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Biomedical subjects

S G Smith

Publications and source records attributed to S G Smith.

At least 127 records · Page 7Linked to original sources
PubMed1976

Effect of unit dose and route of administration on self-administration of morphine.

Rats were implanted with intravenous or intragastric cannulas and allowed to self-administer morphine sulfate in doses of 0 (saline), 0.03, 0.1, 0.3, 1.0, 3.0, and 10.0 mg/kg/infusion. For the intravenous route the number of infusions decreased with increasing unit dose, while the amount self-administered was directly related to unit dose. However, for the intragastric route the number of infusions first increased and then decreased as unit dose was elevated, while the amount self-administered again increased with unit dose. Comparisons between routes showed that for intragastric subjects the number of infusions and amount self-administered both were lower at the two lowest doses but higher for all other doses. These results support the expectation that intravenous injection should produce more potent reinforcing effects than intragastric administration.

Animals↗
PubMed1976

A dose-response comparison between methadone and morphine self-administration.

Rats were allowed to self-administer a solution of 0.9% saline, or 0.01, 0.03, 0.1 or 0.3 mg/kg/infusion of methadone hydrochloride or 0.03, 0.1 or 0.3 mg/kg/infusion of morphine sulfate. The results showed that number of infusions taken was an inverse function of unit dose, while amount of drug self-administered (mg/kg) was a direct function of unit dose. The data also indicated that more morphine than methadone was self-administered.

Animals↗
PubMed1976

Macrocyclic intermediates in the biosynthesis of porphyrins.

The hepta-, hexa- and penta-carboxylic porphyrins found in the faeces of rats poisoned with hexachlorobenzene have been separated by high-pressure liquid chromatography and characterized largely by spectroscopie methods. Their structures were confirmed by total synthesis, as part of a programme in which eleven of the fourteen hepta-, hexa- and penta-carboxylic porphyrins derived from uroporphyrin III have now been synthesized as their methyl esters. The four isomeric heptacarboxylic and three of the pentacarboxylic porphyrinogens have been incubated with haemolysates of chicken erythrocytes, and they are all converted into protoporphyrin IX but at different rates. On the basis of this and other evidence we conclude that the decarboxylation of uroporphyrinogen III to coproporphyrinogen III is a stepwise process taking place by a preferred pathway (both in normal and abnormal metabolism); the acetic acid groups are decarboxylated in a sequential clockwise fashion starting with that on the D ring and followed by those on the A, B and C rings. In the poisoned rats the uroporphyrinogen decarboxylase enzyme (or group of enzymes) is probably partially inhibited and the pentacarboxylic porphyrinogen with an acetic acid group on ring C accumulates. The latter is then transformed by a side pathway into dehydroisocoproporphyrinogen and thence into dehydroisocoproporphyrin and its congeners.

Animals↗
PubMed1976

Hepta- and hexa-carboxylic porphyrinogen intermediates in haem biosynthesis.

In the course of our studies on intermediates in normal and abnormal metabolism of porphyrins we have synthesised a number of porphyrins related to uroporphyrin-III and compared them with materials isolated from natural sources. In the present paper we show that the corresponding porphyrinogens are all metabolised to protoporphyrin-IX by haemolysates of chicken erythrocytes, but at different rates. The results are discussed in relation to our conclusions concerning the preferred pathway of degradation of uro'gen-III to coproporphyrinogen-III, which indicate a clockwise sequence of decarboxylation reactions.

Animals↗
PubMed1976

Pentacarboxylic intermediates in haem biosynthesis.

The incorporation of the four possible type III porphyrinogens into protoporphyrin is described and their various rates or conversion are discussed. The techniques used involved the incubation of the porphyrinogens in chicken red cell haemolysates followed by extraction and characterisation of the end products on HPLC and TLC. Porphyrin 5 b c d was shown to be more slowly incorporated than porphyrins 5 a b d, 5 a c d and 5 a b c. The relevance of these findings to an understanding of the porphyrin excretion pattern in hepato-erythrocitic porphyria is considered.

Animals↗
PubMed1976

Incubation of double labelled coproporphyrinogen with chicken red cell haemolysates, chemical and TLC fractionation of extracts.

Further evidence is presented for the enzymic conversion of protoporphyrinogen to protoporphyrin by observing the loss of 3H counts by 3H and 14C labelled coproporphyrinogen when incubated in chicken red cell haemolysates. Use was made of chemical and TLC fractionation of porphyrin extracts after incubation and a loss of half the 3H was again found. Evidence is presented for the role of harderoporphyrinogen as a natural intermediate in this conversion. The relevance of the findings in the porphyrias, and in particular variegate porphyria, is discussed. It is suggested that the enzymic process involved in the conversion of protoporphyrinogen to protoporphyrin may be deficient in variegate porphyria.

Animals↗
PubMed1975

Two active forms of RD-114 virus DNA polymerase in infected cells.

Two forms of DNA polymerase are present in RD-114-infected human, dog, and mink cells, but are not detectable in uninfected cells. The two enzymes are indistinguishable catalytically and immunologically, but differ with respect to molecular weight and elution position from (dT)12-18-cellulose and phosphocellulose. The large enzyme (equivalent 95,000 daltons) is found in the infected cells, but not the virions produced by these cells. The virions contain only the smaller enzyme (equivalent 70,000 daltons). The larger form may represent a mammalian viral equivalent to the beta subunit of avian RNA tumor virus DNA polymerase.

Cell Line↗
PubMed1975

Thin layer chromatography and counter-current analysis in porphyrias.

The porphyrin metabolism of 100 patients with porphyria and 351 of their relatives has been studied. Thin layer chromatography of methyl esters of the urinary porphyrin was undertaken in sixty-six patients with different types of porphyria, and forty-five relatives, seventeen patients with hepatic cirrhosis, three patients with lead poisoning and twenty normal control subjects. This investigation was also made on the stools of thirty-six patients with porphyria, and then of their relatives. Countercurrent analysis of the bile of nine selected patients with porphyria was also undertaken. The results provide some evidence that symptomatic hepatic porphyria may be familial. Thin layer chromatography was decisive in the characterization of a new type of porphyria described recently by the authors (hepato-erythrocytic porphyria). The counter-current examination of the bile showed the absence of the 'S 411' porphyrin in all the nine cases investigated.

Bile↗
PubMed1975

The use of thin layer chromatography in the separation of free porphyrins and porphyrin methyl esters.

Thin layer chromatographic techniques for the separation and subsequent quantification of free porphyrins, coproporphyrin isomers and the methyl esters of porphyrins are described including a 2-dimensional system. The relevant RFs for a wide range of porphyrins are given. These methods have been in use in Cardiff and Barcelona for a number of years and were used in the survey of cases described by Pinol et al. (1975) which resulted in the discovery of the new porphyria, hepato-erythrocytic porphyria.

Chromatography, Thin Layer↗