Biomedical subjects

D N Singh

Publications and source records attributed to D N Singh.

At least 19 recordsLinked to original sources

PubMed1996

Post-operative radiotherapy in carcinoma of buccal mucosa, a prospective randomized trial.

Squamous cell carcinoma of the buccal mucosa is a common cancer in India. We are referred a large number of locally advanced lesions where curative surgery is still possible. The objective of this study is to determine the role of post-operative radiotherapy in enhancing disease-free survival. Patients with stages III and IV cancer of the buccal mucosa potentially curable by surgery were randomized to surgery only or post-operative radiotherapy. Patients were followed up for 3 years. The clinico-pathological features in both arms were comparable. Disease-free survival at the end of the study was found to be 38% and 68% (P<0.005) respectively. Post-operative radiotherapy was thus seen to improve disease-free survival in squamous cell carcinoma of the buccal mucosa.

Carcinoma, Squamous Cell↗

PubMed1993

Clinical and cytogenetic survey of institutionalized mentally retarded patients with emphasis on the fragile-X syndrome.

A detailed clinical and cytogenetic survey for the fragile-X syndrome was undertaken on 201 institutionalized mentally retarded males with no previously recognized cause of retardation, and the causes of mental retardation were summarized from a total of 595 institutionalized male and female patients after the review of their medical records including clinical and cytogenetic data. Among the 201 males clinically and cytogenetically examined, five (2.5%) had abnormal chromosome findings with four (2%) having the fragile-X syndrome. Twelve of the males (6.0%) were diagnosed with a single gene disorder. In the present study, mental retardation was classified as possibly due to multifactorial causes when a genetic syndrome, chromosome abnormality or environmental insult was not identified, but mental retardation was present in one or more first and/or second degree relatives, but did not follow a recognizable inheritance pattern. Hence, mental retardation was recorded in other family members and may indicate possible multifactorial causes in 45 males (22.4%). An environmental insult was noted in 25 males (12.4%); unexplained birth defects in three males (1.5%); a specific condition or diagnosis identified, but cause unknown (e.g. Rubinstein-Taybi syndrome) in 10 males (5%); and no diagnosis made in the remaining 101 males (50.2%). Of all 595 patients (334 males and 261 females), including the 201 males who had undergone a detailed clinical and cytogenetic evaluation, 39 (6.6%) had abnormal chromosome findings, with Down's syndrome noted in 31 of the patients. Twenty-five patients (4.2%) were diagnosed with a single gene disorder while mental retardation was noted in other family members and may indicate possible multifactorial causes in 64 patients (10.8%). An environmental insult was noted in 170 patients (28.6%); unexplained birth defects in 17 patients (2.9%); a specific condition or diagnosis but cause unknown in 27 patients (4.5%); and no diagnosis made in 253 patients (42.5%). Clinical and cytogenetic screening of mentally retarded patients for the fragile-X syndrome and other causes of mental retardation is helpful in identifying individuals and their families who may benefit from genetic services such as counseling and treatment. This study was performed over an approximate 2 year period from 1987 to 1989.

Adolescent↗

PubMed1993

Anthropometric and craniofacial patterns in mentally retarded males with emphasis on the fragile X syndrome.

Anthropometric and craniofacial profile patterns indicating the percent difference from the overall mean were developed on 34 physical parameters with 31 white, mentally retarded males (23 adults and 8 children) with the fra(X) syndrome matched for age with 31 white, mentally retarded males without a known cause of their retardation. The fra(X) syndrome males consistently showed larger dimensions for all anthropometric variables, with significant differences for height, sitting height, arm span, hand length, middle finger length, hand breadth, foot length, foot breadth, and testicular volume. A craniofacial pattern did emerge between the two groups of mentally retarded males, but with overlap of several variables. Significant differences were noted for head circumference, head breadth, lower face height, bizygomatic diameter, inner canthal distance, ear length and ear width, with the fra(X) syndrome males having larger head dimensions (head circumference, head breadth, head length, face height and lower face height), but smaller measurements for minimal frontal diameter, bizygomatic diameter, bigonial diameter, and inner canthal distance. Several significant correlations were found with the variables for both mentally retarded males with and without the fra(X) syndrome. In a combined anthropometric and craniofacial profile of 19 variables comparing 26 white fra(X) syndrome males (13 with high expression (> 30%) and 13 with low expression (< 30%), but matched for age), a relatively flat profile was observed with no significant differences for any of the variables. Generally, fra(X) syndrome males with increased fragile X chromosome expression have larger amplifications of the CGG trinucleotide repeat of the FMR-1 gene. No physical differences were detectable in our study between fra(X) males with high expression and apparently larger amplifications of the CGG trinucleotide repeats compared with those patients with low expression. Our research illustrates the use of anthropometry in identifying differences between mentally retarded males with or without the fra(X) syndrome and offers a comprehensive approach for screening males for the fra(X) syndrome and selecting those individuals for cytogenetic and/or molecular genetic testing.

Adolescent↗

PubMed1991

A 15-item checklist for screening mentally retarded males for the fragile X syndrome.

A 15-item checklist, including physical and behavioral features frequently observed in fragile X syndrome, was used in a prospective study of 188 mentally retarded males in order to identify males at risk for this syndrome. Of the 188 males, 19 were found to have the fragile X syndrome, while the remaining 169 males had no recognizable cause of their mental retardation, including normal chromosomes. Significant differences (p less than 0.01) were found between mentally retarded males with and without the fragile X syndrome with increased hyperactivity; shorter attention span; more tactile defensiveness, hand-flapping, perseverative speech, and hyperextensibility; large ears and testes; higher frequency of simian creases or Sydney lines and plantar creases; and more positive family histories of mental retardation in the fragile X syndrome males. Multiple regression and discriminant analyses of the 188 males indicated several physical features were useful predictors for inclusion in the fragile X syndrome group. An overall correct classification rate of 93% was achieved based on 6 variables (plantar crease, simian crease, hyperflexibility, large testes, large ears, and a positive family history of mental retardation) that were entered into the discriminant equation. Therefore, our experience with a 15-item checklist suggests the potential of screening for the fragile X syndrome in mentally retarded males and that 6 of the 15 variables were particularly good predictors of this syndrome.

Adolescent↗

PubMed1989

Chromosomal mapping and nucleotide sequence of a human DNA autonomously replicating sequence.

A 1.1-kb human DNA fragment (ARSH1) capable of functioning as a putative origin of replication in yeast cells has been characterized both by in situ hybridization to human metaphase chromosomes and by DNA sequencing. Our hybridization studies show a preferential localization of ARSH1 in chromosome regions 1p34-36 and 2q34-37. DNA sequence analysis indicates that in addition to the consensus sequence required for ARS function in yeast cells, nuclear matrix-associated DNA motifs are also present in the 1.1-kb fragment. These results suggest that ARSH1 sequences may serve as points of anchorage to the nuclear matrix for chromosomes 1 and 2.

Amino Acid Sequence↗

PubMed1989

Immunocytochemical studies of astrocytes following injury to the cerebral cortex of the rat.

The morphological change of cerebral cortex astrocytes from protoplasmic to glial fibrillary acidic protein (GFAP)-containing cells is induced by injury. Protoplasmic astrocytes that contain no detectable amount of GFAP become filled with GFAP and their processes extend to form the glial scar around the wound. It is hypothesized that this transformation is induced by cAMP and neurotransmitters released from damaged neuronal cells. A similar mechanism may be present in other brain regions following injury or disease.

Animals↗

PubMed1989

Morphology and distribution of tanycytes in the third ventricle of the adult rat. A study using semithin methacrylate sections.

Light microscopy and semithin methacrylate sections were used to study the tanycytic projections and morphology in the floor of the third ventricle of the rat. The tanycytic cell soma was located in the ependyma. The luminal surface showed minute protrusions into the ventricular space and their basal processes projected across the width of the parenchyma of the infundibular region. During their course, tanycytic processes made contact with capillaries in the parenchyma and pial surface, suggesting that they might be involved in uptake and/or delivery mechanisms between the cerebrospinal fluid, hypothalamic cells and blood vessels.

Animals↗

PubMed1987

Urinary mucoprotein in pediatric urolithiasis.

Primary bladder stone is a common pediatric surgical problem in developing countries. Many theories are prevalent. The stone matrix theory is based on increased excretion of its precursor, the uromucoid (the urinary mucoprotein). Uromucoid, studied in urine and stones by the electroimmunodiffusion technique in 49 cases with controls, showed significantly increased excretion in stone cases. Family income and serum protein were the only important influencing factors (negative). Causal relationship between uromucoid excretion, stone matrix, and pediatric bladder stones is discussed. Methylene blue decreased uromucoid excretion but not magnesium oxide, vitamin C or B6 (four common therapeutic drugs for prevention/dissolution of urolithiasis).

Ascorbic Acid↗

PubMed1987

Adrenomedullary chromaffin cells of the rat. An ultrastructural study.

Adrenomedullary chromaffin cells of the rat were studied at the ultrastructural level. Chromaffin cells contained a large population of electron-dense-core vesicles of two types, one very electron-dense (norepinephrine) and the other moderately electron-dense (epinephrine). The vesicles showed an even distribution pattern in the cytoplasmic matrix. No physical contacts were observed between cytoplasmic and vesicle membranes to indicate exocytosis, a mechanism frequently observed in the hamster. For chromaffin cells to be used as a transplantable source of dopamine, both the cells and vesicles must survive the trauma of denervation and vascular elimination or alternatively acquire the two factors from the transplantation site.

Adrenal Medulla↗

PubMed1986

Survival of adrenal gland implants in the neocortex of the rat: a morphological study.

The survival of adrenal gland implantation in the cerebral cortex of the rat was studied. In the present study, mature adrenal gland had survived after six months of implantation. No scar tissue was observed between the adrenal gland cortex and the host cerebral cortex. The implanted tissue showed some reorganization in its cortex and medulla. In the adrenal cortex there was an observable increase in connective tissue fibers and some degeneration of cells. In the medulla, again, both surviving and degenerating cells were observed. This study shows that mature adrenal gland has the capacity to survive after implantation in the cerebral cortex of the rats. Further studies are being carried out on fetal and mature tissue implantation and the ability of the adrenal medulla to secrete catecholamines.

Adrenal Glands↗

PubMed1984

Ultrastructural study of lysosomes in the myocardium of spontaneously hypertensive rats under chronic salt ingestion.

The presence of lysosomes and lysosomal-like bodies in the myocardium of spontaneously hypertensive rats (SHRs) under the influence of 1% NaCl was studied. In SHRs, 2 weeks and older, there was an observable increase of lysosomes and lysosomal-like bodies in the myocardium when compared to the myocardium of age-matched controls. It is postulated that degradation is initiated by primary lysosomes and that mitochondria seem to be a prime target. The degradation process is also believed to be a relevant factor in cardiac hypertrophy of SHRs and that a high NaCl intake coupled with a sustained high blood pressure enhanced this process.

Animals↗

PubMed1983

Effects of chronic salt intake on the capillaries in the cerebral cortex of spontaneously hypertensive rats (SHRs): an ultrastructural study.

Fine structural changes of capillaries in spontaneously hypertensive rats (SHRs) under the influence of 1% NaCl were studied. In SHRs (control), 30 weeks and older, capillaries showed deformed lumina, hypertrophy of endothelial cells and matrical alterations of mitochondria. Deformed capillary lumina, fibrosis in upper stream vessels and swelling of astrocytic processes were observed in the saline-treated SHRs. The significance of these findings is discussed.

Animals↗

PubMed1982