Biochemical characterization of chromatin fractions isolated from induced and uninduced friend erythroleukemia cells

Summary Chromatin fractions from Friend erythroleukemia cells after induction of differentiation by dimethylsulfoxide (DMSO) were compared in their biochemical characteristics to fractions from uninduced cells. Fractions were prepared by extracting chromatin from nuclei after mild micrococcal nuclease treatment with increasing concentrations of NaCl according to Sanders [1]. This procedure has been found to release chromatin containing hyperacetylated histones preferentially [2]. The fractions obtained by this procedure were analysed in respect to the amount of chromatin released, the amount of histone H1, the degree of acetylation of histone H4, the presence of non-histone proteins and the concentration of transcribed and non-transcribed sequences. It was found that the fractions differ in the amount of histone H1 present, in several non-histone proteins and in the acetylation of histonie H4, regardless whether induced or uninduced cells were analysed. The distribution of transcribed sequences versus non-transcribed sequences among the fractions was the same, demonstrating that this fractionation procedure, although leading to fractions with biochemical differences, is not able to discriminate functional states of chromatin and that the biochemical characteristics of the fractions may be common to both, active as well as inactive states of chromatin.     

Die Verbreitung des Weidensperlings (Passer hispaniolensis) in Marokko

Zusammenfassung In Marokko fällt die südliche Verbreitungsgrenze des Weidensperlings wahrscheinlich mit dem Nordrand des Antiatlas zusammen. Aus den Oasen der ehemaligen Spanischen Sahara liegen keine Beobachtungen vor. Aus dem Raum Oujda sind die östlichsten Populationen, die ständig zwischen Marokko und Algerien migrieren, bekannt. Landnutzung und Klima prägen entscheidend die Dispersion des Weidensperlings. Als euryöke Art ist er in der Lage, das reichhaltige Angebot an Schlaf- und Brutplätzen sowie an Nahrung und Wasser in den ackerbaulichen Nutzflächen zu verwerten. Auffallend ist, daß die Hauptverbreitungszonen mit den großen ackerbaulichen Nutzflächen zusammenfallen. Während die agrarischen Nutzflächen sich in den letzten Jahrzehnten im Zuge der Modernisierung der Landwirtschaft rapide änderten, und das erklärte Ziel für das Jahr 2000 in einer bewässerten Fläche von einer Million Hektar besteht, gingen die ursprünglichen Habitate des Weidensperlings, wie die Bereiche der mauretanischen Wüstensteppengebiete, drastisch zurück. Ferner konnte im Raum Marrakech eine Abnahme der Niederschläge beobachtet werden, die das für die Weidensperlinge verfügbare Nahrungsangebot entscheidend beeinflußt und somit die Populationsdynamik steuert.

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On the distribution of the Spanish Sparrow (Passer hispaniolensis) in Morocco

Summary In Morocco, the southernmost border of the distribution of the Spanish Sparrow coincides probably with the North-Antiatlas. From the oasis of the former Spanish Sahara don't exist any observations. In the region of Oujda the easternmost populations are found which are migrating permanently between Morocco and Algeria. The euryoecous species is able to use a high variability of different roosts, breeding sites, resources of food and water in the agricultural areas. A high overlap of the main distribution areas with the large agricultural regions is obvious. While the cultivated areas have been changed heavily during the modernisation periode of the Moroccan agriculture the original habitats of the Spanish Sparrow (i. e. the parts in the Mauretanian desert-steppe regions) disappeared dramatically. The goal of the year 2000 lies in an irrigated scheme of 1.000.000 ha. Moreover, a decrease of the precipitation in the region of Marrakech was observed, which has a great influence on the food available for the species and which therefore controls the population dynamics.

     

Odorant response of isolated olfactory receptor cells is blocked by amiloride

Summary Olfactory receptor cells were isolated from the nasal mucosa ofRana esculenta and patch clamped. Best results were obtained with free-floating cells showing ciliary movement. 1)On-cell mode: Current records were obtained for up to 50 min. Under control conditions they showed only occasional action potentials. The odorants cineole, amyl acetate and isobutyl methoxypyrazine were applied in saline by prolonged superfusion. At 500 nanomolar they elicited periodic bursts of current transients arising from cellular action potentials. The response was rapidly, fully and reversibly blocked by 50 m amiloride added to the odorant solution. With 10 m amiloride, the response to odorants was only partially abolished. 2)Whole-cell mode: Following breakage of the patch, the odorant response was lost within 5 to 15 min. Prior to this, odorants evoked a series of slow transient depolarizations (0.1/sec, 45 mV peak to peak) which reached threshold and thus elicited the periodic discharge of action potentials. These slow depolarizing waves were reversibly blocked by amiloride, which stabilized the membrane voltage between –80 and –90 mV. We conclude that amiloride inhibits chemosensory transduction of olfactory receptor cells, probably by blocking inward current pathways which open in response to odorants.     

Protonmotive force in freshwater sulfate-reducing bacteria,and its role in sulfate accumulation in Desulfobulbus propionicus

The protonmotive force in several sulfate-reducing bacteria has been determined by means of radiolabelled membrane-permeant probes (tetraphenyl-phosphonium cation, TPP⁺, for , and benzoate for pH). In six of ten freshwater strains tested only the pH gradient could be determine, while the membrane potential was not accessible due to nonspecific binding of TPP⁺. The protonmotive force of the other four strains was between –110 and –155 mV, composed of a membrane potential of –80 to –140 mV and a pH gradient between 0.25 and 0.8 (inside alkaline) at pH_out=7. In Desulfobulbus propionicus the pH gradient decreased with rising external pH values. This decrease, however, was compensated by an increasing membrane potential. Sulfate, which can be highly accumulated by the cells, did not affect the protonmotive force, if added in concentrations of up to 4 mM. The highest sulfate accumulation observed (2500-fold), which occurred at external sulfate concentrations below 5 M, could be explained by a symport of three protons per sulfate, if equilibrium with the protonmotive force was assumed. At higher sulfate concentrations the accumulation decreased and suggested an electroneutral symport of two protons per sulfate. At sulfate concentrations above 500 M, the cells stopped sulfate uptake before reaching an equilibrium with the protonmotive force.Abbreviations CCCP carbonyl cyanide m-chlorophenylhydrazone - MOPS morpholinopropanesulfonic acid - TPP⁺ tetraphenylphosphonium cation - EDTA ethylenediaminetetraacetic acid - pH transmembrane pH gradient (pH_in-pH_out) - transmembrane electrical potential difference     

Fermentative production of 1,3-propanediol from glycerol by Clostridium butyricum up to a scale of 2m3

Summary The conversion of glycerol to 1,3-propanediol (PD) by Clostridium butyricum DSM 5431 was studied in anaerobic culture. Growth and product formation were optimal at pH = 7.0 and T = 35° C, while aeration rate and stirrer speed were found to have no significant influence. As increasing amounts of initial glycerol led to inhibition of growth, cultivations were done in fed-batch operation. Comparative cultivations were carried out in an air-lift (ALR) and a stirred-tank reactor (STR) having equal working volumes (V _L = 30 l) and no difference in product formation was found. The process was scaled up to reactor sizes of 1.2 m³ (ALR) and 2.0 m³ (STR). The same results were obtained irrespective of reactor volume as well as reactor type (STR/ALR). PD concentrations of approximately 50–58 g·l^–1 and overall productivities of 2.3–2.9 g·l^–1 ·h^–1 could be reached. Offprint requests to: W.-D. Deckwer     

Influence of cultivation and induction conditions on β-lactamase production in Acinetobacter calcoaceticus

Summary The formation and localization of the -lactamase of Acinetobacter calcoaceticus CCM 5593 is strongly affected by cultivation and induction conditions. Optimal parameters for enzyme yield are cultivation on minimal salts medium with acetate (10 g·1^–1) as carbon source and addition of yeast extract (5–10 g·l^–1), induction by cefotaxime (50g·ml^–1) immediately after inoculation and growth for 24 h at 25° C. The strain forms a basal level of -lactamase constitutively [70 units (U)·g^–1]. Nearly all of this was found to be cell-bound. However, -lactamase activity additionally produced after induction (up to 500 U·g^–1 wet bacteria) was located in the culture medium (up to 96%). This unusual localization is a special feature of A. calcoaceticus and is not attributed to cell lysis. Offprint requests to: P. Borneleit     

Assembly of 60S ribosomal subunits is perturbed in temperature-sensitive yeast mutants defective in ribosomal protein L16.

Temperature-sensitive mutants defective in 60S ribosomal subunit protein L16 of Saccharomyces cerevisiae were isolated through hydroxylamine mutagenesis of the RPL16B gene and plasmid shuffling. Two heat-sensitive and two cold-sensitive isolates were characterized. The growth of the four mutants is inhibited at their restrictive temperatures. However, many of the cells remain viable if returned to their permissive temperatures. All of the mutants are deficient in 60S ribosomal subunits and therefore accumulate translational preinitiation complexes. Three of the mutants exhibit a shortage of mature 25S rRNA, and one accumulates rRNA precursors. The accumulation of rRNA precursors suggests that ribosome assembly may be slowed in this mutant. These phenotypes lead us to propose that mutants containing the rpl16b alleles are defective for 60S subunit assembly rather than function. In the mutant carrying the rpl16b-1 allele, ribosomes initiate translation at the noncanonical codon AUA, at least on the rpl16b-1 mRNA, bringing to light a possible connection between the rate and the fidelity of translation initiation.     

Chemical characterization by protein sequence analysis of the bovine estrogen receptor

Tryptic peptides generated from bovine estrogen receptor have been fractionated and purified using microbore column high performance liquid chromatography. Sequence analysis performed on six of these peptides, derived from diverse structural regions of the receptor protein, yielded 73 unique assignments corresponding to approximately 12% of the molecule. The amino acid sequences of these peptides displayed a high degree of similarity with corresponding sequences from estrogen receptors of mammalian origin, but were only moderately conserved in receptors from non-mammalian species. The sequenced residues of one tryptic peptide, positioned in the estrogen binding domain, were fully conserved in all estrogen receptors.