Assimilation of ammonia and growth of biotin deficient Aspergillus nidulans.

Biotin deficiency in Aspergillus nidulans has been found to increase the uptake of ammonium ions, associated with a marked increase in the activity of NADP-linked glutamate dehydrogenase, which is found to be the major route of ammonia assimilation in this culture. The results obtained are discussed with respect to the growth of Aspergillus nidulans during biotin deficiency.     

Regulation of ammonia uptake inAspergillus nidulans

Summary The ammonia uptake inA. nidulans was found to be linear for about 20 min, and was proportional up to 1.5 mg/ml dry cell density. The transport of ammonia does not involve energy. Normal and biotin deficientA. nidulans showed an identical K_m-values of 10.26×10^–5 M ammonia for uptake. The uptake of ammonium ion has been shown to be regulated by the intracellular concentration of ammonia.Acknowledgment. The award of research fellowship by the Govt of India, Department of Atomic Energy, Bombay, to JDD is acknowledged.     

Regulation of glucose transport in Aspergillus nidulans.

Pyruvate and acetate inhibited the uptake of glucose by Aspergillus nidulans; although there were significant variations in glucose uptake rate, the intracellular concentration of acetate was almost identical in biotin-supplemented, normal and deficient cells. The in vitro activity of glucose-binding protein was not affected by biotin, avidin, acetate or acetyl-CoA.     

Regulation of glucose transport in Aspergillus nidulans

Summary Pyruvate and acetate inhibited the uptake of glucose by Aspergillus nidulans; although there were significant variations in glucose uptake rate, the intracellular concentration of acetate was almost identical in biotin-supplemented, normal and deficient cells. The in vitro activity of glucose-binding protein was not affected by biotin, avidin, acetate or acetyl-CoA.J. D. Desai gratefullt acknowledges the receipt of Research Fellowship from the Govt. of India, Department of Atomic Energy, Bombay.     

Effects of ethidium bromide in diploid and duplication strains of Aspergillus nidulans.

Unstable duplication and diploid strains of Aspergillus nidulans were treated with ethidium bromide, and it was shown that this drug reduces the number of sectors produced by such strains. The mechanisms which could be responsible for the partial stabilization of the strains are discussed and it is suggested that a similar mechanism is responsible for the production of sectors in both strains. It is also suggested that ethidium bromide could be useful for the reduction of instability of industrial strains.     

Effects of ethidium bromide in diploid and duplication strains of Aspergillus nidulans

Summary Unstable duplication and diploid strains of Aspergillus nidulans were treated with ethidium bromide, and it was shown that this drug reduces the number of sectors produced by such strains. The mechanisms which could be responsible for the partial stabilization of the strains are discussed and it is suggested that a similar mechanism is responsible for the production of sectors in both strains. It is also suggested that ethidium bromide could be useful for the reduction of instability of industrial strains.Acknowledgment. The authors are thankful to the National Council for the Development of Science and Technology (CNPq) for financial assistance.     

Assimilation of ammonia and growth of biotin deficientAspergillus nidulans

Summary Biotin deficiency inAspergillus nidulans has been found to increase the uptake of ammonium ions, associated with a marked increase in the activity of NADP-linked glutamate dehydrogenase, which is found to be the major route of ammonia assimilation in this culture. The results obtained are discussed with respect to the growth ofAspergillus nidulans during biotin deficiency. J. D. Desai gratefully acknowledges the receipt of a research fellowship from the Government of India, Department of Atomic Energy, Bombay.     

Volatile metabolites of aspergilli in relation to spore germination of some keratinophilic fungi

Summary The effect of volatile metabolites produced by 8 Aspergilli (i.e.,Aspergillus candidus, A. chevalieri, A. flavus, A. fumigatus, A. nidulans, A. niger, A. ochraceous andA. tamarii) on spore germination were tested againstAuxarthron conjugatum, Chrysosporium pannicola, Keratinomyces ajelloi andMicrosporum gypseum. The volatile metabolites inhibited the spore germination of all the test fungi.Acknowledgment. The authors thank Professor G.P. Mishra for the use of the facilities and S.K.D. acknowledges the fellowship award by I.C.M.R. New Delhi.     

Cerebral ammonia production during hypoglycemia in the newborn calf.

The effect of insulin hypoglycaemia on cerebral blood flow, and cerebral metabolic rates of glucose, oxygen and ammonia was investigated in the unanaesthetized newborn calf. A net loss of ammonia from the brain occurred during hypoglycaemia, and was greater in convulsing than in comatose animals.     

Cerebral ammonia production during hypoglycaemia in the newborn calf

Summary The effect of insulin hypoglycaemia on cerebral blood flow, and cerebral metabolic rates of glucose, oxygen and ammonia was investigated in the unanaesthetized newborn calf. A net loss of ammonia from the brain occurred during hypoglycaemia, and was greater in convulsing than in comatose animals.Acknowledgments. The expert assistance of Mr P.M.M. Bircham and Miss B.N. O'Connor is gratefully acknowledged. This work was supported by the Medical Research Council.     

Transfer of isolated nuclei into protoplasts of Aspergillus nidulans.

Nuclei were isolated from protoplasts of a haploid auxotrophic Aspergillus nidulans strain. Transformation of protoplasts prepared from a complementary haploid auxotrophic strain with these purified nuclei resulted in both heterokaryotic and diploid colonies. The nutritionally-complementing colonies appeared at a frequency of 5 x 10(-7) to 10(-8).     

High-frequency fusion of fungal protoplasts

Zusammenfassung Es gelang, die intraspezifische Protoplastfusion vonAspergillus flavus, A. nidulans, A. niger, Penicillium frequentans undP. ramigena mit grosser H?ufigkeit zu verwirklichen. Die Fusionsh?ufigkeit wurde durch Komplementation von Mangelmutanten festgestellt.

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The authors thank Dr.M. Czakó, Dr.M. Pesti and Mr.L. Manczinger for producing and characterizing some of the required mutants, andéva Sziráki andMagdolna Romvári for skilful technical assistance.     

Use of 3H-QNB in the isolation of plasma membrane from smooth muscle of the urinary bladder: effect of oxalate on calcium uptake by the membrane fractions

Specific binding of tritiated quinuclidinyl benzilate (3H-QNB) to surface membrane muscarinic receptors was utilized to identify plasma membrane (PM) fractions from smooth muscle of the rabbit urinary bladder. Accumulation of 3H-QNB in the PM fraction was 4-5-fold higher than that in fractions of endoplasmic reticulum (EM) or mitochondria (M). A similar pattern of distribution was found for 5'-nucleotidase. 3H-QNB binding therefore appears to be a suitable marker for plasma membrane of the urinary bladder. Data on ATP-dependent calcium uptake by PM and ER fractions showed that oxalate highly potentiated calcium uptake by both fractions and consequently this feature cannot be used to identify ER fractions specifically.     

苯酚在氨氮体系中的氧化降解研究

研究了氨氮存在下次氯酸钠处理苯酚模拟废水的氧化特性,探讨了苯酚在氨氯体系中的反应途径。实验结果表明:在含氨氮的苯酚废水中加入次氯酸钠,氨氮将与苯酚发生竞争反应。折点加氯曲线表现为当氯与氨氮质量比由5.35上升到27.67时,氨氮去除率的变化趋势滞后;而余氯量则不断减小,没有折点出现。随着氨氮浓度增加,苯酚的氧化降解受到抑制:一方面,苯酚的去除率不断下降;另一方面,体系中检测到一系列氯酚中间产物,其生成量和种类先增加后减少。HPLC分析结果显示体系中生成的氯酚中间产物至少有2种(2-氯酚和4-氯酚),至多有5种(2-氯酚、4-氯酚、2,6-二氯酚、2,4-二氯酚和2,4,6-三氯酚)。其中,2-氯酚和4-氯酚是导致三卤甲烷产生的最有效前体物质,而2,6-二氯酚、2,4-二氯酚和2,4,6-三氯酚则是生成卤乙酸的高活性物质。实验结果对次氯酸钠处理含氨氮的难生化或有毒有机废水具有一定的参考价值。     

Ectoprotein kinase-mediated phosphorylation of FAT/CD36 regulates palmitate uptake by human platelets

Glycoprotein IV (FAT/CD36) has been shown to be phosphorylated by a cAMP-dependent, platelet membrane-bound ectokinase. In this study, we demonstrate that ectophosphorylation of FAT/CD36 regulates initial palmitate uptake. This is the first time that short-term regulation of the activity of a long-chain fatty acid carrier could be shown. Phosphorylation of FAT/CD36 was paralleled by a significant decrease in initial palmitate uptake by morphologically and functionally intact platelets. Maximum inhibition of palmitate uptake was achieved at 0.5 nM extracellular ATP, being significantly decreased to 72% compared to the control. Inhibition of palmitate uptake was abolished by co-incubation with the specific protein kinase A inhibitor peptide PKI or with β,γ-methylene-ATP, and was reversible upon addition of alkaline phosphatase. An extracellular ATP concentration above 5 μM completely prevented the ectophosphorylation-mediated inhibition of palmitate uptake. We conclude that FAT/CD36-mediated palmitate uptake by human platelets is short-term regulated via cAMP-dependent ectophosphorylation of FAT/CD36. Received 18 July 2002; received after revision 29 August 2002; accepted 19 September 2002 RID="*" ID="*"Corresponding author.     

Metaraminol uptake by human thrombocytes: A poor model for neuronal noradrenaline uptake

Summary The IC₅₀ of a number of antidepressants and related drugs on the uptake of 1-metaraminol and serotonin into human thrombocytes, and of noradrenaline and serotonin into rat midbrain synaptosomes were compared. In accordance with previous reports, it was found that platelets, provide a good model for the study of neuronal uptake of serotonin. Platelet uptake of 1-metaraminol, although correlated to some extent with noradrenaline uptake into synaptosomes, seems to be an unsatisfactory model for the neuronal uptake of the latter amine.     

Effect of L-methionine-DL-sulphoximine on the photoproduction of hydrogen byRhodospirillum rubrum

Summary The repression of photoproduction of hydrogen by ammonia could be relieved by L-methionine-DL-sulfoximine. In the absence of ammonia, hydrogen evolution was inhibited by concentrations of L-methionine-DL-sulfoximine higher than 0.1 mM.Acknowledgments. This work was supported by the Swiss National Foundation for Scientific Research, grant 4.048.0.76.04, National Research Program Energy.     

Proliferation and cell loss of human leukemic cell subpopulations in liquid culture

A kinetic study was performed on leukemic blasts from patients with acute myeloid leukemia, separated into 2 subpopulations by a specific density gradient. The growth curve and the [3H]-thymidine uptake were simultaneously analyzed. While cumulative nucleotide uptake fitted with the growth kinetics in the low-density fraction, such a concordance was not found in the high-density subpopulation. That indicated the occurrence of simultaneous growth and loss in the high density fraction, which could not be evaluated by a simple numerical determination.     

The ischemic and postischemic effect on the uptake of neutral amino acids in isolated cerebral capillaries.

The uptake of some neurtral amino acids was investigated in cerebral microvessels isolated from brains of gerbils subjected to bilateral cerebral ischemia with and without various periods of recovery. A transiently increased capillary uptake of 3H-isoleucine, 14C-cycloleucine and 3H-phenylalanine was found in both conditions.     

The concentration of ammonia in the excreta of sixth instar larvae ofLamida moncusalis Walker (Pyralidae: Lepidoptera) during development

Summary The concentration of ammonia in the fresh and dry excreta ofLamida moncusalis Walker was determined. It was found that a large quantity of ammonia was lost from the excreta on drying. Ammonia is one of the major excretory products of the larva.5 September 1986Acknowledgment. We thank the State Committee on Science, Technology and Environment, Kerala, for the financial assistance.