Trehalase activity in extracts of Phycomyces blakesleeanus spores following the induction of germination by heat activation

The heat activation of trehalase in extracts of sporangiospores of Phycomyces blakesleeanus, following the induction of germination by heat activation and the gelatinization of potato starch granules were studied under different conditions in order to discriminate between several phenomena as possible triggers in the activation of trehalase.Short-chain alcohols (from methanol to pentanol) lower the activation temperature of trehalase while long-chain alcohols (from heptanol to nonanol) raise it. Short-chain alcohols also lower the gelatinization temperature of potato starch granules, while long-chain alcohols, hexanol and heptanol have hardly any influence on the gelatinization temperature. Octanol raises the gelatinization temperature. More polar phenols lower the activation temperature of trehalase, while more apolar phenols will raise it. The gelatinization temperature of starch granules is more lowered by the polar polyphenols than by the more apolar phenols.The effect of high pressure on starch gelatinization was investigated in order to compare data from such a model system with the data on trehalase activation.The gelatinization temperature of starch granules is shifted upwards with about 3–5 K/1000 atm (1.013×10⁵ kPa). Pressures higher than 1500 atm do not further increase the gelatinization temperature. However, no reversal of the effect, as occurs with protein conformational changes, is seen with pressure up to 2500 atm. Also for trehalase activation we find a continuous upward shift of the activation temperature with about 5–9 K/1000 atm. These data are in agreement with a thermal transition in a polysaccharide matrix, being the trigger in the heat activation of trehalase.     

PHYTOTAB — A program package for Braun-Blanquet tables

A computer program package of six programs for vegetation classification is described. The package includes raw field-data input, automatic and user sequencing modes, final table and synoptic table preparation which are camera-ready and also allows the user the option of ordinating by means of DECORANA.     

Purification and partial characterization of the carbohydrate structure of lysosomal N-acetyl-beta-D-hexosaminidases from bovine brain

1. The lysosomal forms A and B, and an intermediate form I of N-acetyl-beta-D-hexosaminidase (EC 3.2.1.30) were isolated from bovine brain, resulting in the following purification factors and specific activities: hexosaminidase A 20255, 103 U mg-1; hexosaminidase B 34715, 134 U mg-1; hexosaminidase I 15241, 78 U mg-1. 2. The molecular weights of the polypeptide chains were identical for each isoenzyme: two bands of 50 and 53 k daltons were found. 3. Carbohydrate analysis showed the presence of mannose, galactose, N-acetylglucosamine and sialic acid. This composition, and the absence of N-acetylgalactosamine, indicated that only N-glycosidically linked oligosaccharide chains are present. 4. The amino-acid composition showed no substantial differences for the three isoenzymes.     

Discontinuation syndrome after continuous infusion of clonidine in the spontaneously hypertensive rat

In conscious spontaneously hypertensive rats prepared with permanent indwelling aortic catheters the continuous infusion of clonidine (500 μg/kg/day) via an ALZET miniosmopump induced significant reductions in blood pressure and heart rate. These effects were well sustained during 12 days of treatment. A marked overshoot in heart rate was observed following withdrawal of clonidine administration. The tachycardia persisted for more than 36 hours. Mean arterial pressure exceeded control level slightly in the immediate withdrawal period only, whereas significant blood pressure lability was observed for more than 36 hours. These withdrawal symptoms were accompanied by an elevation of plasma noradrenaline concentration. The present study shows the consistent antihypertensive and bradycardic activities of clonidine during 12 days of infusion in spontaneously hypertensive rats. Furthermore, this model may provide a useful tool in the study of withdrawal phenomena of antihypertensive drugs.     

Endogenous Cytokinins in Bougainvillea ;San Diego Red': I. OCCURRENCE OF CYTOKININ GLUCOSIDES IN THE ROOT SAP

Using chromatographic, chemical, and enzymic techniques, 11 compounds capable of stimulating the division of soybean callus cells were tentatively identified in the root sap of Bougainvillea `San Diego Red.' These cytokinin-like compounds included phosphorylated and glucosylated forms of zeatin, ribosylzeatin, and their dihydro derivatives. In addition, isopentenyl adenosine and isopentenyl adenine were apparently also present. The occurrence of glucosylated derivatives in the root sap of plants has not been substantiated previously.     

Drone bees fixate the queen with the dorsal frontal part of their compound eyes

Summary Free flying drone bees (Apis mellifera carnia () were filmed from the side while chasing the honey bee queen or landing on a hive.Drones use the upper frontal part of the field of view of their eyes while chasing the queen. They fixate with the lower frontal part of the field of view of their eyes during landing. Drones keep a particular distance from the queen while chasing her.The diameter of ommatidial lenses in drones shows a maximum in the region where the queen is fixated.Niedersächsisches Landesinstitut für Bienenforschung und Bienenwirtschaftliche Betriebslehre, Wehrstrasse 4, D-3100 Celle, Federal Republic of GermanyLehrstuhl Entwicklungsphysiologie, Fakultät für Biologie, Universität Tübingen, Auf der Morgenstelle, D-7400 Tübingen, Federal Republic of GermanyWe thank Walter F. Gelinski for kind cooperation and Professor W. Engels for support.