Beitrag zur Flora von Bosnien und der Hercegovina

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MährischeThymus-Formen

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Beitrag zur Flora der Beskiden und des Hochgesenkes

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Regulation of acid hydrolysis of sucrose in acid lime juice sac cells

The sucrose content of acid lime [ Citrus aurantifolia (Christm.) Swing.] juice tissue was measured at time 0 and at various times following incubation at 15.5, 26.6 and 37.7°C. The decline in sucrose content in fruit stored at 15.5°C paralleled the expected values for a sucrose solution at pH 2.1. At higher temperatures, the in vivo sucrose content decreased at significantly lower rates than the expected values. In fruit stored at 26.6 and 37.7°C, the vacuolar pH increased 0.11 and 0.23 units, respectively. When sucrose hydrolysis was recalculated at the increased vacuolar pH of juice cells stored at 26.6 and 37.7°C, the calculated values were similar to the measured values obtained in vivo. It is concluded that within the limits of the experimental conditions, the rates of sucrose acid hydrolysis are regulated by changes in the vacuolar H⁺ concentration.     

Expression and purification of glutamine synthetase cloned from Bacteroides fragilis

A glutamine synthetase (GS) gene, glnA, from Bacteroides fragilis was cloned on a recombinant plasmid pJS139 which enabled Escherichia coli glnA deletion mutants to utilize (NH4)2SO4 as a sole source of nitrogen. DNA homology was not detected between the B. fragilis glnA gene and the E. coli glnA gene. The cloned B fragilis glnA gene was expressed from its own promoter and was subject to nitrogen repression in E. coli, but it was not able to activate histidase activity in an E. coli glnA ntrB ntrC deletion mutant containing the Klebsiella aerogenes hut operon. The GS produced by pJS139 in E. coli was purified; it had an apparent subunit Mr of approximately 75,000, which is larger than that of any other known bacterial GS. There was very slight antigenic cross-reactivity between antibodies to the purified cloned B. fragilis GS and the GS subunit of wild-type E. coli.     

PREY TAKEN BY TAWNY OWLS DURING THE BREEDING SEASON

The diet of Tawny Owls during the breeding seasons 1949-52 in Wytham Woods, near Oxford, was determined (a) from analysis of pellets collected, (b) from observation at night, by the use of a red floodlight, of prey brought to the nest and (c) from records of prey left in the nest made during daily visits to weigh the young.
Analysis of pellets showed an increase in the proportion of moles and beetles (mainly cockchafen) in the diet after the first week of May (the time when, on average, the young owls are about half grown) and a decrease in the proportion of mice and voles.
These changes were confirmed in a more emphatic way from observations of food being brought to the nest and from records of prey left in the nest.
This greater emphasis suggests that tho food brought to the young may differ from that which the adults eat themselves.
The fact that no moles were observed being brought to nests at night, wherean many were recorded as surplus prey in the nest, showed that diurnal hunting is regular during the breeding reaaon.
A true assessment of prey taken by Tawny Owls during the breeding season should be based both on analyeis of pellets cast by the adults and on records of food brought to the nest throughout 24 hours. Such records could best be obtained with an automatic camera and flash and a design of nest-box which is described.