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.     

Dibutyryl cyclic AMP triggers Ca2+ influx and Ca2+-dependent electrical activity in pancreatic B cells

In the presence of 7 mM glucose, dibutyryl cyclic AMP induced electrical activity in otherwise silent mouse pancreatic B cells. This activity was blocked by cobalt or D600, two inhibitors of Ca2+ influx. Under similar conditions, dibutyryl cyclic AMP stimulated 45Ca2+ influx (5-min uptake) in islet cells; this effect was abolished by cobalt and partially inhibited by D600. The nucleotide also accelerated 86Rb+ efflux from preloaded islets, did not modify glucose utilization and markedly increased insulin release. Its effects on release were inhibited by cobalt, but not by D600. These results show that insulin release can occur without electrical activity in B cells and suggest that cyclic AMP not only mobilizes intracellular Ca, but also facilitates Ca2+ influx in insulin secreting cells.     

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.     

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.