Carbohydrates,lipids and lipoproteins and islet changes in diabetes with superimposed myocardial infarction

Short-term metabolic and concomitant morphologic effects of streptozotocin diabetes on isoproterenol-induced myocardial infarction was studied in Wistar rats, Of particular significance was the observation that myocardial infarction in concert with diabetes brought about a distinctive exacerbation of the severity and complexity of the histopathological lesions. Of all the biochemical parameters, serum glucose and free fatty acids registered maximum elevation and serum lactate and cardiac glycogen levels a maximum reduction. Among the lipoproteins, an inverse relationship was found between high density lipoproteins and low density and very low density lipoproteins; while high density lipoproteins, ratio of high density lipoprotein to low density lipoprotein and the percentage of high density lipoprotein were decreased, there was a significant increase in low density lipoprotein concentration and percentage values of low density and very low density lipoproteins. In diabetes, the B cell of the endocrine pancreas depicted selective necrosis. Loss of insulin granules and wide-spread necrobiosis of cellular elements of the pancreatic islets were observed, respectively, in myocardial infarction and in diabetes plus myocardial infarction combinations. Pathological evidence of chemical-induced mild toxicity was present in the exocrine parenchyma. Mitotic features and the presence of centroacinar cells in the damaged Langerhans’ islets supposedly formed the basis of regeneration of the tissue in diabetes, with or without vascular complications     

A sodium ion gradient as energy source for Peptostreptococcus asaccharolyticus

The determination of enzymatic activities in cell-free extracts of Acidaminococcus fermentans and Peptostreptococcus asaccharolyticus led to a refined scheme for the pathway of glutamate fermentation via (R)-2-hydroxyglutarate to acetate and butyrate. From the ratio of these products the amount of ATP generated by substrate level phosphorylation was calculated. Growth experiments with the organisms including Clostridium symbiosum and Clostridium tetanomorphum indicated that a sodium gradient contributed additional energy for growth. The high growth yields found in organisms containing the biotin dependent sodium pump glutaconyl-CoA decarboxylase could be reduced by the sodium ionophor monensin. In P. asaccharolyticus energy equivalent up to 0.6 mol ATP per mol of glutaconyl-CoA decarboxylated was conserved via the Na⁺ gradient. The data may explain the growth promoting effects of monensin in cattle.     

Releaser and primer pheromones in Collembola

In Collembola, pheromones appear to be present in the faecal pellets. Pheromone release after cessation of faeces production points to the digestive tract as a possible site of biosynthesis.During the pre-moulting periods Collembola do not react to pheromones, possibly due to their low activity at that time, whereas the production of the pheromones continues.Starvation periods of up to 14 days diminish pheromone release but do not cause complete cessation. Production per animal seems to decrease at increasing densities.The effect of pheromones on the reproductive efficiency of Collembola is discussed in the context of their physiological and behavioural ecology.     

Regulation of carbonic-anhydrase activity,inorganic-carbon uptake and photosynthetic biomass yield inChlamydomonas reinhardtii

The regulation of carbonic anhydrase by environmental conditions was determined forChlamydomonas reinhardtii. The depression of carbonic anhydrase in air-grown cells was pH-dependent. Growth of cells on air at acid pH, corresponding to 10 m CO₂ in solution, resulted in complete repression of carbonic-anhydrase activity. At pH 6.9, increasing the CO₂ concentration to 0.15% (v/v) in the gas phase, corresponding to 11 M in solution, was sufficient to completely repress carbonic-anhydrase activity. Photosynthesis and intracellular inorganic carbon were measured in air-grown and high-CO₂-grown cells using a silicone-oil centrifugation technique. With carbonic anhydrase repressed cells limited inorganic-carbon accumulation resulted from non-specific binding of CO₂. With air-grown cells, inorganic-carbon uptake at acid pH, i.e. 5.5, was linear up to 0.5 mM external inorganic-carbon concentration whereas at alkaline pH, i.e. 7.5, the accumulation ratio decreased with increase in external inorganic-carbon concentration. It is suggested that in air-grown cells at acid pH, CO₂ is the inorganic carbon species that crosses the plasmalemma. The conversion of CO₂ to HCO ₃ ^- by carbonic anhydrase in the cytosol results in inorganic-carbon accumulation and maintains the diffusion gradient for carbon dioxide across the cell boundary. However, this mechanism will not account for energy-dependent accumulation of inorganic carbon when there is little difference in pH between the exterior and cytosol.     

Regulation by kinetin and abcisic acid of correlative senescence in relation to grain maturation,source-sink relationship and yield of rice (Oryza sativa L.)

When kinetin was applied to the source organ (flag leaf) of rice (Oryza sativa L. cv. Ratna), foliar senescence was delayed and grain yield per plant (as evidenced by grain weight, grain/straw weight ratio and 1,000 grain growth) was increased through the increase of sink activity (increase in dry weight of the grains/plant), duration of sink capacity as well as photosynthetic ability of the glumes (as determined by the chlorophyll content of the glumes of the developing grains). However, application of kinetin to the sink organs (fruits), promoted senescence of the source but increased the yield by increasing the sink capacity and 1,000 grain growth mostly at the earlier stage of reproductive development. Lower sterility percentage was associated with higher grain yield of the plant by kinetin treatments. ABA applied either to the source or the sink promoted leaf senescence and reduced the grain yield by reducing the sink activity, harvest index, sink capacity duration and increasing the sterility percentage. Thousand grain dry weight at harvest did not vary significantly amongst the treatments. It was concluded that nutrient drainage was associated with the correlative influence of fruit on the monocarpic senescence of rice plant and that a competetion for differential allocation of cytokinin and ABA in the source and sink organs initiates this senescence syndrome.     

Phenolic acid effects on peanut growth and oil production

Plants of peanut (Arachis hypogaea L. var. PG No. 1) were given two foliar sprays of phenolic compounds (H-acid, 1, 2, 4-acid, resorcinol and RD-Brown) at 100 and 200 ppm, 35 and 50 days after sowing. In treated plants, shelling %, yield (kg/ha), number of gynophores per plant and number of pods per plant were significantly greater than in the control. Oil content of kernels also showed a significant increase with all the phenolic compounds applied. These compounds increased the linoleic acid concentration so improving nutritional quality. The number of gynophores was significantly correlated with the number of pods per plant and yield per hectare. The effect of phenolic compounds on growth and development was independent of their structural configuration.     

Methanogenesis from methanol in Methanosarcina barkeri studied using membrane inlet mass spectrometry

Abstract A mass spectrometer with membrane inlet was used to study methanol metabolism by Methanosarcina barkeri strain MS. The addition of methanol to methanol grown culture samples in the mass spectrometer vessel stimulated methanogenesis and hydrogen production. The apparent K _s for methanol was determined as 0.5 mM and the V _max as 8.14 mmol g (dry weight) h⁻¹. The V _max for methane production was fairly constant during growth of the culture on methanol implying that growth is tightly coupled to methanogenesis. The addition of methanol to culture samples in the mass spectrometer vessel stimulated methanogenesis with no lag which indicated that methanogenesis can be uncoupled from growth. Exposure of the culture sample in the mass spectrometer vessel to an atmosphere of 2 kPa oxygen for 80 min resulted in a decrease in the rate of methanogenesis from methanol but on returning the atmosphere to nitrogen the addition of further methanol stimulated methanogenesis. The effect of other inhibitors of methanogenesis (2-bromoethane sulphonate and monensin); K _j values 21.5 μM and 0.3 mM, respectively) were also studied.     

On the O2 flash yields of two cyanophytes

We explored O₂ flash yield in two cyanophytes, Anacystis nidulans and Agmenellum quadruplicatum. On a rate-measuring electrode, a single flash gave a contour of O₂ evolution with a peak at about 10 ms which was maximum (100) for 680 nm background light. On 625 nm illumination the peak was smaller (62) but was followed by an increased tail of O₂ attributed to enhancement of the background. After a period of darkness, repetitive flashes (5 Hz) gave a highly damped initial oscillation in individual flash yields which finally reached steady state at 94% of the yield for 680 nm illumination. When O₂ of repetitive flashes was measured as an integrated flash yield the results was distinctive and similar to that for a continuous light 1 (680 nm). An apparent inhibition of respiration which persisted into the following dark period was taken as evidence for the Kok effect. With a concentration-measuring electrode, integrated flash yield vs. flash rate showed the same nonlinear behavior as O₂ rate vs. intensity of light 1. We draw three conclusions about the two cyanophytes. (a) The plastoquinone pool is substantially reduced in darkness. (b) Because of a high ratio of reaction centers, reaction center 1 / reaction center 2, for the two photoreactions, saturating flashes behave as light 1. (c) Because repetitive flashes are light 1, they also give a Kok effect which must be guarded against in measurements designed to count reaction centers.