Heart rate variability in subjects with different respiratory rates

The variability of the cardiac rhythm was studied in males with different initial respiratory rates. At rest and during voluntarily controlled breathing, subjects with medium respiratory rates were found to have a less variable heart rate than their counterparts with low or high respiratory rates.     

Collagen type I fibril packing in vivo and in vitro

Reviewed are works concerning the mechanisms of collagen (type I) fibril packing and the influence of macromolecular structure and physicochemical parameters of the medium on the process.     

A Temporally Explicit Production Efficiency Model for Fuel Load Allocation in Southern Africa

Abstract We present a regional fuel load model (1 km² spatial resolution) applied in the southern African savanna region. The model is based on a patch-scale production efficiency model (PEM) scaled up to the regional level using empirical relationships between patch-scale behavior and multi-source remote sensing data (spatio-temporal variability of vegetation and climatic variables). The model requires the spatial distribution of woody vegetation cover, which is used to determine separate respiration rates for tree and grass. Net primary production, grass and tree leaf death, and herbivory are also taken into account in this mechanistic modeling approach. The fuel load model has been calibrated and validated from independent measurements taken from savanna vegetation in Africa southward from the equator. A sensitivity analysis on the effect of climate variables (incoming radiation, air temperature, and precipitation) has been conducted to demonstrate the strong role that water availability has in determining productivity and subsequent fuel load over the southern African region. The model performance has been tested in four different areas representative of a regional increasing rainfall gradient—Etosha National Park, Namibia, Mongu and Kasama, Zambia, as well as in Kruger National Park, South Africa. Within each area, we analyze model output from three different magnitudes of canopy coverage (<5, 30, and 50%). We find that fuel load ranges predicted by the model are globally in agreement with field measurements for the same year. High rainfall sustains green herbaceous production late in the dry season and delays tree leaf litter production. Effect of water on production varies across the rainfall gradient with delayed start of green material production in more arid regions.     

Isoforms of myosin and actin in human, monkey and rat myometrium. Comparison of pregnant and non-pregnant uterus proteins

Using several electrophoretic procedures, we have compared the forms of myosin and actin in pregnant and non-pregnant uterus of woman, monkey (Macaca fascicularis) and rat. On non-dissociating gels, native myosin of the three species migrates as a single band, of identical mobility independently of the physiological state. Remigration of this band in dissociating conditions shows that it is constituted of two heavy chains of respectively 201 kDa and 205 kDa; the relative proportions of these two bands are different for the three animal species but do not vary during pregnancy. Using two-dimensional gel electrophoresis, we found that the 17-kDa light chain of purified uterus myosin exists under two isoelectric forms, the more acidic one becoming progressively predominant at the end of pregnancy in the human as in the monkey uterus, while we observed no changes in the rat. In two-dimensional gel electrophoresis, actin of human, monkey and rat uterus is present under three isoforms, the most basic one (the gamma form) increasing early in pregnancy in the two primate species but being always the most abundant form in the rat. The ATPase activity of human uterus myosin was found to be similar for the protein extracted from both pregnant and non-pregnant uterus. The changes observed in the 17-kDa light chain and in the actin isoforms might nevertheless participate in the modifications of contractility of the uterus during pregnancy of the primates.     

Slow Cortical Potentials Preceeding Visually Guided Saccades in Schizophrenics

The parameters of saccades and presaccadic slow potentials were studied in right-handed men with a dominant right eye, including 19 schizophrenics and 12 healthy subjects. For visual stimulation, three light-emitting diodes were used, which were located in the center of the visual field (the central fixation stimulus) and 10° to the right and left of it (peripheral stimuli). Two stimulation protocols were used: with a simultaneous switching off of the central fixation stimulus and switching on of the peripheral stimuli (test 1) and with an interstimulus gap of 200 ms (test 2). According to the latency, saccades were divided into anticipatory, express, and regular. Slow EEG potentials preceding regular saccades were analyzed. It was found that the proportion of anticipatory saccades is considerably higher than the normal value in schizophrenia. The analysis of the presaccadic potentials demonstrated a significant decrease in the amplitude of negative potentials in the vertex region at early stages of presaccadic preparation and its increase in the occipital region at late stages. Test 2 in the patients demonstrated an increase in the positivity focus in the frontal region of the right hemisphere. It was assumed that the alterations found in schizophrenia result from the deficit of frontal cortical fields.     

Influence of right atrial stretch on plasma renin activity in the conscious rat

Rats were prepared with inflatable balloons at the superior vena cava - right atrium junction. After recovery 1 week later, when blood was taken from conscious, normovolaemic animals plasma renin activity was found not to be influenced by right atrial stretch. Plasma renin activity was then measured in rats in which an extracellular fluid deficit had been produced by peritoneal dialysis against a hyperoncotic, isotonic solution. Although basal plasma renin activity was elevated (6.8 +/- 0.9 from 1.5 +/- 0.2 ng X mL X h, n = 19), no depression was observed in the experimental group after 15 or 90 min of balloon inflation. In rats pretreated with isoprenaline (10 micrograms/kg body wt.) plasma renin activity was also increased over basal levels, but again balloon inflation caused no reduction in plasma renin activity. It would appear that right atrial stretch has little, if any, influence on renin release in the conscious rat.     

Reconstructing labroid evolution with single-copy nuclear DNA.

Fifteen per cent of all living fishes are united in a single suborder (Labroidei) and display a dazzling array of behavioural and ecological traits. The labroids are considered monophyletic and members share a pharyngeal jaw apparatus (PJA) modified for crushing and processing prey. Outside of the explicitly functional PJA, there is no corroborative evidence for a monophyletic Labroidei. Here, we report the first molecular phylogenetic analysis of the suborder. Contrary to morphology-based phylogenies, our single-copy nuclear DNA data do not support labroid families as a natural group. Our data indicate that pharyngognathy has evolved independently among labroid families and that characters of the PJA are not reliable markers of perciform evolution. This work ''crushes'' conventional views of fish phylogeny and should engender novel concepts of piscine life history evolution.     

Diminished Reovirus Capsid Stability Alters Disease Pathogenesis and Littermate Transmission

Reovirus is a nonenveloped mammalian virus that provides a useful model system for studies of viral infections in the young. Following internalization into host cells, the outermost capsid of reovirus virions is removed by endosomal cathepsin proteases. Determinants of capsid disassembly kinetics reside in the viral σ3 protein. However, the contribution of capsid stability to reovirus-induced disease is unknown. In this study, we found that mice inoculated intramuscularly with a serotype 3 reovirus containing σ3-Y354H, a mutation that reduces viral capsid stability, succumbed at a higher rate than those infected with wild-type virus. At early times after inoculation, σ3-Y354H virus reached higher titers than wild-type virus at several sites within the host. Animals inoculated perorally with a serotype 1 reassortant reovirus containing σ3-Y354H developed exaggerated myocarditis accompanied by elaboration of pro-inflammatory cytokines. Surprisingly, unchallenged littermates of mice infected with σ3-Y354H virus displayed higher titers in the intestine, heart, and brain than littermates of mice inoculated with wild-type virus. Together, these findings suggest that diminished capsid stability enhances reovirus replication, dissemination, lethality, and host-to-host spread, establishing a new virulence determinant for nonenveloped viruses.     

Hierarchy of effects of the MHC and T cell receptor beta-chain genes in susceptibility to Theiler's murine encephalomyelitis virus-induced demyelinating disease.

Intracerebral inoculation of susceptible mice with Theiler's murine encephalomyelitis virus induces a demyelinating disease that is similar to human multiple sclerosis. This murine model for human multiple sclerosis is apparently immune-mediated and the genes involved in the immune response influence the outcome of disease susceptibility as observed with human multiple sclerosis. These genes include the MHC and TCR genes. However, the functional relationships among these genes on the disease susceptibility has not yet been studied. In this study, we demonstrate that the effect of the H-2s genotype from susceptible SJL/J mice overrides the resistant effect of the BALB/c TCR beta-chain gene in CXJ recombinant-inbred and BALB.S congenic mice. These results strongly suggest the presence of a hierarchy of genes involved in the immune response in Theiler's murine encephalomyelitis virus-induced demyelinating disease.