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Biomedical subjects

I Davies

Publications and source records attributed to I Davies.

At least 19 recordsLinked to original sources
PubMed1992

Influence of age on plasma osmolality: a community study.

We have shown an age-associated increase in plasma osmolality (p less than 0.001) in 152 randomly selected subjects, living in the community. In the old [mean age 78.0 (7.5) years] the plasma osmolality was 302.2 (300.6-303.8) mOsmol/kg compared with 291.2 (290.0-292.3) mOsmol/kg in the young [39.2 (11.2) years] (p less than 0.0001). In a further group of 20 screened, health status defined, elderly subjects the plasma osmolality was 298.1 (295.9-300.3) mOsmol/kg, which was significantly higher than the young group (p less than 0.0001) but lower than the unscreened old subjects (p = 0.005). The variance was also significantly lower (p = 0.03). The results may reflect a loosening of homoeostatic control and highlight the need for care in subject selection in studies of ageing.

Adult↗
PubMed1992

Fluid balance in elderly patients following acute stroke.

We studied the relationship between plasma osmolality, arginine vasopressin (AVP), and fluid input in patients during the acute phase of a first stroke. Fifteen consecutive patients were studied (median age 79) and their blood sampled on days 0, 1, 2, 3, 7 and 14. Plasma osmolality was related to fluid input over days 0-3 (p = 0.0013) and AVP over 14 days (p less than 0.001). Patients with a poor outcome had higher AVP concentrations (p = 0.02). Those on intravenous fluids received a higher volume (p less than 0.01) and had a lower plasma osmolality (p = 0.04). The results of this preliminary study indicate that a standard regime for fluid input is inappropriate.

Aged↗
PubMed1991

Age-associated changes in neuroaxonal transport in the hypothalamo-neurohypophysial system of the mouse.

In this study, we investigated age-associated changes in neuroaxonal transport of the hormone vasopressin (AVP) and its associated neurophysin (NPII), from the supraoptic nucleus (SON) of the hypothalamus to the neurohypophysis. C57BL/Icrfat male mice of 6 and 28 months of age were injected in the hypothalamus with L-[35S]cysteine. Animals were killed up to 2.25 h after injection and NPII and AVP from the SON and neurohypophysis were separated using HPLC, and the fractions counted for radioactivity. In the SON, radiolabelled NPII and AVP were first detected after 0.50 h in both young and old mice. There was no significant difference between the age-groups in the incorporation of radiolabel over the time course studied. Radiolabelled NPII in the neurohypophysis was significantly above background after 1.25 h in the young, and after 1.50 h in the old mice. The differences between the two age groups was significant (P = 0.05). Radiolabelled AVP followed a similar trend, but was not significantly above background until 1.50 h in the young and 1.75 h in the old. The differences between the two age groups was on the point of significance (P = 0.056). These results indicate a significant reduction of up to 25% in the rate of axonal transport of neurohypophyseal peptides with advancing age.

Aging↗
PubMed1991

Cerebral activity prior to motion task performance: an electroencephalographic study.

Cerebral activity, as reflected by power in the alpha waveband (8-13 Hz), was examined prior to the performance of three tasks with different effort and accuracy requirements. The study aimed to further investigate changes in activity observed in an earlier study in which expert karate performers exhibited significant increases in alpha band power during preparation for a training task. In contrast to the earlier research, the high effort task produced a significant decrease in 'alpha' power prior to performance. 'Alpha' power prior to the high accuracy task showed significant differences mediated by the outcome. Successful performance was preceded by higher levels of 'alpha' power than unsuccessful attempts. The reported use of a cognitive strategy on the first task produced a significant difference in activity, lower alpha power being associated with the use of such a technique.

Attention↗
PubMed1991

Stress hormone and blood glucose response following acute stroke in the elderly.

We studied the relation of reactive hyperglycemia, stress hormone response, and outcome in 23 consecutive elderly patients (median age 80 [range 75-92] years) following an acute first stroke. The median delay from the onset of the stroke to the first blood sample (day 0) was 9 (range 4-22) hours. Subsequent blood samples were taken, after fasting, for the determination of blood glucose, cortisol, catecholamine, insulin, C-peptide, glucagon, and lactate concentrations on days 1, 2, 3, 7, 14, 30, and 90. For all 23 patients, a significant relation was found between the blood glucose concentration and survival (p = 0.03) and the blood glucose concentration decreased with time (p less than 0.001). There was also a significant relation between blood glucose concentration and outcome (p = 0.02). For the 15 patients with complete data, the major determinants of the blood glucose concentration were the cortisol, insulin, and glucagon concentrations (all p less than 0.001), which accounted for 42% of the variance. When all the indexes were analyzed together by logistic regression, only the cortisol concentration was related to outcome (p = 0.02). Hyperglycemia following a stroke probably reflects the intensity of the stress hormone response. We have confirmed that hyperglycemia is a predictor of outcome in persons with stroke.

Acute Disease↗
PubMed1990

The effect of endotoxin on membrane fatty acid composition in BCG-sensitized mice.

The effects of endotoxin on mouse liver phospholipid fatty acid composition have been investigated. Administration of endotoxin from Salmonella abortus equi led to a decrease in the polyunsaturated fatty acid content of livers from mice sensitized with Bacille Calmette Guérin (BCG). The content of arachidonic acid fell significantly in both the phosphatidylcholine and phosphatidylinositol fractions whereas in the phosphatidylethanolamine fraction the linoleic acid content was significantly reduced. The polyunsaturated fatty acids were replaced by increased amounts of oleic acid and palmitic acid, leading to a reduction in the polyunsaturated to saturated fatty acid ratio.

Animals↗
PubMed1990

The ageing hypothalamo-neurohypophysial system. An analysis of the neurohypophysis in normal hydration, osmotic loading and rehydration.

Age-associated changes in the structure and function of the neurohypophysis may contribute to the decreased ability to conserve water in older animals. We investigated the neurohypophyses of 6 and 28-month-old male mice using radioimmunoassay and quantitative morphological techniques. The dry-weight and volume of the neurohypophysis increased significantly with age but the quantity of vasopressin in the gland remained constant. Oxytocin levels decreased with age. A quantitative morphological analysis was performed on the compartments of the neurohypophysis from male mice of 6 and 28 months of age which were either normally hydrated, osmotically loaded, or osmotically loaded and rehydrated. The absolute volumes of the axon endings, swellings, their constituent organelles and the axon terminals containing degenerating subcellular components were determined. The design of the analysis allowed us to examine both age-related changes and statistical interactions between the age of the animal and the behaviour of a variable during the osmotic loading/rehydration phase of the experiment. There was a significant age-related reduction in the volume of the neurohypophysis occupied by the endings and swellings. The diameters of the neurosecretory granules found in the endings were significantly smaller than those in the swellings in both age groups but the size difference was greater in the young animals. Dehydration and subsequent rehydration of old male mice leads to extensive re-modelling of the neurohypophysial compartments and subcellular organelles to the configuration found in the adult animal.

Aging↗
PubMed1990

Oxygen-dependent desulphation of monomethyl sulphate by Agrobacterium sp. M3C.

Agrobacterium sp. M3C, previously isolated from canal-water for its ability to grow on monomethyl sulphate, degraded this ester with stoichiometric liberation of inorganic sulphate. In contrast with the biodegradation of monomethyl sulphate in Hyphomicrobium sp., and of other longer-chain alkyl sulphates in Pseudomonas spp., the pathway in Agrobacterium appeared not to involve a sulphatase enzyme capable of catalysing ester-bond hydrolysis. No such sulphatase was detectable under a range of conditions of bacterial culture, or using various methods for preparing cell-extracts, or different assay conditions. There was no incorporation of 18O-label from H2(18O) into the liberated inorganic sulphate. No methanol was detectable during biodegradation, and the organism was incapable of growth on methanol, and did not produce methanol dehydrogenase activity when grown on monomethyl sulphate. Tracer studies using mono[14C]-methyl sulphate indicated that formate serine and glycine were produced during the biodegradation. The presence of these amino acids, together with high activity of hydroxypyruvate reductase, indicated the operation of the serine pathway common in methylotrophs. Use of an oxygen electrode in conjunction with monomethyl[35S]sulphate showed that release of 35SO2(-4) was dependent on availability of O2, and that there was equimolar stoichiometry among monomethyl sulphate degraded, O2 consumed and 35SO2(-4) released. A proposed pathway for the degradation involved an initial mono-oxygenation to methanediol monosulphate with subsequent elimination of SO2(-4) and concomitant formation of formaldehyde. The pathway was compared with degradation mechanisms for other C1 compounds and for other sulphate esters.

Biodegradation, Environmental↗
PubMed1990

Loss of resistance technique for locating the epidural space: evaluation of glass and plastic syringes.

Location of the epidural space in epidural anaesthesia usually involves the measurement of loss of resistance using glass or plastic syringes. In the present study two varieties of glass syringe and one plastic type were evaluated to determine the resistive forces associated with plunger movement. The mean static (fs) and dynamic (fd) forces for polished glass syringes having a ground plunger only were fs = 0.47 X 10(-3) +/- 0.22 X 10(-3) N and fd = 0.37 X 10(-3) +/- 0.19 X 10(-3) N and for polished glass syringes having a ground barrel and plunger were fs = 0.43 X 10(-3) +/- 0.16 X 10(-3) N and fd = 0.38 X 10(-3) +/- 0.15 X 10(-3) N. Each of these values was significantly lower (P less than 0.5) than those for plastic syringes fs = 2.22 X 10(-3) +/- 0.48 X 10(-3) N and fd = 1.46 X 10(-3) +/- 0.37 X 10(-3) N. It is concluded that glass syringes are favoured over plastic for locating the epidural space because frictional forces developed with glass syringes were significantly lower than with plastic.

Anesthesia, Epidural↗
PubMed1990

Reduced survival with increasing plasma osmolality in elderly continuing-care patients.

The results reported here are from a 2-year follow-up study of 58 elderly patients in a continuing-care unit. Most of these patients were in a hyperosmolar state at the time of entry (mean plasma osmolality 304 +/- 8 mOsmol/kg). The survival of those patients with the highest osmolality (greater than 308 mOsmol/kg) was significantly reduced (p = 0.025), with an increased mortality at 2 years (15/20 patients, p = 0.053). There was no correlation between age and plasma osmolality (r = 0.02) and the effect of osmolality on survival was independent of age. Hyperosmolality was either a marker for, or a cause of, increased mortality in this group of frail elderly patients.

Aged↗
PubMed1990

Haemodynamic and neurohumoral responses in elderly patients with postural hypotension.

Haemodynamic and neurohumoral responses to head-up tilt were measured in 28 elderly patients with postural hypotension (EPPH) and 12 healthy elderly subjects (HE). There were no differences in catecholamines between the groups and only noradrenaline increased on tilt (P less than 0.001). Plasma renin activity and aldosterone were similar in HE and EPPH in the supine and tilt positions. In both groups vasopressin increases (P = 0.032), and plasma volume decreases were the same (P = 0.673). Supine EPPH had higher heart rates (P = 0.019) but similar cardiac indices (P = 0.621). Both had similar changes on tilting (P = 0.975 and P = 0.341). Stroke volume decrease was higher in HE (35%) than EPPH (23%; P less than 0.001). HE showed an increase in peripheral resistance on tilting with no change in EPPH (P = 0.005). EPPH had larger coefficients of variation for all variables. The differences in haemodynamic responses and the similarity of neurohumoral responses during tilting suggest end-organ failure in EPPH with individual variations. Postural hypotension in old age is not a single entity.

Aged↗
PubMed1989

Age-associated changes in the kidney of the laboratory mouse.

This paper describes a qualitative and quantitative morphological investigation of the kidneys of male laboratory mice without macroscopic pathology at 6, 12, 24 and 34 months of age. In the 6- and 12-month old adults there were no signs of microscopic pathological changes in either the kidney cortex or medulla. However, at 24 and 34 months of age minor pathology, such as focal interstitial inflammation, was detected. In both these age groups there were a few glomeruli with sclerotic changes. There were no significant differences in the total volume of the kidneys, cortex, medulla or other structures with age. There was a significant increase in the diameter of the glomeruli with age but no change in the total numbers of glomeruli. The increase in volume of the glomerulus appears to be due to cellular components rather than changes in the blood vessels. It is concluded that in animals without macroscopic pathological changes there are only minor alterations in kidney structure with age, and that any alterations which do take place occur very late in the life span.

Age Factors↗
PubMed1989

Effect of lysophosphatidylcholine on the filtration coefficient in intact dog lungs.

Lysophosphatidylcholine (lyso-Pc) is a lysophospholipid normally found in low concentrations in the lung. At high concentrations lyso-Pc, instilled into the airways, causes pulmonary edema. We tested the hypothesis that the edema caused by lyso-Pc was due to an increase in pulmonary microvascular membrane permeability. In 11 anesthetized dogs we continuously weighed the left lower lobes (LLL) while instilling lyso-Pc (20 mM) into the LLL airways. After 30 min we determined the microvascular membrane fluid filtration coefficient (Kf) from the relationship between the rate of LLL weight gain and the pulmonary microvascular pressure. Kf was not significantly different between the lyso-Pc-treated lobes (0.048 +/- 0.018 ml.min-1.mmHg-1) vs. control lobes (0.067 +/- 0.031 ml.min-1.mmHg-1). Our data do not support the hypothesis that lyso-Pc, instilled into the airways, causes an increase in pulmonary microvascular permeability.

Animals↗
PubMed1989

Elderly female patients in continuing care: why are they hyperosmolar?

We have shown that the majority of elderly female patients in continuing care are in a hyperosmolar state. Thirty-two out of thirty-nine subjects had an osmolality greater than 295 mosm/kg and the mean osmolality was 302 +/- 8 mosm/kg (range 280-317 mosm/kg). No significant relationship was found with the degree of confusion (rs = 0.31; p greater than 0.05). In the second part of the study neither the measured degree of hydration, or any acute, small increases in fluid input influenced the plasma osmolality.

Aged↗
PubMed1988

A new urethral catheter.

A new balloon catheter for women with a flexible urethral portion that conforms to the shape of the closed urethra was tested. In sheep control catheters caused epithelial destruction, which was absent with the conformable catheter. A 12 week crossover trial compared control catheters in 52 long stay geriatric patients. Eighty two out of 91 conformable catheters were rated as comfortable compared with 68 of 87 control (p = 0.006). The average length of time in situ was 15.9 days for the conformable catheter compared with 12.9 days for the control (p = 0.001). The average number of bypasses a week with the conformable catheter was 1.1 compared with 1.3 for the control; this difference was not significant. Examination of 249 used catheters showed significantly fewer with intraluminal obstruction with struvite among the conformable than control catheters (1 (0.8%) versus 15 (11.5%); p less than 0.001). This new catheter for women is a substantial improvement over the Foley catheter and (except in urethral stricture) is suitable for all forms of drainage.

Aged↗