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T Sharma

Publications and source records attributed to T Sharma.

At least 127 records · Page 7Linked to original sources

Schizophrenia and the androgen receptor gene: report of a sibship showing co-segregation with Reifenstein syndrome but no evidence for linkage in 23 multiply affected families.

Crow et al. [1993: Am J Med Genet (Neuropsychiatr Genet) 48:159-160] have reported excess sharing of alleles by male sibling pairs with schizophrenia, at a triplet repeat marker within the androgen receptor gene, indicating that mutations at or near this gene may be a risk factor for males. In this report, we describe a pair of male siblings concordant for both schizophrenia and Reifenstein syndrome, which is caused by a mutation in this gene. This provides support for the hypothesis that the androgen receptor may contribute to liability to develop schizophrenia. Because of this, we have examined a collection of 23 pedigrees multiply affected by schizophrenia for linkage to the androgen receptor. We have found no evidence for linkage by both the LOD score and affected sibling-pair methods, under a range of genetic models with a broad and narrow definition of phenotype, and when families with male-to-male transmission are excluded. However, because of the small number of informative male-male pairs in our sample, we cannot confirm or refute the excess allele sharing for males reported by Crow.

Adolescent↗

Linkage analysis of chromosome 22q12-13 in a United Kingdom/Icelandic sample of 23 multiplex schizophrenia families.

A possible linkage to a genetic subtype of schizophrenia and related disorders has been reported on the long arm of chromosome 22 at q12-13. (Pulver et al., 1994: Am J Med Genet 54:36-43; Coon et al., 1994: Am J Med Genet 54:72-79; Pulver et al., 1994: Am J Med Genet 54:44-50). However formal statistical tests in a combined sample could not reject homogeneity and prove that there was a linked subgroup of families. We have studied 23 schizophrenia pedigrees to test whether some multiplex schizophrenia families may be linked to the microsatellite markers D22S274 and D22S283 which span the 22q12-13 region. Two point followed by multipoint lod and non-parametric linkage analyses under the assumption of heterogeneity provided no evidence for linkage over the relevant region.

Chromosomes, Human, Pair 22↗

Computerized brain tissue classification of magnetic resonance images: a new approach to the problem of partial volume artifact.

Due to the finite spatial resolution of digital magnetic resonance images of the brain, and the complexity of anatomical interfaces between brain regions of different tissue type, it is inevitable that some voxels will represent a mixture of two or three different tissue types. Outright assignment of such "bipartial" or "tripartial" voxels to one class or another is more problematic and less reliable than assignment of "full-volume" voxels, wholly representative of a single tissue type. We have developed a computerized system for brain tissue classification of dual echo MR data, which uses a polychotomous logistic model for discriminant analysis, combined with a Bayes allocation rule incorporating differential prior probabilities, and spatial connectivity tests, to assign each voxel in the image to one of four possible classes: gray matter, white matter, cerebrospinal fluid, or unclassified. The system supports automated volumetric analysis of segmented images, has low operational overheads, and compares favorably with previous multivariate or "multispectral" approaches to brain MR image segmentation in terms of both validity (bootstrap misclassification rate = 3.3%) and interoperator reliability (intra-class correlation coefficients for all three tissue classes > 0.9). We argue that these improvements in performance stem from better methodological management of the related problems of non-Normality of MR signal intensity values and partial volume artifact.

Artifacts↗

Pattern of retinal breaks and retinal detachments in eyes with choroidal coloboma.

PURPOSE: To describe the type of breaks that occur in the diaphanous tissue within the coloboma of the choroid and the types of retinal detachment that are associated with these breaks. METHODS: This is a retrospective study of 36 eyes of 36 patients with retinal detachments that extended into the choroidal coloboma. Preoperative findings were documented using detailed fundus drawings and color photographs. Intraoperative identification of retinal breaks was possible using high magnification of the operating microscope. RESULTS: Based on the identifiable breaks inside the coloboma and the extent of retinal detachment, these patients were divided into five subgroups. Three distinct types of breaks were identified within the coloboma: (1) breaks at the edge of the detachment inside the coloboma; (2) oval atrophic breaks; and (3) breaks in anatomic macula that was involved in the coloboma. Multiple breaks were common. CONCLUSIONS: Retinal detachments that extend into the colobomatous area always are associated with breaks in the diaphanous tissue. Intraoperative identification of these breaks is relatively easy. Commonly, the breaks are seen at the edge of the retinal detachment inside the coloboma or as oval breaks within the detached diaphanous tissue. Macula, if involved in the coloboma, occasionally can harbor a retinal break.

Adolescent↗

Exclusion of linkage of schizophrenia to the gene for the dopamine D2 receptor (DRD2) and chromosome 11q translocation sites.

There have been previous reports of a 1q43;11q21 translocation cosegregating with schizophrenia and a 9p22;11q22.3 translocation cosegregating with manic depression. In addition, the genes for the dopamine D2 receptor and for tyrosinase both map to chromosome 11q. Three 11q DNA markers were used to investigate 23 pedigrees containing multiple cases of schizophrenia. Strongly negative lod scores were obtained, providing evidence against linkage over a 70 cM region which included both translocation sites and both candidate genes.

Chromosome Mapping↗

Vitrectomy for accidental intraocular steroid injection.

BACKGROUND: Accidental perforation of the globe and intraocular injection of steroid is a potential complication of periocular injections. Final outcomes in eyes in which this complication has occurred have been reported to be unsatisfactory in the past. However, the advent of vitrectomy has altered their prognosis significantly. METHODS: A retrospective analysis was done of five cases of accidental intraocular steroid injection, treated by vitrectomy. Additional procedures involved treatment of retinal breaks (where required) with endolaser or transscleral cryopexy. Scleral buckling was done in one case. RESULTS: Barring one case in which retinal detachment developed, there were no postoperative complications. At last follow up all patients had satisfactory recovery of visual acuity; had attached retina; and quiet anterior chamber and vitreous cavities. CONCLUSION: Vitrectomy is associated with satisfactory results in cases of accidental intraocular steroid injection. Delay up to a few days does not seem to materially influence the outcome.

Adolescent↗

Cytochrome P4502D6 genotype does not determine response to clozapine.

1. The atypical antipsychotic drug clozapine, used in the treatment of resistant schizophrenia, is metabolized partly by the hepatic cytochrome P450 enzyme CYP2D6. Two phenotypes with respect to the activity of the enzyme are recognized (extensive metabolisers (EM) and poor metabolisers (PM)), resulting from allelic variation in the gene, CYP2D6. 2. Genotype was determined in 123 schizophrenic patients currently being treated with clozapine, in order to determine if EM or PM status influences response to this drug. Patients were divided into responders and non-responders using the Global Assessment Scale, and genotyped for the A and B poor metaboliser mutations by digesting PCR products with HpaII or BstNI. 3. Fifty-nine patients were heterozygous for allele B and for allele A. Eight patients were determined as poor metabolisers since they were homozygous either for A and B. Poor metabolisers were equally distributed between responders and nonresponders and no correlation between CYP2D6 alleles and response to clozapine was found. 4. The results are consistent with recent findings showing that CYP1A2, rather than CYP2D6, is the major enzyme responsible for the metabolism of clozapine.

Alleles↗

Investigation by linkage analysis of the XY pseudoautosomal region in the genetic susceptibility to schizophrenia.

BACKGROUND: A susceptibility locus for schizophrenia in the pseudoautosomal region has been proposed on the basis of a possible excess of sex chromosome aneuploidies among patients with schizophrenia and an increased sex concordance in affected sib pairs. Several studies investigating this hypothesis have produced conflicting evidence. METHOD: In a series of Icelandic and British families, we used lod score and sib pair linkage analyses with markers for the MIC2 and DXYS14 loci on the pseudoautosomal XY region. RESULTS: Lod and sib pair linkage analysis with these markers produced strongly negative scores. Heterogeneity testing also produced negative results. CONCLUSION: We conclude that the present study provides no support for the involvement of either the pseudoautosomal region or the nearby region of the sex chromosomes in the aetiology of schizophrenia.

Aneuploidy↗

Investigations in the virological etiology in acute retinal inflammation.

Virological investigations for herpes simplex virus (HSV), cytomegalovirus (CMV) and Epstein-Barr virus (EBV) were performed in nine patients of acute retinal inflammation. Serum samples of all the patients were assayed for IgG and IgM antibodies to HSV, CMV and EBV. Vitreous fluid (VF) from 5 patients was tested by immunofluorescence and culture for detection of HSV and CMV. In four patients, VF was also assayed for IgG and IgM antibodies to HSV and CMV. HSV was shown to be the etiological agent in 3 patients with acute retinal necrosis (ARN) syndrome and in one patient with multifocal retinitis. CMV was the causative agent in one patient of ARN and 1 patient with clinically diagnosed CMV retinitis. Evidences of infection with these three viral agents could not be obtained in one patient with clinical diagnosis of CMV retinitis who tested positive for antibody to human immunodeficiency virus 1. All other patients were HIV negative. Identification of the causative viral agent of acute retinal inflammations may help an ophthalmologist to institute specific therapy particularly for HSV and CMV infections.

Acute Disease↗

Endophthalmitis caused by anaerobic bacteria.

A retrospective analysis of 22 patients who underwent pars plana vitrectomy for endophthalmitis and had culture-proven anaerobic bacteria, was done. Elimination of infection with attached retina and recovery of ambulatory vision > or = 2/60 were considered as anatomic success and functional success, respectively. Mean follow-up period was 12.7 months (range, 2 to 48 months). Anatomic success was attained in 14 (63.6%) eyes and functional success in 12 (54.6%) eyes. A poor preoperative visual acuity was found to be associated with poor functional outcome (p < 0.046). In endophthalmitis, a routine anaerobic culture of intraocular specimen is recommended.

Adolescent↗

Retinopathy of prematurity: a study.

A total of 50 infants of less than 2000 gm birth weight were screened for retinopathy of prematurity (ROP) by binocular indirect ophthalmoscopy. The incidence of ROP was found in 19 patients (38%). Of these, 8 patients (16 eyes) had threshold disease. Significantly, occurrence of threshold ROP was seen in both 1600 gm birth weight in one infant and in the absence of oxygen administration in 2 infants. Ten of the 16 eyes underwent therapeutic intervention while 6 eyes did not receive treatment for lack of consent from the parents. The treatment consisted of indirect laser photocoagulation (8 eyes) and transconjunctival cryopexy (2 eyes). Good regression of the disease (favourable outcome) was noted in all the treated eyes.

Birth Weight↗

Photodynamic enhancement of doxorubicin cytotoxicity.

Argon ion laser irradiation at 514.1 nm and 488 nm dramatically increased doxorubicin cytotoxicity in an L929 cell clonogenic survival assay. The cytotoxicity was dependent on both the drug concentration and the total light energy delivered such that at 5 micrograms doxorubicin/ml and 800 J/cm2, cytotoxicity was enhanced by a factor of > 10(4) relative to that achieved with drug alone. Irradiation times in excess of 2 min and power densities in excess of 100 J/cm2 were required to produce the effect. Beyond this 2-min limit, cytotoxicity was not related to the duration of exposure if the total energy delivered was held constant. The ability of catalase and superoxide dismutase to abolish completely the increase in cytotoxicity produced by laser irradiation suggests that the cytotoxic mechanism may depend on the generation of active oxygen species by the photodynamically excited drug.

Animals↗

Scleral buckling for retinal detachment. Predictors for anatomic failure.

PURPOSE: The influence of various preoperative, intraoperative, and postoperative factors on retinal reattachment after scleral buckling was examined. METHODS: A study of 601 eyes of 577 consecutive patients who underwent conventional scleral buckling procedures was conducted. Multiple logistic regression analysis was used to determine the independent influence of each variable on anatomic failure. RESULTS: Anatomic reattachment of the retina was achieved in 86% of eyes after a single procedure, and in 90% of eyes after a second surgical procedure, with a mean follow-up period of 5.27 months (range, 2-29 months). Factors predictive of poor anatomic success (P < 0.05) included preoperative choroidal detachment and significant vitreous opacification; circumferential buckle extent of more than two quadrants and intravitreal injection of air or fluid intraoperatively; and postoperative occurrence of sterile vitritis. CONCLUSION: Breakdown of the blood-retinal barrier leading to cellular migration and proliferation is considered to be predictive of anatomic failure after scleral buckling procedures.

Adolescent↗

Intraocular Gnathostoma spinigerum. Clinicopathologic study of two cases with review of literature.

BACKGROUND: Live intraocular nematode is a rare occurrence that is mostly reported in Southeast Asian countries. Common nematodes that are seen live in the eye are microfilaria, Gnathostoma, and Angiostrongylus. Approximately 12 cases of intraocular gnathostomiasis have been reported in the literature. METHOD: Two cases of intraocular gnathostoma, removed by vitrectomy in the first case and by paracentesis in the second case, are reported. Morphologic study of the parasites in wet preparation was performed under dissecting microscope and fixed in Karnovosky's fixative. Light microscopic and scanning electron microscopic studies were also performed. RESULTS: The first patient had anterior uveitis, multiple iris holes, and dense vitreous haze with fibrous proliferation over the optic disc. On resolution of the vitreous haze, a live worm was seen in the vitreous cavity. The second patient had anterior uveitis with secondary glaucoma, multiple iris holes, mild vitritis, and focal subretinal haemorrhage with subretinal tracts. Four days later a live worm was seen in the anterior chamber and removed. Microscopic study of the parasites from both patients revealed typical head bulb with four circumferential rows of hooklets, and fine cuticular spines were seen on the surface of the body. CONCLUSIONS: Iris holes, uveitis, and subretinal haemorrhage with subretinal tract can be characteristic features of intraocular gnathostomiasis. Identification of this parasite can be made by typical features, which can be identified on light and scanning electron microscopic study.

Adult↗

The Marfan syndrome gene locus as a favoured locus for susceptibility to schizophrenia.

Marfan syndrome (MS) is a rare autosomal dominant disorder of connective tissue with manifestations in the cardiovascular, ocular and skeletal systems. Genetic linkage analysis with random probes has mapped the MS locus to 15q21.1. There have been several reports of Marfan syndrome co-segregating with schizophrenia within families, which suggest that a common genetic factor may be shared between schizophrenia susceptibility and MS. This could be due to a cytogenetic abnormality affecting both genetic loci or due to co-segregation of two disease loci near each other on the same chromosome. We tested this hypothesis by using genetic linkage analysis with multiplex families. Using three genetic markers spanning the MS locus, we were unable to find evidence of linkage with schizophrenia across the Marfan syndrome locus on chromosome 15.

Chromosomes, Human, Pair 15↗

The chromosomal distribution of Mus musculus-like AT-rich heterochromatin in the M. dunni complex as revealed by AluI digestion of metaphase chromosomes.

In situ digestion of metaphase chromosomes with AluI revealed differences in the distribution of Mus musculus-like AT-rich heterochromatin in the complements of the Indian pygmy field mice, M. booduga and M. dunni. In M. booduga, although the banding pattern was almost comparable to that of M. musculus, AluI-resistant bands were much reduced in size at the centromeric regions. In all three chromosome types of the M. dunni complex, M. musculus-like AT-rich heterochromatin was found to be confined mainly to two small segments on the short arm of the X chromosome. This AT-rich heterochromatin varied greatly in both position and quantity in the two X chromosomes. In addition to the polymorphism, a whole block of M. musculus-like AT-rich heterochromatin was found at the centromeric region of an autosome in one individual of M. dunni.

Adenine↗