Production of Cricotopus ornatus (Meigen) (Diptera: Chironomidae) in Waldsea Lake,Saskatchewan

Cricotopus ornatus was the predominant chironomid in meromictic, saline Waldsea Lake. Annual production of C. ornatus larvae in the mixolimnion was estimated to be 107 mg m^-2 (dry weight) in 1974, 66.5 mg m^-2 in 1975 and 69.5 mg m^-2 in 1976. These estimates are similar to those for chironomids in Canadian arctic lakes and deep-water areas of the Great Lakes. Annual P/B ratios were 5.4 in 1974, 6.8 in 1975 and 6.8 in 1976. These ratios are in the middle of the range reported for chironomids. The major factors limiting chironomid production in Waldsea Lake appear to be: (1) restriction of the habitable zone because of meromixis with accompanying loss of mobile first and second instars that are swept out of the mixolimnion (2) the relatively narrow zone of good C. ornatus habitat, i.e. areas of dense macrophyte or benthic algal growth and (3) predation by nine-spine stickleback and damselfly naiads.     

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.     

Die Photosynthese von Meerespflanzen in ihrer Beziehung Zum Salzgehalt

Zusammenfassung Werden Blattstücke vonPosidonia oceanica oder Thallusteile vonUlva lactuca unter sonst optimalen Assimilationsbedingungen aus Meerwasser in Süßwasser, überführt, so sinkt hier die apparente Assimilation beiPosidonia bis zu Null oder gar zu negativen Werten ab, beiUlva bis zu etwa 23% der Leistung im Meerwasser. Bei Rückführung in Meerwasser wird die Assimilationsrate ebenso schnell wieder erhöht, die Ausgangswerte werden allerdings innerhalb der Versuchszeit — einige 20-min-Perioden — meist nicht in voller Höhe wieder erreicht.Folgt der Wechsel zwischen Meer- und Süßwasser im Wechsel von 20 min, so reagieren die Versuchspflanzen mit der gleichen Präzision wie auf das Aus- und Einschalten einer Lichtquelle.Wird anPosidonia die photosynthetische Rate in verschiedenen Stufen verdünnten Meerwassers (Verdünnung nicht mit dest. Wasser, sondern mit Leitungswasser von bekanntem Bicarbonatgehalt und p_H) bestimmt und in Prozenten der Leistung in Meerwasser ausgedrückt, so ergibt sich die in Abb. 3 dargestellte Kurve. Innerhalb der Versuchszeit scheint jeder Meerwasserkonzentration ein bestimmter Photosynthesewert zugeordnet zu sein, ein Verhalten, das auf das Vorhandensein von Gleichgewichtszuständen hindeutet, die zwischen dem photosynthetischen System und dem Zustand des Außenmediums bestehen.Infolge der überaus raschen Reaktion der Pflanzen auf Änderungen im Außenmedium wird als Arbeitshypothese die Vermutung ausgesprochen, daß an der Änderung der photosynthetischen Rate bei Übertragung in und Rückführung aus Süßwasser in Meerwasser nicht Zustandsveränderungen imZellinneren, sondern Zustände der Membranen verantwortlich sind, welche das Ausmaß der CO₂-Permeation bestimmen und damit einen begrenzenden Faktor der Photosynthese darstellen.Mit 4 Textabbildungen     

Tissue-specific sorting of the human LDL receptor in polarized epithelia of transgenic mice

The distribution of human low density lipoprotein (LDL) receptors was studied by immunofluorescence and immunoelectron microscopy in epithelial cells of transgenic mice that express high levels of receptors under control of the metallothionein-I promoter. In hepatocytes and intestinal epithelial cells, the receptors were confined to the basal and basolateral surfaces, respectively. Very few LDL receptors were present in coated pits or intracellular vesicles. In striking contrast, in the epithelium of the renal tubule the receptors were present on the apical (lumenal) surface where they appeared to be concentrated at the base of microvilli and were abundant in vesicles of the endocytic recycling pathway. Intravenously administered LDL colloidal gold conjugates bound to the receptors on hepatocyte microvilli and were slowly internalized, apparently through slow migration into coated pits. We conclude that (a) sorting of LDL receptors to the surface of different epithelial cells varies with each tissue; and (b) in addition to a signal for clustering in coated pits, the LDL receptor may contain a signal for retention in noncoated membrane that is manifest in hepatocytes and intestinal epithelial cells, but not in renal epithelial cells or cultured human fibroblasts.     

Effect of the expression of a hepatocyte-specific MHC molecule in transgenic mice on T cell tolerance

A hybrid murine class I gene, Q10/L, was injected into C3H/HeJ fertilized ova to produce transgenic (TG) mice. This fusion gene contained 414 bp of Q10 promoter sequences which was sufficient to direct liver-specific expression in two lines of animals. Animals from these lines did not have Q10/L mRNA in 10 nonhepatic tissues examined including thymus, spleen, and bone marrow. The ontogeny of Q10/Ld expression in both liver and yolk sac paralleled expression of endogenous Q10. Analysis of liver cells from these lines by flow cytometry and immunofluorescence demonstrated the presence of the Q10/L Ag solely on hepatocytes. TG animals showed no signs of hepatic disease as evidenced by an absence of cellular infiltrates in the liver and a normal profile of serum enzymes that are elevated in association with hepatic disease. When spleen cells from TG animals were cocultured with splenocytes that express Ag cross-reactive with Q10/L, CTL were generated that recognized and lysed L cells which express Q10/L. However, the extent of lysis was less than that generated from non-TG control littermates. That these cross-reactive T cells were physiologically significant was demonstrated by adoptive transfer of in vivo primed T cell enriched spleen cells which produced a mononuclear infiltration of the liver of TG recipients. However, inoculation of Q10/L L cells or splenocytes expressing Q10/L cross-reactive Ag into TG mice did not induce cellular infiltration or overt hepatic disease. Whereas inoculation of normal C3H mice with these cells led to priming of Q10/L reactive CTL, anti-Q10/L CTL could not be primed in TG mice. This suggests that Ag expression solely on hepatocytes can lead to inactivation of specific CTL clones and thus account for the observed in vivo tolerance.     

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.