Indole alkaloid biosynthesis: Partial purification of “ajmalicine synthetase” from Catharanthus roseus

The “ajmalicine synthetase” system of $\text{Catharanthus roseus}$ has been partially purified from callus, seedlings and mature plants. On gel filtration of the cell-free extract, four β-D-glucosidase isozymes were observed in seedlings and plants. Only two were present in the callus. A protein peak at 55,000 daltons in all three materials was capable of synthesizing ajmalicine from tryptamine and secologanin in the presence of NADPH. This “ajmalicine synthetase” rapidly lost its ability to synthsize ajmalicine, but retained the β-glucosidase activity.     

Effects of a nonperssor analogue of vasopressin on plasma renin activity and salt and water excretion in water-loaded,anesthetized dogs

The object of this study was to determine the importance of vasoconstrictor activity in the suppression of renin secretion by vasopressin. Arginine vasopressin (AVP) (0.05 and 0.1 ng/kg/min) and a nonpressor analogue of vasopressin, 1-deamino-[4-threonine, 8-D-arginine]-vasopressin (dTDAVP) (0.01 and 0.05 ng/kg/min), were infused intravenously in anesthetized hypophysectomized dogs. Neither dTDAVP nor AVP influenced arterial pressure or heart rate but both suppressed plasma renin activity. Infusion of dTDAVP at 0.01 and 0.05 ng/kg/min suppressed plasma renin activity to 86±4% (p<0.05) and 63±6% (p<0.01) of the control values respectively. Infusion of AVP at 0.05 and 0.1 ng/kg/min suppressed plasma renin activity to 60±8% (p<0.01) and 59±12% (p<0.05) of the central values respectively. dTDAVP and AVP both produced significant increases in sodium excretion. These data demonstrate that vasoconstrictor activity is not required for the effects of vasopressin on renin secretion and sodium excretion.     

Quantitative analyses of ultrastructure and vascularization of the slow muscle fibres of the anchovy

A quantitative study has been made of the ultrastructure and vascularization of slow fibres in the lateral muscles of the European anchovy (Engraulis encrasicolus). Mitochondria and myofibrils occupy 45.5 and 44.3% of total fibre volume respectively. More than 95% of all myofibrils are adjacent to mitchondria. A total of 51 % of the sarcolemma is in direct contact with capillaries with a mean of 12.9 capillaries per fibre. In transverse sections anchovy slow fibr es are considerably flattened (long to short axis 12:1) such that the surface to volume ratio is more than twice that of a cylindrical fibre of the same area (1115 μm²). The capillary surface required to supply l μm³ of mitochondria is 0.18 μm² and the maximum distance between any capillary and mitochondrion 8 μm. T-system and sarcoplasmic reticulum occupy 0.43 and 2.7% of fibre volume respectively. Adaptations for increasing the capacity of skeletal muscle for aerobic work are discussed.     

Direct evidence for the presence of a rotenone-resistant NADH dehydrogenase on the inner surface of the inner membrane of plant mitochondria

Submitochondrial particles (SMP) were produced from Jerusalem artichoke (Helianthus tuberosus L.) mitochondria by sonication and differential centrifugation. The SMP were about 50% inside-out as measured by the access of reduced cytochrome c to cytochrome c oxidase. Uncoupled NADH oxidation (1 mM NADH) by the SMP was 120 nmol O₂ min^?1mg^?1, which was reduced to 98 nmol O₂ min^?1 (mg mitochondrial protein)^?1 in the presence of EGTA. In contrast, the oxidation of NADH by intact mitochondria was completely inhibited by EGTA (from 182 to 14 nmol O₂ min^?1mg^?1). The EGTA-resistant NADH oxidation by the SMP is ascribed to the NADH dehydrogenase(s) on the inside of the inner membrane and exposed to the medium in the inside-out SMP. In the presence of EGTA it could be shown that two NADH dehydrogenase activities were present in the SMP. One had an apparent K_m of 7 μM for NADH, a V_max of 80 nmol NADH min^?1mg^?1, and was rotenone-sensitive. This dehydrogenase is equivalent to the mammalian Complex I NADH dehydrogenase. The other dehydrogenase, which was rotenone-resistant, had a K_m of 80 μM and a V_max of 131 nmol NADH min^?1mg^?1; it is probably responsible for the rotenone-resistant oxidation of organic acids often observed in plant mitochondria. The redox poise of the pyridine nucleotides had only a small effect on the relative rates of the two internal dehydrogenases. Electron flow through these dehydrogenases appears, therefore, to be regulated mainly by the concentration of NADH in the matrix of the mitochondria.     

Incorporation of3H-thymidine into DNA and the activity of alkaline phosphatase in zinc-deficient fetal rat brains

The incorporation of³H-thymidine into DNA in the brains of the 17-day and 20-day old rat fetuses was significantly reduced by maternal zinc restriction during pregnancy. The activity of the enzyme thymidine kinase (EC 2.7.1.21) was similarly reduced in the zine-deprived fetal brains on days 14 and 20 of gestation, but not on day 17. Fetal brain alkaline phosphatase (EC 3.1.3.1) was significantly depressed by maternal zinc deprivation on days 17 and 20 of pregnancy. The data suggest an association between thymidine kinase and the reduced incorporation of³H-thymidine into DNA in the brains of 20-day old fetuses but not in animals on day 17. Alkaline phosphatase was however depressed at this stage. The suggestion is made that because of the complexity of brain development, future biochemical studies in this area should concern specific structures in the brain at particular critical stages during neurogenesis.     

Evolutionary temperature adaptation of fish sarcoplasmic reticulum

Summary Sarcoplasmic reticulum has been isolated from the white muscle of 15 species of teleost fish adapted to diverse thermal environments. Evidence has been obtained that the Ca²⁺-dependent ATPase of fish sarcoplasmic reticulum has undergone evolutionary modification for function at different temperatures. Compared with tropical fish, cold adapted species have higher rates of Ca²⁺ transport and Ca²⁺-ATPase activities at low temperatures. Most species have linear Arrhenius plots over the temperature range 0–30°C. Activation enthalpies (H ) of the ATPase ranged from 53–190 kJ mol^–1 and were positively correlated with environment temperature. Activation entropy (S ) varied from negative values in cold adapted species to positive values in tropical fish.In contrast to the Ca²⁺-ATPase, the basal ATPase of fish sarcoplasmic reticulum showed no relationship between either ATPase activity or thermodynamic activation parameters and environmental temperature.Only the Ca²⁺-dependent ATPase is coupled to Ca²⁺ transport. The percentage of total ATPase activity which is Ca²⁺ activated is higher at low temperatures in cold than in warm adapted species. For example, ratios of Ca²⁺-dependent/total ATPase at 2°C varied from 80–98% in Arctic, Antarctic and North Sea species to only 2–50% in various tropical fish. Above 20°C, similar ratios in the range 80–98% were obtained for all species. The nature of the basal ATPase and mechanisms of temperature adaptation of fish sarcoplasmic reticulum are discussed.Abbreviations ET environmental temperature - EGTA ethylene glycol-bis (-aminolethyl ether)-N, N-tetraacetic acid - HEPES N-2-hydroxylpiperazine-N-2-ethanesulfonic acid - SR sarcoplasmic reticulum     

Correlation of the effect of feeding upon the cell cycle distribution profiles of MPC-11 cells with the relative appearance of [3H]-choline labeled material in microsomal subfractions and other cell fractions

Summary Cultures of mouse plasmacytoma cells (MPC-11) grown within the range 6–23 × 10⁵ cells/ml showed considerable variation in cell cycle distribution profiles and also differences with regard to relative amounts of microsomal subfractions. The variability of appearance of heavy rough (HR) and light rough (LR) microsomal subfractions was not merely due to differences in nutritional state of the culture. Cultures containing a high S/G₂ + M cell cycle distribution ratio showed a high content of HR microsomal membranes; as the S/G₂ + M ratio decreased, so too decreased the amount of HR material whilst the amount of LR microsomal membranes increased. The results indicate that there is a direct correlation between phase of cell cycle and both amount and relative distribution of rough microsomal membranes, the smooth fraction (S), however, remains relatively unchanged.     

DISAGGREGATION OF POLYSOMES IN FETAL ORGANS AND MATERNAL BRAIN AFTER ADMINISTRATION OF d-LYSERGIC ACID DIETHYLAMIDE IN VIVO

The intravenous administration of d-lysergic acid diethylamide (LSD) to pregnant female rabbits induced hyperthermia as well as disaggregation of polysomes in fetal organs and maternal brain. The LSD-induced polysome shift in maternal brain and fetal organs was not due to an activation of ribonuclease or associated with alterations in the levels of free amino acids. Pretreatment with the receptor blocking agents haloperidol and pizotyline blocked both LSD-induced polysome shift in maternal brain and fetal organs and LSD-induced hyperthermia. Fine dissection of adult rabbit brain showed that the extent of LSD-induced disaggregation of polysomes does not exhibit any marked regional variation.     

Steroid sulphatase levels in XX males,including observations on two affected cousins

Summary Quantitative assays of steroid sulphatase in XX males have shown that some individuals have two functional loci, and others only one. Two affected cousins, who cannot share the same X-chromosome, nevertheless have male levels of steroid sulphatase, suggesting functional abnormality of the X chromosome.The hypothesis is advanced that these and other unusual features of X-chromosome function in some XX males, could be explained if such cases were due to an autosomal mutation, exercising its effect by causing abnormal inactivation of a subterminal area of Xp which normally escapes the inactivation process.