Search PubMed⌕ Search

Biomedical subjects

M Oz

Publications and source records attributed to M Oz.

At least 55 records · Page 3Linked to original sources
PubMed1995

Frequency-dependent effect of ethanol on action potentials of frog skeletal muscle fibers.

The effects of ethanol at the concentrations of 88 mM (0.5%) and 165 mM (1%) on single and repetitively elicited sodium action potentials were investigated in frog skeletal muscle fibers. At the concentrations used, although single action potentials remained intact, repetitively generated action potentials elicited with the stimulation frequency of 100 Hz for 2 sec were greatly inhibited. The inhibition of repetitively elicited sodium action potentials was completely reversed at 25 Hz. In conclusion, results indicate that ethanol inhibits sodium action potentials in a frequency-dependent manner.

Action Potentials↗
PubMed1994

The effects of verapamil on tetanic contractions of frog's skeletal muscle.

The effects of the organic calcium channel antagonist, verapamil, were tested on twitches and tetanic contractions (100 Hz, 2 sec) in frog toe muscles. At low concentrations (3 x 10(-6) M), verapamil had no effect on the maximum amplitudes of twitches, but significantly reduced the size of the tetanic responses. This depression was observed as an inability to maintain the maximum tetanic tension for more than 0.5 sec. With increasing concentrations up to 10(-4) M of verapamil, its depressant effect on tetanic responses gradually increased, and at very high concentrations (10(-4) M) of verapamil, twitches were also blocked. Intracellular microelectrode recordings showed that there was no block of the action potentials during the stimulus train at the concentration of 3 x 10(-6) M of verapamil. These results support the concept that during tetanic responses, the voltage sensitive Ca2+ channels in the t-tubules open and the Ca2+ ions entering via these channels are required to maintain the full strength of the contraction. At higher concentrations, verapamil blocked Na+ action potentials during the stimulus trains in a concentration and use-dependent manner.

Action Potentials↗
PubMed1994

Effect of the calcium channel agonist Bay K8644 on mechanical and electrical responses of frog skeletal muscle.

The effects of Bay K8644, a Ca2+ channel agonist, on the mechanical and electrical properties of frog skeletal muscle fibers were investigated. At relatively low concentrations, such as 10(-6) and 10(-5) M, Bay K8644 significantly potentiated the maximum amplitudes of twitch responses, and this effect was not reversed in the presence of the calcium channel antagonist nitrendipine. At higher concentrations, such as 10(-4) M, Bay K8644 depressed the amplitudes of twitch responses, and nitrendipine did not change this effect. At all concentrations, Bay K8644 greatly reduced the area under the tetanic force versus time curve, and this effect was not modified by the concomitant application of Bay K8644 and nitrendipine. Intracellular recordings revealed that the depressing effect of Bay K8644 on tetanic contractions was due to the blockade of sodium action potentials. In conclusion, the present results suggest that the modulation of twitch responses by calcium channel agonist and antagonists, at the concentration range used, is not related to the expected modulation of voltage-sensitive slow calcium channels in frog skeletal muscle fibers, and tetanic contractions are depressed by the calcium channel agonist Bay K8644 through its effect on sodium channels.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1994

Comparison of a single dose of aerosol salbutamol and fenoterol/ipratropium on bronchial asthmatic patients.

A combination dose aerosol of fenoterol hydrobromide (200 micrograms) and ipratropium bromide (80 micrograms) was compared with aerosolized salbutamol (200 micrograms) in 10 stable asthmatic patients. With both treatments a statistically significant improvement was noticed in both FEV1 and PEF measurements starting after 15 minutes and continuing until 330 to 360 minutes. No statistically significant differences in one second Forced Vital Capacity (FEV1) and Peak Expiratory Flow (PEF) was noted between the two treatments. No side effect was noticed. As a result, it was concluded that in bronchial asthmatic patients, the bronchodilator effects of the combination of a beta-2 agonist with anticholinergic drugs was as effective and lasted as long as salbutamol. This combination, in order to prevent cardiovascular complications, could be selected as a suitable treatment for those patients who need high doses of beta-2 agonist drugs.

Administration, Inhalation↗
PubMed1993

Restoration of the cAMP second messenger pathway enhances cardiac preservation for transplantation in a heterotopic rat model.

Current organ preservation strategies subject graft vasculature to severe hypoxia (PO2 approximately 20 Torr), potentially compromising vascular function and limiting successful transplantation. Previous work has shown that cAMP modulates endothelial cell (EC) antithrombogenicity, barrier function, and leukocyte/EC interactions, and that hypoxia suppresses EC cAMP levels. To explore the possible benefits of cAMP analogs/agonists in organ preservation, we used a rat heterotopic cardiac transplant model; dibutyryl cAMP added to preservation solutions was associated with a time- and dose-dependent increase in the duration of cold storage associated with successful graft function. Preservation was also enhanced by 8-bromo-cAMP, the Sp isomer of adenosine 3',5'monophosphorothioate, and types III (indolidan) and IV (rolipram) phosphodiesterase inhibitors. Neither butyrate alone nor 8-bromoadenosine were effective, and the cAMP-dependent protein kinase antagonist Rp isomer of adenosine 3',5'monophosphorothioate prevented preservation enhancement induced by 8-bromo-cAMP. Grafts stored with dibutyryl cAMP demonstrated a 5.5-fold increase in blood flow and a 3.2-fold decreased neutrophil infiltration after transplantation. To explore the role of cAMP in another cell type critical for vascular homeostasis, vascular smooth muscle cells were subjected to hypoxia, causing a time-dependent decline in cAMP levels. Although adenylate cyclase activity was unchanged, diminished oxygen tensions were associated with enhanced phosphodiesterase activity (59 and 30% increase in soluble types III and IV activity, respectively). These data suggest that hypoxia or graft ischemia disrupt vascular homeostasis, at least in part, by perturbing the cAMP second messenger pathway. Supplementation of this pathway provides a new approach for enhancing cardiac preservation, promoting myocardial function, and maintaining vascular homeostatic properties.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1991

Malignant carcinoid tumor metastatic to the dura mater simulating a meningioma.

A 50-year-old man, transferred from another hospital, was admitted because of adult onset seizures. Nine months earlier, he had undergone an esophagogastrectomy; the lesion was confirmed to be a carcinoid tumor. Laboratory tests, chest x-rays, and electrocardiogram were normal. A second liver and spleen scan was performed. A computed tomographic scan revealed a well-circumscribed homogeneous enhancement of a lesion in the left frontal superficial area. On the 10th day, the patient underwent a left frontal parietal craniotomy. Postoperatively, he manifested no residual neurological deficits and was discharged on the 6th postoperative day. A week later, he was readmitted for treatment of aphasia and right hemiparesis; he was treated and discharged. The patient survived 16 more months. The occurrence of central nervous system metastasis from carcinoid tumor is rare. This tumor resembled, in many respects, a parasagittal meningioma. Radiological findings on the computed tomographic scan were typical of these tumors. This patient was diagnosed as having metastatic disease just 9 months after the diagnosis of the primary tumor and 13 months from the onset of any symptoms. This is a short period of time compared with that reported in other cases.

Brain Neoplasms↗
PubMed1991

Decrease in the size of tetanic responses produced by nitrendipine or by extracellular calcium ion removal without blocking twitches or action potentials in skeletal muscle.

The effects of removing extracellular Ca++ ions or of adding the organic calcium channel antagonist, nitrendipine, were tested on twitches and tetani (100 Hz for 2 sec) in frog toe muscles. Under conditions that did not reduce or that potentiated twitches, both procedures reduced the size of the tetanic responses. This depression was seen as an inability to maintain the maximum tetanic tension for more than 0.5 sec. Intracellular microelectrode recordings showed that the muscle fibers were depolarized (mean about 23 mV) during the stimulus train and the fiber only slowly repolarized after the train. The latter effect is the "late negative afterpotential" and it is produced by the accumulation of K+ ions in the t-tubules during the action potential train. Neither the depolarization nor the late negative afterpotentials were decreased in amplitude by nitrendipine. These results indicate that the voltage-sensitive, slow Ca++ channels are opened by the accumulation of K+ ions in the t-tubules during the tetanus and that the Ca++ ions entering via these channels are required to maintain the full strength of the tetanic contraction. It is suggested that this is a function of these Ca++ channels concentrated in the t-tubules of skeletal muscle fibers.

Action Potentials↗
PubMed1989

Replacement of the abdominal aorta with a sutureless intraluminal ringed prosthesis.

To evaluate our experience with sutureless intraluminal ringed grafts in the abdominal aorta, we reviewed all patients who were managed with this device from 1980 to 1987. Thirty-one patients were identified with a mean follow-up time of 41 months. Three patients had suprarenal aneurysms and four had ruptured abdominal aneurysms. Average tube graft insertion time was 17 minutes and required 0.9 units of transfused blood. There were two postoperative deaths (6 percent), both secondary to myocardial infarction. None of the patients with ruptured or suprarenal aneurysms died. No patients had permanent renal or neurologic deficits, and no instances of postoperative bleeding, wound infection, pseudoaneurysm formation, or graft migration were encountered. The sutureless intraluminal graft can be implanted easily and quickly and is safe for use in the abdominal aorta. It is particularly helpful in the management of suprarenal or ruptured abdominal aneurysms, in which speed is important, and in effecting technically difficult anastomoses to friable aortic tissue.

Adult↗
PubMed1986

Esophagogastrectomy. Successful palliation for esophageal carcinoma.

Although esophagogastrectomy offers the best chance for cure and alleviation of dysphagia in the treatment of esophageal carcinoma, the operative mortality and morbidity can be prohibitively high. To investigate means for reducing the rate of surgical complication, a study was made of a six-year series of 36 procedures involving 32 esophagogastrostomies and four colon interpositions. Patient survival rates were 60 percent at one year, 40 percent at two years, and 9 percent at five years with a mean survival of 22 months. Histology of the tumor did not significantly affect prognosis. The three operative mortalities were caused by pulmonary insufficiency in one overhydrated patient, and coagulopathy in two alcoholic patients with underlying liver disease. Anastomotic leakage, the precipitating factor for the majority of operative mortalities in the recent literature, occurred in one non-fatal case. This low incidence is linked to the implementation of steps to maximize blood supply and minimize tension on the anastomosis line. Anastomotic stricture was seen and easily dilated in three patients. The five cases of intra-esophageal tumor recurrence which occurred despite tumor-free margins may have been avoided by more extensive resection.

Adenocarcinoma↗