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Biomedical subjects

M Simons

Publications and source records attributed to M Simons.

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

Coronary vasoconstriction and catecholamine cardiomyopathy.

Norepinephrine (NE) causes extensive myocardial injury in the rabbit. To investigate a potential mechanism we measured coronary blood flow with radioactive microspheres. Coronary resistance and oxygen demand (heart rate-blood pressure double product) were calculated. Severity of injury was determined by semiquantitative histologic evaluation. Changes resulting from NE infusion were determined in animals with or without alpha-receptor blockade with phentolamine (10 mg). In all animals oxygen demand remained constant. Coronary blood flow (ml/gm/min) was 2.66 at the beginning of the experiment, rose to 3.46 after 3 minutes of NE infusion (p less than 0.05), then declined to baseline values (2.33) after 10 minutes. However, coronary blood flow was sharply lower than baseline (1.51; p less than 0.05) after 40 minutes of infusion. Coronary resistance rose progressively from baseline values of 40.9 (units) to 74.8 at 40 minutes (p less than 0.05). Animals given phentolamine manifested none of these changes. Control subjects infused with saline solution showed no significant changes in coronary blood flow or coronary resistance. Animals pretreated with phentolamine had minimal histologic damage at 48 hours compared with NE alone (p less than 0.01). We conclude that NE induces sustained coronary vasoconstriction in the rabbit and that reduced coronary blood flow may contribute to the pathogenesis of NE cardiomyopathy in this species.

Animals↗
PubMed1983

Testicular arterial perfusion in varicocele: the role of rapid sequence scintigraphy with technetium in varicocele evaluation.

Rapid sequence scintigraphy was used to study testicular arterial perfusion and venous stasis in 53 patients with varicocele-associated infertility, 17 with idiopathic testicular failure and 9 treated for varicocele. Arterial blood supply to the diseased testicle was decreased in 63 per cent of the patients with subclinical or low grade varicocele compared to 18 per cent with idiopathic testicular failure. In the majority of cases the disturbance of perfusion disappeared immediately after interruption of retrograde blood flow in the internal spermatic vein by transcatheter embolization, whereas persistently impaired perfusion was found in a few cases with no improvement of semen quality after treatment. Venous stasis was found in only 18 per cent of the patients with low grade varicocele compared to 88 per cent with large varicoceles. It is suggested that impaired arterial blood supply rather than venous stasis is the pathogenic factor in epididymo-testicular dysfunction associated with low grade varicocele.

Humans↗
PubMed1983

Evaluation of 99mTc-dimercaptosuccinic acid renal uptake as an index of individual kidney function after acute ureteral obstruction and desobstruction. An experimental study in rats.

The evolution of the 99mTc-dimercaptosuccinic acid (DMSA) renal uptake is followed after ligation of the right ureter in rats. The DMSA uptake falls rapidly from 35% before ligation to 13% after 24 h, and decreases further to 1.5% after 31 days. The ligated ureter was desobstructed after 10, 17, 24 and 31 days, respectively, DMSA uptake was controlled 4, 11 and 18 days after desobstruction. In the first group, deobstruction after 10 days, the DMSA uptake rose from 7 to 15%, while in the fourth group it rose from 1.5 to 2%. It is concluded that DMSA uptake provides a reliable index for renal function after acute urinary tract obstruction in rats. If the DMSA uptake has fallen below 4% very little renal function can be expected to be regained, whereas above 4% the function can improve considerably.

Acute Disease↗
PubMed1982

Visualization of muscles involved in unilateral tremor using 13N-ammonia and positron emission tomography.

Using positron emission computerized tomography (PCT), a high uptake of IV injected 13N-ammonia was observed in the muscles of the right forearm and leg of a patient with a rightsided static tremor. In some muscles the concentration of 13NH3 was 8.5 times higher than in the symmetrical normal limb. Confrontation of the clinical, neurological, and electromyographic findings with the results of the PCT proved that the muscles with the high uptake corresponded to the muscles responsible for the tremulous movements. There is strong evidence that the high uptake of 13NH3 was related to the increased blood flow produced by the continuous rhythmic exercise of the muscles involved in the tremor. To our knowledge a similar observation has not been described before. It is suggested that the combined use of suitable positron emitters and PCT might provide a valuable tool for the noninvasive study of perfusion of individual skeletal muscles.

Aged↗
PubMed1982

A clinical study of 99mTechnetium dimercaptosuccinic acid uptake in obstructed kidneys: comparison with the creatinine clearance.

We studied 17 hydronephrotic kidneys owing to stenosis of the pyeloureteral junction. Preoperative uptake of 99mtechnetium dimercaptosuccinic acid was compared to early postoperative unilateral creatinine clearance, measured by urine collection from the nephrostomy tube. An excellent correlation was found. Therefore, uptake of 99mtechnetium dimercaptosuccinic acid represents a reliable parameter of renal function even in the presence of severe urinary tract obstruction. However, 99mtechnetium dimercaptosuccinic acid uptake should be measured more than 24 hours after injection of the tracer.

Adolescent↗
PubMed1982

Ga-67 imaging in Hodgkin's disease.

In order to answer the question if Ga-67 imaging has a practical utility for the management of the patient with Hodgkin's disease, 108 scans performed on 60 patients were reviewed. When used during the initial staging of the disease or during restaging because of recurrences, Ga-67 imaging-at least in our experience-gave many false negative results in the cervical, axillary and inguinal areas, whereas the majority of true positive scans was found at the mediastinal level (including the lower mediastinum), and also in the lung parenchyma and the upper epigastric regions. Because of its lack of sensitivity, Ga-67 imaging cannot replace other staging procedures, but nevertheless is a valuable adjunctive test, as it can identify tumor localization that may have remained undetected by other methods. Fifty-four scans were performed to monitor treatment with radiation therapy or chemotherapeutic agents. Disappearance or decreases of Ga-67 uptake after treatment usually corresponded to a disappearance or regression of the tumor as ascertained by other methods. When the treatment was shown to be ineffective, Ga-67 uptake persisted or even became more prominent. When during follow-up, a new concentration of Ga-67 appeared at the original location or elsewhere, a relapse was extremely likely. However, one must be aware of false positive images. In our material, no correlation was found between the intensity of the Ga-67 uptake and the histological subtypes of Hodgkin's disease. Neither did we observe any relation to the blood sedimentation rate or serum iron levels.

False Negative Reactions↗
PubMed1982

Abnormal Tl-201 limb scan due to unilateral tremor.

A abnormal intra- and interextremity distribution pattern on Tl-201 was observed on the limb scan of a patient with a unilateral tremor. This is ascribed to the increased blood flow in the muscles responsible for the tremor. The suggestion is made that the existence of tremor should be considered as a possible explanation for unexpected abnormalities on Tl-201 limb scintigrams.

Aged↗
PubMed1982

Uptake of 13N-ammonia by human tumours as studied by positron emission tomography.

Tumour uptake of 13N-labelled ammonia was studied by means of positron emission computerised axial tomography in 46 patients with various extensive neoplastic conditions. Eleven of the patients have been followed sequentially before, during and after radio- and/or chemotherapeutic treatment. Substantial accumulation of 13NH3 (up to five times the amount found in comparable normal tissues) was noted in some cases of breast cancer and their metastases, as well as in soft tissue sarcomas, in malignant neck nodes secondary to head and neck tumours, in lung tumours and their metastases, in melanomas, in malignant lymphomas, in metastasis prostatic carcinoma and in the case of ovarian carcinoma examined. Little or no extra uptake of 13NH3 was found ion necrotic or non-malignant tumours or in primary brain tumours, or in some primary breast cancer which otherwise appeared well vascularized and actively growing. In those patients who were followed sequentially, 13NH3 uptake could be seen to decrease with tumour regression. However, during the course of a radiotherapeutic treatment a transitory increase of 13NH3 uptake could be observed. If the therapy had not been successful, 13NH3 uptake was found to persist after treatment. Uptake of 13NH3 in tumours is to be regarded as the result of a complex interaction of both circulatory and metabolic influences. Studies using more specific tracers of flow and tissue metabolism will probably help to unravel the contributory physiological components.

Aged↗
PubMed1979

JCAH equivalency: its effect on hospitals, labs, and the I&A program.

In reviewing the Joint Commission on Accreditation of Hospitals' acceptance of the CAP Inspection and Accreditation program, this article examines, for example, the effect of this acceptance on the cost of laboratory inspections, on the handling of so-called splinter laboratories, and on the I&A program. The author also reviews briefly current efforts to obtain state equivalency.

Accreditation↗
PubMed1975

Measurement of gastric blood flow with radioactive microspheres.

The validity of using radioactive microspheres (15 +/- 5-mum diameter) to measure gastric blood flow and its partition between gastric wall layers was investigated in anesthetized dogs with a chambered segment of gastric corpus. Total flow measured by a venous effluent technique demonstrated close correlation with microsphere-measured flow (r = 0.98, slope = 0.95) in 12 dogs given histamine, gastrin, or isoproterenol. In 12 histamine-stimulated dogs, mucosal flow measured by aminopyrine clearance and by microspheres also showed good agreement (r = 0.96, slope = 0.83). No evidence was found to indicate that microspheres altered hemodynamic or gastric function. In all experiments less than 1% of the total gastric radioactivity passed through arteriovenous shunts. The mucosa always contained a statistically adequate number of spheres (greater than 400), but the submucosa and muscularis frequently did not. Microspheres of all sizes mixed adequately in large arteries, but a significant difference was found in the distribution of 16- and 26 mum spheres between mucosa and submucosa, presumably because of streaming of the larger spheres past mucosal arteries. It was concluded that, with the techniques developed in our laboratory, microspheres could be a highly useful tool for quantitating gastric regional blood flow under a variety of experimental conditions.

Aminopyrine↗