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Biomedical subjects

D J Betteridge

Publications and source records attributed to D J Betteridge.

142 records · Page 8Linked to original sources
PubMed1975

Regulation of 3-hydroxy-3-methylglutaryl coenzyme-A reductase activity in type II hyperlipoproteinaemia.

The regulation of 3-hydroxy-3-methylglutaryl coenzyme-A reductase activity in leucocytes was studied in a family with familial type II hyperlipoproteinaemia (WHO classification). The propositus was heterozygous and 16 other members of the family were studied. Leucocytes were isolated by a relatively quick and simple procedure and used for enzyme estimations. The results suggest that measurement of the regulation of this enzyme in leucocytes may be helpful in the diagnosis and management of the condition.

Adolescent↗
PubMedDate not supplied

Compactin inhibits cholesterol synthesis in lymphocytes and intestinal mucosa from patients with familial hypercholesterolaemia.

Compactin (2000 nmol/l), a potent competitive inhibitor of the rate-determinign enzyme for cholesterol synthesis (3-hydroxy-3-methyl-glutaryl coenzyme-A reductase), inhibited by about 90% cholesterol synthesis from 14C-acetate in isolated lymphocytes from healthy control and from patients heterozygous for familial hypercholesterolaemia (F.H.). In isolated intestinal mucosa, a physiologically important tissue for cholesterol synthesis, compactin (2000 nmol/l) suppressed cholesterol synthesis by approximately 50% in controls and F.H. patients. Compactin or its derivatives may prove to be useful in the treatment of hypercholesterolaemia.

Acetates↗
PubMedDate not supplied

Differential actions of naftopidil, doxazosin and nifedipine on platelet thromboxane generation and platelet-derived growth factor efflux in vitro.

We examined the effects of the alpha(1)-adrenoreceptor blockers naftopidil and doxazosin and the Ca(2+) antagonist nifedipine on platelet function with reference to stimulus-induced thromboxane (TxB(2)) generation and platelet-derived growth factor (PDGF) efflux. Collagen (5 micro g/ml) caused a 12.5-fold increase in TxB(2) generation, from a basal level of 7.69 +/- 1.28 ng/10(8) platelets to 96.34 +/- 13.37 ng/10(8) platelets (P<0.001). Adrenaline (16 micro M) increased TxB(2) production 3-fold from 2.44 +/- 0.61 to 8.02 +/- 1.08 ng/10(8) platelets (P<0.01). Adrenaline-induced TxB(2) generation was inhibited 42.5 +/- 10.3% (P<0.05) and 81.8 +/- 7.5% (P<0.05) by 10 and 40micro M naftopidil, respectively. Collagen-stimulated TxB(2) generation was inhibited 59.5 +/- 9.2% (P<0.01) by 40 micro M naftopidil and 53.7 +/- 11.3% (P<0.01) by 28 micro M nifedipine. Doxazosin (7.5 and 30 micro M) did not influence adrenaline- or collagen-induced TxB(2) synthesis. Collagen increased PDGF efflux from 1.17 +/- 0.39 to 4.25 +/- 0.51 ng/10(8) platelets (P<0.01), whilst adrenaline raised concentrations from 1.08 +/- 0.19 to 5.37 + 1.02 ng/10(8) platelets (P<0.01). Naftopidil had no effect on collagen-induced PDGF release. Adrenaline-stimulated PDGF efflux was, however, inhibited 82.9 +/- 13.7% (P<0.001) and 125.7 +/- 16.3% (P<0.001) by 10 and 40 micro M naftopidil, respectively. Doxazosin (30 micro M) inhibited adrenaline-induced PDGF release by 70.3 +/- 31.5% (P<0.05), whilst nifedipine (28 micro M) had no effect on collagen-stimulated release. We conclude that naftopidil, like nifedipine, may block stimulated TxB(2) generation via inhibition of phospholipase A(2), the Ca(2+)-dependent, rate-limiting enzyme in thromboxane synthesis. Although adrenaline-induced PDGF release was inhibited by naftopidil and doxazosin, collagen-induced release was unaffected by either alpha(1)-adrenoreceptor blocker or nifedipine, indicating that platelet alpha-granular release is not dependent on Ca(2+) mobilisation or thromboxane generation. Thus, the effects of these drugs on PDGF release may be mediated through alternative cellular signalling mechanisms.

Adrenergic alpha-Antagonists↗
PubMedDate not supplied

Abnormal cerebrovascular carbon dioxide reactivity in people with diabetes.

Cerebral blood flow was measured both under conditions of normocapnia and hypercapnia in 22 diabetic patients and 20 normal control subjects, using either the intravenous 133Xe method or the closely comparable 133Xe inhalation method. While 19 out of 20 control subjects responded appropriately to hypercapnia with an increase in flow, eight of the diabetic patients failed to respond normally, this difference being significant (p = 0.03). Those manifesting an abnormal response included young, insulin-dependent patients with a short duration of diabetes and no clinical evidence of complications.

Adolescent↗
PubMedDate not supplied

Platelet function in uncomplicated insulin-dependent diabetic patients at rest and following exercise.

There are conflicting reports of platelet function abnormalities in diabetic patients without vascular complications. We have studied in vitro platelet aggregation, using platelet rich plasma and whole blood techniques, in 18 patients with uncomplicated insulin-dependent diabetes and a matched group of 24 non-diabetic subjects. In addition we measured plasma beta-thromboglobulin levels in these groups, as an index of in vivo platelet activation, and compared the indices of in vitro and in vivo platelet function before and after maximal bicycle exercise. Before exercise plasma beta-thromboglobulin levels and platelet sensitivities to ADP, collagen or adrenaline, as assessed by both methods of platelet aggregation, were the same in diabetic and control subjects. Both groups showed similar increases in beta-thromboglobulin levels and in platelet sensitivity to all agonists in whole blood following exercise. Using platelet rich plasma there were no changes in platelet sensitivity in either group after exercise. In non-diabetic subjects, increases in noradrenaline levels after exercise correlated with increases in platelet sensitivity to adrenaline in whole blood. This was not observed in the diabetic group. Abnormalities of platelet function, using the techniques described here, are not present in diabetic patients who do not have clinical evidence of vascular disease.

Adenosine Diphosphate↗
PubMedDate not supplied

Blood rheology and cardiovascular risk factors in type 1 diabetes: relationship with microalbuminuria.

Whole blood and plasma viscosity, erythrocyte aggregation and deformability, plasma fibrinogen, lipids, lipoproteins, apolipoproteins, and measures of blood glucose control were compared between 21 Type 1 diabetic patients with microalbuminuria (overnight albumin excretion rate 30-200 micrograms min-1) and 21 patients with albumin excretion below this range matched for age, sex, and duration of diabetes. Patients with microalbuminuria had significantly higher glycosylated haemoglobin (9.4 +/- 1.6 (+/- SD) vs 7.9 +/- 1.8% (normal range 5.0 to 7.6%)), total-cholesterol (5.6 +/- 1.1 vs 4.6 +/- 1.3 mmol l-1), apolipoprotein B (0.82 +/- 0.21 vs 0.66 +/- 0.14 g l-1), and apolipoprotein B:A1 ratio (0.58 +/- 0.18 vs 0.50 +/- 0.15) than those without microalbuminuria (all p less than 0.05). HDL-cholesterol was also raised (1.71 +/- 0.46 vs 1.43 +/- 0.37 mmol l-1, p less than 0.05). Lipoprotein(a) concentration was possibly higher in the microalbuminuric group (median (95% Cl) 105 (82-140) vs 72 (52-114) mg l-1, p = 0.06). No differences were seen in any of the rheological measurements. These results confirm the presence of potentially atherogenic lipoprotein changes in Type 1 diabetic patients with microalbuminuria, but suggest that altered blood rheology does not predate the development of nephropathy.

Adult↗
PubMedDate not supplied

The effect of acipimox in patients with type 2 diabetes and persistent hyperlipidaemia.

A placebo-controlled, double-blind study was performed to assess the effect of 12 weeks treatment with acipimox (250 mg three times per day) on lipoproteins and glycaemic control in patients with Type 2 diabetes. All patients studied had persistent hyperlipidaemia despite acceptable glycaemic control on treatment with diet alone or diet and oral hypoglycaemic agents, achieving glycosylated haemoglobin (HbA1) of less than 10.5% but with fasting total triglycerides greater than 2.5 mmol l-1 or total cholesterol greater than 6.5 mmol l-1. Forty-eight patients were randomized to treatment, 21 to acipimox and 27 to placebo; 43 completed the trial. All patients had been diabetic for at least 1 year. Total cholesterol fell by 6% and total triglycerides by 19% following 12 weeks of acipimox, compared to rises in the placebo group of 1% and 16%, respectively (p less than 0.05). There were no significant differences between acipimox and placebo in the change in low density lipoprotein (LDL) cholesterol, high density lipoprotein (HDL) cholesterol, apolipoproteins AI, AII, or B, or in glycaemic control during the treatment period. Acipimox is effective in reducing fasting total cholesterol and total triglycerides in patients with Type 2 diabetes with acceptable blood glucose control but persistent hyperlipidaemia. Acipimox does not adversely affect glucose tolerance.

Apolipoproteins↗