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Biomedical subjects

H Mahajan

Publications and source records attributed to H Mahajan.

12 recordsLinked to original sources
PubMed2006

Vascular and metabolic effects of methacholine in relation to insulin action in muscle.

AIMS/HYPOTHESIS: Methacholine (MC) is a nitric oxide vasodilator, but unlike other vasodilators, it potentiates insulin-mediated glucose uptake by muscle. The present study aimed to resolve whether this action was the result of a vascular effect of MC leading to increased muscle perfusion or a direct effect of MC on the myocytes. We hypothesise that vascular-mediated insulin-stimulated glucose uptake responses to MC occur at lower doses than direct myocyte MC-mediated increases in glucose uptake. METHODS: The vascular and metabolic effects of this vasodilator were examined in rats in vivo using a novel local infusion technique, and in the pump-perfused rat hindlimb under conditions of constant flow. RESULTS: Local infusion of low-dose MC (0.3 micromol/l) into the epigastric artery of one leg (test) in vivo markedly increased femoral blood flow and decreased vascular resistance, without effects in the contra-lateral leg. Capillary recruitment, but not glucose uptake, was increased in the test leg. All increases caused by MC were confined to the test leg and blocked by local infusion into the test leg of N-nitro-L-arginine methyl ester (L-NAME), but not by infusion of N-nitro-D-arginine methyl ester (D-NAME). In the constant-flow pump-perfused rat hindlimb, infusion of 0.6 micromol/l MC vasodilated the pre-constriction effected by 70 nmol/l noradrenaline or 300 nmol/l serotonin, and this was blocked by 10 micromol/l L-NAME. 2-Deoxyglucose in muscle was increased by 30 micromol/l MC (p<0.05), but was unaffected by 3 micromol/l MC. All increases in 2-deoxyglucose uptake by 30 micromol/l MC were blocked by 10 micromol/l L-NAME. CONCLUSIONS/INTERPRETATION: MC has dose-dependent effects both on the vasculature and on muscle metabolism. At low dose (0.3-3 micromol/l), MC is a potent vasodilator in muscle, both in vivo and in vitro, without metabolic effects; at higher doses (> or =30 micromol/l) MC has a direct metabolic effect leading to increased glucose uptake. Both the vascular and metabolic effects are sensitive to L-NAME. The low-dose enhancement of insulin action in vivo by MC, which has been reported previously, thus seems to be attributable to vascular effects.

Animals↗
PubMed2006

Craniofacial surgery for craniometaphyseal dysplasia.

Craniometaphyseal dysplasia (CMD) is a rare congenital bone dysplasia with abnormal bony overgrowth leading to characteristic facial features and cranial nerve compression. We present a 10-year-old child with bony swelling at the nasal root since birth along with decreased hearing in both ears. She had normal developmental milestones and intelligence. On examination, she had bossing of forehead with very broad nasal root, short septum, hypertelorism and epicanthic folds. CT scan with 3D reconstruction revealed grossly thickened calvarium and hyperostosis and sclerosis of the cranial base. As the major concern of the parents was cosmetic, craniofacial reconstruction was performed with good cosmetic outcome.

Adult↗
PubMed2004

Local methacholine but not bradykinin potentiates insulin-mediated glucose uptake in muscle in vivo by augmenting capillary recruitment.

AIMS/HYPOTHESIS: Insulin has nitric-oxide-dependent vasodilatory effects in muscle, including capillary recruitment, that enhance access for itself and glucose. However, nitric-oxide-dependent vasodilators other than methacholine do not enhance insulin action. Our hypothesis is that methacholine, unlike bradykinin, enhances insulin-mediated glucose uptake in muscle by augmenting capillary recruitment. METHODS: Local infusion of either methacholine or bradykinin into one leg of the anaesthetised rat was made during physiological insulin (3 mU.kg(-1).min(-1)) infusion under euglycaemic conditions and without affecting systemic blood pressure. Whole-body glucose infusion was determined, as was femoral blood flow, 2-deoxyglucose uptake into calf muscles and the metabolism of infused 1-methylxanthine, a measure of capillary recruitment for each leg. RESULTS: Methacholine alone (0.3 micromol.l(-1)) increased femoral arterial blood flow, increased capillary recruitment but had no effect on 2-deoxyglucose uptake of the test leg relative to the contra-lateral control leg. Insulin alone (systemically) required a glucose infusion rate of 8.7 mg.kg(-1).min(-1) to maintain euglycaemia, increased 2-deoxyglucose uptake and capillary recruitment, but was without effect on femoral blood flow in either leg. Local methacholine with systemic insulin infusion increased femoral blood flow, 2-deoxyglucose uptake and capillary recruitment in the test leg only. Bradykinin (0.07 micromol.l(-1)), alone or with insulin, administered in a manner that increased femoral blood flow similarly to methacholine, did not affect 2-deoxyglucose uptake or capillary recruitment. CONCLUSIONS/INTERPRETATION: Methacholine but not bradykinin enhances insulin-mediated muscle glucose uptake in vivo. We conclude that methacholine acts at specific sites in the vasculature of muscle to stimulate capillary recruitment and thereby enhance insulin access.

Animals↗
PubMed1994

Cushing's disease: pituitary imaging.

Fourteen patients with adrenocorticotropic hormone (ACTH)-dependent hypercortisolism underwent pituitary scanning with computed axial tomography (CT) and magnetic resonance imaging (MRI). Computed tomography revealed pituitary macroadenomas in two patients, pituitary hyperplasia in one and a suspicion of pituitary microadenoma in one. Thirteen patients underwent MRI. One with a macroadenoma diagnosed on CT did not undergo MRI. The MRI revealed a pituitary macroadenoma in one, microadenoma in three and hyperplasia in two cases. Magnetic resonance imaging following gadolinium diethylene triamine penta acetic acid (gd-DTPA) enhancement revealed four more pituitary microadenomas. All patients who had pituitary adenomas (micro and macro) and hyperplasia underwent trans-sphenoidal pituitary surgery. One of the two patients, who had an enlarged pituitary on imaging but no demonstrable adenoma, was found to have a microadenoma at surgery. Patients with ACTH-dependent hypercortisolism should undergo MRI of the pituitary gland to identify/localize corticotroph pituitary adenomas. The study should include gd-DTPA enhancement in cases where the scan is normal.

Adenoma↗
PubMed1993

Magnetic resonance imaging of the brain in idiopathic hypogonadotropic hypogonadism.

Magnetic resonance imaging (MRI) of the pituitary, hypothalamus and olfactory sulci was performed in 40 patients with idiopathic hypogonadotropic hypogonadism (IHH). Twelve of these patients had an impaired sense of smell (Kallmann's syndrome). Sagittal and coronal imaging revealed no morphological abnormalities in the hypothalamic-pituitary region. On axial imaging rudimentary, hypoplastic or aplastic olfactory sulci were found in eight cases. All patients with olfactory sulcal abnormalities had associated hyposmia (one case) or anosmia (seven cases). Structural defects identifiable on MRI were present only in 20 per cent of patients with IHH.

Adult↗
PubMed1992

Undescended testis: evaluation by magnetic resonance imaging.

We describe our experience of prospective magnetic resonance imaging (MRI) study in patients of undescended testis, with a 1.5 T equipment using body coil. There were thirty two patients, aged 1.5 to 14 years with a mean age of nine years. Surgical follow up was obtained for thirty one patients. We were able to indicate the position of 26 testes in 22 patients and absence of five testes in three patients. MRI was falsely positive and negative for five and two testes, respectively. Testicular tissue at ectopic site was identified by presence of characteristic signal intensity pattern, mediastinum testis and its location along empty spermatic canal in cases of inguinal testis either singly or in combination. MRI was able to detect atrophic changes in four testes, confirmed on surgery. The study concludes that MR imaging is useful in the localization and tissue characterization of a non palpable testis. However, it is not sensitive enough for complete exclusion of the diagnosis of an undescended testis. Thus a surgical or laproscopic exploration may be needed further in selective cases for the management of patient.

Abdomen↗
PubMed1989

Hepatic arterial infusion of human recombinant tumor necrosis factor-alpha. An experimental study in dogs.

Local and systemic toxicities associated with hepatic arterial infusion of human recombinant tumor necrosis factor (rTNF) were studied in healthy adult mongrel dogs. The animals received saline containing human serum albumin with or without rTNF (0.02, 0.2, or 2.0 mg/m2). Arteriograms were made, and blood samples were collected for hematologic and biochemical analyses at regular intervals. The dogs were killed at 1, 3, and 7 days postinfusion and complete necropsies were performed. Specimens were obtained from various tissues for histopathologic evaluation. Results indicated that all but the highest dose of rTNF were well tolerated. Severe histopathologic changes were found in the liver, spleen, and kidneys of the animals receiving 2.0 mg/m2 rTNF. In addition, focal tubular degeneration was found in one dog administered 0.2 mg/m2 rTNF. These data suggest that the upper dose limit for hepatic arterial infusion of rTNF is between 0.2 and 2.0 mg/m2 and that renal function should be closely monitored after infusion.

Angiography↗
PubMedDate not supplied

Magnetic resonance imaging of malignant fibrous histiocytoma.

The magnetic resonance imaging (MRI) changes in 39 patients with malignant fibrous histiocytoma (MFH) were reviewed retrospectively. Twenty-one sarcomas were in the lower extremity, five each in the upper extremity and trunk, two each in the neck and heart, and one each in the maxillary sinus, sella turcica, tongue, and spermatic cord. The examinations were performed with spin-echo sequences on a 1.5 Tesla Signa Scanner (GE, Milwaukee WI). Twenty-two tumors exhibited intermediate signal intensity on T1-weighted images and 23 were of high signal intensity on T2-weighted images. There was no significant differences in signal intensity of 12 preoperative and 13 recurrent neoplasms. Twelve of 13 patients were correctly diagnosed as having postoperative changes. The MR sensitivity and specificity for detecting a neoplasm were 96% and 83% respectively, but the signal changes were nonspecific for MFH. When compared to CT in 14 patients, MR better defined the extent of the MFH, its relationship to surrounding tissues and vessels, and best differentiated residual or recurrent disease from postoperative changes when examined at least 3 months after surgery.

Adolescent↗
PubMedDate not supplied

Synovial sarcoma: MR imaging.

Ten patients with biopsy-proved synovial sarcoma were evaluated by magnetic resonance (MR) imaging on a 1.5-T unit. The lesions showed intermediate signal intensity on T1-weighted images and heterogeneous high signal intensity on T2-weighted images. Tumors were well-demarcated from normal tissues. Additional information included adjacent bone involvement (one case), femoral vein invasion by tumor (one case), and hemorrhage within the tumors (one case). Four patients underwent a repeat MR examination following chemotherapy. This showed a decrease in size and increase in the signal intensity of three tumors on T2-weighted images, proven to be due to necrosis in one. These changes correlated with clinical regression of disease. While MR in synovial sarcoma does not have any specific signal intensity, it proved to be useful in defining the extent of disease and in determining the response to chemotherapy.

Adolescent↗
PubMedDate not supplied

Ruptured supratentorial dermoid cysts.

Two cases with ruptured supratentorial dermoid cysts are presented. Computerised tomography and magnetic resonance findings are illustrated. The pathology and differential diagnosis is discussed.

Adult↗