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In Vitro Tryptophan Catabolism by Leishmania donovani donovani Promastigotes (1992)

LEELAYOOVA, SAOVANEE ; MARBURY, DEAN ; RAINEY, PETRIE M. ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

The @journal of eukaryotic microbiology 39 (1992), S. 0

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ISSN: 1550-7408

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: . Metabolism of tryptophan by promastigotes of Leishmania donovani donovani was investigated in cells suspended in a simple buffer solution supplemented with glucose. Metabolites from supernatant and lysed cell pellets were analyzed by capillary gas liquid chromatography and 13C nuclear magnetic resonance spectroscopy, with structural confirmation by gas liquid chromatography-mass spectrometry. Tryptophan does not appear to serve as a carbon energy source for L. d. donovani promastigotes since parasites could survive for only short periods in buffer containing tryptophan without glucose, levels of tricarboxylic acid cycle intermediates remained unchanged in the presence of added tryptophan and label from [13C]tryptophan was not detected in any of the intermediates. Leishmania d. donovani catabolized l-tryptophan via aminotransferase and aromatic lactate dehydrogenase reactions to form one major end product, indole-3-lactic acid. The activity of aromatic lactate dehydrogenase required manganese and was NADH-dependent in these organisms that lack lactate dehydrogenase. Promastigotes taken from the mid-log stage of growth produced higher concentrations of indole-3-lactic acid than those from the stationary stage. Conservation of a similar tryptophan catabolic pathway among four Leishmania species suggests the pathway is physiologically important to the parasites themselves.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1550-7408.1992.tb01329.x

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Thyroid function in lead smelter workers: absence of subacute or cumulative effects with moderate lead burdens (1998)

Schumacher, Cynthia ; Brodkin, C. Andrew ; Alexander, Bruce ; [et al.]

Springer

International archives of occupational and environmental health 71 (1998), S. 453-458

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ISSN: 1432-1246

Keywords: Key words Lead ; Lead poisoning ; Thyroid diseases ; Thyroid hormones ; Pituitary gland

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine

Notes: Abstract Objective: To evaluate the effect of low to moderate occupational lead exposure on thyroid function we conducted a cross-sectional study of 151 male lead smelter workers. Methods: Parameters of thyroid function were assessed in relation to both subacute and cumulative lead exposure over a 10-year employment period. Blood lead levels, obtained from plant surveillance records, were used to establish four ordinal levels of current and cumulative exposure (〈15, 15–24, 25–39, and ≥40 μ g/dl). Results: Mean values for the lowest as compared with the highest current exposure group were similar for thyroxine (T4: 6.8 versus 6.1 μ g/dl), estimated free thyroxine (EFT4: 1.6 ng/dl in both groups), and thyroid-stimulating hormone (TSH: 1.8 versus 1.7 mIU/l); there was no evidence of a significant trend for diminished thyroid function associated with increasing current lead exposure. Similarly, no significant difference was observed for T4, EFT4, or TSH in relation to the 10-year cumulative exposure or for adjusted analyses controlling for potential confounders, including age and alcohol use. Conclusion: In contrast to studies observing thyroid dysfunction in the setting of high lead exposure and related clinical poisoning, our findings weigh against a significant physiologic effect on thyroid function at lower levels (〈60 μ g/dl) of occupational lead exposure.