Central neural control of pineal melatonin synthesis in the rat

To investigate a possible central neural influence on nocturnal pineal metabolic activity in rats, frontal transsections of the stria medullaris thalami were conducted. Enzymes involved in melatonin synthesis, i.e. N-acetyltransferase and hydroxyindole-O-methyl-transferase, exhibited reduced activities in operated animals when compared to controls. These results indicate a modulatory role of central structures on nocturnal pineal indole metabolism.     

Intrinsic and extrinsic neural and neurohumoral control of the decapod heart

The intra-cardiac nervous system of the decapod heart is composed of large and small ganglionic cells (LGCs and SGCs) and axons of extrinsic cardio-acceleratory and-inhibitory neurons (CAs and CIs). Candidate neurotransmitters for the neurons have been determined by pharmacological, cytochemical and immunocytochemical tests. SGCs may be cholinergic, LGCs and CAs are probably dopaminergic, and CIs are GABAergic. Serotonin and octopamine were cardio-excitatory neuromodulators of the heart. Proctolin, crustacean cardio-active peptide (CCAP), red pigment concentrating hormone (RPCH), and FMRFamide also had modulatory actions on the heart. Proctolin was the most potent peptide, which acted primary on the cardiac ganglion. Insect adipokinetic hormones had little effect on the heart.     

Central neural control of pineal melatonin synthesis in rat

Summary To investigate a possible central neural influence on nocturnal pineal metabolic activity, frontal transsections of the stria medullaris thalami were conducted. Enzymes involved in melatonin synthesis, i.e. N-acetyltransferase and hydroxyindole-O-methyl-transferase, exhibited reduced activities in operated animals when compared to controls. These results indicate a modulatory role of central structures on noctural pineal indole metabolism.This study was supported by the Deutsche Forschungsgemeischaft and the Stifung Volkswagenwerk. The technical assistance provided by M. Henschel, I. v. Graevenitz and G. Schlich is gratefuly acknowledged.     

Effect of 6-amino-nicotinamide on the tolerance of mice to hypoxic hypoxia

Zusammenfassung Eine einmalige Injektion von 6-Aminonicotinamid (6-ANA) steigerte die Sauerstoffman-gelresistenz von Mäusen in einer Atmosphäre mit 5% O₂ und 95% N₂. Hyperglykämie und Hypothermie, systemische Wirkungen von 6-ANA, konnten als Ursachen der gesteigerten Resistenz ausgeschlossen werden. Es wird deswegen vermutet, dass 6-ANA die anaerobe Utilisation von Glucose im Gehirn fördert.     

Microsphere measurement of myocardial capillary bed in hypoxic rats

Summary Rats exposed to hypobaric hypoxia for 24 h showed a significant increase in the number of perfused capillaries and in the number of radioactive microspheres trapped in the coronary circulation.     

Erythropoietin but not VEGF has a protective effect on auditory hair cells in the inner ear

It has recently been shown that the oxygen-regulated factors erythropoietin (Epo) and vascular endothelial growth factor (VEGF) confer protection on different cells, including neuronal-derived ones. The receptors for Epo and VEGF are widely expressed in different organs. Since mammalian auditory hair cells can irreversibly be damaged by different agents, we aimed to identify otoprotective compounds. We focused on the role of Epo and VEGF in the inner ear and review the recent studies. Epo and its receptor are expressed in the inner ear. In vitro experiments on auditory hair cells showed a protective effect of Epo in ischemia- and gentamicin-induced hair cell damage. In contrast, an in vivo study using an animal model of noise-induced hearing loss showed a negative effect of Epo. Also VEGF and its receptors are expressed in the inner ear. Changes in the expression of VEGF or its receptors have been found in the cochlea after noise exposure, transcranial vibration and diabetic or aged animals. Until now, there are no studies about a direct effect of VEGF on auditory hair cells in vitro or in vivo. We could exclude a protective effect of VEGF on gentamicin-induced auditory hair cell damage in vitro. Thus, we conclude that Epo but not VEGF has a protective effect on auditory hair cell damage at least in vitro. (Part of a multi-author review.)     

Decreased survival time of insulin-treated mice subjected to hypoxic decompression

Résumé On a constaté que les souris traitées à l'insuline possèdent une sensibilité élevée à la décompression hypoxique. Ce résultat concorde avec l'hypothèse d'une relation inverse entre la quantité de glucose dans le sang et la sensibilité d'un hôte à une grande variété de «stressors».

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We thankA. Bundeally for assistance in this investigation, which was supported in part by Public Health Service Research Grant No. CC00223 from the National Communicable Disease Center through the Massachusetts Health Research Institute.     

Formation of gigantic mitochondria in hypoxic isolated perfused rat hearts

Zusammenfassung Herzen gesunder, erwachsener Ratten wurden mit Krebs-Henseleit-Bikarbonatlösung durchströmt (95% O₂5% CO₂). Bei künstlich herbeigeführter Hypoxie (95% N₂5% CO₂) erschienen die Herzmitochondrien innerhalb von 7 min bedeutend vergrössert und zu 25% miteinander verschmolzen.     

Hypoxia in the regulation of neural stem cells

In aerobic organisms, oxygen is a critical factor in tissue and organ morphogenesis from embryonic development throughout post-natal life, as it regulates various intracellular pathways involved in cellular metabolism, proliferation, survival and fate. In the mammalian central nervous system, oxygen plays a critical role in regulating the growth and differentiation state of neural stem cells (NSCs), multipotent neuronal precursor cells that reside in a particular microenvironment called the neural stem cell niche and that, under certain physiological and pathological conditions, differentiate into fully functional mature neurons, even in adults. In both experimental and clinical settings, oxygen is one of the main factors influencing NSCs. In particular, the physiological condition of mild hypoxia (2.5–5.0% O₂) typical of neural tissues promotes NSC self-renewal; it also favors the success of engraftment when in vitro-expanded NSCs are transplanted into brain of experimental animals. In this review, we analyze how O₂ and specifically hypoxia impact on NSC self-renewal, differentiation, maturation, and homing in various in vitro and in vivo settings, including cerebral ischemia, so as to define the O₂ conditions for successful cell replacement therapy in the treatment of brain injury and neurodegenerative diseases.     

The formation of the front part of the neural tube

Zusammenfassung Die Ontogenese des Zentralnervensystems durchläuft drei frühe Entwicklungsphasen: Proneuromerie, Neuromerie und Postneuromerie. Danach folgen: distale Zellmigrationen in die Neuralrohrwand. Sämtliche Phasen sind mit der Mitosenaktivität korreliert.