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Biomedical subjects

P Misra

Publications and source records attributed to P Misra.

At least 37 records · Page 2Linked to original sources
PubMed1992

Laser mediated release of dye from liposomes.

Liposomes made from phospholipids and containing sulforhodamine dye (1-50 mM) have been irradiated with nanosecond and picosecond laser pulses. Individual liposomes were locally heated by laser absorption of dye dimers during a single laser pulse, and heating was sufficient to release the liposome contents. The extent of dye release produced by a single laser pulse was shown to be quantitatively dependent on several interdependent variables, including dye concentration, liposome size, laser excitation parameters and initial temperature of the dye-liposome system. Fluorescence lifetime data having three components have been obtained and analyzed in terms of three dye environments. Quantitative estimates support a photo-induced thermal mechanism for liposome lysis and release of its contents. These results may be useful for laser induced delivery of therapeutic agents or other applications of lasers in biological systems.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1989

In vitro culture of erythrocytic stages, including gametocytes of Plasmodium berghei (NK 65 strain) using candle jar method and a newly designed continuous medium flow apparatus.

Three methods have been described for cultivation of erythrocytic stages, specially gametocytes of P. berghei NK65 strain, (1) by using vial candle jar where the cultures were subcultured by addition of fresh erythrocytes, (2) a newly designed simple and compact continuous medium flow apparatus, where medium was continuously perfused but fresh erythrocytes were not added and (3) where the subcultures were also done using simple and compact continuous medium flow apparatus for comparison. The maximum percentage of parasitized erythrocytes obtained by these methods was 24.3, 27.1 and 26.4% respectively. Parasites in vials could survive for more than 10 days with 3 to 4 subcultures with maximum 1.96% gametocytaemia. However, the gametocytaemia in continuous medium flow apparatus, where subcultures were not made reached 2.2% compared to that of 2.7% in this apparatus where subcultures were done. The asexual as well as sexual stages of this parasite survived for about 16-18 days in compact continuous medium flow apparatus, where at least 7 subcultures were done.

Animals↗
PubMed1988

Further characterization of the keratinocyte somatomedin-C/insulin-like growth factor I (SM-C/IGF-I) receptor and the biological responsiveness of cultured keratinocytes to SM-C/IGF-I.

Somatomedin-C/insulin-like growth factor I (SM-C/IGF-I) binds to both cultured keratinocytes trypsinized to single-cell suspensions and fresh epidermal sheets derived from 1 M NaBr-treated 6-mm punch biopsies. A gradual increase of 1-4% in specific binding of SM-C/IGF-I to fresh epidermal sheets was observed during a 5-hour incubation period at 15 degrees C. The human keratinocyte SM-C/IGF-I receptor was isolated by polyacrylamide gel electrophoresis after cross-linking with iodinated SM-C/IGF-I and migrated at 135,000 daltons under reducing conditions. Both a partially purified preparation of SM-C/IGF-I, as well as recombinant DNA-derived thr-59-SM-C/IGF-I (25-100 ng/ml), stimulated keratinocyte replication in a serum-free system, with an approximately equivalent effect as insulin (10 micrograms/ml). Since fibroblasts produce SM-C/IGF-I, our data suggest that some dermal-epidermal interactions in diseases such as psoriasis may be mediated, in part, by SM-C/IGF-I.

Cell Division↗
PubMed1988

Differential binding of 125I-IGF-I preparations to human fibroblast monolayers.

Specific, high affinity binding of 125I-IGF-I to the type I IGF receptor on human fibroblast monolayers was not altered by varying feeding schedules, serum lots, washing procedures, or incubation times and temperatures. However, markedly different competitive binding curves were obtained when different iodinated IGF-I preparations were used. Five of six radioligands bound preferentially to the type I IGF receptor on human fibroblast monolayers, with 50% displacement at 4-8 micrograms/l unlabelled IGF-I; with one radioligand a paradoxical 20-200% increase in 125I-IGF-I binding was observed at low concentrations of unlabelled IGF-I, while concentrations as high as 100 micrograms/l IGF-I failed to displace this radioligand. The latter binding pattern cannot be accounted for by 125I-IGF-I binding to the type II IGF receptor. These data indicate that various radioligands may have preferential affinities for different IGF-I binding sites on human fibroblast monolayers.

Autoradiography↗
PubMed1987

Heterogeneity of insulin-like growth factor-I affinity for the insulin-like growth factor-II receptor: comparison of natural, synthetic and recombinant DNA-derived insulin-like growth factor-I.

Although insulin-like growth factors (IGF) I and II bind with high affinity to structurally discrete receptors, they bind with a lesser affinity to each other's receptor. We have evaluated the affinity of five different IGF-I preparations (three natural IGF-I preparations, one synthetic preparation, and one recombinant DNA-derived) for the IGF-II receptor in rat placental membranes, 18-54,SF cells and BRL-3A cells. In all tissues tested, the natural IGF-I preparations demonstrated an affinity for the IGF-II receptor which was 10-20% that of IGF-II. However, the recombinant and synthetic IGF-I preparations exhibited substantially lower affinities than natural IGF-I for this receptor, with only 10-25% reduction in (125-I)iodo IGF-II binding at peptide concentrations up to 400 ng/ml. Radioimmunoassay of the natural IGF-I preparations with an antibody directed against the unique C-peptide region of IGF-II demonstrated that contamination of IGF-I preparations with immunoreactive IGF-II could not exceed 5%. These results demonstrate that IGF-I purified from human plasma has a different affinity for the IGF-II receptor than does synthetic or recombinant IGF-I. Furthermore, these data are consistent with the hypothesis that IGF-I, itself, may be heterogeneous, and that subforms may vary in their affinities for the IGF receptors. Alternatively, IGF-I preparations which have been considered to be pure may be contaminated with small amounts of IGF-II, resulting in overestimation of the affinity of IGF-I for the type II IGF receptor.

Adult↗
PubMed1987

Plasma somatomedin-C levels in psoriasis.

We have measured plasma levels of somatomedin-C, one of the principal mediators of growth hormone action, in 25 patients with plaque-type psoriasis of varying severity and compared these levels with those found in healthy controls. Plasma somatomedin-C levels were not elevated in the psoriatic patients regardless of the severity of their disease, suggesting that in these patients growth hormone secretion is within normal limits.

Adult↗
PubMed1986

Effect of an anti-insulin-like growth factor I receptor antibody on insulin-like growth factor II stimulation of DNA synthesis in human fibroblasts.

To investigate the role of insulin-like growth factor II in the control of DNA synthesis in human fibroblasts, dose-response curves for insulin-like growth factor I and II stimulation of [3H]thymidine incorporation were compared in the absence and presence of alpha IR-3, a highly specific monoclonal antibody directed against the type I insulin-like growth factor receptor. Specific binding of [125I]insulin-like growth factor I to human fibroblast monolayer cultures was inhibited 60-70% in the presence of alpha IR-3. alpha IR-3 had no effect on [125I]insulin-like growth factor II binding to human fibroblasts. However, alpha IR-3 inhibited both insulin-like growth factor I and II stimulated [3H]thymidine incorporation. These data indicate that the type II insulin-like growth factor receptor does not function as a transducer of insulin-like growth factor II's mitogenic effect in human fibroblasts.

Adult↗
PubMed1986

Characterization of insulin-like growth factor-I/somatomedin-C receptors on human keratinocyte monolayers.

A membrane receptor for insulin on cultured human keratinocyte monolayers has recently been reported. It has also been established by previous investigators that the receptors for insulin and the somatomedin peptide, insulin-like growth factor-I/somatomedin-C (IGF-I), have similar oligomeric composition. However, these 2 receptors can be distinguished by their high affinity for their respective peptides. The present study was undertaken to identify and characterize IGF-I receptors on human keratinocytes, using time courses at different temperatures, competitive displacement of [125I]IGF-I by unlabeled IGF-I and insulin, and comparative binding of IGF-I, IGF-II, and insulin. The binding of [125I]IGF-I was time and temperature dependent, achieving steady state after 6 h of incubation at 15 degrees C. Specific binding at 15 degrees C averaged 4.33% for 0.8-1.0 million cells. Competition for binding was observed at IGF-I concentrations as low as 1 ng/ml, with half maximal displacement of [125I]IGF-I at IGF-I concentration of 17 ng/ml. Insulin, on the other hand, was 100-fold less potent than IGF-I in displacing [125I]IGF-I. Scatchard analysis of the competitive binding data revealed a curvilinear plot, with a calculated Kd = 1.4 X 10(-9) mol/liter. When the binding of [125I]IGF-I, -IGF-II, and -insulin was compared in the same experiment, the specific binding of [125I]IGF-I was 3.43% as compared with 5.60% for [125I]insulin and 0.90% for [125I]IGF-II. The finding of specific IGF-I receptors on cultured human keratinocytes suggests a possible role for this mitogenic peptide in epidermal cell proliferation.

Binding, Competitive↗
PubMed1986

Structural and immunological characterization of insulin-like growth factor II binding to IM-9 cells.

The structural and immunological properties of the insulin-like growth factor II (IGF-II) receptor on IM-9 lymphoblasts were studied using a combination of competitive binding and affinity cross-linking techniques as well as with a panel of polyclonal and monoclonal antireceptor antibodies. Unlike IGF-II binding to the classical type II IGF receptor, [125I] IGF-II binding to IM-9 cells was potently inhibited not only by unlabeled IGF-II, but also by insulin (50% inhibition of binding at 2.5 and 1.5 nM, respectively). Affinity cross-linking of [125I] IGF-II to intact cells, followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, demonstrated that the overwhelming majority of IGF-II binding was to a type I receptor (apparent mol wt, greater than 300,000 unreduced and 135,000 reduced), with minimal binding to a type II receptor (apparent mol wt, 220,000 unreduced and 240,000 reduced). After preincubation with five different antireceptor antibodies, inhibition of [125I] IGF-II binding was comparable to inhibition of [125I]insulin binding. These studies demonstrate that in IM-9 cells, the majority of IGF-II binding is to a type I receptor with high affinity for both insulin and IGF-II. Whether this is an atypical insulin receptor or a unique type I receptor remains to be established.

Autoradiography↗
PubMed1980

Weak estrogenic activity of lindane in rats.

Administration of lindane (20 mg/kg . d) for 30 d to ovariectomized rats caused no significant change in the weight of the uterus, cervix, or vagina. Histological changes in these organs were comparable to those in ovariectomized control rats. Treatment with estradiol dipropionate alone and in combination with lindane induced a significant increase in the weights of these organs. Microscopically, these organs appeared normal. Lindane induced a significant increase in the glycogen content of the uterus, cervix, and vagina of ovariectomized rats compared to ovariectomized control rats, whereas a two- to fourfold increase in glycogen was observed in ovariectomized rats treated with estradiol dipropionate or estradiol dipropionate plus lindane. There was a significant increase in total erythrocytes and hemoglobin in ovariectomized rats treated with lindane, estradiol dipropionate, or lindane plus estradiol dipropionate. An increase in neutrophils with a corresponding decrease in lymphocytes was also observed in rats treated with lindane or lindane plus estradiol dipropionate.

Animals↗