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.     

Peritonitis induces the synthesis of 1α,25-dihydroxyvitamin D3 in macrophages from CAPD patients

Metabolism of 25-[3H]hydroxyvitamin D3 was studied in peritoneal macrophages from renal failure patients on continuous ambulatory peritoneal dialysis (CAPD). Cells from 5 out of 8 patients with a history of peritonitis produced significant amounts of a metabolite chromatographically identical to 1 alpha,25(OH)2D3; but none was produced by cells from non-infected patients. The evidence strongly suggests that peritoneal macrophages stimulated by infection can metabolise 25OHD3 to the active vitamin D3 metabolite, 1 alpha,25(OH)2D3, when maintained in short-term primary culture.     

Primary hyperparathyroidism: the case for medical management.

Thirty two patients with primary hyperparathyroidism were followed up medically for a mean of 4.2 years. One patient had an operation because of a rise in plasma calcium concentration. There was no significant change in the mean plasma calcium and creatinine concentrations or in blood pressure during the period of follow up. The progress of these patients who were managed medically was compared with that of a group of 60 patients who had had successful operations for primary hyperparathyroidism. There was no significant change in mean plasma creatinine concentration or in blood pressure in the group who had had operations during a mean follow up period of 5.9 years. The natural history of mild asymptomatic hyperparathyroidism is probably different from and better than that of the type of hyperparathyroidism that was usually seen before the advent of routine chemical screening. It is suggested that patients over the age of 60 with mild asymptomatic hyperparathyroidism, and perhaps even younger patients, may not require operation.     

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.      

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.      

Masting,seed dispersal and seed predation in the cycad Macrozamia communis

Summary Little is known about the adaptive value of mast seeding, a common phenomenon in temperate trees and shrubs. Masting is likely to affect both seed dispersal and seed predation. In systems where similar taxa of animals are involved in these two processes, the consequences of mast seeding are likely to be particularly complicated. This study examined the effects of mast seeding in a cycad, Macrozamia communis, on the dispersal of seeds, the pattern of dispersion of seeds and post-dispersal predation on seeds. Dispersal of seeds by possums was poorer from source plants in a masting population than from source plants in an adjacent, non-masting population. This resulted in fewer seeds per seeding female plant in the masting plot being dispersed to favourable sites. We conclude that this is caused by the feeding behaviour and movements of possums in the masting site. The abundance of seeds in this site did not satiate the post-dispersal predators, native rats. In fact, more seeds in this site were eaten than in the nonmasting site. We suggest that the mast seeding observed in M. communis may not be adaptive, but is more likely a consequence of other factors which synchromize flowering within local populations.     

Some studies on catalysis by lysozyme

The preparation of some aryl β-glycosides of β-1, 4-linked oligosaccharides of (GlcNAc)_n, n = 2, 3, 4, is described. These compounds were tested as substrates for lysozyme from hens' egg white. The best of them, (GlcNAc)₄-3,4-DNP, had a value of k_cat/K_m which was about one-nintieth that for the hydrolysis of (GlcNAc)₆. The pH dependence of k_cat and k_cat/K_m for the hydrolysis of (GlcNAc)₄-3,4-DNP was similar to that for (GlcNAc)₆. (GlcNAc)₄-3,4-DNP was also a substrate for human lysozyme and lysozyme from ducks' egg white (II and III). An impure sample of (GlcNAc)₂F was prepared and this was hydrolyzed much more rapidly than (GlcNAc)₂-2,4-DNP by lysozyme. Compounds of type (GlcNAc)_n−1(XylNAc)Ar, where n = 2, 3, 4, were prepared and found not to be substrates for lysozyme. In the presence of (GlcNAc)₄ or (GlcNAc)₅, lysozyme-induced hydrolyses of (GlcNAc)-3,4-DNP and (Glc)-3,4-DNP were observed but not of (XylNAc)-3,4-DNP, (6-deoxy-GlcNAc)-3,4-DNP, (6-F-GlcNAc)-3,4-DNP, and (6-Cl-GlcNAc)-3,4-DNP. The significance of these results is discussed.