Relative importance of temporal and spatial heterogeneity in the zooplankton community of an artificial reservoir

Zooplankton samples were collected monthly at three stations in Ogochi Reservoir during 1980, and the temporal and horizontal variations in the density of dominant taxa were evaluated by a standard 2-way ANOVA with random effects. The analysis revealed that horizontal is greater than temporal variation in the warm water season (> 18 °C), whereas temporal variation is greater in the cold water season (< 18 °C). Horizontal heterogeneity of the zooplankton community found in the warm water season seems to be associated with differences in site-specific conditions.     

Regional brain GABA metabolism and release during hepatic coma produced in rats chronically treated with carbon tetrachloride

Hepatic coma was induced in rats chronically treated with CCl₄, by means of a single injection of ammonium acetate. The activities of glutamate decarboxylase (GAD) and GABA transaminase (GABA-T), as well as the synaptosomal uptake and release of [³H]GABA, were measured in the following brain areas of the comatose rats: cortex, striatum, hypothalamus, hippocampus, midbrain and cerebellum. Hepatic coma was associated with a general decrease of GAD activity, whereas GABA-T activity was diminished only in the hypothalamus, striatum and midbrain. During hepatic coma, the K⁺-stimulated [³H]GABA release was notably diminished in the striatum and cerebellum, whereas a significant increase was observed in the hippocampus. [³H]GABA uptake increased in most regions after CCl₄ treatment, independently of the presence of coma. The results indicate that GABAergic transmission seems to be decreased in most cerebral regions during hepatic coma.     

Energy metabolism in glutamatergic neurons,GABAergic neurons and astrocytes in primary cultures

Several aspects of energy metabolism (glucose utilization, lactate production,¹⁴CO₂ production from labeled glucose, glutamate or pyruvate, oxygen consumption and contents of ATP and phosphocreatine) were measured in cerebellar granule cells (glutamatergic) in primary cultures and compared with corresponding data for cerebral cortical neurons (mainly GABA-ergic) and astrocytes. Cerebellar granule cells and astrocytes were metabolically more active than cerebral cortical neurons. Glutamate which is utilized as a major metabolic fuel as astrocytes and, to a lesser extent, in cerebral cortical neurons, was virtually not oxidized in cerebellar granule cells.Special Issue dedicated to Prof. Holger Hydén.     

Isolation of a cAMP-requiring mutant in Escherichia coli K-12: evidence of growth regulation via N-acetylglucosamine metabolism controlled by cAMP

Abstract An adenylate cyclase gene ( cya ) mutant was mutagenized and an adenosine 3,5-cyclic monophosphate (cAMP)-requiring mutant (KM8161) was obtained on Davis minimal medium containing glucose in the presence or absence of cAMP. KM8161 also required N -acetylglucosamine for its growth instead of cAMP. Furthermore, the mutant could use neither glucosamine nor N -acetylglucosamine as the carbon source. These results indicate that the cAMP-requiring property is due to multiple mutations of a few genes involved in amino sugar metabolism in addition to cya . By genetic analysis of KM8161, one gene, which was tentatively termed cidA and located near 2 min on the chromosomal map, proved to be defective. Reversion of cidA mutation in KM8161 resulted in recovery of not only the cAMP-requiring phenotype but also non-utilization of amino sugars. When both cAMP and N -acetylglucosamine or glucosamine were added to the culture medium for KM8161, only N -acetylglucosamine could be utilized as the carbon source. These studies s strongly suggest that the cidA or cya mutation in KM8161 causes deficiency in different stages of amino sugar metabolism and the regulatory circuit of growth by cAMP is mediated via control of N -acetylglucosamine metabolism.     

The effects of cultural conditions on growth and secondary metabolism in Streptomyces thermoviolaceus

Abstract Granaticin, an isochromate quinone antibiotic is synthesized as a secondary metabolite by Streptomyces thermoviolaceus . Antibiotic productivity was investigated under a variety of cultural conditions, including complex and defined media, mesophilic and thermophilic temperatures and a variety of sole carbon sources. In a defined medium growth was supported, to varying extents, by different carbon sources and in most cases granaticin production was observed. Highest biomass and granaticin yields were obtained when cultures were grown in the presence of xylan, fructose, glutamate or proline as carbon source. Changes in pH during growth affected both the timing and extent of granaticin production.     

Are galling insects better protected against parasitoids than exposed feeders?: a test using tenthredinid sawflies

ABSTRACT.

• 1 Data mostly from the published literature were used to assess the effect of galling on the number of parasitoid species per host species in the phylogeny of nematine sawflies from free external feeders (colonial and solitary) to leaf gallers and shoot gallers.
• 2 The strongest effects of galling were the total elimination of the species-rich cocoon-attacking guild of parasitoids, and eonymphal parasitoids, from the parasitoid community on shoot gallers, all of which are in the genus Euura.
• 3 All tachinid larval parasitoids were also eliminated by the galling habit.
• 4 The cumulative effects of these exclusions resulted in a decline in mean number of parasitoid species per host species from almost sixteen species on external colonial feeders to 4.0 species on shoot gallers.
• 5 General patterns in per cent parasitism by non-tachinid and tachinid larval parasitoids, eonymphal and cocoon parasitoids, on exposed feeders to shoot gallers, showed declines in non-tachinid attack and elimination of tachinid, eonymphal and cocoon parasitoids. But leaf gallers tended to be attacked more than exposed feeders by non-tachinid larval parasitoids.
• 6 The galling habit had a long-term impact by reducing the number of parasitoid species attacking nematine sawfly gallers and per cent mortality inflicted, so that natural enemies may have been important as a selective factor in the evolution of galling nematine sawflies.

     

Intermediary metabolism and shell growth in the brachiopod Terebratalia transversa

Juvenile Terebratalia transversa (Brachiopoda) metabolize carbohydrates in the anterior-most marginal mantle at a rate of 0.46 μM glucose/g/hr (in vitro incubation of mantle in C¹⁴-glucose in a carrying medium of 10^-3 M non-radioactive glucose). The rate declines to 0.18μM glucose/g/hr in full-grown specimens. Carbohydrate metabolism in the marginal (anterior-most) mantle averages approximately 3.7 times greater than metabolism in (a portion of the ‘posterior’) mantle situated between the coelomic canals and the marginal mantle. This ratio remains constant in specimens of all sizes (i.e. an ontogenetic trend in the ratio is absent at p≤ 0.05). Organic acids are not detectable within the mantle (HPLC techniques) even after simulated anoxia (N₂ bubbling during mantle incubation). Glucose metabolism in vitro declines in both the marginal and ‘posterior’ mantles during anoxia and the metabolic ratio between marginal/‘posterior’ mantles becomes 1/1. We found no difference (at p≤ 0.05) in mean metabolic activity or in sue-related metabolic trends among populations from depths ranging between mean sea level and 70 m. However, the activity within the ‘posterior’ mantle was more variable in specimens from 70 m than in those from shallower habitats (10 m - mean sea level). The size of the specimens analyzed was most variable in the groups obtained from the shallowest habitats and least variable at 70 m depth. Our results may help define the energetics of fossil as well as living brachiopod shell growth. Brachiopod shell growth is known to be very slow relative to that of bivalves and our results indicate that this is a result of the animals' slow metabolism. The inflation of the valves in T. transversa is, in part, a function of the high ratio of intermediary metabolism in the marginal vs‘posterior’ mantle (i.e. parallels the relative growth rates at the shell margin vs‘posterior’ areas). We found that the bivalve, Chlamys hastata, which is commonly associated with T. transversa, has a lower ratio of metabolic activities in the ventral/dorsal mantle areas than the brachiopod has in the anterior/posterior. The difference produces a flatter shell in the bivalve in accord with allometric principles. The higher metabolic rate in the marginal vs‘posterior’ brachiopod mantle and its more pronounced decline with anaerobiosis is reflected in the greater definition of growth increments in the outer shell layer. Our results do not support recent generalizations that correlate shell thickness of a wide variety of invertebrates inversely with metabolic rate. Growth rate as determined from width of shell growth increments is a better index of metabolic rate. Although the genetic basis of glucose metabolism is unknown, the observed metabolic variability is consistent with suggestions that populations of marine organisms living in stable offshore environments are genetically more variable but morphologically more uniform than populations from shallow water. Furthermore, our results support suggestions that bivalved molluscs and brachiopods are very different metabolically, but the data are neutral with respect to theories of competitive exclusion of the two taxa throughout geologic history.     

Uptake and metabolism of benzyladenine in the early stage of flower bud development in vitro in tobacco

Benzyladenine (BA) was found to regulate the number of flower buds regenerated in vitro from pedicel tissue of tobacco. Flower bud induction was particularly sensitive to BA levels in the range of 0.45 to 1.0 μ M , where a two-fold increase in concentration caused a threefold rise in the number of buds. When tissues were fed radioactive BA for 24h, only 9–12% of the counts were recovered in the original compound. The rest was present in metabolites, tentatively identified as the mono-, di- and triribotides, 7- and 9-glucosides and 9-riboside of BA. The amount of growth regulator taken up and the quantities of BA and its metabolites in the explants were all linearly related to the concentration of the medium. The internal BA concentration was ca 60% of the level in the medium after 24 h. When the concentration in the medium was raised, relatively more BA remained in the non-conjugated form. However, this change in the equilibrium between BA and the conjugates is too small to account for the steep rise in the curve representing concentration vs effect between 0.45 and 1.0 μ M .     

Heterotrophic metabolism and diazotrophic growth ofNostoc sp. fromCycas circinalis

The cyanobiont ofCycas circinalis (identified asNostoc sp.) was isolated and its heterotrophic metabolism was studied in free culture under nitrogen-fixing conditions. Morphology, growth rate, nitrogenase activity, biochemical composition, efficiency of assimilation of organic carbon and molecular nitrogen were determined under different conditions of energy and carbon supply. The study has revealed the high potential of the heterotrophic metabolism in this symbiotic cyanobacterium. Although low rates of metabolic activities were attained under heterotrophic conditions, the efficiencies of organic carbon utilization (0.48 g cell-carbon per g glucose-carbon in chemoheterotrophy, from 0.65 to 0.74 under photoheterotrophy) and of N₂ assimilation (35.0 mg N₂ fixed per g glucose used in chemoheterotrophy, from 58.3 to 61.9 under photoheterotrophy) displayed by this organism were among the highest ever found in diazotrophically grown microorganisms. The isolate fromC. circinalis was able to grow indefinitely in the dark under nitrogen-fixing conditions, maintaining a well balanced biosynthetic activity and the capacity to resume photosynthetic metabolism quickly. The significance of the heterotrophic potential of this symbioticNostoc is discussed.     

The effect of auxin concentration on cytokinin stability and metabolism

The stability of [³H]zeatin riboside supplied to freshly excised tobacco pith explants was found to be inversely related to -naphthaleneacetic acid concentration in the incubation medium. At higher concentrations of -naphthaleneacetic acid greater breakdown of [³H]zeatin riboside was indicated by higher levels of degradative metabolites (adenine, adenosine and adenosine nucleotides) formed. This auxin effect on cytokinin metabolism appears to be mediated, at least in part, through cytokinin oxidase. The results of in-vitro assays carried out with partially purified enzyme from corn kernels substantiale this conclusion. These findings are discussed in relation to recent observations of auxin and cytokinin levels in crown-gall tumours with altered morphology.Abbreviations FPLC fast protein liquid chromatography - HPLC high-performance liquid chromatography - IP isopentenyladenine - NAA naphthaleneacetic acid - ZR zeatin riboside