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Biomedical subjects

R K Saxena

Publications and source records attributed to R K Saxena.

At least 73 records · Page 4Linked to original sources
PubMed1994

Effect of moderate & high loadings on the proteoglycans & water content of bovine knee joint articular cartilage.

Variations in proteoglycans and water content of the knee joint cartilage were found to occur when the joint was subjected to articulating motion under moderate and high loadings. It was found that at a moderate load of 150 kg there were an increase in the percentage of proteoglycans but the percentage decreased when the joint was articulated at a high loading of 300 kg. It has also been observed that the ratio of water content and the proteoglycans decreased at moderate load, whereas the ratio increased at high load. The observed changes in proteoglycans and water content in extracellular matrix with moderate and high loadings suggested that articular cartilage properties respond to mechanical stresses.

Animals↗
PubMed1994

Effect of gamma interferon on the expression of class I MHC antigens on fresh leukemic cells and their susceptibility to lysis by lymphokine activated killer cells.

Relationship between MHC class I antigen expression on PBLs from leukemia patients and their susceptibility to lysis by LAK cells was investigated. LAK cells induced small yet significant lysis of leukemic cells. In nine out of 14 cases studied, treatment with Interferon gamma (200 U/ml for 48 hours) resulted in a decrease in the LAK susceptibility of leukemic cells. In six of these cases, there was a concomitant increase in the expression of class I MHC antigen expression. In three samples, the increase in MHC class I antigen expression was not accompanied by a decrease in LAK susceptibility. IFN treatment had no effect on the binding of leukemic cells to LAK effector cells.

Down-Regulation↗
PubMed1993

B-cell mitogenic effect of dinitrophenyl derivative of Mycobacterium tuberculosis antigens.

Soluble antigens derived from the H37Ra strain of Mycobacterium tuberculosis (Ra antigen) induced marginal proliferative response in spleen cells from unsensitized mice. The FDNB derivative of this antigen (Ra-DNP), however, had a marked proliferation-inducing effect. An increase in the population of B-cells but a reduction in the T-cell population was noted in Ra-DNP-treated spleen cell cultures. BSA-DNP derivatives used as control had no effect on mouse spleen cell proliferative activity. Moreover, addition of BSA-DNP along with Ra did not improve the proliferative response to the latter, indicating that in order to obtain proliferative activity, DNP residues must be present on Ra antigens themselves. Thymidine incorporation studies using sorted cell populations indicated that B-cells proliferated in response to Ra-DNP. The effect of Ra-DNP was neither blocked by Polymyxin-B treatment, nor retained by an endotoxin removal column, suggesting that lipopolysaccharide was not responsible for the B-cell mitogenic effect of Ra-DNP. As compared to Ra antigen, Ra-DNP derivative was found to bind more efficiently to B-cells as well as to mouse Ig. Additionally, lymph node cells derived from Ra-sensitized mice proliferated significantly better in response to Ra-DNP. These results indicate that FDNB derivatization of Ra antigen renders it more reactive with B-cells, which may in turn be responsible for a better T-cell reactivity of the derivative, since B-cells can act as antigen-presenting cells. It is possible that DNP residues may facilitate the interaction of Ra antigen with B-cells, perhaps through their Ig receptor.

Animals↗
PubMed1993

MHC class I up-regulation protects some but not all targets against LAK-mediated lysis: possible implications for the existence of LAK cell subpopulations using different recognition strategies.

The effect of gamma-interferon (gamma-IFN) was examined on the lymphokine-activated killer (LAK) cell susceptibility and the levels of major histocompatibility complex (MHC) class I antigen expression on YAC, P815 and EL4 cells. IFN induced a marked increase in the MHC class I antigen expression on all target cells, a concomitant decrease in LAK sensitivity was observed for YAC and P815 cells but not for EL4 cells. In competition experiments, lysis of YAC cells by LAK cells was inhibited by control or IFN-treated YAC and P815 cells, but not by control or IFN-treated EL4 cells. Moreover, lysis of EL4 cells was not inhibited by control or IFN-treated YAC cells. Our results suggest that the effectors killing EL4 are distinct from those killing YAC and/or P815 and that the former are not influenced by the levels of MHC class I antigens on target cells.

Animals↗
PubMed1992

Acid pH-induced changes in the immunoreactivity of specific antigen and antibody in circulating immune complexes from tuberculosis sera.

The effect of acid pH treatment of circulating immune complexes (CIC) derived from tuberculosis sera was studied on the relative titers of specific antibody (CIC Ab) and mycobacterial antigen (CIC Ag) in the complexes. While the specific antibody titers increased, the titers of CIC Ag declined as a result of acid pH treatment of CIC, both changes being highly significant statistically. Direct exposure of TB sera to pH 2.8 also resulted in significant enhancements in the titers of antibodies directed against Mycobacterium tuberculosis (M.tb.). Competition experiments indicated that the acid pH-treated antibodies retained their antigen specificity. TB sera treated with pH 2.8 for 30 min and then neutralized back to pH 7.4 retained the enhanced antibody reactivity even after 7 days of storage at 4 degrees C. Our results indicate that acid pH treatment induces higher antigen binding ability in anti-M.tb. antibodies, present in free or complexed form in TB sera. These changes appear to be irreversible. Dissociation of CIC and analyzing the titers of released antibody and antigen components offered no advantage with respect to the immunodiagnosis of tuberculosis, as compared to the levels of undissociated CIC components or the serum antibody.

Antibodies, Bacterial↗
PubMed1992

Immune status of children suffering from minimal change nephrotic syndrome.

Twenty five children suffering from minimal change nephrotic syndrome were studied for immunological alterations at different stages of this disease i.e., onset, relapse and remission. Changes were found mainly at onset and during relapse in the form of altered helper and suppressor cell ratio, depressed delayed cutaneous hypersensitivity reaction, decreased S-IgG bearing lymphocytes with low serum IgG concentration, and increased S-IgM bearing lymphocytes with high serum IgM concentration. Majority of these parameters returned to normal values during remission. Serum IgE was found high at all stages of this. These alterations suggest defects in cell mediated immunity resulting in secretion of some substance which modifies the glomerular anionic charges.

Adrenal Cortex Hormones↗
PubMed1991

Antigenic epitopes on Mycobacterium tuberculosis recognized by antibodies in tuberculosis and mouse antisera.

The effect of sodium periodate and proteolytic enzyme treatments on the antibody binding capacity of Mycobacterium tuberculosis antigen (Ag) was studied by ELISA. Treatment with sodium periodate resulted in a marked decrease in the capacity of M. tuberculosis Ag to bind antibodies in human TB sera, but had no effect on the reactivity with antibodies in mouse. In contrast, treatment with proteolytic enzymes (trypsin and chymotrypsin) had no effect on the reactivity of M. tuberculosis Ag with human TB sera but reduced substantially the reactivity to antibodies in mouse antisera. These results indicate that anti-M. tuberculosis antibodies in human TB sera react predominantly with carbohydrate determinants and not with protein epitopes sensitive to trypsin and chymotrypsin. The bulk of murine antibodies on the other hand were directed against protein determinants and not the carbohydrate epitopes.

Animals↗
PubMed1991

Analysis of circulating immune complexes (CIC) in tuberculosis: levels of specific antibody and antigens in CIC and relationship with serum antibody.

Eighty sera from tuberculosis (TB) patients, 16 Indian and 10 American control sera were analyzed by ELISA for relative titres of antibody against mycobacterial antigens. Levels of specific antibody and mycobacterial Ag in circulating immune complexes (CIC) isolated from these sera were also studied. All these parameters were found to be elevated in TB sera as compared to control sera. Maximum increase was however noted in CIC specific antibody titres. A good correlation was observed between serum and CIC levels of specific antibody (r = 0.72) and between specific antigen (Ag) and antibody (Ab) levels within CIC (r = 0.64). In a few of the TB sera examined, CIC specific Ab contributed less than 1% to the Ab titres in sera. In order to examine the differences between different subgroups within TB patients, a statistical analysis of variance was performed. Sex of the patients had no effect on any parameter. Sputum-positive patients had significantly higher levels of CIC Ag and Ab than the sputum-negative patients, although no significant difference occurred in respect to serum Ab. All three parameters were significantly higher in patients on chemotherapy as compared to fresh untreated cases. The relevance of these observations to the development of a CIC-based immunodiagnostic assay for TB is discussed.

Analysis of Variance↗
PubMed1991

Morphological changes in the bovine articular cartilage subjected to moderate and high loadings.

This study aims at examining the morphological changes in the cartilage structure of the bovine knee joint when the amputated joints are subjected to (a) a moderate load of 150 kg and (b) a high load of 300 kg and fitted on a knee joint articulating machine at 45 cycles/min for 2 h. The scanning-microscopic study of the surface structure of the experimental and control cartilage shows no appreciable change in the surface morphology of the cartilage when subjected to the moderate load of 150 kg. However, in the case of the high load (300 kg) there is appreciable change in the fibrillary structural pattern of the surface morphology. Histologically too, no appreciable change was noticed when subjected to moderate loadings, but in the case of high loading the cartilage develops roughness of the surface with occasional small clefts.

Animals↗
PubMed1991

Shear properties of articular cartilage of a bovine knee joint subjected to moderate and high loads: an experimental study.

Freshly excised bovine knee joints were subjected to oscillation under constant load on a specially designed knee joint articulating machine with the joints subjected to moderate and high loadings of 1471.5 and 2943 N respectively. Instantaneous and equilibrium shear moduli of the articular cartilage obtained from the experimental knee joints were measured on a mechanical indentor (DuPont 943 TMA) and compared with the corresponding values of the shear moduli of the cartilage obtained from the control knee joints. At moderate load, both the instantaneous and the equilibrium shear moduli exhibit significant increase in their values. However, at high load the constant shear moduli showed a decrease in its value whereas the value of the equilibrium shear modulus was observed to increase slightly.

Animals↗
PubMed1990

Necessity for interaction between adherent and non-adherent rat spleen cells for the generation of a suppressor factor of NK activation.

Whole rat spleen cell populations in culture release constitutively a factor which suppresses the NK activation in response to interleukin-2. Culture supernatants derived from adherent (AD) and non-adherent (NAD) cell preparations obtained from rat spleen cells, did not have a suppressor activity comparable to that present in the culture supernatants of whole spleen cells. When reconstituted mixtures of the AD and NAD cells were cultured, high levels of suppressor activity could again be demonstrated in the culture supernatants, indicating that some kind of co-operation between AD and NAD cells was needed for efficient generation of the suppressor. Non-suppressive culture supernatants derived from NAD cells became suppressive when AD cells were cultured in them. On the other hand, relatively little suppressor activity was generated when NAD cells were cultured in non-suppressive culture supernatants from AD cells. Our results seem to indicate that NAD cells may release some agent which is not itself a suppressor but either (a) induces the generation of suppressor activity from AD cells, or (b) is "processed" into a suppressor agent by AD cells.

Animals↗
PubMed1990

Quantitative estimation of major histocompatibility complex antigens on live tumour cells.

Quantitation of major histocompatibility complex (MHC) antigens on cells can accurately be done by using a flowcytometer. Since flowcytometer is not freely accessable an alternate, simple method for relative quantitation of MHC antigens has been devised. In this procedure, YAC lymphoma cells were first treated with a monoclonal anticlass I MHC antibody and then with a rabbit anti mouse Ig-antibody coupled to peroxidase, followed by colour development using a substrate of peroxidase enzyme. Various assay parameters have been optimized. The validity of the procedure was examined by assessing the enhanced MHC expression on YAC cells treated with a soluble rat spleen derived factor, by the new procedure as well as by the flowcytometer. Comparable results were obtained by using both techniques.

Animals↗
PubMed1989

Lack of optimal activation of natural killer levels by interleukin-2 in rat spleen cells: evidence for suppression.

The effect of human recombinant IL-2 on the levels of natural killer (NK) activity in spleen cells derived from BALB/c mice and different strains of rats was studied. Enhancement of murine NK activity in response to IL-2 was readily demonstrable. Levels of NK activity in control as well as IL-2-treated spleen cells from Wistar, Sprague-Dawley, Fischer, and Long-Evans rats increased initially and peaked on Day 1 or 2 of culture. No significant differences between the control and the IL-2-treated cultures was found in this duration. The subsequent fall in NK activity was slower in IL-2-treated cultures of Fischer and Long-Evans rat spleen cells resulting in a significant difference between the NK levels in control and IL-2-treated cells on Day 5 and Day 7 of the culture. In the case of Wistar and Sprague-Dawley rats, the boosting effect of IL-2 on NK levels was either poor or nonexistent. Even though NK activation was poor, spleen cells of all strains of rats did proliferate in response to IL-2, indicating that the IL-2 preparation used was biologically active on rat spleen cells. Rat spleen cells cultured alone or with IL-2 released a factor(s) in the culture supernatant which could suppress the IL-2-induced NK activation in mouse spleen cells. Indomethacin could block the release of suppressor factor by cultured rat spleen cells. Moreover the NK levels in rat spleen cells could be augmented by IL-2 in the presence of indomethacin. These results indicate that the subdued IL-2-induced NK activation in bulk cultures of rat spleen cells could be due to spontaneous release of prostaglandins by the cultured cells.

Animals↗
PubMed1989

Numerical simulation of systemic O2 and CO2 exchange in a hyperbaric environment.

The process of gas exchange in systemic capillaries and its surrounding tissue is simulated numerically in a hyperbaric environment, taking into account the molecular diffusion, convection, saturation of haemoglobin with O2 and CO2, and the metabolic activity in the tissue. Krogh tissue-cylinder is used as a geometrical representation of the capillary-tissue system. The resulting system of non-linear governing equations together with the physiologically relevant boundary conditions is solved numerically. It is found that the concentration of oxygen decreases from the axis of the capillary to the tissue periphery whereas the concentration of carbon dioxide increases. It is shown that very little CO2 is transported radially. The location of the vulnerable region from the point of view of CO2 accumulation is found to be the rim (r = R2, z = L) situated at the periphery of the tissue near the venous end of the capillary. It is also found that accumulation of O2 decreases whereas that of CO2 increases in a hyperbaric environment. Finally, it is surmised that one of the reasons in causing discomfort among divers could be excessive accumulation of CO2 in the tissue.

Biological Transport↗
PubMed1989

Interleukin-2-induced decrease in the buoyant density of cytotoxic cells and its relationship with proliferation.

Interleukin 2 (IL-2) is known to induce an augmentation of natural killer activity. In the present study we have used discontinuous Percoll density gradients to investigate the changes in the buoyant density of killer effector cells generated in response to IL-2. In all systems examined (mouse and rat spleen cells and human peripheral blood mononuclear cells), the cytolytic effectors generated in response to IL-2 have markedly lower buoyant densities compared to fresh natural killer cells. Our results also suggest that if a single layer of 44.2% (v/v) Percoll is used, almost all IL-2-induced cytolytic activity can be enriched in the cells which float on this layer whereas the heavier cells from the pellet are devoid of cytotoxic activity. The contribution of proliferative activity to (a) the generation of cytotoxicity and (b) the decrease in the buoyant density of the IL-2-induced killer cells was also studied in the mouse system. Natural killer levels in mouse spleen cells treated with mitomycin C could be significantly augmented by IL-2. Moreover, the effector cells generated in control as well as mitomycin-C-treated spleen cells in response to IL-2 had the same low buoyant densities. These results indicate that proliferation is not a prerequisite for the activation of killer activity and a reduction in buoyant density in response to IL-2.

Animals↗
PubMed1989

Clinical profile and electrodiagnostic study of peripheral neuropathy.

A clinical analysis and electrophysiological study was performed in 40 cases of peripheral neuropathy. Motor nerve conduction velocity (MNCV) and electromyography (EMG) were also recorded in 20 healthy volunteers. Twelve cases were of diabetic neuropathy (DN), nine of Guillain-Barre syndrome (GBS), eight of idiopathic, six of leprous, three of toxic neuropathy and one each of acute intermittent porphyria (AIP) and carcinomatous neuropathy. The onset was insidious in a majority of the cases (70%), the presenting symptom being paraesthesia (27.5%). A variable sensory loss was the commonest finding (77.5%). Two patients each had evidence of cranial nerve involvement and affection of urinary bladder and bowel. In both DN and GBS there was a significant reduction in the MNCV especially in the peroneal nerves. In DN 41.6% had evidence of decreased motor unit potentials and 16.6% showed spontaneous fibrillatory activity. For GBS these figures were 77.7% and 8.3% respectively. The peripheral nerve involvement was variable in leprosy and the EMG was normal in all, but one case.

Adult↗
PubMed1989

Modulation of major histocompatibility complex antigens and inhibition of proliferative activity of YAC lymphoma cells by a natural killer lysis resistance-inducing factor (NK-LRIF).

Concanavalin-A-activated rat spleen cells secrete a natural killer lysis resistance-inducing factor (NK-LRIF) distinct from interleukin-2 and interferon, which induces resistance to NK-cell-mediated lysis in YAC tumor cells. In order for NK-LRIF to have an effect on YAC cells, several hours of incubation is required. When NK-LRIF-treated YAC cells are washed and cultured in the absence of NK-LRIF, normal NK susceptibility is regained. YAC cells treated with NK-LRIF show a significant decrease in the rate of proliferation as judged by changes in cell numbers and rate of thymidine incorporation. Cell cycle studies indicate that the proportion of G0/G1 phase cells increases in YAC preparations treated with NK-LRIF. Major histocompatibility complex (MHC) class I antigen expression is markedly enhanced on YAC cells incubated with NK-LRIF but the expression of MHC class II antigens and Thy-1 antigen remains unchanged. No effect of NK-LRIF treatment on the capacity of YAC cells to bind effector spleen cells could be demonstrated.

Animals↗