bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydroacoustic events located near the Atlantis (30N) and Kane (2330N) transform faults on the MAR
Authors: Williams Clare M. , Stephen Ralph A. , Smith Deborah K.
Published: February 2004

Hydroacoustic arrivals detected by a hydrophone array on the Northern Mid-Atlantic Ridge (MAR) are used to better understand T phases from oceanic crust earthquakes. T-phase events are selected from two study areas: the inside corner and ridge transform intersection at the eastern ends of the Kane (2330N) and Atlantis (30N) transform faults. Both are regions of high relief (5000 m) and events are located throughout the massif and transform valleys. We investigate the spatial distribution of T-phase locations as a function of water depth. We examine the characteristics of T phases as a function of both distance from the event to each hydrophone and event location water depth. Finally, we use a ray-trace model to test for bathymetric blockage along the propagation path of the T phase. We observe that acoustic magnitudes of T phases show no dependence on water depth of event location. This is opposite to predictions from current T-phase generation models which show water depth dependence. There may be a correlation between acoustic magnitude and propagation path topography, but results are sensitive to the sound velocity profile used in the model. Our results underscore the complexity of T-phase generation and propagation.
A Genome-Wide Screen Identifies Genes Required for Centromeric Cohesion
Authors: Marston Adele L. , Tham Wai-Hong , Shah Hiral , Amon Angelika
Published: February 2004

During meiosis, two chromosome segregation phases follow a single round of DNA replication. We identified factors required to establish this specialized cell cycle by examining meiotic chromosome segregation in a collection of yeast strains lacking all nonessential genes. This analysis revealed Sgo1, Chl4, and Iml3 to be important for retaining centromeric cohesin until the onset of anaphase II. Consistent with this role, Sgo1 localizes to centromeric regions but dissociates at the onset of anaphase II. The screen described here provides a comprehensive analysis of the genes required for the meiotic cell cycle and identifies three factors important for the stepwise loss of sister chromatid cohesion.
Child safety education and the world wide web: an evaluation of the content and quality of online resources: Table 1
Authors: Isaac D , Cusimano M D , Sherman A , Chipman M
Published: February 2004

The purpose of this study was to assess the content, quality, and type of internet resources available for safety education. Using 19 search engines with search strings targeting major forms of injury, identified resources were classified by audience group, accessibility, and authorship. Two independent reviewers rated each resource on the basis of its content and a set of quality criteria using a three point scale. Overall, 10 (18.2%) resources were of highest quality, four (7.3%) were intermediate, and 41 (74.5%) were not recommended. Eighteen months after the original search, 67.3% of all resources and 90% of the highest quality resources were still on the internet. This study provides a methodology for evaluating child safety resources on the world wide web and demonstrates that most internet resources for safety education are of dubious quality. A rating system such as the one developed for this study may be used to identify valuable internet materials.
CDC’s National Violent Death Reporting System: background and methodology
Authors: Paulozzi L J , Mercy J , Frazier L , Annest J L
Published: February 2004

Objectives:This paper describes a new surveillance system called the National Violent Death Reporting System (NVDRS), initiated by the United States Centers for Disease Control and Prevention. NVDRS’s mission is the collection of detailed, timely information on all violent deaths.

Design:NVDRS is a population based, active surveillance system designed to obtain a complete census of all resident and occurrent violent deaths. Each state collects information on its own deaths from death certificates, medical examiner/coroner files, law enforcement records, and crime laboratories. Deaths occurring in the same incident are linked. Over 270 data elements can be collected on each incident.

Setting:The 13 state health departments of Alaska, Colorado, Georgia, Maryland, Massachusetts, New Jersey, North Carolina, Oklahoma, Oregon, Rhode Island, South Carolina, Virginia, and Wisconsin.

Subjects:Cases consist of violent deaths from suicide, homicide, undetermined intent, legal intervention, and unintentional firearm injury. Information is collected on suspects as well as victims.

Interventions:None.

Outcome measures:The quality of surveillance will be measured in terms of its acceptability, accuracy, sensitivity, timeliness, utility, and cost.

Results:The system has just been started. There are no results as yet.

Conclusions:NVDRS has achieved enough support to begin data collection efforts in selected states. This system will need to overcome the significant barriers to such a large data collection effort. Its success depends on the use of its data to inform and assess violence prevention efforts. If successful, it will open a new chapter in the use of empirical information to guide public policy around violence in the United States.
Do children’s intentions to risk take relate to actual risk taking?
Authors: Morrongiello B A
Published: February 2004

Objectives:Concerns about safety and rigorous ethic standards can make it very difficult to study children’s risk taking. The goal of this study was to determine how closelyintentionsto risk take relate toactualrisk taking among boys and girls 6–11 years of age.

Methods:Children initially completed an “intentions to risk take” task. Following administration of several questionnaires they later participated in an actual risk taking task.

Results:At all ages, for both boys and girls, intentions to risk take was highly positively correlated with actual risk taking. When discrepancies occurred these were usually of minimal magnitude.

Conclusions:Tasks that tap children’s intentions to risk take can serve as proxy indicators of children’s actual risk taking.
Community based programs to prevent poisoning in children 0–15 years: Table 1
Authors: Nixon J , Spinks A , Turner C , McClure R
Published: February 2004

Objective:Community based models for injury prevention have become an accepted part of the overall injury control strategy. This systematic review of the scientific literature examines the evidence for their effectiveness in preventing poisoning in children 0–15 years of age.

Methods:A comprehensive search of the literature was performed using the following study selection criteria: community based intervention study; target population was children under 15 years; outcome measure was poisoning rates; and either a community control or an historical control was used in the study design. Quality assessment and data abstraction were guided by a standardized procedure and performed independently by two authors. Data synthesis was in tabular and text form with meta-analysis not being possible due to the discrepancy in methods and measures between the studies.

Results:The review found only four studies, which met all the inclusion criteria. Only two studies used a trial design with a contemporary control and only one study provided convincing evidence of an effective community program for reducing poisoning in children.

Conclusion:There is a paucity of research studies in the literature from which evidence regarding the effectiveness of community based childhood poisoning prevention programs can be obtained and hence a clear need to increase the effort on developing this evidence base.
How, and when, can I restrain a patient?
Authors: Horsburgh D
Published: February 2004

The need to restrain service users will vary according to the area of practice within which practitioners are employed. Many of the principles that relate to the issue of restraining service users are, however, applicable to all, or most, health and social care settings. While the emphasis should be on pre-emptive action, wherever possible, in order to prevent the need to restrain, there are some occasions on which the risks to the service user, or others, of inaction may outweigh those of taking action. Some of the key issues are discussed in this paper.
Audit on flexible sigmoidoscopy for rectal bleeding in a district general hospital: are we over-loading the resources?
Authors: Mathew J , Shankar P , Aldean I M
Published: February 2004

Objective

Patients with rectal bleeding are being over investigated because of the fear of missing colorectal cancers. This study aimed to identify the percentage of patients <45 years of age who undergo flexible sigmoidoscopy for rectal bleeding, and to assess and compare the incidence of colorectal cancers and polyps above and below this age.

Methods

Patients who underwent flexible sigmoidoscopy for rectal bleeding between 1 January 2000 and 31 December 2002 were reviewed. Patients were divided into two groups: group 1 consisted of patients aged ⩾45 years and group 2 patients <45 years. The histopathology of biopsy specimens taken was also studied.

Results

Altogether 18.9% of the patients who had flexible sigmoidoscopy for rectal bleeding were <45 years. The incidence of colorectal cancers in group 1 was 3.5%; all these cases were confirmed on histopathology. Only one patient in group 2 was diagnosed with colorectal cancer on flexible sigmoidoscopy, but the histopathology disproved it. The incidence of polyps was 16.6% in group 1 and 7.9% in group 2. Following histopathology, the incidence of adenomatous polyps was 6.8% in group 1 and 2.1% in group 2. There was a significant difference between the two groups, with a p value of <0.0001.

Conclusion

The incidence of colorectal cancers and adenomatous polyps in patients aged <45 years with rectal bleeding is very low. A flexible sigmoidoscopy costs approximately £330. If new guidelines are implemented considering the age of the patient, considerable cost savings could be made, and the available resources could be appropriately used in groups with high incidences of colorectal cancers.
ACOUSTIC INSERTION LOSS PROVIDED BY RIGID ACOUSTIC BARRIERS OF DIFFERENT SHAPES
Authors: BRANCO FERNANDO J. F. G. , GODINHO LUÍS , TADEU ANTÓNIO
Published: February 2004

The present article studies what effect the shape of a rigid acoustic barrier has on the acoustic insertion loss provided by the barrier. The Boundary Element Method (BEM), formulated in the frequency domain, is used to evaluate the sound propagation around acoustic screens in the vicinity of a tall building. The acoustic screen is assumed to be non-absorbing, and the building is modeled as an infinite barrier. Signals in the time domain are obtained from the frequency domain computations by applying inverse Fourier transforms. In the examples provided, the height of the acoustic barrier remains constant, but different geometric shapes are modeled. The results obtained for a vertical barrier are used as a reference.
BROADBAND SIGNAL SIMULATION IN SHALLOW WATER
Authors: JENSEN FINN B. , FERLA CARLO M. , NIELSEN PETER L. , MARTINELLI GIOVANNA
Published: February 2004

Today's minimum requirements for ocean acoustic models are to be able to simulate broadband signal transmissions in 2D varying environments with an acceptable computational effort. Standard approaches comprise ray, normal mode and parabolic equation techniques. In this paper we compare the performance of four broadband models [Formula: see text] on a set of shallow-water test environments with propagation out to 10 km and a maximum signal bandwidth of 10–1000 Hz. It is shown that a computationally efficient modal approach as implemented in the [Formula: see text] model is much faster than standard, less optimized models such as [Formula: see text] and [Formula: see text]. However, the handling of range dependency in the adiabatic approximation is not always sufficiently accurate, and it is suggested that a mode coupling approach be adopted in [Formula: see text]. Moreover, the interpolation of modal properties in range could lead to a further significant speed-up of mode calculations in range-dependent environments. It is concluded that coupled modes with wavenumber interpolation in both frequency and range remain the most promising wave modeling approach for broadband signal simulations in range-dependent shallow water environments. At higher frequencies (> 1 kHz) there is currently no alternative to rays as a practical signal simulation tool.
COUPLED-MODE PREDICTION OF BACKSCATTER
Authors: MCDANIEL SUZANNE T.
Published: February 2004

The application of coupled-mode theory to ocean acoustic propagation and scattering requires that ideal boundary conditions be applied at the surface and within the seabed. The depth of the lower boundary imposes limits on the ability of coupled-mode models to treat propagation and scattering at high grazing angles. Selecting this depth to predict the contributions of the continuous spectrum in a range-independent two-layered waveguide is not practical, and other methods must be introduced to apply coupled-mode theory in the near field of a source. An example of up-slope propagation in a range-dependent waveguide in which backscatter is governed by ray steepening and reversal is also treated. With a careful choice of the depth at which the lower boundary condition is applied, an estimate of the backscattered field is obtained.
THE MATCHED FIELD PROCESSING OF BINAURAL DOLPHIN-LIKE SIGNALS FOR THE DETECTION AND IDENTIFICATION OF BURIED TARGETS
Authors: TOLSTOY A. , AU W.
Published: February 2004

The Matched Field Processing (MFP) approach to be discussed here is intended to extract subtle differences between apparently similar signals. The technique is applied coherently to an array of data, i.e. to two receivers. One of the main advantages to this work is that even though we use MFP, there is no modeling involved. Since the available binaural data are quite limited and show very strong, obviously different returns from all the targets (not the subtle differences realistically expected), we found it necessary to manipulate the data to bring them more into line with expectations. In particular, scattered returns from a drum were reduced, i.e. multiplied by a small constant factor, then added to the scattered returns from bottom-only data using various time shifts. The shifts simulated a family of returns from a low signal-to-noise (S/N) 55 gallon drum target. This family with shifted bottom scattering mimics returns from multiple placements of the targets on the bottom. These new target "data" (comprised of manipulated real data) seem at first glance to be nearly identical to the original bottom-only returns. Thus, the new target data display subtle differences from the bottom-only data. The MFP approach (based on the linear, a.k.a., Bartlett, processor) was then applied to these new "data". They were processed and yielded a target "template" of scattered returns varying as a function of time and frequency characterizing the returns scattered from the drum. Additionally, a similar template was computed for the buried manta-like target data and is seen to be quite different from the drum template. This new type of template can easily be used to detect scattering from particular target types in low S/N situations. It is not proposed that dolphins are using these templates, but, rather, that the templates display scattering characteristics which the dolphins may be using. More data would be extremely useful in determining the templates under a variety of conditions, e.g. for lower S/N levels, different bottom types, targets types, source ranges, depths, and scattering angles, etc.
Control of Na+-K+-ATPase β1-subunit expression: role of 3′-untranslated region
Authors: Shao Yvonne , Ismail-Beigi Faramarz
Published: February 2004

Using in vitro translation and cell transfection assays, we previously demonstrated that the Na+-K+-ATPase β1 mRNA species containing its longest 3′-untranslated region (UTR) exhibited the lowest translational efficiency. Here, employing deletions and in vivo expression assays, using direct injection of plasmids into rat ventricular myocardium, we identified a 143-nt segment located in the distal 3′-UTR of β1 mRNA that was associated with decreased luciferase expression; interestingly, this segment contains three AUUUA motifs. Using RNA-protein binding assays and UV cross-linking of cRNA with cytosolic proteins of rat heart, we identified an ∼38-kDa protein that specifically bound to the cRNA encoding the 143-nt segment of β1 mRNA 3′-UTR. Mutation of three nucleotides located in the middle region of the 143-nt segment, which was predicted to greatly disrupt a putative stem-loop structure of the cRNA in this region, was associated with reduced binding of the mutated cRNA to the protein migrating at ∼38 kDa. The cRNA encoding a segment of cyclooxygenase-2 mRNA 3′-UTR containing six AUUUA sequences did not bind the protein migrating at ∼38 kDa and did not compete with the binding of the wild-type 143-nt β1 cRNA to the protein. The above results suggest that the 143-nt segment in the distal segment of the 3′-UTR of β1 mRNA may play an important role in the control of β1-subunit expression.
Differential modulation of voltage-dependent K+ currents in colonic smooth muscle by oxidants
Authors: Prasad Madhu , Goyal Raj K.
Published: February 2004

The effect of oxidants on voltage-dependent K+ currents was examined in mouse colonic smooth muscle cells. Exposure to either chloramine-T (Ch-T), an agent known to oxidize both cysteine and methionine residues, or the colon-specific oxidant monochloramine (NH2Cl) completely suppressed the transient outward K+ current ( Ito) while simultaneously enhancing the sustained delayed rectifier K+ current ( Idr). In contrast, the cysteine-specific oxidants hydrogen peroxide (H2O2) and 5,5′-dithiobis(2-nitrobenzoic acid) (DTNB) exhibited partial and slow suppression of Ito by inducing a shift in channel availability of -18 mV without affecting Idr. After enhancement by NH2Cl or Ch-T, Idr was sensitive to 10 mM tetraethylammonium but not to other K+ channel blockers, suggesting that it represented activation of the resting Idr and not a separate K+ conductance. Extracellular dithiothreitol (DTT) partially reversed the effect of H2O2 and DTNB on Ito but not the actions of NH2Cl and Ch-T on either Idr or Ito. Dialysis of myocytes with GSH (5 mM) or DTT (5 mM) prevented suppression of Ito by H2O2 and DTNB but did not alter the effects of NH2Cl or Ch-T on either Idr or Ito. Ch-T and NH2Cl completely blocked Ito generated by murine Kv4.1, 4.2, and 4.3 in Xenopus oocytes, an effect not reversible by intracellular DTT. In contrast, intracellular DTT reversed the effect of H2O2 and DTNB on the cloned channels. These results suggest that Ito is suppressed via modification of both methionine and cysteine residues, whereas enhancement of Idr likely results from methionine oxidation alone.
A SCL4A10 gene product maps selectively to the basolateral plasma membrane of choroid plexus epithelial cells
Authors: Praetorius J. , Nejsum L. N. , Nielsen S.
Published: February 2004

The choroid plexus epithelium of the brain ventricular system produces the majority of the cerebrospinal fluid and thereby defines the ionic composition of the interstitial fluid in the brain. The transepithelial movement of Na+ and water in the choroid plexus depend on a yet-unidentified basolateral stilbene-sensitive [Formula: see text]-[Formula: see text] uptake protein. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis revealed the expression in the choroid plexus of SLC4A10 mRNA, which encodes a stilbene-sensitive [Formula: see text]-[Formula: see text] transporter. Anti-COOH-terminal antibodies were developed to determine the specific expression and localization of this [Formula: see text]-[Formula: see text] transport protein. Immunoblotting demonstrated antibody binding to a 180-kDa protein band from mouse and rat brain preparations enriched with choroid plexus. The immunoreactive band migrated as a 140-kDa protein after N-deglycosylation, consistent with the predicted molecular size of the SLC4A10 gene product. Bright-field immunohistochemistry and immunoelectron microscopy demonstrated strong labeling confined to the basolateral plasma membrane domain of the choroid plexus epithelium. Furthermore, the stilbene-insensitive [Formula: see text]-[Formula: see text] cotransporter, NBCn1, was also localized to the basolateral plasma membrane domain of the choroid plexus epithelium. Hence, we propose that the SLC4A10 gene product and NBCn1 both function as basolateral [Formula: see text] entry pathways and that the SLC4A10 gene product may be responsible for the stilbene-sensitive [Formula: see text]-[Formula: see text] uptake that is essential for cerebrospinal fluid production.
Extracellular matrix controls myosin light chain phosphorylation and cell contractility through modulation of cell shape and cytoskeletal prestress
Authors: Polte Thomas R. , Eichler Gabriel S. , Wang Ning , Ingber Donald E.
Published: February 2004

The mechanism by which vascular smooth muscle (VSM) cells modulate their contractility in response to structural cues from extracellular matrix remains poorly understood. When pulmonary VSM cells were cultured on increasing densities of immobilized fibronectin (FN), cell spreading, myosin light chain (MLC) phosphorylation, cytoskeletal prestress (isometric tension in the cell before vasoagonist stimulation), and the active contractile response to the vasoconstrictor endothelin-1 all increased in parallel. In contrast, MLC phosphorylation did not increase when suspended cells were allowed to bind FN-coated microbeads (4.5-μm diameter) or cultured on micrometer-sized (30 × 30 μm) FN islands surrounded by nonadhesive regions that support integrin binding but prevent cell spreading. Cell spreading and MLC phosphorylation also both decreased in parallel when the mechanical compliance of flexible FN substrates was raised. MLC phosphorylation was inhibited independently of cell shape when cytoskeletal prestress was dissipated using a myosin ATPase inhibitor in fully spread cells, whereas it increased to maximal levels when microtubules were disrupted using nocodazole in cells adherent to FN but not in suspended cells. These data demonstrate that changes in cell-extracellular matrix (ECM) interactions modulate smooth muscle cell contractility at the level of biochemical signal transduction and suggest that the mechanism underlying this regulation may involve physical interplay between ECM and the cytoskeleton, such that cell spreading and generation of cytoskeletal tension feed back to promote MLC phosphorylation and further increase tension generation.
ATP-dependent regulation of SK4/IK1-like currents in rat submandibular acinar cells: possible role of cAMP-dependent protein kinase
Authors: Hayashi M. , Kunii C. , Takahata T. , Ishikawa T.
Published: February 2004

SK4/IK1 encodes an intermediate conductance, Ca2+-activated K+ channel and fulfills a variety of physiological functions in excitable and nonexcitable cells. Although recent studies have provided evidence for the presence of SK4/IK1 channels in salivary acinar cells, the regulatory mechanisms and the physiological function of the channel remain unknown in these cells. Using molecular and electrophysiological techniques, we examined whether cytosolic ATP-dependent regulation of native SK4/IK1-like channel activity would involve endogenous cAMP-dependent protein kinase (PKA) in rat submandibular acinar (RSA) cells. Electrophysiological properties of tetraethylammonium (TEA) (10 mM)-insensitive, Ca2+-dependent K+ currents in macropatches excised from RSA cells matched those of whole cell currents recorded from human embryonic kidney-293 cells heterologously expressing rat SK4/IK1 (rSK4/IK1) cloned from RSA cells. In outside-out macropatches, activity of native SK4/IK1-like channels, defined as a charybdotoxin (100 nM)-blockable current in the presence of TEA (10 mM) in the bathing solution, ran down unless both ATP and Mg2+ were present in the pipette solution. The nonhydrolyzable ATP analog AMP-PNP failed to support the channel activity as ATP did. The addition of Rp-cAMPS (10 μM), a PKA inhibitor, to the pipette solution containing ATP/Mg2+ induced a rundown of the Ca2+-dependent K+ currents. Inclusion of cAMP (1 mM) into the pipette solution (1 μM free Ca2+) containing ATP/Mg2+ caused a gradual increase in the currents, the effect being pronounced for the currents induced by 0.1 μM free Ca2+. Forskolin (1 μM), an adenylyl cyclase activator, also increased the currents induced by 0.1 μM free Ca2+. In inside-out macropatches, cytosolic ATP/Mg2+ increased both the maximum current (proportional to the maximum channel activity) and Ca2+ sensitivity of current activation. Collectively, these results suggest that ATP-dependent regulation of native SK4/IK1-like channels, at least in part, is mediated by endogenous PKA in RSA cells.
Mechanism of regulation of the gap junction protein connexin 43 by protein kinase C-mediated phosphorylation
Authors: Bao Xiaoyong , Altenberg Guillermo A. , Reuss Luis
Published: February 2004

Phosphorylation of the gap junction protein connexin 43 (Cx43) by protein kinase C (PKC) decreases dye coupling in many cell types. We report an investigation of the regulation by PKC of Cx43 gap junctional hemichannels (GJH) expressed in Xenopus laevis oocytes. The activity of GJH was assessed from the uptake of hydrophilic fluorescent probes. PKC inhibitors increased probe uptake in isolated oocytes expressing recombinant Cx43, indicating that the regulatory effect occurs at the hemichannel level. We identified by mutational analysis the carboxy-terminal (CT) domain sequences involved in this response. We found that 1) Ser368 is responsible for the regulation of Cx43 GJH solute permeability by PKC-mediated phosphorylation, 2) CT domain residues 253-270 and 288-359 are not necessary for the effect of PKC, and 3) the prolinerich CT region is not involved in the effect of phosphorylation by PKC. Our results demonstrate that Ser368 (but not Ser372) is involved in the regulation of Cx43 solute permeability by PKC-mediated phosphorylation, and we conclude that different molecular mechanisms underlie the regulation of Cx43 by intracellular pH and PKC-mediated phosphorylation.
Cytoskeletal disruption and small heat shock protein translocation immediately after lengthening contractions
Authors: Koh Timothy J. , Escobedo Joel
Published: February 2004

The purposes of this study were to determine whether, immediately after lengthening contractions, 1) levels of specific force-transmitting cytoskeletal elements are reduced in skeletal muscle cells and 2) cytosolic small heat shock proteins (HSPs) translocate to structures prone to disruption. Western blot analysis demonstrated decreased concentrations of z-disk proteins α-actinin and plectin and membrane scaffolding proteins dystrophin and β-spectrin in muscle exposed to lengthening contractions compared with contralateral control muscle. Lengthening contractions also resulted in immediate translocation of constitutively expressed HSP25 and αB-crystallin from the soluble to the insoluble fraction of muscle homogenates, and cryosections showed translocation from a diffuse, cytosolic localization to striations that corresponded to z-disks. Lengthening contraction-induced translocation of HSP25 and αB-crystallin was associated with phosphorylation of these small HSPs, which may trigger their protective activity. In summary, these findings demonstrate loss of z-disk and membrane scaffolding proteins immediately after lengthening contractions, and concomitant translocation of HSP25 and αB-crystallin to the z-disk, which may help to stabilize or repair cytoskeletal elements at this site.
Regulation of exocytosis by purinergic receptors in pancreatic duct epithelial cells
Authors: Jung Seung-Ryoung , Kim Mean-Hwan , Hille Bertil , Nguyen Toan D. , Koh Duk-Su
Published: February 2004

In epithelial cells, several intracellular signals regulate the secretion of large molecules such as mucin via exocytosis and the transport of ions through channels and transporters. Using carbon fiber amperometry, we previously reported that exocytosis of secretory granules in dog pancreatic duct epithelial cells (PDEC) can be stimulated by pharmacological activation of cAMP-dependent protein kinase (PKA) or protein kinase C (PKC), as well as by an increase of intracellular free Ca2+ concentration ([Ca2+]i). In this study, we examined whether exocytosis in these cells is modulated by activation of endogenous P2Y receptors, which increase cAMP and [Ca2+]i. Low concentrations of ATP (<10 μM) induced intracellular Ca2+ oscillation but no significant exocytosis. In contrast, 100 μM ATP induced a sustained [Ca2+]i rise and increased the exocytosis rate sevenfold. The contribution of Ca2+ or cAMP pathways to exocytosis was tested by using the Ca2+ chelator BAPTA or the PKA inhibitors H-89 or Rp-8-bromoadenosine 3',5'-cyclic monophosphorothioate. Removal of [Ca2+]i rise or inhibition of PKA each partially reduced exocytosis; when combined, they abolished exocytosis. In conclusion, ATP at concentrations >10 μM stimulates exocytosis from PDEC through both Ca2+ and cAMP pathways.
M-cadherin transcription in satellite cells from normal and denervated muscle
Authors: Maier Annette , Bornemann Antje
Published: February 2004

Satellite cells (SC) in adult muscle are quiescent in the G0 phase of the cell cycle. In the present study we determined whether SC after denervation upregulate M-cadherin, an adhesion molecule that is upregulated with differentiation and fusion. We also monitored primary cultures of SC from denervated muscle for expression of the transcription factors of the MyoD family to determine whether SC from denervated muscle can be activated in vitro. Hindlimb muscles of rats were denervated under anesthesia, and rats were killed after 2-28 days. The SC of the denervated limbs were pooled and either assessed for M-cadherin mRNA by using real-time RT-PCR or cultured in vitro. The cultures were processed for RT-PCR or immunofluorescence for expression of the transcription factors of the MyoD family. Hindlimb muscles of M-cadherin knockout mice were denervated under anesthesia, mice were killed after 2-28 days, and cells were stained for β-galactosidase activity by X-gal histochemistry. In vitro, primary SC cultures from rat muscle denervated for 2-28 days expressed transcripts of myf5, MyoD, myogenin, and MRF4 as SC from normal innervated muscle. In vivo, M-cadherin transcription was not upregulated in SC from denervated rat muscle when compared with normal muscle. Moreover, β-galactosidase activity was not detected in denervated mouse muscle. The finding that SC do not upregulate M-cadherin after denervation supports the notion that they remain in the G0 phase of the cell cycle in vivo. However, the cells retain the capacity to pass through the proliferative and differentiative program when robustly stimulated to do so in vitro.
Extended life span is associated with insulin resistance in a transgenic mouse model of insulinoma secreting human islet amyloid polypeptide
Authors: Andrikopoulos Sofianos , Hull Rebecca L. , Verchere C. Bruce , Wang Feng , Wilbur Shani M. , Wight Thomas N. , Marzban Lucy , Kahn Steven E.
Published: February 2004

Pancreatic amyloid is found in patients with insulinomas and type 2 diabetes. To study mechanisms of islet amyloidogenesis, we produced transgenic mice expressing the unique component of human islet amyloid, human islet amyloid polypeptide (hIAPP). These mice develop islet amyloid after 12 mo of high-fat feeding. To determine whether we could accelerate the rate of islet amyloid formation, we crossbred our hIAPP transgenic animals with RIP-Tag mice that develop islet tumors and die at 12 wk of age from hypoglycemia. At 12 wk of age, this new line of hIAPP×RIP-Tag mice was heavier (29.7 ± 1.0 vs. 25.0 ± 1.3 g, P < 0.05) and had increased plasma glucose levels (4.6 ± 0.4 vs. 2.9 ± 0.6 mmol/l, P < 0.05) compared with littermate RIP-Tag mice. However, the hIAPP×RIP-Tag mice did not display islet amyloid or amyloid fibrils despite high circulating hIAPP levels (24.6 ± 7.0 pmol/l). Interestingly, hIAPP×RIP-Tag mice had a longer life span than RIP-Tag mice (121 ± 8 vs. 102 ± 5 days, P < 0.05). This increase in life span in hIAPP×RIP-Tag was positively correlated with body weight ( r = 0.48, P < 0.05) and was associated with decreased insulin sensitivity compared with RIP-Tag mice. hIAPP×RIP-Tag mice did not develop amyloid during their 4-mo life span, suggesting that increased hIAPP secretion is insufficient for islet amyloid formation within such a short time. However, hIAPP×RIP-Tag mice did have an increase in life span that was associated with insulin resistance, suggesting that hIAPP has extrapancreatic effects, possibly on peripheral glucose metabolism.
Additive effects of cortisol and growth hormone on regional and systemic lipolysis in humans
Authors: Djurhuus C. B. , Gravholt C. H. , Nielsen S. , Pedersen S. B. , Møller N. , Schmitz O.
Published: February 2004

Growth hormone (GH) and cortisol are important to ensure energy supplies during fasting and stress. In vitro experiments have raised the question whether GH and cortisol mutually potentiate lipolysis. In the present study, combined in vivo effects of GH and cortisol on adipose and muscle tissue were explored. Seven lean males were examined four times over 510 min. Microdialysis catheters were inserted in the vastus lateralis muscle and in the subcutaneous adipose tissue of the thigh and abdomen. A pancreatic-pituitary clamp was maintained with somatostatin infusion and replacement of GH, insulin, and glucagon at baseline levels. At t = 150 min, administration was performed of NaCl (I), a 2 μg·kg-1·min-1hydrocortisone infusion (II), a 200-μg bolus of GH (III), or a combination of II and III (IV). Systemic free fatty acid (FFA) turnover was estimated by [9,10-3H]palmitate appearance. Circulating levels of glucose, insulin, and glucagon were comparable in I-IV. GH levels were similar in I and II (0.50 ± 0.08 μg/l, mean ± SE). Peak levels during III and IV were ∼9 μg/l. Cortisol levels rose to ∼900 nmol/l in II and IV. Systemic (i.e., palmitate fluxes, s-FFA, s-glycerol) and regional (interstitial adipose tissue and skeletal muscle) markers of lipolysis increased in response to both II and III. In IV, they were higher and equal to the isolated additive effects of the two hormones. In conclusion, we find that GH and cortisol stimulate systemic and regional lipolysis independently and in an additive manner when coadministered. On the basis of previous studies, we speculate that the mode of action is mediated though different pathways.
Effects of diet and exposure to hindlimb suspension on estrous cycling in Sprague-Dawley rats
Authors: Tou Janet C. L. , Grindeland Richard E. , Wade Charles E.
Published: February 2004

Various factors can disrupt the female reproductive cycle resulting in subfertility. The primary objective of this study was to determine whether physiological changes associated with exposure to hypogravity disrupt reproductive cycles. The hindlimb suspension (HLS) model was used to simulate the major physiological effects of hypogravity in female Sprague-Dawley rats. Also, to determine whether diet may influence reproductive results, rats were fed purified American Institute of Nutrition (AIN)-93G or chow diet. Rats ( n = 9-11/group) subjected to HLS had lengthened estrous cycles due to prolonged diestrus, indicating hypoestrogenism. Interestingly, HLS rats fed AIN-93G but not chow diet had significantly reduced time spent in estrus and decreased plasma estradiol. Attenuation of hypoestrogenism in the chow-fed rats suggested that diet provided an exogenous source of estrogen. The mechanism involved in the disruption of estrous cycling remains to be determined. HLS increased urinary corticosterone (CORT) levels during the initial 4 days of HLS, suggesting that physiological responses to acute stress may be a potential mechanism in the disruption of estrous cycles. Higher basal urinary CORT was observed in rats fed chow vs. AIN-93G diet. HLS resulted in increased urinary CORT. However, two-way ANOVA indicated a significant HLS effect ( P < 0.001) but no effect of HLS × diet effect on urinary CORT levels, suggesting that estrogenic activity associated with the chow diet did not enhance the stress response. The results of this study indicate that HLS, diet, and the combination of HLS and diet influence estrous cycling. This has important implications for future reproductive success in the hypogravity environment of space.
Treatment of type 2 diabeticdb/dbmice with a novel PPARγ agonist improves cardiac metabolism but not contractile function
Authors: Carley Andrew N. , Semeniuk Lisa M. , Shimoni Yakhin , Aasum Ellen , Larsen Terje S. , Berger Joel P. , Severson David L.
Published: February 2004

Hearts from insulin-resistant type 2 diabetic db/db mice exhibit features of a diabetic cardiomyopathy with altered metabolism of exogenous substrates and reduced contractile performance. Therefore, the effect of chronic oral administration of 2-(2-(4-phenoxy-2-propylphenoxy)ethyl)indole-5-acetic acid (COOH), a novel ligand for peroxisome proliferator-activated receptor-γ that produces insulin sensitization, to db/db mice (30 mg/kg for 6 wk) on cardiac function was assessed. COOH treatment reduced blood glucose from 27 mM in untreated db/db mice to a normal level of 10 mM. Insulin-stimulated glucose uptake was enhanced in cardiomyocytes from COOH-treated db/db hearts. Working perfused hearts from COOH-treated db/db mice demonstrated metabolic changes with enhanced glucose oxidation and decreased palmitate oxidation. However, COOH treatment did not improve contractile performance assessed with ex vivo perfused hearts and in vivo by echocardiography. The reduced outward K+currents in diabetic cardiomyocytes were still attenuated after COOH. Metabolic changes in COOH-treated db/db hearts are most likely indirect, secondary to changes in supply of exogenous substrates in vivo and insulin sensitization.
PPARγ is not required for the inhibitory actions of PGJ2on cytokine signaling in pancreatic β-cells
Authors: Weber Sarah M. , Scarim Anna L. , Corbett John A.
Published: February 2004

Peroxisome proliferator-activated receptor (PPAR)γ agonists, such as 15-deoxy-Δ12,14-prostaglandin J2(PGJ2) and troglitazone, have been shown to elicit anti-inflammatory effects in pancreatic β-cells that include inhibition of cytokine-stimulated inducible nitric oxide synthase (iNOS) gene expression and production of nitric oxide. In addition, these ligands impair IL-1-induced NF-κB and MAPK as well as IFN-γ-stimulated signal transducer and activator of transcription (STAT)1 activation in β-cells. The purpose of this study was to determine if PPARγ activation participates in the anti-inflammatory actions of PGJ2in β-cells. Pretreatment of RINm5F cells for 6 h with PGJ2results in inhibition of IL-1-stimulated IκB degradation and IFN-γ-stimulated STAT1 phosphorylation. Overexpression of a dominant-negative (dn) PPARγ mutant or treatment with the PPARγ antagonist GW-9662 does not modulate the inhibitory actions of PGJ2on cytokine signaling in RINm5F cells. Although these agents fail to attenuate the inhibitory actions of PGJ2on cytokine signaling, they do inhibit PGJ2-stimulated PPARγ response element reporter activity. Consistent with the inability to attenuate the inhibitory actions of PGJ2on cytokine signaling, neither dnPPARγ nor GW-9662 prevents the inhibitory actions of PGJ2on IL-1-stimulated iNOS gene expression or nitric oxide production by RINm5F cells. These findings support a PPARγ-independent mechanism by which PPARγ ligands impair cytokine signaling and iNOS expression by islets.
Does menarche mark a period of elevated resting metabolic rate?
Authors: Spadano Jennifer L. , Bandini Linda G. , Must Aviva , Dallal Gerard E. , Dietz William H.
Published: February 2004

Resting metabolic rate (RMR) and body composition were measured in 44 initially nonoverweight girls at three time points relative to menarche: premenarche (Tanner stage 1 or 2), menarche (±6 mo), and 4 yr after menarche. Mean absolute RMR was 1,167, 1,418, and 1,347 kcal/day, respectively. Absolute RMR was statistically significantly higher at menarche than at 4 yr after menarche despite statistically significantly less fat-free mass (FFM) and fat mass (FM), suggesting an elevation in RMR around the time of menarche. The pattern of change in RMR, adjusted for FFM, log transformed FM, age, race, parental overweight, and two interactions (visit by parental overweight, parental overweight by FFM), was also considered. Adjusted RMR did not differ statistically between the visits for girls with two normal-weight parents. For girls with at least one overweight parent, adjusted RMR was statistically significantly lower 4 yr after menarche than at premenarche or menarche. Thus parental overweight may influence changes that occur in RMR during adolescence in girls.
UCP-mediated energy depletion in skeletal muscle increases glucose transport despite lipid accumulation and mitochondrial dysfunction
Authors: Han Dong-Ho , Nolte Lorraine A. , Ju Jeong-Sun , Coleman Trey , Holloszy John O. , Semenkovich Clay F.
Published: February 2004

To address the potential role of lipotoxicity and mitochondrial function in insulin resistance, we studied mice with high-level expression of uncoupling protein-1 in skeletal muscle (UCP-H mice). Body weight, body length, and bone mineral density were decreased in UCP-H mice compared with wild-type littermates. Forelimb grip strength and muscle mass were strikingly decreased, whereas muscle triglyceride content was increased fivefold in UCP-H mice. Electron microscopy demonstrated lipid accumulation and large mitochondria with abnormal architecture in UCP-H skeletal muscle. ATP content and key mitochondrial proteins were decreased in UCP-H muscle. Despite mitochondrial dysfunction and increased intramyocellular fat, fasting serum glucose was 22% lower and insulin-stimulated glucose transport 80% higher in UCP-H animals. These beneficial effects on glucose metabolism were associated with increased AMP kinase and hexokinase activities, as well as elevated levels of GLUT4 and myocyte enhancer factor-2 proteins A and D in skeletal muscle. These results suggest that UCP-H mice have a mitochondrial myopathy due to depleted energy stores sufficient to compromise growth and impair muscle function. Enhanced skeletal muscle glucose transport in this setting suggests that excess intramyocellular lipid and mitochondrial dysfunction are not sufficient to cause insulin resistance in mice.
The dynamics of glomerular filtration in the puerperium
Authors: Hladunewich M. A. , Lafayette R. A. , Derby G. C. , Blouch K. L. , Bialek J. W. , Druzin M. L. , Deen W. M. , Myers B. D.
Published: February 2004

We evaluated the glomerular filtration rate (GFR) during the second postpartum week in 22 healthy women who had completed an uncomplicated pregnancy. We used physiological techniques to measure GFR, renal plasma flow, and oncotic pressure and computed a value for the two-kidney ultrafiltration coefficient ( Kf). We compared these findings with those in pregnant women previously studied on the first postpartum day as well as nongravid women of reproductive age. Healthy female transplant donors of reproductive age permitted the morphometric analysis of glomeruli and computation of the single-nephron Kf. The aforementioned physiological and morphometric measurements were utilized to estimate transcapillary hydraulic pressure (ΔP) from a mathematical model of glomerular ultrafiltration. We conclude that postpartum day 1 is associated with marked glomerular hyperfiltration (+41%). A theoretical analysis of GFR determinants suggests that depression of glomerular capillary oncotic pressure, the force opposing the formation of filtrate, is the predominant determinant of early elevation of postpartum GFR. A reversal of the gestational hypervolemia and hemodilution, still evident on postpartum day 1, eventuates by postpartum week 2. An elevation of oncotic pressure in the plasma that flows axially along the glomerular capillaries to supernormal levels ensues; however, GFR remains modestly elevated (+20%) above nongravid levels. An analysis of filtration dynamics at this time suggests that a significant increase in ΔP by up to 16%, an ∼50% increase in Kf, or a combination of smaller increments in both must be invoked to account for the persistent hyperfiltration.
Thyroid hormone modulates rabbit proximal straight tubule paracellular permeability
Authors: Baum Michel , Quigley Raymond
Published: February 2004

Proximal straight tubules (PST) from both neonatal and hypothyroid adult rabbits have a lower rate of passive volume absorption when perfused with a high-chloride solution simulating late proximal tubular fluid than adult rabbit PST. We hypothesized that the maturational increase in serum thyroid hormone levels mediates the developmental changes in PST paracellular permeability. Neonatal tubules had lower chloride permeability, higher transepithelial resistance, but comparable mannitol permeability compared with adult PST. The present in vitro microperfusion study directly examined whether thyroid hormone affects passive solute flux and whether thyroid hormone could explain the developmental changes in PST paracellular permeability. Passive chloride transport was 62.1 ± 4.5, 23.1 ± 7.7, and 111.6 ± 5.6 pmol·mm-1·min-1 in PST from euthyroid, hypothyroid, and hypothyroid animals that received thyroid treatment, respectively (control different from hypothyroid and thyroid treatment at P < 0.05). This was due to a thyroid hormone-mediated change in chloride permeability ( PCl). Mannitol permeability was 3.65 + 1.03, -0.19 + 0.72, and 3.60 + 1.12 × 10-6 cm/s in PST from euthyroid animals, hypothyroid animals, and hypothyroid rabbits that received thyroid replacement, respectively ( P < 0.05 hypothyroid vs. euthyroid and thyroid replacement). We demonstrate that PST from hypothyroid animals have a higher passive PNa/ PCl and PHCO3/ PCl than euthyroid controls. Finally, we examined whether these changes in permeability were paralleled by a change in PST paracellular resistance. Resistance was measured by current injection and cable analysis. The resistance in PST from hypothyroid rabbits was 6.3 ± 0.8 Ω·cm2, which was not different from control of 4.8 ± 0.7 Ω·cm2, or 7.0 ± 0.7 Ω·cm2 in hypothyroid animals that received thyroid replacement. Therefore, the maturational increase in thyroid hormone levels does not fully explain the developmental changes in the paracellular pathway.
The story so far: molecular regulation of the heme oxygenase-1 gene in renal injury
Authors: Sikorski Eric M. , Hock Thomas , Hill-Kapturczak Nathalie , Agarwal Anupam
Published: February 2004

Heme oxygenases (HOs) catalyze the rate-limiting step in heme degradation, resulting in the formation of iron, carbon monoxide, and biliverdin, the latter of which is subsequently converted to bilirubin by biliverdin reductase. Recent attention has focused on the biological effects of product(s) of this enzymatic reaction, which have important antioxidant, anti-inflammatory, and cytoprotective functions. Two major isoforms of the HO enzyme have been described: an inducible isoform, HO-1, and a constitutively expressed isoform, HO-2. A third isoform, HO-3, closely related to HO-2, has also been described. Several stimuli implicated in the pathogenesis of renal injury, such as heme, nitric oxide, growth factors, angiotensin II, cytokines, and nephrotoxins, induce HO-1. Induction of HO-1 occurs as an adaptive and beneficial response to these stimuli, as demonstrated by studies in renal and non-renal disease states. This review will focus on the molecular regulation of the HO-1 gene in renal injury and will highlight the interspecies differences, predominantly between the rodent and human HO-1 genes.