Characterization of leprosy based on the nasal lipid profile.

While extracting the M. leprae from the nasal flushings of leprosy patients it was found that these organisms were trapped in the waxy layer, between the aqueous and the chloroform layers. Thin layer chromotography (TLC) analysis of this layer, using chloroform-methanol-water system, revealed different spots when sprayed with acid alcohol and heated at 160 degrees C. The TLC profile of lipids of lepromatous and borderline (MB according to the WHO terminology) leprosy patients was distinctly different from that of tuberculoid leprosy patients and normal human volunteers. A simple, economical and fast procedure to characterize patients belonging to different spectra has been developed.

Rearrangements of nitrogen fixation (nif) genes in the heterocystous cyanobacteria.

In the vegetative cells of heterocystous cyanobacteria, such as Anabaena, two Operons harbouring the nitrogen fixation (nif) genes contain two separate intervening DNA elements resulting in the dispersion of genes and impaired gene expression. A 11 kb element disrupts the nifD gene in the nifH, D-K operon. It contains a 11 bp sequence (GGATTACTCCG) directly repeated at its ends and harbours a gene, xisA, which encodes a site-specific recombinase. A large 55 kb element interrupts the fdxN gene in the nifB fdxN-nifS-nifU operon. It contains two 5 bp direct repeats (TATTC) at its ends and accommodates at least one gene, xisF, which encodes another site-specific recombinase. During heterocyst differentiation both the discontinuities are precisely excised by two distinct site-specific recombination events. One of them is brought about by the XisA protein between the 11 bp direct repeats. The second one is caused by the XisF protein and occurs between the 5 bp direct repeats. As a consequence the 11kb and 55 kb elements are removed from the chromosome as circles and functional nif Operons are created. Nitrogenase proteins are then expressed from the rearranged genes in heterocysts and aerobic nitrogen fixation ensues. How these elements intruded the nif genes and how and why are they maintained in heterocystous cyanobacteria are exciting puzzles engaging considerable research effort currently. The unique developmental regulation of these gene rearrangements in heterocystous cyanobacteria is discussed.

Role of alkali cations (K+ and Na+) in cyanobacterial nitrogen fixation and adaptation to salinity and osmotic stress.

Cyanobacteria occupy almost every possible ecological niche on earth, being tolerant to a large number of environmental stresses, including salinity and drought. Many of them also fix atmospheric nitrogen. They are responsible for a significant share of biosolar energy conversions on this planet and make substantial contributions to the carbon and nitrogen status of both oceans and soils. Sodium and potassium are two of the most prevalent cations on this planet. While K+ is an essential macronutrient in most life-forms, Na+ is strongly discriminated by means of highly selective alkali cation transport systems, favouring K+ over Na+. Although a nutritional requirement for K+ has not been specifically investigated, rapid accumulation of K+ during salt/osmotic stress has been observed in several cyanobacteria. Genes and proteins constituting a membrane-bound, turgor- and osmo-inducible, Kdp-ATPase-like system in Anabaena strains that may help in their early K+ responses to salt/osmotic stress have been identified. An unusual, specific and absolute requirement for trace quantities of sodium has been documented in cyanobacteria. Work done in our laboratory, and elsewhere, has elucidated the mechanisms underlying such a unique requirement. It has long been believed that cyanobacteria scavenge and immobilise sodium. We have, however, shown that sodium exclusion brought about by curtailment of influx and active efflux of Na+ forms the basis of salt tolerance in these microbes and that the inherent salt tolerance can be modified by factors that modulate Na+ fluxes in cyanobacteria. Identification of genes affecting the cation relationships in nitrogen-fixing cyanobacteria is currently in progress.

Surgery in patients with congenital coagulation disorders.

BACKGROUND. Surgery is occasionally necessary in patients with congenital coagulation disorders. Major surgery for patients with haemophilia was not being done in India until recently. This paper reports the experience of a single referral centre. METHODS. The data of 52 patients who were operated upon were collected from the hospital records retrospectively between 1984 and 1986 and prospectively thereafter. They included the surgical procedure performed, replacement therapy used and complications encountered. RESULTS. Fifty-nine procedures were performed of which 26 were major, 30 minor and 3 were diagnostic angiograms. Blood components produced in the hospital blood bank were commonly used for replacement and primary haemostasis was achieved in all patients. Delayed bleeding due to inadequate factor levels occurred in 12 procedures and was controlled by increasing the factor replacement. One patient died of suspected acute myocardial ischaemia. CONCLUSION. In India surgical procedures can be safely performed in patients with congenital coagulation disorders.

Effect of venous hypercarbia and hyperventilation on myocardial contractility in canine haemorrhagic shock.

To study the effect of venous hypercarbia on myocardial contractility, haemorrhagic shock was produced in six healthy mongrel dogs by ex-sanguination of 15 ml of blood/kg body weight every 20 minutes till a loss of 45 ml/kg was achieved. After recording haemodynamic and respiratory parameters, the dogs were hyperventilated by positive pressure ventilation for 30 minutes and haemodynamic and blood gas parameters reassessed. During haemorrhagic shock, mean cardiac output decreased from 4.23 l min to 0.98 l min (p < 0.01), stroke index from 2.25 to 0.35 ml/kg (p < 0.05) and left ventricular stroke work index from 3.72 to 0.19 g. m/kg. The mean mixed venous pCO2 increased from 35 mmHg to 56.7 mmHg (p < 0.05). During hypoventilation, mixed venous pCO2 decreased to 40 mmHg (p < 0.05) and without any volume replacement, mean cardiac output increased 2.5 l min (P < 0.05), stroke index to 1.13 ml/kg (p < 0.05) and left ventricular stroke work index, and index of myocardial contractility, increased to 0.78 g.m/kg (p < 0.05). Thus, although hypovolaemia is the major cause of low cardiac output in haemorrhagic shock, this study shows that venous hypercarbia (which probably indicates tissue respiratory acidosis) further worsens circulatory failure by decreasing myocardial contractility. Hyperventilation improves cardiac functions and increases output by relieving tissue hypercarbia in spite of persistent hypovolaemia.

Assessment of transcervical chorion villus aspiration biopsy in early pregnancy.

BACKGROUND. Chorionic villus sampling for prenatal diagnosis is a relatively new technique and variable success rates have been reported by different authors depending on the methods and instruments used. We describe our experience with chorionic villus sampling in Bombay. METHODS. The procedure was attempted on 62 women before termination of their pregnancy via the transcervical route, under constant real-time ultrasound guidance. A metallic cannula was negotiated through the cervix into the uterine cavity to reach the chorionic frondosum and chorionic villi were aspirated by creating a negative pressure in the syringe attached to the cannula. The villus tissue was checked under a dissecting microscope. We calculated the success rate for obtaining a sample depending on the site of the chorionic frondosum, the physique of the mother, the position of the uterus and the size of the cannula. RESULTS. Villus tissue was aspirated in 47 of the 62 cases. The success rates of sampling at the first and second attempts were 48% and 27% respectively. The factors which were associated with a higher success rate were when the chorionic frondosum was situated posteriorly rather than anteriorly (61% v. 48%; p < 0.01), when the patient was thin rather than fat (58% v. 25%; p < 0.001), when the uterus was anteverted rather than retroverted (53% v. 41%). The commonest complication was bleeding which occurred in 15% of patients. CONCLUSION. Transcervical chorionic villus sampling is associated with a high success rate except in fat women with a retroverted uterus and in those with the chorionic frondosum situated in the fundus.

Relation between electrokinetic potentials and growth in callus cultures of Trigonella foenum-graecum.

Callus cultures of Trigonella foenum-graecum were initiated from radicle or cotyledon portions of seedlings and young leaves and maintained on modified 1-B5 medium. The callus mass was disaggregated by mechanical agitation and the discrete cells thus obtained were used to measure their electrokinetic potential. Studies pertaining to the effects of ageing on electrokinetic potential and growth index revealed a relationship between these two parameters. Thus, the rate of change of electrokinotie potential with age could be employed as a parameter to study the growth kinetics of cells in callus cultures.