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Selected AbstractsInfluence of neurohumoral blockade on heart rate and blood pressure responses to haemorrhage in isoflurane anaesthetized ratsACTA PHYSIOLOGICA, Issue 3 2000UllmanArticle first published online: 24 DEC 200 Four groups of Sprague,Dawley rats were anaesthetized with isoflurane (ISO) (1.7% end-tidal concentration) in 40% oxygen, and mechanically ventilated. The animals were bled 15 mL kg,1 b.w. from the femoral vein over 10 min, followed by an observation period of 30 min. Ten minutes before haemorrhage each group of animals was pre-treated with intravenous injection/infusion of either: isotonic saline (Group B; CON; n=7), vasopressin V1 -receptor antagonist [d(CH2)5Tyr(Me)AVP; 10 ,g kg,1] (Group C; AVP-a; n=7), the non-selective angiotensin II receptor antagonist saralasin (10 ,g kg,1 min,1) (Group D; SAR; n=7) or hexamethonium (10 mg kg,1) (Group E; HEX; n=7). A separate group of conscious animals were pre-treated with isotonic NaCl and subjected to the same haemorrhage protocol (Group A; AW; n=7). Mean arterial pressure (MAP), heart rate (HR) and blood gases were observed during the experiments. Only pre-treatment with SAR and HEX reduced MAP significantly. The pre-haemorrhage HR was only affected by HEX, which caused a reduction by 17%. The HR was significantly lower at the end of haemorrhage compared with pre-haemorrhage levels in all groups except that group treated with HEX. In that group the HR changed in the opposite direction. The ability to maintain MAP during haemorrhage, and the post-haemorrhage period, was significantly impaired in the groups treated with AVP-a, SAR or HEX compared with the group receiving NaCl. It is concluded that autonomic nervous activity is of major importance for the maintenance of MAP during isoflurane anaesthesia, whereas circulating angiotensin II and vasopressin levels contribute to a much smaller degree in this regard. General anaesthesia in combination with different degrees of neurohumoral blockade impairs the haemodynamic responses to blood loss, seen in conscious individuals. The impairment involves both the early and late phases during haemorrhage, as well as the post-bleeding recovery period. All three neurohumoral systems (autonomic nervous activity, angiotensin II and vasopressin) are of importance for regulating MAP during and after haemorrhage, although the autonomic nervous outflow appears to contribute to a larger extent. [source] Expression of c-Met in developing rat hippocampus: evidence for HGF as a neurotrophic factor for calbindin D-expressing neuronsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2000Laura Korhonen Abstract Hepatocyte growth factor-scatter factor (HGF) is expressed in different parts of the nervous system, and has been shown to exhibit neurotrophic activity. Here we show that c-Met, the receptor for HGF, is expressed in developing rat hippocampus, with the highest levels during the first postnatal weeks. To study the function of HGF, hippocampal neurons were prepared from embryonic rats and treated with different HGF concentrations. In these cultures, HGF increased the number of neurons expressing the 28-kDa calcium-binding protein (calbindin D) in a dose-dependent manner. The effect of HGF was larger than that observed with either brain-derived neurotrophic factor (BDNF) or neurotrophin-3 (NT-3), and cotreatment of the cultures with HGF and the neurotrophins was additive with respect to calbindin D neurons. Besides affecting the number of neurons, HGF significantly increased the degree of sprouting of calbindin D-positive neurons, suggesting an influence on neuronal maturation. BDNF and NT-3 stimulated neurite outgrowth of calbindin D neurons to a much smaller degree. In contrast to calbindin D neurons, HGF did not significantly increase the number of neurons immunoreactive with the neurotransmitter ,-aminobutyric acid (GABA) in the hippocampal cultures. Immunohistochemical studies showed that c-Met-, calbindin D- and HGF-immunoreactive cells are all present in the dentate gyrus and partly colocalize within neurons. These results show that HGF acts on calbindin D-containing hippocampal neurons and increases their neurite outgrowth, suggesting that HGF plays an important role for the maturation and function of these neurons in the hippocampus. [source] A practical determination strategy of optimal threshold parameter for matrix compression in wavelet BEMINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 2 2003Kazuhiro Koro Abstract A practical strategy is developed to determine the optimal threshold parameter for wavelet-based boundary element (BE) analysis. The optimal parameter is determined so that the amount of storage (and computational work) is minimized without reducing the accuracy of the BE solution. In the present study, the Beylkin-type truncation scheme is used in the matrix assembly. To avoid unnecessary integration concerning the truncated entries of a coefficient matrix, a priori estimation of the matrix entries is introduced and thus the truncated entries are determined twice: before and after matrix assembly. The optimal threshold parameter is set based on the equilibrium of the truncation and discretization errors. These errors are estimated in the residual sense. For Laplace problems the discretization error is, in particular, indicated with the potential's contribution ,c, to the residual norm ,R, used in error estimation for mesh adaptation. Since the normalized residual norm ,c,/,u, (u: the potential components of BE solution) cannot be computed without main BE analysis, the discretization error is estimated by the approximate expression constructed through subsidiary BE calculation with smaller degree of freedom (DOF). The matrix compression using the proposed optimal threshold parameter enables us to generate a sparse matrix with O(N1+,) (0,,<1) non-zero entries. Although the quasi-optimal memory requirements and complexity are not attained, the compression rate of a few per cent can be achieved for N,1000. Copyright © 2003 John Wiley & Sons, Ltd. [source] The allometric pattern of sexually size dimorphic feather ornaments and factors affecting allometryJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 7 2009J. J. CUERVO Abstract The static allometry of secondary sexual characters is currently subject to debate. While some studies suggest an almost universal positive allometry for such traits, but isometry or negative allometry for nonornamental traits, other studies maintain that any kind of allometric pattern is possible. Therefore, we investigated the allometry of sexually size dimorphic feather ornaments in 67 species of birds. We also studied the allometry of female feathers homologous to male ornaments (female ornaments in the following) and ordinary nonsexual traits. Allometries were estimated as reduced major axis slopes of trait length on tarsus length. Ornamental feathers showed positive allometric slopes in both sexes, although that was not a peculiarity for ornamental feathers, because nonsexual tail feathers also showed positive allometry. Migration distance (in males) and relative size of the tail ornament (in females) tended to be negatively related to the allometric slope of tail feather ornaments, although these results were not conclusive. Finally, we found an association between mating system and allometry of tail feather ornaments, with species with more intense sexual selection showing a smaller degree of allometry of tail ornaments. This study is consistent with theoretical models that predict no specific kind of allometric pattern for sexual and nonsexual characters. [source] Effects of temperature on larval fish swimming performance: the importance of physics to physiologyJOURNAL OF FISH BIOLOGY, Issue 4 2002I. Hunt von Herbing Temperature influences both the physiology offish larvae and the physics of the flow conditions under which they swim. For small larvae in low Reynolds number (Re) hydrodynamic environments dominated by frictional drag, temperature-induced changes in the physics of water flow have the greatest effect on swimming performance. For larger larvae, in higher Re environments, temperature-induced changes in physiology become more important as larvae swim faster and changes in swimming patterns and mechanics occur. Physiological rates at different temperatures have been quantified using Q10s with the assumption that temperature only affected physiological variables. Consequently, Q10s that did not consider temperature-induced changes in viscosity overestimated the effect of temperature on physiology by 58% and 56% in cold-water herring and cod larvae respectively. In contrast, in warm-water Danube bleak larvae, Q10s overestimated temperature-induced effects on physiology by only 5,7%. This may be because in warm water, temperature-induced changes affect viscosity to a smaller degree than in cold water. Temperature also affects muscle contractility and efficiency and at high swimming velocities, efficiency decreases more rapidly in cold-exposed than in warm-exposed muscle fibres. Further experiments are needed to determine whether temperature acts differently on swimming metabolism in different thermal environments. While hydrodynamic factors appear to be very important to larval fish swimming performance in cold water, they appear to lose importance in warm water where temperature effects on physiology dominate. This may suggest that major differences exist among locomotory capacities of larval fish that inhabit cold, temperate waters compared to those that live in warm tropical waters. It is possible that fish larvae may have developed strategies that affect dispersal and recruitment in different aquatic habitats in order to cope not only with temperature-induced physiological challenges, but physical challenges as well. [source] Analysis of DIGE data using a linear mixed model allowing for protein-specific dye effectsPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 23 2007Morten Krogh Dr. Abstract Differential in-gel electrophoresis (DIGE) experiments allow three protein samples to be run per gel. The three samples are labeled with the spectrally resolvable fluorescent dyes, Cy2, Cy3, and Cy5, respectively. Here, we show that protein-specific dye effects exist, and we present a linear mixed model for analysis of DIGE data which takes dye effects into account. A Java implementation of the model, called DIGEanalyzer, is freely available at http://bioinfo.thep.lu.se/digeanalyzer.html. Three DIGE experiments from our laboratory, with 173, 64, and 24 gels, respectively, were used to quantify and verify the dye effects. DeCyder 5.0 and 6.5 were used for spot detection and matching. The fractions of proteins with a statistically significant (0.001 level) dye effect were 19, 34, and 23%, respectively. The fractions of proteins with a dye effect above 1.4-fold change were 1, 4, and 6%, respectively. The median magnitude of the dye effect was 1.07-fold change for Cy5 versus Cy3 and 1.16-fold change for Cy3 versus Cy2. The maximal dye effect was a seven-fold change. The dye effects of spots corresponding to the same protein tend to be similar within each of the three experiments, and to a smaller degree across experiments. [source] Vasomotor sympathetic neural control is maintained during sustained upright posture in humansTHE JOURNAL OF PHYSIOLOGY, Issue 2 2006Qi Fu Vasomotor sympathetic activity plays an important role in arterial pressure maintenance via the baroreflex during acute orthostasis in humans. If orthostasis is prolonged, blood pressure may be supported additionally by humoral factors with a possible reduction in sympathetic baroreflex sensitivity. We tested the hypothesis that baroreflex control of muscle sympathetic nerve activity (MSNA) decreases during prolonged upright posture. MSNA and haemodynamics were measured supine and during 45 min 60 deg upright tilt in 13 healthy individuals. Sympathetic baroreflex sensitivity was quantified using the slope of the linear correlation between MSNA and diastolic pressure during spontaneous breathing. It was further assessed as the relationship between MSNA and stroke volume, with stroke volume derived from cardiac output (C2H2 rebreathing) and heart rate. Total peripheral resistance was calculated from mean arterial pressure and cardiac output. We found that MSNA increased from supine to upright (17 ± 8 (s.d.) versus 38 ± 12 bursts min,1; P < 0.01), and continued to increase to a smaller degree during sustained tilt (39 ± 11, 41 ± 12, 43 ± 13 and 46 ± 15 bursts min,1 after 10, 20, 30 and 45 min of tilt; between treatments P < 0.01). Sympathetic baroreflex sensitivity increased from supine to upright (,292 ± 180 versus,718 ± 362 units beat,1 mmHg,1; P < 0.01), but remained unchanged as tilting continued (,611 ± 342 and ,521 ± 221 units beat,1 mmHg,1 after 20 and 45 min of tilt; P= 0.49). For each subject, changes in MSNA were associated with changes in stroke volume (r= 0.88 ± 0.13, P < 0.05), while total peripheral resistance was related to MSNA during 45 min upright tilt (r= 0.82 ± 0.15, P < 0.05). These results suggest that the vasoconstriction initiated by sympathetic adrenergic nerves is maintained by ongoing sympathetic activation during sustained (i.e. 45 min) orthostasis without obvious changes in vasomotor sympathetic neural control. [source] | ||||||||||