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Biomedical subjects

S Roy

Publications and source records attributed to S Roy.

At least 397 records · Page 22Linked to original sources
PubMed1996

Three-dimensional time-of-flight MR angiography of the arch of aorta and its major branches: a comparative study with contrast angiography.

The region of the arch of aorta and the intrathoracic course of its major branches was evaluated in 11 patients using three-dimensional time-of-flight magnetic resonance (MR) angiography. Abnormalities such as stenosis, occlusion, dilatation and aneurysm formation were documented in the innominate, both common carotid and both subclavian arteries. The results were compared with those of contrast angiography. There was a good correlation in 47 of the 55 arteries compared. There were five false positive results including overestimation of a stenosis, and three false negative results including underestimation of a stenosis. MR angiography had a sensitivity of 93% and a specificity of 89% for correctly detecting or excluding an abnormality. These results suggest that three-dimensional time-of-flight MR angiography demonstrates lesions in the major branches of the arch of aorta fairly accurately and will prove useful in the initial evaluation and in follow up studies.

Adolescent↗
PubMed1996

Tropoelastin gene expression in optic nerve heads of normal and glaucomatous subjects.

Elastic fibers are a major component of the extracellular matrix in the optic nerve head (ONH) and undergo marked morphological changes during primary open angle glaucoma (POAG). Previous findings indicated that there is reactivation of tropoelastin mRNA synthesis in glaucoma. In this study, we sought to determine the alternative splicing pattern of tropoelastin in the human optic nerve head and in cultured laminar astrocytes. Furthermore, we compared the alternative splicing pattern of normal elastogenesis with that of reactivation of elastin synthesis in patients with primary open angle glaucoma. Our results demonstrate that exons 23 and 32 of tropoelastin are alternatively spliced in the normal ONH as well as in tissue from glaucomatous patients. There are no qualitative differences. We also demonstrated that astrocytes from the ONH synthesize tropoelastin in vitro. In conclusion, we have demonstrated a tropoelastin alternative splicing pattern in the human optic nerve head and laminar astrocytes. Abnormalities in elastic fibers in the ONH of patients with POAG are not due to an aberrant splice variant of tropoelastin. Astrocytes grown from ONH explants may serve as an in vitro model to study extracellular matrix changes in glaucoma.

Adult↗
PubMed1996

Oligomerization and maturation of Na,K-ATPase: functional interaction of the cytoplasmic NH2 terminus of the beta subunit with the alpha subunit.

Subunit assembly plays an essential role in the maturation of oligomeric proteins. In this study, we have characterized the main structural and functional consequences of the assembly of alpha and beta subunits of Na,K-ATPase. Xenopus oocytes injected with alpha and/or beta cRNA were treated with brefeldin A, which permitted the accumulation of individual subunits or alpha-beta complexes in the ER. Only alpha subunits that are associated with beta subunits become resistant to trypsin digestion and cellular degradation. Similarly, assembly with beta subunits is necessary and probably sufficient for the catalytic alpha subunit to acquire its main functional properties at the level of the ER, namely the ability to adopt different ligand-dependent conformations and to hydrolyze ATP in an Na(+)- and K(+)-dependent, ouabain-inhibitable fashion. Not only the alpha but also the beta subunit undergoes a structural change after assembly, which results in a global increase in its protease resistance. Furthermore, extensive and controlled proteolysis assays on wild-type and NH2-terminally modified beta subunits revealed a K(+)-dependent interaction of the cytoplasmic NH2 terminus of the beta subunit with the alpha subunit, which is likely to be involved in the modulation of the K(+)-activation of the Na,K-pump transport activity. Thus, we conclude that the ER assembly process not only establishes the basic structural interactions between individual subunits, which are required for the maturation of oligomeric proteins, but also distinct, functional interactions, which are involved in the regulation of functional properties of mature proteins.

Amino Acid Sequence↗
PubMed1996

Arterial complications of pancreatitis and their radiological management.

Arterial haemorrhage from pseudoaneurysm in pancreatitis patients is a formidable complication with a high mortality rate. We encountered six patients in whom a pseudoaneurysm was demonstrated at angiography. Drainage of associated pseudocyst facilitated visualization in one patient. Four patients had pseudoaneurysms arising from the proximal part of the major peripancreatic vessels and were treated by steel coil embolization (n = 3) and surgically (n = 1). There was no episode of rebleeding in these patients during a follow-up period of 10-18 months. Of the two patients with distal small peripancreatic branch vessel involvement hydrogel particle and gelfoam embolization was successful only temporarily in one patient and unsuccessful in the other patient. The literature is reviewed and the efficacy of steel coil embolization is emphasized.

Adolescent↗
PubMed1996

Vitiligo, psoralen, and melanogenesis: some observations and understanding.

Since the etiology of vitiligo is still unknown, we searched for some abnormal biochemical parameters, if any, in subjects with vitiligo. Higher urinary excretion of indole metabolites in vitiliginous patients have been noted, in association with higher dioxygenase, superoxide dismutase, and tyrosine aminotransferase activity in their serum. Similar results have also been found in an animal model, Bufo melanostictus, during induced tyrosinase inhibition. Treatment with psoralen can reverse the parameters, except tyrosine aminotransferase, to a normal level. Although psoralens are not the magic bullet for the therapy of vitiligo, they are still being used as a chemotherapeutic agent against vitiligo on a major scale to date. Tryptophan was found to participate in the pathway of melanogenesis, as a precursor as well as a positive regulator of tyrosinase. Its behavior in this regard is much more similar to the conventional substrates tyrosine and dopa (dihydroxyphenylalanine). In consideration of combined participation of tyrosine and tryptophan in the synthesis of melanin and its breakdown, the possible influence of different enzymatic reactions, like mono-oxygenase, dioxygenase, and deamination, has been suggested.

Animals↗
PubMed1996

Pulmonary capillary blood volume in patients with probable pulmonary Kaposi's sarcoma.

BACKGROUND: An increase in pulmonary capillary blood volume secondary to angiogenesis has been described in Kaposi's sarcoma. The value of the pulmonary capillary blood volume as an early marker of pulmonary Kaposi's sarcoma was evaluated. METHODS: In a prospective study 45 HIV positive patients (nine asymptomatic for Kaposi's sarcoma, 29 with cutaneous or mucocutaneous Kaposi's sarcoma, and seven with pulmonary Kaposi's sarcoma), underwent pulmonary function tests and determination of transfer capacity for carbon monoxide (TLCO) with its components, pulmonary capillary volume and membrane factor. RESULTS: Total lung capacity (TLC), TLCO, and its components were similar in the three groups. TLCO was normal in patients with pulmonary Kaposi's sarcoma and no changes in membrane factor or pulmonary capillary volume were observed. CONCLUSION: Pulmonary function tests and pulmonary capillary volume alone are not useful for identifying patients with pulmonary Kaposi's sarcoma.

Adult↗
PubMed1996

Transcriptional regulation and renal localization of 1,25-dihydroxyvitamin D3-24-hydroxylase gene expression: effects of the Hyp mutation and 1,25-dihydroxyvitamin D3.

X-Linked hypophosphatemic (HYP) mice respond to low phosphate (Pi) intake with a fall in the serum concentration of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] and an increase in the renal activity of 1,25-(OH)2D3-24-hydroxylase (24-hydroxylase), the first enzyme in the C-24 oxidation pathway that degrades 1,25-(OH)2D3 to its final inactivation product. In contrast, normal mice respond to a low Pi diet with an adaptive increase in serum 1,25-(OH)2D3 levels and no change in renal 24-hydroxylase. The low Pi response in Hyp mice involves a 3-fold increase in renal 24-hydroxylase maximum velocity and a corresponding increase in 24-hydroxylase immunoreactive protein and messenger RNA (mRNA). To determine the mechanism for the increase in 24-hydroxylase mRNA in the mutant strain, we examined the effect of actinomycin D on renal 24-hydroxylase mRNA abundance and measured renal 24-hydroxylase gene transcription by nuclear run-off assay in Hyp mice fed control and low Pi diets for 4 h. Vehicle and 1,25-(OH)2D3-treated normal mice were also studied 2-4 h post-treatment. Actinomycin D abrogated the increase in renal 24-hydroxylase mRNA elicited by a low Pi diet in Hyp mice and by 1,25-(OH)2D3 in both normal and Hyp mice. 24-Hydroxylase gene transcription, relative to that of glyceraldehyde-3-phosphate dehydrogenase, was increased 2-fold by feeding the low Pi diet to Hyp mice (n = 4; P < 0.05) and 5.4-fold by 1,25-(OH)2D3 administration to normal mice (n = 3; P < 0.01). In situ hybridization localized 24-hydroxylase transcripts to the proximal tubule of normal and mutant mice fed control and low Pi diets and showed that the 1,25(OH)2D3-induced increase in 24-hydroxylase mRNA occurred in the same nephron segment. The present study demonstrates that 1) transcriptional activation can account for the increase in renal 24-hydroxylase mRNA in Pi-deprived Hyp mice and for 24-hydroxylase mRNA induction by 1,25-(OH)2D3; and 2) the renal proximal tubule is the primary site of increased expression of 24-hydroxylase mRNA.

Animals↗
PubMed1996

ERECT WING, the Drosophila member of a family of DNA binding proteins is required in imaginal myoblasts for flight muscle development.

The erect wing locus of the fruit fly Drosophila melanogaster encodes a protein, EWG, that shares extensive homology with the P3A2 DNA binding protein of sea urchin and a recently identified mammalian transcription factor. Loss-of-function erect wing alleles result in embryonic lethality. Viable alleles of erect wing cause severe abnormalities of the indirect flight muscles. We have analyzed the spatial pattern of erect wing expression in the developing indirect flight muscles during postembryonic development. EWG is detected, 10 hours after puparium formation, in myoblasts that will form the indirect flight muscles. The early events of muscle development are normal in ewg mutants. However, a few hours after the onset of erect wing expression in myoblasts, defects are seen in the developing indirect flight muscles which subsequently degenerate. We present results that show that the normal development of the indirect flight muscles requires erect wing expression in the progenitor myoblasts themselves. Finally, we examine the role of target muscles in the arborization of motor axons by studying the developing innervation to the flight muscle in erect wing mutants. Our study demonstrates, for the first time, a role for a regulatory gene expressed in imaginal myoblasts in Drosophila.

Animals↗
PubMed1996

Myoelectric and mechanical manifestations of muscle fatigue in voluntary contractions.

Endurance is a clinically relevant muscle parameter. It would be desirable to be able to estimate it without the need for a contraction sustained to exhaustion. The purpose of this work was to investigate the capability of the initial rate of spectral compression of the surface electromyographic (EMG) signal to predict mechanical endurance during sustained voluntary contractions of the human tibialis anterior muscle. Six healthy subjects performed voluntary isometric contractions of the tibialis anterior at 80, 70, 60, and 50% of the maximal voluntary contraction level. The contractions were sustained for 90, 120, 150, and 170 seconds, respectively. These intervals exceed the normal endurance time for this muscle and allow for a decrease of torque output. The slope of the median frequency, computed over the first 30 seconds of the contraction, was used to describe the initial spectral compression of the EMG signal. Significant correlations were found: 1) between contraction level and endurance time (p < 0.05 for each subject) and 2) between median (or mean) frequency slope and endurance time (p < 0.0001 for all subjects pooled together). The regression between median frequency slope and endurance time showed intersubject variations possibly related to the tibialis anterior muscle fiber type content. It is concluded that clinical use of the EMG spectral technique in assessing muscle fatigue may enable the clinician to estimate the endurance time without having the subject sustain a contraction until the point of contractile failure. This could be an advantage for some patient populations, such as the severely disabled, arthritic, or frail elderly, that might not be able to tolerate long duration contractions.

Adult↗
PubMed1996

Proteinuria.

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Adolescent↗
PubMed1996

Hematuria.

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Adolescent↗
PubMed1996

Fibronectin overexpression in retinal microvessels of patients with diabetes.

PURPOSE: To examine whether fibronectin is synthesized in the adult human retina and whether diabetes alters its amount, level of expression, and pattern of splicing. METHODS: Retinas were obtained after death from 24 patients (age, 64 +/- 6 years) with 8 +/- 5 years of diabetes and 24 age-matched control subjects. Retinal localization of fibronectin and its amount in retinal vessels were examined with the immunoperoxidase technique. Fibronectin mRNA in the total retina was studied with reverse transcriptase-polymerase chain reaction using primers encompassing the alternatively spliced exon ED-A. The levels of fibronectin mRNA were measured relative to an internal standard (beta-actin mRNA). To detect and measure fibronectin expression in microvessels, retinal trypsin digests were studied by in situ hybridization. RESULTS: In the adult human retina, fibronectin is present exclusively in the walls of the vessels, including capillaries, and in the internal limiting membrane. In diabetic vessels, immunoreactive fibronectin was increased 1.4-fold over levels in control vessels (P = 0.05). Fibronectin is synthesized locally, and the predominant mRNA species excludes the ED-A region. The splicing pattern was not altered by diabetes. However, in the retinas of patients with diabetes, the levels of fibronectin mRNA were increased 1.3-fold over levels in control retinas (P = 0.028), whereas actin mRNA levels were similar in the two groups. Levels of fibronectin mRNA showed a substantial increase in the microvessels of patients with diabetes (0.49 +/- 0.18 grains/cell versus 0.15 +/- 0.12 grains/cell in control microvessels; P = 0.009. CONCLUSIONS: Fibronectin is synthesized in the adult human retina. Diabetes increases the amount of fibronectin in retinal vessels and upregulates its expression without changing the splicing pattern of the ED-A segment. Increased synthesis and deposition of fibronectin by microvascular cells may modify the interactions of cells and matrix with functional consequences relevant to the lesions of retinopathy.

Aged↗
PubMed1996

Expression of cell cycle-associated proteins in human and rabbit corneal endothelium in situ.

PURPOSE: It is unknown why human corneal endothelium exhibits limited capacity to divide while the endothelia of other species, such as rabbit, divide in vivo at wounding and in culture. A potentially valuable source of information concerning why human endothelium has such a limited proliferative capacity lies in elucidating any differences in the molecular events governing the cell cycle of these two species. A recent study of the relative expression of cell cycle-associated proteins in donor corneas suggests that human corneal endothelial cells in vivo have not exited the cell cycle but are arrested in G1-phase. The purpose of the current study was to identify differences in cell cycle protein expression in human and rabbit endothelium that would explain the difference in their relative proliferative capacities. Specifically, the authors first ascertained the relative proliferative status of rabbit corneal endothelial cells in vivo. The expression and intracellular distribution of G1-phase regulatory proteins was then determined in both species, and the results were compared. METHODS: Corneas from New Zealand white rabbits (weight range, 2 to 3 kg) and from human donors (age range, 6 months to 67 years) were fresh frozen, cryostat sectioned, and prepared for indirect immunofluorescence microscopy using an established protocol. The following monoclonal antibodies were localized in rabbit corneal endothelium only: cyclins D, E, A, and B1; protein kinase p34cdc2; and Ki67, a marker of actively cycling cells. Localization patterns for the following G1-phase regulatory proteins were compared in both human and rabbit corneal endothelia: the tumor suppressors, pRb, p53, and p16INK4, and the transcription factor, E2F. Reverse transcription-polymerase chain reaction studies were conducted to detect mRNA for Ki67 in human and rabbit corneal cells. RESULTS: Cyclins D, E, and A were localized in the cytoplasm of rabbit corneal endothelium, whereas cyclins B1 and p34cdc2 were detected in the nucleus. No Ki67 protein or mRNA expression was detected in the endothelium of either species. In human and rabbit endothelia, p53 and p16INK4 were localized to the cytoplasm, whereas pRb was detected in the nucleus. E2F exhibited a nuclear and a cytoplasmic localization in each species. CONCLUSIONS: The corneal endothelium of rabbits stained positively for cyclins D, E, and A and did not stain for Ki67, suggesting that, as in humans, rabbit corneal endothelium in vivo is arrested in G1-phase upstream from Ki67 synthesis. Cyclin E was located in the cytoplasm of rabbit cells, whereas it was found in the nucleus in human endothelium. The apparent difference in cellular distribution of cyclin E in these two species may be significant because this cyclin is active during the G1-/S-phase transition. It is possible that in situ human and rabbit corneal endothelial cells are arrested at different points within G1-phase and/or that the difference in relative proliferative capacity exhibited by the corneal endothelium in these two species may be caused by differences in their relative ability to overcome G1-phase arrest.

Adolescent↗
PubMed1996

Do we need anti snake venom (ASV) for management of elapid ophitoxaemia.

Twelve patients of elapid ophitoxaemia presented with neuromuscular paralytic features were given anticholinesterase (Neostigmine) in recommended dosage. In four of these patients, despite neuromuscular paralysis, no ASV was used. All these four patients survived. In eight patients, ASV was used; in three of whom it used in doses less than 50 units, yet patients survived. Of the remaining five, despite use of ASV in higher doses (more than 50 units), two succumbed to death. Eight patients required ventilatory support. Hence, in absence of any definite role of ASV in management of elapid ophitoxaemia (snake bite), use of anticholinesterase drugs alone, with good supportive care and prevention of likely complications, can result in satisfactory outcome.

Adolescent↗
PubMed1996

Eye changes in non-specific aorto-arteritis.

Non-specific aorto-arteritis or Takayasu's arteritis is fairly common and has been reported from all parts of India. The disease presents with various eye symptoms such as transient or permanent blindness, headache and signs including neovascularisation, retinal anastomosis, rubeosis iridis, cataracts. Eye manifestations depend on stage of disease and degree of involvement of cervical arteries. This review consists of an indepth impression of eye involvement in non-specific aorto-arteritis.

Eye Diseases↗
PubMed1996

A comparative study of the efficacy and safety of synthetic prostaglandin E2 derivative and 15-methyl prostaglandin F2 alpha in the termination of midtrimester pregnancy.

A comparative study of a synthetic prostaglandin E2 (PGE2) derivative and 15-methyl prostaglandin F2 alpha (PGF2 alpha) in the termination of midtrimester pregnancy of 13-20 weeks of gestation by intramuscular route, showed 97.5% success rate in both the groups but in comparison to 15-methyl PGF2 alpha which produced severe side-effects eg. diarrhoea and vomiting, synthetic PGE2 derivative had minimal or no side-effects.

Abortifacient Agents, Nonsteroidal↗