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Biomedical subjects

N Sheth

Publications and source records attributed to N Sheth.

10 recordsLinked to original sources
PubMed1999

A comparison of various angles of halo pin insertion in an immature skull model.

STUDY DESIGN: A basic science biomechanical study involving an animal model. OBJECTIVES: To evaluate the effect of varying angles of halo pin insertion on the force generated at the pin-bone interface, and thereby the stability of the halo pin-bone interaction during insertion. BACKGROUND DATA: Because of variations in the shape and size of the pediatric skull, halo pins often are inserted at various angles rather than perpendicular to the skull. Concern exists that the high complication rate associated with pediatric halo use may result in part from less than ideal structural properties at the halo pin-bone interface. METHODS: The authors used a fetal calf skull model to simulate the thickness and structural properties of the pediatric skull. Halo pins were inserted at angles of 0 degree (perpendicular), 10 degrees, 15 degrees, and 30 degrees into skull segments via a halo ring. Load generated at the pin-bone interface was measured using a modified mechanical testing device. Twenty trials were conducted per angle, with the endpoint being specimen failure, pin penetration, or maximum load. RESULTS: Mean maximum loads per unit thickness were 82.15 +/- 7.54 N/mm at 0 degree, 68.80 +/- 4.79 N/mm at 10 degrees, 51.49 +/- 5.08 N/mm at 15 degrees, and 42.38 +/- 3.51 N/mm at 30 degrees, There was a significant difference between perpendicular insertion (0 degree) and 15 degrees angles of insertion. There was also a significant difference between the 10 degrees and 30 degrees angles of insertion. CONCLUSIONS: Perpendicular halo pin insertion in an immature skull model was shown to result in increased load at the pin-bone interface. This improved structural behavior may help to reduce the incidence of complications of halo application in children.

Animals↗
PubMed1998

The role of adjunctive mitomycin C in secondary glaucoma triple procedure as compared to primary glaucoma triple procedure.

OBJECTIVE: This study aimed to investigate whether previously failed glaucoma filtration surgery is a risk factor for filtration failure of subsequent trabeculectomy combined with cataract surgery and to determine the role of adjunctive mitomycin C (MMC) in the secondary glaucoma triple procedure (SGTP) as compared to primary glaucoma triple procedure (PGTP). DESIGN: A prospective, controlled study that was randomized with respect to assignment to adjunctive MMC and a case-control design with respect to comparisons between SGTP and PGTP was studied. PARTICIPANTS: The SGTP group consisted of 49 eyes of 49 consecutive patients with primary open-angle glaucoma with a history of glaucoma filtration surgery requiring glaucoma medical therapy and in need of cataract surgery, randomized to adjunctive MMC (SGTP MMC subgroup of 21 eyes) and no adjunctive MMC (SGTP control subgroup of 28 eyes). The PGTP group consisted of 49 PGTP cases closely matched to the SGTP cases with respect to age, race, gender, MMC use, C:D ratio, and systemic diseases. INTERVENTION: Trabeculectomy combined with phacoemulsification and a small incision (5 x 6 mm), all polymethylmethacrylate posterior chamber intraocular lens implantation with or without adjunctive MMC (0.5 mg/ml for 1 minute), was performed. MAIN OUTCOME MEASURES: Surgery failure was defined as the need of an additional intraocular procedure or the need of more than one medication to achieve intraocular pressure control to the target level. Intragroup and intergroup comparisons were made with respect to filtration outcome among the SGTP and PGTP patients. RESULTS: Without adjunctive MMC, filtration success was significantly less in SGTP than in PGTP (P = 0.03). Adjunctive MMC significantly increased the success rate of SGTP (P = 0.02) but not that of PGTP (P = 0.89) over the average follow-up period of 2 years. CONCLUSIONS: Previously failed glaucoma filtration surgery is a significant risk factor for the filtration failure of combined surgery. Intraoperative use of adjunctive MMC significantly improves the filtration success rate of SGTP.

Adult↗
PubMed1991

Halothane alters control of intracellular Ca2+ mobilization in single rat ventricular myocytes.

In an attempt to understand the cellular mechanisms underlying volatile anesthetic-induced myocardial depression, halothane-induced negative inotropy was investigated in an animal model through continuous monitoring of intracellular Ca2+ concentration [( Ca2+]i) in rat ventricular myocytes loaded with fura-2. Single cells were stimulated with 15 mM caffeine or 15 mM extracellular K+ (K+O) or were paced by extracellular glass suction pipette electrode. With each stimulus modality, halothane (0.6-1.5%) caused a significant (P less than 0.05) and dose-dependent depression of the Ca2+ transient. Caffeine and electrically stimulated Ca2+ transients were reduced, in 1.5% halothane, to 35 +/- 14 and 42 +/- 8% of control, respectively. Resting or basal [Ca2+]i was unaffected by halothane. Halothane did not elicit spontaneous Ca2+ transients in these cells. Single cells stimulated by trains of electrical stimuli at 1.0, 1.5, and 2.0 Hz showed a change in [Ca2+]i from prestimulus levels to a stimulated baseline steady state that appeared to increase with stimulus frequency. Halothane at 0.7% increased the change in resting to stimulated baseline [Ca2+]i and depressed net transients (P less than 0.05) at 1.0 and 1.5 Hz. In contrast, 0.1 microM ryanodine depressed the Ca2+ transients in myocytes stimulated by trains of stimuli, but did not potentiate the change in stimulated baseline [Ca2+]i at any pacing rate. The results are consistent with the hypothesis that halothane reduces Ca2+i availability by causing a net loss of Ca2+ from the sarcoplasmic reticulum. The results from experiments using onset of pacing to induce a sudden increase in Ca2+i load in previously quiescent myocytes suggest that halothane may act to limit sarcoplasmic reticulum and/or sarcolemmal uptake/extrusion mechanisms, as compared to ryanodine, which depletes sarcoplasmic reticulum Ca2+ stores without affecting reuptake and extrusion.

Animals↗
PubMed1990

Increased concentration of prostatic inhibin following orchidectomy in rat.

Inhibin, a predominant secretory protein of prostate has been shown earlier to increase in proliferative prostatic diseases. Since the prostate gland is under the profound influence of androgens, it's withdrawal by orchidectomy is many a time included in the therapy to prostate cancer. Hence it was interesting to study the reflection of long term orchidectomy on prostatic inhibin. With this aim two groups of bilaterally orchidectomised male Sprague-Dawley rats were sacrificed 15 days and 30 days after castration respectively. Another group of rats was administered with testosterone enanthate after 30 days of castration. As protein concentration and weight showed a significant decrease after orchidectomy, inhibin concentrations (estimated by RIA) were expressed per gland. The inhibin concentration was increased to a 5-6 fold higher value after 15 days of castration. While a remarkable 10-15 fold elevation of inhibin concentration was observed in 30 day castrated prostates. Concurrently the circulating inhibin levels were also found to be heightened. All these effects of orchidectomy were almost reversed on androgen administration. Thus in contrast to the decrease in the weight and concentration of other prostatic proteins after orchidectomy, the increase in inhibin appears to be striking.

Animals↗
PubMed1989

Nutrient influences on rat intestinal phenytoin uptake.

The intestinal uptake of phenytoin was studied as a function of concentration, intestinal region, coperfused glucose, and calcium chloride in rat intestinal perfusions and everted intestinal rings. Steady-state intestinal membrane permeabilities were obtained in an in situ perfusion system and initial rates of intestinal tissue uptake were obtained in an in vitro everted ring system as rate of absorption parameters. Steady-state membrane permeabilities were independent of phenytoin perfusion concentration and decreased from duodenum to ileum. Coperfusion of glucose increased, and high calcium chloride concentrations decreased phenytoin permeabilities. While phenytoin uptake in the in vitro ring system was also concentration-independent and depressed by high calcium concentrations, regional variations and glucose enhancement were not observed. Thus, drug-nutrient interactions involved in intestinal absorption from phenytoin solutions are a function of the isolation procedure.

Animals↗
PubMed1988

Acyclovir in human breast milk.

Acyclovir concentration was measured by radioimmunoassay in the serum and milk of a lactating woman who was treated with oral acyclovir for herpes zoster. Daily serum and milk samples showing milk concentrations that averaged being 3.24-fold higher than serum levels suggest a low infant dose. The elimination phase demonstrated a half-life of 2.8 hours in milk.

Acyclovir↗
PubMed1985

Intestinal ischemia caused by cocaine ingestion: report of two cases.

Ingested cocaine can be a cause of severe bowel ischemia or gangrene. Two cocaine addicts who ingested large quantities of the drug developed severe abdominal symptoms and signs caused by bowel ischemia. In one patient gangrene of the bowel necessitated repeated resections and was followed, several weeks later, by death. The other patient suffered less severe ischemia and the bowel returned to normal. The diagnosis of bowel ischemia should be suspected whenever a cocaine addict has severe abdominal symptoms and signs. The presence of marked leukocytosis suggests bowel gangrene and demands prompt surgical intervention.

Adult↗
PubMed1985

Carcinoma of the pancreas in nonjaundiced patients. A silent disease.

This report deals with the study of 25 patients with carcinoma of the pancreas without jaundice. Carcinoma of the pancreas is the fourth most common cause of death among men who suffer from cancer. The extremely high mortality associated with pancreatic cancer is due to failure of early diagnosis. Those cases associated with obstructive jaundice can be diagnosed much earlier than those in which jaundice is absent. In the absence of jaundice, symptoms and signs of pancreatic cancer are so vague that they may be confused with those of other conditions. Routine laboratory tests aid little in the definitive diagnosis of the disease. Sophisticated new modalities of diagnosis such as ultrasonography, endoscopic retrograde cholangiopancreatography (ERCP), and CT-scanning frequently will lead to a correct diagnosis, but these tests are seldom performed unless there is a strong suspicion that carcinoma of the body of the pancreas exists. When pancreatic carcinoma without jaundice is ultimately diagnosed, it is found to be less amenable to surgery than lesions located in the head where early jaundice is more often encountered. Most patients with cancer of the body of the pancreas suffer from persistent unexplained abdominal pain, marked anorexia, and weight loss. Such patients must be subjected to sophisticated diagnostic tests in order to arrive at an early diagnosis.

Adenocarcinoma↗
PubMedDate not supplied

Phenytoin interaction with enteral feedings administered through nasogastric tubes.

Inadequate drug plasma levels have been associated with the administration of phenytoin with enteral feedings through nasogastric (NG) tubes. It is demonstrated in this study that loss of phenytoin to tubing is a function of pH. Nonionized phenytoin is irreversibly bound to NG tubing from solution at the pH of enteral nutrient solutions while this is not the case for anionic phenytoin in unbuffered water or saline. In experiments pulsing phenytoin through glass vs NG tubing perfused with buffer at varying pH, reversible loss to tubing was observed at high pH while irreversible loss was observed at low pH. In addition, the irreversible loss of phenytoin was greater in NG tubing than glass particularly at low pH. It is suggested that in those cases where tubing is placed into the duodenum, inadequate gastrointestinal residence time for dissolution of phenytoin solid and suspension dosage forms coupled with irreversible drug loss from solution to NG tubing will result in decreased phenytoin absorption and subsequently lower drug plasma levels.

Animals↗