The refined X-ray structure of muconate lactonizing enzyme from Pseudomonas putida PRS2000 at 1.85 A resolution.

We report here the refined X-ray crystal structure of muconate lactonizing enzyme (MLE) from Pseudomonas putida PRS2000 at a resolution of 1.85 A with an R-factor of 16.8%. An enzyme from the beta-ketoadipate pathway, MLE catalyses the conversion of cis,cis-muconate to muconolactone. It is a homo-octamer, one monomer consisting of 373 amino acid residues. MLE has two large domains and a C-terminal subdomain: an alpha + beta domain, an alpha beta-barrel domain and a C-terminal meandering subdomain. The alpha beta-barrel domain is highly irregular. Its structure is (beta/alpha)7 beta, with the structural role of the last alpha-helix being replaced by both the C-terminal subdomain and part of the N-terminal domain. The fifth, seventh and eighth barrel strands are unusual because they have left-handed twist about their axes. The strand crossing angles also vary enormously, from +9 degrees to -69 degrees; the first and last strands, which close the barrel, cross at an angle of -69 degrees, making extensive strand-strand hydrogen bonding impossible. The first barrel strand is also unusual because it starts in the N-terminal domain and forms hydrogen bonds to the C-terminal subdomain beta-sheet as well as to its neighbouring strands in the barrel. It thus cements the whole protein together. As in other alpha beta-barrel proteins, the active site of MLE, present in each subunit is at the C-terminal ends of the barrel beta-strands. The active site cleft contains an essential manganese ion, is lined with charged and other polar residues, and contains many of the crystallographic water molecules. The manganese ion is octahedrally co-ordinated to three side-chain carboxylate groups and three water molecules, and is at the centre of a radiating web of ionic and hydrogen-bonding interactions. Additionally, two water molecules are buried in the centre of the barrel and two hydrophilic side-chains (Lys167 and Arg196) make both hydrophobic and hydrophilic packing interactions with much of the barrel interior. The barrel interior is thus also unusual because it is so hydrophilic; the dominating force appears to be the need to solvate the metal ion effectively. This might account for the irregularity of the barrel. The catalytic mechanism has been investigated by docking both substrate and product in the active site with the C-COO- of muconolactone superimposed on the corresponding atoms of cis,cis-muconate. In agreement with earlier kinetic and spectroscopic results, the manganese ion does not interact directly with substrate or product.(ABSTRACT TRUNCATED AT 400 WORDS)

Efficacy of vitamin-C (L-ascorbic acid) in reducing genotoxicity in fish (Oreochromis mossambicus) induced by ethyl methane sulphonate.

The genotoxic effects of ethyl methane sulphonate (EMS) have been assessed in a fish, Oreochromis mossambicus with endpoints including chromosome aberrations, abnormal red blood cell nuclei, abnormal sperm morphology, and protein content (both qualitative and quantitative) of selected tissues, namely, muscle, heart, eye, brain, gill, liver, spleen and kidney. EMS caused chromosomal aberrations, nuclear anomalies in red blood cells, abnormal sperm morphology, and alteration of protein synthesis in various tissues. Some of the EMS toxicity appeared to be modulated and ameliorated in this fish by vitamin-C treatment.

Ameliorating effect of microdoses of a potentized homeopathic drug, Arsenicum Album, on arsenic-induced toxicity in mice.

BACKGROUND: Arsenic in groundwater and its accumulation in plants and animals have assumed a menacing proportion in a large part of West Bengal, India and adjoining areas of Bangladesh. Because of the tremendous magnitude of the problem, there seems to be no way to tackle the problem overnight. Efforts to provide arsenic free water to the millions of people living in these dreaded zones are being made, but are awfully inadequate. In our quest for finding out an easy, safe and affordable means to combat this problem, a homeopathic drug, Arsenicum Album-30, appears to yield promising results in mice. The relative efficacies of two micro doses of this drug, namely, Arsenicum Album-30 and Arsenicum Album-200, in combating arsenic toxicity have been determined in the present study on the basis of some accepted biochemical protocols. METHODS: Mice were divided into different sets of control (both positive and negative) and treated series (As-intoxicated, As-intoxicated plus drug-fed). Alanine amino transferase (ALT) and aspartate amino transferase (AST) activities and reduced glutathione (GSH) level in liver and blood were analyzed in the different series of mice at six different fixation intervals. RESULTS: Both Arsenicum Album-30 and Arsenicum Album-200 ameliorated arsenic-induced toxicity to a considerable extent as compared to various controls. CONCLUSIONS: The results lend further support to our earlier views that microdoses of potentized Arsenicum Album are capable of combating arsenic intoxication in mice, and thus are strong candidates for possible use in human subjects in arsenic contaminated areas under medical supervision.

Assessment of EMS-induced genotoxicity in the Indian climbing perch, Anabas testudineus: cytogenetical vis-à-vis protein endpoints.

Genotoxic effects of EMS have been assessed in fish, A. testudineus, using widely accepted cytogenetic protocols like chromosome aberrations, nuclear anomalies in red blood cells and abnormal sperm head morphology. In addition, gel electrophoretic protein profiles and total protein contents in nine selected tissues were analysed for evaluating their utility as potential indicators of genotoxicity. EMS not only caused chromosomal aberrations in somatic cells, nuclear anomalies in red blood cells, and increased incidence of sperm with abnormal head morphology, but also altered significantly both protein profiles and total protein contents in all tissues tested vis-à-vis suitable controls, indicating relevance of protein data in genotoxicity assessment.

Sorption and transport modeling of hexavalent chromium on soil media.

Chromium-soil adsorption system exhibited both Langmuir and Freundlich isotherm models fit to the sorption data in the studied range of concentration. However the model fit was much better for Freundlich isotherm, this was primarily due to low adsorptive capacity of the soil, 1/n is equal to about 1.08 which is quite close to 1.0, indicating low adsorptive capacity of the soil for chromium(VI) system and the Q(max) was observed very low in range of 0.196-0.220 mg Cr(VI)/g of soil. The initial concentration of Cr(VI) in the solution remarkably influenced the equilibrium Cr(VI) uptake on soil sorption process. The model simulated results for the natural redemption of the soil show the periodic movement of the chromium concentration front ultimately reaching quite low concentration at the end of the cycles. In the case of inorganic chemicals, the absence of chemical decay makes the adsorption phenomena as the major contaminant removal mechanism where as for biodegradation the chemical depletion becomes a major factor in the transport of pollutant. Consequently, the concentration of contaminants reaching the ground water table becomes quite low.

Effect of progesterone (norethindrone) only oral contraceptive on mouse uterus--a SEM study.

Impact of progesterone (norethindrone) only oral contraceptive (MICRONOR) on mouse uterus was investigated by SEM. The three dimensional SEM photographs revealed that, flat wave like mucous folds of the uterus (control) become more thick and highly convoluted after 50 days of MICRONOR feeding. The uteri became highly secretory as indicated by increased thickness of nonciliated secretory cell population with their increased microvilli. Low doses of norethindrone in combination with circulating estrogen, instead of causing regression, maintained a steady and highly secretory state which may interfere implantation/gamete transport.

The role of glucocorticoids on histomorphology, nucleic acid, and protein level of bursa of Fabricius of chicken.

The effect of some glucocorticoids were studied on the bursa of FABRICIUS of chickens. It was found that all 3 steroids caused atrophic changes in the histology of the bursa. These changes were also accompanied by reduction in the DNA, RNA, and total protein contents. The significance of these changes have been discussed.

Pretreatment of indian cane molasses for increased production of citric acid.

Surface culture citric acid fermentation was carried out by Aspergillus niger T55, a strain isolated from its natural source, using cane molasses, either untreated or treated by various methods. Citric acid biosynthesis is seriously impaired by both organic and inorganic inhibitors. A combined treatment of molasses with tricalcium phosphate, hydrochloric acid, and Sephadex fractionation minimizes the level of inorganic and organic inhibitors in molasses and increases the production of citric acid (65% weight yield based on total reducing sugar). The optimum level of individual metal ions for citric acid production depends on the concentration of other metals in the medium.

Appearance of drug-resistant tuberculosis in rural Tennessee.

Drug-resistant tuberculosis (DRTB) is a growing national health concern in both urban populations and rural areas and is exacerbated by the growing epidemic of human immunodeficiency virus (HIV) infection. Between 1989 and 1992, 7 cases of DRTB (5 with multidrug-resistance) were diagnosed in an eight-county region of East Tennessee. During 1990 and 1991 alone, 5 of 100 patients with tuberculosis had drug-resistant strains (5%). All 7 patients with DRTB had 100% resistance to isoniazid; 5 also had resistance to streptomycin, 2 to rifampin, and 1 to pyrazinamide and ethambutol. All patients were white, U.S.-born, and without evidence of HIV infection. Contact investigation revealed that more contacts of patients with DRTB (13 of 74, 18%) were infected than were contacts of patients with drug-sensitive tuberculosis (46 of 290, 16%). Our study demonstrates that DRTB is not confined to geographically distinct areas, but may be a subtle and easily missed diagnosis in presumably low-risk rural populations.