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Biomedical subjects

J Marshall

Publications and source records attributed to J Marshall.

At least 505 records · Page 28Linked to original sources
PubMed1980

Spouse-subject interviews and the reliability of diet studies.

Recently published data suggest relationships between ingestion of a number of food items and risk of cancer of the stomach, bowel and mouth. This engenders concern over the accuracy of such data. To study this, dietary interviews of 158 males in the Western New York Study of Cancer Epidemiology are compared to their spouses' estimates of the husband's dietary histories as taken in separate interviews. Respondents were asked to estimate the frequency with which the males consumed each of several foods. For analysis, the frequency estimates were assembled into categories similar to those used in recent epidemiologic analysis: 5-7 times per week, 1-4 times per week, 1-3 times per month and less than once per month. Generally, 60-80% of respondents pairs agree exactly on the frequency of consumption for individual food items. Over 90% of spouse and respondent food frequency estimates are within one frequency category of each other. Radical disagreements between spouses are rare; generally, in less than 2% of spouse pairs does one member estimate the maximum frequency category, and the other minimum frequency category. The authors suggest therefore that, although diet histories are not precisely replicable, they must be adequate to reveal gross differences between cases and controls.

Adult↗
PubMed1980

Photochemical damage in the albino rat retina: morphological changes and endogenous amino acids.

Endogenous amino acids were measured in retinas of rats exposed for up to 48 h to fluorescent light. Typical light damage was seen in photoreceptor cells after 30 h exposure to a maximum luminance of 1544 scotopic lux; and, from this time, taurine levels were significantly reduced. In contrast, the concentrations of other amino acids increased. After 18 h exposure to light, GABA, glycine, glutamate, and aspartate levels were raised in the photoreceptor cells, and GABA, glutamate, and glutamine levels in the inner retina. When 'exposed' animals were returned to their normal environment for 72 h, photoreceptor degeneration progressed and taurine concentrations were further reduced: the results suggest that the loss was from damaged photoreceptor cells. At this time the concentrations of the other amino acids measured had, in general, returned to normal.

Amino Acids↗
PubMed1980

Viscosity, cerebral blood flow and haematocrit in patients with paraproteinaemia.

It has been suggested that blood viscosity is involved in the control of cerebral blood flow (CBF) (Thomas et al. 1977a, b, Humphrey et al. 1979). CBF, using the intravenous Xenon133 technique, blood viscosity and haematocrit were measured in 21 patients with elevated viscosity due to paraproteinaemia and found to be the same as in normal subjects. However, the paraproteinaemic patients were anaemic with a mean haematocrit of 0.342. This degree of anaemia would normally be associated with a high CBF. The paraproteinaemic patients were then compared with a group of 10 anaemic patients with matched haematocrits but without paraprotein bands. The whole blood and plasma viscosities were significantly higher in the paraproteinaemic patients and the CBF was significantly lower. The haematocrit, and therefore oxygen carriage, was similar in the two groups. It is likely that in the anaemia of paraproteinaemia the expected increase in CBF did not occur because of the limiting factor of increased viscosity. This suggests that in this instance viscosity rather than oxygen carriage is a major determinant in the control of CBF. This is further emphasized by the better correlation between CBF and blood viscosity than between CBF and haematocrit. It seems likely that viscosity and oxygen carriage are independent variables in the control of CBF.

Aged↗
PubMed1980

Cerebral blood flow, haematocrit and viscosity in subjects with a high oxygen affinity haemoglobin variant.

The cerebral blood flow is low in primary polycythaemia, and it has been suggested that this is due to the increase in viscosity which accompanies the elevated haematocrit. In the present study cerebral blood flow has been measured by a non-invasive 133Xenon technique in six subjects with an elevated haematocrit secondary to a haemoglobin variant with increased oxygen affinity. Flow was significantly higher than normal and 81% higher than in 11 subjects of comparable age, matched for haematocrit and viscosity, but without the haemoglobin variant. In patients with this unusual type of polycythaemia, cerebral blood flow is high despite the elevated blood viscosity and the implications of these results are discussed.

Adult↗
PubMed1980

Role of axoplasmic transport in the pathophysiology of ischaemic disc swelling.

Pathological changes in the optic disc and anterior part of the optic nerve of monkeys were studied 5 hours and several days after occlusion of the temporal short posterior ciliary arteries. Ischaemic vacuolation of neural tissue was observed in some of the animals studied and was restricted to the lamina cribrosa and the immediately retrolaminar portion of the optic nerve. Axonal swelling and organelle aggregation were demonstrated in the prelaminar region, and autoradiography after intravitreal injection of tritiated leucine revealed an associated obstruction of rapid and slow orthograde axoplasmic transport. The experimental findings correlate with those seen clinically in acute ischaemic optic neuropathy. The pale swelling of the optic disc in this condition represents an accumulation of axoplasmic debris in retinal ganglion-cell axons owing to obstruction of axoplasmic transport at the lamina cribrosa; it is thus equivalent to a 'cotton-wool spot' of the disc.

Animals↗
PubMed1980

Cerebral blood flow after surgery for recent subarachnoid haemorrhage.

243 measurements of cerebral blood flow by a noninvasive (133)Xe clearance technique have been made in 45 patients undergoing surgery for a recently ruptured cerebral aneurysm. Two groups of patients have been defined by the presence or absence of a postoperative rise in cerebral blood flow which showed a significant correlation with level of consciousness after operation.

Adolescent↗
PubMed1980

Small deep infarcts diagnosed on computed tomography.

The clinical and angiographic correlations of small deep infarcts seen on computed tomography (CT) scan were studied in 297 consecutive patients. Some of these showed the features described by Fisher as part of the lacunar syndrome. In a large number, a source of emboli from either a cardiac or a carotid source was highly probable; in a smaller number, other vascular diseases were present. The finding of a small deep infarct on CT does not exclude the need for further investigation of a possible embolic source in selected patients.

Adolescent↗
PubMed1980

The effects of iopodate on the serum iodothyronine pattern in normal subjects.

The ingestion by normal subjects of 3 g of sodium iopodate, which is widely used in routine oral cholecystography, resulted in significant decreases of serum total and free T3 to a nadir on day 4 which averaged 43% and 40%, respectively, below initial mean values. Total and free rT3 increased markedly to a peak on day 3, 244% and 189%, respectively, above initial mean values. Total and free T4 and free T4 index rose to a maximum on day 4, but these changes were not statistically significant. A marked TSH increase was also seen, most evident on day 3. All these changes reverted to baseline values by day 14 at a time when serum total iodide was still markedly elevated. It is concluded that the changes observed after iopodate were not due to alterations in serum binding proteins nor to an effect on thyroid gland by the large iodine component of iopodate, but were consistent with an effect on the peripheral metabolism of T4. Difficulty in interpreting routine thyroid function tests may occur for up to 14 days after oral cholecystography with iopodate.

Adult↗
PubMed1980

Pharmacological effects of some medicaments on the human brain.

The methodological problems of measuring the effect of drugs on cerebral blood flow (CBF) are examined. In animals these include choice of species, technique of measurement, route of administration and whether the drug crosses the blood-brain barrier. Additional factors in man are age, short or long-term effects, tendency for repeated measurements to give lower readings and need to measure not only CBF but also clinical performance. Despite these difficulties drugs affecting the cerebral circulation are worth intensive study, especially now, when reliable non-invasive methods of mesuring CBF are available and positron emission tomography enables us to study also cerebral metabolism in vivo.

Adult↗
PubMed1979

The uptake and radioautographical localization in the frog retina of [3H](+/-)-aminocyclohexane carboxylic acid, a selective inhibitor of neuronal GABA transport.

The accumulation of [3H](+/-)-cis-3-aminocyclohexane carboxylic acid ([3H] ACHC) in frog retinae in vitro was highly localized in horizontal cells and their processes. [3H]GABA was also mainly accumulated within horizontal cells, but [3H]L-2,4-diaminobutyric acid ([3H]DABA) was taken up predominantly by the neuroglial Müller cells, whilst [3H]beta-alanine was localised largely within the photoreceptors. The uptake of [3H]ACHC (4.2 microM) was almost linear for 30 min and after 60 min a tissue/medium ratio of 5.25 was achieved. The uptake process was temperature sensitive highly dependent on sodium ions, and appeared to be mediated by a saturable transport process with an IC50 value of 0.83 mM. The accumulation of [3H]ACHC was inhibited by GABA and DABA (IC50 = 0.32 mM and 0.23 mM, respectively) whilst beta-alanine was a relatively weak inhibitor (IC50 = 9 mM) of ACHC uptake. In agreement with these results, the efflux of [3H]ACHC from the retina was increased by exposure to ACHC, GABA and DABA but not beta-alanine. In contrast, the efflux of [3H]DABA from the retina was not increased by GABA or ACHC, although DABA itself and potassium depolarization stimulated the release of [3H]DABA. These results strongly suggest that ACHC is accumulated in the frog retina by the same neuronal transport process as GABA. In contrast, the high affinity sites for DABA are localized mainly in glia, although inhibitor and release studies suggest that, at high concentration, DABA also interacts with the neuronal GABA (ACHC) transport process.

Alanine↗
PubMed1979

Cerebral blood-flow and viscosity in relative polycythaemia.

Cerebral blood flow (CBF), red-cell mass, and plasma volume were measured in 39 patients with venous haematocrit values in the range 0.47--0.58. Patients with true polycythaemia were thus excluded. The 39 patients studied fell into two groups--those with a measured red-cell mass in the high-normal range and those with normal red-cell-mass values but reduced plasma-volume values (the relative-polycythaemia, low-plasma-volume group). The mean CBF was low in both the high-normal red-cell-mass (HNRCM) group (45.8 ml/100 g/min) and low-plasma-volume (LPV) group (48.8 ml/100 g/min). The haematocrit in the HNRCM group was 0.504 and in the LPV group 0.513. In a control group of subjects with a mean haematocrit of 0.421 CBF was 68.6 ml/100 g/min. Venesection was associated with a significant rise in CBF in both groups of patients--to 59.7 ml/100 g/min in the HNRCM group and 65.0 ml/100 g/min in the LPV group. Whole-blood viscosity fell significantly in both groups. Both groups demonstrated significant inverse relationships between CBF and haematocrit and between CBF and blood viscosity.

Adult↗
PubMed1979

Reassurance.

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Communication↗