Search PubMed⌕ Search

Biomedical subjects

I Chanarin

Publications and source records attributed to I Chanarin.

At least 91 records · Page 5Linked to original sources
PubMed1980

The neuropsychiatry of megaloblastic anaemia.

The neuropsychiatric states of 50 patients with vitamin B12 deficiency and 34 patients with folate deficiency presenting with megaloblastosis in a general hospital were examined and compared. Abnormalities of the nervous system were found in two-thirds of both groups. Peripheral neuropathy was the most common condition associated with vitamin B12 deficiency and affective disorder with folate deficiency. The proportions of patients with organic mental change were similar in the two groups. Subacute combined degeneration of the cord was an uncommon complication and occurred only in the patients with vitamin B12 deficiency. There was no relation between haematological and neuropsychiatric abnormalities. The neuropsychiatry of megaloblastic anaemia seen in this study of patients presenting to haematologists or general physicians contrasts with that reported previously, before haematological techniques for separating the two deficiencies were introduced.

Adolescent↗
PubMed1980

Vitamin B12 regulates folate metabolism by the supply of formate.

Nitrous oxide (N2O) inactivates the B12 coenzyme involved in methionine synthesis and interrupts formation of the folate coenzyme (folate polyglutamate). Normal synthesis of folate polyglutamate is restored in the N2O-treated rat when folate carrying a single carbon unit is supplied at the formate level of oxidation. The activity of the enzyme, formyl synthetase, which links formate to tetrahydrofolate, is increased after exposure to nitrous oxide. Formate is normally derived from the oxidation of methyl groups, methionine being an important source. It is suggested that failure of methionine synthesis leads to a paucity of formate and in turn to inadequate formylation of tetrahydrofolate. Formyltetrahydrofolate is the required substrate for the synthesis of folate polyglutamate, and impairment of this step in turn compromises general folate metabolism.

Animals↗
PubMed1980

Utilization of [2-14C]tetrahydropteroylglutamic acid and 5-[G-3H]methyltetrahydropteroylglutamic acid as substrates for folate polyglutamate synthesis in fruit bats: effect of vitamin B-12-deficiency.

[2-14C]Tetrahydropteroylglutamic acid and 5-[G-3H]methyltetrahydropteroylglutamic acid were given intraperitoneally to fruit bats. Folate polyglutamates were formed in the liver from both substrates in different amounts and at different rates. The methylfolate pool appeared to remain separate from the tetrahydrofolate pool. More polyglutamate was formed from tetrahydropteroylglutamic acid than from 5-methyltetrahydropteroylglutamic acid. There was a fall in the folate content of the liver in the vitamin B-12-deficient bat and a more rapid incorporation of folates into polyglutamates but thereafter a more rapid loss of the labelled folate from liver.

Animals↗
PubMed1980

The effect of nitrous oxide inactivation of vitamin B12 on rat hepatic folate. Implications for the methylfolate-trap hypothesis.

Rats exposed to N20 show a decrease in liver folate to about 25% of the initial value after 10 days. There is a transient increase in the amount of 5-methylterrahydropteroylpolyglutamate in the first 24 h, but thereafter the content decreases. The level of 5-methyltetrahydropterolymonoglutamate declines without any transitory increase. The transient accumulation of 5-methyltetrahydropteroylpolyglutamate is due to failure of methionine synthetase. Thereafter the decrease in the amount of methylfolate makes it improbable that trapping of methylfolate is the explanation for failure of folate metabolism in vitamin B12 deficiency.

Animals↗
PubMed1980

Marrow cells from patients with untreated pernicious anaemia cannot use tetrahydrofolate normally.

Folate analogues were added to human bone marrow cells to determine their effect on deoxyuridine utilization in the deoxyuridine suppression test. Formyltetrahydrofolates fully corrected the impairment of dU utilization in pernicious anaemia marrows but tetrahydrofolate was relatively ineffective. All these analogues were effective in megaloblastic marrows from folate deficient patients. Formyltetrahydrofolates also enhanced dU utilization by normal human marrows whereas methyltetrahydrofolate reduced its use. In terms of the methylfolate trap hypothesis, the expectation that cobalamin-deficient marrows would be able to use tetrahydrofolate normally was not realized.

Anemia, Megaloblastic↗
PubMed1980

Inactivation of methionine synthase by nitrous oxide.

Exposure of rats to a 50% N2O/oxygen mixture led to a rapid loss of methionine synthase activity in both liver and brain. This enzyme has vitamin B12 as a cofactor. There was impaired conversion of deoxyuridine to deoxythymidine by bone marrow cells and this defect followed loss of methionine synthase activity. There was no homocystinuria. Withdrawal of N2O was followed by a relatively slow recovery of methionine synthase activity over four days. The inactivation of vitamin B12 by N2O promises to be a valuable tool in the study of vitamin B12 metabolism.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1980

Sex-related differences in the haematological effects of excessive alcohol consumption.

Mean corpuscular volume (MCV) was measured at presentation in 320 hospital patients with a history of excessive alcohol consumption. The MCV of the 94 women thought to be actively drinking more than 80 g/day of alcohol was 101.3 fl compared with 96.7 fl in their male counterparts. Alcohol consumption, age, smoking habits, prevalence of inadequate diet, or serum and red cell folate levels did not differ significantly between men and women. It is suggested that MCV is a better indicator of excessive alcohol consumption in women than in men, and that women are more susceptible to the haematological toxicity of alcohol.

Adult↗
PubMed1980

Studies in chronic lymphocytic leukaemia II. Lymphocyte markers, cellular and humoral immunity and the effect of treatment.

Observations were made on 15 patients with chronic lymphocytic leukaemia, 3 with non-Hodgkin's lymphoma, and 18 healthy controls. These include characterization of lymphocytes, assessment of humoral and cell-mediated immunity and the effect of treatment. Those responding to therapy showed a disappearance of 'null' lymphocytes from the blood with improvement in clinical and haematological parameters. Their immune capacity, however, remained unchanged or continued to deteriorate.

Adult↗
PubMed1979

Characterization of endogenous folate and incorporation of labelled folates into the brain of the South African fruit bat.

Folate in the brain of the South African fruit bat consists of 10-formyltetrahydropteroyglutamic acid and the tri-, tetra- and penta- forms of 5-methyltetrahydropteroylglutamic acid. Following parenteral injection, only 5-[3H]-methyltetrahydropteroylglutamic acid was taken up by the brain, but none of a dose of 14C-labelled tetrahydropteroylglutamic acid was detectable. Only trace smounts of the 5-methyltetrahydropteroylglutamic acid were converted into the formyl compounds and a small amount of methyltetrahydropteroyltriglutamic acid appeared after 96 h. There was no significant difference in vitamin B-12-deficient animals.

Animals↗