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Biomedical subjects

A Alavi

Publications and source records attributed to A Alavi.

At least 379 records · Page 21Linked to original sources
PubMed1981

Studies of GI bleeding with scintigraphy and the influence of vasopressin.

The management of patients with gastrointestinal (GI) bleeding depends on accurate localization of the site of hemorrhage. Endoscopy and arteriography, although successful in achieving this goal in the majority of patients, are invasive and have other shortcomings. The introduction of the 99mTc-sulfur colloid technique has greatly simplified the evaluation and management of these patients. This test is useful in detecting and localizing the bleeding site in the lower GI tract. Scintigraphy is now used as the initial study of choice in patients with rectal bleeding. Advances made in angiography and nuclear medicine techniques also have resulted in improved management of patients. Conservative approaches succeed in controlling hemorrhage in most patients. Vasopressin is the most widely tested agent and has been adopted by many as the preferred preparation for this purpose. Before the introduction of the 99mTc-sulfur colloid technique, angiography was used to monitor the effectiveness of this drug, whether administered intravenously or intraarterially. With the use of scintigraphy and intravenous administration of vasopressin, these patients now can be managed noninvasively. Only when the intravenous Pitressin infusion fails to stop hemorrhage, is the intraarterial approach considered. Surgery is used as a last resort when these measures fail to stop the bleeding.

Colon, Sigmoid↗
PubMed1981

Mapping of functional activity in brain with 18F-fluoro-deoxyglucose.

The efficacy of using the 18F-fluoro-deoxyglucose (18F-DG) for measuring regional cerebral glucose utilization in man during functional activation is demonstrated. Normal male volunteers subjected to sensory stimuli (visual, auditory, tactile) exhibited focal increases in glucose metabolism in response to the stimulus. Unilateral visual hemifield stimulation caused the contralateral striate cortex to become more active metabolically than the striate cortex ipsilateral to the stimulated hemifield. Similarly, stroking of the fingers and hand of one arm with a brush produced an increase in metabolism in the contralateral postcentral gyrus compared to the homologous ipsilateral region. The auditory stimulus, which consisted of monaural listening to either a meaningful or nonmeaningful story, caused an increase in glucose metabolism in the right temporal cortex independent of which ear was stimulated. These results demonstrate that the 18F-DG technique is capable of providing functional maps in vivo in the human brain.

Adult↗
PubMed1981

Bone scintigraphy in diabetic osteoarthropathy.

Bone scans of patients with diabetic osteoarthropathy of the ankle and foot were characterized by a combination of diffuse and focal increased uptake, similar to that seen with hyperemia and reactive new bone formation. Scintigraphy showed more extensive abnormalities than radiography, with the scan abnormalities sometimes preceding the radiographic changes. The clinical and scintigraphic appearance of osteoarthropathy may improve following strict diabetic control and non-weight-bearing.

Adult↗
PubMed1981

Localization of gastrointestinal bleeding: superiority of 99mTc sulfur colloid compared with angiography.

Preliminary experience with technetium-99m sulfur colloid scintigraphy in 43 patients with lower gastrointestinal bleeding is described. Within minutes of the intravenous introduction of the radiopharmaceutical, a fraction of the injected activity extravasates at the bleeding site and is eliminated from the circulation. Because of rapid clearance of the radiopharmaceutical from the vascular pool by the reticuloendothelial system, a contrast develops between the site of bleeding and surrounding background. Based on animal experiments, bleeding rates as low as 0.05-0.1 ml/min can be detected with this technique. The sensitivity of this technique in the detection of the site of hemorrhage is significantly higher than arteriography or other techniques that use radioactive blood pool indicators. In this study all patients underwent both scintigraphy and arteriography within several hours. In 20 patients with negative scintigrams, arteriography showed no evidence of bleeding. In the other 23 patients with scintigraphic evidence of hemorrhage, arteriograms were positive for bleeding only in 10. In 19 of the 23 patients, a cause for bleeding was eventually established by other means. This technique appears to offer a simple, practical, and reliable approach to the evaluation of patients with lower gastrointestinal bleeding.

Angiography↗
PubMed1981

Diffuse cerebral swelling following head injuries in children: the syndrome of "malignant brain edema".

The commonest initial computerized tomography (CT) finding in head-injured children is bilateral diffuse cerebral swelling. Cerebral blood flow and CT density studies suggest that this swelling is due to cerebral hyperemia and increased blood volume, not to edema. The clinical history, course, and outcome of 63 children with this CT pattern are reviewed. Fourteen children had a Glasgow Coma Scale score of greater than 8; all made a complete recovery and follow-up CT scans were normal. Forty-nine children had Glasgow Coma Scale scores of 8 or less. Fifteen had a history of a lucid period following the initial unconsciousness. One of these children died of delayed brain swelling, the others recovered well with minimal neurological deficit. Thirty-four children were rendered immediately and continuously unconscious. There was a high incidence of second lesions on the CT scan, 50% of this group developed intracranial hypertension and five died. All of the others were in coma for periods ranging from weeks to months. Follow-up CT scans showed an extracerebral collection with a density of cerebrospinal fluid in 27% of the patients, and ventriculomegaly with large sulci in 35%, whereas this pattern was seen only once in those with a lucid period. The difference between those with and without a lucid period is related to the degree of primary diffuse impact injury to the white matter.

Adolescent↗
PubMed1981

Effect of electrical stimulation on diaphragmatic muscle used to enlarge right ventricle.

The effect of chronic electrical stimulation on muscle mass of pedicled diaphragmatic muscle grafts (DMGs) implanted into the right ventricle was studied in 21 dogs. Nineteen dogs, followed up to 70 days (mean, 34 days), were divided into three groups. In six dogs (control) the DMG was not stimulated. In six other dogs the DMG was stimulated at 50 stimuli/min with a fixed-rate unipolar pacemaker. In seven animals the graft was paced 1:1 with the dog's own rhythm with an R-wave synchronous pacemaker. Surface area of the DMG decreased 34% to 43% (P less than 0.05) in all dogs. DMG thickness increased in all dogs (P less than 0.05). The increase was 29% for control animals and 132% and 134% for the two paced groups. The volume of the DMG decreased 24% in the nonpaced animals but increased 29% and 51% in the two paced groups. Histologic studies showed some degree of muscle degeneration and atrophy in all grafts. However, morphometric studies showed relatively normal fiber diversity in paced grafts. Fiber size decreased in nonpaced grafts, indicating muscle atrophy. Perfusion studies with labeled microspheres and silicone injections demonstrated collateral circulation with the host ventricle as early as 28 days. However, total blood flow to DMGs implanted for 4 to 6 weeks averaged only 32% of the blood flow to normal ventricular myocardium. Chronic electrical stimulation of DMGs reduces muscle degeneration and atrophy and is associated with an increase in graft thickness and volume.

Animals↗
PubMed1980

Scintigraphic demonstration of acute gastrointestinal bleeding.

Acute gastrointestinal bleeding may be localized using noninvasive radionuclide methods. We have favored the use of technetium-99m sulfur colloid with sequential imaging because of the rapid clearance of background activity. Definition of the site of upper gastrointestinal bleeding, however, may be obscured by intense uptake of radioactivity by liver and spleen. The sensitivity of the method is such that the bleeding rates of 0.05-0.1 ml/min can be detected compared to a sensitivity of 0.5 ml/min for angiography.

Acute Disease↗
PubMed1980

Evaluation of infection in neutropenic patients with indium-111-labeled donor granulocytes.

Donor granulocytes, obtained by filtration leukophoresis, were labeled with In-111-oxine and injected into seven severely neutropenic patients. All patients were febrile, and presumed to have infection, although infection was eventually proved in only five. Excellent demonstration of infection was achieved in two patients, and fair localization in one. One negative scan became positive when repeated with sedimentation-derived cells from a different donor. This method may be useful in detecting infections in neutropenic patients.

Abscess↗
PubMed1980

99mTc-MDP uptake in nonosseous lesions.

A strikingly similar, massive, soft-tissue localization of 99mTc-MDP is described in three patients who had tumoral calcinosis, mild-alkali syndrome, and chronic renal failure, respectively. Although the basic mechanism for this phenomenon is unknown, some derangement of calcium and phosphate metabolism was present in all three cases.

Adult↗
PubMed1980

Local cerebral blood volume in head-injured patients. Determination by emission computed tomography of 99mTc-labeled red cells.

Local cerebral blood volume (CBV) was mapped in 10 normal subjects and in 30 patients after head injury. In normal subjects, the mean CBV was 4.34 ml/100 gm. The coefficient of variation was 12% for the group mean, and 3% for values obtained in duplicate studies of individuals. Patients with head injuries were divided into three groups according to the stage of their illness: acute illness, early recovery, and later recovery. Averages of mean CBV were within one standard deviation of normal. In contrast, consistent changes were found in serial studies of the mean CBV in the same patient. Compared to recovery values, levels of mean CBV measured soon after injury were reduced, largely at the expense of the gray-matter compartment. In five adults with predominantly unilateral lesions, there was an average early reduction in mean CBV and cerebral blood flow of 15% and 36%, respectively. In three children with diffuse brain swelling, there was an average early mean CBV reduction of 12%; a single child had early increased mean CBV at a time when intracranial pressure was high. Greater changes were seen in local CBV on individual sections. There were mixed zones of hypervolemia and hypovolemia in regions of infarction and intracerebral hematoma. Subdural hematomas had consistent medial margins of increased local CBV, representing dilated blood vessels of the underlying cortex. The presence and displacement of this hypervolemic zone were sensitive indicators of persistent subdural collection and mass effect, even when the collection was lucent to x-ray computed tomography.

Adolescent↗
PubMed1980

Role of bone scintigraphy in the evaluation and treatment of nonunited fractures: concise communication.

Seventy-seven patients with nonunited fractures underwent percutaneous low-grade, direct-current stimulation; the response was correlated with the scintigraphic findings obtained before the treatment. Two distinct patterns of osseous activity were noted: those with intense activity at the fracture site (Group 1) and those with a line of decreased activity surrounded by increased uptake on both sides (Group 2). The scintigrams that did not fit into either of the two patterns were considered as indeterminate (Group 3). Whereas 95% of the patients in Group 1 showed an excellent response to electric stimulation, none of the patients in Group 2 had evidence of healing. The response rate in the third group was 50%. On the basis of these preliminary data, bone scintigraphy is recommended as an important initial examination for the proper selection of patients for percutaneous electric stimulation.

Bone and Bones↗
PubMed1980

Colonic dysfunction in diabetes mellitus.

Colonic myoelectrical and motor activity were measured in 12 patients with diabetes mellitus. Diabetic patients with severe constipation were compared to diabetics with mild or no constipation. Gastric emptying and peripheral nerve conduction studies were performed in all patients. Normal subjects had a rapid increase in colonic spike and motor activity (P < 0.001) within the first 30-min postprandial period. Diabetic patients with mild constipation had a postprandial increase in colonic motility; however, the response was delayed to 60-90 min after eating. Diabetic patients with severe constipation had no postprandial increase in colonic motility. There was no correlation between colinic motility and gastric emptying of a liquid meal (r = 0.23) (P > 0.05) or peripheral nerve conduction (r = 0.36) (P > 0.05). Neostigmine (0.5 mg, intramuscularly) or metoclopramide (20 mg, intravenously) increased colonic spike (P < 0.005) and motor (P < 0.005) activity in all diabetic subjects regardless of their symptoms. These studies suggest that patients with diabetes mellitus and severe constipation may have an autonomic neuropathy which leads to an absent postprandial gastrocolonic response.

Action Potentials↗
PubMed1979

The [18F]fluorodeoxyglucose method for the measurement of local cerebral glucose utilization in man.

A method has been developed to measure local glucose consumption in the various structures of the brain in man with three-dimensional resolution. [18F]-2-deoxy-2-fluoro-D-glucose is used as a tracer for the exchange of glucose between plasma and brain and its phosphorylation by hexokinase in the tissue. A mathematical model and derived operational equation are used which enable local cerebral glucose consumption to be calculated in terms of the following measurable variables. An intravenous bolus of [18F]-2-deoxy-2-fluoro-D-glucose is given and the arterial specific activity monitored for a predetermined period of from 30 to 120 minutes. Starting at 30 minutes, the activity in a series of sections through the brain is determined with three-dimensional resolution by an emission tomographic scanner. The method was used to measure local cerebral glucose consumption in two normal volunteers. The values in gray matter structures range from 5.79 mg/100 g per minute in the cerebellar cortex to 10.27 in the visual cortex, whereas, in white matter structures, the values range from 3.64 mg/100 g per minute in the corpus callosum to 4.22 in the occipital lobe. Average values for gray matter, white matter, and whole brain metabolic rates, calculated as a weighted average based on the approximate volume of each structure, are 8.05, 3.80, and 5.90 mg/100 g per minute, respectively. The value of 5.9 mg/100 g per minute compares favorably with values previously reported.

Adult↗
PubMed1979

Successful lymph node transplantation in rats, with restoration of lymphatic function.

After doing a popliteal lymphadenectomy in rats, we were able to transfer a mass of inguinal nodes to the area, either on an island pedicle of the superficial epigastric vessels, or as a free flap by microvascular anastomoses. The transplants survived and at 7 days were able to entrap india ink particles, or particles of radioactive gold, injected in the distal part of the extremity.

Animals↗
PubMed1979

Effect of water and fat on gastric emptying of solid meals.

Gastric emptying of solid egg meals tagged with 99mtechnetium sulfur colloid was studied in 10 normal subjects and in 6 patients after truncal vagotomy, antrectomy, and gastrojejunostomy (Billroth II) for peptic ulcer disease. Technetium sulfur colloid was found to bind more firmly to cooked egg whites than did the water soluble marker DTPA. Water accelerated gastric emptying in Billroth II patients to a greater degree than in normal subjects, in whom the effect of water was minimal and transient. Fat inhibited solid emptying both in normals and in Billroth II patients. These findings suggest that in humans there are jejunal receptors for fat that may inhibit gastric emptying even following truncal vagotomy.

Eating↗
PubMed1978

Influence of histocompatibility and transplant site on survival.

Suggestions that endocrine tissue is privileged, in that it may not be as severely damaged by the allograft reaction, provided the stimulus for an evaluation of thyroid transplantation across various histocompatibility barriers and into a number of different recipient sites. Results of allografting reveal that Ag-B compatibility allows for prolonged survival of thyroid tissue (much longer than skin in the same histocompatibility combinations) in the following sites: intramuscular, intradermal, renal subcapsular, and anterior chamber. Only the intrasplenic site, however, did not allow survival of even weakly incompatible grafts. In addition, all recipients of thyroid allografts rejected subsequent donor strain skin grafts in an accelerated manner, attesting to the normal antigenicity of thyroid. This finding, that thyroid is a "relatively privileged" tissue, has not been reported previously and is encouraging, since it suggests the potential success of clinical transplantation of other endocrine tissue less easily replaced than thyroid by administration of naturally occurring of synthetic analogues. Further, mild immunosuppression may serve to prolong survivals of allografts of endocrine tissue such as parathyroid or pancreatic islets, especially if an immunologically privileged site is employed.

Animals↗
PubMed1978

Radiologic evaluation of the treatment of nonunion of fractures by electrical stimulation.

A procedure is described in which nonunion of fractures is treated by implantation of electrodes with direct electric current at the site of fracture. Of 107 patients treated with electrode stimulation, 71 (66%) healed. If one eliminates 9 cases of congenital pseudoarthrosis and 11 patients treated with only 10 microamperes of current, 70 of 87 patients (8095%) healed. Severe osteoporosis and sclerosis were common radiologic findings, but had no value in predicting which patients would respond to therapy.

Electric Stimulation Therapy↗