Biomedical subjects

R J LaFrance

Publications and source records attributed to R J LaFrance.

6 recordsLinked to original sources

PubMed1990

Addition of L-glutamine to total parenteral nutrition and its effects on portal insulin and glucagon and the development of hepatic steatosis in rats.

Infusion of total parenteral nutrition (TPN) with excess carbohydrate calories leads to hepatic steatosis in rats and is associated with an elevated portal insulin/glucagon molar ratio. Previously we have shown that adding glucagon to TPN prevents and reverses hepatic steatosis in rats, possibly by increasing hepatic lipid export. It has been reported that steatosis is eliminated in rats by the addition of L-glutamine to TPN. In this study, we examined the effect of glutamine on portal insulin and glucagon levels and the development of hepatic steatosis. Adult rats (n = 19) received internal jugular catheters: Group 1 (n = 6), saline (3 cc/hr) and chow ad libitum; Group 2 (n = 7), 25% dextrose base TPN; Group 3 (n = 6), 25% dextrose base TPN with 2% glutamine. The infusion rate of TPN was 1.2 cc/100 g body wt/hr. Daily nitrogen balance was determined and at 7 days, portal venous blood was drawn for insulin and glucagon radioimmunoassay, livers were removed for histology and lipid content determination, and the small intestines were removed for mucosal protein and DNA content determination. Panlobular vacuolization of the hepatocytes was noted on histology in Group 2 (TPN) while Group 1 (chow) and Group 3 (TPN + glutamine) showed normal liver morphology. Hepatic lipid content was significantly elevated in Group 2 (P less than 0.05). The portal insulin/glucagon molar ratio was increased because of excessive portal venous insulin in Group 2 (TPN). In contrast, portal glucagon was significantly elevated while the insulin/glucagon ratio and hepatic lipid content did not increase above control levels in the glutamine-supplemented Group 3 rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1986

Differential cytotoxicity and DNA-damaging effects produced in human cells of the Mer+ and Mer- phenotypes by a series of 1-aryl-3-alkyltriazenes.

A series of arylalkyltriazenes has been investigated for its differential cytotoxicity towards the HT-29 (Mer+) and BE (Mer-) cell lines and for its ability to cause DNA strand breaks and cross-links. A monomethyltriazene (MMPT) and some hydroxymethyltriazene derivatives capable of generating the monomethyltriazene in situ were preferentially cytotoxic to the BE cell line when compared with the HT-29 cell line. The differential toxicity of MMPT is very similar to the analogous monochloroethyltriazene. In contrast, the dimethyl- and monoethyltriazenes in the series display reduced toxicity towards the BE cell line with little or no differential toxicity between the BE and HT-29 cell lines. MMPT and monochloroethyltriazene caused single strand DNA breaks in the two cell lines, whereas little or no DNA strand breaks were observed in either cell line after exposure to the monoethyl- or dimethyltriazene. However, these lesions could not account for the differential cytotoxicity observed. In measurements of DNA interstrand cross-linking none of the agents tested, including monochloroethyltriazene and MMPT, was found to cause such linkages. In contrast to previous results obtained with bifunctional monochloroethylating agents, which produced a similar differential cytotoxicity between these two cell lines, our results tend to suggest that lesions other than DNA interstrand cross-links may be responsible for the mechanisms of cell killing by chloroethylating agents.

Alkylation↗

PubMed1985

Triazene metabolism. IV. Derivatives of hydroxymethyltriazenes: potential prodrugs for the active metabolites of the anti-tumour triazene, DTIC.

A series of derivatives of the anti-tumour hydroxymethyltriazenes have been investigated for activity in vivo and in vitro. Acetoxymethyltriazenes are active in vivo against the TLX5, P388 and PC6 tumours in mice, and inhibit the growth of TLX5, Np and Li cells in vitro without metabolic activation. The acetoxymethyltriazenes are comparable with the hydroxymethyltriazenes and monomethyltriazenes in their spectrum of activity and thus appear to be prodrugs for these species. On the other hand, a methoxymethyltriazene was found to be active on the TLX5 tumour in vivo, but did not inhibit the growth of Np cells in vitro. This latter observation is consistent with the anticipated chemical stability of the methoxymethyltriazene and the requirement for metabolic O-demethylation to generate an active species. Acetoxymethyltriazenes do not require metabolic intervention and break down chemically in phosphate buffer to the hydroxymethyltriazene, which in turn loses formaldehyde to give the incipient methylating agent, the monomethyltriazene.

Animals↗

PubMed1985

Triazene metabolism. V. Chemical and biological properties of N,N-bis-[(1-aryl-3-methyltriazen-3-yl)-methyl]-methylamines: potential prodrugs for the cytotoxic monomethyltriazenes.

N,N-Bis-[(1-aryl-3-methyltriazen-3-yl)-methyl]-methylamines, 'bistriazenes', have anti-tumour activity against the TLX5 and PC6 mouse tumours and inhibit the growth of tumour cells growing in culture, without metabolic activation. The biological activity of the bistriazene appears to derive from facile hydrolysis to the cytotoxic monomethyltriazene, Ar-N = N-NHMe, and it is suggested that the bistriazene may be a good prodrug from for the 'active' metabolite of the anti-tumour dimethyltriazene, Ar-N-N = N-NME2. A kinetic study of the bistriazene hydrolysis shows that the reaction is retarded by electron-withdrawing substituents in the aryl group. The results can be interpreted by a mechanism in which the bistriazene behaves as an 'animal' (i.e. N-CH2-N) and undergoes anchimerically assisted fragmentation, via an iminium ion intermediate, to the monomethyltriazene.

Animals↗

PubMed1985

Warfarin absorption after massive small bowel resection.

Small bowel resection is often accompanied by malabsorption and nutritional deficiencies. Malabsorption of drugs may also occur; however, few reports have been published. We treated five patients with oral warfarin for thrombotic problems after substantial small bowel resection. All five had a documented hypoprothrombinemic response to the warfarin (patient prothrombin time: control greater than 1.5). Maintenance warfarin doses were up to 10 mg/day. Oral warfarin appears to be well absorbed after removal of the majority of the jejunum and ileum. This may indicate a proximal site of warfarin absorption.

Adult↗

PubMedDate not supplied

Fat emulsion effects on prothrombin time in warfarin anticoagulated patients: an in vitro study.

The effect of lipid emulsions on prothrombin time in blood from anticoagulated patients was determined. Blood samples were obtained from 23 patients therapeutically anticoagulated with warfarin (prothrombin time 1.3-2.0 x control). Varying amounts of an intravenous lipid emulsion (Intra-lipid) were added to the blood to simulate concentrations seen in vivo with a constant lipid infusion. The prothrombin time was measured on the plasma from these samples and compared to the prothrombin time of the plasma samples without lipid. The mean decrease in prothrombin times were: 0.29 sec at 50 micrograms/ml, 0.23 sec at 100 micrograms/ml, and 0.29 sec at 200 micrograms/ml. All concentrations showed a statistically significant decrease (p less than 0.05) when compared to the control by the Scheffe test. Lipid emulsions appear to decrease the prothrombin times in anti-coagulated patients. The differences however, were small and not of clinical significance at the concentrations tested.

Fat Emulsions, Intravenous↗