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Biomedical subjects

K M Rao

Publications and source records attributed to K M Rao.

At least 73 records · Page 4Linked to original sources
PubMed1990

Effects of pentoxifylline administration on blood viscosity and leukocyte cytoskeletal function in patients with intermittent claudication.

We have previously shown that pentoxifylline, a drug used in intermittent claudication, causes depolymerization of actin in leukocytes in vitro. In this study we evaluated several parameters in peripheral blood obtained from 17 patients receiving pentoxifylline, before therapy and at 1 and 2 months after initiation of drug therapy. Total blood viscosity decreased at 1 month and was further reduced at 2 months. The plasma viscosity remained unchanged during the course of the therapy (1.770 +/- 0.147, 1.776 +/- 0.162, and 1.772 +/- 0.164 centipoise at 0, 1, and 2 months, respectively; mean +/- SD, n = 14 to 17). No changes were observed in stimulus-induced actin polymerization in granulocytes, concanavalin A-induced capping in granulocytes and lymphocytes, and anti-IgG-induced caps in lymphocytes, before and after therapy. Similarly, there was no difference in the magnitude of depolymerization caused by pentoxifylline when added in vitro. Thus none of the parameters altered by pentoxifylline treatment in vitro have been observed ex vivo in patients receiving this drug. However, the decrease in total blood viscosity along with unaltered plasma viscosity suggests that the rheology of the cellular elements is being affected by the administered drug. In addition to the direct effects on the cell membrane and the cytoskeleton, pentoxifylline may exert indirect effects through its inhibitory action on cytokine production. Subtle changes in a number of parameters in leukocytes, which taken alone fail to show demonstrable changes, might ultimately be responsible for the therapeutic benefit noted with pentoxifylline.

Actins↗
PubMed1989

Chemotactic peptide receptor-cytoskeletal interactions and functional correlations in differentiated HL-60 cells and human polymorphonuclear leukocytes.

We studied the chemotactic peptide receptor/cytoskeletal interactions in HL-60 cells induced to differentiate with different agents and attempted to correlate these observations with the acquisition of different functional responses. Dibutyryl cyclic AMP-treated cells showed rapid superoxide anion production in response to N-formyl-methionyl-leucyl-phenylalanine (FMLP) and slow, sustained response to phorbol myristate acetate (PMA). Retinoic acid-induced cells showed a slow, sustained response to both FMLP and PMA. Interferon-gamma-treated cells produced no superoxide anion on stimulation with FMLP, whereas tumor necrosis factor (TNF)-treated cells showed a slight response. Chemotactic peptide receptor association was the same in the HL-60 cells treated with different agents, despite marked differences in the superoxide anion generation and actin polymerization responses to FMLP and PMA in these cells. In mature neutrophils chemotactic peptide receptor association with the cytoskeleton was not affected by either pertussis or cholera toxin. However, both toxins inhibited FMLP-induced actin polymerization and superoxide anion generation. This suggested involvement of a G-protein similar to Gt, rather than Gi or Gs. Neither toxin had any effect on PMA-induced superoxide anion generation. These observations indicate that receptor association with the cytoskeleton may not have a significant role in affecting signal recognition and response. Among the several possible roles suggested, clearance of the occupied receptors may be the most important role of the cytoskeletal association. HL-60 cells induced to differentiate with different agents (because of their varied functional responses) might prove very useful in dissecting the molecular mechanisms regulating stimulus-induced activation of neutrophils.

Bucladesine↗
PubMed1989

Study on dermal toxicity and urinary metabolites of the new insect repellent N,N-diethylphenylacetamide in rabbits.

Dermal toxicity of the new multi-insect repellent N,N-diethylphenylacetamide (DEPA) was studied in female rabbits. LD50 of DEPA was estimated to be 3505 mg/kg b.w. On daily topical application for 21 d at a dose of 50 mg/kg b.w., dermal irritancy score and blood chemistry changes indicated that the compound is non-irritant and non-toxic. N-Ethylphenylacetamide and conjugated phenylacetic acid were identified as the urinary metabolites of DEPA by gas-liquid chromatography.

Acetamides↗
PubMed1989

Control of haematophagous flies on equines with permethrin-impregnated eartags.

The efficacy of 10% (w/w) permethrin impregnated eartags for the control of the haematophagous fly pests Stomoxys calcitrans L., Haematopota dissimilis Meigen and Hippobosca maculata Leach on equines in India was determined. The tags were found to be effective for 1-2 months against S. calcitrans and H. dissimilis but completely ineffective against H. maculata. No tags were lost during the study. Tags can be used as part of an integrated control programme. This is the first reported use of eartags for control of haematophagous flies on horses.

Animals↗
PubMed1989

Comparison of indirect and sandwich ELISA for the identification of ECHO viruses.

An indirect enzyme linked immunosorbent assay (ELISA) was standardized for the identification of ECHO viruses isolated in buffalo green monkey (BGM) kidney cell culture on inoculation of 113 sewage samples. Comparable results were obtained with both indirect and sandwich ELISA for the identification of ECHO viruses in respect of 15 out of 34 sewage samples which showed 75-100% CPE in BGM monolayers.

Enterovirus B, Human↗
PubMed1988

Lack of correlation between induction of chemotactic peptide receptors and stimulus-induced actin polymerization in HL-60 cells treated with dibutyryl cyclic adenosine monophosphate or retinoic acid.

We used the promyelocytic leukemic cell line HL-60 to explore the molecular mechanisms regulating stimulus-induced actin polymerization in myeloid cells. HL-60 cells express very few chemotactic peptide receptors in their undifferentiated state and fail to undergo actin polymerization when stimulated with the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (FMLP). However, when the cells were induced to differentiate with dibutyryl cyclic AMP (dbcAMP) or retinoic acid, they acquired the ability to undergo actin polymerization on stimulation with FMLP or phorbol myristate acetate. Kinetic experiments revealed that in the first 48 h of retinoic acid treatment there was no increase in the chemotactic peptide receptors on HL-60 cells, but the cells were capable of undergoing actin polymerization on stimulation with FMLP. Similarly, treatment with dbcAMP showed no increase in chemotactic peptide receptors until 24 h but stimulus-induced actin polymerization was demonstrable as early as 4 h after the treatment. In addition, with dbcAMP-treated cells the magnitude of stimulus-induced actin polymerization showed large variation depending on the duration of exposure to the drug. Dual-label studies using propidium iodide to measure DNA content and NBD-phallacidin to measure the F-actin content revealed that these variations were not related to the stages of cell cycle. Cells in all stages of the cell cycle responded to stimulus-induced actin polymerization, but the magnitude of the response appeared to be more in cells in G2/M phase. The observations reported here indicate that the small number of chemotactic peptide receptors present on HL-60 cells are adequate to mount an actin polymerization response, provided the required intracellular mechanisms exist. Differentiation-inducing agents, therefore, must cause changes within the cell, such as induction of actin-binding proteins, to cause actin polymerization following FMLP stimulation. The HL-60 system serves as a useful model for studying the molecular mechanisms regulating stimulus-induced actin polymerization in human neutrophils.

Actins↗
PubMed1988

Phenylmethylsulfonyl fluoride inhibits chemotactic peptide-induced actin polymerization and oxidative burst activity in human neutrophils by an effect unrelated to its anti-proteinase activity.

Stimulation of polymorphonuclear leukocytes with the chemotactic peptide N-formylmethionylleucylphenylalanine (fMet-Leu-Phe) causes conversion of monomeric actin to polymeric actin. We studied the role of proteinase inhibitors phenylmethylsulfonyl fluoride PMSF) and diisopropyl fluorophosphate in fMet-Leu-Phe-induced actin polymerization in polymorphonuclear leukocytes. Pre-incubation of cells with PMSF (2 mM) for 1 min caused inhibition of fMet-Leu-Phe-induced actin polymerization, as studied by 7-nitrobenz-2-oxa-1,3-diazole (NBD) -phallacidin labeling and flow cytometry. PMSF also inhibited fMet-Leu-Phe-induced hydrogen peroxide release, superoxide anion generation and chemiluminescence. In contrast, diisopropyl fluorophosphate (5 mM) was unable to inhibit fMet-Leu-Phe-induced actin polymerization and superoxide generation, but was effective in inhibiting hydrogen peroxide production and chemiluminescence. PMSF did not cause any change in membrane potential by itself and failed to inhibit the membrane potential changes induced by fMet-Leu-Phe, indicating that PMSF does not affect the binding of fMet-Leu-Phe to the receptors. The high concentration of PMSF required coupled with the fact that diisopropyl fluorophosphate was unable to inhibit fMet-Leu-Phe-induced actin polymerization suggested that this activity of PMSF might be unrelated to proteinase inhibitory activity. Polymyxin B, a membrane-active antibiotic, had an effect similar to PMSF on fMet-Leu-Phe-induced actin polymerization. This suggests that PMSF may also be acting via its membrane effect rather than its anti-proteinase effect.

Actins↗
PubMed1988

Actin depolymerization and inhibition of capping induced by pentoxifylline in human lymphocytes and neutrophils.

Pentoxifylline is used clinically for the treatment of intermittent claudication. It is believed to exert its effect by altering the rheologic properties of blood. The cytoskeleton plays an important role in the maintenance of cell structure and function. In particular, alterations in the state of actin seem to play an important role in cell motility. Therefore, we examined the effect of pentoxifylline on the actin state in human polymorphonuclear leukocytes (PMN) and mononuclear cells. Pentoxifylline (10 mM final concentration) decreased F-actin content in both PMN and mononuclear cells. Pentoxifylline also inhibited concanavalin A-induced capping in PMN and mononuclear cells. Similarly, surface immunoglobulin capping in B lymphocytes was also inhibited. Pretreatment of cells with pertussis toxin did not inhibit pentoxifylline-induced decrease in F-actin, suggesting pentoxifylline does not act through pertussis toxin-sensitive G-proteins. Dibutyryl cyclic AMP failed to show any significant effect on the F-actin content in PMN. Therefore, the effect of pentoxifylline cannot be attributed to changes in cyclic AMP levels. Chemotactic peptide-induced actin polymerization was unaffected in PMN when expressed as percent changes in F-actin. The observations reported here suggest that the rheological effects of pentoxifylline might be due to its effects on the actin state in the cellular elements of the blood. Further studies on the mechanism of action of pentoxifylline on actin state in leukocytes will prove useful in delineating the physiological mechanisms regulating actin state in leukocytes.

Actins↗
PubMed1988

Mutagenicity of methyl isocyanate in the modified test conditions of Ames Salmonella/microsome liquid-preincubation procedure.

Methyl isocyanate (MIC) was tested for mutagenicity using the Ames Salmonella/microsome liquid-preincubation procedure with slight modification of test conditions. In the modification the preincubation mixture was incubated at 10 degrees C for 60 min. MIC was assayed both in the presence and absence of Aroclor-1254-induced S9, using 5 tester strains of Salmonella typhimurium, TA97a, TA98, TA100, TA102 and TA104. MIC induced mutagenic response in two base-pair substitution strains, TA100 and TA104, in the presence and absence of S9. However, mutagenic response in the presence of S9 was low as compared to that in the absence of S9. In the comparative mutagenic activity at 3 different preincubation test conditions (37 degrees C for 20 min, 20 degrees C for 40 min and 10 degrees C for 60 min), optimum mutagenic response was observed at 10 degrees C for the 60-min test condition. However, no mutagenic response was observed at 37 degrees C for the 20-min test condition.

Animals↗
PubMed1988

N,N-diethylphenylacetamide, an insect repellent: absence of mutagenic response in the in vitro Ames test and in vivo mouse micronucleus test.

N,N-diethylphenylacetamide (DEPA), a promising new insect repellent, was tested for mutagenicity in the in vitro Ames Salmonella/microsome mutagenicity test and the in vivo mouse micronucleus test. For the Ames test, DEPA was assayed both in the presence and absence of Aroclor 1254-induced rat-liver S-9 mix (5 and 20% S-9 fraction), using five tester strains of Salmonella typhimurium--TA97a, TA98, TA100, TA102 and TA104. For the micronucleus test, mice were exposed to DEPA through ip injection for 2 and 5 days in separate experiments, and bone marrow and peripheral blood were sampled 6 and 48 hr after the final injection, respectively. DEPA did not induce a mutagenic response in the Ames test, and mouse bone marrow and peripheral blood micronucleus tests. DEPA was not considered cytotoxic, as a depression of the percentage PCE was not observed at any dose in the range of 1 to 100 mg/kg body weight with either treatment protocol of the micronucleus test.

Acetamides↗
PubMed1988

Cytogenetic activity of methyl isocyanate in vivo in the mouse micronucleus test.

The ability of methyl isocyanate (MIC) to induce mutagenic and cytotoxic effects in vivo in the mouse micronucleus test was evaluated by assessing the induction of micronuclei and depression of polychromatic erythrocytes in bone marrow and peripheral blood smears. Animals were exposed to MIC through intraperitoneal injection for 2 and 5 days in separate experiments, and bone marrow and peripheral blood were sampled 6 and 48 h after the last injection, respectively. MIC did not significantly increase the frequencies of micronucleated polychromatic erythrocytes (MN-PCE) and micronucleated normochromatic erythrocytes (MN-NCE) in bone marrow and peripheral blood samples respectively in either twice or multiply treated mice. However, a dose-dependent depression in percentage PCE observed was significant. This indicates that MIC exposure led to the cytotoxic effect by inhibition of bone marrow cell proliferation.

Animals↗
PubMed1988

Cooperative effect of tumor necrosis factor and gamma-interferon on chemotactic peptide receptor expression and stimulus-induced actin polymerization in HL-60 cells.

We studied the effect of tumor necrosis factor (TNF) and gamma interferon (IFN-gamma), alone and in combination, on the expression of chemotactic peptide receptors, stimulus-induced actin polymerization, hydrogen peroxide production (H2O2), and expression of nonspecific esterase (NSE) positivity in human promyelocytic leukemic cell line HL-60. These parameters were analyzed following a five-day culture with the cytokines. Chemotactic peptide receptor expression was studied using the fluoresceinated hexapeptide, formyl-norleucyl-leucyl-phenylalanyl-norleucyl-tyrosyl-lysine and flow cytometry. Actin polymerization, an important event required for chemotaxis and phagocytosis, was studied using NBD-phallacidin labeling, following stimulation with the chemotactic peptide formyl-methionyl-leucyl-phenylalanine (FMLP) or phorbol myristate acetate (PMA). TNF increased the expression of chemotactic peptide receptors in a dose-dependent fashion, and there was good correlation between the receptor expression, stimulus-induced actin polymerization, H2O2 production, and NSE positivity. IFN-gamma was less potent in inducing all the parameters studied but exerted a positive cooperative effect when combined with TNF. IFN-gamma at high concentrations induced chemotactic peptide receptors comparable in magnitude to that seen with TNF but failed to prime these cells to undergo actin polymerization in response to FMLP or PMA. Undifferentiated HL-60 cells showed a decrease in F-actin content on stimulation with PMA. This suggests that protein kinase C might have a negative regulatory role in stimulus-induced actin polymerization. The observations reported here indicate that appropriate combinations of different inducing agents with different modes of action might be necessary to duplicate the functional abilities of mature phagocytic cells.

Actins↗
PubMed1987

Drill biopsy in the diagnosis of lung lesions.

A high speed pneumatic drill was used to perform 190 percutaneous transthoracic biopsies in 161 patients. The resultant cores of tissue provided a definite diagnosis in 146 patients, giving a success rate of 90.7%. Complications occurred in 58 patients, subcutaneous emphysema being the most common, though only seven patients required active treatment, giving a rate of 3.7% for important complications. One patient died within 24 hours of the biopsy procedure owing to asphyxia resulting from aspiration of the contents of an acutely dilated stomach. Our experience clearly establishes that the drill biopsy as used by us is simple and safe and can be carried out in an outpatient department, yielding better overall results than any other procedure for closed biopsy of the lung currently practised.

Adolescent↗