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Biomedical subjects

G Austin

Publications and source records attributed to G Austin.

15 recordsLinked to original sources
PubMed1992

Quantitative middle cerebral artery flow in normal and vasospastic arteries.

To determine the degree of MCA vasospasm necessary to exceed the ischaemic threshold of blood flow reduction to less than 1/3 normal flow, we developed a computer model of blood flow in the middle cerebral artery distribution. When solved for a 3 mm trunk diameter, it showed a normal flow of 179 ml/min. It was necessary to decrease trunk diameter by 75%, or branch diameter by 50%, or increase peripheral resistance by a factor of 3, in order to decrease blood flow to less than 1/3 normal.

Cerebral Arteries↗
PubMed1990

A unique mental health network for Victorian aboriginal people.

The Victorian Aboriginal Mental Health Network (VAMHN) is a unique mental health programme for Aboriginal people in Australia. The network was set up in 1987. The services and programmes developed include a community consultation service, a psychiatric inpatient unit; and educational, evaluative and research programmes. Utilisation of the network has steadily increased and the demand for both primary and secondary consultations continues to grow.

Adult↗
PubMed1985

Microelectrode for measuring local cortical oxygen tension and blood flow in the same microareas of cat cortex.

The purpose of this study is to investigate the relationship between changes in cortical Po2 (bPo2) and cortical blood flow when inhalating different oxygen mixtures. Experiments were performed on 31 cats anaesthetized with N2O/O2 plus supplemental drugs for immobilization and analgesia. Cortical Po2 was measured by the polarographic method using 25 microns Pt electrode (coated) and a 250 micron Ag-AgCl2 indifferent electrode, especially designed to rest lightly on the cortex by means of coiled spring support. Using the same electrode but with opposite tip polarization; local cortical blood flow (lCoBF) was measured at the same site by the H2-clearance method. The change of bPo2 in going from FiO2 25% to FiO2 75% was measured at 58 different sites. (Table 2). At 25% FiO2 the mean bPo2 was 24 +/- 16 mm Hg, with a range from 4 to 92 mm Hg. With increased FiO2 to 75% local bPo2 responded quite differently at adjacent sites. At 75% FiO2 the mean bPo2 was 42.7 +/- 32 mm Hg with a range from 10 mm Hg to 198 mm Hg. The bPo2 and lCoBF were both measured at 44 of the 58 different sites. Cortical sites with a resting bPo2 greater than 30 mm Hg at 25% FiO2 had a lCBF = 57 +/- 12 ml/100g m; whereas sites with resting normoxic bPO2 less than 20 mm Hg had a mean ICoBF = 56 +/- 14 ml/100g min.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Endotracheal↗
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↗
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↗
PubMedDate not supplied

Cerebral blood flow in patients undergoing microanastomosis for modification for prevention of stroke.

The high incidence of stroke has been considered and the importance of measuring cerebral blood flow (CBF) in patients with transient ischemic attacks has been emphasized. A brief description has been given of the non-invasive method of measuring CBF using a brief bolus injection of 133xenon into any convenient arm vein. The values of CBFg = 75 +/- 8 and CBFw = 24 +/- 2 in ml per 100 g per M compared closely to those obtained by the internal carotid method of measurement. Cerebral blood flow in the gray matter, CBFg is the more sensitive measurement and is used almost exclusively to evaluate patients undergoing microneurosurgical anastomosis for cerebral ischemia in an attempt to prevent or modify stroke. The post operative studies in patients who had a pre operative depression of CBFg greater than 2 S.D. showed improvement in both the frontal and parietal regions. The latter was more significant with p less than 0.04 using paired t-tests.

Carotid Artery, Internal↗