Genetic structure of Plasmodium falciparum field isolates in eastern and north-eastern India.

BACKGROUND: Molecular techniques have facilitated the studies on genetic diversity of Plasmodium species particularly from field isolates collected directly from patients. The msp-1 and msp-2 are highly polymorphic markers and the large allelic polymorphism has been reported in the block 2 of the msp-1 gene and the central repetitive domain (block3) of the msp-2 gene. Families differing in nucleotide sequences and in number of repetitive sequences (length variation) were used for genotyping purposes. As limited reports are available on the genetic diversity existing among Plasmodium falciparum population of India, this report evaluates the extent of genetic diversity in the field isolates of P. falciparum in eastern and north-eastern regions of India. METHODS: A study was designed to assess the diversity of msp-1 and msp-2 among the field isolates from India using allele specific nested PCR assays and sequence analysis. Field isolates were collected from five sites distributed in three states namely, Assam, West Bengal and Orissa. RESULTS: P. falciparum isolates of the study sites are highly diverse in respect of length as well as sequence motifs with prevalence of all the reported allelic families of msp-1 and msp-2. Prevalence of identical allelic composition as well as high level of sequence identity of alleles suggest a considerable amount of gene flow between the P. falciparum populations of different states. A comparatively higher proportion of multiclonal isolates as well as multiplicity of infection (MOI) was observed among isolates of highly malarious districts Karbi Anglong (Assam) and Sundergarh (Orissa). In all the five sites, R033 family of msp-1 was observed to be monomorphic with an allele size of 150/160 bp. The observed 80-90% sequence identity of Indian isolates with data of other regions suggests that Indian P. falciparum population is a mixture of different strains. CONCLUSION: The present study shows that the field isolates of eastern and north-eastern regions of India are highly diverse in respect of msp-1 (block 2) and msp-2 (central repeat region, block 3). As expected Indian isolates present a picture of diversity closer to southeast Asia, Papua New Guinea and Latin American countries, regions with low to meso-endemicity of malaria in comparison to African regions of hyper- to holo-endemicity.

Evaluation of bifenthrin treated mosquito nets against anopheline and culicine mosquitoes.

BACKGROUND AND OBJECTIVES: The main rural malaria vector Anopheles culicifacies has developed resistance to dichloro diphenyl trichloroethane (DDT), hexachloro cyclo hexane (HCH) and malathion in the state of Haryana in northern India. An alternative synthetic pyrethroid insecticide bifenthrin was therefore evaluated on mosquito nets against anopheline and culicine mosquitoes, in two villages Jagdishpur and Garh Mirakpur of Community Health Center (CHC) Badhkhalsa in district Sonipat, Haryana state. METHODS: Two formulations of bifenthrin, suspension concentrate (SC) and micro-emulsion (ME) were compared with micro-capsule suspension (CS) of lambdacyhalothrin. The impact of three doses of bifenthrin (10, 25 and 50 mg/m(2)) impregnated on mosquito nets was compared with lambdacyhalothrin (25 mg/m(2)) and untreated control. Quality assessment of treatment on treated nets was carried out by residue analysis and the persistence of the insecticide on nets was determined by contact bioassays. Efficacy of treated nets on mosquito density was assessed by calculating mosquito entry rate, immediate mortality, delayed mortality and excito-repellency to the insecticides. RESULTS: In susceptibility tests An. culicifacies was susceptible to bifenthrin (0.1% test papers) and to lambdacyhalothrin (0.05% test papers). Bioassays on treated nets against A. culicifacies recorded 100 per cent mortality up to tenth fortnight for all the doses of impregnation with bifenthrin (SC and ME) and lambdacyhalothrin (CS). Ring-net bioassays against An. culicifacies showed median knock-down time between 3.1 to 11.4 min. Behavioural indices were also studied for anopheline and culicine mosquitoes. The reduction in entry rates of anopheline and culicine mosquitoes into the rooms with treated nets compared to control indicated good efficacy with all the formulations and doses of the insecticides. INTERPRETAION AND CONCLUSION: Indoor (immediate) mortality of mosquitoes with bifenthrin ME formulation was relatively lower compared to SC fomulation of bifenthrin and based on delayed mortility and continued susceptibility in bioassays, bifenthrin ME at the rate of 10 mg/m(2) dose was found suitable for the impregnation of mosquito nets for phase III trial.

Three case reports of the metabolic and electroencephalographic changes during advanced Buddhist meditation techniques.

To examine the extent to which advanced meditative practices might alter body metabolism and the electroencephalogram (EEG), we investigated three Tibetan Buddhist monks living in the Rumtek monastery in Sikkim, India. In a study carried out in February 1988, we found that during the practice of several different meditative practices, resting metabolism (VO2) could be both raised (up to 61%) and lowered (down to 64%). The reduction from rest is the largest ever reported. On the EEG, marked asymmetry in alpha and beta activity between the hemispheres and increased beta activity were present. From these three case reports, we conclude that advanced meditative practices may yield different alterations in metabolism (there are also forms of meditation that increase metabolism) and that the decreases in metabolism can be striking.

Effect of restricted potassium intake on its excretion and on physiological responses during heat stress.

The effect of low potassium (K+) intake on its excretion, concentration in sweat and on physiological responses during heat stress was evaluated on eight Indian male soldiers in winter months at Delhi. After a stabilization period of 3 days on each diet, i.e., 85 mEq of K+/d (diet I, normal), 55 mEq of K+/d (diet II), and 45 mEq of K+/d (diet III), the physiological responses and the sodium and potassium concentrations in sweat, plasma, RBC, and urine were measured when the subjects were exposed to heat for 3 h daily in a climatic chamber maintained at 40 degrees C DB and 32 degrees C WB. The subjects worked in the chamber at the rate of 465 W/h for 20 min periods with 40 min rest between each period of exercise. The whole body sweat was collected after the spell of work and was analysed for sodium and potassium levels. Throughout the study the subjects remained on positive sodium balance except on day 4 in diet III. Fluid balance also remained positive while potassium balance was negative in subjects on diet II and diet III. There was no significant change in heart rate, sweat volume, oral temperature, sodium, and potassium concentrations in plasma and RBC during the entire period of the study. Even in the subjects with negative potassium balance there was no change in the sodium and potassium concentrations in sweat during exercise in heat. The only evidence of potassium conservation was a reduced excretion in urine. Out of the eight subjects, in one subject there was a flattening of the 'T' wave in the ECG and reduction in amplitude of the 'T' wave in two more subjects. As there is no reduction in sweat potassium concentration and the urine volume is low, the marginal level of reduced excretion of potassium in urine with a high rate of sweating (7-81) in subjects doing work in the tropics, there is every likelihood of potassium deficiency if a liberal intake is not ensured. In our earlier studies (Malhotra et al. 1976) we found that the concentration of potassium (K+) in sweat is much higher than in plasma even in acclimatised subjects. A large amount of K+ is therefore likely to be lost in sweat during exposure to heat. In that study there was no evidence of a reduction in K+ concentration in the sweat or urine upon repeated exposure of the subjects to heat, indicative of a compensatory mechanism for conservation of K+ losses. However, these earlier studies were done on subjects who were on a normal diet which contained 75-80 mEq of K+ per day. Since a compensatory mechanism may be triggered only when the body K+ becomes dificient and not earlier, as is the case with sodium (Malhotra et al. 1959), we have now investigated the effects of a sequential reduction of reduced dietary K+ on the dermal and urinary losses of K+. The effects of K+ deficiency on the physiological responses to heat have also been studied. The results of these studies are reported here.

Alterations in aerobic-anaerobic proportions of metabolism during work in heat.

With a view to investigating the aerobic and anaerobic proportions of oxygen supply during different grades of muscular activity in varying thermal stress, studies have been conducted on six young healthy Indians naturally acclimatized to heat. The subjects were given submaximal exercises of 400, 500, and 600 kgm/min (equivalent to 65.40, 81.75, and 98.10 W) for 6 min on a bicycle ergometer in three different simulated conditions, i.e., comfortable, hot humid, and very hot humid. Their O2 consumption (VO2), pulmonary ventilation (VE) and heart rate (HR) were measured during rest and throughout the exercise period (6 min) and for 30 min post exercise. Blood lactate level (LA) was measured during rest and recovery. From these, the total O2 cost with aerobic and anaerobic proportions were calculated. Results indicated a significant increase in the total O2 cost for each exercise with increasing thermal stress, along with a significant increase in the anaerobic fraction and a decrease in the aerobic fraction. The increase in anaerobic contribution to the energy supply processes was further confirmed by a significant increase in relative O2 debt (l/kg) and in blood lactate level at each work load. Thus, a highly significant correlation (P < 0.001) was found between O2 debt contracted and increase in thermal stress. A significant fall in VO2 max was also observed in hot humid and very hot humid conditions as against comfortable temperature, with no change in HR max and VE max.

Lognormal distribution in physical work capacity in young healthy males.

This paper evaluates the statistical distribution of physical work capacity (Vo2 max) in young healthy males. For this purpose, the normally of Vo2 max data, collected on two random samples consisting of 123 and 120 young healthy male volunteers was tested. It is concluded that physical work capacity follows lognormal distribution and the quality of fit has been found to be good as tested by chi2 test.

Cold-induced vasodilatation response at different water bath temperatures in monkeys.

The response of cold-induced vasodilatation (CIVD) at different water bath temperatures was studied in 20 monkeys (3.5 kg) in a conscious state in a thermoneutral room. The animals were controlled by seating in a monkey chair, and the right hind limb up to 7.5 cm from the heel was immersed in a water bath for 60 min. Four series of experiments were conducted at water bath temperatures of 0 degrees, 4 degrees, 8 degrees, and 12 degrees C, respectively, at weekly intervals and the skin temperatures were measured from three sites in the foot. Marked CIVD response was noted from the dorsum and, to a lesser extent, from the sole of the foot, but no response was seen from the tip of the middle toe at 0 degrees, 4 degrees, and 8 degrees C water bath temperatures. The pattern of CIVD response at 4 degrees C was identical to that of 0 degrees C, but the response at 8 degrees C was poor and was absent at 12 degrees C. Three patterns of CIVD--such as hunting, proportional control, and slow, steady, and continuous rewarming--was observed. However, 15% of the animals did not exhibit any CIVD. The observations show that the CIVD response of monkeys is remarkably similar to that of man.

Haematologic changes in rabbits during acclimatisation, deacclimatisation, and reinduction to hypoxia.

Haematologic changes were studied in 16 albino rabbits during acclimatisation, deacclimatisation, and reinduction to hypobaric hypoxia. Of these, four animals died during reinduction. Haemoglobin, haematocrit, and red blood cell count attained maximum values by the 15th day during acclimatisation and by the 10th day during reinduction. Reticulocyte count reached maximum level by the fifth day, both during acclimatisation and reinduction. All these parameters returned to initial control levels by the 10th day of deacclimatisation. The erythrocytes became macrocytic during acclimatisation and remained so during deacclimatisation and reinduction. Blood volume increased on acclimatisation, returned to control values during deacclimatisation, and remained low at this level on reinduction. Red cell mass increased both during acclimatisation and reinduction and returned to control levels on deacclimatisation. Plasma volume did not change on acclimatisation and deacclimatisation, but was reduced on reinduction. The erythrocyte life span and erythrocyte glutamic oxaloacetic transaminase (EGOT) decreased during acclimatisation and reinduction. There was no change in RBC osmotic fragility, indicating no change in the integrity of the red cell wall. The deaths during reinduction were possibly due to haemoconcentration and increased blood viscosity as a result of reduction in plasma volume. It has been concluded that reinduction to hypoxia after a phase of deacclimatisation imposes a more severe stress than experienced during acclimatisation.