A 1H-NMR longitudinal relaxation study of the interaction between cytochrome c and cytochrome c oxidase

The interaction between the oxidized forms of cytochrome c and cytochrome c oxidase (EC 1.9.3.1) has been investigated by 1H-NMR longitudinal relaxation measurements. It is found that relaxation of methyl groups on the heme ring of cytochrome c markedly deviates from a simple exponential behavior in the presence of small amounts of cytochrome oxidase. A comparison with the relaxation behavior of cytochrome c modified by 4-carboxy-3,5-dinitrophenyl at Lys-13 shows that the oxidase induces a conformation in native cytochrome c that is closely related to that of the derivative. It is suggested that this change in conformation consists of a rupture of the salt bridge between Lys-13 and Glu-90 and a concomitant perturbation of the methionine ligand.     

Cortisol decreases the cellular concentration of translatable procollagen mRNA species in cultured human skin fibroblasts

The effect of cortisol on the cellular concentration of translatable procollagen mRNAs was studied in cultured human skin fibroblasts. Cortisol selectively decreased the amount of procollagen mRNAs, in comparison to the total mRNA activity, when the cells were grown in enriched medium conditions, i.e., with 10% newborn calf serum. The selective decrease was first observed after 6 h exposure to 1 microM cortisol. In depleted medium conditions, i.e., with 2% newborn calf serum, the initial response was a stimulatory one, followed after about 12 h by a decrease in the procollagen mRNA activity. The results suggest that the selective inhibitory effect of cortisol on the cellular concentration of translatable procollagen mRNA species needs an optimal serum concentration. Furthermore, the results give support to the hypothesis that the decrease in the procollagen mRNA concentration after cortisol administration is a secondary response, preceded by the induction of some intracellular regulation system.     

The comparison of seed protein patterns within the genusArachis by polyacrylamide gel electrophoresis

The seed protein patterns of 12Arachis species were compared by polyacrylamide gel electrophoresis (PAGE), similarities between patterns were measured by the Jaccard index. Results obtained confirm the close relationships established between members of the genus on morphological grounds and support the more recent classification schemes.A. villosa andA. correntina could well be regarded as distinct species on grounds of protein differences whileA. macedoi andA. villosulicarpa (although members of the same section, Extranervosae) show considerable differentiation of their protein patterns. Surprisingly, the formA. ×batizogaea showed less similarity in protein pattern to those of its parental species than might have been expected. The principle value of seed protein pattern data appears to be in distinguishing species within sections.     

Electro-optical measurements on aqueous suspension of purple membrane from Halobacterium halobium

The permanent dipole moment, polarizability, and the retinal angle of Halobacterium halobium purple membranes were determined at different pH values. All of the parameters have a maximum between pH 5 and 6. There is a reversal in the direction of the permanent dipole moment near pH 5. The value of permanent dipole moment was determined to be 60 D/protein at pH 6.6, and the value obtained for polarizability was 3 X 10(-28) Fm2/membrane fragment. The retinal angle of all-trans retinal was 0.8 degrees smaller than that of the 13-cis conformation.     

A new function for overall optimization of yeast production

The influence of several operating variables on the productivity and nutritional quality of Candida utilis under carbon-limited growth conditions was studied. Four responses were analyzed: biomass yield (Y), in vitro dry matter digestibility (d), nucleic acid cotents, and protein content (P). Three operating variables were studied: dilution rate, temperature, and carbon-nitrogen ratio in the growth medium. Correlation describing the influence of operating variables on the studied response parameters were developed. From these correlations response surfaces were drawn. A new function, alpha = PdY, is proposed as a more comprehensive criterion for selecting the optimal conditions under the constraint of satisfying multiple objectives. It is demonstrated to be superior to the yield coefficient alone in this respect, since it accounts for factors that are important to the nutritional aspects of the process.     

The development of the early atrioventricular conduction system in the embryonic heart

Recent electrophysiological evidence indicates that periodic spontaneous depolarizations occur in the primordial heart of the bird (and presumably mammal) even before the myocardial cells can contract, and these are initiated in the primordial sinoatrial region. As contractions are generated, these then establish a peristaltic wave. From that time on, during ontogenesis, the contractile sequence follows a regular pattern of development. As chambers form they contract sequentially in the direction of blood flow, even though, in the twisted configuration, myocardial continuities suggest the possibility of short-circuiting the electrical conduction pathways from atrium to bulbus. This implies that, even at these early stages, the electrical properties of the myocardium are not isotropic, and that specialized conduction pathways must exist. To the present time, electrophysiological techniques have limited the direct evidence that can be obtained on these delicate electrically specialized pathways. However, microscopical techniques have permitted studies on the morphological development of the tissue and of the cells in the various regions of the myocardium. The present paper traces the development of cell morphology in these regions, including the development of structural nodes and proximal ventricular fibre pathways, and from these observations, the manner in which the electrical conduction pathways are believed to develop is suggested.