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Biomedical subjects

G Austin

Publications and source records attributed to G Austin.

At least 37 records · Page 2Linked to original sources
PubMed1985

Comparison of regional cerebral blood flow in TIA patients with and without occlusion or stenosis of major vessels.

The purpose of this study is to compare the background regional cerebral blood flow (rCBF) in TIA patients with and without angiographically demonstrable lesions. 147 TIA patients with severe stenosis or occlusion of major vessels supplying the brain (A group) were compared with a similar group without any arterial lesion demonstrable by angiography (B group). Their rCBFs were measured by the intravenous Xe133 technique. The average of mean rCBF (MrCBF) in (A) group (119 cases) with a mean age of 59.9 yrs was 50.1 +/- 12.3 ml/100g/m and the average of MrCBF in (B) group (31 cases) with a mean age of 59.3 years was 47.6 +/- 11.8 ml/100g/m. In spite of no angiographic lesion in (B) group, the MrCBF was lower in value than that in (A) group. The average of hemispheric rCBF (HrCBF) was approximately the same bilaterally in a control group (55.4 ml/100g/m), and even in (B) group there was no significant difference between the symptomatic side and the non-symptomatic side. In (A) group, HrCBF on the symptomatic side (48.1 ml/100g/m) was significantly lower on the average than that on the opposite side (51.5 ml/100g/m). Comparing probe by probe in TIA patients, the average rCBF of the symptomatic site was 44.1 +/- 11.9 ml/100g/m and that of the symmetrically opposite site was 47.6 +/- 13.0 ml/100g/m in (A) group. In (B) group, the average rCBF of the symptomatic site was 46.2 +/- 10.8 ml/100g/m, and 47.7 +/- 10.8 ml/100g/m for the non-symptomatic site. These values in both group (A) and (B), have a significant difference between symptomatic probes and non-symptomatic probes (p less than 8.0 X 10(-7) and p less than 6.5 X 10(-3)).

Brain↗
PubMed1985

The Keyes technique and self-inflicted injuries. Three case reports.

Three cases of self-inflicted gingival injuries resulting from the improper use of the Keyes technique are presented. The profession must assume responsibility for studies to determine the safety of the methods of application of the hydrogen peroxide, salt and baking soda mixtures and disseminate this information for the public interest.

Bicarbonates↗
PubMed1984

The ultrasound macroscope: initial studies of breast tissue.

A system called the ultrasound macroscope has been developed to measure the ultrasonic properties of tissues. Based on the concept of the scanning acoustic microscope, it is capable of generating quantitative images of ultrasound velocity, attenuation and backscatter for macroscopic slices of tissue. By maintaining high resolution (approximately 120 microns at 13 MHz) the morphology of complex tissues is well delineated. Data from regions of interest in the tissue are transformed into three dimensional probability distributions representative of the tissue's ultrasonic characteristics. Sets of two dimensional projections of these distributions are used to display the information. As an initial study, the properties of breast tissues are analyzed. Examples of both normal and abnormal pathology are presented and the relevance of the results to clinical imaging are discussed.

Adult↗
PubMed1983

Cortical oxidative metabolism under conditions of ischemia, hypoxia, and asphyxia in the rabbit.

The purpose of this investigation was to compare the effects of hypoxia, asphyxia, and ischemia on brain cortical oxidative metabolism. This study was carried out using 14 New Zealand White rabbits. The effects of episodic stress were measured simultaneously on brain functional metabolism by monitoring cortical oxygen tension (brain pO2), cortical cerebral blood flow (cCBF), cortical blood volume, and mitochondrial oxidative metabolism. During hypoxia (when the fraction of inspired O2 (FiO2) was reduced to 10%) and asphyxia (induced by turning the respirator off), there was a decrease of brain pO2 but an increase of cCBF and blood volume. Similarly, there was a reduction of cortical oxidative metabolism. In post-asphyxic conditions, an overshoot of brain pO2 and post-asphyxic oxidation of cytochrome (Cyt.) aa3 were usually shown. Under ischemic conditions (induced by sudden severe hypotension plus bilateral common carotid occlusion), cCBF and blood volume were decreased. There was also a decrease of brain pO2 and a reduction of Cyt. aa3 following ischemia. These techniques are applicable in intraoperative monitoring of patients.

Animals↗
PubMed1982

Regional cerebral blood flow in patients with vertebrobasilar disease.

We have investigated the changes in regional cerebral blood flow (rCBF) in patients with occlusive vertebrobasilar disease. Fifty patients who showed severe stenosis or occlusion of the vertebrobasilar artery territory were studied by angiography. Lesions in 13 of these patients were limited to the vertebrobasilar artery (limited VB group), and 37 patients showed combined vertebrobasilar/carotid artery lesions (combined VB-C group). Measurements of rCBF in the group of 50 patients using the intravenous xenon 133 technique showed that there was a significant decrease in the mean rCBF (47.5 +/- 1.4 ml/100 gm/min) as compared with 19 age-matched normal subjects (54.9 +/- 1.8 ml/100 gm/min. There was also a significant difference in mean rCBF between the combined VB-C group (45.6 +/- 1.5 ml/100 gm/min) and a group of 153 patients with limited carotid artery lesions (C group, 49.8 +/- 1.0 ml/100 gm/min). However, no significant difference in mean rCBF was found between the limited VB group and normal subjects. There were no differences in rCBF when evaluated according to the presence or absence of angiographic collateral circulation via the posterior communicating artery (Pcom). Good correlation was found between mean rCBF and direction of collateral flow via the Pcom (p less than 0.05). The value of hemispheric rCBF of patients with carotid system transient ischemic attacks (TIAs) was significantly lower than that of patients with vertebrobasilar system TIAs (p less than 0.02). In cerebral autoregulation tests of 24 patients with occlusive vertebrobasilar disease (7 patients from the limited VB group and 17 patients from the combined VB-C group), 13 of these 24 patients (54%) showed an impairment of autoregulation.

Aged↗
PubMed1982

Long-term evaluation of cerebral blood flow, transient ischemic attacks, and stroke after STA-MCA anastomosis.

A group of 107 consecutive patients with patent extracranial-intracranial bypasses were followed an average of 25.2 months to determine the long-term results on regional cerebral blood flow (rCBF), transient ischemic attacks (TIAs), and stroke incidence. Average mean rCBF initially rose to 110% at 1 week, then gradually fell to 105% at 6 months, and 85% at 2 years. Maximum increase in cerebral blood flow occurred in patients with middle cerebral artery stenosis or those in the preoperative low flow group, i.e., less than 50 ml/100 gm/min. In the group with TIAs plus mild stroke, the mean rCBF rose to 122% at 1 week, compared to the group with TIAs only who showed a mean increase to 107% at one week. Clinical improvement was excellent or good in 82% of those with TIAs only; in those with TIAs plus mild stroke, 77% had excellent or good relief of TIAs; and in those with mild stroke only, 70% recovered from their neurological deficits. In the 25.2 months of average follow-up, stroke occurred in only 1 patient on the side of the anastomosis, and in 2 patients on the side opposite the anastomosis, giving an average stroke incidence of 1.5% per year.

Adult↗
PubMed1982

Hemodynamics, oxygen consumption and serum catecholamine changes in progressive, lethal peritonitis in the dog.

A progressive, lethal canine peritonitis model was developed using the intraperitoneal injection of previously processed, frozen human stool. Of 15 dogs with fecal contamination, seven died within 24 hours and eight died over two to nine days, with a mean of five days. The model was associated with an initial hyperdynamic state which became quite variable as sepsis progressed. The cardiac index in the septic dogs correlated directly with the arteriovenous oxygen content difference. Evidence of multiple system organ failure and a significant increase in norepinephrine levels was noted in the septic dogs. The serum catecholamine levels were inversely correlated with the systemic blood pressure but did not correlate with the systemic vascular resistance or the cardiac index. This implies a lack of responsiveness of resistance vessels or the heart to catecholamines in this severely septic dog model.

Alkaline Phosphatase↗
PubMed1981

Ethnic and cultural determinants of the perceptions of female dental students.

A survey of women dental students enrolled in all American and Canadian dental schools during the 1977-78 academic year was conducted to determine their backgrounds, current status, motivation regarding dentistry as a career, perception of the dental school environment, preferences in dental education, and future plans. The data were analyzed on the basis of ethnic or racial derivation to delineate differences in the perceptions of female dental students of various ethnic groups. Recognizing the nature of such differences may prove beneficial to dental educators, who must determine the specific problems faced by female students of various ethnic groups.

Adult↗
PubMed1980

Acute lymphoblastic leukemia with giant intracytoplasmic inclusions.

Leukemic cells of bone marrow and peripheral blood showing clusters of distinctive, large, uniform, rounded intracytoplasmic inclusions were found in a patient who had acute lymphoblastic leukemia. These membrane-bound inclusions ranged from 0.8 to 1.4 microgram in diameter and were clearly demonstrated on routinely stained preparations. Electron microscopy disclosed transitions between well-developed mitochondria and the electron-dense structures. The functional significance of these presumably altered mitochondria is uncertain. Whorled lamellar internal structures, in occasional fingerprintlike arrangements, may represent duplication of mitochondrial cristae and, functionally, may reflect increased metabolic rate or otherwise abnormal metabolism. Cytochemical studies demonstrated the presence of both periodic acid-Schiff positivity and nonspecific esterase activity in these inclusions, but no peroxidase or acid phosphatase was found. These findings support the lymphoid nature of the disorder. Immunologic surface membrane markers are consistent with this case being, as with the majority of acute lymphoblastic leukemias, of non-B, non-T cell type. Cytogenetic studies on cultured leukemic cells from bone marrow and peripheral blood showed a consistently abnormal karyotype associated with the presence of an XXY chromosomal constitution. Since no other tissues (e.g., dermal fibroblasts) were examined, the diagnosis of Klinefelter's syndrome cannot be confirmed. A causal relationship between the coexistence of the abnormal karyotype and the acute leukemia was not proven but was suspected.

Bone Marrow↗
PubMed1980

Women dental students: preferences in support services.

Female dental students in 68 American and Canadian dental schools were surveyed to determine their attitudes and concerns about women in dental school, and their preferences in support services. Almost 80 percent of the women reported that their sex did not not hinder them in achieving peak academic success. They believe that qualifications, rather than sex, should be the primary consideration in admitting students and hiring faculty. The majority of respondents indicated that the most beneficial support service for women would be a seminar series specific to their concerns. They also believe that to have women dentists used as role models in lectures and textbooks would be both appropriate and supportive.

Attitude↗
PubMed1979

Fluorescence mapping of mitochondrial redox changes in heart and brain.

Fluorescence techniques may be utilized to map changes in the distribution of mitochondrial redox states in heart and brain during ischemic or hypoxic stress. The basis of these techniques is the intrinsic fluorescence of reduced NADH and oxidized flavoprotein in mitochondria which respond to changes in critical oxygen supply. Ischemic areas in rabbit hearts induced by coronary ligation were detected and mapped based on the increase in NADH fluorescence in the ischemic zone. The width of the jeopardized normoxic tissue surrounding the ischemic area (less than 50--350 mu) was measured by combination of fluorescein angiography and NADH fluorescence. Areas of increased NADH fluorescence in gerbil brains after carotid artery ligation or induction of spreading depression were mapped in a similar manner. Intraoperative monitoring of flavoprotein fluorescence from human cerebral cortex after superficial temporal artery middle cerebral artery (STA-MCA) anastomoses demonstrated increased rates of cortical oxidative metabolism after the surgical procedures.

Animals↗
PubMed1977

Tetracycline-induced extrinsic discoloration of the dentition.

Tetracycline, a broad-spectrum antibiotic, is known to cause intrinsic discoloration of the dentition. A case is being presented of extrinsic discoloration of the teeth associated with the use of this drug. This is believed to be the first such reported case in the literature. Possible mechanisms of how tetracycline may cause extrinsic tooth discoloration are discussed.

Adult↗