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Biomedical subjects

S Mehta

Publications and source records attributed to S Mehta.

At least 181 records · Page 10Linked to original sources
PubMed1996

Radial nerve entrapment.

The radial nerve is frequently more involved in entrapment syndromes than the ulnar and median nerves. Common sites of compression are the juncture of the middle and distal third of the arm (especially with fractures of the humerus), just distal to the elbow (radial tunnel), and proximal to the wrist between the brachioradialis and extensor carpi radialis longus. Often in entrapment syndromes involving the radial nerve, the true diagnosis is not evident and is arrived at only by exclusion, which sometimes delays initiation of effective treatment. Radial tunnel syndrome is rare, but decompression when indicated, can provide relief. Radial sensory nerve entrapment in the forearm (distal third) does occur, but patients often respond to temporary thumb spica splinting.

Adult↗
PubMed1996

Nonionizing electromagnetic fields and cancer: a review.

Low-frequency electromagnetic radiation had previously been thought to cause human injury only by generation of excess heat or by shock from direct contact with electric current. Information accumulating over the past few decades, however, suggests that nonionizing electric and magnetic fields associated with this radiation may be an environmental etiology in human disease. Human beings are affected not only by natural background nonionizing electromagnetic fields produced by the Earth, but also by a host of manmade sources. Of the diseases believed related to these fields, cancer and participation of these fields in the carcinogenic process have received considerable attention. This paper is a review of the basic science that points to this possible association.

Animals↗
PubMed1996

Rhabdomyosarcoma of head and neck--an analysis of 24 cases.

Clinical records of 24 cases or rhabdomyosarcoma involving head and neck region were studied. Majority of the patients (83.3%) were under five years of age. The common sites of involvement were the middle ear (50%) and the nasopharynx (17%). Embryonal variety was noted in majority of patients (83.3%). Pain and swelling in the post aural or pre-auricular region was the commonest mode of presentation. Last four cranial nerves were involved in eight patients and four patients had extension of the tumor in the posterior cranial fossa. Twenty patients having embryonal rhabdomyosarcoma received combination of chemotherapy and radiotherapy. Half of these remained tumor free upto six months. Surgical extirpation was done only in two patients, where the disease was localised. The tumor in these two patients was of pleomorphic variety and did not recur till two years after surgery.

Adolescent↗
PubMed1996

Noninvasive ventilation in acute respiratory failure.

Noninvasive PPV has been employed for decades in patients with chronic respiratory failure. Increasing use in patients with acute respiratory failure is a more recent phenomenon, mainly because of advances in noninvasive interfaces and ventilator modes. Noninvasive PPV delivered by nasal or oronasal mask has been demonstrated to reduce the need for endotracheal intubation, decrease lengths of stay in the ICU and hospital, and possibly reduce mortality. In the acute care setting, evidence now demonstrates the efficacy of noninvasive PPV for acute exacerbations of COPD, pulmonary edema, pulmonary contusions, and acute respiratory failure in patients who decline or who are not believed to be candidates for intubation. No firm conclusions can yet be made regarding patients with respiratory failure due to other causes, but studies suggest that noninvasive PPV may also be of benefit in patients with postoperative respiratory insufficiency, chest wall disease, and cystic fibrosis. Several factors are vital to the success of this therapy, including careful patient selection, properly timed intervention, a comfortable, well-fitting interface, patient coaching and encouragement, and careful monitoring. Noninvasive ventilation should be used as a way to avoid endotracheal intubation rather than as an alternative. Accordingly, a trial of noninvasive ventilation should be instituted in the course of acute respiratory failure before respiratory arrest is imminent, to provide ventilatory assistance while the factors responsible for the respiratory failure are aggressively treated. Moreover, the authors favor conservative management with expeditious intubation in patients who have other conditions that place them at risk during use of noninvasive ventilation or in patients failing to respond to noninvasive PPV. Noninvasive PPV clearly represents an important addition to the techniques available to manage patients with acute respiratory failure; however, because most studies have been retrospective and uncontrolled, many issues remain unresolved. Further controlled studies are needed to confirm the safety and efficacy of noninvasive PPV, evaluate the most appropriate selection of patients and timing of intervention, define the best type of interface, and assess the costs of noninvasive PPV in comparison with conventional therapy.

Acute Disease↗
PubMed1995

Short-term pulmonary vasodilation with L-arginine in pulmonary hypertension.

BACKGROUND: Endothelial dysfunction may contribute to the pathogenesis of pulmonary hypertension through impaired production of the endothelium-derived vasodilator nitric oxide (NO). L-Arginine, the substrate for NO synthase (NOS), has a vasodilatory effect in systemic vascular beds and can correct abnormal endothelium-dependent vasodilation. It has been suggested that these two effects of L-arginine are mediated through NOS metabolism and enhanced NO production. Therefore, we assessed the short-term pulmonary hemodynamic effects of exogenous L-arginine in patients with pulmonary hypertension of various origins. METHODS AND RESULTS: During continuous hemodynamic monitoring, 10 subjects with pulmonary hypertension (mean pulmonary artery pressure [PAP], 54 +/- 5 mm Hg [mean +/- SEM]) received a 30-minute control infusion of hypertonic saline followed by a 30-minute infusion of 500 mg/kg of L-arginine. The hemodynamic effects of L-arginine were compared with those of prostacyclin titrated to maximally tolerated doses. The hemodynamic response to L-arginine was also studied in 5 subjects with heart failure but without pulmonary hypertension (mean PAP, 20 +/- 2 mm Hg) and 5 healthy control subjects. In subjects with pulmonary hypertension, infusion of L-arginine reduced mean PAP by 15.8 +/- 3.6% (P < .005) and pulmonary vascular resistance (PVR) by 27.6 +/- 5.8% (P < .005) compared with decreases of 13.0 +/- 5.5% (P < .005) and 46.6 +/- 6.2% (P < .005), respectively, with prostacyclin. L-Arginine infusion also increased the mean plasma level of L-arginine from 59 +/- 6 mumol/L to 10,726 +/- 868 mumol/L (P < .005), which was associated with a significant increase in the plasma level of L-citrulline, the immediate product of NOS metabolism of L-arginine. Moreover, the peak plasma level of L-citrulline correlated significantly with the reductions in mean PAP (r = .71, P < .05) and PVR (r = .70, P < .05), consistent with vasodilation mediated by NOS metabolism of exogenous L-arginine and increased NO production. L-Arginine also had a modest hypotensive effect in healthy control subjects and reduced systemic vascular resistance in subjects with heart failure in the absence of pulmonary hypertension. However, only small reductions in absolute pulmonary vascular resistance were observed in this latter group in response to L-arginine that did not reach significance. CONCLUSIONS: An exaggerated short-term pulmonary vasodilatory response to L-arginine in patients with pulmonary hypertension suggests a relative impairment in pulmonary vascular endothelial NO production that may contribute to increased pulmonary vascular tone and thus be important in the pathophysiology of pulmonary hypertension.

Adult↗
PubMed1995

Results of conversion from triple-drug to double-drug therapy in living related renal transplantation.

Results of 34 recipients of living related renal allografts initially treated with cyclosporine, azathioprine, and prednisolone and later electively converted to AZA and PRED are presented. Thirteen (group A), 14 (group B), and 7 (group C) patients were converted before 9 months, between 9 and 12 months, and after 12 months, respectively. Thirty-four patients who were on AZA and PRED and had never received CsA served as controls. Of the 34 patients, 33 were HLA haploidentical with their donors and 1 was HLA identical. All patients received a mean 8.62 +/- 7.39 third-party blood transfusions. In the control group, 29 patients received haploidentical grafts. The number of blood transfusions given to this group was 7.09 +/- 9.13. Of the 34 patients receiving triple-drug therapy, 9 (26%) had acute rejection within 3 months after conversion, as compared with 5 (14.7%) in the control group (P > 0.05). Although 1 case had acute rejection before conversion, all recipients had stable graft function at the time of conversion. Of these 9 recipients, 7 had conversion over 4-7 weeks, while 2 had rapid conversion. Following treatment of the rejection episodes, 4 patients in the study group responded to therapy, as compared with 3 cases in the control group (P > 0.05). After a mean follow-up of 18.62 +/- 10.31 months (range 3-41 months) following conversion, 4 patients were normal, 4 had chronic rejection (mean serum creatinine = 3.0 mg/100 ml), and 1 was back on regular dialysis. Eventually, of the 34 patients who were converted from triple-drug to double-drug therapy, 25 were normal, 5 had stable chronic rejection, 2 were back on regular dialysis, 1 was retransplanted, and 1 died due to failed graft. At the end of follow-up, graft survival in the study group was 88.2%, as compared with 85.5% in controls (P > 0.05). We conclude that conversion from triple-drug to double-drug therapy is not without risk, even in living related primary renal transplantation. Degree of HLA matching, number of pretransplant blood transfusions, and rejection before conversion did not have any significant effect on rejections following conversion, and the graft loss following conversion is unpredictable.

Adolescent↗
PubMed1995

Effects of high levels of fluoride on bone formation: an in vitro model system.

In order to develop an in vitro model for the study of the effects of different agents on biomineralization, a three-dimensional cell culture system was investigated at different levels of fluoride. Rat fetal osteoblasts were seeded onto collagen discs and maintained in a culture medium for 40 days. Results showed that, at 40 days, the cultured matrices had a Ca:P ratio, mineral content and Fourier transform infrared (FTIR) spectrum that were close to those seen for normal rat bone. Viable cells, observed by light microscopy, were present in the matrix at 40 days. The formation of a mineralized matrix in this experimental set-up provided a model for exploring in vitro the effects of high levels of fluoride on bone. The fluoride content of the mineral formed in the cultures showed a dose-dependent increase in fluoride content with time. Also, an increase in the crystallinity of the apatite in the presence of fluoride, was observed by FTIR. The Ca:P ratio and percentage mineral by weight showed no apparent differences among the groups. The three-dimensional model used for this study has the potential to be a powerful tool in the study of time-dependent effects of drugs and other factors on osteoblast cell functions and subsequently on matrix mineralization.

Animals↗
PubMed1995

Hepatic involvement culminating in cirrhosis in a child with disseminated cryptococcosis.

A 7-year-old child had unusual manifestation of cryptococcosis; liver and lymph node involvement predominated. There was evidence of cryptococcal hepatitis, extrahepatic biliary obstruction, and subsequent cirrhosis of the liver. Despite widespread dissemination, underlying immune disturbance was not evident. The patient was treated with two courses of amphotericin and 5-flucytosine.

Amphotericin B↗
PubMed1995

Urinary tract obstruction and nephrostomy drainage in pelvic malignant disease.

OBJECTIVE: To determine the survival of patients after percutaneous nephrostomy drainage (PND) for obstructive uropathy secondary to pelvic malignant disease. PATIENTS AND METHODS: The records of 77 patients undergoing PND for obstructive uropathy were reviewed. Patients were classified according to the nature of the obstructing lesion: Group I (primary untreated malignancy, 31 patients); Group II (recurrent malignancy with further treatment, 15 patients); Group III (recurrent malignancy with no further treatment, 12 patients); and Group IV (benign disease as a consequence of previous treatment, 19 patients). Outcome was assessed by survival over a mean follow-up of 20 months (range 2 days-8.3 years). RESULTS: Overall median survival was 26 weeks, with a 5-year survival of 22%. The survival in Groups I and II was not significantly different (median survival 27 and 20 weeks, respectively; 5-year survival, 10% and 20%, respectively). Group III patients had a poor prognosis (median survival 6.5 weeks) with no patient surviving beyond one year, whilst Group IV patients fared best with a 5-year survival of 64%. The commonest primary tumour type was carcinoma of the cervix (42 patients), and these patients were analysed as a subset. Benign post-radiation fibrosis was found in 16 of 27 patients (59%). Survival was related to the diagnostic group. CONCLUSION: The nature and extent of the obstructing lesion and its potential for further treatment are the major determinants of post-nephrostomy survival. Every effort should therefore be made to identify the nature of the obstruction before deciding on PND.

Adult↗
PubMed1995

Hemileaflet susceptibility to oxidative damage in the intestinal brush-border membrane.

Oxidation of biological membranes is characteristic of many types of tissue injury, including those observed with inflammatory bowel disease. The lipid compositions of the inner and outer leaflets of biological membranes differ significantly, making one leaflet theoretically more susceptible to oxidative stress than the other. In this study, we evaluated the susceptibility of each membrane hemileaflet for peroxyl radical-mediated oxidation. In vitro peroxidation of intestinal brush-border membrane was initiated with the peroxyl radical-generator 2,2'-azobis-(2-amidinopropane)hydrochloric acid (AAPH). Oxidation events were monitored by following the oxidation-sensitive degradation of the lipid-soluble fluorescent probe cis-parinaric acid (PnA). The degradation patterns were clearly distinct in the inner and outer hemileaflet. PnA degradation in the inner hemileaflet was consistent with a slow first-order reaction, whereas degradation in the outer leaflet appeared as two first-order processes delayed in time. The results suggest that the sum of available antioxidants and endogenous substrates for oxidation are consumed more rapidly in the outer membrane hemileaflet, making this leaflet more susceptible to peroxidation compared with the cytofacial leaflet.

Amidines↗
PubMed1995

Effect of peptide YY on human renal function.

Peptide YY (PYY) is released from the intestine into the circulation in response to ingestion of food. As PYY/neuropeptide Y (NPY) receptors have recently been identified in the human kidney, we examined the effect of PYY on human renal function. Male subjects (6 per group) received control infusate or PYY at 0.4 or 1.2 pmol.kg-1.min-1 intravenously for 90 min with control periods before and after. Infusion of PYY at the lower dose reproduced normal postprandial plasma concentrations and caused significant decreases in glomerular filtration rate (10% reduction), plasma renin activity (30% reduction), and aldosterone levels while increasing sodium excretion by approximately 30% (all P < 0.01). Infusion of PYY at the higher dose, which reproduced plasma levels seen during a diarrheal illness, resulted in similar changes in renal function and also reduced renal plasma flow by approximately 10% (P < 0.05). Therefore, PYY may be an important mediator of the normal postprandial natriuretic response, and PYY agonists could provide a novel approach to the treatment of patients with sodium overload.

Adult↗
PubMed1995

Effects of physical conditioning on endogenous nitric oxide output during exercise.

Nitric oxide (NO) has been detected in the expiratory air of normal animals and human subjects. Recent experiments revealed that expiratory NO production rises during exercise and correlates well with O2 consumption (VO2) and heart rate. Whether physical conditioning influences expiratory NO output production remains unclear. In this study, NO concentration in expired gas was measured in 18 healthy male volunteers subdivided into three groups (sedentary, intermediate, and athletic) on the basis of the subjects' state of physical conditioning. Measurements were taken at rest and during two steady-state exercise bouts on a bicycle ergometer designed to elicit VO2 of 1 and 2 l/min with the athletes performing an additional bout at VO2 of 4 l/min. In the sedentary and intermediate groups, expired NO concentrations declined significantly with increasing VO2. In contrast, expired NO levels declined only slightly with increasing VO2 in the athletes. At a VO2 of 2 l/min, expired NO concentrations were significantly higher in the athletes compared with values in the other groups. When correlated with minute ventilation (VE), expired NO concentrations declined linearly with the increase in VE in sedentary and intermediate groups but not in the athletes. Only the athletes had a significant linear increase in NO output (expired NO x VE) with increasing VO2 (P < 0.001). These results support the notion that physical conditioning increases expiratory NO output during exercise. We speculate that the rise in expiratory NO output in the athletes might be due to increased vascular and/or epithelial production of NO. Enhanced vascular NO production may be the result of increased shear stress and/or upregulation of endothelial NO synthase gene expression.

Adult↗
PubMed1995

Sigmoido-rectal intussusception.

Sigmoido-rectal intussusception is the least common type of intussusception seen in infants and children and is therefore usually misdiagnosed as rectal prolapse. Delay in diagnosis and treatment is due to lack of its awareness amongst surgeons, incomplete assessment of the prolapsed bowel at the anal orifice, and absence of classical traid of intussusception i.e. palpable abdominal mass, colicky abdominal pain, and bleeding per rectum.

Child↗
PubMed1994

Effect of protein energy malnutrition on the lipid composition and leucine uptake of small intestinal brush border vesicles of growing rhesus monkeys.

Mild to moderate protein energy malnutrition (PEM) was induced in young developing rhesus monkeys by giving them half of the casein-based synthetic diet which was given to control animals. After a body weight reduction of 30-40%, the PEM animals were sacrificed. The small intestine was removed, flushed with ice-cold saline, everted and divided into equal proximal, middle and distal segments. Brush border membrane vesicles (BBMV) were prepared from all three segments and assayed for marker enzymes, e.g. sucrase and alkaline phosphatase, to assess their purity. Sucrase was found to be purified 23-fold and alkaline phosphatase 12-fold compared to the respective homogenates in all three parts. In PEM animals, uptake of [U-14C]L-leucine into the BBMV was diminished in all three segments and cholesterol and phospholipid levels also decreased significantly. As a result there was an elevation in the molar ratio of cholesterol to phospholipid, and the sphingomyelin: phosphatidylcholine molar ratio also increased. This signified a decrease in lipid fluidity and amino acid uptake in PEM in the small intestine. Histologically, a mild to moderate grade of partial villus atrophy was observed in the intestine. The diminished uptake and lipid fluidity of the membrane and the histological changes returned to their control values after nutritional rehabilitation.

Alkaline Phosphatase↗
PubMed1994

Voda guiding catheter is superior to amplatz guiding catheter for performing left circumflex PTCA.

Amplatz guiding catheters have traditionally been recommended for performing Left Circumflex PTCA because of their enhanced support. The Voda (Scimed Inc.) design guiding catheter may provide similar support for the left coronary artery, particularly the left circumflex, with less catheter manipulation. We prospectively randomized 40 patients to either Amplatz or Voda guiding catheters to compare ease of use and observed that a Voda design guiding catheter has more favorable characteristics for use without sacrificing support.

Aged↗