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Biomedical subjects

R G Lee

Publications and source records attributed to R G Lee.

At least 163 records · Page 9Linked to original sources
PubMed1984

A comparison of two cerebral perfusion tracers, N-isopropyl I-123 p-iodoamphetamine and I-123 HIPDM, in the human.

Both N-isopropyl I-123 p-iodoamphetamine (IMP) and I-123 HIPDM have been advocated as radiotracers for assessing regional cerebral perfusion. We compared the biodistribution of the two tracers in 19 patients without evidence of neurological disease. Following intravenous injection, both tracers accumulated initially in the lung. Early after injection the fraction of the total brain uptake was higher for I-123 HIPDM than for I-123 IMP. The peak brain activity for I-123 IMP was higher than for I-123 HIPDM . Brain activity was unchanged with both tracers between 30 and 60 min after injection. Tomographic images were similar in appearance for both tracers. No eye uptake greater than background was observed with either tracer in any patient at 2, 24, and 48 hr. I-123 IMP is superior for tomographic imaging because of its higher brain uptake, whereas I-123 HIPDM may be superior for studies performed during rapid changes in blood flow.

Amphetamines↗
PubMed1984

Upper gastrointestinal polyps in Gardner's syndrome.

Upper gastrointestinal polyps have been considered an uncommon finding in patients with Gardner's syndrome and familial polyposis coli. Investigators from Japan, however, have recently reported finding gastric and duodenal polyps in a high percentage of Japanese patients with these conditions. We endoscopically examined 11 affected members of the originally described Gardner's syndrome kindred to determine if upper gastrointestinal polyps also occurred in patients with Gardner's syndrome living in the United States. Six of the patients were found to have numerous small polyps of the gastric fundus and body. Polyp histology in 5 of the 6 patients was consistent with fundic gland hyperplasia. Biopsy specimens from the remaining patient demonstrated normal mucosa only. Another patient with no fundic polyps had a single antral polyp that was an adenoma. Eight patients exhibited small polyps of the duodenum. Biopsy specimens were obtained in 7 of the 8. All polyps biopsied were adenomas. The terminal ileum was examined by endoscopy in 9 of the 11 study patients. All 9 had ileal polyps, but the polyps were adenomas in 6 patients and lymphoid aggregates in 3 patients. The results indicate that upper gastrointestinal polyps are a common pleiotropic manifestation of the genetic defect responsible for Gardner's syndrome.

Adenoma↗
PubMed1984

The relationship of the eye uptake of N-isopropyl-p-[123I]iodoamphetamine to melanin production.

Eye uptake has been a potential concern with N-isopropyl-p-[123I]iodoamphetamine (I-123 IMP) because it has been observed in certain animal species. We have investigated the cause of the eye uptake and its relationship to melanin synthesis. In a 1-yr-old cynomolgus monkey, high concentration of the tracer was seen in the eyes regardless of the type of anesthesia (pentobarbital or ketamine) or the oral administration of Lugol's solution. The eye uptake at 24 hr after injection of I-123 IMP was equally high in an 8-yr-old rhesus monkey. The ratio of radioactivity in the eye of black compared with white albino mice was 10:1 at 30 min, 18:1 at 2 hr and 36:1 at 24 hr after injection of I- 123 IMP. No eye uptake above soft-tissue background was seen in five patients at 2, 24, and 48 hr after injection. I-123 IMP is avidly incorporated into melanocytes actively producing melanin, but substantially less in melanocytes where production of melanin has ceased as in the human eye.

Amphetamines↗
PubMed1983

Multicystic renal cell carcinoma.

This is a case report of a patient with cystic renal cell carcinoma that had all of the ultrasound and computed tomographic features of benign multicystic renal disease. Although this benign entity is a possibility in some patients, thick-wall cystic lesions of the kidney must be considered malignant until proven otherwise and surgery cannot be avoided.

Adenocarcinoma↗
PubMed1983

Peripheral hepatic artery embolization for primary and secondary hepatic neoplasms.

Eighteen patients underwent peripheral arterial embolization with Gelfoam powder for treatment of primary or metastatic hepatic neoplasms. Except for two cases in which the patients could not undergo long-term arterial infusion, all cases were treatment failures from intravenous chemotherapy, intra-arterial chemotherapy, or, in some cases, intra-arterial chemotherapy plus radiation therapy. Fourteen patients had good symptomatic relief from the procedure. Four of these patients are alive at 3, 5, 6, and 18 months following the procedure. Four patients died within 2 weeks following embolization, three of progression of disease and one of aspiration pneumonia. Of the patients showing symptomatic relief, 10 died of progression of cancer 2 to 14 months following embolization, with a median survival of 5 months. Based on the results in this small group of patients, it would seem that transcatheter hepatic dearterialization is often successful palliative therapy in patients who are not responsive to traditional therapies. Because of the low procedural morbidity, transcatheter embolization is superior to surgical dearterialization.

Carcinoma, Hepatocellular↗
PubMed1983

Hepatic artery embolization for metastatic endocrine-secreting tumors of the pancreas. Report of two cases.

Two patients with hormone-secreting metastatic tumors of the liver (carcinoid, islet cell) were treated with transcatheter arterial embolization. In both cases, occlusion of blood supply to the tumors was accomplished, resulting in cessation of the systemic symptoms. Arterial embolization provides another useful palliative therapy for hormone-secreting tumors of the liver.

Adenoma, Islet Cell↗
PubMed1982

Long latency reflexes to imposed displacements of the human wrist: dependence on duration of movement.

Reflex EMG responses to angular displacements of the wrist joint were recorded from 12 normal human volunteers. A mechanical stop was used to suddenly arrest displacements at varying times following the onset of the stimulus. With unrestricted movement of the handle, the EMG response consisted of an early component (M1) with a latency of 30-35 ms and a long-latency component (M2-3) beginning 55-65 ms after the onset of the displacement. When the displacements were arrested prior to a critical time occurring between 40 and 50 ms after the onset (mean of 44 ms), the M2-3 component of the response was not present. Increasing the duration of the displacement beyond this time resulted in a rapid increase in the size of M2-3. Facilitation provided by volitional intent to oppose the perturbation was not sufficient to generate an M2-3 response to either a brief, low velocity displacement produced by the torque motor or to a phasic, high velocity stretch produced by a tendon tap. The timing relationships between the onset latency of M2 and the minimum duration of displacement required to generate an M2-3 response are not easily reconciled with the notion that the segmentation of the EMG responses into components is mediated by repeated activation of the same central reflex pathway by phasic afferent bursts. Two mechanisms that could account for these results are either inhibition in response to the sudden stop of phasically-active "linking" interneurons which are part of the long latency pathway, or the loss of an essential convergent facilitatory input which serves to monitoring the continuation of the movement.

Adult↗
PubMed1982

Experimental transcatheter splenectomy using absolute ethanol.

Since ethanol is known to be effective for transcatheter infarction of the kidney, the authors evaluated it as an agent for splenic ablation in swine and dogs. Infarction was successful in 7 of 9 pigs and 4 of 5 dogs. Controlled segmental infarction using flow-directed balloon catheters was attempted and was successful in 3 pigs and 2 dogs. The maximum blood ethanol level was 78 mg/100 ml, and by 15 minutes after injection it was less than or equal to 20 mg/100 ml. There was no evidence of pancreatic or hepatic injury at autopsy. The authors conclude that with careful catheter positioning, controlled total or partial infarction of the spleen can be safely performed with absolute ethanol without risk of abscess formation, pneumonia, or significant damage to other organs.

Animals↗
PubMed1982

Comparison of N-isopropyl (I-123) p-iodoamphetamine brain scans using Anger camera scintigraphy and single-photon emission tomography.

N-isopropyl (I-123) p-iodoamphetamine (IMP), which is extracted by the brain in proportion to regional blood flow, has been shown to be useful with single-photon emission tomography (SPECT) in the assessment of pathologic states related to blood flow. Because emission tomographic equipment is not yet available at most hospitals, the authors compared IMP brain images obtained with an Anger camera with those obtained by SPECT to determine the usefulness of IMP scintigraphy. Thirty-nine pairs of studies were performed on 12 control patients, 14 patients with stroke, three patients with tumors, and a miscellaneous group of eight patients. Planar scintigraphy showed good correlation with SPECT in determining the presence or absence of abnormality in all patients except one with a very small brain stem infarction that was not detected by planar imaging. Anger images showed poor contrast resolution compared with SPECT images. It is thus expected that SPECT will result in better lesion detection when smaller lesions are studied. Planar scintigraphy is not capable of providing quantitative measurement of regional cerebral blood flow.

Amphetamines↗
PubMed1982

N-isopropyl(I-123)p-iodoamphetamine brain scans with single-photon emission tomography: discordance with transmission computed tomography.

Transmission computed tomography (CT) brain scans were compared with N-isopropyl (I-123)-p-iodoamphetamine (IMP) single-photon emission computed tomography (SPECT) brain scans to determine if there was a correlation between morphology, as seen on CT, and cerebral perfusion changes detected by IMP SPECT. In 12 patients with acute stroke, four showed no discordance between the edema seen on CT and perfusion deficits seen on IMP SPECT; five had positive IMP scans while initial CT scans were negative and follow-up CT scans demonstrated edema in the region of perfusion deficit seen on the IMP scans; and in four patients, the average perfusion deficit was 2.3 times greater than the edema shown on CT at 2 cm above the canthal-meatal line. In nine control patients, there was a 2.3% difference in IMP activity between the right and left hemispheres. The 12 stroke patients showed 30.3% less IMP activity in the abnormal hemisphere compared with the normal side. Three patients, one with temporal lobe seizure, one with hemiballismus, and the third with idiopathic intention tumor, had 54% greater IMP activity on the side of movement or seizure than on the normal side. The discordance between IMP and CT scans was clearly demonstrated in cases in which CT showed no abnormality but IMP provided information on function, reflected in increased or decreased cerebral perfusion.

Amphetamines↗
PubMed1981

D-penicillamine treatment improves survival in primary biliary cirrhosis.

The copper-chelating, immunological, and antifibrotic effects of D-penicillamine indicated that it might be suitable for the treatment of primary biliary cirrhosis (PBC). In a randomised clinical trail, 55 PBC patients received penicillamine (600 mg daily), and 32 received a placebo. Drug reactions developed in 16 patients on penicillamine. All deaths occurred in patients with stage 3 or 4 (late stage) liver histology on entry to the study. 5 (14%) of 37 penicillamine-treated patients and 10 (43%) of 23 placebo patients have died (p less than 0.01). Improvement in survival only became evident after 18 months. Survivors in the penicillamine group demonstrated a significant fall in serum aspartate transaminase, serum immunoglobulins, and liver copper concentrations. On follow-up liver biopsy 12-72 months (median 33) after joining the study, 21% of penicillamine-treated patients had less pronounced inflammation and piecemeal necrosis, whereas there had been no improvement in patients on placebo (p less than 0.02). Penicillamine did not retard the histological evolution of the liver disease from the early prefibrotic stages to the late fibrotic or cirrhotic stages. Both the copper-chelating and immunological effects of penicillamine are probably important in improving survival. The excellent prognosis of patients with PBC in its early histological stages, and the failure of penicillamine to prevent histological progression from early to late stages, suggests that penicillamine treatment should not be given to patients with PBC in the early (stage 1 or 2) histological phase of the disease. Penicillamine treatment is recommended in patients once liver biopsy has demonstrated histological results typical of late stage 3 or 4 PBC.

Antigen-Antibody Complex↗
PubMed1981

Resetting of tremor by mechanical perturbations: a comparison of essential tremor and parkinsonian tremor.

With the use of a computer-controlled torque motor, experiments were carried out on 11 patients with essential tremor and 13 with parkinsonian tremor to determine the effect of mechanical displacements at the wrist joint on the established pattern of tremor. Analysis of the timing of tremor bursts in electromyographic recordings before and following the stimuli revealed that the phase of essential tremor could be readily reset by external perturbations. In the majority of the parkinsonian patients the same type of stimuli had very little effect on the pattern of tremor. Differences between predicted and actual times of occurrence of tremor bursts following the stimuli were used to calculate a normalized resetting index, with 0 representing no resetting and 1, complete resetting. For the patients with essential tremor the mean resetting index was 0.64 +/- 0.14 (SD); for the parkinsonian patients the generation of essential tremor. Reflex mechanisms are less important in parkinsonian tremor, which is more likely dependent on oscillations originating in the central nervous system.

Biomechanical Phenomena↗