Enhancement of the horseradish peroxidase-catalyzed chemiluminescent oxidation of cyclic diacyl hydrazides by 6-hydroxybenzothiazoles

6-Hydroxybenzothiazole, 2-cyano-6-hydroxybenzothiazole, and 2-(6-hydroxy-2-benzothiazolyl)thiazole-4-carboxylic acid (dehydroluciferin) dramatically enhance light emission from the horseradish peroxidase conjugate catalyzed oxidation of luminol, isoluminol, N-(6-aminobutyl)-N-ethyl isoluminol, and 7-dimethylaminonaphthalene-1,2-dicarboxylic acid hydrazide by either peroxide or perborate. Light emission is enhanced by up to 1000-fold, which is an improvement over the enhancement previously observed using firefly luciferin (4,5-dihydro-2-(6-hydroxy-2-benzothiazolyl)thiazole-4-carboxylic acid). Enhancement is influenced by enhancer concentration and pH. Spectral scans of light emitted in enhanced and unenhanced reactions are similar, suggesting that aminophthalate products, and not the enhancers, are the emitters.     

Evidence that hypoxic pulmonary vascular remodeling in rats is polyamine dependent

This study tested the hypothesis that the polyamines, a family of low-molecular-weight organic cations with documented regulatory roles in cell growth and differentiation, are mediators of chronic hypoxia-induced pulmonary vascular remodeling. Relative to room air controls, chronically hypoxic animals (inspired O2 fraction = 0.1; 21 days) exhibited higher pulmonary arterial pressures (measured in room air), thicker medial layers in pulmonary arteries of 50-100 microns diam, increased hematocrits, and right ventricular hypertrophy. In addition, lung contents of the polyamines, putrescine, spermidine, and spermine were greater in hypoxic animals than in controls. alpha-Difluoromethylornithine (DFMO), an inhibitor of polyamine synthesis, attenuated the hypoxia-induced elevations in lung putrescine and spermidine content and blunted the increases in pulmonary arterial pressure and medial thickness. Neither the increased hematocrit nor right ventricular hypertrophy associated with chronic hypoxia were abrogated by DFMO. In addition, DFMO failed to influence vasoconstrictor responses provoked by acute hypoxic ventilation in isolated, buffer-perfused rat lungs. These observations suggest that depression of polyamine biosynthesis with DFMO blunts the sustained increase in pulmonary arterial pressure by attenuating hypoxia-induced medial thickening.     

Deductive analysis of a protein-synthesis mutant of Escherichia coli

A mutant of E. coli, T ^s68b, selected as unable to grow at 43 C, is unable to synthesize proteins at 43 C, though it can carry out this function at 30 C. This defect is shown to be in the protein-synthetic rather than the RNA-synthetic machinery by an analysis of the response of the strain to infection with the RNA bacteriophage f2. An analysis of the capacity for RNA synthesis and the polyribosome content of these cells at 44 C indicates that the defect resides in the elongation step of protein synthesis. No defects could be detected in vitro. The results are discussed in light of similar data on other mutants and in relation to the general approach of analyzing complex mutants selected with ill-defined phenotypes.This work was supported by Grant GM14368 from the National Institute of Health.     

A further study on the dietary-regulated biosynthesis of high-sulphur wool proteins

When the diet of sheep is supplemented by the infusion of sulphur-containing amino acids or casein into the abomasum, the newly synthesized wool shows characteristic changes in its amino acid composition, with significant increases in cystine, proline and serine and decreases in aspartic acid and phenylalanine. This modification seems to be due entirely to an alteration in the overall composition of the high-sulphur proteins and to an increase in their proportion in the fibre. These variations are not the result of a change in the composition of individual proteins, but are due to alterations in their relative proportions and to the initiation of the synthesis of `new' proteins, many of which are extremely rich in cystine. It is suggested that the heterogeneity of the high-sulphur proteins may be due, in part, to similar changes in composition caused by natural variations in the nutrition of sheep.     

Intensity of photosynthesis and chlorophyll content as related to leaf age inNicotiana Sanderae hort

U r?zně starých list? v listové r??ici 90 a? 110 denních rostlin Nicotiana sanderae hort. byly sledovány rozdály v intensitě ?isté fotosynthesy a v obsahu chlorofylu (a + b). Ke stanovení intensity fotosynthesy bylo pou?ito dvou odli?ných metod, a to váhového stanovení p?ír?stku su?iny podle Barto?e, KubÍna a ?et-lÍka (1960) a gazometrického stanovení infra?erveným analyzátorem CO₂. Nejvy??í intensitu fotosynthesy i nejvy??í obsah chlorofylu (vzhledem k plo?e listové) mají mladé, ale ji? dob?e rozvinuté listy, tj. t?etí a? ?tvrté od vrcholu (prvním listem se rozumí list o plo?e asi 20 cm²). Tyto listy nazýváme ?fotosyntheticky dospělými“. Listy nejmlad?í a zejména pak listy star?í mají intensitu fotosynthesy i obsah chlorofylu ni??í; u nejstar?ích list? je intensita fotosynthesy prakticky nulová. Intensita fotosynthesy i obsah chlorofylu se během vývoje mění: jejich momentální rozdíly u list? v genetické spirále jsou z?ejmě shodné s jejich změnami v ontogenesi listu. Pokles intensity fotosynthesy p?i stárnutí list? je rychlej?í ne? pokles obsahu chlorofylu. P?i ur?itém obsahu chlorofylu (tj. asi 2,25 a? 2,45 mg/dm²) klesá intensita ?isté fotosynthesy k nule. Intensita fotosynthesy je v lineárním vztahu k mno?ství chlorofylu (p?i p?epo?tu na plo?nou jednotku), a to nezávisle na poloze listu v genetické spirále. Obě pou?ité metody ke stanovení intensity fotosynthesy poskytly obdobné výsledky.