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Biomedical subjects

N Krishnan

Publications and source records attributed to N Krishnan.

At least 19 recordsLinked to original sources
PubMed1989

Lymphokine-activated killer-cell function of lymphocytes from peripheral blood, regional lymph nodes and tumor tissues of patients with oral cancer.

Lymphokine-activated killer (LAK) cells, generated from peripheral blood lymphocytes (PBL) from patients with oral cancer or oral leukoplakia and from healthy donors showed comparable lysis of 6 target tumor cell lines, including 3 derived from head and neck and oral cancers. The tumor burden of the host did not appear to influence the systemic LAK activity. LAK activity of lymphocytes infiltrating the tumor tissues (TIL) was also comparable to that of the PBL. Both TIL and PBL showed a parallel increase in proportion of HNK-I+ and CD-25+ cells upon activation with IL-2. The lymph-node lymphocytes (LNL) from metastatic (met) and non-metastatic (non-met) draining lymph nodes, however, showed reduced LAK activity and an increase in CD8+ cells, in addition to CD25+ and HNK-I+ cells, when cultured with IL-2. When IL-2-activated LNL were co-cultured with autologous PBL during IL-2 activation of the latter, a strong suppressive effect was exerted by LNL. In contrast, IL-2-activated PBL did not suppress autologous LAK generation in spite of an increase in CD8+ cells seen after activation with IL-2. Frequency distribution of LAK precursors was significantly lower in LNL than in PBL from oral cancer patients. LAK precursor frequency in TIL was comparable to that of PBL. The results show that, in oral cancer, regional lymph nodes may not have adequate IL-2-inducible cytotoxic potential, due to a reduced number of LAK progenitors and possible activation of suppressor cells. Alternatively, TIL can be a potential source for LAK cell function.

Adolescent↗
PubMed1989

Natural killer and lymphokine-activated killer cell-mediated cytotoxicity in patients with oral cancer.

Peripheral blood lymphocytes (PBL) from untreated and treated oral cancer patients, lymph node lymphocytes (LNL) from metastatic (met) and nonmetastatic (non-met) lymph nodes, and tumor infiltrating lymphocytes (TIL) were tested for natural killer (NK) and lymphokine activated killer (LAK) cell cytotoxicity using appropriate targets in a short-term chromium release assay. The results showed that while both NK and LAK functions of PBL from oral cancer patients were comparable to those of normal healthy donors, the NK activity of metastatic and nonmetastatic LNL and TIL was highly compromised. On the other hand, potent LAK activity could be generated from all three lymphoid populations. Individual patients showing low NK activity displayed good LAK cytotoxicity, indicating that endogenous cells with low NK potential have adequate ability to respond to interleukin 2 (IL-2). LAK activity tested on autologous tumour targets revealed that TIL were the best source of LAK cells. followed by PBL and LNL.

Cell Line↗
PubMed1989

Lymphocyte subpopulations in Bancroftian filariasis: activated (DR+) CD8+ T cells in patients with chronic lymphatic obstruction.

To examine the relationship between lymphocyte phenotypes and states of activation in patients with Bancroftian filariasis, dual colour flow cytometry and concurrent in vitro cell culture were performed on normal individuals (NV; n = 15), and on patients with either asymptomatic microfilaraemia (MF; n = 12) or elephantiasis (CP; n = 11). In contrast to findings by others in a population with Brugian filariasis, the percentages of total B lymphocytes (CD19), T lymphocytes (CD3), helper/inducer T lymphocytes (CD4), and suppressor/cytotoxic T lymphocytes (CD8) in both patient groups were found to be within the range defined by clinically normal individuals. Furthermore, there were no differences among the groups in the expression of the IL-2 receptor (CD25) on T cells. There was, however, a significantly greater proportion (P less than 0.01) of 'activated' cytotoxic/suppressor lymphocytes (defined by co-expression of CD8 and HLA-DR) in patients with elephantiasis (16.4 +/- 8.6%) than in the MF (8.9 +/- 2.6%) or NV (8.3 +/- 2.9%) groups. Further, when the expression of this activation antigen was examined in parallel with in vitro mitogen responsiveness, an inverse correlation between the percentage of CD8+ HLA-DR+ lymphocytes and pokeweed mitogen-induced proliferation was seen (r = -0.54; P less than 0.001). These data provide further definition of the immunoregulatory abnormalities seen in human filarial infections and suggest that activated CD8+ T lymphocytes may be involved in the pathogenesis of the chronic obstructed lymphatic form of this disease.

Adult↗
PubMed1989

Immunoreactivity of lymphocytes from draining lymph nodes, peripheral blood and tumor infiltrates from oral cancer patients.

Lymphocytes from metastatic (met) and nonmetastatic (non-met) regional lymph nodes, LNL peripheral blood (PBL) and tumor infiltrating lymphocytes (TIL) of patients with squamous cell carcinoma of the oral cavity and healthy donors were investigated for CD3, CD4, CD8 and HNK-1 phenotypes, Natural Killer (NK) cell Activity, Antibody Dependent Cellular Cytotoxicity (ADCC) and proliferative response to mitogen (PHA). Modulation of NK cytotoxicity with recombinant Interferon alpha (IFN-alpha) was also investigated in some cases. Lymphocytes from met and non-met lymph nodes showed no variation in the percentages of CD3+, CD4+ and CD8+ cells, when compared with each other and with PBL of oral cancer patients. TIL showed significantly less proportion of CD3+ and CD4+ cells. The percentage of HNK-1+ cells was significantly lower in LNL and TIL when compared to PBL of oral cancer patients. The mitogen responses of met and non-met LNL were comparable to each other and better than that of PBL from the same patients, while, TIL showed significant impairment in mitogen responses. The NK cytotoxicity and ADCC of PBL from oral cancer patients were comparable to healthy donors which could be augmented by rIFN alpha. LNL and TIL showed almost negligible NK and ADCC activities and NK activity could not be modulated by rIFN alpha. The results thus demonstrate that in oral cancer patients, lymphocytes from three compartments viz. PBL, LNL and TIL showed differential effector functions. The metastatic status of LN did not affect the immunoreactivity of LNL.

Adult↗
PubMed1979

Helical substructure of neurofilaments isolated from Myxicola and squid giant axons.

Neurofilaments purified from invertebrate giant axons have been analyzed with the electron microscope. The neurofilaments have a helical substructure which is most easily observed when the neurofilaments are partially denatured with 0.5 M KCl or 2 M urea. When the ropelike structure comprising the neurofilaments untwists, two strands 4--5.5nm in diameter can be resolved. Upon further denaturation these strands break up into rod-shaped segments and subsequently these segments roll up into amorphous globular structures. Stained, filled densities can be resolved within the strand segments, and these resemble similar structures observed within the intact neurofilaments. The strands appear to consist of protofilaments 2--2.5 nm in diameter. These observations suggest that the neurofilament is a ropelike, helical structure composed of two strands twisted tightly around each other, and they su-port the filamentous rather than the golbular model of intermediate filament structure.

Animals↗
PubMed1979

Identification of the subunit proteins of 10-nm neurofilaments isolated from axoplasm of squid and Myxicola giant axons.

Neurofilaments were isolated from the axoplasm of the giant axons of Myxicola infundibulum and squid. The axoplasm was fractionated by discontinuous sucrose gradient centrifugation and gel filtration on Sepharose 4B. The fractions were monitored for neurofilaments by electron microscopy. When isolated in the presence of chelating agents, the neurofilaments of Myxicola are composed almost entirely of protein subunits with mol wt of 150,000 and 160,000. Squid neurofilaments contain two major proteins with mol wt of 200,000 and 60,000. These proteins are compared with other intermediate filament proteins which have been reported in the literature.

Animals↗
PubMed1978

Characterization of guanylate cyclase of rod outer segments of the bovine retina.

Guanylate cyclase (GTP pyrophosphate-lyse (cyclizing), EC 4.6.1.2.) of bovine retinal rod outer segments is almost completely particulate, i.e. associated with rod outer segment membranes. In contrast to particulate guanylate cyclase in other tissues, treatment of rod outer segments with Triton X-100 does not solublize the enzyme but inhibits it. Enzyme activity is dependent on the presence of divalent cation, especially Mn2+ with only poor activation by Mg2+ (10-fold lower) and no activation seen with other cation. Ezpression of maximal activity required Nm2+ and GTP in equimolar concentrations with an apparent Km of 8 . 10(-4) M and V of 10 nmol/min per mg protein. Excess of Mn2+ over that required for the formation of the Mn . GTP complex was inhibitory. Ca2+, Ba2+ and Co2+ inhibited enzyme activity when assayed with the Mn . GTP substrate complex. In the presence of a fixed concentration of 1mM Mn2+, the enzyme exhibited strong negative cooperative interactions with GTP, characterized by an intermediary plateau region in the substrate vs. enzyme activity curve, a curve of downward concavity in the double reciprocal plot and a Hill coefficient of 0.5. Nucleotides such as ITP, ATP and UTP at higher concentrations (1 mM) stimulates activity by 40%. NaN3 has no effect on the guanylate cyclase. It is thus possible that the guanylate cyclase may be regulated in vivo by both the metal : GTP substrate ratio and the free divalent cation concentration as well as by the ATP concentration and thus play an important but yet undefined role in the visual process.

Animals↗
PubMed1977

The perineural sheath in the urodele amphibian.

The perineural epithelial cells of the peripheral nerve sheath in triturus are elongated flat cells with long and thin cytoplasmic processes. Structural characteristics of the processes include a relative absence of common cytoplasmic organelles of the perinuclear cytoplasm but an abundance of vesicular profiles similar to fully formed pinocytotic vesicles. Unlike pinocytotic vesicles, vesicles of the processes often contain an 8-nm thick filament attached to their cytoplasmic face. Vesicles are also interconnected by similar filaments or by tubules. In addition, almost all vehicles appear to have openings at the cell surface, a feature not seen for pinocytotic vesicles. The concentration of exogenous peroxidase in the vesicles, and the subsequent appearance of peroxidase in the endoneural fluid, myelin sheath and axon, support the notion that the vesicles function in the exchange of substances between extraneural and endoneural fluids.

Animals↗
PubMed1975

A rapid method for the assay of guanylate cyclase.

An extremely rapid and sensitive assay for guanylate cyclase utilizing [alpha-32P]-GTP has been developed. It involves incubation of 5-100 mug of enzyme protein with 1 mM [alpha-32P]-GTP in 40 mM Tris HC1 buffer (pH 7.4) containing 3-3 mM MnSO2, 10 mM theophylline and 1 mM cyclic GMP. The reaction is terminated by addition of EDTA, and [32P]-cyclic GMP formed is isolated by sequential chromatography on Dowex-50-H+ and alumina. Recovery of 75-85% of [3H]-cyclic GMP and a blank of 0.001-0.003% of added [32P]-GTP was routinely obtained. The [32P] radioactivity isolated was shown to be cyclic GMP by a variety of techniques. The assay has also been shown to be applicable for a variety of tissues.

Adrenal Glands↗