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Biomedical subjects

T M Davis

Publications and source records attributed to T M Davis.

At least 145 records · Page 8Linked to original sources
PubMed1987

Growth hormone (GH) release in response to GH-releasing hormone in man is 3-fold enhanced by galanin.

The effect of GHRH in a dose (120 micrograms) thought to produce a maximal GH response was compared with the GH response to insulin-induced hypoglycemia, iv infusion of the hypothalamic neuropeptide galanin (40 pmol/kg.min for 40 min), and a combination of GHRH and galanin in normal men. The median peak serum GH level was 29 mU/L in response to GHRH, 28.9 mU/L in response to insulin hypoglycemia, 17.3 mU/L in response to galanin, and 115.0 mU/L in response to the combination of galanin and GHRH. GH release induced by galanin was completely inhibited by a concomitant somatostatin infusion (50 pmol/kg.min). Thus, galanin increased the peak GH response to GHRH, previously thought to be one of the most powerful stimulants to GH release, more than 3-fold. Since the dose of GHRH used was thought to be maximal and since galanin is reported not to have direct effects on the pituitary, one possible mode of action of galanin would be inhibition of tonic endogenous hypothalamic somatostatin release.

Adult↗
PubMed1986

Determinants of ADP-induced platelet aggregation in diabetes mellitus.

ADP-induced platelet aggregation was measured in 15 Type 1 (insulin-dependent) diabetic patients, 15 Type 2 (non-insulin-dependent) diabetic patients and in 15 non-diabetic control subjects. Simultaneous measurements were made of fasting blood glucose, glycosylated haemoglobin, serum insulin, total plasma cholesterol, cholesterol in the lipoprotein subfractions, total triglycerides and platelet phospholipid fatty acid levels. Regression analysis of aggregation against the biochemical variables within the three groups revealed that there was no significant difference in the associations with aggregation between the groups. When the data was pooled, blood glucose (p less than 0.01) and glycosylated haemoglobin (p less than 0.05) demonstrated significant associations with aggregation. Multiple regression analysis was then applied; only blood glucose (p less than 0.05) had an independent effect on aggregation. Platelet aggregation in diabetic patients and non-diabetic patients appears to be related directly only to blood glucose levels.

Adenosine Diphosphate↗
PubMed1986

The abnormal renal axis in children with spina bifida and gibbus deformity--the pseudohorseshoe kidney.

The axes of the kidneys in children with a thoracolumbar gibbus deformity may be distorted to simulate a horseshoe kidney. Measurements of the angle of the gibbus and the angle of intersection of the renal axes were made in 68 children with thoracolumbar meningomyelocele. Thirty-eight children with a gibbus deformity and thoracolumbar meningomyelocele had an abnormality of the renal axis on supine urography, including 19 (28 per cent) in whom a horseshoe kidney was suggested. Three additional children with a gibbus deformity and thoracolumbar meningomyelocele had a normal renal axis. Regression analysis of these data indicated a linear relationship between the angle of the gibbus and the amount of deviation of the renal axis for the values studied. Nuclear scintigraphy, ultrasound studies and clinical records were reviewed in all 41 children with a gibbus deformity. In none were the kidneys fused. There were 21 children with thoracolumbar myelomeningocele who had no gibbus deformity and a normal renal axis. Six other children will be described in detail, 2 of whom were excluded because of severe scoliosis and 4 with congenital renal anomalies.

Child↗
PubMed1985

Platelet sensitivity in vitro to adenosine-5'-diphosphate and prostacyclin and diabetic retinopathy.

Platelet sensitivity to adenosine diphosphate and prostacyclin in diabetes has been assessed using collision theory and the concept of 'sticking probability' (the probability of particle union). Twenty Type 1 (insulin-dependent) diabetic men (10 with no or minimal retinopathy and a matched group of 10 with proliferative retinopathy) and 10 age-matched nondiabetic men were studied. Platelets from the 20 diabetic patients required, on average, 37% less adenosine diphosphate to achieve a sticking probability of 0.5 (ED50) compared with platelets from the non-diabetic subjects (medians 1.50 and 0.95 mumol/l, respectively; p less than 0.01). The platelet prostacyclin response was assessed by the dissociation constant (Ki) for inhibition of adenosine diphosphate-induced aggregation. Platelets from the diabetic patients had similar prostacyclin sensitivity to those from the non-diabetic subjects (medians 0.42 and 0.42 respectively). Diabetic patients with and without retinopathy had similar platelet sensitivity to both adenosine diphosphate and prostacyclin.

Adenosine Diphosphate↗
PubMed1985

CIGMA assessment of insulin resistance and pancreatic beta cell function in the elderly.

Ten elderly subjects aged 71-85 years and with no indication of diabetes had an oral glucose tolerance test (OGTT) and a one hour's continuous infusion of glucose with model assessment (CIGMA) to assess the pathophysiology of glucose intolerance. All had fasting plasma glucose less than 6 mmol/l and glycosylated haemoglobin levels less than 8.8%, but seven had impaired glucose tolerance during the OGTT. The CIGMA similarly assessed glucose tolerance (rs = 0.65, P less than 0.02), and in addition showed increased insulin resistance and low normal beta cell function.

Aged↗
PubMed1985

Plasma fibronectin, factor VIII-related antigen and fibrinogen concentrations, and diabetic retinopathy.

Fibronectin and factor VIII-related antigen (VIIIR: AG), which are produced by the endothelium and are involved in cellular adhesion, may have a role in the development of diabetic retinopathy. We have measured plasma levels of these glycoproteins and of fibrinogen in 9 control males, 10 insulin-dependent diabetic males with nil or minimal retinopathy and 10 insulin-dependent diabetic males with proliferative retinopathy. These three groups were closely matched for age, body weight and smoking habit. The diabetics in each retinopathy group had similar duration of disease and insulin doses. There was no significant difference between plasma fibronectin concentrations in the three groups. Both plasma factor VIII-related antigen activity and fibrinogen concentration were higher amongst the diabetic subjects, especially those with proliferative retinopathy. These two latter measures correlated significantly when the diabetics were considered as a single group, whereas they did not correlate with fibronectin. Plasma concentrations of fibrinogen and factor VIII R: AG, but not fibronectin, have an association with diabetic microvascular disease.

Adult↗
PubMed1983

Plasma N-acetyl-beta, D-glucosaminidase activities and glycaemia in diabetes mellitus.

The plasma activity of the lysosomal enzyme N-acetyl-beta, D-glucosaminidase (NAGase) has been shown to correlate with hyperglycaemia; their temporal relationships have been investigated. In 12 insulin-treated male diabetic patients, NAGase showed a slight diurnal variation with a nadir at 07.00 h (F = 9.54, p less than 0.001). The mean plasma glucose and NAGase fluctuated similarly (rs = 0.88, p less than 0.01) but did not correlate within individual patients. Normoglycaemia was induced in eight insulin-treated diabetic patients for 4 days but the mean NAGase did not fall significantly. Glycaemic improvement over 3 months was achieved by dietary therapy in 28 newly-presenting non-insulin-dependent diabetic patients: there were significant falls in mean fasting plasma glucose (mean +/- SD: 12.8 +/- 3.3 to 8.3 +/- 3.1 mmol/l; p less than 0.001), glycosylated haemoglobin levels (12.4 +/- 2.4 to 9.3 +/- 2.3%, p less than 0.001) and a corresponding decrease of NAGase (1.5 +/- 0.5 to 1.2 +/- 0.4 mumol 4-nitrophenyl-N-acetyl-beta-D-glucosamide released.h-1.ml-1; p less than 0.001). The change in NAGase correlated with the changes in plasma glucose and glycosylated haemoglobin levels (r = 0.61, p less than 0.025; r = 0.48, p less than 0.05, respectively). Plasma NAGase activity may be influenced by glycaemia in diabetes.

Acetylglucosaminidase↗
PubMed1983

Two new burn severity indices.

Two new severity indices for burned patients based on the combined experience of 11,200 patients in 12 major U.S. burn centers are presented. Each index estimates the risk of death utilizing the patient's age, sex, size of burn, perineum involvement, and time from burn to admission, and is suitable for use with patients admitted within 2 weeks of the burn. The two indices differ in the specificity of the burn size information used. The first index utilizes only the per cent of total body surface burned. The second index, in addition, uses the amount of full-thickness burn. The more detailed index provides a somewhat more accurate estimate and may be used if an adequate estimate of the area of full-thickness burn is available. Applications include patient prognosis estimation and retrospective evaluation of new treatments. Methods for the computation and use of both indices are described together with illustrative examples.

Age Factors↗
PubMed1983

Analysis of platelet aggregation using particle collision theory.

The aggregometer monitors changes in light transmission through stirred suspensions of aggregation platelets. Arbitrary measurements from aggregometer recorder tracings have been used to investigate platelet aggregation without regard to mechanisms involved. To determine the applicability of particle collision theory to assessment of in vitro platelet sensitivity to proaggregating agents, platelet-rich plasma (PRP) from five volunteers was used to obtain recorder tracings after addition of ADP in five doses (0.4-4.0 mumol/l PRP) to aliquots of PRP stirred and incubated in an aggregometer. Using the equation describing light transmission through particulate suspensions, particle collision theory, and s (the probability of particle union after collision), a subject- and dose-independent relationship between aggregation rate (dn/dt) and particle number (n) at the recorder tracing inflection point was found (dn/dt = -k X s X n1.56, where k is a constant dependent on particle size and speed and on the proportion of unreactive particles). Determinations of mean particle size at the tracing inflection point indicated that k was also dose independent. Dose-response curves of ADP added vs. s could therefore be constructed. This methodology provides conveniently obtainable quantitative information concerning in vitro platelet "stickiness."

Analysis of Variance↗
PubMed1981

In-vitro venous prostacyclin production, plasma 6-keto-prostaglandin F1 alpha concentrations, and diabetic retinopathy.

Previous studies have shown that vessels from diabetics produce less prostacyclin in vitro than those from normal controls. To determine whether this decreased production is related to complications elective biopsy of a superficial forearm vein was performed on 12 insulin-dependent male diabetics, six with nil or minimal and six with proliferative retinopathy, and seven male controls. Vein segments from the diabetics and controls produced similar amounts of prostacyclin in vitro (medians 0.11 and 0.19 ng/mg tissue respectively), but the segments from the diabetics with nil or minimal retinopathy produced less than those from the diabetics with proliferative retinopathy (medians 0.09 and 0.18 ng/mg respectively). Preoperative plasma immunoreactive concentrations of 6-keto-prostaglandin F1 alpha were not significantly different between the controls and the diabetics (medians 101 and 116 pg/ml respectively). In a separate study, however, 11 diabetics with duration of disease of over 10 years and nil or minimal retinopathy had significantly lower concentrations than a matched group of 16 with background or proliferative retinopathy (medians 79 and 121 pg/ml respectively). These results do not support an association between reduced prostacyclin production and diabetic retinopathy.

6-Ketoprostaglandin F1 alpha↗
PubMed1981

A severity grading chart for the burned patient.

A graphical method for the quick computation of admission severity for the burned patient is described. The method is easily used by non-technical personnel and requires only the patient's age, an estimate of the percentage body surface area burned, and knowledge of the presence or absence of a perineal burn. The severity estimate is obtained by simply applying a straight-edge to the provided chart and reading the severity score from the scale crossed by the straight-edge. The severity score used is an estimate of the patient's mortality risk and is based on an extensively validated multiple logistic model which was developed using the combined experience of 11,200 patients at 12 major United States burn units. This severity score can be used with other severity and treatment factors to determine the level of care needed, and as an aid in triage decisions.

Age Factors↗