Biomedical subjects

S A Ebrahimi

Publications and source records attributed to S A Ebrahimi.

9 recordsLinked to original sources

PubMed2006

Interaction of papaverine with the enalapril-induced cough in guinea pig.

BACKGROUND: Angiotensin Converting Enzyme Inhibitors (ACEIs) like enalapril are extremely effective in the treatment of hypertension and heart failure. One of the most important side-effects of these drugs which can lead to cessation of therapy is a persistant dry cough, induced because of increased bradykinin levels in the lung. Although antitussive alkaloids like codeine are effective in suppressing this cough, they too present a wide range of side-effects, most notably addiction. OBJECTIVE: In a previous work we were able to show that noscapine, a non-narcotic antitussive agent, was able to decrease enalapril induced cough in guinea pigs. In this work, papaverine, another non-narcotic alkaloid found in opium latex was tested in the guinea pig model for antitussive activity. METHOD: Cough was induced in enalapril pretreated guinea pigs by forcing the animals to inspire capsaicin aerosol in an air-tight chamber. Coughs were recorded in control animals and in those which had received different doses of papaverine. Characteristic changes in chamber air pressure, were detected by a pressure transducer. RESULTS: . At low doses (0.5 and 0.25 mg/kg) papaverine was able to decrease enalapril induced cough. CONCLUSION. This effect was not mediated by the action of the drug on mu receptors and was only observed in animals treated with enalapril.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed2004

Effects of mebudipine and dibudipine, two new calcium channel blockers, on guinea-pig isolated common bile duct.

The inhibitory effects of calcium channel blockers; nifedipine and two new compounds, mebudipine and dibudipine, on contractions of isolated guinea-pig common bile duct were investigated. All the compounds tested induced a concentration-dependent reduction of the amplitude of contractile response to electrical stimulation and all the compounds displaced concentration-response curve of calcium chloride to the right in a concentration-dependent manner. The pIC50 values for these compounds acting on electrically stimulated common bile duct were calculated as: dibudipine: 8.50 +/- 0.17; mebudipine: 8.27 +/- 0.20; nifedipine: 7.96 +/- 0.07. The compounds also antagonized the contractile response of K+-depolarized guinea-pig common bile duct to cumulative concentration of calcium. However the inhibitory effect of these compounds were not significantly different.

Animals↗

PubMed2003

Interaction of noscapine with the bradykinin mediation of the cough response.

Angiotensin Converting Enzyme Inhibitors (ACEI) like captopril and enalapril, can induce persistant cough in man. Noscapine, an antitussive alkaloid, can be used to suppress ACEI-induced cough. Some workers have suggested a role for bradykinin in precipitation of ACE-induced cough. Work carried out in our laboratory has shown noscapine to be a non-competitive inhibitor of bradykinin in guinea pig ileum. It is therefore possible that noscapine suppresses cough by blocking the effect of bradykinin receptor activation in the airways. Guinea pigs were placed in a cough-chamber connected to an air pump and a pressure transducer. Capsaicin was sprayed into the chamber and cough was recorded as a distinctive change in air pressure inside the cough-chamber. Animals treated with 1 mg/kg captopril and enalapril for 7 days, showed increased cough response. Ten microgram/kg FR190997, a non-peptide agonist of the bradykinin B2 receptor, also increased the cough response. Noscapine at 0.5, 1 and 2 mg/kg was able to reverse the effects of ACEI and FR190997. Naloxone, a specific opioid receptor inhibitor, did not block the antitussive effects of noscapine in enalapril or FR190997 treated guinea pigs. This antitussive effect of noscapine is not mediated via the mu, kappa or delta opioid receptors. It is therefore possible that noscapine exerts its antitussive action by interfering with the bradykinin cough mediation.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1999

Deletion of chromosome 1 predicts prognosis in pancreatic endocrine tumors.

Endocrine tumors, such as parathyroid adenomas and pheochromocytomas, frequently have deletions of chromosome 1, suggesting that inactivation of a tumor suppressor gene from chromosome 1 is important in their tumorigenesis. We hypothesized that deletion of chromosome 1 may contribute to pancreatic endocrine tumor formation. Twenty-nine sporadic and MEN1 pancreatic endocrine tumors were studied for loss of heterozygosity (LOH) with 12 chromosome 1 microsatellite markers. LOH on chromosome 1 was identified in 10 of 29 (34%) tumors studied. Allele loss occurred more frequently in tumors with hepatic metastases (7 of 8) than tumors without metastases (3 of 21) (P = 0.004). Tumors in patients with lymph node involvement and patients with multiple endocrine neoplasia type 1 did not demonstrate LOH for chromosome 1 markers. These data suggest that loss of chromosome 1 is associated specifically with the development of hepatic metastases in patients with sporadic pancreatic endocrine tumors.

Chromosomes, Human, Pair 1↗

PubMed1998

Mutation of the MENIN gene in sporadic pancreatic endocrine tumors.

Pancreatic endocrine tumors occur both sporadically and as part of the multiple endocrine neoplasia type 1 (MEN1) syndrome. MEN1 is an autosomal dominant disease characterized by parathyroid hyperplasia, pancreatic endocrine tumors, and pituitary adenomas. The MEN1 gene called MENIN maps to chromosome 11q13 and is thought to function as a tumor suppressor gene. We previously demonstrated loss of heterozygosity (LOH) at 11q13 in approximately 40% of sporadic pancreatic endocrine tumors and hypothesize that MENIN is involved in the development of these tumors. Thirty-one sporadic pancreatic endocrine tumors were analyzed for mutation of MENIN by nonradioactive single-stranded conformation polymorphism. Twelve mutations were detected in 31 sporadic pancreatic endocrine tumors (34%). Twelve of these 31 tumors previously demonstrated loss of heterozygosity at 11q13. Of the tumors with LOH, seven contained mutations of the MENIN gene (58%). The majority of the MENIN mutations occurred within exon 2. Two independent mutations in MENIN were detected in a gastrinoma that also revealed LOH, leading to the possibility of another tumor suppressor gene locus at 11q13. Mutations were present in both benign and malignant pancreatic endocrine tumors, suggesting that a MENIN gene mutation is a frequent and early event in the tumorigenesis. The high incidence of truncating mutations in tumors with LOH at 11q13 support the hypothesis that MENIN is a tumor suppressor gene.

Amino Acid Substitution↗

PubMed1998

Deletion mapping of endocrine tumors localizes a second tumor suppressor gene on chromosome band 11q13.

Multiple endocrine neoplasia type 1 syndrome (MEN1, MIM 131100), an autosomal dominant disease, is characterized by parathyroid hyperplasia, pancreatic endocrine tumors, and pituitary adenomas. These tumors also occur sporadically. Both the familial (MEN1) and the sporadic tumors reveal loss of heterozygosity (LOH) for chromosome band 11q13 sequences. Based on prior linkage and LOH analyses, the MEN1 gene was localized between PYGM and D11S460. Recently, the MEN1 gene (menin) has been cloned from sequences 30-kb distal to PYGM. We performed deletion mapping on 25 endocrine tumors (5 MEN1 and 20 sporadic) by using 21 polymorphic markers on chromosome band 11q13. Of these, two (137C7A, 137C7B) were derived from PYGM-containing BAC (bacterial artificial chromosome-137C7) sequences, one from INT2-containing cosmid sequences and the marker D11S4748, a (CA)20 repeat marker that was developed by us. The LOH analysis shows that the markers close to the MEN1 (menin) gene were not deleted in three of the tumors. These tumors, however, showed LOH for distal markers. Thus, the data suggest the existence of a second tumor suppressor gene on chromosome band 11q13.

Chromosome Banding↗

PubMed1997

Tracking the MEN1 gene.

Multiple endocrine neoplasia type 1 (MEN1) is a hereditary autosomal dominant disease characterized by parathyroid hyperplasia, pancreatic endocrine tumors, and pituitary adenomas. Sporadic forms of these tumors are more common than their inherited counterparts and share common genetic abnormalities. We have been studying the molecular genetics of sporadic pancreatic endocrine tumors to identify the tumor suppressor gene responsible for MEN1 by positional cloning. This review introduces the reader to the fundamentals of these molecular genetic techniques and outlines the general strategy used to isolate this gene.

Chromosome Mapping↗

PubMed1994

Some problems associated with measuring monoamine oxidase activity in the presence of sodium azide.

The colourimetric assay of monoamine oxidase activity, as hydrogen peroxide production, normally requires the use of sodium azide to inhibit breakdown of hydrogen peroxide by catalase. Sodium azide was shown to act as an uncompetitive inhibitor of benzylamine deamination with an inhibitor constant of 1.5 mM. Catalase activity of isolated rat liver mitochondria could be eliminated with the irreversible inhibitor of catalase, 3-amino-1,2,4-triazole. The treatment did not affect benzylamine deaminating activity. The catalase-free preparation could be used to assay monoamine oxidase activity colourimetrically, as hydrogen peroxide production, in the absence of sodium azide.

Amitrole↗

PubMed1994

Some kinetic properties of guinea pig liver monoamine oxidase.

Titration of monoamine oxidase activity in isolated guinea pig liver mitochondria with clorgyline and assay of remaining activity with tyramine yielded biphasic inhibition curves. The position of the plateaus obtained with mitochondria from four animals, indicated that the B form of monoamine oxidase accounted for 30% to 70% of the tyramine deaminating activity. Benzylamine deamination was selectively inhibited by (-)-deprenyl. However, benzylamine and other amines which are selective substrates for the B form of monoamine oxidase from the rat, were deaminated at only low rates by the guinea pig liver enzyme. Guinea pig liver contains a monoamine oxidase-B which is unusual in that although it exhibits apparently normal sensitivity to selective irreversible inhibitors, it has a low catalytic activity with substrates which the enzyme from rat liver deaminates rapidly.

Animals↗