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M H Ravindranath

Publications and source records attributed to M H Ravindranath.

At least 37 records · Page 2Linked to original sources
PubMed1991

Role of gangliosides in active immunotherapy with melanoma vaccine.

Among various tumor associated cell surface antigens, gangliosides, the glycosphingolipids that contain sialic acids, offer a variety of epitopes, some of which are preferentially expressed on melanoma cells. These surface components of the bilayered lipid membrane of tumor cells are the targets of active immunotherapy with melanoma vaccine. Purified gangliosides in aqueous solution form micelles and, at high density, form lactones. Their antigenic expression (physical conformation and orientation) on the cell surface is governed by the nature of the sphingosine and the fatty acids they contain. Evidence is accruing to show that the nature of the fatty acid moiety of gangliosides differs in normal and neoplastic cells. Gangliosides per se are not immunogenic and require extrinsic adjuvanticity. Preparation of a melanoma cell vaccine for active immunotherapy requires an understanding of the ganglioside profile of melanoma, the ganglioside-associated heterogeneity of melanoma, and the role of shed melanoma gangliosides in the immunosuppression of cell mediated and humoral immunity. In addition, the role of some of the anti-ganglioside antibodies in the elimination of shed gangliosides, the cytotoxic killing of tumor cells, as well as in the down-regulation of lymphocyte functions must be considered in the formulation of vaccine. Different strategies for augmenting the immunogenicity of melanoma associated gangliosides with melanoma vaccine are evaluated.

Clinical Trials as Topic↗
PubMed1989

An epitope common to gangliosides O-acetyl-GD3 and GD3 recognized by antibodies in melanoma patients after active specific immunotherapy.

GD3 is a major ganglioside of human melanoma and was shown to be an effective target for passive immunotherapy with murine monoclonal antibodies. It was noted earlier that GD3 neither purified nor in melanoma cell vaccine (MCV), could elicit an antibody response in melanoma patients. In this study, we demonstrate that melanoma patients who received MCV had autoantibodies against a derivative of GD3, O-acetylated GD3 (O-AcGD3), a minor ganglioside expressed on human melanoma cells, and that the antibodies cross-reacted with GD3. Thin layer chromatographic immunostaining revealed that all of the sera containing antibodies against O-AcGD3 also reacted to GD3. None of the other sera responded only to GD3, although the MCV contained 7- to 12-fold higher GD3 than O-AcGD3. Furthermore, the antibody activity was completely abolished by absorption with animal erythrocytes expressing either O-acetyl disialogangliosides or GD3, indicating that the antibodies recognize an epitope commonly shared by GD3 and O-AcGD3. The antibodies bound only to the sialyloligosaccharide moiety but not to the ceramide portion of GD3 after endoglycosylceramidase treatment. The antibodies failed to bind to GD3 after neuraminidase treatment. These results indicate that the sialyloligosaccharides of the gangliosides are important components of the epitope. Periodate oxidation abolished reactivity of the antibodies to GD3 but not that to O-AcGD3, revealing that the glycerol side chain of the sialic acids in both GD3s was an important structure of the epitope. The binding of the antibodies to melanoma cell surface gangliosides was confirmed by an absorption with a GD3- and O-AcGD3-positive melanoma cell line. These results in the light of previous reports on the inability of GD3 to elicit immune response in humans suggest that anti-GD3 antibodies found in the melanoma patients were induced by immunization with O-AcGD3 and O-AcGD3 present in the MCV would serve as an antigen source for GD3-targeted active specific immunotherapy of melanoma.

Antibodies↗
PubMed1987

Gangliosides of human melanoma: altered expression in vivo and in vitro.

The ganglioside composition of human melanoma was analyzed in five sets of tumor specimens obtained directly from surgery, from the autologous tissue culture cell lines, and from the autologous cell lines grown in athymic nude mice. Total gangliosides of these 15 melanoma specimens were isolated and purified, and the amount of each component ganglioside was analyzed by thin-layer chromatography and a thin-layer chromatography scanner. The ganglioside composition of the five surgical melanoma specimens clearly exhibited different patterns from each other. Moreover, none of the autologous cultured melanomas possessed the same ganglioside composition as their original biopsied tumors. However, when these melanoma cell lines were transplanted into nude mice, the ganglioside composition was converted back to the same ganglioside pattern as in the original surgical specimens. The results support the view that changes in the ganglioside composition of melanoma during in vitro growth are caused by the culture environment rather than by selection of melanoma cells with a particular genotype. Reestablishment of the original ganglioside patterns after passage in nude mice provides clear evidence that in vivo expression of gangliosides is a conserved and stable function specified by the human melanoma cells.

Animals↗
PubMed1986

Significance of the variation in haemolymph copper-free- and -bound proteins during ageing and time of day in the crab Scylla serrata (Forskal).

During growth or ageing the total quantity of copper-free proteins in haemolymph of S. serrata increases at a higher rate than copper-bound proteins. The copper-free proteins are specifically degraded to meet the energy demand imposed by outburst of nocturnal activity during night hours, while the copper-bound proteins remain unaffected, signifying the importance of Cu-bound proteins in the normal physiology of the animal.

Aging↗
PubMed1985

Purification and characterization of an O-acetylsialic acid-specific lectin from a marine crab Cancer antennarius.

A sialic acid-binding lectin with high specificity for 9-O-acetyl- and 4-O-acetylsialic acids was purified from the hemolymph of the California coastal crab, Cancer antennarius, by affinity chromatography using bovine submaxillary mucin coupled to agarose. The binding specificity of the crab lectin distinguishes it from other known sialic acid-specific lectins from Limulus polyphemus and Limax flavus which show a broader range of specificity for sialic acids. The purified lectin is homogenous on sodium dodecyl sulfate-polyacrylamide electropherograms with a subunit molecular weight of about 36 kDa. The specificity of the lectin for O-acetylsialic acids appears to account for the fact that it agglutinates mouse, rat, rabbit, and horse erythrocytes, which contain O-acetylsialic acids on cell surface glycoconjugates, but not human monkey, sheep, goat, and chicken erythrocytes which contain only NeuAc or N-glycolylneuraminic acid (NeuGc). This conclusion was supported by the potent inhibition of hemagglutination by bovine and equine submaxillary mucins which contain 9(7,8)-O-acetyl- and 4-O-acetylsialic acids, respectively, and also by free 9-O-acetyl-N-acetylneuraminic acid (9-O-Ac-NeuAc) and 4-O-Ac-NeuAc relative to NeuAc and NeuGc. Further support for the role of O-Ac-sialic acids in hemagglutination of erythrocytes was obtained by enzymatic modification of human erythrocytes. Sialidase-treated erythrocytes were resialylated with purified sialyltransferases and various CMP-sialic acid donor substrates to contain NeuAc or NeuGc or 9-O-Ac-NeuAc in the Sia alpha 2,3Gal or Sia alpha 2,6Gal linkages. Cells resialylated to contain NeuAc or NeuGc were not agglutinated, but cells resialylated to contain 9-O-Ac-NeuAc were agglutinated with high titer, comparable to that of mice or horse erythrocytes.

Animals↗
PubMed1984

Crustacean defense strategies. I. Molecular weight dependent clearance of dyes in the mud crab Scylla serrata (Forskal) (Portunidae: Brachyura).

Clearance rates of dyes injected into the hemocoel of the mud crab, Scylla serrata, revealed several patterns of clearance and retention associated with physico-chemical and biological variables. Clearance rates remained constant: 1) when the molar concentrations of the injected dyes were equal, 2) after repeated injections of dyes and 3) after serum opsonization. Rates increased: 1) with higher molecular weight irrespective of charge, 2) at higher dye concentration and 3) at night concomitant with an increase in the hemocyte population. In contrast, clearance rates decreased with increasing crab size. Dye cleared from the hemolymph accumulated in the gills but not in the hepatopancreas, antennary glands nor gut. The retention of dyes in the gills increased with higher molecular weights. Granular hemocytes accumulated in the gill rachis and lamellae of dye treated but not in gills of normal and saline injected crabs. A role for hemocytes in molecular weight and concentration dependent clearance of dyes is suggested. Our findings are important for understanding the molecular basis of recognition in crustaceans.

Animals↗
PubMed1984

Crustacean defense strategies II. Recognition, clearance, accumulation and externalization of soluble foreign proteins by the mud-crab Scylla serrata.

The Defense reactions of Scylla serrata have been investigated by challenging crabs with two metalloproteins, horse radish peroxidase (HRP:M.W. 40,000) and hemoglobin (Hb:64,000). The defense response analyzed include 1) recognition of foreign proteins; 2) clearance from the haemocoel; 3) accumulation in tissues and 4) externalization. Protein clearance was similar to dye clearance in several respects: 1) clearance rate increased with higher a) molecular weight and concentration and b) at night and 2) decreased with crab size. HRP clearance rate was significantly increased after repeated injections of HRP but not saline. Clearance was not enhanced after repeated injections of Hb. About 70% of HRP accumulates in gills within 2 hours after injection, when there were no signs of HRP accumulation in the hepatopancreas. But about the same percent of injected Hb accumulated in both gills and hepatopancreas after 2 hours of injection. When 300 ug HRP declined in gills after 8 hour, similar amounts of HRP accumulated in the hepatopancreas. Moreover when 325 ug of Hb was lost from gills after 4 hours, the hepatopancreas accumulated about 300 ug, suggesting that foreign proteins may undergo antigenic alteration in the gills prior to mobilization to the hepatopancreas. There is no evidence of degradation of proteins in gills. When HRP and Hb level declined in the hepatopancreas, the levels of these proteins increased in gut contents indicating externalization of injected proteins via gut.

Animals↗
PubMed1980

Haemolymph protein concentration of Scylla serrata : assessment of quantitative methods and intra-individual variability.

The suitability of micro-Kjeldahl, biuret and Folin-Ciocalteu methods of protein determination in analysing the haemolymph protein concentration of Scylla serrata was assessed. It was found that biuret method is simple, reliable and the results are consistent. Intra-individual factor as a function of time of day is also responsible for individual variability in the haemolymph protein concentration of the crab.

Animals↗
PubMed1977

The cystacanth of Moniliformis moniliformis (Bremser, 1811) and its relationship with the haemocytes of the intermediate host (Periplaneta americana).

The nature of the capsule of the cystacanth of Moniliformis moniliformis was studied. Fat body, tracheal system, Malpighian tubules and haemocytes of the host are intimately associated with the cystacanth. The capsule of the cystacanth is cellular. The cells encapsulating the middle and late acanthellae are granular haemocytes of the host, whereas those encapsulating the cystacanth are agranular. Degranulation of haemocytes after encapsulation of the cystacanth recalls the common method for encapsulation of parasites of insect haemocytes, but a difference between the two kinds of encapsulation is that the capsule around the cystacanth does not bring about melanization nor destroys the parasite. It is suggested that the surface of the parasite may have inhibitors against enzyme systems causing melanization. Host haemocytes are also found in the capsular fluid. The infiltration of haemocytes into the capsule may be in response to the release of metabolites by the parasites. It is also suggested that the haemocytes may detoxify the parasitic metabolities. Rarely, capsules containing two parasites were observed. In one of the cases, one of the two cystacanths already possessed its own capsule. This finding, together with the cellular nature of the capsule, suggests that the capsule is of host origin.

Acanthocephala↗
PubMed1976

Histochemical characteristics of the egg envelopes of Acanthosentis sp. (Acanthocephala).

The histochemical and phase contrast observations on the embryonic envelopes enclosing the acanthor of Acanthosentis sp. reveal the presence of three layers. All the three layers were non-refractile during early stages of their formation, and become refringent subsequently. The outer layer loses its refractile property together with affinity for acid and basic dyes when the eggs are fully developed. This layer is neither tanned nor chitinous. The second layer consists of glyco-lipo-proteinous matrix. The polysaccharide moiety is identified to be strongly sulfated acid mucopolysaccharide. The lipid component has been characterized to be KOH resistant and esters of unsaturated fatty acid. The protein is rich in aromatic amino acids. The third and the innermost layer contains chitin and acid mucopoly-saccharides. The protein is rich in sulfur-containing amino acids. Sulphydryl groups were present during early stages of its formation, but forms disulphide cross-links subsequently. Stages in the development of acanthors were characterized with reference to the formation of envelopes. The permeability experiments carried out on fresh eggs using 0.1% aqueous solutions of bromophenol blue, methylene blue, toluidine blue, basic fuchsin and neutral red indicate that the inward diffusion of these substances is prevented subsequent to formation of disulphide groups in the innermost layer. The results further indicate that the embryo derives nutritive requirements from the fluid of pseudocoel of the female worm through th envelopes covering it.

Acanthocephala↗
PubMed1975

Histochemical studies of pedicellaria of an echinoid, Salmacis bicolor.

The tridentate pedicellaria of Salmacis bicolor consists of calcareous head and stalk, connected by a muscular neck regions. Head, neck and stalk are covered by a thin cuticle, which is non-mineralized and soft. Both the cuticle and the organic fraction of the calcareous region are resistant to acids and alkalis. Histochemical studies reveal that both the cuticle and the organic matrix of the calcified head and stalk contain protein, polysaccharide and lipids. The lipid content of the organic fraction of the mineralized matrix recalls the spicules of Pluteus larva reported in an earlier study. The protein component of the cuticle and that of the organic matrix slightly differ in that the former is rich in aromatic amino acids, namely tyrosine and tryptophane. Both cuticle protein and the protein of the organic matrix lack sulphur containing aminoacids. Another feature of similarity between the cuticle and the organic matrix is that both contain acid mucopolysaccharide and neutral mucopolysaccharide components. The role of acid mucopolysaccharide in calcification is discussed. The neutral mucopolysaccharide has been suggested to be similar to chitin, and its significance is discussed. Unlike the skeletal elements of other invertebrates, the cuticle and the organic matrix of pedicellariae are devoid of any phenolic compounds.

Amino Acids↗