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.     

Regulation of ammonia uptake in aspergillus nidulans.

The ammonia uptake in A. 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 deficient A. nidulans showed an identical Km-values of 10.26 X 10(-5) M ammonia for uptake. The uptake of ammonium ion has been shown to be regulated by the intracellular concentration of ammonia.     

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.     

High sensitivity of porcine cerebral arteries to endothelin

Summary The threshold concentration of endothelin to induce contractions in porcine cerebral arteries (anterior cerebral, Willis ring and basilar artery) was lower than those for coronary and renal arteries. The median effective concentrations (ED₅₀) of endothelin in cerebral arteries were also significantly lower than those for coronary and renal arteries. There was no significant difference in the sensitivity to endothelin among cerebral arteries, or between coronary and renal arteries. The maximal percentage of contractions induced by endothelin, as compared to that induced by 10^–1 M potassium chloride, was not significantly different between the arteries.     

Potassium transfer from brain to blood during sustained hyponatraemia in the newborn calf

Summary The effect of dilutional hyponatraemia on cerebral blood flow and oxygen consumption, and net transfer of K⁺ to the circulation from brain tissue drained by the sagittal sinus was investigated in anaesthetized calves. Cerebral blood flow decreased, and net transfer of K⁺ to the circulation increased during hyponatraemia.Acknowledgments. The expert assistance of Miss B.N. O'Connor, Miss D. McNaughton and Mr P.M.M. Bircham is gratefully acknowledged.     

Pentagastrin induction of acetylcholinesterase activity in cerebral cortex of rats

Summary A single injection of pentagastrin (500 g kg^–1) produced an immediate (within 15 min) and pronounced increment (about 50%) in the activity of acetylcholinesterase (AChE) in the cerebral but not in the cerebellar region of the brain. Pretreatment of rats with either actinomycin-D or cycloheximide did not fully abolish the pentagastrin-mediated stimulation of cerebral AChE activity.Acknowledgments. A.M. Nakhla is recipient of a postdoctoral research fellowship from Danida, Ministry of Foreign Affairs, Denmark. The project was in part supported by grants to A.P.N.M. from The Laegevidenskabelige Forskningsråd and Danida, Denmark.     

Changes in cAMP concentration in the rat preoptic area during synchronized and desynchronized sleep

Summary cAMP concentration was found to be significantly lower during desynchronized sleep than during synchronized sleep in the preoptic area of rats kept at normal laboratory temperature. No significant changes in cerebral cortex cAMP concentraion were observed in the same experimental conditions.This work was supported by grants from Consiglio Nazionale delle Ricerche and Ministero della Pubblica Istruzione.The authors wish to thank G. Mancinelli and L. Sabattini for technical assistance and M. Luppi for secretarial assistance.     

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。     

Effects of cerebral lateral,ventricular infusions of phloridzin on feeding and body weight in Gallus domesticus (L.)

Summary Contrary to earlier findings in rats, cerebral lateral ventricular infusions of 1×10^–3 M or 2×10^–3 M solutions of phloridzin at a rate of 2.5 l/min for 90 min had no significant stimulating effects on food intake and weight gain in hens and cocks. These different responses to intraventricular phloridzin might reflect a difference of sensitivity to the inhibitory action of phloridzin on glucose transport in cerebral cells or certain peculiarities of mechanisms controlling food intake in chickens.     

Drug action on adenylate kinase activity in cerebrospinal fluid of arteriosclerotic patients

Summary A manifest presence of adenylate kinase activity in cerebrospinal fluid was found in patients with cerebral arteriosclerosis. This activity was significantly higher during treatment with co-dergocrine (Hydergin^®) compared with the two periods before and after treatment.Acknowledgment. We are obliged to Mrs M. Hedström, for skilful technical assistance. This study was supported by a grant from the Södermanland Country Council. The study plan was approved by the Ethical Committy of Medical Faculty at the University of Uppsala.     

Effect of acetylcholine acetyl-hydrolase (E.C. 3.1.1.7) inhibition on the accumulation of pp' DDT in various brain regions of rats

Summary The concentration of pp' DDT given intraperitoneally in rats was determined in different brain regions. Maximum accumulation of pp' DDT was found in the corpus striatum, followed by cerebellum and cerebral cortex in that order; following pretreatment with paraoxon the concentrations of pp' DDT were increased in all brain regions studied. pp' DDT (1,1,1-trichloro-2,2-bis(4′-chlorophenyl ethane), used in the above studies was generously supplied by Montrose Chemical Corporation of California, USA. The authors are grateful to Mr M.Z. Hasan for analysis of the samples and to Sandoz, Basel, Switzerland for the gift of paraoxon.     

Plasma motilin levels in duodenal ulcer and effect of a truncal vagotomy and hypoglycaemia

Summary The identical response of plasma motilin levels, in duodenal ulcer patients and healthy controls, to a test meal and insulin induced hypoglycaemia, fail to demonstrate any significant abnormalities in motilin release. The close correlation between blood glucose and motilin suggest a possible role of this new hormone in carbohydrate metabolism.This work was made possible by a generous grant by the Wellcome Trust. The authors are indebted to Dr P. Mitznegg, Department of Pharmacology, University of Erlangen-Nuremberg (Germany) for his encouragement and aid in the development of the plasma motilin assay.     

Heterogeneous responses of canine basilar and middle cerebral arteries to serotonin at normal and high CO2 tension.

The responses of basilar arteries (BAs) to serotonin were attenuated by high PCO2 (86 +/- 1 mm Hg) and the pH matched acidotic solution (PCO2 37 +/- 1 mm Hg), whereas the responses of middle cerebral arteries (MCAs) were not. High PCO2 decreased the basal tone of both arteries, and the changes in basal tone due to high PCO2 were not influenced by 3 x 10(-7) M imipramine, 10(-5) M pargyline or 10(-4) M aspirin. The responses of BAs to serotonin were attenuated by high PCO2 in the presence of imipramine, pargyline and aspirin. The responses of MCAs to serotonin were not influenced by high PCO2 in the presence of pargyline and aspirin, but attenuated by high PCO2 in the presence of imipramine.     

‘Binding’ of glycine andγ-aminobutyric acid to synaptosomal fractions of 6 regions of the feline brain; effects of strychnine

Summary GABA (6×10^–6 M) binding to synaptosome-enriched fractions of cat CNS exhibited a clear rostro-caudal gradient, whereas glycine (6×10^–6 M) binding was greatest to particles of cerebellar cortex, and this was followed by medulla caudate nucleus cerebral cortex pons > corona radiata. Strychnine-SO₄ (10^–3 or 10^–4 M) inhibited the binding of GABA and glycine in all brain regions studied; at 10^–5 M this drug inhibited the binding of both GABA and glycine only to particles of the cerebral cortex.This study was supported by Centro Nacional Ramón y Cajal and Fundación Juan March. P. M. was a summer student from Eastern Nazarene College, Wollaston, Mass., USA.     

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.     

Origin of ammonia excreted by trout gill (Salmo gairdneri)]

In the perfused head of Trout the gills are the site of ammonia clearance which corresponds exactly to the appearance rate of ammonia in the external medium. Thus metabolic production of ammonia by the gill apparently does not participate to its excretion. Under ammonia-free Ringer perfusion however, endogenous production is observed and ammonia is excreted in both external and internal media.     

High K+-induced release of somatostatin from the cortical preparation of rat brain

Summary Release of endogenous somatostatin (SRIF) from the rat cerebral cortical slices incubated in Krebs-bicarbonate buffer was increased from the basal rate of 3.4±0.6% of the total SRIF content in 15 min at [K⁺]_o=5.6 mM, to 13.1±1.6% upon raising the [K⁺]_o to 56.6 mM. The high-K⁺ evoked SRIF release was absent when Ca⁺⁺ in the medium was replaced by Mn⁺⁺. The isolated synaptosomes from rat cerebral cortex contain 13.2±3.1 ng SRIF/mg protein compared to 0.33±0.01 ng/mg protein in the cortical tissue as a whole, suggesting that nerve terminals are the main source of the peptide released upon membrane depolarization.The study was supported by a grant from the Medical Research Council of Canada. Results of this work have been published in part as abstracts: Can. Physiol.9, 45 (1978), and Fedn Proc.37, 665 (1978).The authors are greatly indebted to Dr M. Gotz and the Ayerst Research Laboratories for the most generous supply of the synthetic somatostatin.     

Preliminary results on the abiotic synthesis of metalloporphyrins]

The possibility of obtaining metalloporphyrins in abiotic conditions was investigated. The direct formation of zinc-porphyrins in the reaction product obtained by exposing a mixture of methane, ammonia and water vapor to electrical discharges is reported.     

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.     

Biochemical and environmental perspectives on nitrogen metabolism in fishes

Catabolism of nitrogen-containing substances makes a major contribution to the oxidative metabolism in teleostean fishes. In this review, we focus on aspects of the formation, transport, detoxification and excretion of the two most important nitrogenous products of fishes: ammonia (NH₃ plus NH ₄ ⁺ ) and urea. While NH ₄ ⁺ makes up the bulk of nitrogenous waste, it is in equilibrium with the highly toxic NH₃. Ammonia is generated in the liver and excreted through branchial, surface and renal routes. Innocuous urea is derived through hepatic uricolysis or argininolysis and voided through kidney, gill, skin or faeces. Under conditions hampering the release of ammonia, such as exposure to exogenous ammonia, water limitation, or alkaline conditions, some teleosts detoxify ammonia through synthesis of urea by the ornithine-urea cycle in liver. Ammonia and possibly alanine are the prevalent vehicles of internal nitrogen transport. Glutamine is immaterial to interorgan nitrogen transport in fishes, but plays a transient role in the detoxification of ammonia by brain glutamine synthetase.