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Biomedical subjects

R Segal

Publications and source records attributed to R Segal.

At least 199 records · Page 11Linked to original sources
PubMed1985

Neurogenic hypertension: etiology and surgical treatment. II. Observations in an experimental nonhuman primate model.

In a companion paper (Ann Surg 1985; 201(3):391-398), clinical data which suggest that neurogenic hypertension may be caused by arterial compression of the left medulla oblongata was presented. A chronic pathophysiologic animal model of neurogenic hypertension using a substitute for arterial pulsation, the neurovascular compression simulator (NCS), was developed. This paper presents data that demonstrate how development of hypertension in a nonhuman primate baboon (5 subject animals, 5 control animals) can be caused by the NCS, and the blood pressure can subsequently return to normal following cessation of NCS activity. These experiments show that pulsatile compression of the left ventrolateral medulla oblongata results in cardiovascular changes consistent with the sequence found in human neurogenic hypertension. Arteriosclerosis and arterial ectasia in the human contribute to arterial elongation and looping at the base of the brain. An arterial loop, by causing pulsatile compression of neural structures, elicits an increase in blood pressure initiated by an increase in cardiac output. This may be due to interference with the autonomic control of the heart and/or by alteration of the relative capacitance of the vascular system.

Animals↗
PubMed1985

Drug choice as a problem-solving process.

A model of the drug prescribing process, which incorporates prescribers' personal values about treatment outcomes and beliefs about treatment effects, was tested under actual clinical conditions. Forty physicians were given two fictional case histories and six disguised case histories of patients whom they had recently treated for hypertension or maturity-onset diabetes mellitus. The physicians completed questionnaires based on each case history that measured 1) the beliefs about the probability that seven treatment-related outcomes would result from the prescribing of several alternative treatments and 2) the values placed on each outcome. The physicians were also asked, in an open-ended question, how they would treat the patient described in the case. The 40 physicians proposed 172 drug treatments that corresponded to treatment alternatives for which beliefs about treatment effects had been measured. The model correctly predicted 1) prescribing intent in 81% of hypertension cases and in 87% of the diabetes cases and 2) actual prescribing in 76% of hypertension cases and in 70% of the diabetes cases, significantly more than would be expected at random (P less than 0.01). The prescribing model appears useful for predicting drug choices for the outpatient treatment of hypertension and diabetes by resident physicians.

Attitude of Health Personnel↗
PubMed1985

Mechanical and metallurgical properties of carotid artery clamps.

The mechanical and metallurgical properties of carotid artery clamps were evaluated. The pressure plate retreat propensity, metallurgical composition, surface morphology, magnetic properties, and corrosion resistance of the Crutchfield, Selverstone, Salibi, and Kindt clamps were tested. None of the clamps showed evidence of pressure plate retreat. The clamps differed significantly in their composition, surface cleanliness, magnetic properties, and corrosion resistance. The Crutchfield clamp was the only one manufactured from an ASTM-ANSI-approved implantable stainless steel (AISI 316) and the only clamp in which the surfaces were clean and free of debris. The Selverstone clamp was made principally from AISI 304 stainless steel, as was one Salibi clamp. The pressure plate on another Salibi clamp was made from a 1% chromium and 1% manganese steel. Machining and surface debris consisting principally of aluminum, silicon, and sulfur was abundant on the Selverstone and Salibi clamps. The Kindt clamp was manufactured from AISI 301 stainless steel with a silicate-aluminized outer coating. The Crutchfield and Selverstone clamps were essentially nonferromagnetic, whereas the Salibi and Kindt clamps were sensitive to magnetic flux. In the pitting potential corrosion test, the Crutchfield clamp demonstrated good corrosion resistance with a pitting potential of 310 mV and no surface corrosion or pitting by scanning electron microscopy examination. The Selverstone clamp had lower pitting potentials and showed various degrees of corrosion and surface pitting by scanning electron microscopy. The Salibi pressure plate had a very low pitting potential of -525 mV and showed severe corrosion. By metallurgical criteria, only the Crutchfield clamp is suitable for long term implantation.

Animals↗
PubMed1985

Combined-modality treatment of inoperable lung cancer (i.v. immunotherapy, chemotherapy, and radiotherapy).

Patients with inoperable non-small cell carcinoma of the bronchus were treated by iv methanol extraction residue of bacillus Calmette-Guérin (MER) followed by combination chemotherapy with methotrexate, doxorubicin, cyclophosphamide, and lomustine (MACC). Radiotherapy was added in patients with localized disease. MER was given iv in four weekly courses. The dose ranged between 0.1 and 0.8 mg/m2/course and was determined according to the skin reactivity to MER. None of the 19 patients treated with iv MER had an objective tumor response during immunotherapy. Five of 16 evaluable patients receiving MACC (31%) achieved partial response. The overall median survival for all 17 patients treated was 11 months according to the protocol. During immunotherapy the following side effects were observed: all patients had fever and chills and most had malaise, nausea and/or vomiting, and headache. Transient abnormalities of liver function tests were found in six patients, and in one patient roentgenographic changes suggestive of lung granulomas were seen. The side effects were more severe during the first course than in the further treatments. Side effects of the MACC combination were comparable to those observed in previously reported studies. Immunological monitoring performed during immunotherapy revealed that iv MER had an unfavorable effect on the immune system. Following four courses there was a decrease in the in vivo skin reactivity to MER and to five recall antigens. Twenty-four hours after the initiation of iv MER there was a tendency for decrease in the lymphoproliferation to phytohemagglutinin, an increase in the indices of the adherent cell suppressor system and the prostaglandin-related suppressor system, and an increase in the percentage of adherent mononuclear cells. No consistent changes in serum lysozyme were found. A transient increase in the total number of peripheral blood leukocytes and a decrease in the number of lymphocytes were noticed 24 hours after iv MER. Taking into account the results of the immunological studies and the overall therapeutic results, we do not feel justified in continuing to use this combined modality treatment.

Adenocarcinoma↗
PubMed1984

The hemolytic activity of citral: evidence for free radical participation.

In the present investigation the hemolytic properties of citral were examined. Tests with different concentrations of citral showed that hemolysis of rat erythrocytes commenced after a lag period the length of which depended on the concentration of the hemolysin and tended to 100% hemolysis. Comparison of the characteristics of the hemolysis induced by high and low citral concentrations, indicated that two mechanisms are involved--a non specific steroid--terpenoid or glutathione depletion mechanism dominating at high citral concentrations and a free radical mechanism dominating at low citral concentrations. Experiments performed with various free radical scavengers indicate that 1O2 might be involved.

Acyclic Monoterpenes↗
PubMed1984

Intracranial clips: an examination of the devices used for aneurysm surgery.

A properly functioning aneurysm clip is of paramount importance in the surgical ablation of intracranial aneurysms. An appropriate match between the closing force needed to ablate an aneurysm and the force exerted by the aneurysm clip must be achieved. In this study, the opening and closing forces exerted by several commonly used aneurysm clips were tested. There was a strong correlation between the classification of the clips, according to the Dujovny system, and their mechanical behavior. Minimal variability among different lots of the same clip type and minimal hysteresis were generally exhibited by the alpha mobile fulcrum class clips, such as the Yasargil, Vari-Angle McFadden, Scoville, and Mayfield clips. Significant exceptions included several types of Mayfield and Drake clips. In contrast, pivot class clips generally showed twice as much lot variability among different lots, as well as a significant amount of hysteresis. Clips of this class include the Vari-Angle, Heifetz, and Pivot clips. Because significant variations in clip force exist and because several other factors can compound these differences, it is suggested that aneurysm clips be individually tested for their closing forces before they are used in an operation.

Humans↗
PubMed1984

Prostaglandin-related and adherent cell suppressor system in apparently cured Hodgkin's disease patients.

Lymphocyte proliferation (LP) by phytohemagglutinin (PHA) and two suppressor systems of mononuclear cells was investigated in 22 patients with Hodgkin's disease (HD) who were apparently cured at the time of study. The results were compared with those obtained in healthy controls and in a group of patients with inoperable carcinoma of the bronchus. The prostaglandin-related suppressor cell system ( PGSS ) was tested by adding 1 microgram/ml indomethacin to the mononuclear leukocyte cultures. The adherent cell suppressor system ( ACSS ) was tested by removal of the adherent cells on plastic petri dishes. The PGSS index of suppression was defined as the ratio of LP by PHA with indomethacin to LP without indomethacin. The ACSS index was defined as the ratio of the nonadherent cell LP to the total LP. The mean PGSS index in HD patients (1.1 +/- 0.25) was significantly higher (p less than 0.01) than in healthy controls (0.94 +/- 0.2). The ACSS index in HD patients (1.08 +/- 0.47) was also higher (p less than 0.02) than in controls. The LP by PHA value in HD patients (23,908 +/- 14,770 cpm) was significantly lower (p less than 0.001) than in controls (47,151 +/- 17,706 cpm). ACSS values in bronchogenic cancer patients were lower than in HD patients. The LP by PHA value was significantly lower in HD patients compared with bronchogenic carcinoma patients (p less than 0.02). HD patients who had a PGSS index of 1.3 or higher had a significantly lower LP value than those with a PGSS index lower than 1.3.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1984

Double pylorus or antro-bulbar fistula.

A patient suffering from rheumatoid arthritis and a gastric ulcer was found endoscopically to have a double pylorus. One year later the two apertures were found to be fused and appeared endoscopically like a deformed pylorus. We suggest that this lesion, which is usually acquired but may sometimes be congenital, would be better called antro-bulbar fistula.

Adult↗
PubMed1983

Trichothecene-induced hemolysis. I. The hemolytic activity of T-2 toxin.

In the present investigation, the hemolytic properties of T-2 toxin were examined. Tests with different concentrations of T-2 toxin showed that essentially complete hemolysis of rat erythrocytes commenced after a lag period, the length of which depended on the concentration of toxin. Comparison of the characteristics of hemolysis caused by T-2 toxin, saponins, H2O2, and polyoxyethylene surfactants showed great similarity between T-2 toxin and the latter two which proceed by a free radical mechanism. The same mechanism was suggested for hemolysis caused by T-2 toxin on the basis of the additional following observations: (1) darkness inhibited hemolysis; (2) specific free radical scavengers, i.e., vitamin E, mannitol, and histidine, inhibited hemolysis caused by T-2 toxin.

Animals↗
PubMed1983

Hemolysis caused by cetomacrogol 1000: evidence for hydroxyl radical participation.

The mechanism of cetomacrogol 1000-induced hemolysis was investigated. Previous conclusions that peroxides are involved in the hemolytic process were confirmed. The possibility that hydrogen peroxide, superoxide, hydroxyl radical, or singlet oxygen, which are known to induce hemolysis, are involved in cetomacrogol 1000-induced hemolysis was tested by using specific inhibitors and inactivators. The hydroxyl radical (OH.) was shown to be the only apparent oxygen species involved in cetomacrogol 1000-induced hemolysis. Its contribution to the hemolytic potency of the surfactant is approximately 30%.

Animals↗
PubMed1983

Mechanical and metallurgical properties of vascular clips designed for temporary use.

Six commonly used surgical clips (Kleinert-Kutz, Pivot, Vari-Angle, Yasargil, Biemer, and Acland) that have been designated by their manufacturer as being suitable for temporary occlusion were studied in terms of their mechanical and metallurgical properties. Opening and closing forces were determined for all of the clips. Significant variations in clip force with respect to blade gap were found in all of the pivot-type clips. Metallurgical testing showed that all six clips exhibited properties that contraindicate long-term implantation.

Corrosion↗