Biomedical subjects
G Singh
Publications and source records attributed to G Singh.
Dermatoglyphics in ichthyosis vulgaris.
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Systematised comedo naevus.
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Dermatoglyphics in alopecia areata.
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Vitiligo and neurodermatitis circumscripta.
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Immunocytochemical localization of the surfactant apoprotein and Clara cell antigen in chemically induced and naturally occurring pulmonary neoplasms of mice.
The localization of surfactant apoprotein (SAP) and the Clara cell antigen(s) (CCA) was studied in naturally occurring and experimentally induced pulmonary hyperplasias and neoplasms by avidin-biotin peroxidase complex (ABC) immunocytochemistry. Lungs of B6C3F1 and A strain mice with naturally occurring lesions, B6C3F1 mice given injections of N-nitrosodiethylamine (DEN), BALB/c nu/nu or nu/+ mice exposed transplacentally on Day 16 of gestation to ethylnitrosourea (ENU), or BALB/c nu/+ mice exposed to ENU at 8-12 weeks of age were preserved in formalin or Bouin's fixative. After ABC immunocytochemistry, SAP was found in the cytoplasm of normal alveolar Type II cells; in the majority of cells in focal alveolar and solid hyperplasias originating in peribronchiolar or peripheral locations; and in solid, tubular, papillary, and mixed adenomas and carcinomas. The larger mixed-pattern neoplasms and small or large tubular neoplasms usually had the least number of cells with SAP. The majority of large papillary adenomas and carcinomas in BALB/c mice exposed to ENU and in untreated A strain mice contained SAP in the nuclei of many neoplastic cells but only in the cytoplasm of a few neoplastic cells. CCA was found in normal Clara cells of bronchi and bronchioles but not in any hyperplastic or neoplastic lesion of any mouse studied. This study provided immunocytochemical evidence that the vast majority of naturally occurring and experimentally induced pulmonary neoplasms of mice are alveolar Type II cell adenomas and carcinomas.
Immunocytochemical and morphological evidence for the origin of N-nitrosomethylurea-induced and naturally occurring primary lung tumors in F344/NCr rats.
Naturally occurring and N-nitrosomethylurea-induced lung tumors were studied in male F344/NCr rats by sequential histological, electron microscopic, and immunohistochemical methods. Rats were given one injection at 6 weeks of age of N-nitrosomethylurea at a dosage level of 41.2 mg/kg body weight i.v. Groups of rats were sacrificed at 20, 33, and 52 weeks, while some were sacrificed while moribund. Nine lung tumors from aged F344/NCr male rats were also studied. For determining localization of pulmonary antigens, sections of lungs were stained by the avidin-biotin-peroxidase complex immunocytochemical technique using antibodies to rat surfactant apoprotein or rat Clara cell antigen. At 20 weeks, in rats receiving N-nitrosomethylurea, focal alveolar type II cell hyperplasia, adenoma in focal alveolar type II cell hyperplasia, and adenoma were found in 15 (100%), 1 (7%), and 2 (13%) of 15 rats, respectively. At 33 weeks, there were 19 rats (95%) with focal alveolar type II cell hyperplasias, 10 rats (50%) with adenoma in focal alveolar type II cell hyperplasia, and 2 rats (10%) with adenomas in 20 rats. In 53 rats allowed to live up to 52 weeks, there were 10 (19%) adenomas and 3 (6%) carcinomas, as well as 49 (92%) rats with focal hyperplasia and 31 (58%) with adenomas in focal type II cell hyperplasia. Rat surfactant apoprotein was found in the cytoplasm of normal alveolar type II cells and the majority of cells in focal alveolar type II cell hyperplasias, adenomas in hyperplastic lesions, adenomas, and carcinomas. The ultrastructure of these lesions supported immunocytochemical findings with evidence of lamellar bodies. All nine naturally occurring lung tumors studied contained rat surfactant apoprotein. Rat Clara cell antigen was found, however, only focally within one adenoma induced by N-nitrosomethylurea and one adenoma in a hyperplastic lesion, and also focally in three neoplasms which occurred naturally. This study provided morphological, immunohistochemical, and ultrastructural evidence that the vast majority of N-nitrosomethylurea-induced and naturally occurring pulmonary neoplasms of F344 rats are alveolar type II cell adenomas and carcinomas and that a portion of these tumors arise within focal alveolar type II cell hyperplasias.
Erythromycin for BCG infections.
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Process of endothelial cell-death in cultured corneas.
Human and porcine corneas were cultured in organ-culture medium at 32 degrees C for long-term preservation and study of endothelial cell death. The endothelium was examined and re-examined at different intervals by using a phase contrast microscope and dual vital staining with alizarin-red S and trypan-blue. The appearance of degenerative vacuoles (which we called "death vacuoles" or "water-bubble bodies") as the first visible structural change in the process of cell death was very characteristic. While these vacuoles increased in size and number, the nucleus and cell-border disintegration was proceeding to the stage at which the cell was lost, leaving behind vacuoles on the Descemet's membrane, which we called the "endothelial graveyard."
A method for assessing damage to mitochondrial DNA caused by radiation and epichlorohydrin.
This paper describes a rapid and reliable method for quantification of damage to mitochondrial DNA (mtDNA), especially strand breaks. The degree of damage to mtDNA is assessed by the proportion of physical forms (i.e., supercoiled versus open-circular and linear forms) upon agarose gel electrophoresis, blotting, and visualization by hybridization with [32P]mtDNA probes. The use of a radiolabeled probe is a crucial step in the procedure because it provides both a means to quantify by radioautography and to obtain the mtDNA specificity required to eliminate misinterpretation due to nuclear DNA contamination. To demonstrate the utility of this technique, X-irradiation and epichlorohydrin are shown to damage both isolated mtDNA and mtDNA in whole cells in a dose-dependent fashion.
Effect of levamisole therapy on lepromin reaction in lepromatous leprosy cases.
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Corticosteroids in corneal endothelial wound healing.
Corticosteroids have inhibitory effects on corneal endothelial wound healing in organ-culture conditions. Low concentrations of methylprednisolone added to the culture medium inhibited the healing attempt and induced intracellular degenerative vacuoles and diffuse cell disintegration. Higher concentrations were highly toxic to the cell morphology and physiology and caused pronounced endothelial cell damage. These observations are compared with the normal healing of endothelial wounds in organ-culture conditions. Cell proliferation and amitotic and mitotic cell divisions repaired the endothelial layer in normal corneas.
The persistence of phorate and carbofuran in soil and rice plants.
The insecticides phorate and carbofuran applied at a range of 1 kg a.i./ha in a field trial against the important rice pest Hydronomidius molitor Faust, the rice root weevil, had largely degraded after 4 and 3 months, respectively, in flooded soil. In rice plants a strong decrease in the content of these insecticides was found three weeks after application. At the time of harvest, the rice plants did not contain any insecticide.
C-reactive protein in clinical practice.
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Cryoextraction versus forceps extraction of cataract under general versus local anesthesia.
Cryoextraction and forceps extraction of cataract are compared, with specific reference to their utility and practicability in developing countries. Because of cost and limited availability, cryoextraction is rarely performed in these areas. The decision whether to use general or local anesthesia is also discussed.
Endothelial cell densities in corneal donor material.
The mean endothelial cell count of 282 donated corneas was 2,665 cells/mm2, and the mean donor age was 56.01 years. The majority of the donors were over the age of 40 years, and the major causes of death were malignancies and myocardial infarction. Vital staining of the endothelium and direct evaluation of cells with an inverted phase contrast microscope were used in assessing the viability of this monocell layer. Evaluation of endothelial photomicrographs revealed that the cell count falls in the first three decades of life and eventually stabilizes around 2,600 cells/mm2. It is therefore suggested that patient age should not be the primary criterion for donor corneal selection.
Toxicity of methods of implant material sterilization on corneal endothelium.
The toxicity of different procedures utilized for the sterilization of intraocular implant material was assessed on the endothelium of organ-cultured porcine corneas. Polymethylmethacrylate lenses sterilized by treatment with sodium hydroxide (NaOH), ethylene oxide, formaldehyde, and gamma radiation were added to a culture medium containing normal porcine corneas. Considering the viability of endothelial cells, appearance of intracellular degenerative vacuoles, and denudation of corneal Descemet's membrane as criterion for the evaluation of toxicity of different methods of sterilization, the NaOH-treated lenses were found to be the least toxic to porcine corneal endothelium. Phase-contrast microscopy and vital staining of the endothelium permitted direct viewing of the endothelium aiding in the assessment of toxicity.