Endogenous γ-Hydroxybutyrate in Rat Brain Areas: Postmortem Changes and Effects of Drugs Interfering with γ-Aminobutyric Acid Metabolism

Abstract: The possibility that γ-hydroxybutyrate (GHB), a metabolite of γ-aminobutyric acid (GABA), may play a role in the CNS has recently come to attention. We describe here a sensitive and specific mass fragmento-graphic technique that allows the measurement of picomole amounts of GHB in single rat brain areas. Moreover, we show that GHB can accumulate postmortem, an effect that is blocked by the use of microwave irradiation to kill the animals. To understand further the relationship between GABA and GHB formation, we treated rats with drugs known to inferfere with GABA metabolism at different levels and concomitantly measured GABA and GHB in cerebral cortex and cerebellum. Isoniazide, which blocks the formation of GABA, also decreases GHB. Blockers of the catabolism of GABA, such as aminooxyacetic acid and γ-acetylenic GABA, increase GABA levels and decrease those of GHB. Sodium dipropylacetate increases both GABA and GHB, supporting the hypothesis that this effective antiepileptic drug also blocks in vivo the enzyme that converts succinic semialdehyde to succinic acid.     

The ACTH-interrenal axis in the freshwater stickleback,Gasterosteus aculeatus form leiurus

Summary The ACTH-interrenal axis of the freshwater stickleback has been examined with the fish in a variety of physiological conditions. A morphometric analysis of ACTH cell ultrastructure in spring animals revealed that the only change from the winter condition was a significant decrease in the amount of perinuclear RER. The interrenal gland responded to metopirone treatment by an increase in both nuclear and cell size, although only a high dose of metopirone could degranulate the ACTH cells. Morphometry of the ACTH cells from metopirone-treated animals showed a significant increase in the amount of RER and a significant decrease in the number of free ribosomes and secretory granules, compared with control animals maintained in freshwater. Such ultrastructural changes may be expected of a cell that is stimulated to increase its secretion of polypeptide hormone. The ACTH-interrenal axis also responded to 70% seawater, as this treatment increased the interrenal cell and nuclear sizes.     

快中子辐射对红豆草愈伤组织细胞结构影响的电镜观察(简报)

近年来植物愈伤组织无性变异系的诱导和选择,已成为植物细胞工程中十分活跃的领域,快中子、γ射线等电离辐射也已开始被用于愈伤组织抗性变异系的诱导。观察不同剂量电离辐射在诱发植物愈伤组织变异中对细胞结构的影响,对于探讨辐射诱变的细胞学机理     

Developmental Expression of Go in Neuronal Cultures from Rat Mesencephalon and Hypothalamus

The developmental expression of the alpha-subunit of Go was examined in neuronal cultures derived from rat mesencephalon (MES) and hypothalamus (HYP). These cultures were essentially free of contaminating glia and were maintained as a stable population for periods up to 3 weeks. Immunoblotting utilizing specific antisera against Go indicated that in neurons from both brain regions, membrane concentrations of Go increased dramatically during the first 2 weeks in vitro. Thereafter, increases in the amount of Go per neuron kept pace with increasing process (axons and dendrites) formation. Multiple forms of immunoreactive Go were detected in MES and HYP neurons, and the proportions of these forms changed between 4 and 14 days in culture. Finally, increasing neuron density significantly increased membrane levels of Go in MES but not HYP cultures.     

Extraction of melodies in behavioural sequences

A method is proposed that extracts a set of phrases, or “melodies”, from a behavioural sequence, using a technique for extracting and compressing chains based on Information Theory. These melodies are validated by reference to a statistical criterion. An application of this method to the analysis of the behavioural sequences of two groups of mice, the first observed during the day, the second during the night, is described. The advantages and the limitations of the method are discussed.     

Ecological and evolutionary consequences of the trophic polymorphism in Cichlasoma citrinellum (Pisces: Cichlidae)

The neotropical cichlid fish Cichlasoma citrinellum is polymorphic in the structure of its pharyngeal jaw apparatus and external morphology. The pharyngeal jaws are either gracile and bear slender, pointed teeth (papilliform) or robust with strong, rounded teeth (molariform). Molariform morphs have a ‘benthic’, and papilliform morphs a ‘limnetic’ body form. Furthermore, this species is also polychromatic, with yellow and black morphs. The molariform morphology of the pharyngeal jaw apparatus adapts the fish for cracking and feeding on snails. Based on analysis of stomach contents, 94% of the molariform morph ate snails whereas only 19%, of the papilliform morph did so. This result suggests that the morphs occupy different ecological niches. The morphology of the pharyngeal jaw apparatus does not correlate significantly with sex, but it does with body colouration (P<0.005). Cichlasoma citrinellum mate assortatively with their own colour; therefore a mating preference for colour may lead to genetic isolation of trophic morphs. The frequency of the molariform morph differs strikingly among populations of five Nicaraguan lakes and its abundance is correlated with the abundance of snails, the fishes' principal prey item. Among populations the frequency of molariform morphs decreases in the dry season. Morphology possibly changes reversibly within particular individuals between seasons. These results suggest that phenotypic plasticity and polymorphisms may be an adaptive characteristic of cichlid fishes. Patterns of intraspecific morphological variation match patterns of interspecific morphological diversification which suggests that universal developmental mechanisms canalize the possible expressions of morphology. The ability to respond morphologically to environmental shifts, in conjunction with genetically determined trophic polymorphisms and sexual selection via mate choice, could be the basis for speciation through intermediate stages of polymorphism of the impressive adaptive radiation of cichlid fishes.     

Alternative seed-handling strategies in primates: seed-spitting by long-tailed macaques (Macaca fascicularis)

Summary The seeds in fruits consumed by primates may be chewed and digested, swallowed and defecated intact, or separated from the flesh and spat out. We show by a combination of close field observations and experiments with caged animals, that long-tailed macaques (Macaca fascicularis) have a remarkably low threshold of 3–4 mm for swallowing seeds and also that wild macaques rarely break them. The seeds of 69% of the ripe fruit species eaten are spat out intact or cleaned outside the mouth and dropped. Seed-spitting significantly reduces the swallowed food bulk and may lessen the risk of releasing seed toxins during mastication. However, it requires that even small fruits are processed in the mouth one or a few at a time. We suggest that fruit storage in the cheek pouches of cercopithecine monkeys allows them to spit seeds individually without excessively slowing fruit intake while feeding on patchily distributed fruit. In contrast, Apes and New World monkeys apparently swallow and defecate most ripe seeds in their diet and colobine monkeys break and digest them, detoxifying seed defenses by bacterial fermentation.     

Natal dispersal in relation to population density and sex ratio in the field vole,Microtus agrestis

Summary In a sample of 240 juvenile field voles 8% of the males and 22% of the females reached sexual maturity within their natal home range. Among individuals retrapped as adults, 58% of males and 23% of females had dispersed, i.e. had moved more than one home range diameter. The mean distance moved for males (58.5 m) exceeded that for females (28.6 m). Male movement distances were negatively associated with total density, and with density of adult females, but not with male density. Female movements were not related to population density. There were no relation between sex ratio and distance moved. The distribution of distances moved for both males and females fit a geometrical distribution, suggesting the importance of competitive processes.     

Haematological disturbances and osmotic shifts in rainbow trout,Oncorhynchus mykiss (Walbaum) under acid and aluminium exposure

Summary Elevated values of haematocrit were observed in rainbow trout (Oncorhynchus mykiss) during combined acid and aluminium exposure. Possible causes of this, i.e., decreased plasma volume, swelling of erythrocytes, and/or mobilization of erythrocytes into the blood were investigated. Slight haematocrit increases (10–20%) during mild acid stress (pH 5.0, 25 mol Ca²⁺·1^-1) were mostly caused by osmotic shifts. Both swelling of erythrocytes rocytes and a significant decrease of the plasma volume were demonstrated in fish at pH 5.0. These osmotic disturbined were greater during acid exposure (pH 5.0) combined with Al (60 g·1^-1; 200 g·1^-1). In addition, numbers of erythrocytes increased by 40% compared to acid exposure, which contributed to the severe haematocrit rise (35%) during Al exposure. A contraction of the spleen releasing erythrocytes into the blood is suggested to occur as an adrenergic response to hypoxia, which is observed in fish acutely exposed to Al.Abbreviations BV blood volume - ECFV extracellular fluid volume - ICFV intracellular fluid volume - ISFV interstitial fluid volume - MCHC mean cell haemoglobin concentration - MCV mean cell volume - PV plasma volume     

Electrooptical studies on proton-binding and -release of bacteriorhodopsin

Electric field induced pH changes of purple membrane suspensions were investigated in the pH range from 4.1 to 7.6 by measuring the absorbance change of pH indicators. In connection with the photocycle and proton pump ability, three different states of bacteriorhodopsin were used: (1) the native purple bacteriorhodopsin (magnesium and calcium ions are bound, the M intermediate exists in the photocycle and protons are pumped), (2) the cation-depleted blue bacteriorhodopsin (no M intermediate), and (3) the regenerated purple bacteriorhodopsin which is produced either by raising the pH or by adding magnesium ions (the M intermediate exists). In the native purple bacteriorhodopsin there are, at least, two types of proton binding sites: one releases protons and the other takes up protons in the presence of the electric field. On the other hand, blue bacteriorhodopsin and the regenerated purple bacteriorhodopsin (pH increase) show neither proton release nor proton uptake. When magnesium ions are added to the suspensions; the field-induced pH change is observed again. Thus, the stability of proton binding depends strongly on the state of bacteriorhodopsin and differences in proton binding are likely to be related to differences in proton pump activity. Furthermore, it is suggested that the appearance of the M intermediate and proton pumping are not necessarily related.