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Biomedical subjects

J F Thompson

Publications and source records attributed to J F Thompson.

At least 307 records · Page 17Linked to original sources
PubMed1983

A controlled trial of cyclosporine in renal transplantation with conversion to azathioprine and prednisolone after three months.

Thirty-five patients given an HLA-DR-incompatible cadaver kidney that was diuresing immediately after transplantation were randomly allocated to treatment with cyclosporine alone for 3 months followed by conversion to azathioprine and prednisolone (AP), or to conventional treatment with AP. Although many patients had to be converted to AP before 90 days because of rejection requiring more than two treatment courses of high-dose i.v. methylprednisolone, 16 of 21 grafts were functioning at 3 months, and 12 of 14 grafts in the control group were functioning. However 3 further grafts were lost from chronic rejection in the control group, and none were lost from chronic rejection in the cyclosporine group. All but one patient on cyclosporine had depressed renal function, and in all these patients function improved on conversion to AP. This depression of renal function is attributed both to cyclosporine nephrotoxicity and to a low-grade rejection reaction, the latter suggesting that the addition of steroids to cyclosporine might be beneficial in some patients. The strategy of a three-month course of cyclosporine followed by conversion to AP provides satisfactory immunosuppression, and it may be of value if long-term side effects of cyclosporine emerge with further experience.

Adult↗
PubMed1983

The management of pancreatic carcinoma: a review of 173 cases.

Pancreatic carcinoma is an increasingly common malignancy, cure of which is rarely feasible. Ideal management involves the safe and effective palliation of symptoms once the diagnosis has been established beyond reasonable doubt and the unlikely possibility of cure by radical surgery ruled out. In this retrospective study of 173 patients, management fell short of the ideal. Histological confirmation of the diagnosis was obtained in only 42% of patients, and there was a 16% reoperation rate because of the failure of an initial palliative procedure to relieve actual or potential biliary or gastric outlet obstruction. Still more patients developed recurrent obstructive jaundice or duodenal obstruction but did not undergo further surgery. To achieve optimal palliation, it is recommended that a gastroenterostomy be performed whenever a palliative operation is undertaken for the relief of obstructive jaundice, and that biliary drainage be accomplished by anastomosis of bowel to the common hepatic duct rather than the gall-bladder whenever possible, to minimize the risk of recurrent obstruction. It is further recommended that an attempt be made to obtain a tissue diagnosis in every case, since other methods of diagnosis are unreliable.

Adult↗
PubMed1982

The biosynthesis and processing of high molecular weight precursors of soybean glycinin subunits.

The predominant storage protein of soybean seed, glycinin, is composed of two heterogeneous classes of related subunits, the acidics (Mr approximately 38,000) and the basics (Mr approximately 22,000). Immunoreaction of polypeptides translated in vitro from isolated seed mRNA using antibodies prepared against either purified acidic or basic subunit groups precipitated precursor polypeptides of Mr = 60,000 to Mr = 63,000. High pressure liquid chromatography fingerprinting of trypsin-generated fragments from in vitro synthesized precursors showed fragments specific to both acidic and basic subunits. No mature acidic or basic subunits were detected in vitro translation reactions by either immunoprecipitation or high pressure liquid chromatography fingerprinting. Pulse-labeling of cotyledons growing in culture with [3H]glycine showed rapid accumulation of label in glycinin precursors of Mr = 59,000 to Mr = 62,000. Although in vivo synthesized precursors had slightly greater electrophoretic mobility than in vitro synthesized precursors, little label initially appeared in mature glycinin subunits. After several hours of continued cotyledon growth in absence of label, precursors were processed and label accumulated in both acidic and basic subunit groups. Recombinant plasmids were prepared by reverse transcription of soybean seed mRNA, and clones which encode glycinin precursors were identified by heteroduplex-hybridization of translatable messages. Northern blot analysis of seed mRNA shows the mRNA-encoding glycinin precursors to migrate at Mr = 0.71 X 10(6) on agarose gels, corresponding to approximately 2050 nucleotides. This is sufficiently large to encode a polypeptide consisting of both a glycinin acidic and basic subunit.

Chromatography, High Pressure Liquid↗
PubMed1982

Identification of a site of psoralen crosslinking in E. coli 16S ribosomal RNA.

We have developed a 2-dimensional gel method for identification of RNA sequences crosslinked by the intercalative drug 4'-hydroxymethyl-4,5',8-trimethylpsoralen (HMT). This method is being used to localize such sites in E. coli ribosomal RNA. We report here the identification of a site for HMT crosslinking within positions 434 and 497 of 16S rRNA. We suggest a likely site for HMT intercalation, in which residues U548 and U473 become crosslinked via the drug.

Base Sequence↗
PubMed1982

Dependence of 4'-(hydroxymethyl)-4,5',8-trimethylpsoralen photoaddition on the conformation of ribonucleic acid.

The photoaddition of 4'-(hydroxymethyl)-4,5',8-trimethylpsoralen (HMT) to different conformational states of RNA was studied. Poly(U), poly(A,U) (random copolymer), poly(A-U) (alternating copolymer), poly(A) . poly(U) (double stranded), and poly(U) . poly(A) . poly(U) (triple stranded) were reacted with HMT at different temperatures and salt concentrations. The conformation of the polymers was monitored by UV absorption and circular dichroism. It was found that the rate of HMT photoaddition changed dramatically at structural transitions in the RNA. The alternating copolymer poly(A-U) was found to have the highest rate of addition. Low salt and temperature produced maximal incorporation.

Circular Dichroism↗
PubMed1982

Cimetidine and acetylcysteine as antidote for acetaminophen overdose.

The incidence of acetaminophen overdose, often resulting in hepatotoxicity or even death, steadily increases as its use (instead of aspirin) as an antipyretic and analgesic increases. Acetaminophen-induced hepatotoxicity is though to be dependent on the dose ingested and the activity of the cytochrome P450 enzyme system. The actual hepatotoxic mechanism is believed to be the formation of a toxic tissue arylating metabolite(s). Current therapy attempts to inactivate this toxic metabolite(s) with acetylcysteine, as opposed to inhibiting its production. Because cimetidine can inhibit the cytochrome P450 mixed-function oxidase system, we believe it could decrease the production of the hepatotoxic acetaminophen metabolite(s) providing an effective antidote to be used in conjunction with acetylcysteine.

Acetaminophen↗
PubMed1981

Identification of the modified nucleotides produced by covalent photoaddition of hydroxymethyltrimethylpsoralen to RNA.

The reaction between RNA and 4'hydroxymethyl-4,5',8-trimethylpsoralen has been studied. Both natural RNA and synthetic RNAs were used. The base specificity of the reaction was found to be the same in natural RNA, homopolymers, and mononucleotides. Uridine was found to be the most reactive base in all cases. The kinetics of formation and reversal of monoadducts and crosslinks has been examined. Paper electrophoretic conditions are described which provide a separation of the monoaddition and crosslinked photoproducts. The relative and absolute amounts of monoadducts and crosslinks can be determined very accurately with this system. Paper electrophoresis provides good separations of the different photoproducts. The mobilities of the products are a simple function of their molecular weights and charges.

Chemical Phenomena↗
PubMed1981

Diazepam-cimetidine drug interaction: a clinically significant effect.

Cimetidine has been shown to inhibit the liver microsomal metabolism of the benzodiazepines diazepam and chlordiazepoxide, resulting in an increase in half-life and decrease in the clearance of these two drugs. Patients receiving the combination of diazepam and cimetidine have been noted to be more sedated than when given an equal dose of diazepam alone. Many benzodiazepines undergo N-dealkylation and hydroxylation via the cytochrome P450 oxidase system. Cimetidine is thought to bind to cytochrome P450 oxidase and to interfere with many drugs using this path way. Oxazepam and lorazepam are two benzodiazepines not oxidatively metabolized by cytochrome P450, but are glucuronidated by glucuronyl transferase and are, therefore, not subject to metabolic inhibition by cimetidine. Thus, when clinically indicated, oxazepam and lorazepam may be the benzodiazepines of choice to use in combination with cimetidine to eliminate the clinically significant drug interaction seen with diazepam and chlordiazepoxide.

Anti-Anxiety Agents↗