bluuebunny/crossref_metadata_2025_split huggingface dataset:
Excitation and contraction in atrial and ventricular myocardium of the guinea‐pig
Authors: ÁSGRÍMSSON H. , JÓHANNSSON M. , ARNARDÓTTIR S. Á. 
Published: December 2008

Several parameters of excitation‐contraction coupling were compared in two types of muscle, using thin strips from the left atria and papillary muscles from the right ventricles of guinea‐pigs. (1) The duration of the action potential and twitch is much longer in ventricular than in atrial muscle. (2) Mechanical restitution can usually be described by a monoexponential function in ventricular and biexponential function in atrial muscle. (3) Post‐extrasystolic potentiation, when related to the steady state force, is greater in ventricular muscle. (4) When priming with paired‐pulse stimulation, mechanical restitution can be studied after the short interval and after the long interval. In atrial muscle, mechanical restitution is very similar after the short and long intervals but in ventricular muscle they are different in size. (5) Ryanodine (10‐6 M) can decrease the steady state force to about 10% of control in atrial but only to about 35% in ventricular muscle. Ryanodine (10‐8 M) causes the slow phase of restitution in atrial muscle to disappear but in ventricular muscle only increases the rate of mechanical restitution. (6) Ca‐antagonists (Cd2+ 0.2 mM) can decrease the steady state force to zero in atrial and ventricular muscle. Ca‐antagonists, in low concentrations (Cd2+ 0.01 mM), mainly affected the fast phase of mechanical restitution. (7) The recirculation fraction of calcium was about 0.64 in atrial and 0.27 in ventricular muscle.The findings are discussed in the light of known ultrastructural differences between atrial and ventricular myocardium.
Electrical field stimulation of rat mesenteric small arteries: force and free cytosolic calcium during neurogenic contractions and mechanisms of non‐neurogenic relaxations
Authors: JENSEN PETER E. 
Published: December 2008

The effect of transmural electrical field stimulation (TEFS) of rat mesenteric small arteries was studied. Stimulation parameters were selected to cause tetrodotoxin (TTX) sensitive contractions. In arteries precontracted with PGF2αin the presence of phentolamine, TTX insensitive relaxation could be induced by TEFS. The relaxing effect of TEFS required higher stimulation amplitude and duration than the contractions. Thus, by appropriately choosing stimulation parameters, contractile responses could be elicited which were little affected by any relaxing effect, while contractions were abolished by TTX at any stimulation conditions in the present study.The contractions were abolished by cold storage and almost completely inhibited by phentolamine. Thus, contractions were neurogenic and primarily caused by noradrenaline. At low frequencies, TEFS caused phentolamine sensitive increases in free cytosolic calcium with no contractions. At higher frequencies, there was a further increase in free cytosolic calcium, associated with contraction. Only at high frequencies, noradrenaline from nerves caused sensitization of the contractile filaments to free cytosolic calcium as during stimulation with exogenous noradrenaline.The relaxations were associated with decreases in free cytosolic calcium and were probably non‐neurogenic since they were resistant to TTX, cold storage, capsaicin, and repeated stimulation. Furthermore, relaxations were almost completely abolished by increasing extracellular potassium to 40 mM or by adding tetraethylammonium chloride or 4‐aminopyridine. Relaxations were also reduced by ouabain and potassium free conditions.
Atrial natriuretic peptide and its mRNA in heart and brain of vasopressin‐deficient Brattleboro rats
Authors: ARJAMAA O. , TASKINEN T. , KANERVO A. , VUOLTEENAHO O. , LEPPALUOTO J. 
Published: December 2008

To understand the secretion and synthesis of atrial natriuretic peptide we measured immunoreactive atrial natriuretic peptide from plasma, heart tissues and brain areas, and ANP mRNA was determined from heart auricles and ventricles of vasopressin‐deficient Brattleboro rats (DI) and from desmopressin treated Brattleboro rats (DI + DDAVP). Long‐Evans rats (LE) served as controls. DI + DDAVP rats were given for 3 days sc. injections of 0.5/g l‐desamino‐8‐D‐arginine vasopressin in 1 ml. saline twice a day. The rats were housed in single metabolic cages and urinary output and water intake were measured daily. All the body and organ weight parameters were similar in the three groups when the rats were killed. No change was seen in the plasma ANP level between the groups. The right ventricle of DI + DDAVP rats had significantly (P < 0.05) higher concentration of ANP than LE rats (15.8 + 4.4 vs. 3.4 + 0.6 ng mg“1tissue). The left ventricle of DI and DI+DDAVP had significantly (P < 0.05) lower amounts of ANP mRNA than LE rats (0.5 ± 0.2 vs. 1.3 + 0.2 and 0.5 + 0.1 vs. 1.3 + 0.2 arbitrary units). In the hypothalamus, the ANP concentration was significantly (P < 0.05) lower both in DI and in DI + DDAVP rats than in LE rats (9.3 ±1.3 vs. 14.5 ±±1.6 and 6.1+0.6 vs. 14.5 ± 1.6 pg mg‐1tissue).To conclude, although the water intake and urinary output of DI rats were changed towards normal with desmopressin treatment, the heart ventricular and hypothalamic ANP did not parallel the change. Desmopressin increased the ANP concentration in the right ventricle of DI rats. Thus the correction of the complete vasopressin deficiency‐does not appear to associate with synthesis or release of atrial natriuretic peptide in heart or hypothalamus.
Nitric oxide regulates coronary blood flow at various coronary arterial pressures in intact porcine hearts
Authors: OFFSTAD J. , NAESS P. A. , AKSNES G. , TØNNESSEN T. , ILEBEKK A. , KIRKEBØEN K. A. 
Published: December 2008

Nitric oxide (NO) is known to regulate basal coronary blood flow (CBF). The objective of the present study was to examine the importance of NO in CBF regulation at various coronary arterial pressures (CAPs) in vivo.Experiments were performed in 11 open‐chest pentobarbitone sodium anaesthetized pigs. CAP was reduced in steps by a hydraulic occluder on the mid left anterior descending coronary artery (LAD) before and after a 5‐min intracoronary infusion of the inhibitor of NO synthesis, A‐nitro‐L‐arginine (NOARG, 30 /imo\ min“1). CAP was recorded and NOARG infused through a catheter inserted into the LAD just distal to the occluder. CBF was measured by Doppler flowmetry on the LAD.NOARG significantly reduced CBF by 11±4, 20 ± 5, 10 ± 3, 15 ± 4, 19 ± 2, 25 ± 4 and 25 ± 5 mL min‐1 100 g‐1 (mean ± SE) at CAPs of 30 (n = 6), 40 (n = 9), 50 (n= 9), 60 (n = 9), 70 (n = 9), 80 (n = 8) and 90 (n = 6) mmHg, respectively. These decrements were not statistically different, but the percentage reductions in CBF after infusion of NOARG were significantly greatest at the lowest CAPs. The slight haemodynamic alterations induced by NOARG could not explain the reductions in CBF. Thus, the reductions in CBF after infusion of NOARG were caused by inhibition of a continuous NO release from the coronary endothelium.Coronary NO contributes significantly to CBF at all CAPs between 30 and 90 mmHg. The pronounced reduction in CBF during NO inhibition at the lower CAPs indicates an important vasodilating role of intact endothelium in a region supplied by a stenosed coronary artery.
Villus tip microcirculation in the rat duodenum
Authors: SABABI M. , HOLM L. 
Published: December 2008

Duodenal microvascular perfusion was measured in anaesthetized rats both as erythrocyte velocity (rev) in capillaries in the tip of duodenal villi and by laser‐Doppler flowmetry (LDF). Rev increased transiently by about 40% during the first 5 min of luminal exposure to 10 mM (NaCl to isotonicity) hydrochloric acid, while LDF measurements only showed a transient increase of about 7%, followed by a prolonged reduction by about 11%. Since the LDF signal is a measure not only of villus microcirculation but also of blood flow in the deeper layers, our results may suggest that blood flow is transiently redistributed towards the villi from deeper layers. Hypovolaemia (bleeding by ∼ 10% of the blood volume) reduced rev in the capillaries by 63% during the first 5 min of hypotension, but reduced LDF only by about 12%, a discrepancy which suggests a shift in blood flow from the tip to deeper layers. The experiments were performed under atmospheric oxygen tension, but rev in the villus capillaries exposed to abdominal Po2 (∼ 45 mmHg) did not differ significantly from the values obtained under the atmospheric oxygen condition, either in the resting situation or during hypotension.In conclusion, we have developed an animal model in which red cell velocity in the tip of the duodenal villi can be studied for several hours and in which alkaline secretion from the duodenum is similar to previously reported levels. Our results show that the villus tip microcirculation in the duodenum may respond differently from that of deeper layers of the duodenal wall.
ERG OFF response in frog retina: light adaptation and effect of 2‐amino‐4‐phosphonobutyrate
Authors: POPOVA E. , KUPENOVA P. , VITANOVA L. , MITOVA L. 
Published: December 2008

The intensity‐response (V/log I) function of ERG OFF response (d‐wave) in dark and light adapted superfused frog eyecups was investigated before and after blockade of the retinal ON channel by 2‐amino‐4‐phosphonobutyrate (APB). The V/logI function of the dark adapted d‐wave had two distinct components, each of them consisting of an ascendent and descendent part. In eyes adapted to mesopic or photopic background the V/log I function had only one component. It was shifted to the right along the intensity axis, had a steeper slope and a higher maximal response amplitude compared with the two components of the dark‐adapted V/log I curve.Perfusion with 200 μmol APB markedly increased the d‐wave amplitude at all stimulus intensities except for the threshold ones in both dark and light adapted eyes. The position of the V/log I curve was shifted slightly to the left along the intensity axis in dark adapted eyes, but was not changed in light adapted eyes. Thus the adaptational mechanism responsible for changes in the decremental sensitivity with increased background illumination was not altered by APB.The effect of APB was studied also in chromatically adapted eyes, in which the responses were predominantly mediated by one photoreceptor type. The results showed that the potentiating effect of APB on d‐wave did not depend on photoreceptor input.
Ca selectivity of the transduction channels in the hair cells of the frog sacculus
Authors: GENSEN F. JØ , KROESE A. B. A. 
Published: December 2008

The extracellular receptor currents evoked by step displacements of the otolithic membrane of the isolated saccular macula ofRana esculentawere recorded under transepthelial voltage clamp conditions. With the aim to depolarize the hair cells and increase the fractional resistance of the apical membrances, the basal side of the preparation was bathed in saline with an increased K+concentration (62 mm). This caused a shift in the non‐linear receptor current‐voltage relation along the voltage axis of ‐51 mVpL10 mV; (mean pL SD; n= 32) and a reduction in the transepithelial resistance of 10%. Under these conditions the electrical properties of the macula are assumed to be controlled by the apical membranes. The effects of different concentrations of Ca2+in the apical solution on the receptor current‐voltage relation were examined.Change of the apical Ca2+concentration (range 3 mM to 70 μM) varied the transepithelial voltage at which the receptor current was zero (Vrev). Fitting a modified constant field equation to the relation between the apical Ca2+concentration and the change in Vrevgave an estimate of Pca/Pkof the transduction channels of 212. Furthermore, a high relative permeability of the transduction channels for other divalent cations (Ba2+, Sr2+) was measured, whereas Mn2+inhibited the receptor current. The receptor current was inhibited by amiloride (IC503.2 μM) and nifedipine (IC501.9 μM pL0.6 μM).Reduction of the apical Ca2+concentration to 90μM in standard apical solution reduced the size of the receptor current to 67% pL 30% (n=17) compared to control but did not affect the shape of the receptor current ‐voltage relation. Subsequent substitution of K+by Na+caused a further reduction of the receptor current to 32% pL29% (n=9), changed the receptor current‐voltage relation into a linear relation and diminished the adaptation of the receptor current.These results indicate that the mechano‐electrical transduction channels of the frog saccular hair cells are highly selective to Ca2+and that the conductance of the channels may be influenced by the apical monovalent cation species.
Fluorescence Investigation of the Binding of Model PDT Drugs to Nonionic and Zwitterionic Surfactants
Authors: Patel Sunita , Datta Anindya 
Published: December 2008

AbstractThe binding of two model photodynamic therapy drugs, chlorin p6 and purpurin 18, with surfactants has been studied using steady‐state and time‐resolved fluorescence techniques. The surfactants used are amphiphilic nonionic surfactant (Tween 80 and Tween 40) and zwitterionic surfactant (HAPS). These have applications in drug delivery. The studies have been performed at pH 7 and 5 for chlorin p6 and at pH 7 for purpurin 18. The binding constants have been estimated from the change in fluorescence parameters and have been compared with those for Cremophor EL and human serum albumin. Chlorin p6 is found to bind to the surfactants to a greater extent at pH 5 than at pH 7. The same ionic species of chlorin p6 is found to exist at the maximum concentrations of the surfactants.
Photoprocesses of Xanthene Dyes Bound to Lysozyme or Serum Albumin
Authors: Zhang Yazhou , Görner Helmut 
Published: December 2008

AbstractThe ground and excited state processes of eosin, erythrosin and rose bengal in aqueous solution were studied in the presence of lysozyme or bovine serum albumin (BSA). Noncovalent protein‐dye binding was analyzed by circular dichroism (CD), fluorescence and UV–Vis absorption spectroscopy. The effects of protein concentrations and pH were studied. Fluorescence quenching of the dye takes place due to binding to lysozyme and fluorescence enhancement due to low loading to BSA. The effects of proteins on the xanthene triplet state and its precursor were observed by time‐resolved 530 nm photolysis. The triplet lifetime is quenched by lysozyme and prolonged by loading to BSA. Light‐induced damages on both the dyes and proteins were observed under exclusion of oxygen. Photo‐oxidation is efficient for lysozyme and lower for BSA. The CD signal of the eosin/BSA system is maximum at pH 4, where the photo‐oxidation is minor.
PERSPECTIVE ARTICLE: Why do adaptive immune responses cross‐react?
Authors: Fairlie‐Clarke Karen J. , Shuker David M. , Graham Andrea L. 
Published: December 2008

AbstractAntigen specificity of adaptive immune responses is often in the host’s best interests, but with important and as yet unpredictable exceptions. For example, antibodies that bind to multiple flaviviral or malarial species can provide hosts with simultaneous protection against many parasite genotypes. Vaccinology often aims to harness such imprecision, because cross‐reactive antibodies might provide broad‐spectrum protection in the face of antigenic variation by parasites. However, the causes of cross‐reactivity among immune responses are not always known, and here, we explore potential proximate and evolutionary explanations for cross‐reactivity. We particularly consider whether cross‐reactivity is the result of constraints on the ability of the immune system to process information about the world of antigens, or whether an intermediate level of cross‐reactivity may instead represent an evolutionary optimum. We conclude with a series of open questions for future interdisciplinary research, including the suggestion that the evolutionary ecology of information processing might benefit from close examination of immunological data.
Genes and Molecules of Lactobacilli Supporting Probiotic Action
Authors: Lebeer Sarah , Vanderleyden Jos , De Keersmaecker Sigrid C. J. 
Published: December 2008

SUMMARYLactobacilli have been crucial for the production of fermented products for centuries. They are also members of the mutualistic microbiota present in the human gastrointestinal and urogenital tract. Recently, increasing attention has been given to their probiotic, health-promoting capacities. Many human intervention studies demonstrating health effects have been published. However, as not all studies resulted in positive outcomes, scientific interest arose regarding the precise mechanisms of action of probiotics. Many reported mechanistic studies have addressed mainly the host responses, with less attention being focused on the specificities of the bacterial partners, notwithstanding the completion ofLactobacillusgenome sequencing projects, and increasing possibilities of genomics-based and dedicated mutant analyses. In this emerging and highly interdisciplinary field, microbiologists are facing the challenge of molecular characterization of probiotic traits. This review addresses the advances in the understanding of the probiotic-host interaction with a focus on the molecular microbiology of lactobacilli. Insight into the molecules and genes involved should contribute to a more judicious application of probiotic lactobacilli and to improved screening of novel potential probiotics.
Recreational Physical Activity Modifies the Association Between a Common GH1 Polymorphism and Colorectal Cancer Risk
Authors: Khoury-Shakour Sana , Gruber Stephen B. , Lejbkowicz Flavio , Rennert Hedy S. , Raskin Leon , Pinchev Mila , Rennert Gad 
Published: December 2008

AbstractGrowth hormone may be associated with the development of colorectal cancer directly and/or indirectly via increased serum level of insulin-like growth factor (IGF-I). Regular physical activity can decrease insulin resistance and modulates IGF-I production. A common polymorphism in the GH1 gene, rs2665802, was previously shown to be associated with lower IGF-I levels and decreased colorectal cancer (CRC) risk. We investigated the association of this polymorphism and physical activity with colorectal cancer risk in a case-control study.Methods: The analysis includes 3,041 (1,402 cases and 1,639 controls) participants in the Molecular Epidemiology of Colorectal Cancer study, a population-based case-control study in Northern Israel. Analysis was carried out separately in two sets. The first set included 1,248 subjects (625 cases, 623 controls), and the second validation set consisted of 1,793 subjects (777 cases, 1,016 controls).Results: No association was found between the studied polymorphism and CRC risk. However, evaluation of gene environment interactions revealed an interaction between leisure time physical activity and the GH1 polymorphism, which was consistent in both sets (Pinteraction = 0.005). The genotype AA was associated with decreased risk of CRC among individuals who did not engage in any such activity (odds ratio, 0.76; 95% confidence interval, 0.52-0.98), whereas the same genotype was marginally associated with increased risk among individuals who reported physical activity (odds ratio, 1.38; 95% confidence interval, 0.98-1.94).Conclusions: We found that the A allele of the rs2665802 polymorphism is associated with reduced risk of CRC only among physically inactive individuals, indicating an interaction between physical activity and the growth hormone/IGF-I system. A replication of the observed findings and further investigation of the underlying mechanism is warranted. (Cancer Epidemiol Biomarkers Prev 2008;17(12):3314–8)
Green Tea, Soy, and Mammographic Density in Singapore Chinese Women
Authors: Wu Anna H. , Ursin Giske , Koh Woon-Puay , Wang Renwei , Yuan Jian-Min , Khoo Kei-Siong , Yu Mimi C. 
Published: December 2008

AbstractThere is increasing evidence from observational studies that breast cancer risk is inversely associated with soy and green tea consumption. We investigated the effects of these two dietary agents on mammographic density, a well-established biomarker for breast cancer risk, in a cross-sectional analysis of mammograms and validated food frequency questionnaires from 3,315 Chinese women in Singapore. Percent mammographic density (PMD) was assessed using a reproducible computer-assisted method. We used generalized linear models to estimate PMD by intake of soy, green tea, and black tea while adjusting for potential confounders. Daily green tea drinkers showed statistically significantly lower PMD (19.5%) than non-tea drinkers (21.7%; P = 0.002) after adjusting for relevant covariates. This difference in PMD between daily green tea drinkers and non-tea drinkers remained statistically significant after adjustment for soy (P = 0.002); the effect was more apparent among lower soy consumers (Q1-Q3; 21.9% versus 19.4%; P = 0.002) than in higher (Q4) consumers (20.9% versus 19.5%; P = 0.32). Black tea intake was unrelated to PMD. Only among postmenopausal women who reported very high soy intake (Q4) compared with those with less soy intake was there any association noted between PMD and soy intake (18.9% versus 20.5%; P = 0.035). Following adjustment for green tea intake, the association between soy and PMD was no longer statistically significant (P = 0.52). Our findings suggest that both regular green tea and high soy intake may have beneficial effects on the breast; the effect of green tea on PMD may be stronger than the effect of soy. (Cancer Epidemiol Biomarkers Prev 2008;17(12):3358–65)
A Liquid Chromatography-Mass Spectrometry Method for the Simultaneous Measurement of 15 Urinary Estrogens and Estrogen Metabolites: Assay Reproducibility and Interindividual Variability
Authors: Falk Roni T. , Xu Xia , Keefer Larry , Veenstra Timothy D. , Ziegler Regina G. 
Published: December 2008

AbstractBackground: Accurate, reproducible, and sensitive measurements of endogenous estrogen exposure and individual patterns of estrogen metabolism are needed for etiologic studies of breast cancer. We have developed a high-performance liquid chromatography-tandem mass spectrometry method to quantitate simultaneously 15 urinary estrogens and estrogen metabolites (EM): estrone; estradiol; 3 catechol estrogens; 5 estrogens in the 16α pathway, including estriol; and 5 methoxy estrogens.Methods: Overnight urines were obtained from 45 participants. For the reproducibility study, two blinded, randomized aliquots from 5 follicular and 5 luteal premenopausal women, 5 naturally postmenopausal women, and 5 men were assayed in each of four batches. Assay coefficients of variation and intraclass correlation coefficients were calculated with ANOVA models. Data from the additional 25 participants were added to compare EM levels by menstrual/sex group and assess interindividual variability.Results: For each EM, overall coefficients of variation were ≤10%. Intraclass correlation coefficients for each menstrual/sex group were generally ≥98%. Although geometric mean EM concentrations differed among the four groups, rankings were similar, with estriol, 2-hydroxyestrone, estrone, estradiol, and 16-ketoestradiol accounting for 60% to 75% of total urinary EM. Within each group, interindividual differences in absolute concentrations were consistently high; the range was 10- to 100-fold for nearly all EM.Conclusion: Our high-performance liquid chromatography-tandem mass spectrometry method for measuring 15 urinary EM is highly reproducible, and the range of EM concentrations in each menstrual/sex group is quite large relative to assay variability. Whether these patterns persist in blood and target tissues awaits further development and application of this method. (Cancer Epidemiol Biomarkers Prev 2008;17(12):3411–8)