Chromosomal analyses in vinyl chloride-exposed workers

Chromosomal morphology from cultured peripheral lymphocytes was studied in 81 men; 57 of the men were employed on plants manufacturing vinyl chloride or polyvinylchloride, 19 were on-site controls and 5 were off-site controls. There was a significant increase in chromosomal abnormalities in the exposed workers when compared with the controls. The greatest statistically significant increase in total B and total C cells occurred in autoclave operators, with smaller increases in other job categories. The increase in chromosomal aberrations was correlated with the length of exposure and with a history during the year prior to sampling (1973–1974) of exposure to excursion levels of vinyl chloride. Information on smoking habits was obtained 18 months after blood sampling and a positive correlation between these and total C cell abnormalities was found. There was no positive correlation with various other parameters (bilirubin, platelets, γ-glutamyltranspeptidase, alkaline phosphatase, alanine transaminase and aspartate transaminase). It was not possible to estimate which of the three parameters (smoking history, length of employment or exposure to excursion levels) was the most important.     

Characteristics of microsomal reduction of benzo[a]pyrene 4,5-oxide

NADPH-reduction of benzo[a]pyrene 4,5-oxide (BP-4,5-oxide) to BP required four components from rat liver: cytochrome P-450, NADPH cytochrome P-450 reductase, phosphatidylcholine and a soluble, heat-sensitive factor which was present in 105 000 × g supernatant and was also released from microsomes by sonication. The requirement for this factor contrasts with recently reported results from Sugiura et al. (Cancer Res., 40 (1980) 2910). Oxide-reduction was 40 times faster under anaerobic conditions, but oxygen did not affect the stimulation factor. This stimulation was highest (× 15) at low concentrations of microsomal protein (<0.1 mg/ml) and was almost absent at high concentrations of microsomal protein (>1 mg/ml). Oxide-reduction activity was proportional to microsomal protein concentration in the presence of added 105 000 × g supernatant, but for microsomes alone (>0.1 mg/ml) exhibited a parallel plot with an intercept at 0.08 mg/ml microsomal protein. Stimulation was highest at high concentrations of BP-4,5-oxide and a linear plot of V⁻¹ vs. [BP-4,5-oxide]⁻¹ was only obtained in the presence of 105 000 × g supernatant (K_m = 3 μM, V_max = 3.3 nmol/mg/min). Microsomal hydration of BP-4,5-oxide (inhibited in reductase assays) was unaffected by 105 000 × g supernatant, suggesting that stimulation of oxide-reduction did not derive from solubilization of BP-4,5-oxide. Stimulation was observed in the initial rate of reaction and was independent of incubation time. Inhibition of lipid peroxidation, removal of peroxides and deoxygenation were all excluded as explanations of the stimulatory effect.     

Requirement for glucose during in vitro culture of sheep preimplantation embryos.

Glucose utilization by sheep embryos was examined in 8-cell (N = 36) and blastocyst (N = 36) stages, by measuring conversion of [5-3H]glucose to 3H2O. Fifty percent glucose utilization occurred at 0.79 +/- 0.69 mM for 8-cell embryos and -0.06 +/- 0.15 mM for blastocysts. Development of 1- and 2-cell sheep embryos (N = 264) was examined under different glucose concentrations (0, 1.5, 3, or 6 mM) and in the presence or absence of 0.33 mM pyruvate and 3.3 mM lactate (PL). Overall, the presence of glucose was detrimental (P less than 0.001) to embryonic development. By contrast, the presence of pyruvate and lactate was beneficial (P less than 0.001) to development. An interaction was observed between the concentration of glucose and presence or absence of PL (P less than 0.05). An optimum level of glucose occurs at 0-3 mM in the presence of PL (P less than 0.1). Development to the blastocyst stage was observed in medium when supplemented with amino acids and albumin alone. Thus, glucose metabolism is not critical for embryonic development, but beneficial at low concentrations. High concentrations can inhibit development, possibly by inhibiting the tricarboxylic acid (TCA) cycle. Sheep embryos may also be using amino acids as an energy source for development.     

On the origin of mitochondria: a reexamination of the molecular structure and kinetic properties of pyruvate dehydrogenase complex from brewer''s yeast

45Ca2+ incorporated in response to glucose was selectively mobilized from the beta-cell-rich pancreatic islets of ob/ob-mice after raising the intracellular Na+ by removal of K+ or addition of ouabain or veratridine. Also studies of insulin release indicated opposite effects of glucose and Na+ on the intracellular sequestration of calcium. The fact that glucose inhibits insulin release induced by raised intracellular Na+ indicates that this sugar can lower the cytoplasmic [Ca2+]. The concept of a dual action of glucose on the cytoplasmic [Ca2+]. The concept of a dual action of glucose on the cytoplasmic [Ca2+] might well explain previous observations of an inhibitory component in the glucose action on the 45Ca2+ efflux.     

Alternative Pathways of Glucose Utilization in Brain; Changes in the Pattern of Glucose Utilization in Brain Resulting from Treatment of Rats with 6-Aminonicotinamide

The effect of 6-aminonicotinamide (6AN) treatment on the activities of alternative pathways of glucose metabolism in 20-day-old rat brain was evaluated by measurements of yields of 14CO2 from glucose labeled with 14C on carbons 1, 2, 3 + 4, or 6 and uniformly labeled glucose, and from the incorporation of 14C from specifically labeled glucose into lipids by brain slices from cerebral hemispheres and cerebellum. At the highest dose of 6AN used (35 mg/kg body weight) there was a significant decrease in the 14CO2 yields via the pentose phosphate pathway, the glycolytic route, tricarboxylic acid (TCA) cycle, and via the glutamate-gamma-aminobutyric acid pathway. Giving a graded series of doses (20-35 mg 6AN/kg body weight) revealed a hierarchy of responses in which the pentose phosphate pathway, lactate, glyceride-glycerol, and fatty acid formation were most sensitive, followed, in sequence, by the pyruvate dehydrogenase reaction, the glutamate-gamma-aminobutyrate route and, finally, the TCA cycle. The nature of the blocks in the various pathways was examined by the use of metabolite profiles.     

Effect of Aging on the Metabolism of Pyruvate and 3-Hydroxybutyrate in Nonsynaptic and Synaptic Mitochondria from Rat Brain

Abstract: Age-dependent changes in the oxidative metabolism in nonsynaptic and synaptic mitochondria from brains of 3, 12, and 24-month-old rats were investigated. When pyruvate and malate were used in conjunction as substrates, a significant reduction in State 3 respiration was observed in both mitochondrial populations from 12-and 24-month-old rats compared with 3-month-old animals. A similar age-dependent reduction in the oxidation of [1-¹¹C]pyruvate was also observed in nonsynaptic and synaptic mitochondria from senescent rats. Pyruvate dehydrogenase complex activity (both active and total) was, however, not decreased in the two mitochondrial populations from brains of 3, 12, and 24-month-old rats. When DL-3-hydroxybutyrate plus malate were used as substrates, a decrease in State 3 respiration was observed only in synaptic mitochondria from 24-month-old rats compared with 3- month-old animals. Similarly, an age-dependent reduction in the oxidation of 3-hydroxy[3-¹¹C]butyrate was also observed only in synaptic mitochondria from 12-and 24-month-old rats. However, a significant reduction in the activities of ketone body-metabolizing enzymes, namely, 3-hydroxybutyrate dehydrogenase, 3-ketoacid CoA transferase, and acetoacetyl-CoA thiolase was observed in both mitochondrlal populations from 12- and 24-month-old rats compared with 3 month-old animals. These findings show that specific alterations in oxidative metabolism occur in nonsynaptic and synaptic mitochondria from aging rats. The data also suggest that in addition to alterations in enzyme activities, permeability of anions (e.g. pyruvate) across the inner mitochondrial membrane may be altered in nonsynaptic and synaptic mitochondria from senescent animals.     

Regulation of pyruvate kinase from Propionibacterium shermanii

Pyruvate kinase from Propionibacterium shermanii was shown to be activated by glucose-6-phosphate (G-6-P) at non-saturating phosphoenol pyruvate (PEP) concentrations but other glycolytic and hexose monophosphate pathway intermediates and AMP were without effect. Half-maximal activation was obtained at 1 mM G-6-P. The presence of G-6-P decreased both the PEP_0.5V and ADP_0.5V values and the slope of the Hill plots for both substrates. The enzyme was strongly inhibited by ATP and inorganic phosphate (P_i) at all PEP concentrations. At non-saturating (0.5 mM) PEP, half-maximal inhibition was obtained at 1.8 mM ATP or 1.4 mM P_i. The inhibition by both P_i and ATP was largely overcome by 4 mM G-6-P. The specific activity of pyruvate kinase was considerably higher in lactate-, glucose- and glycerol-grown cultures than that of the enzyme catalysing the reverse reaction, pyruvate, phosphate dikinase. It is suggested that the activity of pyruvate kinase in vivo is determined by the balance between activators and inhibitors such that it is inhibited during gluconeogenesis while, during glycolysis, the inhibition is relieved by G-6-P.Abbreviations PEP phosphoenolpyruvate - G-6-P glucose-6-phosphate - P_i inorganic phosphate     

Phosphoenolpyruvate carboxylase from Acetobacter aceti

In Acetobacter aceti growing on pyruvate as the only source of carbon and energy, oxaloacetate (OAA) is produced by a phosphoenolpyruvate (PEP) carboxylase (EC 4.1.1.31). The enzyme was purified 122-fold and a molecular weight of about 380,000 was estimated by gel filtration.The optimum pH was 7.5 and the K _m values for PEP and NaHCO₃ were 0.49 mM and about 3 mM, respectively. The enzyme needed a divalent cation; the K _m for Mn²⁺, Co²⁺ and Mg²⁺ were 0.12, 0.26 and 0.77 mM, respectively. Maximal activity was only obtained with Mg²⁺. Mn²⁺ and Co²⁺ became inhibitory at high concentrations.The activity was inhibited by succinate and, to a lesser extent, by fumarate, citrate, -ketoglutarate, aspartate and glutamate.As compared with the corresponding enzyme from A. xylinum, the PEP carboxylase of A. aceti showed the following differences: a) It had an absolute requirement for acetyl CoA (K _a 0.18 mM) or propionyl CoA (K _a 0.2 mM). b) It was not affected by ADP. c) It was sensitive to thiol blocking agents.Abbreviations PEP phosphoenolpyruvate - OAA oxaloacetate - MW molecular weight - TEMG buffer 50 mM Tris-HCl, pH 7.5, 1 mM EDTA, 5 mM MgCl₂, 1 mM glutathione - HEPES N-2-hydroxyethylpiperazine-N-ethanesulfonic acid     

Regional and subcellular distribution of cysteine sulfinate transaminase in rat nervous system

The distribution of the cysteine sulfinate transaminase activity in adult and newborn rat central nervous system was studied and compared with the distribution of the glutamate oxaloacetate transaminase activity. The subcellular localization of both enzyme activities was also investigated. These experiments suggest that both enzymes, sometimes considered as identical, are different.     

Pyruvate fermentation in Rhodospirillum rubrum and after transfer from aerobic to anaerobic conditions in the dark

The fermentative metabolism of Rhodospirillum rubrum (strain Ha, F₁, S₁) was studied after transfering the cells from aerobic to anaerobic dark culture conditions. Pyruvate was metabolized mainly to acetate and formate, and to a lesser extent to CO₂ and propionate, by all strains. Therefore, pyruvate formate lyase would appear to be the characteristic key enzyme of the dark anaerobic fermentation metabolism in R. rubrum. Strain F₁ and S₁ metabolized the formate further to H₂ and CO₂. It is concluded that this cleavage was catalysed by a formate hydrogen lyase system. Strain Ha was unable to metabolize formate. The cleavage of formate and the synthesis of poly--hydroxy-butyric acid were increased by a low pH value (6.5). Fermentation equations and schemes of the pyruvate metabolism are discussed.