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Biomedical subjects

M J Graham

Publications and source records attributed to M J Graham.

42 records · Page 3Linked to original sources
PubMed1988

Increases in cytochrome P-450 mediated 17 beta-estradiol 2-hydroxylase activity in rat liver microsomes after both acute administration and subchronic administration of 2,3,7,8-tetrachlorodibenzo-p-dioxin in a two-stage hepatocarcinogenesis model.

Administration of single doses of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (10 micrograms/kg) increased estradiol 2-hydroxylase (E2OHase) activity approximately 2-fold in liver microsomes of female rats but had no effect on E2OHase activity in hepatic microsomes of male rats. In contrast, TCDD increased P-450d (an enzyme which has a high turnover number for E2OHase in a reconstituted enzyme system) 10- to 20-fold in livers of both male and female rats. The discrepancy between the increases in P-450d and E2OHase activity in liver microsomes of TCDD-induced rats was abolished by the addition of exogenous purified P-450 reductase to the microsomal assays for E2OHase, suggesting that reductase was limiting in the in vitro assays. When E2OHase activity was assayed in the presence of exogenous reductase, TCDD increased E2OHase 2-fold and 4-fold respectively in liver microsomes of male and female rates. Antibody to P-450d completely inhibited the increase in E2OHase activity in liver microsomes of TCDD-treated male and female rats, but had little effect on E2OHase activity in liver microsomes of untreated male or female rats. These data indicate that P-450d is responsible for the increase in E2OHase activity in TCDD-treated rats, but other P-450 isozymes are responsible for constitutive E2OHase activity. Biweekly administration of 1.4 micrograms/kg of TCDD for 30 weeks as a potential promoter of hepatocarcinogenesis increased the volume of the liver occupied by gamma-glutamyl transpeptidase (GGT)-positive foci in livers of female rats given a necrogenic dose of diethylnitrosamine (DEN) (200 mg/kg) as the initiator. Biweekly doses of 0.14-1.4 micrograms/kg TCDD in this model also increased P-450d (7-fold) and E2OHase activity maximally (4-fold) in DEN-initiated rats. Moreover, initiation with DEN substantially enhanced the effects of the low dose of TCDD on both hepatic microsomal P-450d and E2OHase activity.

Animals↗
PubMed1987

Zwitterionic analogues of cimetidine as H2 receptor antagonists.

A series of analogues of the H2 receptor histamine antagonist cimetidine have been synthesized in which the dipolar cyanoguanidine group has been replaced by a number of zwitterionic moieties. Although none of the compounds is more effective than cimetidine in blocking histamine-stimulated tachycardia on the isolated guinea pig atrium, the activities of most of the compounds possessing rigid dipoles can be accounted for on the basis of dipole orientation relative to the common side chain and by considering the active species in each case to be the zwitterion. These findings are in general agreement with those found for analogues having conjugated groups as dipoles.

Animals↗
PubMed1986

Dipole moment in relation to H2 receptor histamine antagonist activity for cimetidine analogues.

The activities of a series of H2 receptor histamine antagonists structurally related to cimetidine (1) have been compared to investigate the effect of replacing the cyanoguanidine moiety by other neutral, dipolar groups. Antagonist activity, as measured in vitro on the histamine-stimulated guinea pig right atrium, was found to be very sensitive to relatively minor structural changes. Differences in H2 antagonist activity are accounted for by dipole moment orientation and lipophilicity and are rationalized in terms of an optimum requirement for alignment of a hydrogen-bonding moiety in the antagonist with respect to the receptor and desolvation effects at the receptor. The most active compound in the series is the 2-amino-3-nitropyrrole derivative 5, which combines a near-optimal dipole orientation with high lipophilicity.

Animals↗
PubMed1983

Persistent leucine sensitivity following partial pancreatectomy and diazoxide treatment. Therapeutic response.

Hyperinsulinemic hypoglycemia secondary to nesidioblastosis persisted in a 4-year-old girl despite a 95% pancreatectomy and high-dose diazoxide treatment. Current literature suggests that dietary treatment, specifically protein restriction, of patients who are receiving diazoxide is ineffective and that further surgical pancreatectomy is required. However, in this patient, marked leucine sensitivity was demonstrated and a subsequent reduction in leucine intake eliminated hypoglycemia and the need for total or nearly total pancreatectomy. Therefore, dietary alteration should be considered in some patients with hyperinsulinism as an adjunct to other medical treatment.

Child, Preschool↗
PubMedDate not supplied

Antisense properties of 2'-O-dimethylaminooxyethyl (2'-O-DMAOE) oligonucleotides.

Antisense oligonucleotides with 2'-O-(2-[N,N-dimethyl)aminooxy]ethyl) or (2'-O-DMAOE) modification were synthesized and evaluated for nuclease resistance and pharmacology both in vitro and in vivo. This modification exhibits very high nuclease resistance and efficacy in various biological (ICAM-1, C-raf and PKC-alpha) targets.

Animals↗