Physiology of F-Pilin Synthesis and Utilization

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis was used to study the synthesis and turnover of F-pilin in membrane preparations of Escherichia coli K-12 under conditions which have been reported to affect the production of F-pili. Incorporation of [³⁵S]methionine into membrane F-pilin by cells in log phase was barely detectable at 25°C, but increased with temperature. The labeled pilin band was prominent in membranes from 37°C cultures and even more prominent if the growth temperature was raised to 42°C. The appearance of other tra products in the membranes was similarly temperature dependent. In cultures grown in glucose minimal medium at 37°C, the relative amount of membrane pilin and traT product synthesis remained unchanged from early log phase through early stationary phase; provision of glycerol or arabinose as a substitute carbon source had no obvious effect. Turnover of traT product and membrane F-pilin, as assessed in an Flac tra mutant strain which is incapable of elaborating pili, was not rapid. Both traT product and pilin subunits labeled in mid-log phase cells were still apparent in the membranes after growth of the cells to stationary phase. The relative amount of labeled pilin decreased with prolonged incubation in stationary phase, but the relative amount of traT product did not decrease even after the culture was incubated for 24 h. When wild-type Flac piliated cells were used, a similar result was obtained, but in this case, loss of F-pilin from the preparations could be acclerated by blending the cells. Although intermittent blending during culture growth caused a slow depletion of the labeled pilin pool, continuous blending resulted in the rapid disappearance of this pool from our preparations. Loss of other membrane polypeptides was not accelerated by our blending procedure, and blending did not affect the turnover of the pilin pool of the Flac tra mutant. Our data are consistent with a model in which pilin subunits are assembled transiently into pili, conserved by retraction, and made available for subsequent reassembly. Growth in 0.01% sodium dodecyl sulfate did not accelerate loss of pilin from the Flac strain compared with the Flac tra strain, and we suggest that in the presence of sodium dodecyl sulfate at this concentration, F-pili are not elaborated from cell surfaces.     

The mechanism of biliary secretion of reduced glutathione. Analysis of transport process in isolated rat-liver canalicular membrane vesicles

Transport of reduced glutathione (GSH) was studied in isolated rat liver canalicular membrane vesicles by a rapid filtration technique. The membrane vesicles exhibit uptake of [2-3H]glycine--labeled GSH into an osmotically reactive intravesicular space. Although the canalicular membrane vesicles possess gamma-glutamyltransferase and aminopeptidase M, enzymes that hydrolyze glutathione into component amino acids, inactivation of the vesicle-associated transferase by affinity labeling with L-(alpha S,5S)-alpha-amino-3-chloro-4,5-dihydro-5-isoxazoleacetic acid (AT-125) had no effect on the initial rate of GSH transport. Chemical analysis revealed that intact GSH accounted for most of vesicle-associated radioactivity. The initial rate of transport followed saturation kinetics with respect to GSH concentration; an apparent Km of 0.33 mM and V of 1.47 nmol/mg protein in 20 s were calculated. These results indicate that transport of GSH across the canalicular membranes is a carrier-mediated process. Replacement of NaCl in the transport medium by KCl, LiCl or choline chloride had no effect on the transport activity of the vesicles. The rate of GSH uptake by the vesicles was enhanced by valinomycin-induced K+-diffusion potential (vesicle inside-positive) and was inhibited by probenecid, indicating that GSH transport across the canalicular membranes is electrogenic and involves the transfer of negative charge. The transport of GSH was inhibited by oxidized glutathione or S-benzyl-glutathione. This transport system in canalicular plasma membranes may function in biliary secretion of GSH and its derivatives which are synthesized in hepatocytes by oxidative processes or glutathione S-transferase.     

Comparison of the localization of nucleic acid synthesis during bud formation on leaf fragments and on intact undetached leaves ofBegonia rex Putz.

The budding capacity ofBegonia rex leaf fragments is well known; that of undetached leaves has been shown by us only recently after treating the leaves with 6γγ DMAAP. Benzyladenine is as effective as 6γγ DMAAP in stimulating budding. Lower temperatures (17°, 22–12°, 12°) are also capable of inducing bud formation but only after a small cut has been made in a main vein of the undetached leaf. Root formation can also be provoked on undetached leaves which have a cut in the main leaf vein by higher temperatures (24–22°) or by an IAA treatment. Differences in the first stages of bud formation on leaf fragments and on undetached leaves are observed using histochemical and histoautoradiographic techniques.     

DNA-dependent in vitro synthesis of enzymes of the galactose operon of Escherichia coli

Summary Two active enzymes of the galactose operon of Escherichia coli, uridyl transferase and galactokinase have been synthesized with high yields in a DNA dependent system for protein synthesis. The unspecific blank values amount to less than two percent of the rate obtained under optimal conditions and permit the accurate determination of even a small fraction of the maximum synthesis rate. Therefore this system provides a sensitive assay for the biological activity of DNA that contains the intact galactose operon of Escherichia coli.The synthesis of these galactose enzymes is to a high extent dependent on the presence of cyclic adenosine-3:5-monophosphate.D-fucose, known as an inducer of the galactose operon in vivo, stimulates the synthesis of galactokinase, indicating that the repressor of the galactose operon in active under these conditions. This stimulation is not observed, if the bacterial extract is prepared from a strain defective for the galactose repressor or if the DNA carries an operator constitutive mutation in the galactose operon. Therefore the stimulation by D-fucose is true derepression.     

Die Carotinoide der grünen Schwefelbakterien: Carotinoidzusammensetzung in 18 Stämmen

Summary The composition of the carotenoids in 18 strains of photosynthetic green sulfur bacteria has been investigated.Chlorobactene predominates in all strains; this pigment seems to be characteristic for all photosynthetic green sulfur bacteria. This main carotenoid is accompanied by various amounts of precursors and the hydroxy compounds of all appearing pigments.     

Über Fibrillärstrukturen im Nebennierenmark von Haus und Wildmeerschweinchen (Cavia aperea f. porcellus L. und Cavia aperea tschudii Fitzinger)

Zusammenfassung Im Nebennierenmark von adulten Wildmeerschweinchen (Cavia aperea tschudii) und Hausmeerschweinchen (Cavia aperea f. porcellus) werden bisher unbekannte intrazelluläre Fibrillenstrukturen nachgewiesen. Licht- und elektronenmikroskopische Befunde zeigen, daß in bestimmten Markzellen Filamentbündel in Gruppen auftreten, die durch das Perikaryon bis zur Zellperipherie zu verfolgen sind. Sie fasern in der Nähe des Plasmalemms auf und bilden desmosomenähnliche Kontaktflächen. Die Einzelfilamente sind ca. 70–100 Å dick. Beim Chinchilla konnten im Mark keine Filamentstränge festgestellt werden, beim Haus- und Wildmeerschweinchen kommen sie in unterschiedlicher Häufigkeit vor.

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Intracellular fibrils in the adrenal medulla of domesticated and wild guinea pigs (Cavia aperea f. porcellus L. and Cavia aperea tschudii fitzinger)

Summary By light and electron microscopic observations intracellular fibrils were found in the adrenal medulla of adult wild (Cavia aperea tschudii) and domesticated guinea pigs (Cavia aperea f. porcellus). In certain cells of the adrenal medulla bundles of filaments can be traced from the perinuclear region into the periphery of the cells. Near the plasma membrane they split apart and attach to the desmosome-like regions. The individual filaments are about 70–100 Å in diameter. In adrenal medullary cells of chinchilla no fibrillar strands were observed, in wild and domesticated guinea pigs they occur in different numbers.

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Die Untersuchung wurde mit dankenswerter Hilfe der Deutschen Forschungsgemeinschaft durchgeführt.     

Expression of O-glycans during enterocytic differentiation of HT-29 cells

The expression of O- and N-glycan chains during the enterocytic differentiation of HT-29 cells was followed using L-[63H]-fucose and D-[6-3H]-glucosamine radiolabeling. Whatever the cell population, i.e., differentiated or undifferentiated, the incorporation of radiolabeled sugars into glycoproteins was similar. However, differences among these two cell populations were noted when the ratio [3H]-glucosamine/[3H]-galactosamine and the sensitivity of glycopeptides to mild alkaline treatment were followed. From these data, we could conclude that there is a shift in the high molecular weight glycopeptides during the differentiation of HT-29 cells meaning an increase of O-linked glycopeptides correlated with a decrease of N-linked forms.     

Association of the Red Ring Nematode and Other Nematode Species with the Palm Weevil,Rhynchophorus palmarum

The palm weevil, Rhynchophorus palmarum (L.), was collected in cocoons from red ring-diseased coconut palms (Cocos nucifera L.) in Trinidad and Tobago. Juveniles of five species of nematodes were extracted from the genitalia and macerated bodies of newly emerged adults of the palm weevil: Rhadinaphelenchus cocophilus (Cobb) Goodey (the red ring nematode), Teratorhabditis sp., Diplogasteritus sp., Mononchoides sp., and Bursaphelenchus sp. Over 90% of newly emerged weevil females and males were infested internally with red ring nematode juveniles, and over 47% of the weevils contained more than 1,000 red ring nematodes each. There was no significant correlation between weevil body length and the number of red ring nematodes carried internally by each weevil. Teratorhabditis sp. and Diplogasteritus sp. were extracted from over 50% of the palm weevils, and Monochoides sp. and Bursaphelenchus sp. were found in a small proportion of the weevils. Field-collected adult weevils were also internally and externally infested with a Rhabditis sp., which was not observed in or on weevils allowed to emerge from field-collected cocoons.     

Sexual differences in survival rates of adult pipistrelle bats (Pipistrellus pipistrellus) in South Sweden

Summary A pipistrelle bat (Pipistrellus pipistrellus) population in southernmost Sweden was studied for eight consecutive breeding seasons by means of bat boxes. Survival rates were calculated using Cormack's stochastic technique. The mean survival rate of adult females exceeded that of territorial males. Annual variations in survival rates were most evident in males, low rates being observed in years following wet autumns. Energy constraints imposed on territorial males by the mating system, a resource defence polygyny, were assumed to account for the differences obtained in survival rates between the sexes.