Selective loss of uncoupling protein mRNA in brown adipose tissue on deacclimation of cold-acclimated mice

The time course of changes in the level of uncoupling protein mRNA when cold-acclimated mice were returned to a thermoneutral environment (33 degrees C) was examined using a cDNA probe. Upon deacclimation, there was a marked loss of uncoupling protein mRNA within 24 h, which precedes the loss of uncoupling protein from mitochondria. This loss of uncoupling protein mRNA was selective, since there was no change in the relative proportion of cytochrome c oxidase subunit IV mRNA or poly(A)+ RNA in total RNA. The results suggest that the decrease in the mitochondrial content of uncoupling protein during deacclimation is likely the result of turnover of existing protein, with very little replacement due to a lower level of its mRNA.     

Changes in the size of the myocardial damaged area in postischemic reperfusion

The changes in the size of the myocardial injury area during reperfusion after the coronary occlusion-induced ischemia lasting 30 minutes are phasic in nature. Until 3.5 h the injured area increases and after 23.5 h relatively diminishes. After a more prolonged ischemia such manifestations are either unmarked or absent. Ischemia lasting from 30 min to 4 hours followed by reperfusion, as compared with ischemia of the same duration without reperfusion, normally gives rise to the formation of an area of injury, which is less or occasionally equal in size. The data obtained and reported indicate that in the area of coronary occlusion there are groups of cardiomyocytes that differ as regards the resistance to ischemia.     

Fractionation and purification of DNA-methylases from Shigella sonnei 47

Possible applications of various column chromatography techniques and isoelectrofocusing for the study of DNA-methylases of Shigella sonnei 47 cells were analyzed. A simple, rapid and convenient procedure based on the use of cation-exchange chromatography was developed for obtaining a highly active total preparation of methylases. Affinity chromatography on heparin-Sepharose was shown to be a promising approach for separating methylases according to their specificity towards nitrous bases. Isoelectrofocusing was used to identify in Shigella sonnei 47 cells six individual methylating enzymes differing in their pI values. Under the stipulation that Shigella sonnei 47 DNA-methylases show a tendency to aggregate in the course of fractionation, column chromatography is of little or no use in isolating and purifying individual methylating enzymes of the given strain. The advantages of the isoelectrofocusing technique and its utility in the study of different molecular forms of site-specific enzymes are discussed.     

Partial trisomy 20p resulting from a recombination of a familial pericentric inversion

Summary Recombination of an inherited pericentric inversion of chromosome 20 has given rise to a child with partial trisomy 20p. To our knowledge no previous familial inversions of this chromosome have been described in the literature.     

Solid-state 15N NMR of oriented lipid bilayer bound gramicidin A'

Highly oriented samples of lipid and gramicidin A' (8:1 molar ratio) have been prepared with the samples extensively hydrated (approximately 70% water v/w). These preparations have been shown to be completely in a bilayer phase with a transition temperature of 28 degrees C, and evidence is presented indicating that the gramicidin is in the channel conformation. An estimate of the disorder in the alignment of the bilayers parallel with the glass plates used to align the bilayers can be made from the asymmetry of the nuclear magnetic resonances (NMR). Such an analysis indicates a maximal range of disorder of +/- 3 degrees. Uniformly 15N-labeled gramicidin has been biosynthesized by Bacillus brevis grown in a media containing 15N-labeled Escherichia coli cells as the only nitrogen source. When prepared with labeled gramicidin, the oriented samples result in high-resolution 15N NMR spectra showing 12 resonances for the 20 nitrogen sites of the polypeptide. The frequency of the three major multiple resonance peaks has been interpreted to yield the approximate orientation of the N-H bonds in the peptide linkages with respect to the magnetic field. These bond orientations are only partially consistent with the extant structural models of gramicidin.     

Influenza A Gradual and Epochal Evolution: Insights from Simple Models

The recurrence of influenza A epidemics has originally been explained by a “continuous antigenic drift” scenario. Recently, it has been shown that if genetic drift is gradual, the evolution of influenza A main antigen, the haemagglutinin, is punctuated. As a consequence, it has been suggested that influenza A dynamics at the population level should be approximated by a serial model. Here, simple models are used to test whether a serial model requires gradual antigenic drift within groups of strains with the same antigenic properties (antigenic clusters). We compare the effect of status based and history based frameworks and the influence of reduced susceptibility and infectivity assumptions on the transient dynamics of antigenic clusters. Our results reveal that the replacement of a resident antigenic cluster by a mutant cluster, as observed in data, is reproduced only by the status based model integrating the reduced infectivity assumption. This combination of assumptions is useful to overcome the otherwise extremely high model dimensionality of models incorporating many strains, but relies on a biological hypothesis not obviously satisfied. Our findings finally suggest the dynamical importance of gradual antigenic drift even in the presence of punctuated immune escape. A more regular renewal of susceptible pool than the one implemented in a serial model should be part of a minimal theory for influenza at the population level.