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Biomedical subjects

K M Khan

Publications and source records attributed to K M Khan.

At least 109 records · Page 6Linked to original sources
PubMed1993

Immunohistochemical localization of S-100 protein in the saccule of the rainbow trout (Salmo gairdnerii R.).

The distribution of S-100-like immunoreactivity in the trout saccule (a presumed organ of hearing in fish) has been determined by means of immunohistochemistry. Within the sensory epithelium of the saccular macula, hair cells and myelinated saccular nerve fibers were found to be immunoreactive. Hair-cell immunoreactivity was relatively uniform throughout the macula except at the extreme periphery (rostral, caudal, ventral and dorsal), where staining was either decreased or absent. The immunoreactivity associated with myelinated nerve fibers was greatest at the peripheral edges of the nerve processes, a position corresponding to the location of Schwann cells. However, the nerve processes themselves (within and subjacent to the sensory epithelium), as well as cell bodies within the saccular nerve, were also immunoreactive. Thus, the immunoreactivity of the saccular nerve observed above the basal lamina can be attributed to the saccular nerve processes as well as to nerve-associated Schwann cells. Overall, the immunoreactivity displayed by hair cells was less intense than that associated with myelinated saccular nerve, as evidenced by a disappearance of signal in hair cells first, upon serial dilution of antibody. No S-100-like immunoreactivity was observed in supporting cells within the sensory epithelium or in epithelial cells in non-sensory regions. A concentration of S-100-like immunoreactivity in hair cells and saccular nerve is suggestive of the presence of S-100 calcium-binding protein-mediated activities in these cell types.

Animals↗
PubMed1993

Analysis of gamma-aminobutyric acidA receptor subunits in the mouse cochlea by means of the polymerase chain reaction.

Thirteen GABAA receptor subunits were examined in the cochlea of the CBAJ mouse by PCR analysis. Total RNA was extracted from the auditory organs of 14-18-day-old animals, and mRNA was isolated using oligo-dT cellulose. After reverse transcription, resulting cDNA was amplified by PCR with primers specific for nucleotide sequences representing GABAA subunits. PCR products corresponding to subunits alpha 1-alpha 6, beta 1-beta 3, and gamma 2 were amplified, whereas those representing gamma 1, gamma 3, and delta were not amplified above background. These results provide the most direct evidence to date that GABAA receptors composed of the detected subunits are expressed in the mammalian cochlea, lending new support to previous studies implicating GABA as a cochlear transmitter. The pronounced expression of alpha 2 and alpha 6 subunits suggests type II and "cerebellar-type" benzodiazepine pharmacology in the cochlea.

Animals↗
PubMed1993

Stress fractures of the tarsal navicular bone: CT findings in 55 cases.

OBJECTIVE: The purpose of this article is to present the CT findings in 55 cases of tarsal navicular stress fracture before and after treatment and to describe the CT protocol used. MATERIALS AND METHODS: Fifty-five navicular stress fractures in 54 patients whose initial and follow-up CT scans were available for study were retrospectively reviewed. In most cases, contiguous 1.5-mm axial and 3-mm coronal scans of the navicular bone had been obtained. Both feet were scanned for comparison. Follow-up scans were obtained between 4 weeks and 6 years. RESULTS: On review, fractures were evident in all cases, but six small fractures (11%) were missed at the initial interpretation. All fractures involved the central third of the proximal dorsal margin of the navicular bone. Fifty-three fractures (96%) were partial. Forty-three partial fractures were linear, five were linear with bone fragments, and five were rim defects with ossicles. In 13 cases (24%) the fracture was small, 10% or less of bone height. The earliest sign of healing, slight dorsal cortical bridging, was seen in three of eight cases in which follow-up was done at 6 weeks. Firm cortical union was noted in 10 (32%) of 31 by 4 months. Nonunion occurred in 12 and was indicated by the persistence of the fracture gap and lack of cortical healing. Medullary cysts (five) and cortical notching (two) were noted to persist after complete healing. CONCLUSION: CT scanning is a suitable method for detecting navicular stress fracture and for performing follow-up examinations. Small fractures may be overlooked owing to lack of familiarity with their appearance.

Adolescent↗
PubMed1991

The histochemical localization of acetylcholinesterase in the rainbow trout saccular macula by electron microscopy.

The hair cells of the teleost saccular macula are morphologically similar to type II vestibular hair cells of higher vertebrates. The two types of nerve endings at the base of the saccular hair cells are the non-vesiculated endings, thought to be afferent, and the vesiculated terminals, presumed to be efferent. The vesicles in the presumptive efferent endings are predominantly round and clear, and a few are dense cored. The morphological characteristics of the vesiculated endings resemble those of presumptive efferent cholinergic endings present in the inner ear of higher vertebrates. In the present study, vesiculated nerve endings were examined histochemically for acetylcholinesterase. The reaction product was observed along the plasma membranes of the vesiculated nerve endings synapsing both with the hair cells and afferent endings, but was not seen at non-vesiculated endings on hair cells. No staining was observed in control specimens incubated in the presence of eserine sulfate, an inhibitor of acetylcholinesterase. These results suggest that the vesiculated nerve endings in the trout saccular macula contain cholinergic elements.

Acetylcholinesterase↗
PubMed1991

Carbohydrates associated with the cell coat surrounding cells of the rainbow trout saccular macula as revealed by lectin probes.

The luminal surface of the saccular macula in the rainbow trout is covered with a glycoconjugate-rich cell coat. The aim of this study was to identify specific carbohydrate moieties present in this coat, using biotinylated lectins as probes. Saccular tissues were fixed in Karnovsky's fixative for 2 h at 1-2 degrees C, followed by incubation with biotinylated lectins for 12-16 h at 25 degrees C. Lectin binding was visualized by performing avidin-biotin-peroxidase reactions. As controls, specimens were reacted with solutions of lectins preincubated with their specific inhibitory sugars. Staining was observed that was consistent with the presence of glucose, galactose, fucose, mannose, N-acetylglucosamine, N-acetylneuraminic acid, and N-acetylgalactosamine in the cell coat. The variability in the intensity of staining associated with the lectin-carbohydrate complexes suggests quantitative differences among the various carbohydrate moieties detected. The presence of these carbohydrates in the cell coat of the trout saccular macula also suggests biochemical similarities between cell coats in teleost and mammalian inner ear structures.

Animals↗
PubMed1990

Proteins of the gelatinous layer of the trout saccular otolithic membrane.

Although the otolithic membrane is thought to play an important role in the stimulation of vestibular hair cells, little is known about its chemical composition. We analyzed proteins of the gelatinous layer of this structure from the trout saccule, a probable organ of hearing in fish, by SDS-polyacrylamide gel electrophoresis. A relatively small number of major proteins were detected in homogenates of the 'membrane' layer, with apparent molecular weights ranging from 35 to greater than 300 kDa. Six bands, with molecular weights of 35, 43, 65, 94, 100, and 160 kDa, were particularly prominent. Periodic acid-Schiff (PAS) staining indicated that the 43, 94, 100, and 160 kDa bands were glycoproteins. Lectin binding on nitrocellulose blots confirmed the PAS results, and further suggested that the 35 and 65 kDa bands may be glycoproteins. Incubation of blots with human anti-collagen type II antibodies suggested that the 94 kDa band was a component of collagen type II or a related protein.

Animals↗
PubMed1990

The cell coat of the sensory and supporting cells of the rainbow trout saccular macula as demonstrated by reaction with ruthenium red and tannic acid.

The surface of most cells is covered by glycoconjugates. The composition and thickness of the surface coat varies among different cell types. The purpose of the present study was to demonstrate the presence of and to characterize the cell coat surrounding the cells in the saccular macula of the rainbow trout. Tissues were fixed in Karnovsky's fixative containing either ruthenium red (0.5, 1, or 2%) or tannic acid (1, 2, or 4%). The apical surface of the sensory and supporting cells reacted with both agents. Varying the concentration of the compounds within a certain range did not significantly affect the degree of tissue staining. Whereas ruthenium red staining was distributed evenly along the luminal surface of the epithelium and along the length of the stereocilia, tannic acid formed electron-dense clumps on the luminal surface of sensory and non-sensory cells and in the basal region of the macular epithelium. The stereocilia of the sensory cells also exhibited tannic acid-positive, electrondense precipitate, particularly near the distal ends of these processes, while uniform staining of the plasma membrane was seen along their lengths. The results of this study suggest that the trout saccular macula is provided with extracellular microenvironments which may be necessary for functional integrity.

Animals↗
PubMed1989

Protein associated with the sensory cell layer of the rainbow trout saccular macula.

A protein has been detected that is associated with the saccular hair cell layer of the rainbow trout, Salmo gairdnerii R. By one- and two-dimensional SDS polyacrylamide gel electrophoresis, the molecular weight and isoelectric point of this protein are estimated to be 13.6 and 8.8 kDa, respectively. The 13.6 kDa protein cannot be detected electrophoretically in brain, gill, liver, and fractions containing the basal lamina, non-sensory epithelium, and saccular nerve. This protein does not bind antibodies to bovine myelin basic protein, while trout myelin basic proteins in the same molecular weight range do. In addition, the protein does not bind concanavalin A or react with the periodic acid-Schiff reagent. The 13.6 kDa band represents about 1% of the total protein in saccular sensory epithelium, and may be a marker protein for the hair cell layer.

Animals↗
PubMed1989

Sequestration and degradation of alpha 2u-globulin in rat kidney lysosomes.

alpha 2u-Globulin (M.W. = 18,709) is the major protein synthesized in the liver of adult male rats. alpha 2u-Globulin, secreted from the liver, is filtered by the kidneys where about a half of the protein is reabsorbed and the remainder is excreted in the urine. Highly purified lysosomes from rat kidneys were subjected to immunoblot analysis using antiserum against alpha 2u-globulin. A major immuno-reactive band was observed at the position about 1 k dalton smaller than that of the authentic alpha 2u-globulin. The immuno-reactive band in SDS-polyacrylamide gel was excised and the protein, eluted from the gel, was subjected to amino acid sequence analysis by micro Edman method. The N-terminal amino acid sequence of the intralysosomal alpha 2u-globulin was found to be leu-asp-val-ala-lys-leu-asn-gly-... which exactly corresponded to the sequence from the 10th leucine residue of the authentic urinary alpha 2u-globulin. This result suggests that alpha 2u-globulin, sequestered into the kidney lysosomes, is cleaved intralysosomally between the 9th asparagine and the 10th leucine, and the degradative intermediate, thus produced, is accumulated in the lysosomes. The immuno-blot assay gave the value of 210 +/- 70 mg alpha 2u-globulin/g kidney lysosomal proteins. The molecular basis for the resistance of the degradative intermediate of alpha 2u-globulin against further degradation in the kidney lysosomes was discussed in the light of the computer-predicted secondary structure of alpha 2u-globulin.

Alpha-Globulins↗
PubMed1988

Degradation of aspartate aminotransferase in rat liver lysosomes.

Highly purified lysosomes from the normal and leupeptin-treated rat livers were subjected to immunoblot analysis using antibodies against cytosolic and mitochondrial isozymes of aspartate aminotransferase (cAspAT and mAspAT). In the case of cAspAT (subunit M.W. = 46K), the leupeptin-treated lysosomes showed a major band of 46K and a minor band of 36K while normal lysosomes showed a major band of 36K and a minor band of 41K. In the case of mAspAT (subunit M.W. = 44K), the leupeptin-treated lysosomes showed a 44K band and the normal lysosomes showed a 40K band. These observations suggest that both cAspAT and mAspAT are sequestered into lysosomes with the original subunit molecular weights and are degraded in the lysosomes by way of sequential formation of relatively stable intermediates with distinct molecular weights.

Animals↗
PubMed1984

Morphologic study of effects of kanamycin on the developing cochlea of the rat.

The development of the rat inner ear starts about day 9 of a 22-day gestational period. The sensory and supporting cells are morphologically identifiable by day 18 of gestation; however, auditory function is not evident until day 9 postnatally. The organ of Corti attains adult maturity about day 16 postnatally. Morphologic and physiologic studies have shown that administration of sublethal doses of aminoglycosidic antibiotics, including kanamycin, damages the sensory and supporting cells of the inner ear in mammals. This results in the impairment of auditory function. This study was designed to determine the earliest stage in cochlear duct development at which kanamycin toxicity can be morphologically detected. A sublethal dose of kanamycin was administered to pregnant rats on days 10 through 20 of gestation and to neonates from days 1 to 8 or from days 8 to 16 postnatally. The inner ears were dissected and processed for light microscopic and ultrastructural observations. The cochlear ducts of fetuses exposed in utero to kanamycin and those of neonates exposed from days to 1 to 8 postnatally were unaffected. Kanamycin toxicity was evident in the cochlear ducts of neonates exposed from days 8 to 16 postnatally. The most severe damage occurred in the basal coil of the cochlea where in many instances sensory cells were totally absent. The sensory cells in the middle and apical coils exhibited abnormal morphology. These results suggest: (1) kanamycin does not have any permanent toxic effects on the rat cochlear duct during gestation and the first week of postnatal life. This provides a basis for further studies into the possible pharmacologic application of this finding in humans. (2) A correlation exists between the initiation of auditory function and the vulnerability of the organ of Corti to kanamycin toxicity.

Age Factors↗
PubMed1983

Clinical and immunogenetic studies in rheumatoid arthritis from northern India.

A total of 258 patients with classic rheumatoid arthritis seen over a 7-year period were included in this study. The majority of the patients had relatively mild disease at the time of presentation. The incidence of extraarticular manifestations such as subcutaneous nodules, vasculitis, amyloidosis and pulmonary involvement was low although one or two pulmonary function test parameters were abnormal in some. Seventy patients were tested for all three subclasses of rheumatoid factors - IgM, IgG and IgA. Of these, 23 patients had all three whilst four had only IgG. The 62 patients who had most typical and severe manifestations were typed for four major HLA loci A, B, C and DR. Of these 42 (67.7%) had DR4 antigen while DR3 antigen was detected in 14 (22.6%).

Adult↗