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Biomedical subjects

M Sharifi

Publications and source records attributed to M Sharifi.

At least 19 recordsLinked to original sources
PubMed2006

Platelet nitric oxide synthase is activated by tyrosine dephosphorylation: possible role for SHP-1 phosphatase.

BACKGROUND: Endothelial nitric oxide synthase (eNOS) activity in endothelial cells is regulated by post-translational phosphorylation of critical serine, threonine and tyrosine residues in response to a variety of stimuli. However, the post-translational regulation of eNOS in platelets is poorly defined. OBJECTIVES: We investigated the role of tyrosine phosphorylation in the regulation of platelet eNOS activity. METHODS: Tyrosine phosphorylation of eNOS and interaction with the tyrosine phosphatase SHP-1 were investigated by coimmunoprecipitation and immunoblotting. An in vitro immunoassay was used to determine eNOS activity together with the contribution of protein tyrosine phosphorylation. RESULTS: We found platelet eNOS was tyrosine phosphorylated under basal conditions. Thrombin induced a dose- and time-dependent increase in eNOS activity without altering overall level of tyrosine phosphorylation, although we did observe evidence of minor tyrosine dephosphorylation. In vitro tyrosine dephosphorylation of platelet eNOS using a recombinant protein tyrosine phosphatase enhanced thrombin-induced activity compared to thrombin alone, but had no effect on endothelial eNOS activity either at basal or after stimulation with bradykinin. Having shown that dephosphorylation could modulate platelet eNOS activity we examined the role of potential protein phosphatases important for platelet eNOS activity. We found SHP-1 protein tyrosine phosphatase, co-associated with platelet eNOS in resting platelets, but does not associate with eNOS in endothelial cells. Stimulation of platelets with thrombin increased SHP-1 association with eNOS, while inhibition of SHP-1 abolished the ability of thrombin to induce elevated eNOS activity. CONCLUSIONS: Our data suggest a novel role for tyrosine dephosphorylation in platelet eNOS activation, which may be mediated by SHP-1.

Animals↗
PubMed2006

The occurrence, variations and diameter of the human condylar canal in relation to the jugular foramen.

In medical practice, especially in analysis of radiograms and computed tomography scans, it is very important to be familiar with the anatomy of the skull base, not only the normal and typical anatomical structures but also the variations and anomalies. One of the important venous foramina of the human skull is the condylar canal. This structure is described as the most stable and permanent venous emissary, with a prevalence of up to 100%. In our study, based on 100 human macerated skulls, this canal was encountered in 81% of cases. In several it was double. We have not encountered any information on this in the available literature. We found that the condylar canal in humans could be double and that the size of the external opening of this canal is not crucial in relation to the size of the jugular foramen. There was no significant correlation between the jugular foramen and the condylar canal in our specimens.

Female↗
PubMed2000

Coronary angioplasty and stenting in orthotopic heart transplants: a fruitful act or a futile attempt?

Accelerated allograft coronary artery disease remains the major cause of mortality after the first year of transplantation. Despite the extensive use of stents and angioplasty in coronary artery disease, there is a paucity of data about the efficacy of such interventions in orthotopic heart transplants. The authors herein report the outcome of those patients in their institution who had undergone percutaneous coronary artery angioplasty and stenting at a late stage of their transplantation. Within a 12-year period, 106 adult patients underwent orthotopic heart transplantation at their institution. Eight of these patients with 17 lesions underwent deployment of nine stents and eight angioplasties 8.1 +/- 3.2 years posttransplantation. There were 15 denovo and two restenotic lesions. The indications for intervention were presence of symptoms in five patients and severity of lesions in three asymptomatic patients detected on their follow-up angiogram. All patients had angiographic worsening of lesions at their follow-up angiogram. The initial procedural success for both stented and angioplastied lesions was 100%. Within a mean angiographic follow-up of 261 days, all balloon angioplastied lesions had developed restenosis, whereas within a mean period of 67 days, 50% of stented lesions had developed restenosis. On the follow-up angiogram, deterioration of the nontreated segments were noted throughout the coronary arterial tree; however, the immediate proximal and distal parts of the target segments demonstrated an exaggerated hyperproliferative response as compared to other sites. The overall median time to the detection of restenosis for both stented and angioplastied lesions was 5.2 months (inner quartile 2.5-6.2 months). The authors conclude that angioplasty and stenting late in the course of transplantation is associated with a significant restenosis rate and in such patients earlier or alternative catheter-based interventions must be considered.

Angioplasty, Balloon, Coronary↗
PubMed1999

Simulation of ion trajectories in a quadrupole ion trap: a comparison of three simulation programs

An attempt has been made to compare the performance, design and operation of three simulators, ISIS, ITSIM and SIMION-3D, when applied to the calculation of ion trajectories in a quadrupole ion trap. For the simulation of the trajectory of a single ion in a collision-free system, the calculated spatial trajectory components, kinetic energies and secular frequencies from the three simulators were virtually identical. It is concluded that, despite the various approaches to electrode design, calculation of fields, integration methods and ion generation tactics, there is a remarkable degree of consistency among the products of the simulators when dealing with collision-free conditions. The results of the ion injection simulations under collisional conditions were indicative of the complexity that can be introduced into the simulations with little effort. Random effects such as collisions of ions with He buffer gas and accumulated calculation errors together with the different collision model settings and the different approaches to field calculation are thought to have contributed to the somewhat minor differences in trapping efficiency. SIMION is the simulator of choice for the simulation of ion trajectories in hybrid instruments and in custom-designed assemblies of electrodes; and ITSIM would appear to be the best choice on the basis of computational speed for running multiparticle simulations and user friendliness. Both ISIS and ITSIM are adept at providing detailed information of collision events. Copyright 1999 John Wiley & Sons, Ltd.

Journal Article↗
PubMed1999

Left internal mammary artery graft perforation due to high-pressure stent deployment.

Perforation of newly placed left internal mammary artery (LIMA) grafts due to stent deployment is an infrequent but potentially dangerous complication of coronary interventions. It may lead to brisk hemorrhage and massive cardiac tamponade requiring emergent pericardiocentesis and surgery. We report a case of a LIMA graft perforation following stent deployment with a high-pressure balloon 12 days after surgery. The patient was treated with emergent pericardiocentesis, rapid autotransfusion of the pericardial aspirate into the systemic circulation, and surgical repair of the ruptured vessel.

Aged↗
PubMed1999

Saphenous vein graft ectasia: an unusual late complication of coronary artery bypass surgery. A case report.

Aneurysms and ectasias of saphenous vein grafts are infrequent complications of coronary artery bypass surgery. They usually present as an expanding asymptomatic mediastinal mass on chest x-ray film or computed tomography scan. Though rare, they must be excluded from the differential diagnosis of mediastinal masses to avoid potentially dangerous needle biopsy. The authors describe ectasia of a saphenous vein graft in a 62-year-old man 14 years after coronary artery bypass surgery. The relevant literature is also discussed.

Aortic Aneurysm, Abdominal↗
PubMed1999

Arteriography of the left internal mammary artery graft utilizing a balloon-tipped floatation catheter: an alternative approach.

In this report, we describe an alternative method to the conventional arteriographic techniques of the left internal mammary artery (LIMA) graft using a balloon-tipped floatation catheter placed within the left subclavian artery. The floatation catheter will serve as both an occluder of the subclavian artery as well as a port for contrast injection. It may be effectively employed in the rare instances where direct cannulation of the LIMA graft is not possible.

Cardiac Catheterization↗
PubMed1997

Influence of dietary fat on the intestinal absorption of lipophilic compounds in goldfish (Carassius auratus).

Dietary uptake of a mixture of pp'DDT and four chlorobenzenes from diets with different lipid contents was measured in goldfish (Carassius auratus) in order to investigate the mechanism of intestinal absorption of organic compounds. The results of the experiments suggest that intestinal absorption is basically controlled by chemical diffusion rather than lipid coassimilation. The extent of dietary uptake as indicated by biomagnification factor was strongly correlated with the chemical log Kow, indicating that uptake of the chemicals from the gastrointestinal fluid is similar to the uptake from other aqueous environments and lipid content of the food in the range used in these experiments (2.9-10.9%) could not influence the uptake of lipophilic chemicals.

Animals↗
PubMed1997

Simultaneous presence of a large coronary aneurysm and ectasia in a young patient with myocardial infarction--a case report.

Idiopathic or congenital coronary artery ectasias and aneurysms are uncommon forms of coronary artery disease. The prognosis and optimal management of such patients remains unknown. The authors describe the case of an otherwise healthy 30-year-old man with concomitant severe right coronary artery ectasia and left main coronary artery aneurysm who sustained a mild anterior myocardial infarction. There was no obstructive coronary artery disease, and no cause for the lesions could be identified. Chronic anticoagulation and antiplatelet therapy were initiated with resolution of symptoms.

Adult↗
PubMed1996

First pass Tc-99m MIBI ventriculography in the assessment of left ventricular diastolic function. A comparison with Doppler echocardiography.

Tc-99m MIBI is used for myocardial imaging and first-pass studies. However, little is known about its utility in the assessment of left ventricular diastolic function. The authors retrospectively compared first pass studies of Tc-99m MIBI at rest with Doppler flow velocity measurements to assess left ventricular diastolic performance. Thirty-nine patients who had both studies performed within 48 hours of each other were evaluated. Three indices of diastolic function were measured by first pass Tc-99m MIBI ventriculography and Doppler echocardiography: 1) Time to peak early diastolic velocity; 2) normalized peak filling rate; and 3) half filling fraction. The results demonstrated a correlation of 0.82 (P < 0.001), 0.82 (P < 0.001), and 0.53 (P = 0.001) for the above indices, respectively. This study indicates that the indices of left ventricular diastolic function by first pass Tc-99m MIBI compare favorably with those derived from Doppler flow velocity measurements in which the diagnostic value has been previously established. Both methods accurately reflect diastolic flow and may facilitate clinical evaluation of diastolic function.

Adult↗
PubMed1996

Bronchial arteriovenous malformation in a child with hemoptysis. A case report.

Pulmonary arteriovenous (AV) malformations occur sporadically and in the pediatric population are most commonly associated with hereditary hemorrhagic telangiectasia. Hemoptysis is an infrequent presentation in this age group. Pulmonary angiography is considered to be the definitive diagnostic modality. The authors describe an otherwise healthy eleven-year- old girl who presented with massive hemoptysis secondary to a large bronchial AV malformation unrelated to any congenital anomalies. The pulmonary angiogram appeared normal and the diagnosis was established by digital subtraction aortography. Successful embolotherapy was performed by selective injection of polyvinyl alcohol particles into the culprit bronchial artery.

Arteriovenous Malformations↗
PubMed1995

Inadvertent malposition of a transvenous-inserted pacing lead in the left ventricular chamber.

In conclusion, we propose the following approach to prevent and manage lead malposition in the left ventricle: A 12-lead electrocardiogram in the paced mode and an anterior and lateral chest view should be thoroughly inspected shortly after pacemaker implantation. A definitive diagnosis of malposition can be established with these tests. Development of any neurologic symptoms should be attributed to the malpositioned lead until proved otherwise. In such patients, serious consideration should be given to transcatheter or surgical lead extraction after a period of anticoagulation. If this is not possible, chronic anticoagulation with warfarin must be initiated, achieving an international normalized ratio of > or = 2.5. Antiplatelet therapy alone may not confer adequate protection against future cerebral events. Furthermore, most patients with neurologic manifestations do not have echocardiographic evidence of thrombus on the lead. Conversely, presence of thrombus is highly associated with neurologic symptoms. Any intraarterial lead must be removed due to inevitable complications. Patients who have remained completely asymptomatic for > or = 3 years may be followed carefully with no therapy. For asymptomatic patients diagnosed before this time period, we recommend empiric therapy with antiplatelet agents or low-dose warfarin (international normalized ratio 1.5-2) with careful observation for symptoms.

Cardiac Pacing, Artificial↗
PubMed1995

Myocardial infarction with angiographically normal coronary arteries.

To determine the prevalence rate and clinical and hemodynamic profile of patients with myocardial infarction (MI) with angiographically normal coronary arteries, we analyzed 3,403 consecutive angiograms performed within a 4.5-year period. Of these studies, 1,124 were performed following an acute MI. Through a computerized search, 12 patients were identified who had documented MI with normal or insignificant (< 30% stenosis in one epicardial vessel only) coronary disease. Q-wave MI developed in five patients (group A) and non-Q-wave MI developed in seven patients (group B). Group A patients were all men whereas group B patients were all women. Overall, group A patients were younger (p = 0.003), had a longer smoking history (p = 0.008), and a higher cardiac index (p = 0.005). In ten patients, areas of localized dyskinesia or hypokinesia were shown on left ventricular cineangiography. Mitral valve prolapse was present in four of the patients and varying degrees of mitral regurgitation were identified in another six. The prevalence rate of MI with angiographically normal coronary arteries was 1% in this study. This entity had a bimodal age and sex distribution: a younger age group, all men, with a stronger cigarette smoking history who had Q-wave MI vs an older age group, all women, and no significant association with cigarette smoking who developed non-Q-wave MI. A mean follow-up of 4 years demonstrated a favorable prognosis in both groups.

Adult↗