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Biomedical subjects

T F Slater

Publications and source records attributed to T F Slater.

At least 145 records · Page 8Linked to original sources
PubMed1970

A filtration method for the separation of cell sap from the large-particle fraction of rat liver suspensions, enabling the rapid measurement of nucleotide distributions.

A simple method is described that allows a rapid separation of a cell-sap fraction from the large-particle fraction of rat liver suspensions. The method is based on the filtration under suction of liver suspensions through Millipore filters that retain nuclei, mitochondria and some of the endoplasmic-reticulum fraction, but allow quantitative passage of cell sap into a collecting tube. The cell sap may be separated in this manner within 2min of the death of the rat. The method was applied to study the intracellular distribution of ATP and of the nicotinamide-adenine dinucleotides and the results obtained were compared with those obtained after separating the cell sap by a rapid centrifuging procedure. The percentage of total liver ATP in the cell sap was found to be 46% by the filtration method and more than 70% by the centrifuging procedure. Corresponding figures found for the distribution of NADP(+)+NADPH were 40 and 49% respectively.

Adenosine Triphosphate↗
PubMed1970

Liver adenosine triphosphate content and bile flow rate in the rat.

The effects of a number of hepatotoxic and other agents on the ATP content of rat liver are described. Changes in the distribution of ATP between the cell sap and the large-particle fraction were determined at intervals after rats had been dosed with various substances. Ethionine produced a rapid decrease in total liver ATP but no alteration in its intracellular distribution. Carbon tetrachloride, sodium salicylate, dimethylnitrosamine, 2,4-dinitrophenol, icterogenin, sodium succinate, sodium malonate and sodium taurocholate did not significantly alter the total ATP content of liver in the periods studied but changes in intracellular distribution were found. Carbon tetrachloride, malonate and taurocholate decreased, and salicylate treatment increased, the proportion of ATP in the cell sap. Treatment with sodium phenobarbitone increased the total liver ATP and the total amount of ATP in the cell sap. The changes in ATP concentration and in the intracellular distribution of ATP are correlated with changes previously reported in bile flow (Delaney & Slater, 1969). No general correlation was found between changes in total ATP and changes in bile flow rate, but there was a relationship between changes in bile flow and in ATP content in the case of ethionine. With the exception of taurocholate and icterogenin, which possibly act on a membrane site, an approximate correlation was found between changes in bile flow and changes in the amount of ATP in the cell sap. The findings are discussed in terms of possible mechanisms for biliary secretion.

Adenosine Triphosphate↗
PubMed1969

The effects of carbon tetrachloride on rat liver microsomes during the first hour of poisoning in vivo, and the modifying actions of promethazine.

The effects of an oral administration of carbon tetrachloride on various liver microsomal and supernatant components were studied 1hr. and 2hr. after dosing. The modifications of such early changes resulting from a concomitant administration of promethazine together with the carbon tetrachloride were also investigated. The microsomal components studied were: cytochromes P-450 and b(5); inorganic pyrophosphatase; NADH- and NADPH-cytochrome c reductases; NADH- and NADPH-neotetrazolium reductases; a lipid-peroxidation system associated with the oxidation of NADPH and stimulated by ADP and Fe(2+). NAD- and NADP- DT-diaphorases were measured in the supernatant solution remaining after isolation of liver microsomes, and the distribution of RNA phosphorus between the microsomes and supernatant solution was also determined. Carbon tetrachloride produced a rapid fall in inorganic pyrophosphatase activity, a rather slower decrease in cytochrome P-450 content of the microsomes and small increases in the activities of NADH-cytochrome c reductase and neotetrazolium reductases. The activities of NADPH-cytochrome c reductase, the NADPH-ADP/Fe(2+)-linked lipid-peroxidation system, DT-diaphorases and the content of cytochrome b(5) in the microsomes were unchanged. There was also a loss of RNA phosphorus from the microsomes into the supernatant solution. The RNA phosphorus redistribution, the decrease in inorganic pyrophosphatase and the increases in neotetrazolium reductase activities were at least partially prevented by a concomitant dosing with promethazine. However, the decrease in cytochrome P-450 was not affected by promethazine treatment. These early changes are discussed in terms of the liver necrosis produced by carbon tetrachloride and which is greatly retarded in its onset by the administration of promethazine.

Animals↗
PubMed1968

The inhibitory effects in vitro of phenothiazines and other drugs on lipid-peroxidation systems in rat liver microsomes, and their relationship to the liver necrosis produced by carbon tetrachloride.

1. The effects of several phenothiazine derivatives on lipid-peroxidation systems in rat liver microsomes were studied and the results are considered in relation to the hepatotoxic action of carbon tetrachloride. 2. The lipid-peroxidation system coupled to NADPH(2) oxidation and stimulated by an ADP-Fe(2+) mixture is strongly inhibited in vitro by promethazine (50% inhibition at 29mum). Chlorpromazine and Stelazine also inhibit the peroxidation system but are less effective than promethazine. 3. The effects of promethazine on three other systems involving oxygen uptake (sulphite oxidation, orcinol oxidation and mitochondrial succinate oxidation) were also studied. Promethazine does not inhibit these systems to the same extent as it does the NADPH(2)-ADP-Fe(2+) lipid-peroxidation system. 4. Promethazine also produces an inhibition of the NADPH(2)-ADP-Fe(2+) system in liver microsomes after administration in vivo. It is concluded that the inhibition involves the interaction of the drug (or a metabolite of it) with the microsomal electron-transport chain. 5. Several other compounds known to protect the rat against liver necrosis after the administration of carbon tetrachloride were tested for inhibitory action on the NADPH(2)-ADP-Fe(2+) system. No clear correlation was observed between effectiveness in vivo as a protective agent and inhibitory effects on the NADPH(2)-ADP-Fe(2+) system in vitro. 6. Promethazine was found to inhibit the stimulation of lipid peroxidation produced in rat liver microsomes by low concentrations of carbon tetrachloride. This effect occurs at a concentration similar to that observed in vivo after administration of a normal clinical dose.

Adenine Nucleotides↗
PubMed1967

Oxidized and reduced nicotinamide-adenine dinucleotide phosphate in tissue suspensions of rat liver.

1. The concentrations of NADP and NADPH(2) in homogenates of rat liver (expressed as mug./g. wet wt. of tissue homogenized) were compared with values obtained from intact samples of liver taken from the same female rat. With 0.25m-sucrose alone as the suspending medium, or in combination with tris buffer or 0.01-0.1m-nicotinamide, considerable decreases in the sum of the NADP+NADPH(2) concentrations were occasionally observed during 30min. storage of homogenates at 0 degrees . However, addition of 0.5m-nicotinamide+5mm-tris buffer to 0.25m-sucrose for use as a suspending medium maintained the sum of the NADP+NADPH(2) concentrations in homogenates at the level found in intact tissue for at least 30min. at 0 degrees . 2. The effects of freezing intact tissue and homogenates in liquid nitrogen before the extraction of NADP and NADPH(2) were studied. Freezing alone appears to convert a significant amount (approx. 30%) of liver NADPH(2) into an equivalent amount of NADP in intact tissue. This is discussed in terms of the ;bound NADP' reported by Burch, Lowry & Von Dippe (1963). 3. The intracellular distributions of NADP and NADPH(2) in intracellular fractions of rat liver were studied by using a modified centrifuging scheme that allows extraction of the isolated fractions to be performed within 45min. of killing the animal. Approx. 50% of the total NADP+NADPH(2) was found in the large-particle fractions and the remaining 50% was mostly in the soluble fraction of the cell. 4. Further investigations are reported on the nature of ;bound NADP' in rat liver. Most of this material appears associated with the ;nuclear' (containing nuclei, debris, erythrocytes etc.) or large-mitochondrial fractions, or both, obtained by low-speed centrifuging of rat-liver homogenates. 5. Although in some experiments the variations produced in the concentration of NADPH(2) present in large-particle fractions were followed by similar changes in that of ;bound NADP', in other cases no such direct relationship was obtained. Addition of phenazine methosulphate, for example, consistently lowered the concentration of NADPH(2) yet raised the concentration of ;bound NADP' in rat-liver mitochondrial fractions.

Animals↗
PubMed1966

Liver nucleotides in acute experimental liver injury induced by dimethylnitrosamine and by thioacetamide.

1. The concentrations of the nicotinamide-adenine dinucleotides in rat liver have been determined at intervals during the period 1-24hr. after feeding adult female rats with dimethylnitrosamine or thioacetamide. 2. The administration of dimethylnitrosamine resulted in a rapid decrease in the sum of NAD+NADH(2). This sum was decreased by 40% 3hr. after dosing. 3. Dimethylnitrosamine administration also produced an overall decrease in the NADP+NADPH(2) but this decrease was not so early nor as marked as that found for NAD+NADH(2). 4. The changes produced by thioacetamide were quite different from those obtained with dimethylnitrosamine. Thioacetamide produced a temporary rise in the NAD+NADH(2) followed by a small fall. The NADP+NADPH(2) was little changed in the early hours after dosing with thioacetamide but had decreased by approx. 15% 18hr. after administration. 5. These changes are discussed in terms of the known hepatotoxic actions of dimethylnitrosamine and thioacetamide, and are compared with previously reported changes found after the administration of carbon tetrachloride.

Amides↗
PubMed1966

Nicotinamide-adenine dinucleotides in acute liver injury induced by ethionine, and a comparison with the effects of salicylate.

1. The effects of single doses of ethionine or sodium salicylate on the nicotinamide-adenine dinucleotide content of rat liver have been studied. 2. There was no significant change in the sum of NAD+NADH(2) during the early period (0-2hr.) of the liver injury induced by ethionine but there was a decrease in this value of approx. 30% by 4hr. after administration. 3. Ethionine had no significant effect on the NADP+NADPH(2) during the first 2hr. period after administration. The sum then decreased to a value approx. 70% of the control by 3hr. after dosing but showed a partial recovery at the 4hr. period before decreasing again in later stages of the poisoning. 4. Salicylate produced a very rapid decrease in the NADP+NADPH(2) in the liver after intraperitoneal injection. After 1hr. the decrease was approx. 30% of the initial value; the sum slowly returned towards the normal range during the following 4hr. 5. A high parenteral dose of salicylate was found to cause only a small depression in the concentration of ATP in rat liver in contrast with the rapid depletion produced by ethionine. 6. These results are discussed in terms of the liver disturbances produced by ethionine and salicylate.

Adenosine Triphosphate↗