Biomedical subjects
Publications and source records attributed to K Prakash.
We used v-rasKi, v-bas, Ras-l, v-mos and v-abl DNA fragments as probes to detect homologous sequences in genomic DNA from a variety of fungi. Cellular homologs were identified in most of them and the number of related fragments detected varied with the probe used. In addition, we found that some onc gene homologs were linked to actin-related sequences.
Clinically diagnosed cases with different grades of rheumatoid arthritis (RA) were studied for (a) cryoglobulin content (b) constituents of cryoglobulins, and (c) rheumatoid factor (RF) titers in sera and cryoglobulins. Of 60 patients, 28 (46.66%) had significantly high levels of cryoglobulins and were mainly distributed in the severe group. Significant amounts of IgG and IgM were found in the cryoglobulins of the 15 cases of RA studied. Ten of these cases had detectable C3 in their cryoglobulins. Of 20 cases of RA, 10 had detectable levels of RF in their cryoglobulins, as shown by the latex agglutination method. There was no significant correlation between the RF titers of cryoglobulins and the RF titers in the corresponding sera or the quantity of IgM and IgG components in them. Since the RF titer in cryoglobulin seemed to indicate the severity of the disease, the use of this parameter is proposed for diagnosis and prognosis of RA.
Blood specimens from patients with rheumatic heart disease in both India and New Mexico were typed for the presence of B cell alloantigen 883 by use of a mouse monoclonal antibody with identical specificity to the original 883 human alloantiserum. Strong relative segregation was recorded for 883 positive B cell typing in patients with rheumatic heart disease in both geographic locations as compared with that in normal unaffected controls. In patients with acute rheumatic fever, studies of actual B-lymphocyte membrane binding by anti-883 monoclonal antibody and sonicated group A streptococcal membrane antigens showed separate but contiguous localization on isolated cell surfaces. Although physically distinct, 883 B cell alloantigen and sonicated group A streptococcal membrane antigens moved together in cell capping studies after incubation at 37 degrees C. These findings reaffirm the apparent close association between 883 B cell alloantigen and rheumatic heart disease. They also demonstrate that the B cell alloantigen 883 itself is physically distinct from but very close to sites on antigen-reactive B cells actually binding to group A streptococcal membrane antigens.
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Supplementary formula feeds inhibited the protective effect of expressed raw and pasteurised human milk in 226 high-risk neonates in a randomised controlled trial. The infection rate in the group given pasteurised human milk and formula (33%) was significantly higher than the rates in the groups given raw human milk (10.5%), pasteurised human milk (14.3%), and raw human milk and formula (16%). This accords with the impressions that some of the association of infection with artificial feeding is partly attributable to the lack of the protective effect of human milk. Heating expressed human milk to 62.5 degrees C for 30 min significantly reduces its protective effect.
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Fresh cardiac valvular tissues and atrial appendages removed from 106 Indian patients with rheumatic heart disease at the time of corrective cardiac surgery were examined to determine the characteristics of valvular interstitial lymphocytic infiltrates using conventional histologic staining along with indirect immunofluorescent techniques. Precise identification of the phenotypic profiles of inflammatory mononuclear cells was attempted using anti-IgG, anti-Ia, and monoclonal mouse hybridoma reagents identifying T cells (OKT3) as well as T cell subsets (OKT4 helper/inducer and OKT8 suppressor/cytotoxic cells). A similar group of 21 patients undergoing cardiac valvular resection in Albuquerque was studied. The mean age of Indian patients providing valve tissues was 27.7, whereas in those in Albuquerque, it was 52 years. Twenty-five percent of rheumatic heart valves in Indian patients showed significant interstitial lymphoid infiltrates, and one third of the rheumatic valves from patients in Albuquerque showed similar mononuclear cell collections. Lymphoid infiltrates contained a predominance of T cells (70 to 80 percent) and only occasional B cells. Most of the T cells were OKT4-positive, with only a minor representation of suppressor/cytotoxic OKT8-positive T cells. In many instances, OKT4-positive helper T cell collections were closely juxtaposed to fibroblasts and collagen fibrils. These findings suggest that the chronic rheumatic scarring process may involve helper/inducer T cells as an ancillary factor in the indolent contracture and fibrosis of deformed cardiac valvular structures. Attempts to demonstrate residual streptococcal antigens by indirect immunofluorescence using a wide panel of heterologous rabbit F(ab')2 reagents with specificity for group A streptococcal membranes, cell wall mucopeptide, or group A carbohydrate gave negative results.
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Sucrase-isomaltase (S-I) and maltase-glucoamylase (M-G) of the brush border have been purified to electrophoretic homogeneity from the pigeon small intestine. Heat-inactivated enzymes of crude homogenates of the pigeon intestinal mucosa, papain-solubilized enzymes and those obtained after chromatographic fractionation behaved in an identical manner. Depending on their sensitivity to heat treatment, the disaccharidases were identified to consist of two maltases; one, the heat-labile maltase, and the other, the heat-stable maltase. Sucrase and isomaltase constituted the thermolabile maltase and could be distinguished from each other. Maltase and glucoamylase formed the thermostable maltase the activities of which however, remained inseparable. Based on these results and in accordance with the nomenclature suggested by Dahlqvist & Telenius (1969), the pigeon intestinal disaccharidases were classified as follows: Maltase Ia = isomaltase, Maltase Ib = sucrase, and Maltase II = glucoamylase. DEAE-Cellulose chromatography did not resolve the two enzyme complexes but gel filtration of the active fractions recovered from the former step, resulted in their separation into two distinct peaks. Sucrase, isomaltase and a part of the maltase activity were recovered in the first peak which eluted close to the void volume. Glucoamylase and the remaining maltase activity were recovered in the second peak which appeared to have been retarded on the column because they were eluted much more slowly. The S-I and M-G complexes have an apparent molecular weight of 195 kd and 209 kd as determined by their gel-filtration pattern on Sepharose 6B. S-I hydrolysed alpha-glucosides such as maltose, sucrose and palatinose with a Km of 3.12 mM, 8 mM and 8.36 mM respectively and did not attack starch or dextran. In contrast, M-G catalysed the hydrolysis of starch, amylose and maltose with a Km of 3.12 mM, 7.59 mM and 3.52 mM respectively, and had no action on sucrose or palatinose. Both S-I and M-G were glycoproteins, and were inhibited by Ag+, Hg2+ and Tris but not by p-hydroxymercuribenzoate, iodoacetamide or imidazole. Na+ on the other hand activated both the enzyme complexes by about 20-25%. It is suggested that the molecular and catalytic properties of intestinal disaccharidases of pigeons do not differ considerably from those of Mammals.
Antisera against purified pigeon small intestinal sucrase-isomaltase (S-I) and maltase-glucoamylase (M-G) were prepared from rabbits. Both sera showed cross-reactivity. It was demonstrated that the sucrase . isomaltase was purified to homogeneity, supporting our earlier results of SDS-PAGE of pigeon intestinal disaccharidases. Both the sucrase- isomaltase and maltase-glucoamylase activities were not inhibited by either specific or cross-reacting antibodies even when a several fold of either antibody was present. It is inferred from these immunochemical results that the two complexes in the pigeon intestine share many structural identities, and that their catalytic site(s) may not be involved in their antigenic domains.