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Biomedical subjects

R Buchanan

Publications and source records attributed to R Buchanan.

At least 19 recordsLinked to original sources
PubMed1992

Effects of alprazolam on pituitary-adrenal and catecholaminergic responses to metabolic stress in humans.

Concurrent effects of benzodiazepines on stress-induced activation of the three classical "stress" systems: pituitary-adrenal, adrenomedullary, and sympathoneural systems have not been extensively investigated in humans. In the present study, the effects of alprazolam (1.5 mg) on plasma levels of adrenocorticotropin hormone (ACTH), epinephrine, norepinephrine, dihydroxyphenylglycol (DHPG, the intraneuronal metabolite of norepinephrine), and mood states were examined in 10 healthy volunteers undergoing glucoprivic stress. Glucoprivic stress was induced by intravenous administration of the glucose analog, 2-deoxyglucose (2DG), at a dose (50 mg/kg) that impairs cellular glucose metabolism and produces a state comparable to hypoglycemia. Alprazolam and 2DG were administered in a double-blind, placebo-controlled manner. 2DG produced robust elevations in plasma ACTH and epinephrine levels, modest elevations in plasma norepinephrine levels, and decreases in plasma DHPG levels. Alprazolam significantly attenuated the 2DG-induced increases in plasma ACTH and epinephrine, but did not significantly effect plasma norepinephrine and DHPG. These data suggest that benzodiazepines attenuate metabolic stress-induced activation of the pituitary-adrenal and adrenomedullary systems but do not effect 2DG-related effects on peripheral sympathoneural function. The possible mechanisms involved are discussed.

Adrenocorticotropic Hormone↗
PubMed1992

Limbic system abnormalities identified in schizophrenia using positron emission tomography with fluorodeoxyglucose and neocortical alterations with deficit syndrome.

A hypothesis of psychosis localization in schizophrenia was derived from studying metabolic alterations in rat brain in response to phencyclidine hydrochloride administration. Since phencyclidine and its selective agonist dizocilpine maleate (MK801) induced overlapping and long-lasting metabolic alterations predominantly in limbic areas, the hypothesis developed that schizophrenic patients with psychosis would evidence functional abnormalities in limbic circuits compared with normal controls. Accordingly, 12 actively psychotic, drug-free patients with schizophrenia and matched normal controls underwent functional brain scans using positron emission tomography and fluorodeoxyglucose. Regions of interest were identified on five matched axial slices in each patient and control subject, and average metabolic rates were calculated. Patients with schizophrenia showed a significantly lower regional cerebral metabolic rate of glucose in the hippocampus and the anterior cingulate cortex than did normal controls, but not in neocortical areas or in the extrapyramidal system. When the group of schizophrenic patients was divided into deficit and nondeficit types, a preliminary exploratory analysis suggested thalamic, frontal, and parietal cortical hypometabolism in the deficit subgroup, with normal metabolism in the nondeficit patient group in those areas; in contrast, hippocampal and anterior cingulate cortical metabolism was reduced in both deficit and nondeficit subtypes. These results suggest that the limbic system, especially the hippocampus, is functionally involved in schizophrenic psychosis and that different manifestations of schizophrenia may involve different neuronal circuits.

Adolescent↗
PubMed1992

Loco-regional recurrence and survival after wide local excision, radiotherapy and axillary clearance for early breast cancer.

After breast conservation for early breast cancer which comprised wide local excision, axillary clearance and radiotherapy to the breast, 145 women have been followed prospectively for a median of 42 months. Local recurrence occurred in 11 (7%) and axillary recurrence in three (2%). Distant recurrence has occurred in 32 and accounted for 80% of all first recurrences. Local treatment failure has occurred in three women and would not have been prevented by mastectomy. Loco-regional recurrence in the absence of preceding or synchronous distant disease was unusual and did not pose a significant clinical problem.

Adult↗
PubMed1991

In vitro vs in vivo corrosion analyses of two alloys.

The in vitro and in vivo corrosion characteristics of two alloys, cast Co-Cr-Mo (ASTM F75) and wrought Ni-Cr-Mo, were evaluated using electro-chemical corrosion analysis. Two in vitro electrolytic solutions were utilized, an isotonic saline solution consisting of 0.9 w/o NaCl in distilled water and an isotonic saline solution with 10 v/o sterile calf serum. The in vivo environment was created by implanting cylindrically shaped specimens of each alloy into the back muscles of New Zealand white rabbits. Cyclic anodic and cathodic polarization curves were generated for the three test conditions and subsequently were compared. Anodic curves conducted using the isotonic saline and isotonic saline plus serum electrolyte solutions were very similar to the anodic curves generated for the implanted alloy specimens for both alloys. The corrosion rates predicted from the in vitro and in vivo cathodic polarization curves were not statistically different for the three test conditions. Overall, the corrosion data generated using the in vitro environmental conditions adequately predicted the in vivo corrosion behavior of the cast Co-Cr-Mo and wrought Ni-Cr-Mo alloys.

Animals↗
PubMed1990

Sarcomatoid variant of anaplastic large-cell Ki-1 lymphoma.

Although anaplastic large-cell Ki-1 lymphomas can mimic a variety of tumors, a correct diagnosis is usually not difficult to reach if it is recognized that lymphoma cells can assume bizarre and pleomorphic appearances and that the pattern of growth can be purely sinusoidal. We report a unique case of a 45-year-old man presenting with a leg lesion that showed sarcomatoid growth patterns. The subcutaneous/dermal tumor displayed a myxoid stroma reminiscent of myxoid malignant fibrous histiocytoma. In a subsequent lymph node biopsy, a well-developed storiform pattern was formed by interweaving fascicles of plump spindle and oval neoplastic cells, reminiscent of pleomorphic/storiform type of malignant fibrous histiocytoma. The lymphoid nature of the tumor cells was documented by immunoreactivity for leukocyte common antigen, Ki-1 antigen, and the T-cell marker UCHL1. We conclude that the presence of a storiform or myxoid pattern does not disqualify the diagnosis of lymphoma; this possibility should always be pursued in pleomorphic tumors because the treatment is substantially different from that for sarcoma, carcinoma, or melanoma.

Antibodies, Monoclonal↗
PubMed1989

Two ways to assess problems of evaluating third- and fourth-year medical students: a case study.

Clinical faculty commonly acknowledge that they have difficulty evaluating third- and fourth-year medical students. The faculty and administration of the Louisiana State University (LSU) School of Medicine in New Orleans conducted pilot tests of two types of materials to assess these problems as part of the Clinical Evaluation Program undertaken by the Association of American Medical Colleges in 1984-1985. The two types of materials--questionnaires and the Problem-Case Analysis--were developed by the staff of the AAMC program and used by the LSU Department of Medicine and the Department of Obstetrics and Gynecology to identify problems in the process of evaluating clerks. Furthermore, the two methods proved complementary: both methods identified some of the same problems and each identified problems not identified by the other. Handling difficult students was the single problem identified by both methods in both departments. The questionnaires permit a simple method of collecting data about a broad range of problems. The Problem-Case Analysis, on the other hand, requires more time but evokes possible causes and alternative solutions, as well as identifying the problems. Improvement plans were developed by each department to address the problems that surfaced.

Education, Medical, Undergraduate↗
PubMed1987

Lupus and non-lupus cutaneous manifestations in systemic lupus erythematosus.

Mucocutaneous manifestations occur frequently in systemic lupus erythematosus (SLE). Common non-lupus dermatoses may be confused with lupus rashes, with important clinical consequences. A study of 84 consecutive patients with SLE was performed to determine the comparative frequency of lupus and non-lupus mucocutaneous abnormalities, the comparative sensitivity of routine histology and immunofluorescence in the diagnosis of lupus rashes, and the association of skin manifestations with other clinical and serological features. Thirty-five patients had dermatoses attributable to SLE (mean 3.7 per patient) and 58 had dermatoses which were not directly attributable to SLE (mean 2.1 per patient), highlighting the need for accurate diagnosis of skin rashes in SLE patients. Routine histology confirmed the clinical diagnosis of typical cutaneous lupus in 100% of malar lupus rashes and in approximately 90% of subacute cutaneous and discoid lupus rashes. Direct immunofluorescence of the affected skin provided supportive evidence of cutaneous lupus in 60% of malar lupus rashes and approximately 50% of subacute cutaneous and discoid lupus rashes. This reaffirmed the poor sensitivity of immunofluorescence, compared with routine histology, in the diagnosis of lupus rashes. The association of subacute cutaneous lupus with anti-Ro antibodies was confirmed.

Biopsy↗
PubMed1987

Surgery after initial chemotherapy for localized small-cell carcinoma of the lung.

Despite the high response rates induced by chemotherapy, many patients with limited small-cell lung cancer (SCLC) relapse at the site of primary disease. Failure of radiotherapy to overcome this has led to the use of surgery as part of a combined modality approach. Between December 1981 and December 1985, 189 patients with SCLC were assessed for suitability for surgery after an initial three cycles of chemotherapy (doxorubicin, cyclophosphamide, and etoposide). Fifty-seven were found to have limited disease, and of these, 19 were ineligible or unfit for surgery. Of the 38 eligible patients, 84% had an objective response to three cycles of chemotherapy and 25 were deemed suitable for surgery after restaging. At thoracotomy, four were inoperable, nine had a lobectomy, and 12 had a pneumonectomy. There was no evidence of viable SCLC in four resection specimens (one stage 1, two stage 2, one stage 3 at presentation), no viable SCLC but an entirely separate focus of viable poorly differentiated squamous carcinoma (SqLC) in one, and the remaining specimens contained viable SCLC. Survival of patients selected to undergo tumor resection was excellent (median survival, 33 months; plateau phase, 48% alive at 3 to 5 years), but survival of the entire group with limited SCLC was not dissimilar from that reported in previous series of limited-stage tumor treated with chemotherapy alone. Long-term survival appeared to be largely restricted to those with no evidence of viable SCLC at surgery (no viable SCLC, zero of five relapsed; viable SCLC, 13 of 16 relapsed and/or died). This prospective study confirms the feasibility of the combined modality approach, but suggests that any improvement in overall survival is likely to be small. Until the results from multicenter randomized trials are available, surgery, as part of a combined modality program, should be regarded as experimental.

Actuarial Analysis↗
PubMed1979

Abortion associated with intrauterine infection by candida albicans. Case report.

A 27-year-old patient who became pregnant whilst fitted with an intrauterine contraceptive device developed an intrauterine Candida albicans infection and aborted. The diagnostic (and other inconspicuous) features of C. Albicans infection in the fetus are described. The presence of the intrauterine contraceptive device may have predisposed to the establishment of the infection.

Abortion, Spontaneous↗