双碳源单细胞蛋白间歇培养及流加培养的动力学模型

应用非结构的逻辑增殖模型研究了两种酵母的单碳源和双碳源单细胞蛋白间歇培养的动力学,用改进的逻辑增殖模型研究了双碳源流加培养过程的动力学,从实验数据拟合了动力学模型参数,模型计算值与实验数据吻合良好。     

Preparation of coenzymic activity of soluble polyethyleneimine-bound NADP+ derivatives.

Alkylation at N-1 of the NADP+ adenine ring with 3,4-epoxybutanoic acid gave 1-(2-hydroxy-3-carboxypropyl)-NADP+. Enzymic reduction of the latter, followed by alkaline Dimroth rearrangement and enzymic reoxidation, gave N6-(2-hydroxy-3-carboxypropyl)-NADP+. On the other hand, bromination at C-8 of the NADP+ adenine ring, followed by reaction with the disodium salt of 3-mercaptroproionic acid, gave 8-(2-carboxyethylthio)-NADP+. Carbodimide coupling of the three carboxylic NADP+ derivatives to polyethyleneimine afforded the corresponding macromolecular NADP+ analogues. The carboxylic and the polyethyleneimine derivatives synthesized have been shown to be co-enzymically active with yeast glucose-6-phosphate dehydrogenase, liver glutamate dehydrogenase and yeast aldehyde dehydrogenase. The degree of efficiency relative to NADP+ with the three enzymes ranged from 17% to 100% for the carboxylic derivatives and from 1% to 36% for the polyethyleneimine analogues. On comparing the efficiences with the three enzymes of the N-1 derivatives to the one of the corresponding N6 anc C-8 analogues, the order of activity was N-1 greater than N6 greater C-8, except in the case of the carboxylic compounds with glutamate dehydrogenase, where this order was inverted. None of these modified cofactors were active with pig heart isocitrate dehydrogenase.     

A simplified radioenzymatic assay for dihydrofolate reductase using [3H]dihydrofolate

This report describes a simple method to measure the activity of dihydrofolate reductase using the substrate [³H]dihydrofolate, which is generated by preincubation of [³H]folic acid for 10 min with dithionite before the enzymatic reaction. The procedure then measures the direct reduction of [³H]dihydrofolate to [³H]tetrahydrofolate by coprecipitating the unreduced substrate with excess unlabeled folic acid and acidified zinc sulfate. The advantage of this method is that [³H]dihydrofolate, which is not commercially available, can be generated from high specific activity [³H]folic acid, which is commercially available, immediately before initiating the enzymatic reaction. By this modification, the two important advantages of radioenzymatic assays for dihydrofolate reductase can be more easily exploited; namely, increased sensitivity because much less substrate need be used, and the ability to measure enzyme activity in crude tissue preparations without interference by precipitating proteins or nucleotide oxidases.     

Turning in MFB-lesioned rats and antagonism of neuroleptic-induced catalepsy after lisuride and LSD.

The effects of lisuride, d-lysergic acid diethyl amide (LSD) and apomorphine were studied in rats with unilateral destruction of nigro-striatal nerve terminals either with 6-hydroxydopamine (6-OHDA) or 5, 6-dihydroxytryptamine (5,6-DHT). Lisuride at the dose of 50 μg kg^?1 i.p. induced contralateral turning for more than 4 hours while the circling induced by LSD (200 μg kg^?1) and apomorphine (1 mg kg^?1) persisted for only one hour. Lisuride, a compound stimulating both dopamine (DA) and 5-hydroxytryptamine (5-HT) receptors induced a more intense turning in 6-OHDA than in 5,6-DHT lesioned rats. This might indicate a modulation of 5-HT on rotational behavior. Haloperidol (1 mg kg^?1 i.p.) antagonized both lisuride- and LSD-induced turning. LSD, and much more persistently lisuride, counteracted the prochlorperazine-induced catalepsy. These findings correlate with the biochemical data indicating that lisuride is a very potent agonist at central dopaminergic receptors.     

Isolation and identification of β 1 → 2-d-glucans in extracellular polysaccharides of Rhizobium meliloti strain L5-30

Abstract Exopolysaccharides have been found as bound to R. meliloti cells (strain L5-30) or free in the culture medium; they consist of acidic and neutral polysaccharides. Bound and soluble neutral polysaccharides were identified as β 1 → 2 linked glucans with an average M _r value of 4000 to 6000.     

Studies on the adenosine 3′,5′-monophosphate-dependent protein kinase of Blastocladiella emersonii

Using a combination of Chromatographic and sucrose density gradient techniques under carefully controlled conditions of pH and protease inhibitors, we demonstrate that there is only one form of adenosine 3′,5′-monophosphate-dependent protein kinase in the cytosol fraction of the Blastocladiella emersonii zoospore. If any of these conditions are omitted during extract preparation, one obtains what are apparently multiple forms of the enzyme, which are in reality artifacts due to extensive endogenous proteolytic activity. This endogenous protease is stimulated by alkaline pH and inhibited by antipain. The zoospore protein kinase is similar to type II protein kinase from mammalian cells in several aspects including Chromatographic behavior on DEAE-cellulose column, conditions for subunit dissociation and reassociation, as well as the molecular weight value of the regulatory subunit.     

Veratridine-stimulated central synapses in culture: A quantitative ultrastructural analysis

Synapses in explant cultures of fetal rat neocortex at day 18 in vitro were stimulated by veratridine (10^?4M) for 20 min. The cultures were subsequently processed for electron microscopy and the synapses were analyzed by quantitative techniques, incorporating set mathematical treatment. The mean values of area, perimeter, and form factor of the presynaptic elements significantly increased following veratridine stimulation, compared to the values of control synapses. The length of the postsynaptic thickening also increased, while synaptic curvature did not change significantly in the veratridine group. A fivefold reduction was observed in the mean number of synaptic vesicles per presynaptic element and in the vesicle-terminal area ratio, following veratridine stimulation. The cytoplasm-terminal area ratio and the occurrence of vacuoles/cisternae significantly increased after veratridine application. Planar measurement of membranes (boundary length) of different presynaptic organelles revealed that the total membrane did not change significantly in the veratridine group. The data indicated an increase in volume and swelling of the pre- and postsynaptic elements, considerable depletion of synaptic vesicles, and preservation of the total presynaptic membrane following veratridine stimulation in nerve tissue culture.     

Effect of vitamin B3-active compounds on the content of free and combined gamma-aminobutyric acid and glutamic acid in the brain of mice

The bound and free GABA and glutamic acid content in the brain of F1 (CBA X C57B1/6) hybrid mice was investigated by the Eliott method. A tendency to a decrease of GABA and glutamate content in the brain with their practically constant bound/free ratio was observed 24 h after calcium-D-pantothenate injections (150 mumole/kg, 9 injections for 3 days). Calcium-D-homopantothenate injected in the same way caused a significant decrease in the GABA content, and a sharp drop of the bound/free GABA ratio. The effect is not associated with the influence of calcium ions in the composition of the injected compounds.