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Biomedical subjects

R K Kumar

Publications and source records attributed to R K Kumar.

At least 55 records · Page 3Linked to original sources
PubMed1999

Culture and characterisation of epithelial cells from human pterygia.

BACKGROUND/AIMS: Pterygia are a common disorder of the ocular surface. The disease represents a chronic fibrovascular and degenerative process thought to originate at the conjunctival-corneal junction, where altered limbal stem cells are proposed to be the cell of origin. Extensive epidemiological evidence exists to implicate ultraviolet B irradiation in the pathogenesis of pterygia. To date no animal or in vitro culture model has been developed to test such an hypothesis. The aim of this study was to establish and characterise a pure population of epithelial cells derived from pterygium tissue. METHODS: Tissue specimens were obtained from patients undergoing pterygium excision. Explants were cultured in either serum free or serum supplemented medium. Primary and passaged cells were processed for light microscopy, analysed by flow cytometry, and characterised immunohistochemically using specific antibodies. RESULTS: In serum free culture, cuboidal cells with typical morphology of epithelial cells migrated from the pterygium explants from 3 days onwards and eventually formed a cohesive monolayer. Passaged cells consisted of 98.4% cytokeratin positive cells and demonstrated immunoreactivity for multiple cytokeratins, including AE1, AE3, AE5, but were negative for AE8. These cells also expressed an epithelial specific antigen, together with vimentin and mucin, as did epithelial cells in sections of pterygia. CONCLUSIONS: A relatively simple method of isolating pterygium epithelial cells has been established. Cultured pterygium epithelial cells are phenotypically and functionally similar to their in vivo counterparts with respect to keratin, vimentin, and mucin expression. In vitro assays using these cells may aid in elucidating the pathogenesis of pterygia.

Cells, Cultured↗
PubMed1999

Improved double immunofluorescence for confocal laser scanning microscopy.

Reliable double immunofluorescence labeling for confocal laser scanning microscopy requires good separation of the signals generated by the fluorochromes. We have successfully overcome the limitation of a single argon ion laser in achieving effective excitation of dyes with well-separated emission spectra by employing the novel sulfonated rhodamine fluorochromes designated Alexa 488 and Alexa 568. The more abundant antigen was visualized using the red-emitting Alexa 568, with amplification of the signal by a biotinylated bridging antibody and labeled streptavidin. This was combined with the green-emitting Alexa 488, which yielded brighter images than fluorescein but exhibited comparable photodegradation. With appropriate controls to ensure the absence of crosstalk between fluorescence channels, these dyes permitted unequivocal demonstration of co-localization. This combination of fluorochromes may also offer advantages for users of instruments equipped with alternative laser systems.

Collagen↗
PubMed1999

Neonatal jaundice. An update for family physicians.

BACKGROUND: Neonatal jaundice is the most common problem encountered in newborns. Fifty per cent of term and 80% of preterm babies are jaundiced within the first week. OBJECTIVE: This paper examines the causes of jaundice and describes the effective management of this common condition. DISCUSSION: Neonatal jaundice could well be an emergency and could lead to disasters, if not identified in time. It is the most common cause for admission in the first week of life, especially since the development of the early discharge program.

Family Practice↗
PubMed1999

Papilloedema secondary to acute purulent sinusitis.

Upper respiratory tract infections and sinusitis are common, but intracranial complications of sinusitis are rare in children and are often clinically unremarkable. Papilloedema secondary to purulent sinusitis is a complication previously not reported. We report two cases to highlight atypical manifestations of sinusitis in children.

Abscess↗
PubMed1998

Cooperative interaction of autocrine and paracrine mitogens for airway epithelial cells.

Mitogens of the EGF family may play an important role in regulating the proliferation of airway epithelial cells (AEC). We examined the production of autocrine mitogenic activity by mouse AEC cultured from explants of tracheal tissue. DNA synthesis by growth-arrested AEC was stimulated by conditioned media from cells maintained in serum-free culture without exogenous growth factors. The mitogenic activity was blocked by a specific inhibitor of the EGF receptor tyrosine kinase. Furthermore, conditioned media from AEC contained molecular species that could compete with radiolabeled EGF in a receptor binding assay. However, mitogenic activity was not blocked by neutralizing antibodies to EGF or to transforming growth factor-alpha, but was partly inhibited by co-incubation with heparin, suggesting that it might be due to a heparin-binding member of the EGF family. The activity was potentiated by co-incubation with IGF-1, analogous to the potentiation by IGF-1 of the mitogenic activity of EGF for AEC. Moreover, the autocrine mitogen produced by AEC exhibited cooperative interaction with the mitogenic activity in conditioned media from growth factor-deprived mouse lung fibroblasts, consistent with the hypothesis that interactions with mesenchymal cells could influence the proliferation of AEC in vivo.

Animals↗
PubMed1998

Immunodetection of the murine chemotactic protein CP-10 in bleomycin-induced pulmonary injury.

The murine S-100 protein designated CP-10 is a potent chemotactic factor for phagocytic cells, exhibiting optimal activity in the picomolar range. We assessed the role of this cytokine in the inflammatory response to pulmonary injury following intratracheal administration of bleomycin to mice. In the lungs of normal animals, strong cytoplasmic immunostaining for CP-10 was demonstrable in all recognisable neutrophil leucocytes sequestered within alveolar capillaries. Following induction of pulmonary inflammation in susceptible C57BL/6 mice, numerous CP-10-positive neutrophils were observed, but many of the recruited neutrophils did not exhibit staining for CP-10. No other cells were immunoreactive. The concentration of CP-10 in bronchoalveolar lavage (BAL) fluids from normal mice and mice administered intratracheal saline was below the level of detection by enzyme immunoassay. In contrast, nanomolar levels of CP-10 were detected in unconcentrated BAL fluids from C57BL/6 mice after bleomycin-induced injury, and the presence of monomeric CP-10 was demonstrable by Western blotting. Elevation of CP-10 levels correlated with the influx of inflammatory cells in C57BL/6 mice, but was not demonstrable in BAL fluids from BALB/c mice, which are resistant to pulmonary injury by bleomycin. We conclude that CP-10 may contribute to the recruitment of inflammatory cells in bleomycin-induced lung damage.

Animals↗
PubMed1998

An improved murine model of asthma: selective airway inflammation, epithelial lesions and increased methacholine responsiveness following chronic exposure to aerosolised allergen.

BACKGROUND: Existing murine models of asthma lack many of the inflammatory and epithelial changes that are typical of the human disease. Moreover, these models are frequently complicated by allergic alveolitis. METHODS: High IgE responder BALB/c mice were systemically sensitised to ovalbumin and chronically challenged with low particle mass concentrations of aerosolised ovalbumin. Titres of antiovalbumin IgE in serum were measured at two weekly intervals by enzyme immunoassay, accumulation of inflammatory cells and histopathological abnormalities of the epithelium were quantified morphometrically in the trachea and the lungs, and airway reactivity was assessed by measuring bronchoconstriction following intravenous administration of methacholine. RESULTS: Mice sensitised by two intraperitoneal injections of ovalbumin developed high titres of IgE antibodies to ovalbumin. Following exposure to low concentrations of aerosolised antigen for up to eight weeks these animals developed a progressive inflammatory response in the airways, characterised by the presence of intraepithelial eosinophils and by infiltration of the lamina propria with lymphoid/mononuclear cells, without associated alveolitis. Goblet cell hyperplasia/metaplasia was induced in the intrapulmonary airways, while epithelial thickening and subepithelial fibrosis were evident following chronic exposure. In parallel, the mice developed increased sensitivity to induction of bronchospasm, as well as increased maximal reactivity. Non-immunised mice exposed to aerosolised ovalbumin had low or absent antiovalbumin IgE and did not exhibit inflammatory or epithelial changes, but developed airway hyperreactivity. CONCLUSIONS: This experimental model replicates many of the features of human asthma and should facilitate studies of pathogenetic mechanisms and of potential therapeutic agents.

Aerosols↗
PubMed1998

Injury to murine airway epithelial cells by pollen enzymes.

BACKGROUND: Pollens are important triggers for asthma but the mechanism of sensitisation to their proteins remains poorly understood. The intrinsic protease activity of some allergens may contribute to sensitisation by disrupting the integrity of the airway epithelial barrier. Pollens release a variety of enzymes, including proteases, upon hydration. The hypothesis that such enzymes might be able to damage airway epithelial cells was therefore tested. METHODS: Diffusates from pollens of Lolium perenne (ryegrass), Poa pratensis (Kentucky bluegrass), Acacia longifolia (Sydney golden wattle), or Casuarina distyla (she-oak) were incubated with mouse tracheal epithelial cells in culture and cellular detachment was quantified using a methylene blue dye binding assay. RESULTS: Diffusates prepared using 100 mg/ml of pollen caused detachment of 30-90% of airway epithelial cells in separate experiments. Within each experiment comparable detachment was observed with all diffusates tested, although total protein in the diffusates varied markedly between species. Viability of the cells recovered after exposure to Acacia diffusate was higher than after detachment by exposure to Lolium diffusate. Cellular detachment by all of the diffusates could be almost completely inhibited by addition of 10% serum. Aprotinin, an inhibitor of serine proteases, partially blocked activity in diffusates of Lolium pollen but not of Acacia pollen. In contrast, alpha 1-protease inhibitor and secretory leucocyte protease inhibitor (SLPI) were not able to block the activity of either diffusate at concentrations which inhibited cellular detachment by trypsin. CONCLUSIONS: Proteases released by pollens are able to cause detachment of airway epithelial cells from their substratum in vitro and may not be effectively inhibited by endogenous antiproteases.

Acacia↗
PubMed1998

Pyloric stenosis in premature infants.

Congenital hypertrophic pyloric stenosis is widely believed to be uncommon in premature infants, and is known to present after the corrected age for a 'term baby'. This cautionary tale highlights the fact that this condition can occur in a premature infant (and may present) in an atypical way well before the infant becomes a 'term baby'.

Humans↗
PubMed1998

Acute epiglottis.

Explore the source record for details and available documents.

Acute Disease↗
PubMed1997

Synthesis and studies on the effect of 2-thiouridine and 4-thiouridine on sugar conformation and RNA duplex stability.

In order to understand the effect of 2-thiouridine (s2U) substitution on RNA structure and the potential for stabilization of tRNA codon-anticodon interactions through s2U-34 modification, a pentamer RNA sequence, Gs2UUUC, was synthesized and characterized by NMR spectroscopy. The single strand contains the UUU anticodon sequence of tRNALys with flanking GCs to increase duplex stability. Regiochemical effects of uridine thiolation were determined by comparing the structure and stability of the 2-thiouridine containing oligonucleotide with an identical sequence containing 4-thiouridine (s4U) and also the normal uridine nucleoside. Circular dichroism spectrum indicated an A-form helical conformation for Gs2UUUC which was further confirmed by 2D ROESY NMR experiments. The duplex stability of the three pentamers complexed with a 2'-O-methyl-ribonucleotide complementary strand, GmAmAmAmCm, was determined by UV thermal melting studies and by 1H NMR spectroscopy. The duplex containing s2U has a T m of 30.7 degrees C compared to 19. 0 degrees C for the unmodified control and 14.5 degrees C for the s4U containing duplex. The results from UV experiments were corroborated by imino proton NMR studies that show proton exchange rates, chemical shift differences, and NH proton linewidths indicative of the stability order s2U >U >s4U. The magnitude of the effect of s2U in our model system is comparable to the 20 degrees C stabilization observed by Grosjean and co-workers for 2-thiolation in a codon-anticodon model system composed of two tRNAs with complementary anticodon sequences [Houssier, C., Degee, P., Nicoghosian, K. and Grosjean, H. (1988) J. Biomol. Struct. Dyn., 5, 1259-1266].

Anticodon↗
PubMed1997

Predictors of arterial thrombosis after diagnostic cardiac catheterization in infants and children randomized to two heparin dosages.

Arterial thrombosis is the most frequent major complication of percutaneous arterial catheterization in children. We prospectively studied the effect of randomized dosage of heparin, 50 IU/kg-group I and 100 IU/kg-group II, on the incidence of arterial thrombosis in 366 children and analysed the various factors which may influence the occurrence of this complication. The age of patients ranged from 17 d to 11 yr (mean age 39.5 +/- 40.9 mo) and mean weight was 11.2 +/- 7.8 kg (range 3 to 39 kg). The incidence of arterial thrombosis was 9.8% in group I and 9.3% in group II (P = NS). There was no statistical difference in precatheterization and procedure variables in the two groups and also in the group with absent pulse (n = 35) to the group with pulse present post cath (n = 331). There were 24.9% infants in our study and 14.3% of these had arterial thrombosis. The loss of pulse was more often seen with more number of attempts at arterial puncture (P < 0.001), absence of back bleed at the end of the procedure (P < 0.001), and increased duration of catheterization (P < 0.01). Use of larger sheath size in a given weight and body surface area of children increased incidence of arterial thrombosis. The administration of heparin 50 IU/kg was equally efficacious to heparin 100 IU/kg. Of the patients with arterial thrombosis, 23 responded with intravenous heparin and 12 needed streptokinase. There was no bleeding or haematoma. Thus our study shows that less attempt for arterial puncture, use of smaller sheath size, maintaining shortest procedure time and ensuring back bleed minimises incidence of arterial thrombosis post catheterization.

Anticoagulants↗
PubMed1997

Prolonged low-dose indomethacin therapy for patent ductus arteriosus in very low birthweight infants.

OBJECTIVE: To determine the efficacy and side-effects of prolonged low-dose indomethacin therapy in very low birthweight (VLBW; < 1500 g) infants with a haemodynamically significant patent ductus arteriosus (hsPDA). METHODOLOGY: Very low birthweight infants admitted over a 16 month period were studied (8 months, retrospectively and 10 months, prospectively). Cross-sectional and M-Mode echocardiograms with pulsed-wave and colour Doppler were performed to assess the significance of ductal patency. RESULTS: Forty-one (28%) of 148 VLBW infants were diagnosed to have hsPDA. Indomethacin therapy was successful in 90% after the first course, increasing to 95% after the second course. The recurrence rate after the first course was 3%. Minor and transient complications included oliguria, urea retention, hyponatraemia and thrombocytopenia. Although three infants had focal bowel perforation and the fourth had bowel perforation associated with necrotizing enterocolitis, the incidence of gastrointenstinal pathology was not significantly different from infants without hsPDA and not given indomethacin. CONCLUSIONS: Very low birthweight infants with hsPDA have a high response rate and low recurrence rate to prolonged low-dose indomethacin therapy. Side-effects were mild and transient. However, it is prudent to be cautious when administering indomethacin in critically ill infants < 1000 g with hsPDA who manifest clinical features of bowel ischaemia.

Anti-Inflammatory Agents, Non-Steroidal↗