bluuebunny/crossref_metadata_2025 huggingface dataset:
Vanadium‐induced apoptosis of HaCaT cells is mediated by c‐fos and involves nuclear accumulation of clusterin
Authors: Markopoulou Soultana , Kontargiris Evangelos , Batsi Christina , Tzavaras Theodore , Trougakos Ioannis , Boothman David A. , Gonos Efstathios S. , Kolettas Evangelos
Published: June 2009

Vanadium exerts a variety of biological effects, including antiproliferative responses through activation of the respective signaling pathways and the generation of reactive oxygen species. As epidermal cells are exposed to environmental insults, human keratinocytes (HaCaT) were used to investigate the mechanism of the antiproliferative effects of vanadyl(IV) sulfate (VOSO4). Treatment of HaCaT cells with VOSO4 inhibited proliferation and induced apoptosis in a dose‐dependent manner. Inhibition of proliferation was associated with downregulation of cyclins D1 and E, E2F1, and the cyclin‐dependent kinase inhibitors p21Cip1/Waf1 and p27Kip1. Induction of apoptosis correlated with upregulation of the c‐fos oncoprotein, changes in the expression of clusterin (CLU), an altered ratio of antiapoptotic to proapoptotic Bcl‐2 protein family members, and poly(ADP‐ribose) polymerase‐1 cleavage. Forced overexpression of c‐fos induced apoptosis in HaCaT cells that correlated with secretory CLU downregulation and upregulation of nuclear CLU (nCLU), a pro‐death protein. Overexpression of Bcl‐2 protected HaCaT cells from vanadium‐induced apoptosis, whereas secretory CLU overexpression offered no cytoprotection. In contrast, nCLU sensitized HaCaT cells to apoptosis. Our data suggest that vanadium‐mediated apoptosis was promoted by c‐fos, leading to alterations in CLU isoform processing and induction of the pro‐death nCLU protein.
Structural characterization of l‐glutamate oxidase from Streptomyces sp. X‐119‐6
Authors: Arima Jiro , Sasaki Chiduko , Sakaguchi Chika , Mizuno Hiroshi , Tamura Takashi , Kashima Akiko , Kusakabe Hitoshi , Sugio Shigetoshi , Inagaki Kenji
Published: June 2009

l‐Glutamate oxidase (LGOX) from Streptomyces sp. X‐119‐6, which catalyzes the oxidative deamination of l‐glutamate, has attracted increasing attention as a component of amperometric l‐glutamate sensors used in the food industry and clinical biochemistry. The precursor of LGOX, which has a homodimeric structure, is less active than the mature enzyme with an α2β2γ2 structure; enzymatic proteolysis of the precursor forms the stable mature enzyme. We solved the crystal structure of mature LGOX using molecular replacement with a structurally homologous model of l‐amino acid oxidase (LAAO) from snake venom: LGOX has a deeply buried active site and two entrances from the surface of the protein into the active site. Comparison of the LGOX structure with that of LAAO revealed that LGOX has three regions that are absent from the LAAO structure, one of which is involved in the formation of the entrance. Furthermore, the arrangement of the residues composing the active site differs between LGOX and LAAO, and the active site of LGOX is narrower than that of LAAO. Results of the comparative analyses described herein raise the possibility that such a unique structure of LGOX is associated with its substrate specificity.

Structured digital abstract

MINT‐7041556: LGOX_gamma fragment (uniprotkb:Q8L3C7), LGOX_beta fragment (uniprotkb:Q8L3C7) and LGOX_alpha fragment (uniprotkb:Q8L3C7) physically interact (MI:0915) by x‐ray crystallography (MI:0114)
Malignant transformation of a chronic leg ulcer
Authors: Erfurt‐Berge Cornelia , Schuler Gerold , Bauerschmitz Juergen
Published: June 2009

We report a case of a squamous cell carcinoma arising from a chronic leg ulcer initially diagnosed as venous ulcer. Usually, further diagnostic assessment of chronic ulcers is initiated with considerable delay only in cases when appropriate treatment fails to effect cure.
Seed Dispersal by Golden‐headed Lion TamarinsLeontopithecus chrysomelasin Southern Bahian Atlantic Forest, Brazil
Authors: Catenacci Lilian S. , De Vleeschouwer Kristel M. , Nogueira‐Filho Sérgio L. G.
Published: June 2009

Seed dispersal by small primates may be particularly relevant in areas where populations of larger frugivores have been reduced or extinguished by hunting and/or habitat disturbance. In this context, the aim of this study was to evaluate the role of the golden‐headed lion tamarinLeontopithecus chrysomelasas a seed disperser in Atlantic forest remnants in Brazil. To this end, we opportunistically collected feces deposited during observations on the feeding behavior of two groups of golden‐headed lion tamarins ranging in the degraded areas of the Una Biological Reserve, Bahia, Brazil, from February 2006 to January 2007. We collected 587 fecal samples, of which 524 contained seeds from 24 plant species, distributed over 13 families. Disregarding seeds of<3 mm, the majority of seeds recovered were bromeliad seeds. In general, ingestion of seeds by golden‐headed lion tamarins did not improve the germination proportion or decrease the germination delay of seeds, with the exception ofAechmeaspp. seeds. The tamarins encountered different habitats during their daily activity period, while feeding and defecating. Consequently, some seeds were transported to different habitats including disturbed areas. Thus, the role of seed dispersal in combination with the daily movement pattern ofL. chrysomelascontributes to the persistence of fruit plants and epiphyte species and to the natural regeneration process within Atlantic forest remnants.
Neither Biased Sex Ratio nor Spatial Segregation of the Sexes in the Subtropical Dioecious Tree Eurycorymbus cavaleriei (Sapindaceae)
Authors: Gao Puxin , Kang Ming , Wang Jing , Ye Qigang , Huang Hongwen
Published: June 2009

Knowledge of sex ratio and spatial distribution of males and females of dioecious species is both of evolutionary interest and of crucial importance for biological conservation. Eurycorymbus cavaleriei, the only species in the genus Eurycorymbus (Sapindaceae), is a dioecious tree endemic to subtropical montane forest in South China. Sex ratios were investigated in 15 natural populations for the two defined ages (young and old). Spatial distribution of males and females was further studied in six large populations occurring in different habitats (fragmented and continuous). The study revealed a slight trend of male‐biased sex ratio in both ages of E. cavaleriei, but sex ratio of most populations (13 out of 15) did not display statistically significant deviation from equality. All of the four significantly male‐biased populations in the young class shifted to equality or even female‐biased. The Ripley's K analysis of the distribution of males with respect to females suggested that individuals of the opposite sexes were more randomly distributed rather than spatially structured. These results suggest that the male‐biased sex ratio in E. cavaleriei may result from the precocity of males and habitat heterogeneity. The sex ratio and the sex spatial distribution pattern are unlikely to constitute a serious threat to the survival of the species.
A New Acylated Anthocyanin from the Red Flowers of Camellia hongkongensis and Characterization of Anthocyanins in the Section Camellia Species
Authors: Li Jian‐Bin , Hashimoto Fumio , Shimizu Keiichi , Sakata Yusuke
Published: June 2009

Twelve anthocyanins (1–12) were isolated from the red flowers of Camellia hongkongensis Seem. by chromatography using open columns. Their structures were elucidated on the basis of spectroscopic analyses, that is, proton‐nuclear magnetic resonance, carbon 13‐nuclear magnetic resonance, heteronuclear multiple quantum correlation, heteronuclear multiple bond correlation, high resolution electrospray ionization mass and ultraviolet visible spectroscopies. Out of these anthocyanins, a novel acylated anthocyanin, cyanidin 3‐O‐(6‐O‐(Z)‐p‐coumaroyl)‐β‐galactopyranoside (6), two known acylated anthocyanins, cyanidin 3‐O‐(6‐O‐(E)‐p‐coumaroyl)‐β‐galactopyranoside (7) and cyanidin 3‐O‐(6‐O‐(E)‐caffeoyl)‐β‐galactopyranoside (8), and three known delphinidin glycosides (10–12) were for the first time isolated from the genus Camellia. Furthermore, pigment components in C. japonica L., C. chekiangoleosa Hu and C. semiserrata Chi were studied. The results indicated that the distribution of anthocyanins was differed among these species. Delphinidin glycoside was only detected in the flowers of C. hongkongensis, which is a special and important species in the section Camellia. Based on the characterization of anthocyanins in the section Camellia species, there is a close relationship among these species, and C. hongkongensis might be an important parent for creating new cultivars with bluish flower color.
RESPONSE SURFACE METHODOLOGY FOR STUDYING THE QUALITY CHARACTERISTICS OF COWPEA (VIGNA UNGUICULATA)‐BASED TEMPEH
Authors: ANNOR GEORGE AMPONSAH , SAKYI‐DAWSON ESTHER , SAALIA FIRIBU K. , SEFA‐DEDEH SAMUEL , AFOAKWA EMMANUEL OHENE , TANO‐DEBRAH KWAKU , BUDU AGNES SIMPSON
Published: June 2009

Response surface methodology was used to optimize the processing conditions in the preparation of cowpea tempeh. The independent factors studied were boiling time (varying from 5 to 30 min), incubation time (varying from 12 to 48 h) and incubation temperatures (varying from 25 to 50C), whereas the dependent factors were protein content, protein solubility, pH, titratable acidity and total color difference (using L, a* and b*). Regression models were generated and adequacy was tested with regression coefficients (R2) and the lack‐of‐fit tests. Optimum processing conditions were determined by method of superimposition. There was a strong and significant influence (P < 0.01) of the quadratic effect of the incubation time on the protein content of the cowpea tempeh, with similar significance (P < 0.01) noted in protein solubility with increasing boiling time. The optimum processing conditions observed for the preparation of cowpea tempeh were boiling time of about 20 min, incubation time of about 28 h and incubation temperature of about 37C.

PRACTICAL APPLICATIONS

Response surface methodology (RSM), as a statistical tool, has been effectively used in food process applications. This study embraced the use of RSM in the optimization of the processing conditions involved in the preparation of cowpea tempeh. Superimposition of the contour plots developed from the regression models indicated that cowpea with optimum quality characteristics should be processed at a boiling time of 20 min, incubation time of 28 h and incubation temperature of 37C. These conditions could be adopted for the industrial production of cowpea tempeh.
OHMIC BLANCHING EFFECTS ON DRYING OF VEGETABLE BYPRODUCT
Authors: ICIER FILIZ
Published: June 2009

Ohmic blanching could be used as an alternative fast blanching method in vegetable processing. Artichoke is a vegetable that is a good source of natural antioxidants. In this study, artichoke byproduct was pretreated with ohmic blanching (25 and 40 V/cm at 85C) and water blanching (at 85 and 100C). The ohmic blanching (40 V/cm) at 85C was able to show similar peroxidase inactivation times (310 ± 2 s) with the water blanching at 100C (300 ± 2 s). The retention of vitamin C and the total phenolic content was found to be highest in the byproduct blanched ohmically by 40 V/cm voltage gradient at 85C. Blanched artichoke byproducts were then dried in the fluid‐bed drier. The drying process was optimized by using response surface methodology. Optimum drying parameters were obtained as 80C, 0.8 m/s and the pretreatment of ohmic blanching at 40 V/cm voltage gradient.

PRACTICAL APPLICATIONS

Residues can form up to 60–65% of the harvested vegetable material in the industries. These residues are very perishable products that are difficult to manage because of environmental problems. Vegetable byproducts have valuable components and should be used in the preparation of functional foods. One of these is artichoke byproducts having high amounts of phenolic substances. The use of artichoke byproduct extracts have been reported in the application of functionalization of soups and bakery products.

Main processes in the treatment of artichoke and its byproduct are blanching and drying. There is no study ever done that explains theoptimization of drying of artichoke products in open literature, according to the author's knowledge. Ohmic heating is a fast and homogeneous electrical heating method inactivating enzymes faster than conventional methods in addition to preserving valuable compounds. It could also enhance the drying performance of vegetable products. The results of this study give information about the drying conditions of artichoke byproducts and the use of ohmic blanching in industrial vegetable processing.
EFFECT OF AIRFLOW REVERSAL ON PACKED‐BED DRYING OF CARROTS
Authors: HERMAN‐LARA E. , MARTÍNEZ‐SÁNCHEZ C.E. , AMADOR‐MENDOZA A. , RUIZ‐LÓPEZ I.I.
Published: June 2009

The effect of the periodical application of airflow reversals on drying rate has been investigated during the packed‐bed drying of carrots. Drying experiments were obtained from a complete 34 factorial design with air temperature (50, 70 and 90C), air velocity (2, 4 and 6 m/s), combined product thickness/bed height (0.001/0.05, 0.01/0.1 and 0.02/0.15 m/m) and frequency of application of the flow reversal (every 900 and 1800 s, and without reversals) as independent variables. Experimental data were fitted to the first‐order exponential model (FOEM) and the Page's model in order to estimate the drying rate constant. A normal quantile–quantile plot for the residuals demonstrated the inadequacy of the FOEM to describe satisfactorily the moisture evolution data. As expected, increasing air temperature and air velocity causes an increase on the drying rate, while a higher product and bed thickness causes the drying rate to decrease (P > 0.95). The effect of application of the airflow reversals was significant on the drying rate with resulting shorter drying times (P > 0.95). Furthermore, the drying rate was found to increase significantly with increase in the frequency of application of the airflow reversal (P > 0.995).

PRACTICAL APPLICATIONS

Considerable moisture and temperature gradients may develop during batch drying of deep beds due to air saturation, causing the quality loss of the product due to drying stresses and degradation of heat‐sensitive materials. The periodical reversion of airflow direction is a practical and economical way to avoid these phenomena. In this work, the influence of airflow reversal and several drying parameters on the overall drying rate is statistically determined during packed‐bed drying of carrots. Furthermore, the periodical reversion of airflow was demonstrated to reduce (up to 18%) the required time to achieve a given degree of drying, which may lead to decreases in energy consumption.
FLOW PROPERTIES AND TUBE FRICTION FACTOR OF MILK CREAM: INFLUENCE OF TEMPERATURE AND FAT CONTENT
Authors: FLAUZINO RODRIGO DIAZ , GUT JORGE ANDREY WILHELMS , TADINI CARMEN CECILIA , TELIS‐ROMERO JAVIER
Published: June 2009

The rheological behavior of milk cream was studied for different fat contents (0.10 to 0.31) and for a wide temperature range (2 and 87C) using a rotational rheometer. Newtonian behavior was observed, except for fat content between 0.20 and 0.31 and temperature between 2 and 33C, where viscoplastic behavior was remarkable. The rheological parameters (Newtonian viscosity, plastic viscosity and yield stress) and density were well correlated to temperature and fat content. Tube friction factor during flow of cream was experimentally obtained at various flow rates, temperatures and tube diameters (86 ≤ Re ≤ 2.3 × 104, 38 ≤ ReB ≤ 8.8 × 103, 1.1 × 103 ≤ He ≤ 6.7 × 103). The proposed correlations for density and rheological parameters were applied for the prediction of friction factor for laminar and turbulent flow of cream using well‐known equations for Newtonian and viscoplastic flow. The good agreement between experimental and predicted values confirms the reliability of the proposed correlations for describing the flow behavior of cream.

PRACTICAL APPLICATIONS

This paper presents correlations for the calculation of density and rheological parameters (Newtonian viscosity, Bingham plastic viscosity and yield stress) of milk cream as functions of temperature (2–87C) and fat content (0.10–0.31). Because of the large temperature range, the proposed correlations are useful for process design and optimization in dairy processing. An example of practical application is presented in the text, where the correlations were applied for the prediction of friction factor for laminar and turbulent tube flow of cream using well‐known equations for Newtonian and viscoplastic flow, which are summarized in the text. The comparison with experimental data obtained at various flow rates, temperatures and tube diameters showed a good agreement, which confirms the reliability of the proposed correlations.
Lipopeptide vaccines illustrate the potential role of subtype‐crossreactive T cells in the control of highly virulent influenza
Authors: Ng Wy Ching , Gilbertson Brad , Lim Bock , Zeng Weiguang , Jackson David C. , Brown Lorena E.
Published: June 2009

Background  The best form of protection against influenza is high‐titred virus‐neutralizing antibody specific for the challenge strain. However, this is not always possible to achieve by vaccination due to the need for predicting the emerging virus, whether it be a drift variant of existing human endemic influenza type A subtypes or the next pandemic virus, for incorporation into the vaccine. By activating additional arms of the immune system to provide heterosubtypic immunity, that is immunity active against all viruses of type A influenza regardless of subtype or strain, it should be possible to provide significant benefit in situations where appropriate antibody responses are not achieved. Although current inactivated vaccines are unable to induce heterosubtypic CD8+ T cell immunity, we have shown that lipopeptides are particularly efficient in this regard.

Objectives  To examine the role of vaccine‐induced CD8+ T cells in altering the course of disease due to highly virulent H1N1 influenza virus in the mouse model.

Methods  The induction of influenza‐specific CD8+ T cells following intranasal inoculation with lipopeptide vaccine was assessed by intracellular cytokine staining (ICS) and the capacity of these cells to reduce viral loads in the lungs and to protect against death after viral challenge was determined.

Results and conclusions  We show that CD8+ T cells are induced by a single intranasal vaccination with lipopeptide, they remain at substantial levels in the lungs and are efficiently boosted upon challenge with virulent virus to provide late control of pulmonary viral loads. Vaccinated mice are not only protected from death but remain active, indicative of less severe disease despite significant weight loss.
Fractal properties of human heart period variability: physiological and methodological implications
Authors: Tan Can Ozan , Cohen Michael A. , Eckberg Dwain L. , Taylor J. Andrew
Published: June 2009

Fractal frequency scaling of heart period variability is used as a concise index of overall cardiac control. However, no prior study has assessed within‐individual reproducibility of fractal indices of heart period, or reported how the estimated indices respond to autonomic blockade. Therefore, we examined fractal properties of the heart period from ten young, healthy individuals during three separate experimental sessions under control (saline) conditions and twice under combined autonomic blockade (atenolol and atropine sulfate) conditions. Under each condition, R‐R intervals were recorded with the subject in the supine and the 40 deg upright tilt positions during 20 min of controlled breathing in each position. We calculated the fractal scaling exponent using detrended fluctuation analysis and estimated confidence intervals of the scaling exponents for each R‐R interval time series within each individual. In the control condition, upright tilt significantly increased the scaling exponents (from 0.73 ± 0.11 (±s.d., session 1), 0.72 ± 0.10 (session 2) and 0.75 ± 0.13 (session 3) to 0.82 ± 0.12, 0.82 ± 0.11 and 0.84 ± 0.10; Student's pairedt‐test,t= 2.79,P= 0.02;t= 2.80,P= 0.02; andt= 2.07,P= 0.07). However, neither the absolute scaling exponents nor their change in response to upright tilt were reproducible (Lin's concordance coefficient less than 0.9,P> 0.1 for all comparisons). Following autonomic blockade, the scaling exponents were significantly increased (supine: 1.08 ± 0.13 and 1.08 ± 0.14; tilt: 1.07 ± 0.21 and 1.08 ± 0.14) for both experimental sessions (two‐way repeated‐measures ANOVA;F17,1= 40.89,P< 0.001 andF17,1= 42.72,P< 0.001) regardless of position. However, within individuals, the scaling exponents failed to distinguish between control and blockade for half of the subjects in at least one experimental session. Thus, fractal scaling exponents are not reproducible within individuals and do not reliably reflect the autonomic mechanisms responsible for heart period variability. In fact, data from combined blockade suggest that physiological effects of autonomic outflow may mask intrinsic fractal behaviour of the sinoatrial node.
My recollections of Hubel and Wiesel and a brief review of functional circuitry in the visual pathway
Authors: Alonso Jose‐Manuel
Published: June 2009

The first paper of Hubel and Wiesel in The Journal of Physiology in 1959 marked the beginning of an exciting chapter in the history of visual neuroscience. Through a collaboration that lasted 25 years, Hubel and Wiesel described the main response properties of visual cortical neurons, the functional architecture of visual cortex and the role of visual experience in shaping cortical architecture. The work of Hubel and Wiesel transformed the field not only through scientific discovery but also by touching the life and scientific careers of many students. Here, I describe my personal experience as a postdoctoral student with Torsten Wiesel and how this experience influenced my own work.
The third dimension in the primary visual cortex
Authors: Westheimer Gerald
Published: June 2009

Anatomical superposition of the cortical projections from the overlapping visual fields of the two eyes does not make it obvious how the disposition of objects in the third dimension is encoded. Hubel and Wiesel's demonstration that units in the primary visual cortex of the mammal respond preferentially to elongated contours of specific orientation encouraged the inquiry into whether binocular disparity might not similarly be represented as an attribute interdigitated within the orderly progression of position. When this was found to indeed be the case, this entrained a brisk research activity into the disparity of receptive fields of single units in the primary visual cortex and the influence on their response of the three‐dimensional locations of outside world stimuli. That cells’ preferred orientations covered the whole gamut whereas space perception required only horizontal disparity was an apparent paradox that needed resolution. A connection with an observer's stereoscopic performance was made by the discovery that cells in the primate primary visual cortex display good tuning to the disparity in random‐dot stereograms. But a wide gap still remains between the properties of these cortical units and human stereo thresholds in simple target configurations, let alone depth judgments in which perceptual and cognitive factors enter. When the neural circuits in the primary visual cortex that are involved in processing depth are eventually traced in detail they will also need to have properties that allow for the plasticity in learning and experience.
Receptive fields and functional architecture in the retina
Authors: Balasubramanian Vijay , Sterling Peter
Published: June 2009

Functional architecture of the striate cortex is known mostly at the tissue level – how neurons of different function distribute across its depth and surface on a scale of millimetres. But explanations for its design – why it is just so – need to be addressed at the synaptic level, a much finer scale where the basic description is still lacking. Functional architecture of the retina is known from the scale of millimetres down to nanometres, so we have sought explanations for various aspects of its design. Here we review several aspects of the retina's functional architecture and find that all seem governed by a single principle: represent the most information for the least cost in space and energy. Specifically: (i) why are OFF ganglion cells more numerous than ON cells? Because natural scenes contain more negative than positive contrasts, and the retina matches its neural resources to represent them equally well; (ii) why do ganglion cells of a given type overlap their dendrites to achieve 3‐fold coverage? Because this maximizes total information represented by the array – balancing signal‐to‐noise improvement against increased redundancy; (iii) why do ganglion cells form multiple arrays? Because this allows most information to be sent at lower rates, decreasing the space and energy costs for sending a given amount of information. This broad principle, operating at higher levels, probably contributes to the brain's immense computational efficiency.
Effects of ageing and exercise training on eNOS uncoupling in skeletal muscle resistance arterioles
Authors: Sindler Amy L. , Delp Michael D. , Reyes Rafael , Wu Guoyao , Muller‐Delp Judy M.
Published: June 2009

Reduced availability of tetrahydrobiopterin (BH4) contributes to the age‐related decline of nitric oxide (NO)‐mediated vasodilatation of soleus muscle arterioles. Depending on availability of substrate and/or necessary co‐factors, endothelial nitric oxide synthase (eNOS) can generate NO and/or superoxide (O2−). We evaluated the effects of age and chronic exercise on flow‐induced vasodilatation and levels of NO and O2− in soleus muscle arterioles. Young (3 months) and old (22 months) male rats were exercise trained or remained sedentary (SED) for 10 weeks. Flow‐stimulated NO and O2−, as well as BH4 and l‐arginine content, were determined in soleus muscle arterioles. Flow‐induced vasodilatation was assessed under control conditions and during the blockade of O2− and/or hydrogen peroxide. Exercise training enhanced flow‐induced vasodilatation in arterioles from young and old rats. Old age reduced, and exercise training restored, BH4 content and flow‐stimulated NO availability. Flow‐stimulated, eNOS‐derived O2− levels were higher in arterioles from old SED compared to those from young SED rats. Exercise training increased flow‐stimulated eNOS‐derived O2− levels in arterioles from young but not old rats. O2− scavenging with Tempol reduced flow‐induced vasodilatation from all groups except young SED rats. Addition of catalase to Tempol‐treated arterioles eliminated flow‐induced vasodilatation in arterioles from all groups. Catalase reduced flow‐induced vasodilatation from all groups. In Tempol‐treated arterioles, flow‐induced vasodilatation was restored by deferoxamine, an iron chelator. These data indicate that uncoupling of eNOS contributes to the age‐related decline in flow‐induced vasodilatation; however, reactive oxygen species are required for flow‐induced vasodilatation in soleus muscle arterioles from young and old rats.
Properties of glycine receptors underlying synaptic currents in presynaptic axon terminals of rod bipolar cells in the rat retina
Authors: Mørkve Svein Harald , Hartveit Espen
Published: June 2009

The excitability of presynaptic terminals can be controlled by synaptic input that directly targets the terminals. Retinal rod bipolar axon terminals receive presynaptic input from different types of amacrine cells, some of which are glycinergic. Here, we have performed patch‐clamp recordings from rod bipolar axon terminals in rat retinal slices. We used whole‐cell recordings to study glycinergic inhibitory postsynaptic currents (IPSCs) under conditions of adequate local voltage clamp and outside‐out patch recordings to study biophysical and pharmacological properties of the glycine receptors with ultrafast application. Glycinergic IPSCs, recorded in both intact cells and isolated terminals, were strychnine sensitive and displayed fast kinetics with a double‐exponential decay. Ultrafast application of brief (∼1 ms) pulses of glycine (3 mm) to patches evoked responses with fast, double‐exponential deactivation kinetics, no evidence of desensitization in double‐pulse experiments, relatively low apparent affinity (EC50∼100 μm), and high maximum open probability (∼0.9). Longer pulses evoked slow, double‐exponential desensitization and double‐pulse experiments indicated slow, double‐exponential recovery from desensitization. Non‐stationary noise analysis of IPSCs and patch responses yielded single‐channel conductances of ∼41 pS and ∼64 pS, respectively. Directly observed single‐channel gating occurred at ∼40–50 pS and ∼80–90 pS in both types of responses, suggesting a mixture of heteromeric and homomeric receptors. Synaptic release of glycine leads to transient receptor activation, with about eight receptors available to bind transmitter after release of a single vesicle. With a low intracellular chloride concentration, this leads to either hyperpolarizing or shunting inhibition that will counteract passive and regenerative depolarization and depolarization‐evoked transmitter release.
Regulatory role of tyrosine phosphorylation in the swelling‐activated chloride current in isolated rabbit articular chondrocytes
Authors: Okumura Noriaki , Imai Shinji , Toyoda Futoshi , Isoya Eiji , Kumagai Kousuke , Matsuura Hiroshi , Matsusue Yoshitaka
Published: June 2009

Articular chondrocytes are exposed in vivo to the continually changing osmotic environment and thus require volume regulatory mechanisms. The present study was designed to investigate (i) the functional role of the swelling‐activated Cl− current (ICl,swell) in the regulatory volume decrease (RVD) and (ii) the regulatory role of tyrosine phosphorylation in ICl,swell, in isolated rabbit articular chondrocytes. Whole‐cell membrane currents were recorded from chondrocytes in isosmotic, hyposmotic and hyperosmotic external solutions under conditions where Na+, K+ and Ca2+ currents were minimized. The cell surface area was also measured using microscope images from a separate set of chondrocytes and was used as an index of cell volume. The isolated chondrocytes exhibited a RVD during sustained exposure to hyposmotic solution, which was mostly inhibited by the ICl,swell blocker 4‐(2‐butyl‐6,7‐dichloro‐2‐cyclopentyl‐indan‐1‐on‐5‐yl)oxobutyric acid (DCPIB) at 20 μm. Exposure to a hyposmotic solution activated ICl,swell, which was also largely inhibited by 20 μm DCPIB. ICl,swell in rabbit articular chondrocytes had a relative taurine permeability (Ptau/PCl) of 0.21. Activation of ICl,swell was significantly reduced by the protein tyrosine kinase (PTK) inhibitor genistein (30 μm) but was only weakly affected by its inactive analogue daidzein (30 μm). Intracellular application of protein tyrosine phosphatase (PTP) inhibitor sodium orthovanadate (250 and 500 μm) resulted in a gradual activation of a Cl− current even in isosmotic solutions. This Cl− current was almost completely inhibited by 4,4′‐diisothiocyanatostilbene‐2,2′‐disulfonate (DIDS, 500 μm) and was also largely suppressed by exposure to hyperosmotic solution, thus indicating a close similarity to ICl,swell. Pretreatment of chondrocytes with genistein significantly prevented the activation of the Cl− current by sodium orthovanadate, suggesting that the basal activity of endogenous PTK is required for the activation of this Cl− current. Our results provide evidence to indicate that activation of ICl,swell is involved in RVD in isolated rabbit articular chondrocytes and is facilitated by tyrosine phosphorylation.
A Finite Element Model for Macroscopic Deformation of the Lung
Authors: Vawter D. L.
Published: June 2009

A finite element model is formulated for determining the macroscopic stress, strain and deformation of the lung parenchyma. The effects of nonlinear elastic behavior, finite deformation, and interfacial tension are included. An incremental approach is used. Illustrative results for deformation of the lung due to its weight are included. The necessity of including surface tension explicitly is demonstrated.
Shock Waves in Fluid-Filled Distensible Tubes
Authors: Rudinger G.
Published: June 2009

Flow of a liquid through distensible tubes is of interest primarily in biological systems, and some properties of shock waves in such tubes are discussed. In shock-fixed coordinates, these flows are steady, and the shock is associated with an increase of pressure and cross-sectional area. Shock transition is analyzed for two flow models, namely, immediate flow separation, when the flow enters the shock zone, and no separation. Shock properties are expressed in terms of the speed index (ratio of the velocity of the shock to that of a small-amplitude wave) and dissipation (loss of total pressure). Examples are worked out for the thoracic aorta of an anesthetized dog, a perfectly elastic tube, and a partially collapsed tube. Appreciable differences in shock velocity and dissipation result if either flow separation or no separation is assumed.
Human Joint Performance and the Roughness of Articular Cartilage
Authors: Thomas T. R. , Sayles R. S. , Haslock I.
Published: June 2009

It is known that the surface of articular cartilage is rough and it has been suggested that this is likely to affect the lubrication of human joints. This paper describes the direct measurement of a cartilage surface with a stylus instrument. It is found that the height distribution is Gaussian with an inverse-square power spectrum. It is thus possible to calculate the elastic deflection of the surface under normal walking loads and it is shown that the mean separation of the cartilage surfaces in a human joint varies rather slowly with load. In one particular hip joint at heel strike the real area of contact was calculated to be about 1.3 cm2, the mean gap to be about 60 μm and the trapped volume to be about 80 percent of that when standing.
Shear-Induced Augmentation of Oxygen Transfer in Blood
Authors: Diller T. E. , Mikic B. B. , Drinker P. A.
Published: June 2009

An experimental study was performed to determine the extent of shear-induced augmentation of oxygen diffusion in blood. The results were obtained using whole human blood in laminar flow through semipermeable membrane tubes. Transfer enchancement in whole blood was found to be dependent on the fluid shear rate and the hemoglobin saturation level. Very little agumentation was observed in saturated blood for shear rates up to 2500 s−1. However, with partially unsaturated blood, oxygen transfer was increased up to 250 percent at the higher shear rates. The implications for modeling oxygen transfer in blood are discussed.
Effects of Transmural Pressure and Muscular Activity on Pulse Waves in Arteries
Authors: Rachev A. I.
Published: June 2009

Propagation of small amplitude harmonic waves through a viscous incompressible fluid contained in an initially stressed elastic cylindrical tube is considered as a model of the pulse wave propagation in arteries. The nonlinearity and orthotropy of the vascular material is taken into account. Muscular activity is introduced by means of an “active” tension in circumferential direction of the vessel. The frequency equation is obtained and it is solved numerically for the parameters of a human abdominal aorta. Conclusions concerning pressure-dependence, age-dependence, and muscular activation-dependence of the wave characteristics are drawn which are in accord with available experimental data.
Automatic Control of Human Thermal Comfort by a Liquid-Cooled Garment
Authors: Kuznetz L. H.
Published: June 2009

Astronauts utilize water cooling in a liquid-cooled garment to maintain thermal comfort during extravehicular activities (EVA’s). In the Apollo and Skylab Programs, manual control of the cooling water was a necessary operation to ensure proper control of body heat storage for the EVA crewman. The development of an automatic thermal control system would be a valuable asset to the conduct of EVA, relieving the crewman of a task that can interfere with his EVA objectives. An analytical model of human thermoregulation was used to develop the equations governing the operation of such an automatic controller. A series of tests verified the feasibiliy of a controller utilizing only a measurement of the difference in coolant temperature into and out of the astronaut’s liquid-cooled garment and an estimate of environmental heat loss to maintain the proper crewman thermal balance. Three test subjects performed over a wide range of metabolic rates, and the crewman heat balance was maintained well within allowable medical limits. This study demonstrates the use of a mathematical model to generate previously unknown physiological relationships between human thermal comfort and liquid cooled garment performance. In so doing, it quantitates physiological parameters that are difficult to relate directly by experiment. Index terms: body temperature regulation, space suit cooling, temperature control, human thermoregulation.
Quasi-Linear Viscoelastic Properties of Normal Articular Cartilage
Authors: Woo S. L.-Y. , Simon B. R. , Kuei S. C. , Akeson W. H.
Published: June 2009

A combined experimental and analytical approach was used to determine the history-dependent viscoelastic properties of normal articular cartilage in tension. Specimens along the surface split line direction, taken from the middle zone of articular cartilage were subjected to relaxation and cyclic tests. A quasi-linear viscoelastic theory proposed by Fung [31] was used in combination with the experimental results to determine the nonlinear viscoelastic properties and the elastic stress-strain relationship of normal articular cartilage.
Volumetric Changes in Cells During Freezing and Thawing
Authors: Knox J. M. , Schwartz G. S. , Diller K. R.
Published: June 2009

A thermodynamic model is presented to describe the combined freezing and thawing process for living cells. Continuous changes in the cell volume are predicted according to the thermal protocol imposed on the system. Experimental verification of the model is sought by monitoring continuously the volume of cells as frozen on a cryomicroscope. The volumes of individual cells are measured from sequential photomicrographs by a computerized image analysis technique. The model and experimental data are in quite close agreement for the freezing process, but upon thawing the experimentally measured volumes consistently increased much more rapidly than predicted by the model. The model can be made to conform to the data by accounting for a substantial influx of electrolyte to the cell at subfreezing temperatures.
Mechanical Properties of the Canine Aorta Following Hypercholesterolemia
Authors: Haut R. C. , Garg B. D. , Metke M. , Josa M. , Kaye M. P.
Published: June 2009

The effect of hypercholesterolemia on the transverse wall properties of the upper descending thoracic aorta was studied in canines. Hypothyroid animals were fed a free diet supplemented with cholesterol, propylthiouracil, and saturated fat (lard) for 11 mo. The mechanical properties of the wall showed marked changes following experimental pathology. The failure stress, failure elongation, and energy to failure decreased following hypercholesterolemia. The tensile response was bilinear in both the pathological and control tissues. In the initial region, which is controlled by elastic fibers, the response was left unchanged by the experimental pathology. In the secondary region, which is controlled by stretching of the collagen fibers, the intercept with the strain axis and the slope were decreased by the pathology. This indicates that there are changes in the strength-bearing collagen and its interaction with the amorphous matrix. However, no significant parallel histological changes were observed in the structure of collagen and elastic fibers. Although this phenomenon precedes the development of atherosclerotic plaques which are charateristic of a diagnosed human disease, the aortic wall is already “hardened” because of its reduced compliance resulting from the shift in the onset of secondary (collagenous) response.
The Contribution of the Cruciate Ligaments to the Load-Displacement Characteristics of the Human Knee Joint
Authors: Piziali R. L. , Rastegar J. , Nagel D. A. , Schurman D. J.
Published: June 2009

Human knee specimens were subjected to anterior-posterior, medial-lateral, varus-valgus, and torsional displacement tests. Loads were recorded for the intact joint and for the joint with all soft tissues cut except for the cruciate ligaments. The effect of condylar interference was determined for anterior-posterior, medial-lateral, and torsional displacements. The variation in load with flexion angle was considerable for medial-lateral (0–90-deg flexion) displacements, and less for varus-valgus (0–45-deg flexion) displacements. The cruciates were found to carry almost the entire anterior-posterior load; they carried a significant percentage of the medial-lateral load which varied considerably with flexion angle. A small, but not insignificant percentage of the varus-valgus load was carried by the cruciates and the variations with flexion angle were small. In torsion, the cruciates resisted only internal rotation. In the tested displacement ranges, condylar interference had a small effect on the medial-lateral load but did not affect anterior-posterior or torsional loads.
Devolution of Inhomogeneities in Bone Structure—Predictions of Adaptive Elasticity Theory
Authors: Firoozbakhsh K. , Cowin S. C.
Published: June 2009

In this paper we consider an initially inhomogeneous adaptive elastic body subjected to a steady homogeneous stress state. The adaptive elastic body, which is a model for living bone tissue, is inhomogeneous in both its anisotropic elastic properties and its density. The principal result of the paper is the determination of the devolution of the initially inhomogeneous body to a homogeneous body under the influence of the steady homogeneous stress state. A cylindrical body that is inhomogeneous along the axis of the cylinder, but homogeneous in each transverse plane of the cylinder, is used as an example. This cylindrical body is loaded by a steady uniform stress directed along the cylindrical axis. The temporal devolution of an inhomogeneity in the initial shape of a sine wave is illustrated. As time progresses the amplitude of the sine wave decreases, rapidly at first and then more slowly. As time becomes very large the sine wave becomes a straight line signifying that the cylinder has become homogeneous.
Large Deformation Analysis of Some Soft Biological Tissues
Authors: Demiray H.
Published: June 2009

Due to physiological structure of most of the soft biological tissues, measurable stresses develop after the specimen has been stretched to many hundreds of percent of its relaxed length. Therefore, the nonlinear stress-strain relations developed for vulcanized rubber cannot be applied to soft tissues, which are constitutionally much more nonlinear than other engineering materials. In this article, using two different elastic models proposed for elastic soft tissues, simple elongation of a cylindrical bar and the inflation of a spherical thick shell, which is deemed to be a model for a left venticle, are studied and the material coefficients characterizing the elastic model are obtained via comparing theoretical results with existing experiments on tissues. Furthermore, the elastic stiffnesses which are very important for physiologists and cardiologists are discussed and the consistency of the result with experiments are indicated.
ASME Centennial Historical Perspective Paper: The Lung—A Perspective of Biomechanics Development
Authors: Fung Y. C.
Published: June 2009

This article discusses the flow of gas, blood, and water in the lung from the point of view of the development of biomechanics. History is reviewed in order to gain a perspective of the present and the future.
Why Sliding Seats and Short Stroke Intervals are Used for Racing Shells
Authors: Senator M.
Published: June 2009

A theory is developed to explain why racing shell crews use sliding seats and shorter-than-necessary stroke intervals, two features that tend to waste energy in a highly competitive, power-limited situation. The theory shows that sliding seats are used because they allow the crew to move the oar blades fast enough during the stroke to transfer all available power to the water. Shorter-than-necessary stroke intervals are used to minimize the sum of the power dissipated in developing thrust, which decreases with the relative length of the stroke interval, and the power dissipated in hull drag due to fluctuations about average velocity, which increases with the relative length of the stroke interval. Using representative dimensions and masses, a typical value of average velocity for a race, and independently estimated values of drag and thrust coefficients, the theory predicts an optimum stroke fraction of 0.400, an optimum stroke rate of 45 per min, and an accountable power of 0.46 hp/man for an eight-oar racing shell, values that agree remarkably well with those used under competitive racing conditions. The theory indicates that using wider-bladed oars might improve performance; the theory also supports a suggestion made to the writer by R. A. Swanson that crossing the oars over the shell would improve performance.
Vascular Endothelial Morphology as an Indicator of the Pattern of Blood Flow
Authors: Nerem R. M. , Levesque M. J. , Cornhill J. F.
Published: June 2009

A quantitative study of the en face size and shape of endothelial cells from aortic intercostal ostia has been carried out in rabbits. Photomicrographs were taken from vascular casts of the rabbit aorta and the endothelial cell outlines were analyzed quantitatively using a digitizer and digital computer. The morphology of the endothelial cells was described using 8 calculated parameters (area, perimeter, length, width, angle of orientation, width: length ratio, axis-intersection ratio and shape index). Marked changes in cell morphology were found in the regions proximal and distal to ostia as well as around flow dividers. Cells on the aorta are aligned with the flow direction, and the endothelial cells within the ostia have an angle of orientation of approximately 45 deg to the axis of the vessel. The results obtained to date suggest that endothelial cell morphology and orientation around a branch vessel may be a natural marker or indicator of the detailed features of blood flow.
Effects of Subject Position on Balance Platform Measurements
Authors: Harris G. F. , Salamon N. J. , Weber R. C.
Published: June 2009

The high cost of commercially available force plates instrumented to quantify postural sway can be prohibitive to both research and clinical institutions. Therefore custom plate design and construction within the institutional environment is not uncommon. Some plate designs, however, may give erroneous measurements depending upon subject position. We report here on the existence of a kern boundary on the plate surface. Loads placed inside this boundary result in support compression, while those placed outside cause at least one support to experience tension. The findings indicate that the type of force transducer used for corner support (unidirectional or bidirectional), the type of connection between the plate and transducers, plate weight, subject weight, plate dimensions and transducer preloads are all critical to accurate measurements.
An Analytical Model of Pauwels’ Functional Adaptation Mechanism in Bone
Authors: Firoozbakhsh K. , Cowin S. C.
Published: June 2009

In this paper it is argued and partially demonstrated that the features of Pauwels’ qualitative theory of functional adaptation of bone tissue are expressed mathematically by the cubic approximation to the theory of internal remodeling presented by Cowin and Hegedus. Complete solutions for the steady stress and steady strain situations in the cubic approximation to the theory of internal remodeling are presented. The cubic remodeling rate equation is shown to correspond closely to the remodeling equation suggested by Kummer for the qualitative theory of Pauwels.