Mosquito control by larvivorous fish.

There is growing of the effects of insecticide used controlling the vectors of human diseases. Manipulating or introducing an auto-reproducing predator into the ecosystem may provide sustained biological control of pest populations. The selection of a biological agent should be based on its self-replicating capacity, preference for the target pest population in the presence of alternate natural prey, adaptability to the introduced environment, and overall interaction with indigenous organisms. In order to achieve an acceptable range of control, a sound knowledge of various attributes of interactions between the pest population and the predator to be introduced is desirable. Biological larviciding for the control of mosquito borne diseases is feasible and effective only when breeding sites are relatively few or are easily identified and treated. Larval control appears to be promising in urban areas, given that the density of humans needing protection is higher than the limited number of breeding sites. Since 1937, fish have been employed for controlling mosquito larvae. Different types of fish have been used so far in this operational technique. However, use of fish of indigenous origin is found to be more appropriate in this operation. This review presents information on different larvivorous fish species and the present status of their use in mosquito control and provides a ready reference for workers involved and interested in mosquito research.

Treatment of microfilaraemics with DEC and its effect on vector infection and infectivity in tribal and non-tribal areas of Bankura district, West Bengal, India.

Single course DEC treatment (6 mg/kg body weight/day for 12 days) was administered to 66 tribal and 442 non-tribal microfilaria (mf) carriers detected through a Filariasis survey in Bankura district, West Bengal, India. All the mf carriers remained amicrofilaraemic on 22nd, 180th and 365th post-treatment day. As a result of DEC treatment to the mf carriers, vector (Culex quinquefasciatus) infection rate in tribal study areas reduced from 2.06% to 1.07%. Infectivity rate was "nil" both before and after treatment. In non-tribal study areas, vector infection rate reduced from 4.33% to 2.22% and infectivity rate from 0.51% to 0.29%.

Computerised tomographic study of tuberculous meningitis in children.

Twenty-one patients with clinical and laboratory diagnosis of tuberculous meningitis were studied at the paediatric department and neuroradiology unit of Bangur Institute of Neurology, both attached to IPGME & R, Kolkata, during the period from 1st February, 1996 to 31 st July, 1996. The age group of the patients were between 1 and 8 years. It clearly appears that CT is an extremely powerful investigative modality for the diagnosis, management and follow-up assessment of development of any complications like hydrocephalus, cerebral infarction, etc. CT examination also can predict the prognosis of the patients.

Oxidative damage of DNA and benzoate by chelated and non-chelated copper in presence of hydrogen peroxide.

Benzoate hydroxylation test revealed that Cu(II) reacting with H2O2 produced OH degree radicals, which nicked or damaged DNA or hydroxylated benzoate, the extent of damage or hydroxylation depending on the period of incubation. The production of OH degree free radicals was also supported by the scavenger studies. Neither Cu(II) nor H2O2 alone could damage DNA or hydroxylate benzoate. EDTA-chelated Cu(II) plus H2O2 could damage DNA or hydroxylate benzoate only in presence of the biological reductant, L-cysteine, the damage increased with the increasing molar ratio of L-cysteine to Cu-EDTA. The biological relevance of the EDTA chelated Cu(II) and H2O2 system is discussed.

Effect of rehydrating fluid 'Electral' on Vibrio cholerae cells.

V. cholerae OGAWA 154 cells underwent rapid loss of colony forming capacity during the first few minutes' incubation in the Electral medium at 37 degrees C, the turbidity of the suspension however increasing with time of incubation and leading to a plateau from 5 min onward. The vibrio suspension in the Electral medium released small amounts of 280 nm and much higher amounts of 260 nm absorbing materials. On withdrawal of the Electral medium, the cells underwent significant liquid holding recovery in the phosphate buffered saline, pH 7. Majority of the cells underwent no significant ultrastructural change but grew into long filamentous forms. The mode of action of the Electral medium on the vibrios is discussed.

Electron microscopic study of phages and aberrant structures produced by induction of prophage kappa in Vibrio cholerae el tor cells.

Prophage kappa in V. cholerae el tor strain SLH22(J) could be induced spontaneously or by treatment with nitrofurantoin, though the efficiency of induction was very low (not more than 0.8%). V. cholerae el tor cells were found to release many different aberrant structures of the temperate phage, kappa. These aberrant structures were characterized by density gradient centrifugation and electron microscopy.

Effects of nitrofurantoin on viability, DNA synthesis and morphology of Vibrio cholerae cells.

Nitrofurantoin caused a dose dependent inhibition of growth and decrease in viability of V. cholerae cells, the 10% (D10) and 37% (D37) survival doses being 50 and 19 micrograms/ml respectively. The drug at a concentration of 60 micrograms/ml caused 86% inhibition of DNA synthesis. Both light and electron microscopic observations revealed that treatment with nitrofurantoin (60 micrograms/ml for 1 hr at 37 degrees C) led to a significant filamentation of the V. cholerae cells, ultrastructure of the cell cytoplasm, plasma membrane and cell wall however remaining unaltered from those of untreated cells. The results are discussed in relation to DNA lesions produced by and the carcinogenic potential of the drug.

Induction of prophage lambda by nitrofurantoin and its modulation by butylated hydroxytoluene, sodium arsenite and alpha tocopherol.

Nitrofurantoin induced prophage-lambda in E. coli K12 strain GY5027(lambda) in a dose dependent manner, the maximum induction being 10-fold the spontaneous induction level and the maximum efficiency of induction 74%. The lever extract used as a metabolizing mixture enhanced the induction level significantly. Chloramphenicol at a concentration of 20 micrograms/ml inhibited the prophage induction by nitrofurantoin, indicating that the induction required concomitant protein synthesis. Butylated hydroxytoluene(BHT) and sodium arsenite enhanced the nitrofurantoin induced prophage-lambda induction in E. coli GY 5027(lambda) cells in a dose dependent manner. The maximum modulations in induction level (I/Io) were achieved with 100 micrograms/ml BHT and 250 micrograms/ml sodium arsenite corresponding to a nitrofurantoin concentration of 15 micrograms/ml and were found significant on statistical analysis. alpha-tocopherol, however, did not produce any effect on the prophage-lambda induction by nitrofurantoin.

Membrane lipid peroxidation by ultrasound: Mechanism and implications.

Ultrasonic radiation produced a dose-dependent linear increase in lipid peroxidation in the liposomes membrane as reflected in the measurement of conjugated dienes, lipid hydroperoxides and malondialdehydes. Ultrasound induced malondialdehyde production could not be inhibited by any significant degree by superoxide dismutase or histidine or dimethyl furan but was very significantly inhibited by butylated hydroxytoluene, cholesterol, sodium benzoate, dimethyl sulphoxide, sodium formate and EDTA. The scavenger studies indicated the functional role of hydroxyl radicals in the initiation of ultrasound induced lipid peroxidation.

An approach towards understanding the genesis of sunlight-induced skin cancer.

The molecular basis of the sunlight-induced skin carcinogenesis has been elucidated. Of the two ultraviolet components of sunlight that reach the earth's surface the UV-B is known to be carcinogenic but the mode of action of UV-A, the predominant component of sunlight, is ill understood. Using the liposomes as a model system, it has been shown here that UV-A causes dose-dependent lipid peroxidation as estimated by measurements of conjugated dienes, lipid hydroperoxides, malondialdehydes and the fluorescent adducts (Schiff bases) produced by the reaction of MDA with glycine. Direct exposure to sunlight has also been shown to cause dose-dependent lipid peroxidation. The UV-A induced lipid peroxidation has also been shown to be dependent on dose rate. While the sodium formate, dimethyl sulphoxide, superoxide dismutase and EDTA do not have any significant effect, sodium azide, histidine, beta-carotene and dimethylfuran were shown to inhibit significantly the UV-A induced lipid peroxidation, thereby providing significant evidence of the involvement of singlet oxygen (1O2) as the initiating agent. The use of D2O in place of H2O as the liposome dispersing medium enhanced to great extent the UV-A induced lipid peroxidation, thereby lending additional support to the finding that singlet oxygen was the initiating agent. The possible mode of formation of 1O2 on exposure to UV-A was discussed. This study also highlighted the role of environmental factors on the sunlight-induced cutaneous damage. Finally, the relation between lipid peroxidation, DNA damage and carcinogenesis has been discussed in a way to suggest the possible link between sunlight exposure and causation of skin cancer.

Observations on human bone-marrow for Leishmania donovani.

During the recent epidemic in North Bihar, a total of 65 cases which were clinically designated as Kala-azar had been subjected to bone-marrow aspiration from the iliac crest, out of which the L.D. body was demonstrated in 55 cases (84.61 per cent). Culture analysis of bone-marrow on modified Tobie's medium, revealed that ten cases (15.39 per cent) which were negative for L.D. body did not show any leptomonads, whereas out of 55 L.D. body positive cases, the promastigote forms developed in 22 cases (40.00 per cent). The probable reasons for the negative findings and also the age and sex distribution in Kala-azar are discussed in brief.