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Biomedical subjects

M E Cooper

Publications and source records attributed to M E Cooper.

At least 19 recordsLinked to original sources
PubMed1992

Antihypertensive therapy in a model combining spontaneous hypertension with diabetes.

We have compared the effects of the angiotensin converting enzyme inhibitor, perindopril, and a conventional antihypertensive regimen (triple therapy: hydralazine, reserpine and hydrochlorothiazide) on kidney function and albuminuria in hypertensive diabetic rats. Diabetes was induced with streptozotocin in spontaneously hypertensive (SHR) rats and they were randomized to receive no treatment, perindopril or triple therapy. Antihypertensive drugs were commenced at the time of induction of diabetes and continued for 16 weeks. Blood pressure reduction was equal in the groups treated with perindopril or triple therapy. All groups had similar severity of diabetes as determined by body weight, serum glucose and glycated hemoglobin levels. Whereas plasma renin activity rose in both the perindopril and triple therapy groups, it is likely that the effects on angiotensin II levels were opposite since perindopril but not triple therapy was associated with a significant reduction in plasma angiotensin converting enzyme activity. Diabetes was associated with an increase in glomerular filtration rate. At 12 weeks, glomerular filtration rate was higher in the perindopril treated group when compared to the triple therapy group, but neither group treated with antihypertensive therapy was different to untreated diabetic rats. Both drug regimens reduced albuminuria in the diabetic rats to a similar degree apparently independently of their effects on the renin-angiotensin system. Studies in diabetic subjects are warranted to evaluate different classes of antihypertensive drugs with respect to their effects on kidney function, proteinuria and glomerular morphology.

Albuminuria↗
PubMed1992

Angiotensin converting enzyme inhibition and calcium channel blockade in incipient diabetic nephropathy. The Melbourne Diabetic Nephropathy Study Group.

Small increases in blood pressure are a feature of incipient diabetic nephropathy, and mean blood pressure often correlates with the degree of albuminuria in such patients. Antihypertensive therapy with angiotensin converting enzyme inhibitors (CEI) or calcium channel blockers (CCB) has been assessed in several studies to determine if either form of treatment modifies incipient diabetic nephropathy and its evolution to established nephropathy. The acute renal hemodynamic effects of CEI differ from those of CCB under certain circumstances. In incipient diabetic nephropathy, therapy with CEI but not CCB tends to reduce filtration fraction, especially in hyperfiltering patients. In hypertensive patients with incipient diabetic nephropathy, both treatments result in a decrease in albuminuria and the responses are mainly dependent on the lowering of systemic blood pressure. In normotensive patients with incipient diabetic nephropathy, a lowering of mean blood pressure with CEI or CCB is not found consistently while effects on albuminuria are difficult to interpret. Short- and long-term therapy with CEI lowers or stabilizes albuminuria. Short-term administration of CCB has at times been associated with increases in albuminuria, but a comparison of CEI and CCB over 12 months in the Melbourne Diabetic Nephropathy Study (MDNS) has shown that both drugs stabilize albuminuria with no significant differences in their effects. Serial analysis of urinary sodium excretion in the MDNS shows that the hypotensive response to CEI in incipient nephropathy is highly dependent on sodium intake, and that sodium intake may modulate albuminuria during both CEI and CCB therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1992

Meeting report of the International Society of Hypertension Conference on Hypertension and Diabetes.

Points of agreement: (1) In IDDM, hypertension occurs in patients who have already developed nephropathy, probably in the microalbuminuric phase. (2) Hypertension is an important accelerator of the development of diabetic nephropathy. (3) Hypertension, obesity and NIDDM are often associated, and insulin resistance is commonly observed in all three states. (4) Antihypertensive therapy retards the development of diabetic nephropathy in IDDM and reduces proteinuria in NIDDM. (5) The choice of antihypertensive agent in the diabetic patient must be based upon the efficacy of the drug as well as avoidance of side effects including deleterious influence on glucose, insulin and lipid levels and renoprotection. (6) Carefully conducted long-term comparative trials between different classes of antihypertensive drugs in microalbuminuric IDDM and NIDDM patients are essential. Points of major controversy: (1) Detection of IDDM patients prone to the development of diabetic nephropathy can be performed by measuring specific parameters such as erythrocyte Na(+)-Li+ countertransport activity. (2) Insulin resistance is a pathogenic mechanism rather than purely an association with hypertension and obesity. (3) A certain class of antihypertensive agents--ACE inhibitors--confers a specific renoprotective effect in diabetic nephropathy, in addition to its effects upon systemic blood pressure. (4) Reduction of blood pressure should be considered in the normotensive microalbuminuric diabetic patient. (5) Microalbuminuria is a sufficient 'surrogate endpoint' for the progression of renal failure.

Animals↗
PubMed1992

Mesenteric vascular angiotensin-converting enzyme is increased in experimental diabetes mellitus.

1. Diabetes mellitus was induced by streptozotocin in male Wistar rats, and angiotensin-converting enzyme measured in plasma and mesenteric vessels 3 weeks later. 2. Diabetes was associated with increased mesenteric wet weight/bodyweight ratio (control 0.2 s.e.m. 0.02 mg/g, n = 21, vs diabetes 1.0 s.e.m. 0.3 mg/g, n = 27, P less than 0.01, ANOVA). 3. Plasma angiotensin-converting enzyme activity was increased in diabetic rats (98 s.e.m. 3 nmol HL/mL per min) compared with controls (64 s.e.m. 6 nmol HL/mL per min, P less than 0.01, ANOVA). 4. Mesenteric vessel angiotensin-converting enzyme was increased in diabetes mellitus estimated by radioligand binding site density (fmol/mg protein; 1407 s.e.m. 166 fmol/mg protein) compared with controls (890 s.e.m. 56 fmol/mg protein, P less than 0.05, ANOVA) and by enzyme kinetic assay (diabetes, 15.5 s.e.m. 1.5 nmol HL/mg protein per min, controls, 8.3 s.e.m. 0.7 nmol HL/mg protein per min, P less than 0.01, ANOVA). The equilibrium dissociation constant of ligand-angiotensin-converting enzyme interaction was unchanged. 5. Increased vascular angiotensin-converting enzyme concentration may contribute to vascular hypertrophy and diabetic vasculopathy by increased local synthesis of angiotensin II.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1992

Diabetic renal microvascular disease: the role of hypertension and ACE inhibitors.

1. It has been suggested that hypertension may be an important determinant of the rate of progression of diabetic microangiopathy. 2. Renal microvascular disease as assessed by urinary albumin excretion and glomerular ultrastructure was evaluated in a model in which streptozotocin diabetes was induced in spontaneously hypertensive rats (SHR). 3. Diabetes was associated with increases in urinary albumin excretion, and hypertension resulted in a further increase in albuminuria. 4. Various antihypertensive regimens were administered to diabetic SHR, with the angiotensin-converting enzyme inhibitor perindopril and triple therapy (hydralazine, reserpine and hydrochlorothiazide) being more effective than the calcium antagonist (lacidipine) in retarding the increase in albuminuria in diabetic SHR. 5. Antihypertensive therapy appears to ameliorate the development of diabetic renal disease.

Albuminuria↗
PubMed1991

Legal cases involving birds: the role of the veterinary surgeon.

Since the passing of the Wildlife and Countryside Act 1981, veterinary surgeons have had an increasingly important role to play in legal cases concerning wild animals, especially birds. This paper proposes guidelines for those who may be asked to investigate birds clinically, to carry out post mortem examinations or to perform laboratory tests. The importance of developing and using standard techniques is emphasised and attention is drawn to the need for more detailed research in the field of avian forensic pathology.

Animals↗
PubMed1991

Comparison of sequential cyproterone acetate/estrogen versus spironolactone/oral contraceptive in the treatment of hirsutism.

The effects of the antiandrogen drugs cyproterone acetate (CPA) and spironolactone on hair growth and androgen levels were compared in a randomized study of 48 hirsute women. Twenty six subjects completed 6 months of therapy with 100 mg/day CPA and 19 subjects completed 6 months of 100 mg/day spironolactone. All except 10 subjects received concomitant estrogen therapy. Measured objectively, total hair diameter fell by 17.1% with spironolactone (P less than 0.001), and by 16.8% with CPA (P less than 0.001). The diameter of the hair medulla fell by 17.8% with spironolactone (P less than 0.01), and by 31.7% with CPA (P less than 0.001). There was no difference between the drugs in their effect on hair diameter. Plasma testosterone levels also fell significantly with both drugs. As a subjective assessment of treatment efficacy, the frequency with which subjects performed cosmetic measures was recorded. This fell by 38% with spironolactone and by 44.7% with CPA (P less than 0.001 both drugs), and again there was no difference between the drugs. Side effects caused cessation of treatment in one subject taking CPA and two subjects taking spironolactone, and milder side effects were noted in two further subjects from each treatment group. We conclude that spironolactone and CPA, in the dosages used in this study, are effective and well tolerated agents for the treatment of hirsutism, and that neither drug demonstrates a particular advantage over the other.

Adult↗
PubMed1990

Comparison of simvastatin and cholestyramine in the treatment of primary hypercholesterolaemia.

The effects of simvastatin, a competitive inhibitor of the enzyme 3-hydroxy-3-methylglutaryl-coenzyme A reductase, on plasma lipid levels were compared with those of the bile acid sequestrant cholestyramine in a randomized parallel study of 60 subjects with primary hypercholesterolaemia. After a 12-week direct comparison period 37 subjects with inadequate cholesterol reduction received a combination of both drugs and all subjects were followed for a further 40 weeks. Simvastatin was more effective than cholestyramine in lowering total and LDL cholesterol levels and the LDL/HDL ratio (-31.7% v. -19.7% [P less than 0.01], -41.0% v. -31.8% [P less than 0.05] and -46.7% v. -33.6% [P less than 0.01], respectively at Week 12). Only simvastatin significantly increased the HDL cholesterol concentration (+13.3% [P less than 0.01] v. +6.4%). Cholestyramine increased plasma triglyceride levels by 37.5% (P less than 0.01) whereas simvastatin caused a slight non-significant reduction. Combined therapy produced a further decrease in total and LDL cholesterol levels, and in the LDL/HDL ratio, which was sustained for the duration of the study. Simvastatin was better tolerated than cholestyramine (P less than 0.01), and combining the two drugs enhanced efficacy without increasing the frequency of side effects.

Adult↗
PubMed1990

Hyperlipidaemia increases albuminuria in hypertensive and normotensive rats.

1. The effects of a high cholesterol diet on urinary albumin excretion were examined in spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats over 36 weeks. 2. Cholesterol feeding resulted in an increase in total-cholesterol and a decrease in HDL-cholesterol without influencing triglyceride levels in both strains. 3. Urinary albumin excretion was significantly elevated in cholesterol-fed SHR and WKY rats. 4. These results suggest that hyperlipidaemia may be important in acceleration of experimental nephropathy.

Albuminuria↗
PubMed1990

The use of simvastatin, an HMG CoA reductase inhibitor, in older patients with hypercholesterolemia and atherosclerosis.

Epidemiological evidence suggests that elevated serum cholesterol, especially the low density lipoprotein (LDL) fraction, the total/high density lipoprotein (HDL)-cholesterol ratio, and the LDL/HDL-cholesterol ratio, remains a risk factor for atheromatous disease up to the age of 79 years. We studied the efficacy and tolerability of simvastatin, an HMG CoA reductase inhibitor, in 20 patients aged 65 to 75 years with clinical evidence of atheromatous disease. After four weeks of treatment, there was a 29% fall in LDL-cholesterol levels (P less than .01 vs placebo) with low dose simvastatin and a 38% fall with high dose simvastatin (P less than .001 vs placebo). Similar falls were seen in total cholesterol levels and the LDL/HDL-cholesterol and total/HDL-cholesterol ratios. Apoprotein B levels decreased by approximately 20% with both doses (P less than .05 vs placebo). In an open extension of the study, the decreases in lipid parameters were sustained for a further 48 weeks of treatment with doses of simvastatin ranging from 10 to 40 mg. Two patients required the addition of cholestyramine. Although a small study like this cannot establish safety and tolerance, side effects were minor and did not require stopping therapy in any patient. Simvastatin is an effective cholesterol lowering agent in older patients.

Aged↗
PubMed1990

Glomerular filtration rate in streptozocin-induced diabetic rats. Role of exchangeable sodium, vasoactive hormones, and insulin therapy.

The interrelationships of sodium and volume status, atrial natriuretic peptide (ANP), plasma renin activity (PRA), insulinlike growth factor I (IGF-I), and kidney weight and their influence on glomerular filtration rate (GFR) were investigated in rats during the first 4 wk of streptozocin-induced diabetes (STZ-D). In each of three experiments, untreated diabetic rats were compared with nondiabetic control rats and rats with varying degrees of glycemic control during insulin therapy. The first experiment evaluated exchangeable sodium, plasma volume, and GFR. In untreated diabetic rats, exchangeable sodium and plasma volume, but not GFR, were increased by approximately 25% compared with control rats. Insulin-treated diabetic rats with plasma glucose levels ranging from 12 to 30 mM had increased GFR, whereas exchangeable sodium and plasma volume were reduced toward control values. Daily insulin therapy, titrated to maintain euglycemia, further reduced exchangeable sodium and plasma volume and decreased but did not normalize GFR. The second experiment evaluated the relationship between vasoactive hormones and GFR. In untreated diabetic rats, plasma ANP levels increased 89% and urinary cyclic GMP (cGMP) excretion increased 94%, with an 85% decrease in PRA, whereas GFR was unchanged. Moderate hyperglycemia (plasma glucose 12-30 mM) was associated with normalized plasma ANP levels and urinary cGMP excretion, a 52% decrease in PRA, and a 13% increase in GFR. The third experiment studied serial changes in food and water intake and vasoactive hormones and end-point measurement of kidney weight, GFR, and plasma IGF-I. In the untreated diabetic group, urinary cGMP excretion was significantly elevated after 3 wk, whereas the reduction in PRA levels was apparent after 1 wk.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Nephropathy in model combining genetic hypertension with experimental diabetes. Enalapril versus hydralazine and metoprolol therapy.

We compared the effects of the angiotensin-converting enzyme inhibitor enalapril and a conventional antihypertensive regimen (hydralazine and metoprolol) on kidney function, albuminuria, and glomerular ultrastructure in hypertensive diabetic and nondiabetic rats. Diabetes was induced with streptozocin at 8 wk of age in spontaneously hypertensive (SHR) rats. Antihypertensive drugs were administered in drinking water from the time of induction of diabetes in all groups. Blood pressure reduction was equal in the diabetic and nondiabetic SHR rats receiving either enalapril or hydralazine plus metoprolol. In diabetic SHR rats, there was a rise in serum creatinine after 32 wk, which did not occur in diabetic rats treated with either antihypertensive regimen or in nondiabetic rats. Both drug regimens reduced albuminuria in diabetic and nondiabetic SHR rats to a similar degree. Enalapril and the combination of hydralazine and metoprolol were associated with decreased glomerular basement membrane thickness and glomerular volume in diabetic and nondiabetic SHR rats without significant effect on fractional mesangial volume. Thus, antihypertensive therapy retards the development of albuminuria, glomerular basement membrane thickening, and glomerular hypertrophy in the rat in the presence or absence of diabetes. No specific benefit of angiotensin-converting enzyme inhibition was observed in these hypertensive models of nephropathy. Human studies comparing the effects of different classes of antihypertensive drugs on kidney function, proteinuria, and glomerular morphology are warranted.

Administration, Oral↗
PubMed1989

Reduced bone mass in daughters of women with osteoporosis.

To determine whether premenopausal daughters of women with postmenopausal osteoporosis have lower bone mass than other women of the same age, we measured the bone mineral content of the lumbar spine and femoral neck and midshaft, using dual-photon absorptiometry, in 25 postmenopausal women with osteoporotic compression fractures and in 32 of their premenopausal daughters; we then compared the results with those in normal controls. As compared with normal postmenopausal women, women with osteoporosis had lower bone mineral content in the lumbar spine, femoral neck, and femoral midshaft by 33, 24, and 15 percent, respectively (P less than 0.001 for each comparison by the one-tailed t-test). As compared with normal premenopausal women, the daughters of women with osteoporosis had lower bone mineral content at these sites by 7, 5, and 3 percent, respectively (P = 0.03, 0.07, and 0.15, respectively, by the one-tailed t-test). In terms of a standardized score, we calculated that the mean (+/- SEM) relative deficits in bone mineral content in the daughters of women with osteoporosis were 58 +/- 18 percent (lumbar spine) and 34 +/- 16 percent (femoral neck) of the relative deficits in their mothers. We conclude that daughters of women with osteoporosis have reduced bone mass in the lumbar spine and perhaps in the femoral neck; this reduction in bone mass may put them at increased risk for fractures. We also conclude that postmenopausal osteoporosis may result partly from a relatively low peak bone mass rather than from excessive loss of bone.

Bone and Bones↗
PubMed1989

Enalapril retards glomerular basement membrane thickening and albuminuria in the diabetic rat.

This study has evaluated the effects of the angiotensin converting enzyme inhibitor Enalapril on glomerular ultrastructure and albuminuria in normotensive and hypertensive diabetic rats. Streptozotocin-diabetes was induced in Wistar Kyoto and spontaneously hypertensive rats. Enalapril was administered in drinking water in diabetic normotensive, control hypertensive and diabetic hypertensive rats. Enalapril therapy prevented an increase in glomerular basement membrane thickness in diabetic normotensive, control hypertensive and diabetic hypertensive rats without any significant effect on fractional mesangial volume. Enalapril decreased albuminuria in diabetic normotensive, control hypertensive and diabetic hypertensive rats. Thus, enalapril retards the development of glomerular basement membrane thickening and albuminuria in the rat, in the presence or absence of hypertension.

Albuminuria↗
PubMed1989

Ramipril reduces albuminuria in diabetic rats fed a high protein diet.

1. Streptozotocin diabetes was induced in Wistar-Kyoto rats fed a 50% protein diet. Animals were randomized to receive either the ACE inhibitor ramipril, 1 mg/L in drinking water (n = 7), or no treatment (n = 7) and were studied for 6 months. Blood glucose, body weight and glomerular filtration rate (GFR) were measured at 0, 1, 4, 8 and 16 weeks of diabetes and urinary albumin excretion was measured every 8 weeks. 2. In both groups, GFR increased significantly within 1 week of induction of diabetes (P less than 0.001) and thereafter remained stable. There was no difference in GFR between the treated and untreated groups. 3. Urinary albumin excretion increased progressively in both groups throughout the study. Ramipril treatment reduced albuminuria by approximately 50% at weeks 16 and 24 (P less than 0.01). 4. The amelioration of diabetic albuminuria by ACE inhibition, in the setting of high dietary protein intake, may have important implications for the treatment of human diabetic nephropathy.

Albuminuria↗
PubMed1989

Triphasic changes in selectivity with increasing proteinuria in type 1 and type 2 diabetes.

Two indices of the selectivity of proteinuria, the immunoglobulin G (IgG)/albumin and the IgG/transferrin clearance ratios, were studied cross-sectionally and serially over 7 years in a cohort of 52 Type 1 and 60 Type 2 diabetic patients without established diabetic nephropathy. In Type 1 and Type 2 diabetic patients with albuminuria less than 30 micrograms min-1, both protein clearance ratios were significantly higher than in 27 control subjects. As albuminuria increased, there was a decrease in both protein clearance ratios. However, at albumin clearances above 90 nl s-1, equivalent to albumin excretion rates of greater than 250 micrograms min-1, a positive correlation was found in Type 2 diabetic patients between protein clearance ratios and albuminuria. In individual Type 1 and Type 2 diabetic patients with progressively increasing proteinuria, serial measurements of selectivity showed a decline in both protein clearance ratios with the onset of microalbuminuria. Episodes of transient microalbuminuria were also associated with a fall in the IgG/albumin clearance ratio. The results suggest that the selectivity of proteinuria undergoes a triphasic change with the development of diabetic nephropathy. In the first phase, proteinuria is non-selective with IgG clearance equal to or exceeding transferrin or albumin clearance. As microalbuminuria develops, there is a progressive increase in selectivity reflecting the preferential excretion of transferrin and albumin compared with IgG. In later stages of nephropathy, as shown in Type 2 diabetic patients with macroalbuminuria, there is a return to non-selective proteinuria.

Albuminuria↗
PubMed1989

A rapid purification of L-glutamic acid decarboxylase from the brain of the locust Schistocerca gregaria.

L-Glutamic acid decarboxylase (GAD; EC 4.1.1.15) was purified to apparent homogeneity from the brain of the locust Schistocerca gregaria using a combination of chromatofocusing (Mono P) and gel filtration (Superose 12) media. The homogeneity of the enzyme preparation was established by native polyacrylamide gel electrophoresis (PAGE) with silver staining. The molecular weight of the purified enzyme was estimated from native gradient gel electrophoresis and gel filtration chromatography to be 97,000 +/- 4,000 and 93,000 +/- 5,000, respectively. When analysed by sodium dodecyl sulphate-PAGE, the enzyme was found to be composed of two distinct subunits of Mr 51,000 +/- 1,000 and 44,000 +/- 1,500. Tryptic peptide maps of iodinated preparations of these two subunits showed considerable homology, suggesting that the native enzyme is a dimer of closely related subunits. The purified enzyme had a pH optimum of 7.0-7.4 in 100 mM potassium phosphate buffer and an apparent Km for glutamate of 5.0 mM. The enzyme was strongly inhibited by the carbonyl-trapping reagent aminooxyacetic acid with an I50 value of 0.2 microM.

Animals↗