Showing papers on "Energy source published in 1970"

A Comparative View of Sperm Ultrastructure

Abstract: A comparative study of mammalian sperm showed common structure but species differences in the thickness of the outer fibers length of the midpiece and overall diameter of the tail. Both external retarding forces and internal resistance to bending may be overcome by the increased diameter of the outer fibers moving them farther from the axis of bending to increase their mechanical advantage and by addition of a third order of motor elements the satellite fibers. Cinematographic analysis of unusual patterns of locomotion that may be correlated with exceptional development of particular structural components may shed some light on the functional significance of these differences. The fine structure of urodele spermatozoa suggested that its axial fiber is the homolog of one of the outer fibers of the mammalian sperm tail and that the marginal fiber is probably homologous with one of the longitudinal columns of the fibrous sheath. The close association of the mitochondria with the axial fiber in urodele sperm instead of with the axonemal complex is consistent with the interpretation that the axoneme is capable of functioning independently of a mitochondrial energy source but that the long middle piece of vertebrate sperm has evolved to meet the energy requirements of the accessory outer fibers.(Authors modified)

Molar growth yields and fermentation balances of Lactobacillus casei L3 in batch cultures and in continuous cultures.

Abstract: SUMMARY: Fermentation balances determined for different substrates in batch and continuous cultures of Lactobacillus casei revealed two pathways of pyruvate conversion by this organism, a reduction to lactate and the phosphoroclastic cleavage. Pyruvate formed anaerobically from mannitol and citrate was split by the phosphoroclastic enzyme. Lactate was the main fermentation product formed during aerobic growth on mannitol and anaerobic and aerobic growth on glucose. In glucose-limited continuous cultures pyruvate conversion was dependent on the dilution rate. At low dilution rates glucose was fermented exclusively to acetate, ethanol and formate. At high rates only small amounts of acetate, ethanol and formate were formed and lactate production was maximal. Lactate dehydrogenase of L. casei had an absolute requirement for fructose-1,6-diphosphate and manganous ions. The specific activity of lactate dehydrogenase did not differ significantly at different dilution rates. It was concluded that the intracellular level of fructose-1,6-diphosphate controlled the pathway of pyruvate conversion. In batch cultures Y ATP values were between 18.2 and 20.9. No evidence for oxidative phosphorylation was found. In continuous cultures YATP values varied from 18.7 at low dilution rates to 23.5 at high dilution rates. From the dependence of YATP on the dilution rate, a maintenance coefficient of 1.52 x 10-3 was calculated. The Y ATP value corrected for energy of maintenance was 24.3. The possibility that the molar growth yields were erroneously high because of assimilation of growth substrate into intracellular polysaccharides, or because of energy yield from components of the medium other than the added energy source, was excluded.

Shock Synthesis of Amino Acids in Simulated Primitive Environments

Abstract: Primitive earth prebiological organic synthesis via amino acids shock heating in atmosphere-simulating gas mixture, suggesting energy sources from atmospheric entry

Two modes of Na extrusion in cells from guinea pig kidney cortex slices.

Abstract: Cells from guinea pig kidney cortex slices, which have been loaded with Na and caused to lose K, by leaching at 0.6° C for 2.5 hours, extrude Na with Cl upon rewarming to 25° C in a medium without K. A subsequent rise in the K concentration in the bath at 25° C induces further net Na extrusion, 1 Na being extruded in exchange for 1 K that is taken up. When the leached tissue is rewarmed to 25°C in the presence of K in the bathing fluid (2 or 16 mM), some Na is extruded accompanied with Cl (by a mechanism that is inhibited by ethacrynic acid) and some Na is extruded maintanining a 1:1 ratio with the K that is taken up, (this system being inhibited by ouabain). Thus two modes of Na extrusion are observed, mode A that is accompanied by net Cl efflux, and that is inhibited by 2 mM ethacrynic acid, but not by 1 or 10 mM ouabain and mode B in which one K is taken up for each Na extruded. Mode B is inhibited by 1 mM ouabain and not by ethacrynic acid. DNP and anoxia inhibit both modes A and B. Insufficient doses of ouabain do not explain the refractoriness of mode A to ouabain. Ouabain and ethacrynic acid are known inhibitors of the Na−K-ATPase at much lower doses. It is concluded that both modes may originate in different Na pumps which may have different energy sources. Pump A should be efficient in the volume regulation of the cell. According to experimental procedure, both modes of Na extrusion appear of comparable magnitude. In the steady-state their relative role may be different.

Heating of the solar wind.

Abstract: Solar wind heating, determining roles of various energy sources from Explorer 34 observations

The critical electric potential difference for photophosphorylation. Its relation to the chemiosmotic hypothesis and to the triggering requirements of the ATPase system.

Abstract: The physical meaning of the observed critical electric potential difference necessary for photophosphorylation is discussed. An interpretation of this phenomenon on the basis of the equilibrium thermodynamic formulation of the chemiosmotic hypothesis requires a reversible ATPase system. Contrary to this, ATP hydrolysis experiments seem to confirm that the Mg++dependent ATPase system of class 11-chloroplasts is irreversible in the absence of SH-compounds. This sheds doubt on the equilibrium thermodynamic interpretation of the critical electric potential difference for phosphorylation. However it can be shown, that the seeming irreversibility may be due to some trigger requirements of an intrinsically reversible ATPase system. This leads to an identification of the critical electric potential difference with the triggering level of the enzyme system. Two operational models for an ATPase system, whose activity is modulated by the electric potential difference, are derived. These account quantitatively for a set of experiments on the critical electric potential difference. In the preceding paper it has been shown that a certain electric potential difference across the thylakoid membrane is a necessary condition for photophosphorylation in short flash groups. Moreover it has been demonstrated that three protons have to be translocated across their electrochemical potential difference for any molecule of ATP which is synthesized [I]. Both results favour strongly the chemiosmotic hypothesis of Mitchell [2], who has postulated that an electric potential difference provides part of the free energy for the formation of ADP N P bonds. However, the mechanism which gives rise to a critical level of the electric potential difference has still to be interpreted. An attempt has been made to see whether this phenomenon can be understood from the same role of the electric potential difference, as an energy source for phosphorylation. It will be demonstrated that, at first sight, the critical electric potential difference can be interpreted from the equilibrium thermodynamic formulation of the chemiosmotic hypothesis. However, an inspection of the basic assumption for this interpretation, the reversibility of the ATPase system, reveals inconsistency with the apparent irreversibbility of the enzyme system. The latter has been concluded from hydrolysis experiments on class 11chloroplasts. This apparent irreversibility deserves a

Principal phase of oil formation

Abstract: This paper reviews different theories on the origin and transmission of hydrocarbons in sedimentary rocks. It reviews the diagenetic and catagenetic effects on sediments to mobilize dispersed hydrocarbons into concentrated oil pools. Geochemical information on the hydrocarbons is given along with bituminoid content of sedimentary rocks and recent ocean sediments. Effects of temperature and pressure on the source rocks is provided in graphical form. Attempts are now being made in the USSR to define much more accurately the conditions of the principal phase of oil formation, and its scale and length for different sediments in different oil and gas basins. Attempts are also being made to determine the balance of diagenesis and catagenesis of both organic matter as a whole and bituminoids, including solid, liquid, and gaseous hydrocarbons.

Correlation between ion fluxes and ion-stimulated adenosine triphosphatase activity of plant roots.

Abstract: The energy-dependent influx of Rb+ into excised roots of corn, wheat, and barley has been determined and compared to the Rb+-stimulated ATPase activity of membrane fractions obtained from root homogenates of these species. The external Rb+ concentrations studied were in the range of 1 to 50 mm. The ratio of Rb+ influx/Rb+-stimulated ATPase was approximately 0.85 and was nearly constant for all the species and Rb+ concentrations studied. The correlation coefficient for Rb+ influx versus Rb+-activated ATPase was 0.94. The results support the concept that ATP is the energy source for ion transport in roots and that an ATPase participates in the energy transduction process involved in energy-dependent ion transport.

The Mechanism of Hydrogen Evolution by Chlamydomonas moewusii.

Abstract: Using manometric techniques, H(2) evolution in both darkness and light has been studied in the green alga, Chlamydomonas moewusii.Hydrogen evolution in the dark is accompanied by the release of only CO(2) in manometrically detectable amounts. It is depressed by dark starvation and inhibited both by monofluoroacetic acid and by uncouplers of phosphorylation. This evidence suggests that the reaction is dependent on oxidative carbon metabolism for reductant and phosphorylation for energy to raise the reductant to a redox potential capable of reducing H(+).Photoevolution of H(2) is also accompanied by the release of only CO(2). It is depressed by dark starvation and stimulated by acetate or a period of photosynthesis. Monofluoroacetic acid causes complete inhibition, while 3-(3,4-dichlorophenyl)-1,1-dimethylurea causes no or only slight inhibition. These results indicate that oxidative carbon metabolism is the source of reductant for the reaction. Photoevolution of H(2) does not show Emerson enhancement, and it has an action spectrum peaking at a longer wave length than that of photosynthesis. These characteristics, together with the slight effect of 3-(3,4-dichlorophenyl)-1,1-dimethylurea on the reaction, show that only system I of photosynthetic electron transport is involved in the reaction. Photoevolution of H(2) is stimulated by uncouplers; this indicates that the role of light is not to provide energy by phosphorylation. Rather, the results support an electron flow driven directly by light through system I from reductant produced in oxidative carbon metabolism to a redox potential capable of reducing H(+).

Chapter III Design and Formulation of Microbial Culture Media

Abstract: Publisher Summary This chapter discusses the design and formulation of microbial culture media. Culture media have been described for the successful cultivation of plant and mammalian cells, protozoa, fungi, and bacteria. A non-cellular culture medium for viruses has not yet been formulated. At first sight the various micro-organisms have little in common with each other and this impression is reinforced by the many thousands of diverse culture media described for their cultivation. The structural polysaccharide components of the cell walls make up a larger proportion of the dry weight. The nutrient environment may be divided into: (i) the physical environment-temperature, humidity, and atmosphere. (ii) The chemical environment-those chemical compounds supplied in culture medium to permit growth of micro-organisms. The energy source required by cells varies widely and the cells may be classified as: (i) Photosynthetic-demanding only light as an energy source. (ii) Chemo-lithotropic-deriving energy from oxidation of inorganic molecules. (iii) Chemo-organotrophic-requiring organic carbon compounds as energy sources, which often act as a carbon source as well.

Changes in Constituents and Ultrastructure of Hyphal Compartments during Autolysis of Glucose-starved Penicillium chrysogenum

Abstract: SUMMARY: The dry weight of Penicillium chrysogenum starved of an energy source decreased exponentially. The protein, RNA, DNA and endogenous respiration decreased rapidly during the first few hours of starvation and reached about 25% of their original values after 5 days starvation. The carbohydrate content of the mould only decreased after the first 2 days of starvation. About 60% of the carbon lost during autolysis was oxidized to carbon dioxide. Lysis of organelles in individual hyphal compartments occurred synchronously and did not seem to involve autophagy. Autolysis of separate compartments in the same hyphae was not synchronized. Ribosomes were rapidly degraded but membranes were particularly resistant to breakdown. Intra-hyphal hyphae were observed. In the final stages of autolysis the culture consisted largely of empty hyphal walls. A proportion of cytologically normal hyphal compartments were present at all stages, suggesting that maintenance and/or cryptic growth of some hyphae (or compartments) occurred at the expense of others.

Degradation and utilization of hemicellulose from intact forages by pure cultures of rumen bacteria.

Abstract: Several pure strains of rumen bacteria have previously been shown to degrade isolated hemicelluloses from a form insoluble in 80% acidified ethanol to a soluble form, regardless of the eventual ability of the organism to utilize the end products as energy sources. This study was undertaken to determine whether similar hemicellulose degradation or utilization, or both, occurs from intact forages. Fermentations by pure cultures were run to completion by using three maturity stages of alfalfa and two maturity stages of bromegrass as individual substrates. Organisms capable of utilizing xylan or isolated hemicelluloses could degrade and utilize intact forage hemicellulose, with the exception of two strains of Bacteroides ruminicola which were unable to degrade or utilize hemicellulose from grass hays. Intact forage hemicelluloses were extensively degraded by three cellulolytic strains that were unable to use the end products; in general, these strains degraded a considerably greater amount of hemicelluloses than the hemicellulolytic organisms. Hemicellulose degradation or utilization, or both, varied markedly with the different species and strains of bacteria, as well as with the type and maturity stage of the forage. Definite synergism was observed when a degrading nonutilizer was combined with either one of two hemicellulolytic strains on the bromegrass substrates. One hemicellulolytic strain, which could not degrade or utilize any of the intact bromegrass hemicellulose alone, almost completely utilized the end products solubilized by the nonutilizer. Similar synergism, although of lesser magnitude, was observed when alfalfa was used as a substrate.

Factors governing the kinetics and steady state of the mitochondrial nicotinamide nucleotide transhydrogenase system.

Abstract: The mitochondrial nicotinamide nucleotide transhydrogenase catalyzes a rapid reduction of NAD+ by NADPH as compared to the reduction of NADP+ by NADH. By assuming pseudo first-order kinetics it is shown that the rate constant of the reaction is strongly dependent on the actual [NAD+] [NADPH] / [NADP+] [NADH] ratio, giving a half-maximal rate constant at [NAD+] [NADPH]/[NADH] [NADP+] of approx. 0.003. The altered rate constant can possibly be explained on the basis of a reversible conformational change of the enzyme between an active and an inactive state, controlled by the prevailing concentrations of oxidized and reduced nicotinamide nucleotides. Possible similarities with bacterial transhydrogenases are considered. In the presence of an energy source the overall transhydrogenase reaction involves a strong shift of the equilibrium towards the conversion of NADH and NADP+ into NAD+ and NADPH. Evidence is presented that the final extent of the overall energy-linked transhydrogenase reaction is strikingly dependent on the ratio of the initial rates of the energy-linked reduction of NADP+ by NADH and the nonenergy-linked reduction of NAD+ by NADPH. Thus, the final extent of the transhydrogenase reaction in the presence of an energy source can by explained in terms of a steady state rather than an equilibrium. The possibility of an energy-linked conformational change of transhydrogenase, involving a conversion of the enzyme from an inactive to an active state, is considered.

Green River Oil Shale—Concept of Origin Extended: An Interdisciplinary Problem Being Attacked from Both Ends

Abstract: A much fuller understanding of the Green River oil shale and its organic chemistry will emerge when the geologists, paleontologists, organic chemists, biologists, paleolimnologists, and biogeochemists, who are now working on it, integrate their findings with those of the others. We know from the geology, paleontology, and paleolimnology that the biologic progenitors of the organic substance in the Green River oil shale could only have been microscopic algae, and other micro-organisms, that grew and accumulated in the central parts of large, shallow lakes that existed under a subtropical climate. The only nonlacustrine organic components were wind-blown, or water borne, pollens and waxy spores. These, however, made up a large and important part of the organic-rich sediment. The geology of the Green River Formation shows that as the algal and pollen-rich sediment was buried deeper and deeper, progressively more of its pore water and dissolved constituents were expressed. Static pressures may have reached as much as 210 kg cm−2, and the ambient temperature rose, with depth, to somewhere within the range between 90° and 125° C. Beneath the ancient lakes a tectonically quiescent environment persisted for tens of millions of years after their organic sediments had been deeply buried. The organic material of the Green River oil shale can be divided into three fractions—a small bitumen fraction that is extractable with common organic solvents, a major fraction called koerogen that consists of insoluble pyrobitumens, and a somewhat smaller inert fraction that is neither soluble nor does it yield oil on pyrolysis. As all three fractions originated in the same algal, pollen-rich sediment, an explanation for their marked differences must be sought in their geochemical history or from a study of the modern analogues of their progenitors. The components of the bitumen fraction consisted of “biological markers” that were inherited from the Eocene plants and animals in which they originally formed. Diagenesis has changed these hydrogen-rich compounds, but not enough to obscure their provenance. Kerogen presumably became insoluble because its hydrogen-rich components polymerized. My speculation is that the inert fraction was derived from a polyphenolic substance produced in the original algal ooze by “non-enzymatic browning.” Only three Classes of non-marine algae need be considered as progenitors of the Green River oil shale; the Xanthophyceae, the Chlorophyceae, and the Cyanophyceae. Only the Cyanophyceae (the blue-green algae) meet the biologic and paleontologic requirements to have served as the dominant precursors of the Green River oil shale. Several other oil shales clearly were derived from the Xanthophyceae, specifically Botryococcus. The blue-green algal ooze now forming, and accumulating, in Mud Lake, Florida, has been studied biologically and chemically as a possible present-day analogue of the Green River oil shale precursor. In this small lake we have established the fact that a bacterial inhibitor is produced, which inhibits decay of the algae and thereby permits the accumulation of energy-rich organic compounds. We infer that a similar indigenous inhibitor must have acted in the Eocene lakes to permit them to become the huge energy sinks they were. Studies of the organic chemistry of living blue-green algae show that they contain appreciable percentages of fatty acids, hydrocarbons, and very large percentages of proteins. These promising, energy-rich compounds could serve as source materials for potential conversion into oil shale in the geologic future. Certain marine anaerobic bacteria convert fatty acids into aliphatic hydrocarbons. Fresh-water obligate anaerobes should be investigated to see if they also convert fatty acids into hydrocarbons. The part played by aquatic animals that live in, or on, freshwater algal ooze in synthesizing hydrocarbons has not been investigated, but deserves attention. Pollen grains, of course, must be considered an important precursor of hydrocarbons produced on pyrolysis. They contain far higher percentages of long chain hydrocarbons and alcohols than most plant materials. The major problem ahead is to account for the progressive hydrogenation and subsequent polymerization of the relatively oxygen-rich constituents of algae such as the polysaccharides, amino acids, ammo sugars, and fatty acids into the insoluble pyrobitumens that constitute, particularly, the kerogen fraction of the Green River oil shale.

Venus's General Circulation is a Merry-Go-Round.

Abstract: It is suggested that the atmosphere of Venus might rotate even if the planet did not, due to an apparently new nonlinear instability. One expects convention due to solar heating; if somehow a vertical shear of the horizontal wind arises, its advection will tilt the cells. The tilt of the cells will cause a correlation between the vertical and horizontal velocities, i.e., a Reynolds stress, of the correct sign to reinforce the original shear. Since the time derivative of the mean shear is proportional to the tilt, and the tilt is proportional to the shear for small shear, the mean shear will grow exponentially if the damping is not too heavy. The important requirement is that the cells to be tilted have their own energy source. The range of parameters for which this mechanism is found to work numerically includes those estimated for the atmosphere of Venus.

Laser beam device and method for subterranean recovery of fluids

Abstract: Monochromatically identical beams emitted from a plurality of laser devices positioned in radial relation to a common optical axis along which a composite beam of concentrated energy is projected A rotatable reflective lens device located a remote distance from the source of the composite beam directs the composite beam transverse to the common optical axis The direction of the common optical axis and the concentration of the laser beams are adjustable

Nitrogen fixation by blue-green algae in Yellowstone thermal areas*

Abstract: Potential nitrogen-fixing blue-green algae were common in three hot spring streams studied in Yellowstone National Park. In two streams, where the dominant nitrogen-fixing algae were species of Calothrix, nitrogen fixation, as measured by uptake of 15N2, was detected in situ in the temperature range 28–46 C. At higher temperatures nitrogen fixation was not detected, although the algae may have received fixed nitrogen from a growth of Calothrix, Nostoc, and unicellular algae which occurred at lower temperatures on the sides of the streams. In the third stream, where Mastigocladus was abundant, nitrogen fixation was detected at temperatures up to 54 C, although the optimum for fixation was near 42.5 C. The overall data imply that in situ nitrogen fixation contributes to the productivity of Yellowstone hot spring regions and that Mastigocladus and Calothrix are the most important nitrogen-fixing blue-green algae.

Spectrophotometric studies of acyl-coenzyme A synthetases of rat liver mitochondria

Abstract: 1. Deca-2,4,6,8-tetraenoic acid is a substrate for both ATP-specific (EC 6.2.1.2 or 3) and GTP-specific (EC 6.2.1.–) acyl-CoA synthetases of rat liver mitochondria. The enzymic synthesis of decatetraenoyl-CoA results in new spectral characteristics. The difference spectrum for the acyl-CoA minus free acid has a maximum at 376nm with emM 34. Isosbestic points are at 345nm and 440nm. 2. The acylation of CoA by decatetraenoate in mitochondrial suspensions can be continuously measured with a dual-wavelength spectrophotometer. 3. By using this technique, three distinct types of acyl-CoA synthetase activity were demonstrated in rat liver mitochondria. One of these utilized added CoA and ATP, required added Mg2+ and corresponded to a previously described `external' acyl-CoA synthetase. The other two acyl-CoA synthetase activities utilized intramitochondrial CoA and did not require added Mg2+. Of these two `internal' acyl-CoA synthetases, one was insensitive to uncoupling agents, was inhibited by phosphate or arsenate, and corresponded to the GTP-specific enzyme. The other corresponded to the ATP-specific enzyme. 4. Atractylate inhibited the activity of the two internal acyl-CoA synthetases only when the energy source was added ATP. 5. The amount of intramitochondrial CoA acylated by decatetraenoate was independent of whether the internal ATP-specific or GTP-specific acyl-CoA synthetase was active. It is concluded that these two internal acyl-CoA synthetases have access to the same intramitochondrial pool of CoA. 6. The amount of intramitochondrial CoA that could be acylated with decatetraenoate was decreased by the addition of palmitoyl-dl-carnitine, 2-oxoglutarate, or pyruvate. These observations indicated that pyruvate dehydrogenase (EC 1.2.4.1), oxoglutarate dehydrogenase (EC 1.2.4.2), carnitine palmitoyltransferase (EC 2.3.1.–), citrate synthase (EC 4.1.3.7), and succinyl-CoA synthetase (EC 6.2.1.4) all have access to the same intramitochondrial pool of CoA as do the two internal acyl-CoA synthetases.

Seasonal biochemical composition and energy sources of Sagitta hispida

Abstract: There are few available data on the biochemical composition of warm-water zooplankton in general, and chaetognaths in particular. Unlike populations from higher latitudes, many species probably breed to some extent throughout the year, with life cycles measured in weeks rather than months or years. Analysis of protein, fat, carbohydrate and ash in the chaetognath Sagitta hispidaConant over 1 year showed that, although protein is always the largest component, averaging 53% of the dry weight, it fluctuates widely. The non-protein fraction of the total nitrogen also fluctuates and averages over a third of the total. Experimentally fed and starved animals showed no such protein variability, which was ascribed, there-fore, to changes in environmental parameters other than food availability (e.g. salinity). Starved animals used up body protein, and the O:N ratio in freshly-caught animals also indicated a protein-based metabolism. Periods of starvation of at least 1/4 the length of its life cycle could be tolerated. S. hispida may be added to the list of a variety of planktonic groups over a range of latitudes and feeding habits, which appear to utilize protein as a normal energy source and reserve material.

The extraction, characterization, and significance of soil polysaccharides.

Abstract: Publisher Summary Although much is known about the nature and function of many polysaccharides synthesized by individual organisms, there is little information relating to the polysaccharides produced in an environment such as the soil, which in a unique way to bring together a great variety of biological forms. Polysaccharides have been extracted from soils by many different chemical reagents, and recently methods have been devised that enable most of the carbohydrates to be isolated from other soil materials. The extracted polysaccharides show a continuum of molecular sizes and contain a wide range of neutral and charged monosaccharides, amino acids, and other unidentified nitrogenous and acid components. Carbohydrates from different soils are similar in chemical composition suggesting that the microbial population of different soils is qualitatively similar. This chapter describes the mechanisms related to the extraction, characterization, and significance of soil polysaccharides. Many methods have been used to fractionate extracted soil polysaccharides, the most successful of which are based on gel filtration and chromatography on charged supports such as cellulose. The composition of soil polysaccharides suggests that in soils they may carry charged sites and take part in exchange reactions and act as energy sources for heterotrophic organisms. However, the main stimulus for the study of soil polysaccharides has arisen from repeated indications of their favorable influence on soil physical conditions. Much work has been directed toward this aspect, and it has been shown that microbially produced soil polysaccharides are capable of stabilizing soil aggregates against dispersion in water. Methods for the isolation of polysaccharides from other soil materials in good yield are now available and carbohydrate chemists have developed methods for the analysis of extracted polysaccharides.

Conditions for activity of glutaminase in kidney mitochondria

Abstract: 1. Rat kidney mitochondria oxidize glutamate very slowly. Addition of glutamine stimulates this respiration two- to three-fold. Addition of glutamate also stimulates respiration in the presence of glutamine. 2. By measuring mitochondrial swelling in iso-osmotic solutions of glutamine or of ammonium glutamate it was shown that glutamine penetrates the mitochondrial membrane rapidly whereas ammonium glutamate penetrates very slowly. 3. Experiments in which reduction of NAD(P)(+) was measured in preparations of intact and broken mitochondria indicated that glutamate dehydrogenase shows the phenomenon of ;latency'. On the addition of glutamine rapid reduction of nicotinamide nucleotides in intact mitochondria was obtained. 4. During the action of glutaminase there is an accumulation of glutamate inside the mitochondria. 5. When the mitochondria were suspended in a medium containing glutamine, P(i) and rotenone the rate of production of ammonia was stimulated by the addition of a substrate, e.g. succinate. Addition of an uncoupler or antimycin A abolished this stimulation. 6. The effects of succinate and uncoupler were especially pronounced in the presence of glutamate, which is an inhibitor of glutaminase activity by competition with P(i). 7. Determination of the enzyme activity in media at different pH values showed that the optimum pH for glutaminase activity in the preparation of broken mitochondria was 8, whereas for intact mitochondria it was dependent on the energy state. In the presence of succinate as an energy source it was pH 8.5, but in the presence of uncoupler or antimycin A it was 9. This displacement of the pH optimum to a higher value was especially pronounced in the presence of both glutamate and uncoupler. 8. If nigericin was present in potassium chloride medium the pH optimum for enzyme activity in intact non-respiring mitochondria was nearly the same as in the preparation of broken mitochondria; however, its presence in K(+)-free medium displaced the pH optimum for glutaminase activity to a very high value. 9. It is postulated that because of low permeability of the kidney mitochondrial membrane to glutamate the latter accumulates inside the mitochondria, and that this leads to the inhibition of the enzyme by competition with P(i) and also by lowering the pH of the intramitochondrial space. With succinate as substrate for respiration there is an outward translocation of H(+) ions, which together with accumulation of P(i) increases glutaminase activity. Translocation of K(+) ions inward increases the enzyme activity, perhaps by increasing the pH of the internal spaces and causing an accumulation of P(i). 10. The importance of the location of the enzyme in the mitochondria in relation to its biological function and conditions for activity is discussed.

Effect of Insulin on the Synthesis in Vitro of Hexokinase in Rat Epididymal Adipose Tissue

Abstract: The ability of insulin to increase the hexokinase content of epididymal adipose tissue was studied in vitro, using glucose, pyruvate, or alanine as energy source. Glucose alone caused an increase in hexokinase content which was maximal at 1–10 mm glucose when compared to controls incubated with no energy source. Insulin by itself was ineffective but, in the presence of 10 HIM glucose, caused a significant stimulation at 5×1O-4 U/ml. The effect of insulin with glucose present was significant when expressed per mg extract protein, per g tissue, or per fat pad. Pyruvate alone caused a significant increase in hexokinase activity /mg protein. Insulin led to a significant further increase. Insulin is thus, itself, a stimulator of hexokinase content when a suitable energy source is available. The presence of glucose, the substrate for the enzyme, is not necessary. The stimulation of hexokinase activity by insulin with glucose or pyruvate as energy source was blocked by the addition of actinomycin D to the incuba...

Diffuse Cosmic X- and Gamma Radiation: The Isotropic Component

Abstract: The ability of the various theories to explain the three main spectral features at 1/4 keV, 60 keV and 1 MeV is summarized in Tables II and III. Clearly, confirmation of the reality of these features, especially the soft X-ray and γ-ray excesses, is one of the key elements in enabling us to decide between the competing theoretical interpretations. None of the proposed interpretations are easily explained in terms of the available energy in cosmic rays (except perhaps the Seyfert galaxy proposal, and this runs into difficulties). It seems that one either has to regard normal galaxies at the present epoch as prolific sources of cosmic rays (∼ 1060 erg/galaxy in protons), as is required by the Brecher-Morrison model, or to argue that at early stages in their evolution far more energy is available than at present. One ends up with much the same energy requirement in this approach. One could conceivably identify such an early phase with the radio galaxy or QSO phenomena: in any event, cosmological evolution plays a major role. Cosmology does ease the energy requirements, but only for the inefficient mechanisms, such as nonthermal bremsstrahlung or π° -production. It seems that one still needs the metagalactic cosmic ray flux to be ∼ 10-2 of the galactic flux in the diffuse inverse Compton models, and 10-2–10-4 in the nonthermal bremsstrahlung models. Faced with problems of energetics, one is tempted to turn to the most energetic objects in the Universe, namely Seyfert nuclei and QSO's, to provide the basic energy source, whether directly or indirectly, for the diffuse X-ray background. A direct connection could be more readily investigated when X-ray observations are available of more extra-galactic sources. Another approach, complementary to that of looking for remote discrete sources, is to seek angular fluctuations, or limits on such fluctuations in the diffuse X-ray background. The best results presently available are those from the X-ray experiment on board OSO 3. Schwartz (1970) reports a limit of δI/I∼four percent on small-scale (∼10°) fluctuations over 10–100 keV over about one-quarter of the sky. If one assumes a astrophysics, namely the origin of cosmic rays, is intimately linked to the origin of the X-ray background. It may well be that no single mechanism suffices to account for the entire spectrum of isotropic X- and γ-radiation. Nature is sufficiently perverse for there to be a reasonable probability that several different processes are contributing, and considerable ingenuity will be required to ascertain which mechanism, if any, is assigned the dominant role in a given spectral region.