Search PubMed⌕ Search

Biomedical subjects

D K Shah

Publications and source records attributed to D K Shah.

16 recordsLinked to original sources
PubMed2001

Neuroendocrine factors affecting the steady-state levels of early trypsin mRNA in Aedes aegypti.

Transcription of the early trypsin gene occurs in the midgut after adult emergence under control of juvenile hormone (JH). We tested the hypothesis that factors that affect the steady-state levels of early trypsin mRNA do so by influencing the levels of JH. We investigated the effect of ingesting different meals on early trypsin mRNA levels as well as on JH levels. We also studied how early trypsin mRNA levels changed when the midgut was isolated from different components of the neuroendocrine system by abdominal ligation and decapitation. Early trypsin transcripts levels are high in unfed females; feeding different meals had three distinct effects on the changes of steady-state levels of early trypsin mRNA: (1) blood and protein meals caused the level to decrease drastically and remained low for at least 24 h; (2) amino acid meals caused a transient decrease in the mRNA level, but it returned to high levels after 12-18 h; and (3) sugar, latex and saline meals had no effect on the early trypsin mRNA steady-state levels. The changes in JH levels after ingesting blood and amino acid meals show profiles resembling the changes in early trypsin mRNA levels for the corresponding meal. Decapitation at 1, 2 and 3 days after emergence does not affect the steady-state levels of early trypsin in unfed females. In contrast, 24 h after feeding, transcript levels were significantly higher in decapitated females when compared with non-decapitated fed females. We propose that the changes in the steady-state levels of early trypsin mRNA observed after the ingestion of different meals, ligations and decapitations are generated by changes in the levels of juvenile hormone.

Journal Article↗
PubMed1997

Juvenile hormone controls early trypsin gene transcription in the midgut of Aedes aegypti.

Early trypsin is a female-specific protease present in the Aedes aegypti midgut during the first few hours after ingestion of a blood meal. The enzymatic activity of early trypsin plays an essential role in the transcriptional activation of the late trypsin gene, which encodes the major midgut endoprotease involved in blood meal protein digestion. Transcription of the early trypsin gene is part of the normal post-emergence maturation of the midgut in the adult female. Abdominal ligation within 1 h of emergence completely prevented the transcription of the early trypsin gene. Topically applied JH III or methoprene induced transcription of the early trypsin gene in ligated abdomens to levels similar to those observed in non-ligated females. The induction of early trypsin transcription by JH is dose-dependent and 'head-independent', suggesting that factors coming from the neuro-secretory axis are not required.

Aedes↗
PubMed1997

Endolymphatic sac surgery in Meniere's disease.

Despite the controversy that surrounds sac surgery for Meniere's disease, it remains in the forefront of surgical intervention for the refractory patient. This article reviews the literature for all types of sac surgery, with emphasis on wide sac-vein decompression as performed at the Michigan Ear Institute.

Cerebrospinal Fluid Shunts↗
PubMed1996

Combination therapy for salvaging a failing, experimental skin flap.

The failing free flap remains a major problem for the reconstructive surgeon. Many and varied pharmacologic agents have been utilized to reverse the effects of ischemia in these flaps. Treatments have been aimed at inhibiting presumed causative factors in the no-reflow phenomenon. Therapy has generally been single in nature and designed to affect only one of these presumed factors. In this study, several pharmacologic agents were utilized individually or in combination therapy as postischemic washouts, in an effort to attack the multiple causative factors in the no-reflow phenomenon and to improve flap survival in a rat abdominal skin flap model. The treatment agents included lactated Ringer's, superoxide dismutase, and urokinase, with each used independently as a postischemic perfusion washout. Combination therapy utilized an initial postischemic perfusion with urokinase, followed by a second perfusion washout with superoxide dismutase. After 18 hr of primary ischemia, there was increased flap survival in the animals undergoing perfusion washout with either superoxide dismutase alone or with combined urokinase and superoxide dismutase washouts, compared to all other treatments (p < 0.001). It was found that flaps undergoing combined urokinase and superoxide dismutase postischemic perfusion washouts demonstrated significantly improved survival after 20 hr of primary ischemia, compared to all other therapies (p < 0.05). By demonstrating improved survival when a thrombolytic agent is used in conjunction with an oxygen free radical scavenger, these findings may have implications in the treatment of clinically failing free flaps.

Animals↗
PubMed1995

Evaluation of a continuous systemic infusion of iloprost, a stable PGI-2 analog, on the survival of experimental skin flaps.

Numerous investigators have attempted to enhance the survival of ischemic experimental skin flaps using various pharmacologic manipulations. Recently, the authors' laboratory demonstrated the beneficial effect of iloprost, a stable PGI2 analogue, as a post-ischemic perfusion washout, in improving the survival of ischemic skin flaps. The rat unilateral abdominal skin flap, based on the superficial epigastric vessels, was utilized in this study involving 30 animals. The animals were divided into three different treatment groups, with ischemic periods of 16 and 18 hr. Perfusion washouts were performed at the completion of the various ischemic periods. Alzet osmotic pumps were used to deliver a continuous systemic infusion of iloprost for 7 days postoperatively. The groups consisted of the following: Group 1 (single ILO)--perfusion washout with iloprost only; Group 2 (continuous LD ILO)--low-dose systemic iloprost infusion (0.066 mcg/kg/min) and perfusion washout with iloprost; and Group 3 (continuous HD ILO)--high-dose systemic iloprost infusion (0.1 mcg/kg/min) and perfusion washout with iloprost. The percentage of flap survival was assessed on postoperative day 7. Skin flaps of the animals receiving the continuous systemic infusion of iloprost were noted to have varying percentages of survival, while skin flaps undergoing perfusion washout only were found to have either complete survival using a continuous systemic infusion of iloprost, compared to iloprost perfusion washout alone. In addition, the hypotensive side effects of systemic iloprost infusion limit its use in the rat skin-flap model.

Animals↗
PubMedDate not supplied

Sinonasal hemangiopericytomas: a clinicopathologic and immunohistochemical study of seven cases.

BACKGROUND: Sinonasal hemangiopericytoma (SNHPC) is a rare lesion usually of low-grade malignant potential. Aggressive and metastatic cases are uncommon, and experience using adjuvant therapy on these cases has been limited. Tumor-induced osteomalacia has a very rare association with SNHPC. Further, the diagnosis of SNHPC remains one of histologic-pattern recognition. Traditionally, immunohistochemistry has aided in excluding other diagnoses; only vimentin has been consistently expressed by the tumor spindle cells of HPC. Recent studies have shown that Factor XIIIa is also expressed by HPC, (as well as tumors of fibrohistiocytic differentiation) and hence may be yet another helpful positive marker in establishing an immunohistochemical profile. METHODS: We identified 7 patients at this institution with SNHPC from 1990 to 1994. Immunohistochemistry was performed on seven formalin-fixed paraffin-embedded tumors utilizing antibodies to factor XIIIa as well as antibodies to vimentin, factor VIII, muscle-specific antigen, cytokeratin, and S-100. RESULTS: All 7 patients were initially seen with nasal obstruction or epistaxis and underwent surgical resection. The period of follow-up was from 3 months to 14 years (mean 54 months) for 7 patients. Three patients had recurrent disease after 3, 5, and 10 years. The first 2 were known to have been originally treated by polypectomy. One patient required adjuvant radiotherapy for metastatic disease and local extension. One patient was initially seen with tumor-induced osteomalacia which dramatically improved following resection of the lesion. The immunohistochemical profile revealed strong expression of vimentin in 7/7 cases, and of factor XIIIa in 4/7 cases; tumor cells did not express the other markers studied. CONCLUSIONS: Adequate surgical resection with negative margins appears to be the appropriate therapy for SNHPC. Our 1 case associated with tumor-induced osteomalacia was reversible after surgical excision of the tumor. The immunohistochemical results suggest that the pattern of vimentin and factor XIIIa positivity, as well as lack of expression of other markers, is consistent with the diagnosis of HPC, which still remains in the domain of histopathology.

Adult↗
PubMedDate not supplied

The cardiac inotropic responses to insulin in the rat heart.

Insulin (5 to 40 I.U.) produced dose-dependent positive inotropic effect in the isolated rat heart. The responses to insulin were markedly inhibited in the presence of propranolol (1 . 1X10(-6) M). Insulin responses were markedly reduced in reserpine pretreated (5 mg/kg, i.p.) rats. Theophylline (4.4 mM), the phosphodiesterase inhibitor, potentiated the responses to insulin, whereas imidazole (20 mM), the phosphodiesterase stimulator inhibited the responses to insulin. The data suggest that the positive inotropic effects of insulin in rat heart is mediated through the release of cardiac catecholamines which stimulates beta-adrenoceptors. The final mediator of cardiac action seems to be cyclic-AMP.

Animals↗