Puromycin enhances 20-hydroxyecdysone-induced protein synthesis in wing discs of Drosophila melanogaster

The effect of cycloheximide and puromycin on 20-hydroxyecdysone-induced protein synthesis in wing discs of Drosophila melanogaster has been studied by one-dimensional and two-dimensional SDS polyacrylamide electrophoresis. It is found that puromycin, but not cycloheximide, when applied simultaneously with the hormone enhanced the hormone-induced synthesis of the early and late proteins. However, when puromycin was applied after hormone treatment, only the late proteins were induced. The possible implication of these observations is discussed.     

Localization of ornithine decarboxylase in the chick embryo during organogenesis

Summary The localization of ornithine decarboxylase (ODC), a key enzyme in polyamine biosynthesis and thus in cell growth, was determined in the 4.5-day-old chick embryo, using two independent methods of analysis. ODC protein was identified by indirect immunofluorescence with a monospecific ODC antibody, and catalytically active ODC was identified by autoradiography with -(5-³H) difluoromethylornithine. Both methods revealed a basically similar distribution of ODC within the embryo. Among the organs, the brain exhibited the highest ODC levels. ODC levels were also high in spinal cord, mesonephric tubules and heart. Similar levels, but confined to limited areas, were found in liver tissue, head mesenchyme, and the oral and pharyngeal regions. Organs that exhibited high ODC levels are all engaged in rapid growth, as well as in extensive tissue remodeling and differentiation.     

Crystal structure analysis of an A-DNA fragment at 1.8 A resolution: d(GCCCGGGC).

Single crystals of the self-complementary octadeoxyribonucleotide d(GCCCGGGC) have been analysed by X-ray diffraction methods at a resolution of 1.8 A. The tetragonal unit cell of space group P4(3)2(1)2 has dimensions of a = 43.25 A and c = 24.61 A and contains eight strands of the oligonucleotide. The structure was refined by standard crystallographic techniques to an R factor of 17.1% using 1359 3 sigma structure factor observations. Two strands of the oligonucleotide are related by the crystallographic dyad axis to form a DNA helix in the A conformation. The d(GCCCGGGC) helix is characterized by a wide open major groove, a near perpendicular orientation of base pairs to the helix axis and an unusually small average helix twist angle of 31.3 degrees indicating a slightly underwound helix with 11.5 base pairs per turn. Extensive cross-strand stacking between guanine bases at the central cytosine-guanine step is made possible by a number of local conformational adjustments including a fully extended sugar-phosphate backbone of the central guanosine nucleotide.     

Comparison of population dynamics between slow- and fast-growing strains of the rotifer Brachionus calyciflorus pallas in continuous culture

Summary The population dynamics of a slow- and a fast-growing strain of the rotifer Brachionus calyciflorus are compared. Rotifers were grown in steady-states, at various specific growth rates (), in both two-stage chemostat and turbidostat cultures on the green alga Chlorella pyrenoidosa. Population variables, including specific ingestion (I), loss (L) and filtration (F) rates, yield (Y), production (P) and half-saturation coefficient of growth (K _g), were calculated using a growth model based on saturation kinetics. I, L, F and K _g were shown to be higher and Y and P lower for the fast-growing strain. Differences between the two strains with regard to these variables may represent tradeoffs associated with the faster potential growth rate. Steady-state relationships between these values and for the fast-growing strain, however, deviated from model predictions which suggest a possible shift from carbon to non-carbon growth limitation.     

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Macroaggregated calcifications in cancer of the breast

Breast cancer is characterized by the presence of multiple aggregated microcalcinates. However, the authors managed to detect 6 cases of breast cancer with macroaggregate calcifications, of which 3 were not adequately imaged on mammograms. Morphological investigations in all cases have shown that macroaggregate calcifications that are typical of benign lesions, are also detectable in breast cancer. The absence of an image of calcification on mammograms is probably accountable for by its various density.     

Periplasmic secretion of human growth hormone by Escherichia coli

The gene coding for human growth hormone (hGH) was fused to the coding sequence for the signal peptide of a secreted Escherichia coli protein. STII heat-stable enterotoxin. This hybrid gene was expressed in E. coli. The signal peptide is properly processed and hGH is secreted in to the periplasmic space. In E. coli, some of the material made is proteolytically clipped or deamidated. The effect of culture conditions on the expression and secretion of hGH was studied and several important parameters were identified, including culture temperature and duration, cultivation pH, K+ levels, plasmid structure, and nutrient supplements. Alteration of culture conditions significantly improves the recovery yield and product quality of human growth hormone.     

Interrelationships among various measures of upper body strength assessed by different contraction modes Evidence for a general strength component

Two studies were conducted in 83 college men to determine the degree of generality of individual differences in upper body muscular strength assessed by different testing modes. In study 1 (N = 43), correlations were computed between four measures of upper body strength using the bench press movement, maximal isokinetic (0.09 rad.s-1), maximal fast (0.126 m.s-1) and slow (0.037 m.s-1) hydraulic, and one repetition maximum (1-RM) free weight bench press (BP). Compared to free weight BP, maximal strength during isokinetic and slow hydraulic BP was approximately 29% and approximately 8% larger, and fast hydraulic BP strength was approximately 63% lower (p less than 0.05). Simple linear regression of isokinetic BP on 1-RM BP yielded r = 0.79, error of prediction (SE) = 12%, and generality = 81%. The corresponding averaged values for the regression of slow and fast hydraulic BP on free weight 1-RM BP were r = 0.77, SE = 13.5%, and generality = 84%. In Study 2 (N = 40), testing included maximal isokinetic concentric and eccentric arm flexion and extension at 0.524, 1.570, and 2.094 rad.s-1. The ratio of concentric to eccentric torque at the 3 speeds averaged 0.68 (flexion) and 0.70 (extension), and eccentric torques were 32% and 30% greater than concentric torques (p less than 0.05). The linear regression between concentric vs. eccentric flexion and extension torques at the three velocities yielded an average r = 0.80, SE = 13.7%, and generality = 73%.(ABSTRACT TRUNCATED AT 250 WORDS)