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Biomedical subjects

J C Miller

Publications and source records attributed to J C Miller.

At least 109 records · Page 6Linked to original sources
PubMed1985

Regulation of potato tuber protein accumulation by gibberellic Acid.

Many studies have shown that gibberellic acid (GA(3)) inhibits tuberization in potato (Solanum tuberosum L.). In this study, we have utilized the 40 kilodalton glycoprotein, patatin, as a marker for biochemical events associated with the process of tuberization. To determine the effects of exogenous applications of GA(3) on the induction of the accumulation of this major tuber protein, we measured patatin levels in tubers from treated whole plants, petioles from a single-node cutting system with GA(3) applied in a lanolin paste, and stolon tips cultured in vitro on an inductive medium supplemented with GA(3). In all three systems, GA(3) inhibited the accumulation of patatin and the major 15 and 22 kilodalton tuber proteins. This effect appeared to be selective since most of the other proteins were not affected and, in tubers, at least one protein was stimulated by GA(3). These results suggest that GA(3) can reverse biochemical events of tuberization in tubers as well as prevent the accumulation of the major tuber proteins in other inducible tissues.

Journal Article↗
PubMed1983

Effects of pentobarbital and veratridine on phosphatidylinositol and phosphatidate metabolism in rat parotid acinar cells.

The metabolism of phosphatidylinositol and phosphatidate was studied in isolated rat parotid cells, incubated in a physiological buffer containing [32P]phosphate or [3H]glycerol. Carbamylcholine and epinephrine stimulated 32P incorporation into both of these phospholipids, causing their half-maximal effects at 2 and 0.8 microM respectively. The former concentration is much lower than that anticipated from binding studies. The Hill coefficients for carbamylcholine activation of 32P incorporation were 0.61 +/- 0.05 for phosphatidate and 0.64 +/- 0.05 for phosphatidylinositol. Pentobarbital (0.58 mM) inhibited the increased 32P incorporation caused by 5 microM carbamylcholine but not 100 microM carbamylcholine. Pentobarbital inhibited the incorporation of 3H equally in the presence and absence of epinephrine, indicating that the effect of pentobarbital on 32P incorporation is on turnover and not on de novo synthesis. Veratridine (200 microM) had no effect on phospholipid metabolism in the presence and absence of either carbamylcholine or epinephrine, which contrasts with our previous findings in synaptosomes [J.C. Miller and I. Leung, Biochem. J. 178, 9 (1979)].

Animals↗
PubMed1983

Sex differences in dopaminergic and cholinergic activity and function in the nigro-striatal system of the rat.

Possible sex differences in the balance between dopaminergic and cholinergic activity in the rat striatum were investigated. Female rat show a greater vulnerability to neuroleptic-induced catalepsy compared to male rats. This vulnerability to neuroleptics has a human counterpart in that women show an increased frequency of neuroleptic-induced extrapyramidal syndrome (EPS) compared to men. In humans, EPS can be alleviated by increasing dopaminergic activity or by decreasing cholinergic activity. Conversely, EPS can be precipitated by decreasing dopaminergic activity with neuroleptics, and pre-existing EPS can be made worse with cholinergic agonists. Thus, the presence of EPS in humans or catalepsy in animals, as a result of neuroleptic agents, appears to be related to low dopaminergic and/or high cholinergic activity. In the present studies of sex differences it was found that: (1) cycling female rats had fewer striatal dopamine receptors than did male rats. Estradiol treatment significantly reduced the number in males and also reduced the number, although not significantly in ovariectomized (OVX) rats; (2) cycling female rats had lower apomorphine-induced stereotypy during phases with high estrogen levels as compared to phases with low estrogen levels. Estrogen treatment of male or OVX rats resulted in attenuation of induced stereotypy compared to untreated male or OVX rats; (3) female rats had a significantly higher affinity of striatal cholinergic receptors of 3H-QNB than did males and also had higher choline acetyltransfease activity than male rats. The data from these experiments provide the first direct evidence that estrogen plays a role in shifting the balance toward cholinergic predominance in the striatum, a state that favors the development of cataleposy in female rats and EPS in women.

Acetylcholine↗
PubMed1983

Identification of a cDNA clone for mouse apoprotein A-1 (apo A-1) and its use in characterization of apo A-1 mRNA expression in liver and small intestine.

A cDNA clone for mouse apoprotein A-1 (apo A-1), the major apoprotein of plasma high density lipoproteins, has been identified. In addition to structural and physiological evidence, a genetic polymorphism for mouse plasma apo A-1 has been used to confirm that this DNA sequence corresponds to the apo A-1 gene. Use of this clone in molecular hybridization studies has shown that the concentration of apo A-1 mRNA is similar in liver and small intestine and is constant along the entire length of the small intestine. We provide evidence that the same apo A-1 gene is expressed in both liver and small intestine. Apo A-1 mRNA is also present in the stomach and esophagus at 10-15% the concentration found in small intestine but is undetectable in other tissues (such as large intestine, pancreas, heart, kidney, spleen, and brain). Finally, we show that there is a differential effect of a diet high in saturated fat and cholesterol on apo A-1 mRNA levels in liver and small intestine.

Animals↗
PubMed1982

Digests of protein augment acid-induced canine pancreatic secretion.

To study interactions between intraluminal acid and protein digests, six dogs with chronic gastric and pancreatic fistulas received three sets of intestinal perfusates. The first set contained HCl (1, 2, or 4 mmol/50 ml) and 64 mM D- or L-phenylalanine. The second set contained HCl plus either intact or pepsin-digested bovine serum albumin (BSA); the BSA and HCl were varied so that each 50 ml contained 1, 2, or 4 meq of acid titratable from an initial pH of 2.0 to an end-point pH of 4.5. The third set was identical to the second set except for an initial pH of 3.5. All perfusates were adjusted to 300 mosM and randomly infused at 200 ml/h. L-Phenylalanine enhanced acid-induced bicarbonate and protein outputs, as did pH 2.0 BSA digests. At pH 3.5, only acid-induced protein output was augmented by BSA digests. In additional studies, undigested or digested BSA at pH 7.0 was infused with secretin (82 pmol.kg-1.h-1). Only digested BSA enhanced secretin-induced pancreatic secretion. We conclude that there is an important, albeit complex, interaction between the intestinal acid stimulus and the protein digest stimulus on pancreatic secretion.

Animals↗
PubMed1981

Cholinephosphotransferase in rat lung. The in vitro synthesis of dipalmitoylphosphatidylcholine from dipalmitoylglycerol.

Active substrate preparations of dipalmitoylglycerol were obtained by sonicating dipalmitoylglycerol, phosphatidylglycerol, and Tween 20 together at 65 degrees C. The apparent Vmax for cholinephosphotransferase in lung microsomes was 30 nmol/min/mg of protein for dipalmitoylglycerol-phosphatidylglycerol-Tween 20 substrate preparations and 43 nmol/min/mg of protein for dioleoylglycerol-phosphatidylglycerol-Tween 20 preparations. Sonication at 65 degrees C was required for maximal activity with dipalmitoylglycerol but not for dioleoylglycerol. Highest activity was obtained when diacylglycerol was sonicated with phosphatidylglycerol and Tween 20 although phosphatidylglycerol also increased the activity when added separately. The presence of phosphatidylglycerol was critical particularly with dipalmitoylglycerol as substrate. Phosphatidylinositol, phosphatidylserine, and phosphatidic acid were slightly active but phosphatidylcholine and phosphatidylethanolamine were inactive.

Animals↗
PubMed1981

Evidence for a regulatory role of CTP : choline phosphate cytidylyltransferase in the synthesis of phosphatidylcholine in fetal lung following premature birth.

The sequence of reactions which function to incorporate choline into phosphatidylcholine was investigated in lung from fetuses following premature delivery. The rate of [methyl-14C]choline incorporation by rat lung slices into phosphatidylcholine increases following premature delivery at both 20 and 21 days gestation. The increase in choline incorporation is primarily due to an increased specific activity of phosphorylcholine resulting from a decreased pool size of phosphorylcholine. The decrease in the concentration of phosphorylcholine following premature delivery is apparently caused by an increased activity of cytidylyltransferase which leads to an increase in the conversion of phosphorylcholine to phosphatidylcholine. The total activity of choline kinase, cytidylyltransferase, cholinephosphotransferase and phosphatidate phosphohydrolase did not change significantly. However, the cytidylyltransferase activity in the microsome fraction increased following premature delivery at 20 and 21 days gestation. The amount of cytidylyltransferase in the H form in the cytosol fraction increased following premature delivery at 21 days gestation but not at 20 days gestation. The results are interpreted to indicate that the active form of cytidylyltransferase in lung cells is the membrane-bound enzyme and this form increases following birth resulting in an increased synthesis of phosphatidylcholine.

Animals↗
PubMed1980

Platelet monoamine oxidase as a function of nongenetic factors.

The level of platelet monoamine oxidase (MAO) has been found to be abnormally low in certain types of schizophrenia and in a number of other pathological conditions. It has been suggested that MAO in platelets may be a genetic marker for a subgroup of patients with schizophrenia; however, we have demonstrated that several nongenetic factors influence platelet MAO activity by affecting the platelet rather than the MAO enzyme protein. We have observed platelet MAO activities to be heterogeneously distributed in a given subject's platelet population, heavy platelet fractions having significantly higher specific activity than light platelet fractions. We have also found platelet MAO activity to be significantly correlated with mean platelet volume, platelet protein densities, and protein content per platelet. These changes, which might be induced by drugs and stress, could modify production, mobilization, and clearance of platelets and, hence, influence apparent MAO activity.

Antipsychotic Agents↗