Identification and characterization of mutations in 'X' region of a hepatitis B virus carrier.

A defective form of Hepatitis B virus (HBV) was identified in an apparently healthy voluntary blood donor, who was positive for the presence of HBV by dot blot hybridization, but did not have any serological markers of HBV infection. Two regions, part of X and part of surface antigen genes, were amplified by polymerase chain reaction, cloned and sequenced by Sanger's dideoxy chain termination method. The base sequence analysis revealed that the HBV mutant belonged to ayw serotype and showed three point mutations, in the form of deletions at nucleotides number 1402, 1438 and 1450. Such mutations in the 'X' region, and their likely presence elsewhere, could explain altered antigenic expression.     

Biosurfactant production and use in oil tank clean-up

A proprietary bacterial strain (Pet 1006) produced biosurfactants when grown on both glucose and an immiscible hydrocarbon as carbon sources. Pilot-plant-scale (1500 I) production gave, on repeated batch runs, 2 tonnes of culture broth containing active biosurfactant. The product was used as a substitute for chemical surfactants in a clean-up demonstration test carried out by Cargo Fleet Chemical Company Ltd. (UK) on an oil storage tank belonging to Kuwait Oil Company, Kuwait. The clean-up was successful in removing the sludge from the tank bottom, and it also allowed the recovery of more than 90% of the hydrocarbon trapped in the sludge. The recovered hydrocarbon had excellent properties and could be sold after being blended with fresh crude.I.M. Banat is at 5, Upper Galliagh Road, Londonderry, Northern Ireland BT48 8LW, UK but was at the Kuwait Institute for Scientific Research at the time this paper was written. The remaining authors are with the Kuwait Institute for Scientific Research, Biotechnology Department, P.O. Box 24885, 13109, Safat, Kuwait. I.M. Banat is the corresponding author.In view of the annexation of Kuwait by Iraq in August 1990, this paper has been accepted without return to the author for attention to minor details and for approval of certain editorial changes that have been made. The Editor-in-Chief therefore assumes full responsibility for any errors or omissions.     

Horseradish peroxidase-catalyzed conversion of iodine to iodide in presence of EDTA and H2O2

EDTA (4 mM) blocks the oxidation of iodide to I-3 (increase of extinction at 353 nm) by H2O2 catalyzed by horseradish peroxidase, which is reversed by the addition of an equimolar concentration of Zn2+. Addition of suboptimal concentration of EDTA (2 mM) not only decreases the rate of forward reaction of I-3 formation but also causes loss of extinction of the same when I-3 is generated. The loss of extinction of I-3 is proportional to the enzyme concentration and is blocked by azide, the inhibitor of the peroxidase. EDTA also causes bleaching of nonenzymatically formed I-3 (from iodide and H2O2) only in the presence of horseradish peroxidase, and the effect is reversed by the equimolar concentration of Zn2+. Both the bleaching of I-3 by EDTA and reversal of EDTA effect by Zn2+ are sensitive to azide. The decrease of extinction of I-3 (formed by dissolving iodine in KI solution) is dependent on EDTA, H2O2, and horseradish peroxidase. Molecular iodine is also bleached but at a slower rate than I-3. Evidence is presented to show that this bleaching of I-3 is due to enzymatic conversion of I-3 to iodide in presence of EDTA and H2O2 and this involves pseudocatalatic degradation of H2O2 to O2.     

A Lagrangian Gamma Distribution of the Second Kind

The distribution of the time T for the occurrence of the rth event is derived in a linear function Poisson process, which belongs to a recently introduced family of distributions (JANARDAN and RAO, 1981), called Lagrangian distributions of the second kind (LD₂). In analogy with the ordinary Poisson process, the distribution of the random variable T has been termed the Lagrangian Gamma distribution of the second kind (LG₂); several of its properties and special cases are studied. The frequency function is graphed for some parameter values.     

Redox Biochemistry of Hydrogen Sulfide

H₂S, the most recently discovered gasotransmitter, might in fact be the evolutionary matriarch of this family, being both ancient and highly reduced. Disruption of γ-cystathionase in mice leads to cardiovascular dysfunction and marked hypertension, suggesting a key role for this enzyme in H₂S production in the vasculature. However, patients with inherited deficiency in γ-cystathionase apparently do not present vascular pathology. A mitochondrial pathway disposes sulfide and couples it to oxidative phosphorylation while also exposing cytochrome c oxidase to this metabolic poison. This report focuses on the biochemistry of H₂S biogenesis and clearance, on the molecular mechanisms of its action, and on its varied biological effects.     

Scoring of surface parameters of physiological relevance to surfactant therapy in respiratory distress syndrome.

The Wilhelmy balance was used for in vitro testing of surface parameters of surfactants used for respiratory distress syndrome therapy. Two commercial protein-free surfactants, ALEC and Exosurf, were compared with pure forms of the three main phospholipids in natural surfactants, dipalmitoyl phosphatidylcholine (PC), phosphatidylglycerol (PG), and phosphatidylethanolamine (PE), and their binary mixtures, PC with PE and PG each in the ratio 2:3. Surface excess films (15 A2/molecule) were compressed at 1.2 cycles/min past collapse to a compression ratio of 4:1. The maximum surface pressure, spreading time, compressibility, respreading ratio, recruitment index, and hysteresis area were compared. A consolidated list of criteria for selection of suitable surfactants was compiled from the literature. A relative scoring system was devised for comparison based on these criteria. PC/PG (2:3) performed the best as it fulfilled all the criteria and obtained the highest relative score. Exosurf also performed well, except on the respreading criterion. ALEC and PC/PE were equivalent in their performance and performed well, except on two criteria: hysteresis area and recruitment index. Thus the scoring system proposed here proved valuable to rate the overall efficacy as well as relative merits of surfactant formulations.