Properties of auxin binding sites in different subcellular fractions from maize coleoptiles

In-vitro binding of labeled auxins to sedimentable particles was tested in subcellular fractions from homogenates of maize (Zea mays L.) coleoptiles. The material was fractionated by differential centrifugation or on sucrose density gradients. It was confirmed that the major saturable binding activity (site I) for 1-naphthyl[1-¹⁴C]acetic acid is associated with vesicles derived from the endoplasmatic reticulum. A second type of specific auxin binding (site II) could be distinguished by several criteria, e.g. by the low affinity towards phenylacetic acid. The particles carrying site II could be clearly separated from markers of the endoplasmatic reticulum, the plasmalemma, the mitochondria and the nuclei, while their density as well as sedimentation velocity correlated with particle-bound acid phosphatase, indicating a localization at the tonoplast. In contrast to site I, binding at site II was hardly affected by a supernatant factor and by sulfhydryl groups. However, the specificity pattern of site II towards auxins and auxin analogs was very similar to that of site I tested in the presence of supernatant factor. The existence of a third auxin receptor localized in plasma membrane-rich gradient fractions was indicated by a preferential in-vitro binding of 2,4-dichlorophenoxyacetic acid.Abbreviations 1-NAA 1-naphthyl acetic acid - 2-NAA 2-naphthyl acetic acid - IAA 3-indolyl acetic acid - PAA phenyl acetic acid - 2,4-D 2,4-D-dichlorophenoxy acetic acid - D-2,4-DP dichlorophenoxy isopropionic acid - NPA 1-N-naphthyl phthalamic acid - ER endoplasmatic reticulum - SF supernatant factor     

Seasonal dynamics of moss-dwelling chironomid communities

Chironomid communities of mosses in a small upland stream in central Germany were highly dynamic across the year with respect to their abundance, biomass and dominant taxa. During 1988 semi-submersed mosses near a main spring and those occurring some 700 m downstream were compared with permanently submersed mosses in immediate vicinity of the downstream site. All the chironomids sampled were conspicuously small, with nearly 98% being less than 5 mm in length. A total of 65 chironomid species from 26 genera were found, with a higher diversity occurring near the source and a change in dominant taxa along the upper stream section. The mean abundance in permanently submersed mosses (250 larvae/10 cm², n = 125) was about five times higher than in semi-submersed mosses. The maximum value of 830 larvae/10 cm² (n = 1) is the highest chironomid density ever reported, which is explained by the sampling method used. The mean standing crop was also highest in permanently submersed mosses (1.5 mg AFDW/10 cm² (n = 125)), even though the highest individual value was recorded in semi-submersed mosses near the spring (10.4 mg AFDW/10 cm²). The evidence suggested that the dominance of chironomid taxa depended mainly on the location of the moss along the stream, whereas abundance and biomass were determined mainly by constancy in the ambient discharge as well as the factors influenced by this (e.g. temperature, detritus deposition). A trend was seen towards a seasonal succession among the chironomid taxa colonizing lotic mosses.     

Purification and Properties of a Thermoactive Glucoamylase from Clostridium thermosaccharolyticum

A bacterial glucoamylase was purified from the anaerobic thermophilic bacterium Clostridium thermosaccharolyticum and characterized. The enzyme, which was purified 63-fold, with a yield of 36%, consisted of a single subunit with an apparent molecular mass of 75 kDa. The purified enzyme was able to attack α-1,4- and α-1,6-glycosidic linkages in various α-glucans, liberating glucose with a β-anomeric configuration. The purified glucoamylase, which was optimally active at 70°C and pH 5.0, attacked preferentially polysaccharides such as starch, glycogen, amylopectin, and maltodextrin. The velocity of oligosaccharide hydrolysis decreased with a decrease in the size of the substrate. The K_m values for starch and maltose were 18 mg/ml and 20 mM, respectively. Enzyme activity was not significantly influenced by Ca²⁺, EDTA, or α- or β-cyclodextrins.     

Life cycle ofPseudodiamesa branickii (Chironomidae) in a small upland stream

The generation time ofP. branickii was studied using larval samples in conjunction with rearing experiments and continuous collection of egg masses across one year. This species produced three generations per year in a central German stream (280 m a.s.l., 50° 40 N). Its generation time was variable and obviously influenced by the photoperiod to which eggs and larvulae were subjected. It is thus concluded that two strains ofP. branickii were present in a single population, one bivoltine and the other trivoltine.     

Carbon Balance Studies of Glucose Metabolism in Rat Cerebral Cortical Synaptosomes

Synaptosomes were isolated from rat cerebral cortex and incubated with [U-14C]-, [1-14C]- or [6-14C]glucose. Glucose utilization and the metabolic partitioning of glucose carbon in products were determined by isotopic methods. From the data obtained a carbon balance was constructed, showing lactate to be the main product of glucose metabolism, followed by CO2, amino acids and pyruvate. Measuring the release of 14CO2 from glucose labelled in three different positions allowed the construction of a flow diagram of glucose carbon atoms in synaptosomes, which provides information about the contribution of the various pathways of glucose metabolism. Some 2% of glucose utilized was calculated to be degraded via the pentose phosphate pathway. Addition of chlorpromazine, imipramine or haloperidol at concentrations of 10(-5) M reduced glucose utilisation by 30% without changing the distribution pattern of radioactivity in the various products.     

Metabolism and binding in vitro of 5 alpha-androstane-3 beta, 17 beta-diol and of 5 alpha-androstane-3 alpha, 17 beta-diol in cell fractions of rat ventral prostate and liver.

Rat ventral prostate and liver were investigated for the binding in vitro to particulate fractions and for the metabolism of 5 alpha-androstane-3 beta, 17 beta-diol. Comparative investigations were carried out on the metabolism of 5 alpha-androstane-3 alpha, 17 beta-diol. Preparations of the liver were investigated in order to establish the organ specificity of the method. In the prostate, the bulk of the metabolites of 5 alpha-androstane-3 beta, 17 beta-diol was present as steroids of high polarity. Of the less polar metabolites, 17 beta-hydroxy-5 alpha-androstan-3-one, 3 beta-hydroxy-5 alpha-androstan, 17-one and 5 alpha-androstane-3 alpha, 17 beta-diol were detectable. The binding of a 5 alpha-androstane-3 beta, 17 beta-diol to mitochondria and microsomes was unspecific. In the liver, among the less polar metabolites, 3 beta-hydroxy-5 alpha-androstan-17-one was the main metabolite, and the binding was unspecific. The main metabolite in the prostate homogenate of 5 alpha-androstane-3 alpha, 17 beta-diol was 17 beta-hydroxy-5 alpha-androstan-3-one. The portion of highly polar steroids was very low. The portion of unmetabolized hormone was distributed almost equally among the different cell preparations except the nuclei, in which 17 beta-hydroxy-5 alpha-androstan-3-one was higher and 5 alpha-androstane-3 alpha, 17 beta-diol was lower than in the remaining cell fractions.     

Agarose gel electrophoresis and restriction endonuclease analysis of largeStaphylococcus plasmids

Preliminary studies using an improved method for the agarose gel electrophoresis of semipurified, cleared lysates of staphylococci have indicated some distinct differences in plasmid composition between the coagulase-positive speciesStaphylococcus aureus andStaphylococcus intermedius, and various coagulase-negative species. Penicillinase-positive strains ofS. intermedius andS. simulans did not carry large penicillinase plasmids like most penicillinase-positive strains ofS. aureus. Most coagulase-negative species examined demonstrated complex plasmid profiles. Codigestion by the restriction endonucleasesHaeIII andHpaI offered a useful approach for “fingerprinting” large plasmids from various strains and species.     

Chinning by maleTupaia belangeri: The effects of scent marks of conspecifics and of other species

Journal of Comparative Physiology A -     

EpCAM: Structure and function in health and disease

Injection of tumor cells in mice more than 30 years ago resulted in the discovery of an epithelial antigen, later defined as a cell adhesion molecule (EpCAM). Although EpCAM has since evoked significant interest as a target in cancer therapy, mechanistic insights on the functions of this glycoprotein have been emerging only very recently. This may have been caused by the multitude of functions attributed to the glycoprotein, its localization at different subcellular sites and complex posttranslational modifications. Here, we review how EpCAM modifies cell–cell contact adhesion strength and tissue plasticity, and how it regulates cell proliferation and differentiation. Major knowledge derived from human diseases will be highlighted: Mutant EpCAM that is absent from the cell surface leads to fatal intestinal abnormalities (congenital tufting enteropathy). EpCAM-mediated cell proliferation in cancer may result from signaling (i) via regulated intramembrane proteolysis and/or (ii) the localization and association with binding partners in specialized membrane microdomains. New insight in EpCAM signaling will help to develop optimized cancer therapies and open new avenues in the field of regenerative medicine.