M. P. Pratap Rudra

Inhibition of tyrosine aminotransferase by β-N-oxalyl-L-α,β-diaminopropionic acid, the Lathyrus sativus neurotoxin

Abstract: Species differences in susceptibility are a unique feature associated with the neurotoxicity of β‐N‐oxalyl‐l‐α,β‐diaminopropionic acid (l‐ODAP), the Lathyrus sativus neurotoxin, and the excitotoxic mechanism proposed for its mechanism of toxicity does not account for this feature. The present study examines whether neurotoxicity of l‐ODAP is the result of an interference in the metabolism of any amino acid and if it could form the basis to explain the species differences in susceptibility. Thus, Wistar rats and BALB/c (white) mice, which are normally resistant to l‐ODAP, became susceptible to it following pretreatment with tyrosine (or phenylalanine), exhibiting typical neurotoxic symptoms. C57BL/6J (black) mice were, however, normally susceptible to l‐ODAP without any pretreatment with tyrosine. Among the various enzymes associated with tyrosine metabolism examined, the activity of only tyrosine aminotransferase (TAT) was inhibited specifically by l‐ODAP. The inhibition was noncompetitive with respect to tyrosine (Ki = 2.0 ± 0.1 mM) and uncompetitive with respect to α‐ketoglutarate (Ki = 8.4 ± 1.5 mM). The inhibition of TAT was also reflected in a marked decrease in the rate of oxidation of tyrosine by liver slices, an increase in tyrosine levels of liver, and also a twofold increase in the dopa and dopamine contents of brain in l‐ODAP‐injected black mice. The dopa and dopamine contents in the brain of only l‐ODAP‐injected white mice did not show any change, whereas levels of these compounds were much higher in tyrosine‐pretreated animals. Also, the radioactivity associated with tyrosine, dopa, and dopamine arising from [14C]tyrosine was twofold higher in both liver and brain of l‐ODAP‐treated black mice. Thus, a transient increase in tyrosine levels following the inhibition of hepatic TAT by l‐ODAP and its increased availability for the enhanced synthesis of dopa and dopamine and other likely metabolites (toxic?) resulting therefrom could be the mechanism of neurotoxicity and may even underlie the species differences in susceptibility to this neurotoxin.

Influence of different cultural conditions on photoproduction of hydrogen by Rhodopseudomonas palustris KU003.

Photoproduction of hydrogen by Rhodopseudomonas palustris KU003 under different cultural conditions with various carbon and nitrogen sources was investigated. Hydrogen production was measured using a Gas chromatograph. Malate promoted more amounts of hydrogen production under anaerobic light conditions than anaerobic dark conditions. Cumulative hydrogen production by the organism was recorded at various time intervals. Incubation period of 120 hrs was optimum for production of hydrogen. pH 7.0±0.4 was optimum for production of hydrogen. L-glutamic acid was a good nitrogen source for production of hydrogen. Growing cells produced more amount of hydrogen than resting cells. Significance of the above results in presence of existing literature is discussed.

Factors influencing the production of hydrogen by the purple non-sulphur phototrophic bacterium Rhodopseudomonas acidophila KU001

Rhodopseudomonas acidophila KU001 was isolated from leather industry effluents and the effect of different cultural conditions on hydrogen production was studied. Anaerobic light induced more hydrogen production than anaerobic dark conditions. Growing cells produced more amounts of hydrogen between 96 and 144 h of incubation. Resting and growing cells preferred a pH of 6.0 ± 0.24 for hydrogen production. Succinate was the most preferred carbon source for the production of hydrogen while citrate was a poor source of carbon. Acetate and malate were also good carbon sources for hydrogen production under anaerobic light. Among the nitrogen sources, R. acidophila preferred ammonium chloride followed by urea for production of hydrogen. L‐tyrosine was the least preferred nitrogen source by both growing and resting cells.

In vitro Activation of Protein Kinase C by β-N-oxalyl-l-α, β-diaminopropionic acid, the Lathyrus sativus Neurotoxin

Abstractβ-N-oxalyl-l-α,β-diaminopropionic acid (l-ODAP) toxicity has been associated with lathyrism; a spastic paraparesis caused by excessive dietary intake of the pulse Lathyrus sativus. We investigated the effect of Lathyrus neurotoxin l-ODAP on protein kinase C (PKC) activity under in vitro conditions. l-ODAP activated phosphorylation activity of purified chick brain PKC. Both lysine-rich (histone III-S) and arginine-rich (protamine sulfate) substrate phosphorylation was enhanced in the presence of l-ODAP. The activation is concentration dependent, and maximal activation is observed at 100 μM concentration. Protamine sulfate phosphorylation was enhanced by 47%, whereas histone III-S phosphorylation was enhanced by 50% over PS/PDBu/Ca2+ dependent activity. The nontoxic d-isomer (d-ODAP) did not affect both histone III-S and protamine sulfate phosphorylation activity. These results indicate that l-ODAP taken up by neuronal cells could also contribute to PKC activation and so be associated with toxicity.

In vivo metabolism of β-N-oxalyl-L-α,β-diaminopropionic acid: the Lathyrus sativus neurotoxin in experimental animals

A comparative study of the metabolism of 1,2,3 14C-ODAP and 4,5 14C-ODAP in mice, rats and chicks has been carried out. Following oral administration of 1,2,3 14C-ODAP to either black or white mice, nearly 16 % of the radioactivity appeared in the expired CO2 within 8 h, while in the rat only 3 % of it appeared and in chicks it was less than 2 %. No 14CO2 appeared in the expired air in mice given 4,5 14C-ODAP. Electrophoregrams of the spot urine samples from the animals given 1,2,3 14C-ODAP showed the presence of one radioactive metabolite (metabolite-1) in addition to ODAP. While the urine from rats and mice given 4,5 14C-ODAP indicated the presence of metabolite-1 as well as 14C-oxalate, in chicks, however, no 14C-oxalate was present and only metabolite-1 could be detected. The results indicate that ODAP can to some extent undergo oxidation in vivo in mice (and to a lesser extent in rats) leading to the formation of CO2 and oxalate and a similar pathway might be more prominent in humans leading to a near complete oxidation of ODAP. Copyright

Photoproduction of Hydrogen under Different Cultural Conditions by Alginate Immobilized Rhodopsedomonas palustris KU003

Rhodopsedomonas palustris KU003 was immobilized in alginate and its hydrogen producing abilities were assessed. Maximum hydrogen production took place between 120 and 144 hrs in most carbon sources. Alginate immobilization induced higher amount of hydrogen in malate-, lactate-, and succinate-containing medium in Rps. palustris. Incubation period of 120 hrs was optimum for production of hydrogen. pH 7.0±0.4 was optimum for production of hydrogen. L-glutamic acid was a good nitrogen source for production of hydrogen. Glucose and sorbitol were poorer substrates as they induced only limited amount of hydrogen. Anaerobic light induced comparatively more amount of hydrogen in the bacteria under investigation than in anaerobic dark. Thiourea was a poor nitrogen source for the production of hydrogen by Rps. palustris. Results of the above are discussed in the light of existing literature in this communication.