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Biomedical subjects

J A Watson

Publications and source records attributed to J A Watson.

At least 37 records · Page 2Linked to original sources
PubMed1992

Isopentenoid synthesis in embryonic Drosophila cells: prenylated protein profile and prenyl group usage.

It has been established that vertebrates and yeasts modified a unique subset of polypeptides with farnesyl and geranylgeranyl residues. This observation has been extended to Drosophila Kc cells. [3H]Mevalonate was incorporated into 54 Kc cell peptides (18-92 kDa). As reported for mammalian cells, most of the labeled peptides had molecular weights between 21 and 27 kDa. C18 radio-HPLC tryptic digest profiles for delipidized, [3H]mevalonate-labeled (a) insect (Drosophila and Spodoptera frugiperda) and mammalian (Chinese hamster ovary met 18-2b) cells, (b) Kc cell nuclear lamin, and (c) a 23.5-kDa purified Kc cell GTP-binding protein were compared and analyzed. [35S]Cysteine-labeled Kc cells yielded a tryptic digest radio-HPLC profile which was congruent with that for [3H]mevalonate-labeled cells. A significant fraction (30-33%) of the doubly labeled tryptic peptides were eluted with greater than or equal to 93% acetonitrile. Kc cell nuclear lamin tryptic digests yielded a single 3H-labeled product which migrated as S-farnesylcysteine. The Kc cell 23.5-kDa GTP-binding protein's 3H-labeled oligopeptide(s)/amino acid(s) was geranylgeranylated and its tryptic digest profile was representative of prenylated proteins whose oligopeptides eluted with greater than or equal to 93% acetonitrile. Moreover, the 3H-labeled oligopeptide/amino acid profiles plus prenyl group patterns for [3H]mevalonate-labeled Kc and mammalian cell total extracts were similar. Collectively, these observations supported a prenylated protein spectrum and prenyl group usage as highly conserved eukaryotic cellular characteristics.

Animals↗
PubMed1992

Early management of displaced ankle fractures.

We reviewed all ankle fractures over a 6-year period and selected those with greater than 33 per cent subluxation of the talus to assess the early management and the incidence of skin complications. A total of 60 fractures were identified; none were reduced as an emergency procedure on admission to the accident department and seven developed ischaemic necrosis over the medial skin incision. We suggest that early reduction in the accident and emergency department may help to prevent this complication.

Ankle Injuries↗
PubMed1992

Urea and creatinine generation and removal in a pregnant patient receiving peritoneal dialysis.

Peritoneal dialysis is the preferred form of dialysis during pregnancy because it is continuous and lacks the wide variation in chemistries, weight and blood pressure, and avoids the use of anticoagulation necessary during hemodialysis. This is a case report of a successful vaginal delivery of a 35 week healthy baby boy to a patient with end stage renal disease receiving peritoneal dialysis. Approximately one year after starting peritoneal dialysis for end stage renal disease of unknown etiology, this patient was noted to be pregnant during a transplant evaluation. BUN and creatinine generation increased with pregnancy. In order to keep the plasma BUN less than 50 mg/dl and creatinine less than 5 mg/dl, BUN and creatinine removal were increased by increasing the liters of dialysate from 8 liters to 16 liters per day. The peritoneal volume decreased from an initial 2 liters to 0.8 liter per exchange. The frequency of exchange increased. This was accomplished at home with a cycler so the patient was able to continue self care and maintain a quality of life. Peritoneal equilibration test during pregnancy did not change.

Adult↗
PubMed1991

Malignant chondroid syringoma--a rare cause of secondary bone tumour.

Sweat-gland carcinomas are very rare, comprising only 0.01% of primary tumours of the skin. Malignant chondroid syringoma is the least common variety, of which less than twenty cases have been recorded. We report a case in which this tumour presented as an osteolytic secondary deposit.

Adenoma, Sweat Gland↗
PubMed1990

Sterol-mediated regulation of mevalonic acid synthesis. Accumulation of 4-carboxysterols as the predominant sterols synthesized in a Chinese hamster ovary cell cholesterol auxotroph (mutant 215).

Chinese hamster ovary-215 (CHO-215) mutant cells are auxotrophic for cholesterol. Berry and Chang (Berry, D. J., and Chang, T. Y. (1982) Biochemistry 21, 573-580) suggested that the metabolic lesion was at the level of 4-methyl sterol oxidation. However, the observed cellular accumulation of lanosterol was not consistent with a defect at this metabolic site. With the use of a novel Silica Sep Pak sterol separation procedure, we demonstrated that 60-80% of the acetonesoluble lipid radioactivity in [5-3H]mevalonate-labeled CHO-215 cells was incorporated into acidic sterols. 7(8),Cholesten-4 beta-methyl,4 alpha-carboxy,3 beta-ol was the dominant end product. In addition to this acidic sterol, 7(8),24-cholestadien,4 beta-methyl,4 alpha-carboxy,3 beta-ol and 7(8),24-cholestadien,4 alpha-carboxy,3 beta-ol were also isolated. Incubation of cell-free extracts with [3H]7(8)-cholesten-4 beta-methyl, 4 alpha-carboxy,3 beta-ol and pyridine nucleotides confirmed that CHO-215 4-carboxysterol decarboxylase activity was less than 1% of that for wild type cells. Thus, a correspondence between decreased 4-carboxysterol decarboxylase activity and the spectrum of accumulated sterol products by intact CHO-215 cells was demonstrated. No detectable cholesterol was synthesized by CHO-215 cells. 3H-Product accumulation studies demonstrated that 7(8),24-cholestadien, 4 beta-methyl,4 alpha-carboxy,3 beta-ol increased prior to its subsequent saturation at the delta 24 carbon. Furthermore, the steady state ratio for delta 24-saturated acidic sterols/unsaturated acidic sterols was dependent on media cholesterol source and amount. Finally, the accumulated acidic sterol(s) were not regulatory signal molecules for the modulation of 3-hydroxy-3-methyl-glutaryl coenzyme. A reductase activity in response to cholesterol availability.

Animals↗
PubMed1989

Conservative management of a Yersinia enterocolitica hepatic abscess.

Yersinia hepatic abscesses are rare, and are more likely to occur in patients with iron overload. A diabetic patient with haemochromatosis presented with a hepatic abscess due to Yersinia enterocolitica, which was treated successfully by the use of a single antibiotic.

Diabetes Mellitus, Type 1↗
PubMed1988

Regulation of cholesterol metabolism in a slow-growing hepatoma in vivo.

Cholesterol metabolism and its regulation are altered in hepatomas as compared to normal liver. We investigated parameters of cholesterol metabolism and their regulation in rats bearing the well-differentiated Morris hepatoma 9108. The numbers of membrane associated receptors recognizing chylomicron remnants, the lipoproteins that deliver dietary lipid to the liver, were substantially decreased in the 9108 tumor relative to the host liver. Cholesterol synthetic rates were 2-3-fold higher in the tumor, while the activity of 3-hydroxy-3-methylglutarylcoenzyme A reductase (EC 1.1.1.88), a rate-limiting enzyme for sterol synthesis, was elevated 6-14-fold. Although tumor free and esterified cholesterol contents were elevated, the activity of acylcoenzyme A:cholesterol acyltransferase (EC 2.3.1.26), the enzyme responsible for intracellular sterol esterification, was unchanged. Similar to the host liver, cholesterol synthesis and 3-hydroxy-3-methylglutarylcoenzyme A reductase were inhibited in the tumor when rats were fed a diet containing cholesterol, cholate and lard, and there was no effect on the numbers of chylomicron remnant receptors. Administering an intravenous bolus of very low density lipoproteins obtained from hypercholesterolemic rats caused an inhibition of tumor reductase activity, but had little effect on cholesterol content or cholesterol esterification. Thus, hepatoma 9108 expressed quantitative differences in cellular parameters involved in the uptake, metabolism, and synthesis of cholesterol and their susceptibility to regulation when compared with the host liver. These differences are best explained by changes in the hepatoma of multiple factors involved in the regulation of normal hepatic cholesterol metabolism.

Animals↗
PubMed1988

Isopentenoid synthesis in isolated embryonic Drosophila cells. Farnesol catabolism and omega-oxidation.

Kc cells divert minimally 40% of their mevalonate carbon to n-fatty acids and unidentified compounds covalently linked to macromolecules (Havel, C., Rector, E. R., II, and Watson, J. A. (1986) J. Biol. Chem. 261, 10150-10156). Furthermore mevalonate carbon diversion appears to occur at the polyprenyl 1-pyrophosphate level. This report summarizes initial efforts to define the mevalonate carbon diversion pathway. We demonstrate that Kc cell extracts readily metabolize [14C]farnesyl 1-pyrophosphate and [14C]farnesol, via common intermediates, to identical 14C-products. Two of the major 14C-products were identified as trans,trans-3,7,11-trimethyl-2,6,10-dodecatrien-1,12-dioic acid and trans-3,7-dimethyl-2,6-decadien-1,10-dioic acid. Similar acids were also synthesized by supplemented rat liver extracts incubated with [14C]farnesol. We conclude that (a) mevalonate carbon diversion at the level of polyprenyl 1-pyrophosphate is a viable metabolic strategy, (b) polyprenols are oxidized to alpha,omega-prenyl dicarboxylic acids which are catabolized from the omega-terminus, and (c) this metabolic process is not limited to insect cells.

Animals↗
PubMed1986

Isopentenoid synthesis in isolated embryonic Drosophila cells. Possible regulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity by shunted mevalonate carbon.

Our previous studies (Watson, J. A., Havel, C. M., Lobos, D. V., Baker, F. C., and Morrow, C. J. (1985) J. Biol. Chem. 260, 14083-14091) suggested that a matabolite, distal to isopentenyl 1-pyrophospate (IPP), served as a regulatory signal for sterol-independent modulation of Kc cell 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity. This report summarizes efforts to localize the potential source of the post-IPP regulatory signal molecule. We found no direct correlation between mevalonate-mediated suppression of Kc cell HMG-CoA reductase activity and the rates of [1-14C]-, [3-14C]-, [5-14C]-, or [5-3H]mevalonate incorporation into either carbon dioxide, neutral lipids, water, or water-soluble isopentenoid pyrophosphate esters. [1-14C]Mevalonate's rate of conversion to 14CO2 (a measure of total isopentenyl 1-pyrophosphate synthesis) was minimally 5-fold greater than that for neutral isopentenoid lipid synthesis (measured with either [5-3H]-, [3-14C]-, or [5-14C]mevalonate). However, [5-3H]mevalonate's rate of conversion into [3H]H2O (measure of shunted mevalonate carbon) was equivalent or greater than that measured for neutral isopentenoid lipid synthesis. [5-14C]Mevalonate radioactivity was incorporated into macromolecules and n-fatty acids. Kc cell extracts (100,000 X g supernatant fluid) readily oxidized alcohols with the following activity sequence: geraniol = nerol greater than farnesol = dimethylallyl alcohol greater than geranylgeraniol, isopentenyl alcohol, and allyl alcohol. Oxidation required NAD, and ethanol was not a substrate. We conclude that (a) Kc cells shunted a significant fraction (greater than or equal to 40%) of their post-IPP carbon to prenols for oxidative catabolism and (b) that shunted mevalonate carbon may play a significant role in the mevalonate-mediated regulation of Kc cell HMG-CoA reductase activity.

Alcohols↗
PubMed1986

Isoprenoid synthesis in Halobacterium halobium. Modulation of 3-hydroxy-3-methylglutaryl coenzyme a concentration in response to mevalonate availability.

Halobacterium halobium was evaluated as a potentially simpler biological model to study the regulation of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity (content) in response to mevalonate availability. H. halobium's HMG-CoA reductase was soluble and required NADPH as its reduced coenzyme. Maximum HMG-CoA reductase activity (4-10 nmol/min/mg of soluble protein) was obtained in buffers which contained 3.5 M KCl. Mevinolin (a) blocked growth of H. halobium, (b) was a competitive inhibitor of HMG-CoA reductase (Ki = 20 nM), (c) did not cause the paradoxical increase in assayable reductase activity, as reported for eukaryotic cells, and (d) caused a rapid (within 30 min) 8-12-fold accumulation of intracellular HMG-CoA. Mevalonate blocked and reversed mevinolin-mediated HMG-CoA accumulation. Although mevinolin-treated cell's growth was restored by mevalonate, HMG-CoA reductase's activity was not. Thus, H. halobium is a unique biological model which allows one to study the regulation of intracellular HMG-CoA concentration and not HMG-CoA reductase activity (content) in response to mevalonate availability.

Acyl Coenzyme A↗
PubMed1986

The relations between type A behavior, clinically relevant behavior, academic achievement, and IQ in children.

The relation of Type A behavior to IQ, academic achievement, and several clinically relevant dimensions of behavior in children was assessed in 873 fourth, fifth, and sixth graders by means of the Matthews Youth Test for Health (MYTH), the Cognitive Abilities Test (CAT), the Iowa Tests of Basic Skills (ITED), and the teachers' form of the Missouri Children's Behavior Checklist (MCBC-T). The MYTH and its competitiveness and impatience-aggression subscales were found to be differentially related to academic achievement and to account for a small but significant portion of the variance in achievement not accounted for by IQ. The subscales of the MYTH were found to be highly correlated with several clinically familiar dimensions of children's behavior. The significance of these findings for the construct validity of the MYTH is discussed.

Achievement↗
PubMed1985

Isoprenoid synthesis in isolated embryonic Drosophila cells. Sterol-independent regulatory signal molecule is distal to isopentenyl 1-pyrophosphates.

Embryonic Drosophila cells (Kc cells) were used to further characterize sterol-independent modulation of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity. 3-Methyl-3-5-dihydroxyvalerate (mevalonate), 3-fluoromethyl-3,5-dihydroxyvalerate (fluoromevalonate), and 3-ethyl-3,5-dihydroxyvalerate (homomevalonate) were tested as modulators. Although mevalonate caused a rapid, reversible suppression of reductase activity, fluoro- and homomevalonate increased activity; fluoromevalonate was more effective than homomevalonate. Mevalonate, added simultaneously with fluoromevalonate, blocked the analogue's effect on Kc cell reductase activity. However, mevalonate did not suppress an established fluoromevalonate increase in HMG-CoA reductase activity. Fluoromevalonate blocked [1-14C, 5-3H]mevalonate conversion to 14CO2- and 3H-labeled lipids and [3H] mevalonate 5-pyrophosphate accumulated. Neither protein nor RNA synthesis were required for mevalonate-mediated suppression of reductase activity. However, fluoromevalonate's effect on reductase activity required protein synthesis. Furthermore, in the absence of protein synthesis, fluoromevalonate-stabilized Kc cell HMG-CoA reductase activity. We have concluded that mevalonate, fluoromevalonate, homomevalonate, and compactin (mevinolin) modulated HMG-CoA reductase activity because they altered isoprenoid carbon flow to a post-isopentenyl 1-pyrophosphate regulatory, signal molecule.

Animals↗
PubMed1983

Isoprene synthesis in isolated embryonic Drosophila cells. I. Sterol-deficient eukaryotic cells.

Since insects are cholesterol auxotrophs, we analyzed the apparent paradox presented by an established cell line (Kc cells) from Drosophila embryos which grew in media which contained less than 0.05 micrograms/ml of sterols. Fresh Drosophila embryos contained 3.7 micrograms of 3 beta-hydroxysterols/mg of protein; however, Kc cells had maximally 0.50 micrograms of 3 beta-hydroxysterols/mg of protein. Kc cells, grown in media which contained cholesterol, showed the presence of sterol in their plasma and intracellular membranes. Kc cells did not synthesize sterols or any apparent replacement lipophilic molecule. However, two major compounds which comigrated with ubiquinone and dolichol were synthesized from radioactive mevalonate and acetate. Cholesterol incorporation into Kc cell membranes did not significantly alter total phospholipid head or acyl group composition. Similar observations were obtained with Schneider's Drosophila cell line I and a mosquito (Aedes albopictus) cell line. Our results (a) challenged current concepts that sterols or related replacement isopentenoid molecules were required for eukaryotic membrane structure, (b) demonstrated that marked alterations in eukaryotic membrane sterol composition was insufficient to change total phospholipid head and/or acyl group composition, and (c) set the stage for the use of a eukaryotic cell to examine the regulation of 3-hydroxy,3-methylglutaryl coenzyme A reductase activity independent of a requirement for sterol synthesis.

Animals↗
PubMed1983

Isoprene synthesis in isolated embryonic Drosophila cells. II. Regulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity.

We used an established Drosophila cell line (Kc cells), which neither synthesized nor required cholesterol for growth, to determine if sterol and nonsterol modulators of vertebrate 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity were also active in this biological system. Drosophila HMG-CoA reductase was membrane-bound and required NADPH for catalysis. In contrast to the vertebrate enzyme, Kc cell HMG-CoA reductase activity was not modulated by cholesterol (10 micrograms/ml), human low density lipoprotein (83 micrograms of cholesterol/ml), or oxygenated sterols (5-10 micrograms/ml). However, mevalonate caused a rapid strong suppression of Kc HMG-CoA reductase activity; 18 microM R-mevalonate produced 50% suppression of the enzyme within 24 h. Compactin, a competitive inhibitor, decreased HMG-CoA reductase activity in Drosophila embryo cell-free extracts with an apparent Ki of 1.0 nM. Kc cells, grown in the presence of compactin, had a HMG-CoA reductase specific activity 5- to 10-fold higher than untreated cells. Mevalonate blocked this increase. We have concluded that HMG-CoA reductase activity in Kc cells is (a) not responsive to feedback inhibition by sterols, and (b) is controlled by a fundamental sterol-independent regulatory process. The signal for modulation of HMG-CoA reductase activity may be mevalonate and/or its magnitude conversion to a nonsterol isopentenoid precursor and/or end product. These observations may have broader validity, not only for other insect cells, but for eukaryotic cells in general.

Animals↗