Charge and acidity compensation during proton-sugar symport in Chlorella: The H+-ATPase does not fully compensate for the sugar-coupled proton influx

This study was undertaken in order to demonstrate the extent to which the activity of the plasmalemma H⁺-ATPase compensates for the charge and acidity flow caused by the sugar-proton symport in cells of chlorella vulgaris Beij.. Detailed analysis of H⁺ and K⁺ fluxes from and into the medium together with measurements of respiration, cytoplasmic pH, and cellular ATP-levels indicate three consecutive phases after the onset of H⁺ symport. Phase 1 occurred immediately after addition of sugar, with an uptake of H⁺ by the hexoseproton symport and charge compensation by K⁺ loss from the cells and, to a smaller degree, by loss of another ion, probably a divalent cation. This phase coincided with strong membrane depolarization. Phase 2 started approximately 5 s after addition of sugar, when the acceleration of the H⁺-ATPase caused a slow-down of the K⁺ efflux, a decrease in the cellular ATP level and an increase in respiration. The increased respiration was most probably responsible for a pronounced net acidification of the medium. This phase was inhibited in deuterium oxide. In phase 3, finally, a slow rate of net H⁺ uptake and K⁺ loss was established for several further minutes, together with a slight depolarization of the membrane. There was hardly any pH change in the cytoplasm, because the cytoplasmic buffering capacity was high enough to stabilize the pH for several minutes despite the net H⁺ fluxes. The quantitative participation of the several phases of H⁺ and K⁺ flow depended on the pH of the medium, the ambient Ca²⁺ concentration, and the metabolic fate of the transported sugar. The results indicate that the activity of the H⁺-ATPase never fully compensated for H⁺ uptake by the sugar-symport system, because at least 10% of symport-caused charge inflow was compensated for by K⁺ efflux. The restoration of pH in the cytoplasm and in the medium was probably achieved by metabolic reactions connected to increased glycolysis and respiration.Abbreviations DMO dimethyloxazolidinedione - EDTA ethylcnediaminetetraacetic acid - p.c. packed cell volume     

The effect of low- and high-density lipoprotein cholesterol on steroid hormone production and ACTH-induced differentiation of rat adrenocortical cells in primary culture

Summary The choroid plexus consists of the choroidal epithelium, a derivative of the neural tube, and the choroidal stroma, which originates from the embryonic head mesenchyme. This study deals with epithelio-mesenchymal interactions of these two components leading to the formation of the organ. Grafting experiments of the prospective components have been performed using the quail-chicken marker technique. Prospective choroidal epithelium of quail embryos, forced to interact with mesenchyme of the body wall of chicken embryos, gives rise to a choroid plexus showing normal morphogenesis and differentiation. The choroidal epithelium induces the differentiation of organtypical fenestrated capillaries, which are highly permeable to intravenously injected horseradish peroxidase. The choroidal epithelium of the grafts constitutes a blood-cerebrospinal fluid barrier. On top of the choroidal epithelium, there are epiplexus cells displaying a typical ultrastructure. The experimental results show that these cells do not originate from the transplanted neural epithelium. Prospective choroidal stroma of chicken embryos does not exert a choroid plexus-inducing influence upon a quail embryo's neural epithelium isolated from parts of the brain that normally do not develop a choroid plexus. The experiments show that the choroidal epithelial cells are determined at least three days before the first organ anlage is detectable.This work was supported by the Deutsche Forschungsgemeinschaft (grant Ch 44/7-1)     

Plasmids in the bacterial assemblage of a dystrophic Lake: Evidence for plasmid-encoded nickel resistance

Sixty-two aerobic bacterial strains isolated from the unproductive dystrophic Lake Skärshultsjön (South Sweden) were screened for plasmids. The lake is considered to be an extreme environment because of its high concentration of persistent but nontoxic humic compounds. One-third of the isolates harbored multiple plasmids usually of similar high molecular weights (>25 Mdal). The plasmid-bearing strains were members of the common aquatic taxaPseudomonas spp.,Acinetobacter sp.,Alcaligenes sp.,Aeromonas/Vibrio group, andEnterobacteriaceae (taxonomy is tentative). The majority of isolates displayed multiple resistance to antibiotics and heavy metals. Some of them were capable of degrading aromatic compounds. Three isolates were chosen for curing experiments. Only strain S-68, anAlcaligenes sp., could be cured of one of its two plasmids. It harbored the two cryptic plasmids pQQ32 and pQQ70 of 32 and ca. 70 Mdal, and the latter was segregated during ethidium bromide treatment. Parental strain S-68 was capable of degrading some of nonchlorinated phenolic compounds and displayed resistance to a broad spectrum of antibiotics and the heavy metals Co²⁺, Ni²⁺, Zn²⁺, Cd²⁺, and Hg²⁺. Derivative strain S-68-41 lost its resistance to nickel, suggesting segregated plasmid PQQ70 coded for nickel resistance. Transformation experiments to restore nickel resistance in the cured derivative strain were not successful.     

Dietary zinc deficiency has no effect on auditory brainstem responses in the rat

Zinc has been shown to effect--in vitro--a number of processes associated with neurotransmission. We have tested whether the rate of impulse conduction--in vivo--as measured from the latencies of auditory brainstem responses (ABR), is influenced by dietary zinc deficiency in the rat. Dietary zinc deficiency for up to 26 wk had no effect on the wave I-IV interval compared to zinc-adequate fed animals. The results are discussed in relation to the observed constancy of brain overall and extracellular fluid zinc concentrations under conditions of dietary zinc deficiency.     

Protease activity and proteolytic modification of cellulases from a Trichoderma reesei QM 9414 selectant

Summary The secretion of multiple forms of cellulolytic enzymes by a Trichoderma reesei QM 9414 selectant exhibiting high protease activity (T. reesei QM 9414/A 30) was investigated using monoclonal, domain-specific antibodies against cellobiohydrolase (CBH) I, CBH II and -glucosidase, and a polyclonal antibody against endoglucanase I. The pattern of appearance of these proteins was followed during growth of the fungus on Avicel cellulose, using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE)/Western blotting/immunostaining. Evidence was obtained that, at late cultivation stages, CBH I and II became partially modified to lower molecular weight components, whereas -glucosidase and endoglucanase I appeared to remain largely intact. Modification of CBH I appeared to commence from the carboxy-terminal AB region, whereas CBH II appeared to become modified both from the amino- (ABB') and the carboxy-terminal. Evidence for a protease activity that modifies the already truncated cellobiohydrolases in the culture filtrate was obtained. These results show that proteolysis at late culture stages may contribute to the multiplicity of cellulases found in T. reesei culture fluids. Initial proteolytic cleavage of CBH I and II may, however, involve an unusual protease not detectable by the azocasein method.Offprint requests to: C. P. Kubicek     

Heritability of bone mass: a longitudinal study in aging male twins

Midshaft radial bone mass was first measured from 1970 through 1972 by photon absorptiometry in 42 pairs of monozygotic (MZ) and 38 pairs of dizygotic (DZ) male Caucasian twins (age 44-55 years). The MZ intraclass correlation (rMZ) of .70 was significantly larger (P less than .05) than the DZ correlation (rDZ) of .45, providing evidence for genetic influences (Smith et al. 1973). Radial bone mass measurements repeated 16 years later (1986-87) on 25 of the MZ pairs and on 21 of the DZ pairs revealed an rMZ of .61 and an rDZ of .44, but the difference was not significant (P greater than .05). The twins had an average radial mass loss of 0.49%/year between the two examinations. The rMZ (.52) and rDZ (.49) values for the 16-year loss in radial mass were both significantly different from zero, but their similar size indicated that the correlations were due to nongenetic factors. In a search for the source of genetic influences on adult radial mass, heritability was estimated by the formula 2(rMZ - rDZ) for radial width and was found to be .66 and .76 (P less than .05) for examinations 1 and 2, respectively. An index of radial density (mass/width) was calculated, and the differences between rMZ and rDZ were not significant at either examination. The intraclass correlations (rMZ = .35; rDZ = .43) were both significant for the loss of bone density between examinations but provided no evidence for genetic influences, results similar to the findings for the loss of mass.(ABSTRACT TRUNCATED AT 250 WORDS)     

Individualgeschichte und Gesangsauspr?gung beim Star (Sturnus vulgaris) in einer Kolonie

Zusammenfassung Die Lautäußerungen der Stare können in Gesangsstrophen und Pfeiflaute unterteilt werden. Pfeiflaute sind kurz (bis 2 s) und einfach gebaut, während die Strophen wesentlich länger andauern (meist über 20 s) und sich aus zahlreichen komplex gebauten Untereinheiten zusammensetzen. In einer Kolonie bei Frankfurt am Main, in der die Individuen durch Farbringe gekennzeichnet sind, wurde der individuelle Variationsspielraum der Lautäußerungen analysiert. In den Feinstrukturen der Pfeifthemen glichen sich die Koloniemitglieder weitgehend aneinander an. In den Feinstrukturen der Motivtypen der Gesangsstrophen traten dagegen große individuelle Unterschiede auf. , die während Jahren in der gleichen Kolonie brüteten, sangen nur sehr wenige gemeinsame Motivtypen. Die Repertoiregröße variierte zwischen 17–39 Motivtypen. Im Herbstgesang traten 5 bisher noch nicht beobachtete Motivtypen auf. Es gibt somit deutliche Hinweise darauf, daß auch der adulte Star neue Laute erlernen kann.

---

Individual history and song structure of Starlings (Sturnus vulgaris) living in a colony

Summary Starling's song can be divided into warbling and whistles. Whistles have a short and simple structure, whereas warbling is sung in long sequences (most often more than 20 s). In the warbling one can distinguish many different subunits (repetition of motifs). The individual variability of songs was studied in a colony near Frankfurt/Main in West Germany, where starlings were colour banded since 1969. The following results were obtained:Birds from the same colony uttered nearly identical or very similar microstructures in the species-specific whistle themes. Different to the whistle themes very distinct individual differences characterized the warbling. Only a few motif types were common among colony members. The individual repertoire size ranged from 17 to 39 motif types. Comparison of the song of one individual between the breeding season and the following autumn shows that motifs, which were not observed during spring occurred in the autumn. This observation is a hint that starlings are capable to learn new motif types even as adults.

---

---

Stipendium der Alexander-von-Humboldt-Stiftung     

Appearance of alpha-smooth muscle actin in human eye lens cells of anterior capsular cataract and in cultured bovine lens-forming cells

Using light and electron-microscopic immunolocalization techniques, and gel electrophoresis combined with immunoblotting, we have examined the expression of cytoskeletal proteins in normal human fetal, child and adult lenses, in human anterior capsular cataract and in bovine lens cells in vivo and in vitro. In this report, we focus our observations on the pattern of actin-isoform expression during normal and pathological situations in vivo and culture conditions. We have noted that cells of developing and mature human lenses as well as bovine lens cells in situ contain only beta- and gamma-actins. In contrast, alpha-smooth muscle (alpha-sm) actin, an isoform typical of smooth muscle differentiation, was demonstrated in bovine lens cells at different times of culture. Moreover, the multilayered cells observed in the subcapsular zone of human anterior capsular cataract were characterized by the presence of alpha-sm actin. Thus, extensive changes in actin-isoform expression take place in lens cells growing in culture and may also occur during cataractogenesis. The biological meaning of the appearance of a marker of myoid differentiation in the ectodermally derived lens-forming cells is discussed.     

Aerobic nitrate and nitrite reduction in continuous cultures of Escherichia coli E4

Nitrate and nitrite was reduced by Escherichia coli E4 in a l-lactate (5 mM) limited culture in a chemostat operated at dissolved oxygen concentrations corresponding to 90–100% air saturation. Nitrate reductase and nitrite reductase activity was regulated by the growth rate, and oxygen and nitrate concentrations. At a low growth rate (0.11 h^–1) nitrate and nitrite reductase activities of 200 nmol · mg^–1 protein · min^–1 and 250 nmol · mg^–1 protein · min^–1 were measured, respectively. At a high growth rate (0.55 h^–1) both enzyme activities were considerably lower (25 and 12 nmol mg^–1 · protein · min^–1). The steady state nitrite concentration in the chemostat was controlled by the combined action of the nitrate and nitrite reductase. Both nitrate and nitrite reductase activity were inversely proportional to the growth rate. The nitrite reductase activity decreased faster with growth rate than the nitrate reductase. The chemostat biomass concentration of E. coli E4, with ammonium either solely or combined with nitrate as a source of nitrogen, remained constant throughout all growth rates and was not affected by nitrite concentrations. Contrary to batch, E. coli E4 was able to grow in continuous cultures on nitrate as the sole source of nitrogen. When cultivated with nitrate as the sole source of nitrogen the chemostat biomass concentration is related to the activity of nitrate and nitrite reductase and hence, inversely proportional to growth rate.     

Search for polythionates in cultures of Chromatium vinosum after sulfide incubation

Cultures of Chromatium vinosum, devoid of sulfur globules, were supplemented with sulfide and incubated under anoxic conditions in the light. The concentrations of sulfide, polysulfides, thiosulfate, polythionates and elemental sulfur (sulfur rings) were monitored for 3 days by ion-chromatography and reversed-phase HPLC. While sulfide disappeared rapidly, thiosulfate and elemental sulfur (S₆, S₇ S₈ rings) were formed. After sulfide depletion, the concentration of thiosulfate decreased fairly rapidly, but elemental sulfur was oxidized very slowly to sulfate. Neither polysulfides (S _x ^2– ), polythionates (S_nO ₆ ^2– , n=4–6), nor other polysulfur compounds could be detected, which is in accordance with the fact that sulfide-grown cells were able to oxidize polysulfide without lag. The nature of the intracellular sulfur globules is discussed.