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Biomedical subjects

R Chandrashekar

Publications and source records attributed to R Chandrashekar.

65 records · Page 4Linked to original sources
PubMed1985

Brugia malayi: serum dependent cell-mediated reactions to microfilariae.

Sheathed and exsheathed microfilariae of Brugia malayi are killed by normal rat cells in the presence of immune serum in vitro. Immune serum heated at 56 degrees C for 1 hour lost this activity which was largely restored by the addition of fresh normal rat serum. EDTA but not EGTA abolished this activity indicating the operation of complement by alternate pathway. Fresh normal rat serum alone promoted cellular adherence without exerting cytotoxicity to the microfilariae. The activity in the immune serum could be removed with Staphylococcus aureus cells containing Protein A or anti-IgG antiserum. The activity could also be absorbed to and eluted from Protein A--sepharose CL-4B suggesting the involvement of IgG. Neutrophils and macrophages participate in the antibody dependent cell-mediated cytotoxicity phenomenon. Eosinophils while adhering to the microfilariae exert cytotoxicity only to the exsheathed parasites.

Animals↗
PubMed1984

Separation of viable microfilariae free of blood cells on Percoll gradients.

A consistent and reproducible method is described for isolating pure populations of microfilariae of Litomosoides carinii, Brugia pahangi, B. malayi and Dipetalonema viteae, free of cells, from blood, by density gradient centrifugation on Percoll in 0.25 M sucrose. The recovery of the microfilariae was 85 to 97%.

Animals↗
PubMed1984

Microfilarial periodicity in Mastomys natalensis.

The microfilarial level in the peripheral blood of Mastomys natalensis infected with the filarial parasites, Litomosoides carinii, Brugia pahangi, B. malayi and Dipetalonema viteae was monitored at two-hour intervals for 24 hours. The microfilariae of B. pahangi and B. malayi exhibited nocturnal and diurnal subperiodicity, respectively; no such periodicity was seen in L. carinii and D. viteae infections. The level of B. pahangi and D. viteae microfilariae in peripheral blood was significantly increased when the host was anaesthetized with diethylether or pentothal sodium. Ether-induced anaesthesia had no effect on the level of B. malayi microfilariae but pentothal was most effective. The peripheral blood count of L. carinii microfilariae tended to decrease in the anaesthetized animals but the reduction was not statistically significant.

Anesthetics↗
PubMed1984

The effect of p-aminobenzoic acid and folic acid on the development of infective larvae of Brugia malayi in Aedes aegypti.

Adult Aedes aegypti mosquitoes, infected with the subperiodic Brugia malayi, were found to enhance the development of the filarial parasites to the infective stage when they were exposed to a cotton pad soaked in 10% sucrose solution containing p-aminobenzoic acid (PABA) in 0.001, 0.005, 0.01, 0.05 and 0.1% concentrations. Similarly, larval development increased when the mosquitoes were fed with folic acid at 0.001, 0.01 and 0.1% concentrations. This stimulation was more when PABA or folic acid was given prior to the infected blood meal through the developmental period of the larvae. The data thus suggest that PABA and folic acid are nutrients for the development of B. malayi-microfilariae to the infective stage in A. aegypti.

4-Aminobenzoic Acid↗
PubMed1984

Brugia pahangi: serum-dependent cell-mediated reactions to sheathed and exsheathed microfilariae.

The immune mechanisms operating on the sheath and the cuticle of the Brugia pahangi microfilariae have been studied in vitro. The intact and exsheathed parasites were used for this purpose with serum from albino rats immunized with sonicated homogenates of the parasites as the source of antibodies. The IgG component of the serum was found to promote adherence of rat leucocytes and death of the sheathed and exsheathed parasites in presence of fresh normal serum. EDTA and EGTA abolished the adherence activity suggesting the involvement of complement components via the classical pathway. Both macrophages and neutrophils participate in this reaction. Eosinophils exhibit marginal activity only on exsheathed parasites. The intensity of adherence and killing by neutrophils in the presence of immune serum was greater with the exsheathed microfilariae than with the sheathed ones.

Animals↗
PubMed1984

Effect of diethylcarbamazine on serum-dependent cell-mediated immune reactions to microfilariae in vitro.

The effect of diethylcarbamazine citrate (DEC) on serum-dependent cellular adherence and cytotoxicity to sheathed and exsheathed microfilariae of Litomosoides carinii and Brugia pahangi in vitro has been investigated. DEC at 5 micrograms/ml promoted antibody-mediated neutrophil adherence and cytotoxicity with sheathed L. carinii microfilariae. With exsheathed parasites, the drug promoted significantly complement-and antibody-mediated cellular adherence and cytotoxicity. In the case of B. pahangi, antibody-dependent cell-mediated cytotoxicity (ADCC) of neutrophils to sheathed and exsheathed microfilariae were similarly stimulated by DEC. Pre-incubation of microfilariae with DEC promoted the cellular adherence and cytotoxicity whereas pre-incubation of cells had no such effect. DEC stimulated the adherence of eosinophils to both sheathed and exsheathed microfilariae of the two species but the adherence resulted in cytotoxic effect only on the L. carinii microfilariae. DEC at higher concentrations (100 or 500 micrograms/ml) inhibits these processes. Data on the role of different serum factors involved in this phenomenon have been presented and discussed.

Animals↗
PubMed1983

Comparative efficacy of some benzimidazoles and amoscanate (Go.9333) against experimental filarial infections.

The comparative efficacy of mebendazole, fenbendazole, oxibendazole, oxfendazole, albendazole, flubendazole and micronized amoscanate (particle size 5-8 micron) against Litomosoides carinii and Brugia pahangi infections in Mastomys natalensis was studied on administration of the compounds per os (150 mg/kg/day for 5 days) and subcutaneous (100 mg/kg/day for 5 days) routes. It was found that benzimidazoles when given by the oral route had no effect on adults of L. carinii and B. pahangi. With most of these compounds there was a rise in microfilariae before registering a fall to varying degrees in the peripheral circulation. There was a gradual but effective reduction of microfilariae of L. carinii in animals treated orally with mebendazole (99%), flubendazole (95%) and oxfendazole (85%). No such effect was seen against B. pahangi microfilariae. On subcutaneous administration, all the benzimidazoles with the exception of fenbendazole exhibited marked macrofilaricidal activity against L. carinii. Such activity was not seen with oxibendazole, oxfendazole and fenbendazole against adults of B. pahangi. Amoscanate exhibited superiority over the benzimidazoles in that the compound eliminated microfilariae and adult worms of both L. carinii and B. pahangi species when given by oral and subcutaneous routes.

Aniline Compounds↗
PubMedDate not supplied

Transglutaminase-catalyzed incorporation of host proteins in Brugia malayi microfilariae.

Recently, we have characterized and purified a novel transglutaminase (pTGase) from adults of the filarial worms Brugia malayi. pTGase-catalyzed reactions seem to play an essential role during in utero growth and development of microfilariae. The results presented here demonstrate that exudates from the peritoneal cavity of jirds, the site where adult worms of B. malayi reside and produce microfilariae, contain several host proteins that can serve as substrates in pTGase-catalyzed reactions. The peritoneal exudate proteins are avidly taken up by adult female worms in vitro and incorporated into the developing microfilariae. Among the several host proteins that were crosslinked, a 68-kDa molecular weight protein (p68) was found to be the major protein taken up by the parasites. Following uptake by the parasites, the peritoneal exudate proteins are crosslinked to form high molecular weight aggregates, that are subsequently incorporated into in utero developing embryos and microfilariae. The cross-linking of host proteins was, however, inhibited by monodansylcadaverine (MDC), a competitive inhibitor of pTGase. Antibodies raised against the jird peritoneal exudate proteins strongly immunoreacted with a 68-kDa protein in adult worms and microfilariae extracts but not with infective-stage larvae (L3) of B. malayi. These results suggest that pTGase is involved in covalent incorporation of host proteins (such as p68) into developing embryos and microfilariae of B. malayi.

Animals↗
PubMedDate not supplied

Clearance of Brugia pahangi microfilariae in immunized mice.

Active Brugia pahangi microfilariae (Mf) were injected into naive male BALB/c mice intraperitoneally. Microfilaraemia was studied for 28 days; and Mf circulated in blood in optimum numbers from 3 to 14 days. Anti-Mf response was assessed by the rate of disappearance of Mf from blood as well as their absence from visceral organs. Sonicated antigens of Mf (MfE) and whole worm extract of adults (WWE) induced absolute protection against the establishment of Mf in mice. This potent anti-Mf response elicited by sonicated antigens was intense, rapid and withstood repeated challenge infection. In comparison, immunization with in vitro excretory, secretory and metabolic antigens of Mf (MfESM) produced a partial but significant level of protection. Sera collected periodically from immunized animals showed antibody by micro-ELISA compared to sham-vaccinated controls. When Mf were used as targets along with the peritoneal exudate cells in vitro, sera from mice immunized with MfE and MfESM showed about four-fold cellular adherence to (Mf-ADCA) and 10-fold killing (Mf-ADCC) of Mf which was antibody-dependent. Some degree of correlation was apparent when the antibody levels, Mf-ADCA/Mf-ADCC activity, and Mf clearance were compared. This murine microfilaraemia model was therefore shown to be suitable for studying the host-protective immune response against filarial parasites.

Animals↗