Growth of Trichosporon cutaneum under oxygen limitation: kinetics of oxygen uptake

The relationship between oxygen concentration and growth rate in the yeast Trichosporon cutaneum was studied. In order to establish the conditions for purely oxygen-limited growth, the cells were first grown in a carbon-limited chemostat, and kinetic parameters determined. The cells were then grown in an oxygen-limited chemostat at different dilution rates yielding different oxygen uptake rates. The steady-state dissolved oxygen tension was found at each dilution rate and the corresponding equilibrium dissolved oxygen tension was found at each dilution rate and the corresponding equilibrium dissolved oxygen concentration determined in the effluent medium. The relationship between oxygen concentration and growth rate followed Monod-type kinetics with an apparent K(O) of 4.38 x 10(-6)M.     

Cloning, pharmacological characteristics and expression pattern of the rat GABAA receptor alpha 4 subunit.

A cDNA of rat brain encoding the GABAA receptor alpha 4 subunit has been cloned. Recombinant receptors composed of alpha 4, beta 2 and gamma 2 subunit bind with high affinity the GABA agonist [3H]muscimol and the benzodiazepine 'alcohol antagonist' [3H]Ro 15-4513, but fail to bind benzodiazepine agonists. The alpha 4 subunit is expressed mainly in the thalamus, as assessed by in situ hybridization histochemistry, and may participate in a major population of thalamic GABAA receptors. The alpha 4 mRNA is found at lower levels in cortex and caudate putamen, and is rare in cerebellum.     

Racemization of the aqua-{N-salicylidene-(S)-alaninato}copper(II) by reaction with potassium cyanate

Copper(II) N-salicylidene-(S)-alaninate trihydrate reacting as the S-enantiomeric parent compound with KOCN in hot diluted methanol yielded by slow crystallisation from the cooled reaction mixture (in the course of 1 day) the racemic product K[Cu{sal-(RS)-ala}(NCO)]. The parameters of the axial type EPR spectrum in X-band region and the LF band position in the electronic spectrum are typical of an axially distorted square pyramidal coordination of the Cu(II) atom in this complex. The spectral properties of the complex cuprate prepared and its basal crystallographic data are consistent with those of the earlier studied¹⁵ K₂[Cu₂{sal-(RS)-ala}₂(μ-NCO)₂] synthetized by using [Cu{sal-(RS)-ala}(H₂O)].H₂O as the racemic parent complex in the reaction mixture with KOCN.     

Histidine utilization by Alcaligenes eutrophus: Regulation of histidase formation under heterotrophic conditions of growth

Histidine supported good growth of Alcaligenes eutrophus strain H 16 as a nitrogen source, but only poor growth as a carbon and energy source. The facultative chemolithoautotrophic bacterium was also able to utilize urocanic acid, the first intermediate of histidine catabolism. The products of histidine degradation were ammonium, formate and glutamate. Three enzymes of the pathway, histidase, urocanase and formiminoglutamate hydrolase, were present in histidine-grown cells. Two types of spontaneous mutants, derived from the wild type, were characterized by an increased growth rate on histidine. One of these types was found to produce histidase constitutively and at a higher activity compared with the parental strain. The second type of mutant had apparently gained an improved histidine uptake system, which is supposed to be growth rate-limiting in the wild type. From the physiological studies the conclusion was drawn that the control of histidine-degrading enzymes is based on induction by urocanate and catabolite repression by carbon sources supporting fast growth, such as succinate or pyruvate. Ammonium was found not to affect catabolite repression, however, we obtained evidence that histidine uptake is subject to a nitrogen control.Abbreviation CTAB hexadecyltrimethylammonium bromide     

Isethionate and taurine transport sites at brain cell membranes: Influx studies with brain slices

The influx of [¹⁴C]isethionate (ISA) into rat brain slices was studied with and without taurine. This influx was relatively rapid, but took place largely by a non-saturable, passive mechanism, which transferred much less ISA into the brain cells than taurine. Taurine inhibited the influx of ISA competitively (K _m=50 and 100 mol/l) at low ISA concentrations, and ISA that of taurine non-competitively (V=200 and 400–700 mol×min^–1×kg^–1 wet weight) at high taurine concentrations. It thus appears that ISA and taurine may have a small number of common transport sites at brain cell membranes, but these are apparently of little significance for the total transport of ISA.     

Comparison of Four Enrichment Media in the Recovery of Campyloracter Jejuni

The effectiveness of 4 enrichment media for the recovery of low levels of inoculated cells of Campylobacter jejuni was evaluated. The media contained antibiotics or antibiotics and bile acids as selective compounds. Three of the media recovered most of the inoculated low numbers of 6 C. jejuni strains. In the 3 media the growth rate of 3 strains, indicated by the increase in the log number of cells during 24 h or 48 h incubation at 42 ° C, was about the same as in the control medium without selective compounds. The same 3 media also recovered a low number of Campylobacter cells from artificially contaminated raw milk or ground meat samples. The enrichment medium B containing 40 I.U. Colistin, 5 μg novobiocin, 2 mg Na-cholic acid and 50 mg cycloheximide per ml was inhibitory for most Campylobacter strains studied.