Biomedical subjects

C Hillier

Publications and source records attributed to C Hillier.

At least 19 recordsLinked to original sources

PubMed2006

Psychological interventions for multiple sclerosis.

BACKGROUND: The unpredictable, variable nature of Multiple Sclerosis (MS), and the possibility of increasing disability, means that a diagnosis can have substantial psychological consequences. OBJECTIVES: To assess the effectiveness of psychological interventions for people with MS. SEARCH STRATEGY: We searched 19 databases up to December 2004; Cochrane MS Group Specialised Register, Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, PsychINFO, CINAHL and 14 others. We searched reference lists of articles, wrote to corresponding authors of the 13 papers identified by June 2004, and searched for trials in progress using 3 research registers. SELECTION CRITERIA: Randomised controlled trials of interventions described as wholly or mostly based on psychological theory and practice, in people with MS. Primary outcome measures were disease specific and general quality of life, psychiatric symptoms, psychological functioning, disability, and cognitive outcomes. Secondary outcome measures were number of relapses, pain, fatigue, health care utilisation, changes in medication, and adherence to other therapies. DATA COLLECTION AND ANALYSIS: Pertinent studies were identified from abstracts by one author. Full papers were independently compared to selection criteria by four authors. Key details were extracted from relevant papers using a standard format, and studies scored on three dimensions of quality. The review is organised into four mini-reviews (MR) dependent on the intervention's target population; people with cognitive impairments (MR1), people with moderate to severe disability (MR2), people with MS (no other criteria) (MR3), and people with depression (MR4). MAIN RESULTS: Overall 16 studies were identified and included. MR1: three trials (n=145). Some evidence of effectiveness of cognitive rehabilitation on cognitive outcomes, although this was difficult to interpret because of the large number of outcome measures used. MR2: three trials (n=80). One small trial suggesting psychotherapy may help with depression. MR3: seven studies (n=688). Some evidence that cognitive behavioural therapy may help people adjust to, and cope with, having MS (three trials). The other trials were diverse in nature and some difficult to interpret because of multiple outcome measures. MR4: three trials (n=93). Two small studies of cognitive behavioural therapy showed significant improvements in depression. AUTHORS' CONCLUSIONS: The diversity of psychological interventions identified indicates the many ways in which they can potentially help people with MS. No definite conclusions can be made from this review. However there is reasonable evidence that cognitive behavioural approaches are beneficial in the treatment of depression, and in helping people adjust to, and cope with, having MS.

Adaptation, Psychological↗

PubMed2003

The use of fluorescent nuclear dyes and laser scanning confocal microscopy to study the cellular aspects of arterial remodelling in human subjects with critical limb ischaemia.

Resistance arteries isolated from patients with critical limb ischaemia (CLI), a hypotensive/hypoperfusion state of the lower leg, have been shown to undergo morphological changes opposite to those observed in hypertension, that is, decreased wall thickness, reduced cross-sectional area and a decreased wall : lumen ratio. The aim of this present study was to use laser scanning confocal microscopy (LSCM) to study intact resistance arteries isolated from patients with CLI, specifically to identify the cellular aspects of the morphological changes identified in ischaemic subcutaneous and skeletal muscle resistance vessels. Using LSCM, a significant reduction in adventitial and medial thickness, cross-sectional area and wall : lumen ratio was confirmed in resistance arteries from both distal ischaemic subcutaneous and skeletal muscle vascular beds when compared with corresponding arteries from the proximal non-ischaemic sites. The cellular composition of the adventitial, medial and intimal layers of these distal ischaemic arteries was significantly different compared with proximal non-ischaemic arteries. These differences in the distal arteries were characterised by hypoplasia in the adventitial and medial layers of the arterial wall and hypertrophy in the intimal layer. The differences observed in both distal ischaemic vascular beds (subcutaneous and skeletal muscle) were similar.

Aged↗

PubMed2002

Hormone replacement therapy can augment vascular relaxation in post-menopausal women with type 2 diabetes.

BACKGROUND: Diabetes is a major risk factor for coronary heart disease in women and event rates increase substantially after the menopause. Observational studies have suggested that estrogens may provide cardioprotection by regulating endothelial nitric oxide synthase. METHODS: In order to examine the effect of hormone replacement therapy (HRT) on endothelium-dependent and -independent vascular relaxation in post-menopausal women with type 2 diabetes, an open study was conducted in which gluteal biopsies were collected from 17 women before and after 6 months of transdermal 17 beta-estradiol (80 microg twice weekly) in combination with oral norethisterone (1 mg daily). Small arteries (<550 microm) were dissected from fat and mounted on a wire myograph for assessment of relaxation in response to acetylcholine (ACh), bradykinin (BK) and sodium nitroprusside (SNP). RESULTS: Maximal relaxation responses to ACh, BK and SNP in women with diabetes and non-diabetic control subjects were 52 +/- 8 versus 96 +/- 2% (P < 0.05), 76 +/- 7 versus 97 +/- 1%, (P < 0.05) and 91 +/- 2 versus 98 +/- 1% (P < 0.05) respectively. After 6 months of HRT, maximal relaxation responses to ACh, BK and SNP in women with diabetes (compared with pre-HRT) were: 88 +/- 4 (P < 0.05), 93 +/- 3 (P < 0.05) and 98 +/- 1% (P < 0.05) respectively. At baseline and after HRT, EC50 (concentration required to obtain 50% of maximum response) data exhibited similar changes. CONCLUSIONS: HRT had potentially beneficial effects on vascular relaxation. Data were consistent with improvements in endothelial function, vascular smooth muscle function, or both. Controlled studies are required to confirm and extend these findings.

Acetylcholine↗

PubMed2001

Vasoconstrictor effect of the angiotensin-converting enzyme-resistant, chymase-specific substrate [Pro(11)(D)-Ala(12)] angiotensin I in human dorsal hand veins: in vivo demonstration of non-ace production of angiotensin II in humans.

BACKGROUND: [Pro(11)(D)-Ala(12)] angiotensin I is an ACE-resistant substrate specific for chymase. We used this peptide to determine whether a functionally significant non-ACE angiotensin (Ang) II-generating pathway exists in human dorsal hand veins. METHODS AND RESULTS: Using a modified Aellig technique, we studied the response to Ang I and [Pro(11)(D)-Ala(12)] Ang I in dorsal hand veins in vivo in patients with coronary heart disease. We measured the venoconstrictor effect of each peptide given before and after a 6.25-mg oral dose of the ACE inhibitor captopril or matching placebo. Placebo or captopril was given in a double-blind, randomized fashion. Ang I induced a mean+/-SEM venoconstrictor response of 45+/-11%, 40+/-10%, 55+/-8%, and 4+/-4% before placebo, after placebo, before captopril, and after captopril, respectively. Hence, the response to Ang I was reproducible and was reduced significantly only after treatment with captopril (P=0.002). [Pro(11)(D)-Ala(12)] Ang I induced a mean venoconstrictor response of 42+/-9%, 49+/-9%, 48+/-10%, and 54+/-11% before placebo, after placebo, before captopril, and after captopril, respectively. Hence, captopril had no significant effect on the response to [Pro(11)(D)-Ala(12)] Ang I. CONCLUSIONS: We have demonstrated that [Pro(11)(D)-Ala(12)] Ang I is able to induce venoconstriction in humans in vivo. With this specific pharmacological probe, we have shown that a non-ACE pathway capable of generating Ang II exists in human veins in vivo and is potentially functionally important. This pathway is likely to involve the enzyme chymase.

Administration, Oral↗

PubMed2001

The alpha(1A)-adrenoceptor subtype mediates contraction in rat femoral resistance arteries.

In this study, alpha(1)-adrenoceptor subtypes were characterised in rat femoral resistance arteries mounted on a small vessel myograph. A-61603 was found to be more potent than noradrenaline and phenylephrine in these arteries. Brimonidine (UK 14304) could not evoke any contractile responses and the sensitivity to noradrenaline and phenylephrine was not affected by (8aR,12aS,13aS)-5,8,8a,9,10,11,12,12a,13a-decahydro-3-methoxy-12-(ethylsulphonyl)-6H-isoquino[2,1-g][1,6]-naphthyridine (RS 79948), ruling out the presence of alpha(2)-adrenoceptors. Prazosin, 5-methyl-urapidil and 2-([2,6-dimethoxyphenoxyethyl]aminomethyl)-1,4-benzodioxane (WB 4101) produced rightward shifts in the sensitivity to noradrenaline, giving pA(2) values of 9.6, 9.4 and 10.4, respectively, in agreement with the presence of alpha(1A)-adrenoceptors. (8-[2-[4-(2-Methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4.5]decane-7,9-dione (BMY 7378; 1 microM) produced a small shift in the sensitivity of noradrenaline giving a pK(B) of 7.2. In the presence of 300 nM 5-methyl-urapidil, sensitivity to noradrenaline was not further shifted by 1 microM BMY 7378. Responses to noradrenaline were unaffected by the alpha(1B)-adrenoceptor alkylating agent chloroethylclonidine (1 microM). These results suggest alpha(1A)-adrenoceptors mediate contractile responses to noradrenaline in rat femoral resistance arteries.

Adrenergic alpha-1 Receptor Agonists↗

PubMed2001

Endothelium-derived hyperpolarizing factor : identification and mechanisms of action in human subcutaneous resistance arteries.

BACKGROUND: Both a vascular endothelial cytochrome P450 (CYP450) product of arachidonic acid metabolism and the potassium ion (K(+)) have been identified as endothelium-derived hyperpolarizing factors (EDHFs) in animal vascular tissues. We studied the relative importance of EDHF, nitric oxide (NO), and prostacyclin (PGI(2)) as vasodilators in human subcutaneous arteries. We also examined the mechanisms underlying the vasodilator action of EDHF to elucidate its identity. METHODS AND RESULTS: Subcutaneous resistance arteries were obtained from 41 healthy volunteers. The contribution of EDHF to the vasodilation induced by acetylcholine was assessed by inhibiting production of NO, PGI(2), and membrane hyperpolarization. The mechanisms underlying the relaxation evoked by K(+) and EDHF were elucidated. EDHF was found to account for approximately 80% of acetylcholine-mediated vasorelaxation. Its action was insensitive to the combination of barium and ouabain, whereas barium and ouabain reversed K(+)-mediated vasorelaxation. EDHF-mediated vasorelaxation, however, was sensitive to the phospholipase A(2) inhibitor oleyloxyethyl phosphorylcholine and the CYP450 inhibitor ketoconazole. CONCLUSIONS: EDHF is the major contributor to endothelium-dependent vasorelaxation in human subcutaneous resistance arteries. A product of phospholipase A(2)/CYP450-dependent metabolism of arachidonic acid and not K(+) is the likely identity of EDHF in human subcutaneous resistance arteries.

Acetylcholine↗

PubMed2001

Angiotensin converting enzyme (ACE) and non-ACE dependent angiotensin II generation in resistance arteries from patients with heart failure and coronary heart disease.

OBJECTIVES: We sought to demonstrate non-angiotensin converting enzyme (ACE) dependent angiotensin II (AII) generating pathways in resistance arteries from patients with chronic heart failure (CHF). BACKGROUND: Non-ACE dependent AII generation occurs in resistance arteries from normal volunteers. Inhibition of non-ACE dependent AII generation may have therapeutic potential in CHF. METHODS: Resistance arteries were dissected from gluteal biopsies from patients with coronary heart disease (CHD) and preserved left ventricular function and from patients with CHF. Using wire myography, concentration response curves to angiotensin I (AI) and AII were constructed in the presence of 1) vehicle, 2) chymostatin [an inhibitor of chymase], 3) enalaprilat, and 4) the combination of chymostatin and enalaprilat. RESULTS: In resistance arteries from patients with CHD, the vasoconstrictor response to AI was not inhibited by either inhibitor alone (chymostatin [p > or = 0.05] or enalaprilat [p > or = 0.05]) but was significantly inhibited by the combination (p < 0.001). In arteries from patients with CHF, AI responses were inhibited by enalaprilat (p < 0.05) but not by chymostatin alone (p > 0.05). The combination ofchymostatin and enalaprilat markedly inhibited the response to AI (p < 0.001) to a greater degree than enalaprilat alone (p < or = 0.01). CONCLUSIONS: Non-ACE dependent AII generating pathways exist in resistance arteries from patients with both CHF and CHD. In resistance arteries from patients with CHD, inhibition of either the ACE or chymase pathway alone has no effect on AII generation, and both pathways must be blocked before the vasoconstrictor action of AI is inhibited. In CHF, blockade of ACE results in marked inhibition of responses to AI, but this is enhanced by coinhibition of chymase. These studies suggest that full suppression of the renin-angiotensin system cannot be achieved by ACE inhibition alone and provide a rationale for developing future therapeutic strategies.

Acetylcholine↗

PubMed2001

Effects of urotensin II in human arteries and veins of varying caliber.

BACKGROUND: -Urotensin II (UII) is the ligand for the GPR14 receptor and the most potent vasoconstrictor in the cynomolgus monkey. UII also contracts rat thoracic aorta. We studied the effect of human UII (hUII) in human blood vessels Methods and Results-Small subcutaneous resistance arteries, internal mammary arteries, saphenous veins, and small subcutaneous veins were studied using standard techniques. Subcutaneous resistance arteries constricted in response to norepinephrine (maximum tension, 2.84+/-0.38 mN/mm; the concentration required to produce 50% of the maximum response [EC(50)], 0.52+/-0.07 micromol/L) and endothelin-1 (maximum tension, 4.19+/-0.93 mN/mm; EC(50), 1.6+/-0.1 nmol/L). hUII did not contract these arteries, internal mammary arteries, or either type of vein, but it was a potent vasoconstrictor in rat thoracic aorta (maximum tension, 2.36+/-0.2 mN/mm; EC(50), 1.13+/-0.36 nmol/L). CONCLUSIONS: -hUII has no vasoconstrictor action in human arteries and veins of different sizes and vascular beds. Marked species differences in the actions of UII question its importance in human cardiovascular regulation.

Adult↗

PubMed2001

Increased alpha(1)- and alpha(2)-adrenoceptor-mediated contractile responses of human skeletal muscle resistance arteries in chronic limb ischemia.

OBJECTIVE: Recently, we have shown augmented contractile responses of skeletal muscle resistance arteries to noradrenaline in patients with critical limb ischemia. We investigated whether this increased sensitivity in skeletal muscle resistance arteries is due to either alpha(1)- or alpha(2)-adrenoceptor-mediated responses or both. METHODS: Skeletal muscle resistance arteries were isolated from the proximal (non-ischemic) and distal (ischemic) parts of limbs amputated for critical limb ischemia and mounted on a small vessel wire myograph. Cumulative concentration response curves of the vessel segments to noradrenaline, phenylephrine and brimonidine were obtained in the presence or the absence of the selective antagonists, prazosin and RS79948. RESULTS: Noradrenaline and phenylephrine produced almost equal maximal contractile responses. Brimonidine responses were smaller and were almost abolished by 0.1 microM RS 79948 while those of phenylephrine and noradrenaline were not affected. Prazosin reduced the maximum responses to brimonidine, shifted the concentration response curves of noradrenaline and phenylephrine rightwards giving pK(B) values of 9.86 and 9.33, respectively. Maximum responses produced by all three agonists in distal vessels were significantly higher than those obtained in proximal vessels. CONCLUSIONS: Noradrenaline contractile responses in skeletal muscle resistance arteries are predominantly mediated by alpha(1)-adrenoceptors. Both alpha(1)- and alpha(2)-adrenoceptor-mediated responses are increased in the arteries from ischemic regions that may aggravate the decreased blood flow to the limbs due to arterial occlusion.

Adrenergic alpha-Agonists↗

PubMed2001

Signalling mechanisms underlying the myogenic response in human subcutaneous resistance arteries.

OBJECTIVE: In this study we have examined for the first time the signal transduction mechanisms involved in the generation of pressure-dependent myogenic tone in human small resistance arteries from the subcutaneous vascular bed. METHODS: Myogenic responses and the subcellular mechanisms involved in the generation of this response were studied on a pressure myograph. RESULTS AND CONCLUSION: Human subcutaneous resistance arteries constricted 14.1+/-1.1% in response to an increases in intraluminal pressure from 40 to 80 mmHg and a further 3.5+/-1.7% in response to the 80-120-mmHg pressure step. Ca(2+) depletion or nifedipine abolished this response, whereas BAY K 8644 increased this response to 20.6+/-2.1% (P<0.05, response vs. control). The phospholipase C inhibitor U-73122 reduced the myogenic response to 2.5+/-1.0% at 80 mmHg (P<0.01, response vs. control) and abolished it at 120 mmHg. Diacylglycerol lipase inhibition with RHC-80267 abolished all myogenic responses to pressure. The protein kinase C (PKC) activator phorbol 12,13-dibutyrate increased the maximal myogenic response to 20.9+/-1.8% (P<0.05, response vs. control), whereas the PKC inhibitor calphostin C abolished myogenic responses. These data show that the generation of pressure-dependent myogenic tone in human subcutaneous arteries is dependent on Ca(2+) influx via voltage operated Ca(2+) channels (VOCCs) and a concomitant requirement for the activation of phospholipase C (PLC), diacylglycerol, and PKC.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMed2001

Functional characterization of alpha(1)-adrenoceptor subtypes in human skeletal muscle resistance arteries.

alpha(1)-adrenoceptor subtypes in human skeletal muscle resistance arteries were characterized using agonists noradrenaline (non-selective) and A61603 (alpha(1A)-selective), the antagonists prazosin (non-selective), 5-methyl-urapidil (alpha(1A)-selective) and BMY7378 (alpha(1D)-selective) and the alkylating agent chloroethylclonidine (preferential for alpha(1B)). Small arteries were obtained from the non-ischaemic skeletal muscle of limbs amputated for critical limb ischaemia and isometric tension recorded using wire myography. Prazosin antagonized responses to noradrenaline with a pA(2) value of 9.18, consistent with the presence of alpha(1)-adrenoceptors, although the Schild slope (1.32) was significantly different from unity. 5-Methyl-urapidil competitively antagonized responses to noradrenaline with a pK(B) value of 8.48 and a Schild slope of 0.99, consistent with the presence of alpha(1A)-adrenoceptors. In the presence of 300 nM 5-methyl-urapidil, noradrenaline exhibited biphasic concentration response curves, indicating the presence of a minor population of a 5-methyl-urapidil-resistant subtype. Contractile responses to noradrenaline were not affected by 1 microM chloroethylclonidine suggesting the absence of alpha(1B)-adrenoceptors. Maximum responses to noradrenaline and A61603 were reduced to a similar extent by 10 microM chloroethylclonidine, suggesting an effect of chloroethylclonidine at alpha(1A)-adrenoceptors at the higher concentration. BMY7378 (10 and 100 nM) had no effect on responses to noradrenaline. BMY7378 (1 microM) poorly shifted the potency of noradrenaline giving a pA(2) of 6.52. These results rule out the presence of the alpha(1D)-subtype. These results show that contractile responses to noradrenaline in human skeletal muscle resistance arteries are predominantly mediated by the alpha(1A)-adrenoceptor subtype with a minor population of an unknown alpha(1)-adrenoceptor subtype.

Adrenergic alpha-Agonists↗

PubMed2001

Effects of adrenomedullin on angiotensin II stimulated atrial natriuretic peptide and arginine vasopressin secretion in healthy humans.

AIMS: Adrenomedullin is a newly described peptide that has widespread tissue distribution. Its presence in cardiovascular (including vascular endothelial cells, smooth muscle cells, and cardiac atria and ventricles) and renal tissues, together with its vasodilatory and natriuretic properties, suggest a role in blood pressure regulation and fluid and electrolyte balance. METHODS: Nine normal volunteers were studied to determine whether or not adrenomedullin influenced plasma atrial natriuretic peptide and arginine vasopressin concentrations during systemic angiotensin II infusion. RESULTS: A significant (P = 0.02) augmentation of atrial natriuretic peptide concentrations, but no suppression of arginine vasopressin concentrations, was found with coinfusion of adrenomedullin and angiotensin II when compared with vehicle and angiotensin II. CONCLUSIONS: Despite its vasodilator and natriuretic action, adrenomedullin significantly augmented angiotensin II-stimulated plasma atrial natriuretic peptide concentrations in healthy humans. This provides further evidence of a synergistic interaction between adrenomedullin and atrial natriuretic peptide and suggests that adrenomedullin may have a role in fluid and electrolyte balance and blood pressure regulation.

Adrenomedullin↗

PubMed2001

The use of the Australian Basic Treatment Equivalent (BTE) workload measure for linear accelerators in Canada.

The Inter Society of Radiation Oncologists of North America (ISRON) workload standard for linear accelerators is the one most widely used; it regards the treatment of 250 or more patients per year as an acceptable limit. Nevertheless, there is concern that this standard does not represent the current workload of linear accelerators, given that the complexity of techniques and equipment has increased significantly since the ISRON model was developed in the late 1980s. Delaney et al. recently validated a workload indicator for Australian (AUS) centres, known as the basic treatment equivalent (BTE). They showed that this was a better predictor of workload and that there was less variation between centres using this model than there would have been by using fields/hour. This centre attempted to validate this model for use in a Canadian centre, by collecting treatment data on all linear accelerator-treated patients during February 1998. The linear accelerators at this centre delivered 2,295 fractions (6,928 fields) in 662 hours during February 1998. When 15 minutes was used as a denominator, the BTE model functioned as a better workload indicator than simple measures such as fields/hour. It also had better performance in reducing variability between machines. A BTE of 3,403 was calculated for these machines. The mean value for fields/hour, BTE/hour and BTE/fraction for this centre fell within the range of values quoted by AUS centres. The BTE/fraction value for this centre was relatively high compared with the AUS mean, indicating this centre's reliance on the use of a high number of complex techniques. We recommend that the model should be further refined for the Canadian context by developing BTE values with the use of local time and motion studies, including factors such as multileaf collimators and enhanced dynamic wedges.

Australia↗

PubMed2001

Insulin-mediated vasorelaxation in pregnancy.

OBJECTIVE: To investigate insulin-mediated vasorelaxation in pregnancy, and the role of nitric oxide in this response. DESIGN: In vitro study of isolated subcutaneous resistance arteries from pregnant and non-pregnant women. METHODS: Small arteries (mean vessel diameter <300 microm) were isolated from biopsies of subcutaneous fat from 14 pregnant and seven non-pregnant women. Insulin-mediated attenuation of the vasoconstriction response to noradrenaline, before and after nitric oxide synthase inhibition, was studied in isolated arteries using wire myography. Vessel responses to noradrenaline following incubation with insulin were also tested after endothelial denudation. Maximum responses were compared using one-way ANOVA and Bonferroni's post hoc test for multiple comparisons. RESULTS: In pregnancy, the maximum vasoconstriction produced by noradrenaline was increased (P < 0.01). Insulin significantly reduced this response in pregnant women (P < 0.01), while inhibition of nitric oxide synthase with Nomega-nitro-L-arginine methyl ester (L-NAME) resulted in potentiation (P < 0.05). Following inhibition of nitric oxide synthase with L-NAME, addition of the insulin was still able to produce a significant attenuation in maximum vasoconstriction to noradrenaline in pregnant women (P < 0.01). Furthermore, the absence of functioning endothelium did not abolish the attenuating effect of the insulin on noradrenaline-induced vasoconstriction in pregnant women (P < 0.01). CONCLUSIONS: The vasodilatory effect of insulin is not diminished in pregnancy, despite the development of insulin resistance. Furthermore, the attenuation of vasoconstrictor tone is via an endothelium-independent mechanism. This suggests that the vascular dysfunction associated with diabetes mellitus does not occur with physiological insulin resistance.

Adult↗

PubMed2001

Effect of neutral endopeptidase inhibition on the actions of adrenomedullin and endothelin-1 in resistance arteries from patients with chronic heart failure.

Adrenomedullin and endothelin are novel peptides that are produced in the blood vessel wall and have contrasting biologic actions. Both may play a pathophysiological role in atherosclerosis and chronic heart failure. It has also been suggested that both peptides may be metabolized by neutral endopeptidase and that pharmacological manipulation of this enzyme may be of therapeutic interest. We investigated the effect of thiorphan, a neutral endopeptidase inhibitor, on the vasodilator response to adrenomedullin and the vasoconstrictor response to endothelin in small resistance arteries taken from patients with heart failure caused by coronary heart disease. Small resistance arteries were dissected from gluteal biopsy samples and studied with wire myography. Thiorphan did not affect the vasodilator response to adrenomedullin in arteries preconstricted with norepinephrine. Maximal responses were 66% (SD 11%) and 72% (8%) in the absence and presence of thiorphan, respectively (n=8). The vasoconstrictor response to endothelin was also unaffected. The maximum vasoconstrictor responses in the absence and presence of thiorphan were 152% (11%) and 132% (12%), respectively (n=8). The values of corresponding -log concentrations of agonist required to effect a 50% response (pD(2)) were 8.52 (0.11) and 8.64 (0.15), respectively. We showed that the inhibition of neutral endopeptidase does not augment the vasodilator and vasoconstrictor activities of adrenomedullin and endothelin, respectively, in small resistance arteries from patients with chronic heart failure. This suggests that neutral endopeptidase inhibition, as a therapeutic strategy, will enhance neither the potentially desirable vascular actions of adrenomedullin nor the potentially unfavorable vascular effects of endothelin-1 in human cardiovascular disease states.

Adrenomedullin↗

PubMed2001

The effect of type 1 diabetes mellitus on vascular responses to endothelin-1 in pregnant women.

Diabetes is associated with vascular dysfunction, which may be due in part to altered vascular responses to endogenous peptides such as endothelin-1. These altered responses may also contribute to the decreased maternal peripheral resistance in pregnancy. The aim of this study was to examine the effect of diabetes on the vasoconstrictor response to endothelin-1 in pregnant women. Small arteries were isolated from nine healthy pregnant, seven type 1 diabetic pregnant women, and five healthy nonpregnant women. Contraction curves were performed on a wire myograph for noradrenaline (1 nM to 30 microM) and endothelin-1 (1 pM to 0.3 microM). Maximum responses and sensitivity were compared by t test. No differences in maximum response to noradrenaline or potassium were seen among the three groups. The maximum response to endothelin-1 was significantly increased in pregnancy (P < 0.05), whereas endothelin-1 sensitivity was reduced in the diabetic compared with the nondiabetic pregnant women (P < 0.05). Pregnant women have an increased maximum vasoconstriction response to endothelin-1 compared with nonpregnant women, whereas diabetic pregnant women demonstrate reduced sensitivity to endothelin-1. These observations suggest that endothelin-1 may play a role in maintaining peripheral vascular tone in normal pregnancy, and the decreased sensitivity seen in pregnant women with diabetes may reflect abnormal vascular reactivity.

Adult↗

PubMed2001

The effects of transdermal estradiol in combination with oral norethisterone on lipoproteins, coagulation, and endothelial markers in postmenopausal women with type 2 diabetes: a randomized, placebo-controlled study.

People with type 2 diabetes have a substantially increased risk of coronary heart disease (CHD). Short-term studies with unopposed oral estradiol in women with diabetes have suggested potentially beneficial effects on lipids, thrombotic factors, and insulin sensitivity. However, most (nonhysterectomized) postmenopausal women require combined estrogen-progesterone preparations. We randomized 43 women with type 2 diabetes either to continuous transdermal estradiol (80-microg patches) in combination with oral norethisterone (1 mg daily) or to identical placebos. Blood samples were taken before and after 6 months for measurement of lipoproteins, coagulation factors, and endothelial markers. Total cholesterol and triglyceride concentrations decreased by 8% and 22%, respectively, in those receiving hormone replacement therapy (P < 0.05 relative to change in placebo group after adjustment for baseline concentrations). There was a trend toward a reduction in high density lipoprotein cholesterol concentration (P = 0.06). Factor VII activity decreased by 16% (P < 0.001), and von Willebrand factor antigen decreased by 7% (P = 0.014) with active treatment. Levels of fibrinogen, tissue plasminogen activator, fibrin D dimer, very low density lipoprotein cholesterol, low density lipoprotein cholesterol, lipoprotein(a), and leptin were not significantly altered. No change in glycemic control was detected. Overall, lipid changes may be considered slightly beneficial with respect to CHD risk. The significant decrease in factor VII activity in this study is notable, because elevated factor VII activity has been associated with an increased risk of coronary thrombosis and normally increases with administration of oral estrogen-containing preparations. In addition, a reduction in von Willebrand factor antigen is consistent with an improvement in endothelial function. We suggest that the regimen used in this study may have the potential to reduce CHD risk in women with type 2 diabetes.

Administration, Cutaneous↗

PubMed2001

Effect of adrenomedullin on the production of endothelin-1 and on its vasoconstrictor action in resistance arteries: evidence for a receptor-specific functional interaction in patients with heart failure.

Endothelin-1 (ET-1) and adrenomedullin (ADM) are both produced in the arterial wall, but have opposing biological actions. Evidence from experimental animals suggests a functional interaction between ET-1 and ADM. We have tested this in humans. Small resistance arteries were obtained from gluteal biopsies taken from patients with chronic heart failure (CHF) due to coronary heart disease (CHD), or with CHD and preserved ventricular function. The contractile responses to big ET-1 and to ET-1 in both sets of vessels were studied in the absence (control) and presence of ADM at 20 pmol/l (low ADM) or 200 pmol/l (high ADM), using wire myography. ADM did not affect the conversion of big ET-1 into ET-1 in vessels from patients with either CHD or CHF. Low ADM did not alter the contractile response to ET-1 in vessels from patients with CHF. Low ADM was not tested in vessels from patients with CHD, but high ADM did not affect this response in arteries from these patients. High ADM did, however, significantly reduce the vasoconstrictor effect of ET-1 in vessels from patients with CHF. The maximum response, as a percentage of the response to high potassium, was 199% (S.E.M. 25%) in the control experiments (n=14), 205% (27%) in the low-ADM (n=7) studies and 150% (17%) in the high-ADM (n=6) experiments (P<0.001). Furthermore, the Hill coefficient increased from 0.57+/-0.05 in the absence of ADM to 1.16+/-0.15 in the high-ADM experiments, indicating that ADM at 200 pmol/l specifically antagonized one receptor type in vessels from patients with CHF. We conclude that there is a one-site receptor interaction between ADM and ET-1 that is specific for vessels from patients with CHF. This functional interaction between ADM and ET-1 in resistance arteries may be of pathophysiological importance in CHF.

Adrenomedullin↗