Beta-adrenoceptors in human airway tissue: relationship between functional responsiveness and receptor number.

Functional organ bath experiments and radiolabelled ligand binding studies were used to investigate the relationship between beta-adrenoceptor-mediated relaxation and the total number of beta-adrenoceptors in human lung parenchymal tissue and bronchial tissue. Sensitivity to the beta-adrenoceptor agonist isoprenaline (pD2) varied almost 10-fold (pD2 values 6.00 to 6.85) for lung parenchymal preparations and 35-fold for bronchial preparations (pD2 values 6.16 to 7.67) between patients. The total number of [3H] DHA labelled beta-adrenoceptors (Bmax) varied almost 6-fold for lung parenchymal membrane preparations (Bmax 164 to 936 fmol/mg protein) and less than 2-fold for bronchial tissue membrane preparations (Bmax 188 to 342 fmol/mg protein) between patients. Comparison of sensitivity to isoprenaline and beta-adrenoceptor number for lung parenchymal tissue from the same patient demonstrated a negative correlation (r = -0.80 [95% confidence intervals: -0.13, -0.96], 6 d.f., P less than 0.05), suggesting that beta-adrenoceptor-mediated sensitivity of lung parenchymal tissue is inversely related to the number of beta-adrenoceptors. However, there was an absence of correlation between sensitivity to isoprenaline and beta-adrenoceptor number in bronchial tissue from the same patient. Thus, the findings of the present study do not support the possibility of a direct relationship between the beta-adrenoceptor-mediated responsiveness and the beta-adrenoceptor number of human airway preparations.     

Phytase supplementation increases bone mineral density,lean body mass and voluntary physical activity in rats fed a low-zinc diet

Phytic acid forms insoluble complexes with nutritionally essential minerals, including zinc (Zn). Animal studies show that addition of microbial phytase (P) to low-Zn diets improves Zn status and bone strength. The present study determined the effects of phytase supplementation on bone mineral density (BMD), body composition and voluntary running activity of male rats fed a high phytic acid, low-Zn diet. In a factorial design, rats were assigned to ZnLO (5 mg/kg diet), ZnLO+P (ZnLO diet with 1500 U phytase/kg) or ZnAD (30 mg/kg diet) groups and were divided into voluntary exercise (EX) or sedentary (SED) groups, for 9 weeks. SED rats were significantly heavier from the second week, and no catch-up growth occurred in EX rats. Feed intakes were not different between groups throughout the study. ZnLO animals had decreased food efficiency ratios compared to both phytase-supplemented (ZnLO+P) and Zn-adequate (ZnAD) animals (P<.01 compared to ZnLO). The ZnLO+P and ZnAD rats ran 56–75 km more total distance than ZnLO rats (P<.05), with the ZnLO+P rats running more kilometers per week than the ZnLO rats by Week 6. In vivo DEXA analyses indicate that rats fed phytase-supplemented diets had higher lean body mass (LBM) than those fed ZnLO diets; and that rats fed the Zn-adequate diets had the highest LBM. Body fat (%) was significantly lower in EX rats and was both Zn- and phytase insensitive. Rats fed phytase-supplemented diets had higher bone mineral content (BMC), bone area (BA) and BMD than rats fed ZnLO diets; and in rats fed ZnAD diets these indices were the highest. The dietary effects on BMC, BA and BMD were independent of activity level.We conclude that consuming supplemental dietary phytase or dietary Zn additively enhances Zn status to increase BMD, LBM and voluntary physical activity in rats fed a low-Zn diet. While the findings confirm that bone health is vulnerable to disruption by moderate Zn deficiency in rats, this new data suggests that if dietary Zn is limiting, supplemental phytase may have beneficial effects on LBM and performance activity.     

Effects of intima stiffness and plaque morphology on peak cap stress

Background  

Rupture of the cap of a vulnerable plaque present in a coronary vessel may cause myocardial infarction and death. Cap rupture occurs when the peak cap stress exceeds the cap strength. The mechanical stress within a cap depends on the plaque morphology and the material characteristics of the plaque components. A parametric study was conducted to assess the effect of intima stiffness and plaque morphology on peak cap stress.     

Simulation of stent deployment in a realistic human coronary artery

Background  

The process of restenosis after a stenting procedure is related to local biomechanical environment. Arterial wall stresses caused by the interaction of the stent with the vascular wall and possibly stress induced stent strut fracture are two important parameters. The knowledge of these parameters after stent deployment in a patient derived 3D reconstruction of a diseased coronary artery might give insights in the understanding of the process of restenosis.     

Microsatellite evolution in congeneric mammals: domestic and bighorn sheep

We compared genotypes at eight (AC)n microsatellite loci in domestic sheep (Ovis aries) and wild Rocky Mountain bighorn sheep (O. canadensis). The domestic sheep had greater genetic variation, higher allele-size variances, and larger allele sizes than the wild sheep. Accumulating evidence from higher taxonomic comparisons shows that these parameters are biased if microsatellite loci are selected in one taxon and used in another. Our results demonstrate similar biases between congeneric species. We compared standard measures of genetic variation, differentiation, and distance within and between species (H, D, FST) to newer measures based on allele-size variance (SW, SB, RST). The size-based distances better detected species-level divergence, but standard measures better distinguished allopatric populations. Empirical calibration of these measures at the subspecies level is needed to establish their useful ranges.      

Effects of radiation on the environment: a need to question old paradigms and enhance collaboration among radiation biologists and radiation ecologists

A historical perspective is given of the current paradigm that does not explicitly protect nonhuman biota from radiation but instead relies on the concept that if dose limits are set to protect humans, then the environment is automatically protected as well. We summarize recent international questioning of this paradigm and briefly present three frameworks for protecting biota that are being considered by the U.S. Department of Energy, the Canadian Nuclear Safety Commission, and the International Commission on Radiological Protection. We point out a controversial component in each of the three frameworks and suggest topics that need additional research. We emphasize that to properly address radiation protection of the environment, we need to understand how effects are integrated across different levels of biological organization. We caution that the proposed use of molecular end points to estimate ecological risks from radioactive contamination is applicable only if we understand the extent of the impact that molecular damage has on individual organisms and populations of exposed biota. To accomplish the latter, enhanced collaborations are required among the traditionally separate disciplines of radiation biology and radiation ecology.     

Olfactory sensitivity in tsetse flies: a daily rhythm

The diurnal tsetse Glossina morsitans morsitans bites especially in early morning and late afternoon; around midday feeding is at a low. In laboratory apparatus that measures the amount of locomotion under constant conditions over the photophase, the flies display a similar patterning of activity levels. The profile of daily rhythms for G. morsitans reported in the literature includes a number of motor and sensory motor systems that fluctuate cophasically. Lacking is a study on the patterning of the senses' response levels. In this paper we present the first instance of a daily modulation in the sense of smell. We stimulated the antennae with concentration series of host-derived odours and measured the spiking rate of cells at different times during the photophase. The concentration-response curves suggest that the sensitivity of antennal olfactory cells flows in parallel with the other daily rhythms. This was also reflected in electroantennograms (EAGs). The electroantennography was extended to G. fuscipes fuscipes, whose level of spontaneous locomotor activity--instead of following a U- shaped pattern--rises gradually over the photophase. Again, the EAGs appeared to parallel the species' locomotor activity. What we believe happens is that the organism tones down the sensitivity of its odour receptors during periods of anticipated inactivity for reasons of economy.