Management of hypertension in pregnancy

Hypertension in pregnancy is generally defined as either an absolute BP > 140/90 mm Hg or a rise in systolic BP > or = 25 mm Hg and/or diastolic BP > or = 15 mm Hg from pre-conception or 1st trimester BP. Hypertension in pregnancy is classified as: a) Chronic--essential or secondary hypertension, b) De novo--pre-eclampsia or gestational hypertension, and c) Pre-eclampsia superimposed on chronic hypertension. Pre-eclampsia is a multisystem disorder in which hypertension is but one sign. The major maternal abnormalities occur in kidneys, liver, brain and coagulation systems. Impaired uteroplacental blood flow causes fetal growth retardation or intrauterine death. There is general agreement that BP > or = 170/110 mm Hg should be lowered rapidly to protect the mother against risk of stroke or eclampsia. There is dispute concerning the level at which lesser degrees of hypertension should be treated, and lowering BP is treating only one aspect of pre-eclampsia. Delivery remains the definitive management.

Effect of steroid hormones on blood pressure

1. There is considerable evidence to support the idea that steroid hormones have the potential to increase blood pressure that may not always be via 'classical' mineralocorticoid or glucocorticoid action. 2. Epidemiological studies, together with the evidence from studies in animals, proposed the link between an adverse intra-uterine environment (i.e. undernutrition or excess exposure to glucocorticoids) and the early onset of cardiovascular and metabolic diseases later in life. 3. We tested this by treating pregnant ewes (and foetuses) with excess steroid early in pregnancy. The mean ages at which the prenatal exposure to glucocorticoid (dexamethasone 0.48 mg/h for 48 h) occurred were 22 +/- 0.4 to 29 +/- 0.4 days (prenatal treatment group 1; PTG1) and 59 +/- 2 to 66 +/- 2 days (PTG2), respectively. Basal blood pressures and hormones and the vascular responsiveness to graded doses of angiotensin II and noradrenaline, or to a 5-day adrenocorticotropin hormone treatment (ACTH), in lambs at 4, 10 and 19 months of age were studied. 4. Basal mean arterial pressure in PTG1 group (80 +/- 1 mmHg at 4 months; 83 +/- 1 mmHg at 10 months; and 89 +/- 1 mmHg at 19 months; n = 6) was significantly different (P < 0.05 in all groups) from that in the control group of lambs (74 +/- 2 mmHg at 4 months; 76 +/- 1 mmHg at 10 months; and 81 +/- 1 mmHg at 19 months; n = 7). Prenatal glucocorticoid exposure did not alter vascular responsiveness to noradrenaline, angiotensin II and ACTH in these sheep at any of the ages studied. 5. These results suggest that foetal exposure to maternal dexamethasone during defined developmental stage or 'window' programmes elevated blood pressure, which persists later in life.

Rates of HIV-1 transmission within marriage in rural Uganda in relation to the HIV sero-status of the partners

OBJECTIVE

To assess the efficacy of transmission of HIV-1 within married couples in rural Uganda according to the sero-status of the partners.

DESIGN

Estimation of HIV incidence rates for 2200 adults in a population cohort followed for 7 years comparing male-to-female with female-to-male transmission and sero-discordant with concordant sero-negative couples.

METHODS

Each year, adults (over 12 years of age) resident in the study area were linked to their spouses if also censused as resident. The HIV sero-status was determined annually.

RESULTS

At baseline 7% of married adults were in sero-discordant marriages and in half of these the man was HIV-positive. Among those with HIV-positive spouses, the age-adjusted HIV incidence in women was twice that of men (rate ratio (RR) = 2.2 95% confidence interval (CI) 0.9-5.4) whereas, among those with HIV-negative spouses, the incidence in women was less than half that of men (RR = 0.4, 95% CI 0.2-0.8). The age-adjusted incidence among women with HIV-positive spouses was 105.8 times (95% CI 33.6-332.7) that of women with HIV-negative spouses, the equivalent ratio for men being 11.6 (95% CI 5.8-23.4).

CONCLUSION

Men are twice as likely as women to bring HIV infection into a marriage, presumably through extra-marital sexual behaviour. Within sero-discordant marriages women become infected twice as fast as men, probably because of increased biological susceptibility. Married adults, particularly women, with HIV-positive spouses are at very high risk of HIV infection. Married couples in this population should be encouraged to attend for HIV counselling together so that sero-discordant couples can be identified and advised accordingly.

Seroprevalence and incidence of genital ulcer infections in a rural Ugandan population

OBJECTIVES

To determine age-sex specific seroprevalence and incidence rates of Treponema pallidum, Haemophilus ducreyi, and HSV-2; to assess the association between HIV-1 status and incidence of these STIs; and HSV-2 serostatus with number of lifetime sexual partners.

METHODS

Antibodies against HIV-1, T pallidum, H ducreyi, and HSV-2 infections were tested using approximately 1000 paired (2 year interval) sera collected from a rural adult (15-54 years) population cohort in south west Uganda.

RESULTS

Overall HIV-1 prevalence was 4.9%. Prevalence for T pallidum was 12.9% among males and 12.6% among females. The corresponding rates for H ducreyi were 9.8% and 7.3% respectively. HSV-2 prevalence rates were considerably lower in males (36.0%) than in females (71.5%), p < 0.001. Incidence rates for T pallidum per 1000 person years of observation were 8.4 for males and 12.3 for females. The corresponding rates for H ducreyi were 24.6 and 20.0 and for HSV-2 were 73.2 and 122.9 per 1000 person years of observation, respectively. The RR of HSV-2 incidence was 3.69 in HIV seropositive cases versus HIV seronegative after adjusting for age and sex. The corresponding RR for H ducreyi was 3.50 among female HIV positive cases versus negatives with no effect seen in males. Association between HIV-1 prevalence and prevalence of other STIs was significant (Mantel-Haenszel test) for H ducreyi (p = 0.01) and for HSV-2 (p = 0.004) but not for T pallidum (p > 0.4). HSV-2 prevalence was associated with number of lifetime sexual partners (females, p = 0.003; males, p = 0.08).

CONCLUSIONS

The results have provided a reliable estimate of the magnitude of the STI problem and demonstrated an association between HIV-1 status and serology of other STIs in a general rural population in sub-Saharan Africa. The study has also highlighted a correlation between HSV-2 seropositivity and number of reported lifetime sexual partners.

The immune response to Mycobacterium tuberculosis in HIV-infected and uninfected adults in Uganda: application of a whole blood cytokine assay in an epidemiological study

SETTING

Out-patient clinic, Entebbe, Uganda.

BACKGROUND

It has been proposed that 'type 1' cytokines are essential in protective immunity to Mycobacterium tuberculosis and that suppression of 'type 1' or a switch to a 'type 2' profile is deleterious. We employed a simple assay to examine whether the dependence of the immunological responses to mycobacterial antigens on a range of explanatory factors could be determined in a population where tuberculosis is endemic.

OBJECTIVE

To determine the relationship between the tuberculin skin test response and cytokine profile, and the effect of human immunodeficiency virus (HIV) infection.

DESIGN

A cross-sectional study of 97 Ugandan adults (22 HIV-positive, 75 HIV-negative). Whole blood was stimulated in vitro using mycobacterial antigens (purified protein derivative [PPD] and culture filtrate proteins [CFP]). 'Type 1' cytokines (gamma interferon [IFN-gamma] and interleukin-2 [IL-2]), 'type 2' cytokines (IL-5 and IL-10) and tumour necrosis factor alpha (TNF-alpha) were measured in culture supernatants.

RESULTS

Among HIV-negative subjects, a positive tuberculin skin test was associated with type 1 or mixed (type 1 + type 2) cytokine production, but a positive IFN-gamma response also occurred in a proportion of tuberculin skin test negative subjects (36% for PPD, 17% for CFP). In association with HIV infection, IFN-gamma responses to mycobacterial antigens were profoundly impaired (odds ratio [OR] 0.10 for PPD, 0.06 for CFP, P< or =0.001), but production of IL-2, IL-5 and TNF-alpha was relatively sustained, and IL-10 increased or sustained (OR 3.97 for PPD, P = 0.01, 1.14 for CFP, P = 0.99).

CONCLUSION

The type 1/type 2 cytokine balance was not defined by the tuberculin skin test response, and may have a closer relation to protective immunity. IFN-gamma production was strikingly impaired in association with HIV infection, while production of type 2 cytokines was sustained or increased. Use of a simple assay allowed a large sample of subjects to be examined, producing epidemiologically meaningful results.

Adrenocorticotrophin-induced hypertension: effects of mineralocorticoid and glucocorticoid receptor antagonism

OBJECTIVE

To examine whether the increase of blood pressure in adrenocorticotrophin-treated rats is mediated through mineralocorticoid or glucocorticoid receptors or corticosterone 6 beta-hydroxylation inhibition.

DESIGN

Rats were randomly allocated to 14 treatment groups for 10 days. The treatments included sham injection (n = 35), adrenocorticotrophin (5, 100, 500 micrograms/kg per day, subcutaneously, n = 5, 15 and 15, respectively), spironolactone (100 mg/kg per day, subcutaneously, n = 15), standard-dose or high-dose RU 486 (70 mg/kg every 3 days or 70 mg/kg per day, subcutaneously, n = 5 and 10, respectively), spironolactone + adrenocorticotrophin (100 micrograms/kg per day, n = 5, or 500 micrograms/kg per day, n = 10), standard-dose RU 486 + adrenocorticotrophin (500 micrograms/kg per day, n = 5), high-dose RU 486 + adrenocorticotrophin (100 micrograms/kg per day, n = 10), troleandomycin (40 mg/kg per day, subcutaneously, n = 5) and troleandomycin + adrenocorticotrophin (5 micrograms/kg per day, n = 5). Systolic blood pressure and metabolic parameters were measured every second day.

RESULTS

Adrenocorticotrophin treatment increased systolic blood pressure dose-dependently (5 micrograms/kg per day: +14 +/- 2 mmHg; 100 micrograms/kg per day: +20 +/- 2 mmHg; 500 micrograms/kg per day: +28 +/- 2 mmHg, all P < 0.001). Adrenocorticotrophin at 100 and 500 micrograms/kg per day increased plasma sodium and decreased plasma potassium concentrations. Spironolactone did not block adrenocorticotrophin-induced systolic blood pressure changes but did block changes in plasma sodium and potassium levels. Standard-dose RU 486 did not modify the adrenocorticotrophin-induced (500 micrograms/kg per day) systolic blood pressure rise but blocked the effect of adrenocorticotrophin on body weight. High-dose RU 486 partially blocked the adrenocorticotrophin-induced (100 micrograms/kg per day) systolic blood pressure increase (adrenocorticotrophin at 100 micrograms/kg per day: 143 +/- 3 mmHg; high-dose RU 486 + adrenocorticotrophin at 100 micrograms/kg per day: 128 +/- 5 mmHg, P < 0.001) and body-weight loss. Troleandomycin did not alter the development of adrenocorticotrophin-induced hypertension.

CONCLUSIONS

Spironolactone and standard-dose RU 486 did not modify adrenocorticotrophin-induced hypertension despite demonstrable antimineralocorticoid and antiglucocorticoid actions. High-dose RU 486 partially blocked adrenocorticotrophin-induced (100 micrograms/kg per day) hypertension, suggesting either a permissive effect of glucocorticoid on blood pressure or other antihypertensive actions of RU 486. Inhibition of glucocorticoid 6 beta-hydroxylation by troleandomycin did not modify adrenocorticotrophin-induced hypertension, suggesting that effects of corticosterone 6 beta-hydroxylation in adrenocorticotrophin-induced hypertension are negligible.

Causes and prevalence of non-vision impairing ocular conditions among a rural adult population in sw Uganda

Information is scanty about the extent of ocular morbidity in developing countries, particularly for non-vision impairing conditions (NVIC), although these constitute the majority of consultations in eye clinics. We have conducted a survey to determine the prevalence and causes of NVIC in a Ugandan adult population and compared our findings with the work pattern of the district hospital. Adults were screened using Snellen's illiterate E chart and those found with visual impairment (acuity less than 6/18) in either eye were referred to a low-vision clinic, and those with obvious ocular disease or symptoms, but without visual impairment, to an outreach clinic. A total of 2886 (53%) out of 5479 adults were screened. Of these, 257 (8.9%) were referred to the outreach clinic, of whom 173 (67%) attended. Of those attending the low-vision clinic 83% had visual impairment confirmed, and 92% of those attending the outreach clinic were confirmed not to have visual impairment. The four commonest NVIC observed at the outreach clinic were: presbyopia (48%), allergic conjunctivitis (20%), early cataract (9%) and infective conjunctivitis (8%), the same conditions as those most commonly seen at the district hospital. In this community, over 80% of NVIC are caused by four conditions which are potentially either correctable, operable or treatable. Training health workers to recognise and treat these conditions would serve the great majority of eye patients. Hospital activity data can be used cautiously to assess the relative frequency of NVIC in the community.

Endothelin-1 as a mediator in cardiovascular disease

1. Brachial artery infusion of endothelin (ET)-1 causes transient vasodilatation followed by sustained vasoconstriction of the forearm vascular bed, whereas ET-1 antagonists cause sustained vasodilatation. These data suggest that ET-1 contributes to basal vascular tone. 2. Systemic infusion of ET-1 increases blood pressure and total peripheral vascular resistance and reduces heart rate and cardiac output. The renal and pulmonary circulations are particularly sensitive to the vasoconstrictor effects of ET-1. Systemic infusion of the ETA/B receptor antagonist TAK-044 reduces mean arterial pressure and peripheral vascular resistance. 3. Plasma ET-1 concentrations are not elevated in essential hypertension; however, insulin resistance may be a major determinant of plasma ET-1 concentrations. Vascular sensitivity to ET-1 is normal or may be increased in essential hypertension. 4. Plasma ET-1 concentrations are increased in moderate and severe heart failure and are correlated with clinical and haemodynamic measures of severity. Endothelin-1 contributes to increased vascular tone in cardiac failure. 5. Plasma ET-1 concentrations increase following myocardial infarction and persistent elevation predicts an increased mortality within the subsequent 12 months. 6. Preliminary data suggest that interventions that reduce the activity of the endothelin system may have a beneficial effect in heart failure and myocardial infarction.

Independent evaluation of onchocerciasis rapid assessment methods in Benue State, Nigeria

OBJECTIVE

To evaluate the prevalence of palpable nodules or skin depigmentation as rapid indicators of onchocerciasis epidemicity in at-risk communities.

METHOD

We examined data collected in Benue State on 11035 individuals in 32 villages to evaluate these rapid assessment methods.

RESULTS

The prevalence of palpable nodules correlates more closely with microfilarial prevalence (r=0.68, P<0.001) and community microfilarial load (r=0.64, P<0.001) than the prevalences of skin depigmentation or other potential rapid indicators. The recommended cut-off value for palpable nodules of 20% or more in males aged >20 years had a sensitivity of 94% and specificity of 50% compared to a cut-off of 40% or more for microfilarial prevalence in all ages. This would mean that in these 32 villages 17 of 18 would have been correctly identified for treatment, and a further 7 at lesser risk would have been targeted for treatment.

CONCLUSIONS

Skin snipping and parasitological examination can be replaced by the simpler method of palpating onchocercal nodules to identify communities at serious risk of onchocerciasis. This has important operational benefits for onchocerciasis control programmes.

Difficulties in detecting parathyroid hypertensive factor in the rat

1. Parathyroid hypertensive factor (PHF) has been implicated in the pathogenesis of several forms of hypertension. We aimed to establish a PHF bioassay using spontaneously hypertensive rat (SHR) plasma. 2. Spontaneously hypertensive rats were confirmed hypertensive and their plasma was dialysed and injected into anaesthetized normotensive rats. 3. Haemodynamic responses to injected SHR plasma were uninterpretable during pentobarbital anaesthesia due to blood pressure (BP) fluctuation. Under halothane anaesthesia, BP was stable but did not rise following SHR plasma injection. Using filtered, undialysed plasma and a different brand of pentobarbital, no consistent BP response was observed following SHR plasma injection. 4. We were unable to detect PHF in the SHR.

The nitric oxide system and cortisol-induced hypertension in humans

1. The aim of the present study was to assess the role of the nitric oxide (NO) system in cortisol-induced hypertension in humans. 2. Plasma and urinary nitrate/nitrite concentrations and plasma concentrations of arginine and symmetric (SDMA) and asymmetric (ADMA) dimethyl arginine were measured in six subjects on a restricted nitrate diet who were treated with 80 mg/day cortisol and in subjects on an unrestricted nitrate diet who were treated with cortisol (80 mg/day, n = 6, or 200 mg/day, n = 10) for 5 days. 3. Cortisol significantly increased systolic and mean arterial pressure. Significant reductions in plasma nitrate/nitrite concentrations were observed in subjects on a restricted nitrate diet on days 3, 4 and 5 of cortisol treatment (to 11 +/- 1, 10 +/- 1, 11 +/- 1 pmol/L, respectively) compared with pretreatment (16 +/- 1 pmol/L; P < 0.01). There were no significant changes in plasma arginine, ADMA or SDMA concentrations. 4. Cortisol treatment significantly increased blood pressure and reduced plasma nitrate/nitrite concentrations. Reductions in plasma nitrate concentrations are not explained by changes in substrate availability or in endogenous nitric oxide synthase inhibitors. These data support a role for the NO system in cortisol-induced hypertension in humans.

Cortisol and hypertension

1. In humans, the hypertensive effects of adrenocorticotropic hormone (ACTH) infusion are reproduced by intravenous or oral cortisol. Oral cortisol increases blood pressure in a dose-dependent fashion. At a dose of 80-200 mg/day, the peak increases in systolic pressure are of the order of 15 mmHg. Increases in blood pressure are apparent within 24 h. 2. Cortisol-induced hypertension is accompanied by a significant sodium retention and volume expansion. Co-administration of the type I (mineralocorticoid) receptor antagonist spironolactone does not prevent the onset of cortisol-induced hypertension. Thus, sodium retention is not the primary mechanism of cortisol-induced hypertension. 3. Direct and indirect measures of sympathetic activity are unchanged or suppressed during cortisol administration, suggesting that cortisol-induced hypertension is not mediated by increased sympathetic tone. 4. Preliminary evidence in humans suggests that suppression of the nitric oxide system may play a role in cortisol-induced hypertension. 5. These potential mechanisms of cortisol action may be relevant in a number of clinical contexts, including Cushing's syndrome, apparent mineralocorticoid excess, the hypertension of liquorice abuse and chronic renal failure. There is also preliminary evidence suggesting a role for cortisol in essential hypertension.

Mortality impact of the AIDS epidemic: evidence from community studies in less developed countries

BACKGROUND

The AIDS epidemic is now more than a decade old and direct evidence of mortality impact has become measurable, as indicated by an increasing number of publications presenting empirical data from less developed countries.

METHODS

This review focuses on the evidence of mortality impact among adults and children in community studies. The majority of these studies are located in Africa, particularly eastern Africa, where the AIDS epidemic is conjectured to be older than in other less developed countries.

RESULTS

Community studies show a two- to threefold increase in total adult mortality with an even larger increase in mortality among young adults in communities with adult HIV prevalence levels below 10%. Mortality amongst HIV-infected adults ranges from 5 to 11% per year, and more than half of all adult deaths can be attributed to HIV. HIV-infected women die at an earlier age than men and thereby lose significantly more productive years of life. Follow-up studies of incident cases are few, but population-based data indicate that the median survival time is substantially longer than originally thought on the basis of mortality amongst HIV-infected commercial sex workers. Tuberculosis incidence is on the increase, but evidence of additional impact on mortality is hitherto limited. Infant and early child mortality among children of HIV-infected mothers is two to five times higher than among children of HIV-negative mothers in follow-up studies of maternity-based and community samples.

CONCLUSION

There is now empirical evidence of the mortality impact of HIV/AIDS from several community studies. The large increase in adult mortality and moderate increase in child mortality lead to dramatic falls in life expectancy. For instance, in a rural area of Uganda, which has an HIV prevalence of 8%, life expectancy has dropped from just under 60 years to 42.5 years.

Muscle sympathetic vasoconstrictor activity in hydrocortisone-induced hypertension in humans

AIM

This study was undertaken to test the hypothesis that increased sympathetic vasomotor drive is responsible for cortisol-induced hypertension.

METHODS

Ten healthy male subjects on a fixed sodium diet (150 mmol/day) were randomized to five days of treatment with cortisol (200 mg/day) or placebo in a double-blind crossover study. On day 5 of each treatment, multi-unit muscle sympathetic activity was recorded from the common peroneal nerve. Resting muscle sympathetic activity (MSA) was measured in the recumbent position and stimulated MSA was measured in the final 20 sec of end-inspiratory capacity apnoea and end-expiratory apnoea and in the second minute of a cold pressor stimulus. A subgroup of six subjects also underwent identical MSA measurements following 5 days treatment with dexamethasone (3 mg/day).

MAJOR FINDINGS

Cortisol, but not placebo, significantly increased systolic (115+/-2 vs 129+/-3 mmHg precortisol vs cortisol day 5, p < 0.001) and diastolic blood pressure (53+/-3 vs 61+/-3, p < 0.05). Resting MSA was significantly reduced by cortisol (23.9+/-2.3 to 5.0+/-2.0 bursts/min, placebo vs cortisol, p < 0.01). Cortisol significantly attenuated the increase in MSA observed at end-inspiratory apnoea (56.3+/-3.9 vs 35.4+/-6.6, p < 0.05) and end-expiratory apnoea (50.5+/-3.5 vs 26.3+/-6.2 bursts/min, n = 8, p < 0.05), and during the cold pressor response (55.0+/-12.7 vs 21.4+/-7.6, n = 5, p < 0.05). Dexamethasone significantly increased systolic blood pressure and suppressed resting and stimulated MSA. No changes in body weight, haematocrit or angiotensin II concentrations occurred during dexamethasone treatment.

CONCLUSION

MSA is significantly suppressed by cortisol treatment. As suppression of MSA is also observed during treatment with the pure glucocorticoid dexamethasone, suppressed MSA cannot be attributed to increased plasma volume or to changes in angiotensin II concentration. We conclude that cortisol-induced hypertension is not due to increased muscle sympathetic vasomotor drive.

Adrenocorticotrophin dose-response relationships in the rat: haemodynamic, metabolic and hormonal effects

OBJECTIVE

To determine adrenocorticotrophin dose-response relationships for increase of blood pressure and metabolic parameters of the Sprague-Dawley rat.

METHODS

We injected 120 male Sprague-Dawley rats twice daily subcutaneously for 10 days with 0.5, 1, 5, 50, 100, 200 or 500 microg/kg synthetic adrenocorticotrophin per day (all n = 10) or subjected them to sham injection (0.9% NaCl; n = 50). Systolic blood pressure, 24 h food intake, water intake, urine volume and body weight were measured. Data from a further 45 rats treated with 500 microg/kg per day adrenocorticotrophin in previous studies were included in the blood pressure analyses. After we had killed these rats, their organ weights (kidney, heart, adrenal) and plasma electrolyte, adrenocorticotrophin and serum corticosterone concentrations were measured.

RESULTS

On the final day of treatment systolic blood pressure of sham-injection control rats was 123 +/- 1 mmHg (n = 50). Compared with sham treatment, a low dose of adrenocorticotrophin (1 microg/kg per day) increased systolic blood pressure from 122 +/- 1 to 130 +/- 2 mmHg (P < 0.001) without any metabolic effects, whereas a high dose of adrenocorticotrophin (500 microg/kg per day) increased systolic blood pressure from 121 +/- 1 to 150 +/- 2 mmHg (P < 0.001, n = 55) with increases in intake of water and urine volume (P < 0.001, n = 10) and a decrease in body weight (P < 0.001, n = 10). Plasma adrenocorticotrophin and serum corticosterone concentrations for the sham-injection control group were 162 +/- 12 pg/ml (36 +/- 3 pmol/l) and 376 +/- 18 ng/ml (1038 +/- 50 nmol/l), respectively. Plasma adrenocorticotrophin concentration was elevated by injections of 100 (P < 0.05), 200 (P < 0.01) and 500 microg/kg adrenocorticotrophin per day (P = 0.001). Serum corticosterone concentration was not significantly different from that of sham-injection rats with 0.5-5 microg/kg adrenocorticotrophin per day but was increased by injection of 50-500 microg/kg adrenocorticotrophin per day (P < 0.001).

CONCLUSIONS

These results define 1 microg/kg adrenocorticotrophin per day, administered subcutaneously, as the threshold dose for causing a rise in blood pressure in the rat Thus administration of adrenocorticotrophin increases systolic blood pressure at doses that induce minimal adrenocorticotrophin metabolic effects. Administration of a low dose of adrenocorticotrophin to the rat is a suitable model for stress-induced hypertension.

Hemodynamic profile of corticotropin-induced hypertension in the rat

OBJECTIVES

To examine hemodynamic variables in corticotropin-induced hypertension in rats and the effects of reversal of the hypertension by L-arginine on the hemodynamic profile.

METHODS

Sixty male Sprague-Dawley rats were randomly divided into four groups: sham treatment (0.9% NaCl, injected subcutaneously); 0.5 mg/kg corticotropin per day, subcutaneously; 0.6% L-arginine in food plus sham; and L-arginine plus corticotropin. Systolic blood pressure, water and food intakes, urine volume, and body weight were measured every second day. After 10 days mean arterial blood pressure was measured by intra-arterial cannulation, and cardiac output, and renal, mesenteric, and hindquarter blood flows were determined using transonic small animal flowmeters.

RESULTS

Injection of corticotropin increased blood pressure, water intake, urine volume, and plasma sodium concentration, and decreased body weight and plasma potassium concentration. It increased cardiac output (P < 0.01), mesenteric blood flow (P < 0.05), and renal vascular resistance (P < 0.05), and decreased renal blood flow (P < 0.05), but did not change calculated total peripheral resistance, hindquarter blood flow, mesenteric or hindquarter vascular resistance. L-arginine prevented corticotropin-induced rises in blood pressure (P < 0.001) and renal vascular resistance (P < 0.05), and a fall in renal blood flow (P < 0.05), but did not affect other hemodynamic variables.

CONCLUSION

The hemodynamic profile of corticotropin-induced hypertension in the rat is characterized by a rise in cardiac output and renal vascular resistance, a fall in renal blood flow, but no change in total peripheral resistance, hindquarter blood flow, mesenteric vascular resistance, or hindquarter vascular resistance. L-arginine prevented corticotropin-induced rises both in blood pressure and in renal vascular resistance in the rat. These data suggest that the increase in renal vascular resistance might play a role in corticotropin-induced hypertension in the rat.

Hypotensive effects of peptide T in conscious rats

1. The present study investigated the effects of peptide T on mean arterial blood pressure (MAP) in conscious normotensive Sprague-Dawley (SD) rats, spontaneously hypertensive rats (SHR) and two-kidney one-clip (2K1C) hypertensive rats. 2. Peptide T was infused via the left jugular vein at a rate of 1 mg/kg per h in SD, SHR and 2K1C rats and then at doses of 0.1, 0.25, 0.5, 1 and 5 mg/kg per h in SHR, with 0.9% saline as a sham control in SHR and 2K1C. Mean arterial pressure was measured directly before, during and after infusion. 3. Peptide T (1 mg/kg per h) decreased blood pressure in both SHR (P < 0.01) and 2K1C (P < 0.05). In normotensive SD rats the fall in MAP approached statistical significance (P = 0.06). The effect of peptide T was not significantly different in normotensive compared with hypertensive rats. Saline infusion had no effect. The blood pressure lowering effect of peptide T appeared to be dose-dependent in SHR.

Dexamethasone-induced hypertension in the rat: effects of L-arginine

1. The effects of L-arginine treatment on dexamethasone-induced hypertension were examined in the Sprague-Dawley rat. Seventy rats were randomly divided into the following eight groups: sham, dexamethasone (5 and 10 micrograms/day, L-arginine (100 and 500 mg/kg per day), L-arginine (100 or 500 mg/kg per day) + dexamethasone (10 micrograms/day), L-arginine (520-797 mg/kg per day in food) + dexamethasone (5 micrograms/day). Systolic blood pressure (SBP), bodyweight and plasma nitrate/nitrite concentration were measured. 2. Dexamethasone (5 and 10 micrograms/day) increased SBP in both sham and L-arginine-treated rats. Dexamethasone at 10 micrograms/day decreased bodyweight, but did not alter plasma nitrate/nitrite concentrations. 3. L-Arginine (500 mg/kg per day, i.p.) increased plasma nitrate/nitrite concentrations in 10 micrograms/day dexamethasone-treated rats. L-Arginine did not alter blood pressure in either sham or dexamethasone-treated rats. 4. Dexamethasone-induced hypertension differs from adrenocorticotropic hormone (ACTH)-induced hypertension in the rat in that it is not modified by L-arginine. Thus, ACTH-induced hypertension cannot be explained simply in terms of glucocorticoid activity.

Measuring venous capacitance and blood flow in pregnancy

Forearm or calf venous plethysmography has been used in pregnant women to examine the effects of pregnancy on the vascular system and more recently to measure blood flow changes in response to intra-arterial infusion of vasoactive substances. To examine the assumption that venous capacitance and blood flow measurements are the same in the forearm and calf, venous plethysmography was conducted simultaneously on the forearm and calf in normal (NP) and hypertensive pregnant women (HTP) in their third trimester and in normal nonpregnant women (N). All studies were made on the right forearm and calf with subjects in the left lateral recumbent position. There was no significant difference between venous capacitance in the forearm (median: 124 x 10(3)mL/100mL/mmHg for both NP and HTP) and leg (134 [NP] and 106 [HTP] x 10(3)mL/100mL/mmHg) for both pregnant groups but venous capacitance in the nonpregnant group was greater in the leg than arm (174 versus 112 x 10(3)mL/100mL/mmHg, p < 0.001). Blood flow was similar in the leg and forearm (median 4.9 versus 3.9mL/100mL/min respectively) in nonpregnant women. Forearm blood flow was also similar to calf flow in NP women (6.2 versus 4.3mL/100mL/min respectively) but greater than calf blood flow in HTP (9.7 versus 5.3mL/100mL/min, p < 0.01). Using left lateral recumbency, forearm and calf vein capacitances are similar in pregnant women, in contrast to nonpregnant women. Blood flow is higher in the forearm than the calf only in hypertensive pregnant women. These observations should be borne in mind when interpreting studies of regional blood flow in pregnancy.

HIV-1 disease progression and AIDS-defining disorders in rural Uganda

BACKGROUND

The majority of people infected with HIV-1 live in Africa, yet little is known about the natural history of the disease in that continent. We studied survival times, disease progression, and AIDS-defining disorders, according to the proposed WHO staging system, in a population-based, rural cohort in Uganda.

METHODS

In 1990 we recruited a random sample of people already infected with HIV-1 (as prevalent cases) detected during the initial survey round of a general-population study to form a natural-history cohort. Individuals from the general-population cohort who seroconverted between 1990 and 1995 (incident cases) were also invited to enroll. Participants were seen routinely every 3 months and when they were III.

FINDINGS

By the end of 1995, 93 prevalent cases and 86 incident cases had been enrolled. Four patients in the prevalent group were in stage 4 (AIDS) at the initial visit. During the next 5 years, 37 prevalent cases progressed to AIDS. Seven incident cases progressed to AIDS and the cumulative progression to AIDS at 1, 3, and 5 years after seroconversion was 2%, 6%, and 22%, respectively. The cumulative probability of AIDS at 4 years from entering stages 1, 2, and 3 was 11%, 33%, and 58%, respectively. There were 47 deaths among prevalent cases and seven among incident cases during follow-up. The cumulative mortality 4 years after patients entered stages 1, 2, 3, and 4 was 9%, 33%, 56%, and 86%, respectively. The median survival after the onset of AIDS was 9.3 months.

INTERPRETATION

Our results are important for the setting of priorities and rationalisation of treatment availability in countries with poor resources. We found that progression rates to AIDS are similar to those in developed countries for homosexual cohorts and greater than for cohorts infected by other modes of transmission. However, we have found that the rates of all-cause mortality are much higher and the progression times to death are shorter than in developed countries.

The renin-angiotensin-aldosterone system in pre-eclampsia

Pre-eclampsia is characterised physiologically by plasma volume contraction, intravascular coagulation and intense vasoconstriction. It was originally thought that the renin-angiotensin-aldosterone (RAA) system would be overactive but studies have shown a more complex picture. Plasma renin activity (PRA) and concentration (PRC) and plasma angiotensin II (AII) and aldosterone concentrations (PAC) are reduced compared to normal pregnancy. Total renin concentration is normal and plasma concentrations of high molecular weight angiotensinogen are increased in pre-eclampsia though total angiotensinogen is normal. PRA and PRC respond appropriately to physiologic stimuli in pre-eclampsia except for impaired renin release following frusemide, possibly due to prostacyclin deficiency. Although plasma AII concentrations are reduced there is heightened pressor sensitivity to infused AII--the mechanism(s) for this are unknown. PAC is reduced but the ratio PAC-PRC is twofold greater in pre-eclampsia than normal pregnancy. This does not appear to be due to changes in potassium, atrial natriuretic peptide, dopamine or ACTH, and may be another manifestation of increased (adrenal) sensitivity to AII in pre-eclampsia. There is an inverse relationship between the plasma active renin to prorenin ratio and the clinical severity of the pre-eclampsia. Understanding the mechanisms producing these changes in the RAA system in pre-eclampsia will give strong clues to the overall pathogenesis of this disorder.

Glucocorticoids and hypertension in man

Abnormalities of cortisol production or metabolism are involved in the genesis of hypertension in Cushing's syndrome, apparent mineralocorticoid excess and liquorice abuse and possibly in chronic renal failure and essential hypertension. We have studied the physiological mechanisms by which cortisol raises blood pressure in short term studies of cortisol administration in normal men. Cortisol induced hypertension cannot be explained by increases in vasopressor or decreases in vasodepressor hormone concentrations, or by any increase in sympathetic nervous activity. The hypertension is accompanied by substantial sodium retention but a significant component of the blood pressure rise is sodium independent. The hypertension is characterized by an increase in cardiac output but a rise in output is not essential for the rise in blood pressure. Our working hypothesis is that cortisol induced hypertension is a consequence of increases in renal vascular resistance.

Effects of diet on measurement of nitric oxide metabolites

1. The present study investigated whether a low nitrate/nitrite diet could minimize variability in the measurement of endogenous plasma and urine nitric oxide (NO) metabolites, nitrate and nitrite (NOx) in normal subjects. 2. Nitrate and nitrite concentrations were measured in plasma and urine as indicators of NO production in six subjects during a free diet and then during a low nitrate/nitrite diet for 6 days. 3. The plasma concentration and 24 h urine NOx/creatinine ratio were significantly lower on the low nitrate/nitrite diet than on the free diet (P < 0.01). Nitric oxide production appeared to vary greatly within and between subjects, but these variations were substantially decreased by the fourth day of a low nitrate/nitrite diet. 4. Human plasma and urine NOx measurements should be determined after a low nitrate/nitrite diet for at least 4 days.

Reflex sympathetic function in cortisol-induced hypertension in humans

Nine healthy male subjects underwent measurement of reflex sympathetic function, pressor responsiveness and baroreflex sensitivity to phenylephrine (PE) and glyceryltrinitrate (GTN) before (C1) and following six days of treatment (E6) with cortisol (F), 200 mg/day. Seven subjects had washout studies (W) performed at least two weeks following the end of treatment. The BP responses to head tilt, isometric exercise and mental arithmetic were unaltered by F, however, there was a significant diminution of the diastolic BP response to cold pressor stimulus (delta DBP: 19 +/- 3 vs 25 +/- 5 vs 27 +/- 5 mmHg; E6 vs C1 vs W, p < 0.05 C1 vs E6 and W). Baroreflex sensitivity to PE was increased (28 +/- 3 vs 19 +/- 2 ms/mmHg, E6 vs C1, p = 0.03). These data demonstrate that increased BP during F treatment is not attributable to increased SNS activity, and suggest that SNS activity may be decreased by F.

The role of the hypothalamic-pituitary-adrenal (HPA) axis in the regulation of blood pressure

The role of the HPA axis in blood pressure regulation was examined in 6 normal male volunteers by comparing haemodynamic and hormonal effects of placebo, captopril, and dexamethasone given in random order for two days. The average 24-hour systolic and mean arterial pressures on placebo (135 +/- 6 and 93 +/- 2 mmHg respectively) were significantly higher than on captopril (118 +/- 1 and 85 +/- 1 mmHg respectively, p < 0.05) but there were no significant changes on dexamethasone compared with placebo (128 +/- 3 and 89 +/- 3 mmHg respectively). There were no differences in the average 24-hour diastolic blood pressures or heart rates, nor the day-night differences, night:day ratios or percentage changes in blood pressure and heart rate between treatments. Captopril significantly increased active plasma renin concentration, whilst dexamethasone decreased cortisol concentration. These results confirm the role of the renin-angiotensin system in the regulation of blood pressure in normal subjects but suggest that the HPA axis does not play a major role in determining ambulatory blood pressure or day-night variability in the short term.

An HIV-1 natural history cohort and survival times in rural Uganda

OBJECTIVE

To describe a population-based rural cohort of HIV-1-seropositive and seronegative individuals established in 1990 in south-west Uganda, and determine survival times in the cohort.

DESIGN

Prospective cohort study.

METHODS

Participants were recruited from a large population study, and invited to attend a clinic every 3 months. They were seen by clinicians who administered detailed medical questionnaires and undertook a physical examination.

RESULTS

By the end of 1995, 390 (79%) of the 491 people asked to enrol in the natural history cohort (NHC) had done so. Ninety-three were prevalent cases of HIV infection detected during the initial survey round of the general population cohort in 1989/1990, 66 were subsequent incident cases, 177 were age-matched HIV-negative controls and 54 were HIV-negative spouses of HIV-positive individuals. Twenty participants seroconverted in the NHC. The age-standardized mortality rates per 1000 person-years for the prevalent, incident, and negative cases were 156.5 [95% confidence interval (CI), 115.8-211.4], 35.0 (95% CI, 16.4 75.0) and 13.5 (95% CI, 7.3-25.1), respectively. The median survival time from enrolment to death for the prevalent cases was 4.5 years (95% CI, 3.5- > 5.2); > 5.4 years from seroconversion for the incident cases; and > 5.2 years from enrolment for the HIV-negative cases. The 5-year cumulative survival for prevalents, incidents and HIV-negative participants was 46%, 83% and 94%, respectively.

CONCLUSIONS

We have described an NHC of HIV-positive and HIV-negative participants which is representative of the general population. The NHC was established over 5 years ago; it is continuing and we are maintaining good compliance rates. Survival probabilities in the cohort were lower than most other reported studies.

Hemodynamic effects of the Fab fragment of digoxin antibody (digibind) in corticotropin (ACTH)-induced hypertension

To determine whether the immune Fab fragment of digoxin antibody (digibind) attenuates established corticotropin (ACTH) hypertension, rats were given ACTH sham control (0.1 mL normal saline, twice daily, subcutaneously, n = 18) or ACTH treatment (2.5 microg/kg in 0.1 mL normal saline, twice daily, subcutaneously; n = 27) for 10 days. Acute hemodynamic effects of digibind (30 mg/kg, intravenous bolus injection) were examined after 10 days of sham control or ACTH treatment. Rats were divided into 7 groups: digibind (30 mg/kg, in 1 mL 0.9% NaCl intravenous bolus injection) plus sham (n = 6) or ACTH (n = 8), sham digibind (1 mL 0.9% NaCl intravenous bolus) plus ACTH (n = 7), digibind vehicle (sorbitol 1.8 mg in 1 mL 0.9% NaCl, intravenous bolus) plus sham (n = 6), preimmune sheep IgG (30 mg/kg in 1 mL 0.9% NaCl intravenous bolus) plus sham (n = 6) or ACTH (n = 6) and preimmune sheep IgG (Fab)2 fragment (30 mg/kg in 1 mL 0.9% NaCl intravenous bolus) plus ACTH (n = 6). ACTH increased systolic blood pressure (SBP) from 118 +/- 2 to 132 +/- 3 mm Hg on treatment day 10. BP was unchanged in sham treated rats. The acute administration of digibind decreased MAP (-14 +/- 3 mm Hg, P <.001) in ACTH hypertensive rats, but not in ACTH sham control normotensive rats (+2 +/- 3 mm Hg). Blood pressure reached a minimum after 14 +/- 3 min and the effect lasted more than 30 min. No significant change of blood pressure was found in ACTH treated rats receiving sham (0.9% NaCl) digibind injection (+2 +/- 2 mm Hg). However, both preimmune sheep IgG and IgG (Fab)2 fragment caused a decrease of blood pressure in both sham or ACTH treated rats. Although these data that digibind decreases BP in ACTH but not sham treated rats are consistent with the notion that digitalis-like substances may play a role in ACTH induced hypertension, the evidence that both preimmune sheep IgG and IgG (Fab)2 fragments also decreased blood pressure in rats suggests caution in interpretation of studies that employ digibind preparations.

Autonomic blockade amplifies cortisol-induced hypertension in man

1. We investigated the role of the autonomic nervous system (ANS) in cortisol induced hypertension using the technique of total autonomic blockade (AB). 2. Four healthy young males were given 50 mg cortisol 6 hourly for 6 days. On the day prior to, and the last day of, cortisol treatment, AB was produced using oral prazosin 1 mg, intravenous clonidine 300 micrograms, propranolol 0.2 mg/kg and atropine 2 mg. The adequacy of blockade was assessed using the haemodynamic response to Valsalva manoeuvre. 3. Cortisol produced a significant rise in systolic blood pressure (130 +/- 2 vs 110 +/- 1 mmHg, pre vs post cortisol; P < 0.01). On the final treatment day, AB augmented the increase in diastolic blood pressure (delta DBP), mean arterial pressure (delta MAP) and heart rate (delta HR) compared to the pretreatment day, delta DBP: 43 +/- 6 vs 17 +/- 4 mmHg, post vs pre cortisol, P < 0.005, delta MAP: 39 +/- 4 vs 14 +/- 4 mmHg, P < 0.001, delta HR: 45 +/- 5 vs 26 +/- 4 b.p.m., P < 0.05. The change in systolic blood pressure (delta SBP) was not statistically significant (32 +/- 4 vs 7 +/- 3 mmHg, P = 0.065). 4. These results suggest that the ANS exerts a modulating influence on the hypertensive effect of cortisol.

Clinical and parasitological responses after up to 6.5 years of ivermectin treatment for onchocerciasis

There are plans to use mass treatment with ivermectin to clear all Africa of the worst ocular and cutaneous effects of onchocerciasis. However, there remains uncertainty about the most suitable treatment regimen and the likely effects of ivermectin on onchocercal skin disease. We have followed 948 subjects for over 6 years in a double-blind, randomized, controlled study of ivermectin for onchocerciasis in a hyperendemic focus in Sierra Leone. Using an intention-to-treat analysis we found a microfilarial prevalence of 16% 6 months after up to 4 annual doses of ivermectin, and 13% prevalence in the group receiving up to 10 doses of ivermectin at 6-monthly intervals. Microfilarial loads were well suppressed in both groups, but repopulation data suggest that adult female worms are still alive and fecund, strongly underlining the need to continue treatment. A clear effect of ivermectin was demonstrated on itching, with about one-third of cases being alleviated. Significant reductions in the prevalence of serious hyperkeratosis, and possibly dyspigmentation (leopard skin), were noted, but not for any other onchocercal skin lesion. Six-monthly and annual treatment regimens with ivermectin were equally effective in terms of dermatological and parasitological impact.

Dose-response relationships and mineralocorticoid activity in cortisol-induced hypertension in humans

OBJECTIVE

This study was designed to define the dose-response relationships for cortisol-induced hypertension in humans and to test the hypothesis that cortisol-induced hypertension is a consequence of classical mineralocorticoid actions using the mineralocorticoid antagonist spironolactone.

METHODS

In study 1, six normal men were given cortisol orally every 6 h for 5 days at doses of 40, 80 and 200 mg per day. In study 2, six normal men were given spironolactone at 400 mg/day for 6 days and cortisol at 80 mg/day for 5 days, commencing on the second day of spironolactone treatment.

RESULTS

Systolic blood pressure increased significantly with cortisol at 80 and 200 but not 40 mg/day. There was no difference between 80 and 200 mg/day. Weight increases were seen at the two higher doses and serum potassium concentration fell with each dose. Spironolactone prevented the increase in body weight and the decrease in serum potassium but did not affect the increase in blood pressure produced by cortisol.

CONCLUSIONS

Cortisol at 80 and 200 mg per day produces similar blood pressure and metabolic effects. Spironolactone blocked the mineralocorticoid effects of cortisol but not the blood pressure rise, suggesting that these mineralocorticoid effects are not responsible for cortisol-induced hypertension.

Ambulatory blood pressure monitoring (ABPM) in the normal menstrual cycle and in women using oral contraceptives. Comparison with conventional blood pressure measurement

This study was undertaken to determine if blood pressures (BP) assessed by routine sphygmomanometry and 24 h ambulatory monitoring (ABPM) alter throughout the normal menstrual cycle or in the cycle of women using oral contraceptive pills (OCP), and the interrelationships between urinary sodium (Na) and potassium (K) excretion and ABPM throughout the menstrual cycle. Eleven women with a normal ovulatory cycle (ovulatory) and ten age-matched women taking an oral contraceptive pill (OCP) were studied three times in random order during their menstrual cycle, within days 1 to 5, 13 to 16, and 25 to 28. Twenty-four hour urine Na, K, and creatinine (Cr) excretion and serum Na, K, Cr, cortisol, estradiol, progesterone and plasma renin, angiotensinogen, and aldosterone concentrations were measured. BP was measured by a mercury sphygmomanometer and by 24 h BP (Accutracker II). On days 1 to 5, daytime systolic BP was higher in OCP [mean: 123 mm Hg, 95% confidence interval: 117, 128] than ovulatory women [114 mm Hg (109, 118); P = .011] though daytime diastolic BPs were similar [OCP: 71 (68, 75), ovulatory: 69 (66, 72)]. This difference in daytime systolic BP between groups was also apparent at both of the other stages of the menstrual cycle. Nighttime systolic BPs were significantly higher in OCP users on days 13 to 16 (P < .05) and days 25 to 28 (P < .01). In women taking OCPs, daytime ABPM for days 1 to 5 were higher than their office readings by 15 (7,23)/11 (7,15) mm Hg (P = .001), whereas office and ABPM readings were similar in ovulatory women. This pattern was evident at all three stages. There was no significant change in BP throughout the menstrual cycle within either group, and no correlation between urine Na or K and BP. Systolic BPs are higher throughout the menstrual cycle in women who take OCPs than in ovulatory women but this difference is only detected when ambulatory blood pressure is assessed. Blood pressure does not change subsequently in either ovulatory or OCP-taking women throughout the menstrual cycle.

Viability and fertility of adult Onchocerca volvulus after 6 years of treatment with ivermectin

Onchocerca volvulus nodules were removed from 77 fully compliant patients in a longitudinal study of ivermectin treatment in Sierra Leone. The patients had participated in a randomized controlled trial and received either 4 annual doses of ivermectin or 10 6-monthly doses over 6 years. Worms were examined 9 months after the last treatment for evidence of changes in morphology, viability and reproductivity. The findings were compared with results for the 2 groups obtained at earlier surveys of the same study population. Repeated treatment at 6 and 12-month intervals has resulted in a marked ageing of the male worm population profile and a significant reduction in the proportion of live female worms found in the nodules. In addition, there has been a reduction in reproductivity of 90% or more. However, most of the worms found were still alive and potentially fertile, underlining the need for the continuation of regular ivermectin treatment to maintain the benefits achieved.

Maintaining compliance to ivermectin in communities in two West African countries

We have investigated various aspects related to managing wide-scale ivermectin distribution schemes within randomized controlled trials in communities where onchocerciasis is endemic. Multiple logistic regression analysis of determinants of compliance to five doses of ivermectin in 589 people in Sierra Leone showed independent significant associations with leopard skin depigmentation, the severity of side effects of treatment, fulfilling the exclusion criteria for treatment, and long-term residence in the community. These results are useful for tailoring health promotion messages in Sierra Leone, but the associations may differ in other West African societies. In Nigeria 1847 people were interviewed about various subjective responses, including itching. None of these showed clear improvement after three years of ivermectin treatment. Positive comments about treatment were generally non-specific and similar in the placebo and ivermectin groups. Negative comments were usually related to adverse reactions, especially itching and rash, and were more common after ivermectin. The lack of any benefit attributable to ivermectin that is discernible to its recipients may make it difficult to maintain the high compliance rates needed for long periods if mass dosing programmes are to have a lasting impact on onchocerciasis. In addition, no consistent effects of ivermectin were found by measuring visual acuity, height, weight or haematocrit in comparison with placebo. This may indicate that evidence of clinical impact is very slow to develop and is hard to measure using simple objective methods after only three doses of treatment. At present it seems that parasitological, entomological and detailed ophthalmological or dermatological methods are required to demonstrate the impact of ivermectin treatment in the medium-term.

Primary hyperaldosteronism: a missed diagnosis in 'essential hypertensives'?

BACKGROUND

It has been recognised recently that primary hyperaldosteronism may be more common than previously thought, the frequency of diagnosis being improved by screening using a plasma aldosterone concentration to renin activity ratio.

AIMS

To determine the frequency of primary hyperaldosteronism, screening with both plasma aldosterone to renin concentration (PRC) and activity (PRA) ratios, in normokalaemic subjects previously diagnosed as having essential hypertension.

METHODS

Plasma potassium, aldosterone and PRCs and PRA and blood pressure (BP) were measured in 74 hypertensive subjects previously diagnosed by one physician as having essential hypertension. A normal range for plasma aldosterone/renin ratios was determined in 147 control subjects. Hypertensive subjects with elevated aldosterone/renin ratios were further assessed for primary hyperaldosteronism using saline loading and fludrocortisone suppression. Those in whom plasma aldosterone concentration exceeded 140 pmol/L after suppression tests underwent adrenal vein sampling for measurement of aldosterone and cortisol concentrations as well as adrenal CT scanning to diagnose the cause of primary hyperaldosteronism. The main outcome measures were a diagnosis of aldosterone producing adenoma or bilateral adrenal hyperplasia based upon adrenal vein sampling.

RESULTS

Four subjects (5%) had an elevated plasma aldosterone to renin ratio using PRC and six (8%) using PRA. Two subjects (2.7%) in this selected population had primary hyperaldosteronism, both of whom had BP > 160/110 mmHg at the time of testing.

CONCLUSIONS

The frequency of normokalaemic primary hyperaldosteronism appears to be greater than previously thought, though the true incidence in the general population of hypertensive subjects remains unknown. The sensitivity of diagnosis (but not specificity) may be improved by measurement of the plasma aldosterone/renin ratio and PRC is at least as adequate as PRA for this process.

Human isotype antibody responses to an Onchocerca volvulus glutathione S-transferase

Human isotype specific antibody responses to a recombinant pi-class glutathione S-transferase (Ov24) from Onchocerca volvulus were assessed by ELISA, using a large and well-characterized bank sera (n = 238) from an hyper-endemic area of moderate intensity from Sierra Leone. IgG1, IgG4 and IgA responses, but neither IgG2 nor IgE response, to Ov24 were detected in infected subjects. The relationships between Ov24 antibody levels and skin microfilarial density, number of nodules, age, sex, eosinophil counts and clinical sign of reactive and chronic pathology were analysed using Pearson's correlation coefficient. Significant correlations between both IgA and IgG3 antibody levels and age were found (P < 0.01). Although no firm conclusions could be drawn from this study sample regarding the relationships between antibody levels and parasite load or clinical status, a negative correlation (P = 0.06) between Ov24 IgG3 antibody levels and microfilarodermia was found.

The effects of multiple doses of ivermectin on ocular onchocerciasis. A six-year follow-up

BACKGROUND

Ivermectin has been shown to be a safe treatment for onchocerciasis and is now being distributed through mass treatment programs. Previous studies of up to 3 years of treatment have demonstrated that ivermectin improves anterior segment lesions and reduces the incidence of optic atrophy. The benefit of multiple doses of ivermectin on visual acuity and chorioretinitis has yet to be shown.

METHODS

A community-based, double-blind, randomized, controlled trial of ivermectin was started in Bo, Sierra Leone, in 1987. Two cohorts are reported in this study: (1) 214 subjects had received four 6-month doses of ivermectin followed by up to six additional 6-month treatments. The second cohort, with 185 subjects, had received four 6-month doses of placebo followed by up to four annual doses of ivermectin. All subjects received a full ophthalmic examination in 1989 and again in 1994. For both cohorts, there was an 18-month gap between the fifth and sixth rounds of treatment.

RESULTS

There was no significant difference in the prevalences of any ocular lesion nor of visual acuity categories between the cohorts at the second examination. Comparisons of the prevalences of anterior segment lesions for both cohorts combined between the first and second examinations show highly significant improvement (P < 0.001) for all lesions. Posterior segment lesions show a more variable pattern, with chorioretinitis showing highly significant deterioration (P < 0.001) and the emergence of new lesions in both groups.

CONCLUSION

The authors conclude that annual treatment with ivermectin is effective in controlling ocular onchocerciasis apart from chorioretinal lesions and that a 6-month treatment gives no additional benefit.

Angiotensin converting enzyme inhibition and protein restriction in progression of experimental chronic renal failure

This study examined whether the effects of protein restriction and angiotensin converting enzyme (ACE) inhibition on the progression of renal failure are common or additive. Male Sprague Dawley rats (12 wks of age) underwent 5/6 nephrectomy and were randomized to 20% protein diet (PD) (n = 9), 20% PD+enalapril (5 mg/kg/day) (n = 10), 20% PD+felodipine (30 mg/kg/day) (n = 9), 6% PD (n = 9), 6% PD+enalapril (n = 9) or 6% PD+felodipine (n = 10). Protein restriction, enalapril or felodipine treatment all retarded progression of renal failure and development of glomerular lesions. Protein restriction and enalapril appeared to have additive effects in preventing glomerular sclerosis.

Dehydroepiandrosterone does not prevent adrenocorticotrophin-induced hypertension in conscious rats

1. We tested the hypothesis that dehydroepiandrosterone (DHEA), which prevents dexamethasone-induced hypertension in rats, may block adrenocorticotrophin (ACTH) hypertension, which has been presumed due to corticosterone excess. The blood pressure and metabolic effects of DHEA (18 mg/kg per day) were examined in sham and ACTH-treated (0.5 mg/kg per day) conscious Sprague-Dawley rates (n = 20). 2. ACTH but not sham injection increased blood pressure, water intake and urine output and decreased bodyweight. 3. DHEA administration for 10 days did not alter blood pressure or metabolic effects in either sham or ACTH-treated rats. 4. DHEA, which is known to block dexamethasone-induced hypertension, did not modify ACTH-induced hypertension in the rat. This suggests either that ACTH-induced hypertension is not simply a consequence of glucocorticoid activity or that the action of DHEA in dexamethasone hypertension is not through blocking the glucocorticoid receptor.

Validation of transonic small animal flowmeter for measurement of cardiac output and regional blood flow in the rat

The objective of the present study was to validate a transonic flowmeter system with two probes (model 3SS for cardiac output (CO) and 1RB for organ flows) in Sprague-Dawley (SD) rats first by measuring blood flow through pump-infused isolated renal artery and ascending aorta, and then through measurements of CO and renal, mesenteric, and hindquarter blood flow (RBF, MBF, HBF) in vivo. We measured in vivo baseline flow and changes in flow induced by dopamine and propranolol for CO, prostaglandin E2 (PGE2), and angiotensin II (AII) for RBF and pentobarbital sodium for MBF and HBF. Correlations between meter and pump flow were linear (r = 0.999, p < 0.001) with close agreement both in ascending aorta and renal artery flow measurements. The baseline values were 15 +/- 0.7 ml/100 g/min for CO, 4 +/- 0.1 ml/100 g/min for RBF, 7 +/- 0.3 ml/100 g/min for MBF, and 6 +/- 0.3 ml/100 g/min for HBF, respectively. The system reliably detected increase and/or decrease in CO and regional blood flows. The transonic flowmeter system is accurate, highly reproducible, and compatible with other established techniques for measuring CO and regional blood flows in the rat.

Angiotensin-converting enzyme inhibition in nondiabetic progressive renal insufficiency: a controlled double-blind trial

Angiotensin-converting enzyme inhibitors delay progression of renal disease in different animal models of nephropathy. We tested this treatment modality in 70 hypertensive patients with severe renal disease of various etiologies. We report a double-blind study of the effect of 5 mg enalapril once daily compared with placebo in patients with nondiabetic severe chronic renal impairment (plasma creatinine 2.8 to 6.8 mg/dL; mean creatinine clearance 15 mL/min/1.73 m2) followed for up to 2 years. Efficacy parameters were the slopes of 51Cr-EDTA clearance, reciprocal of plasma creatinine, creatinine clearance, and the effect on urinary protein excretion. Thirty-one patients completed 2 years of treatment (12 in the enalapril group and 19 in the placebo group). Two patients died from nonrenal causes (one patient each in the enalapril and placebo groups), 16 patients commenced dialysis (seven in the enalapril group and nine in the placebo group), and eight patients were discontinued due to adverse events (five in the enalapril group and three in the placebo group). Eleven patients were discontinued because they were noncompliant, uncooperative, or moved (nine in the enalapril group and two in the placebo group). Two enalapril-treated patients were dropped from the study due to protocol deviations. Importantly, the statistical approach in this study evaluated all patients, regardless of the duration of treatment. A mixed-effects linear model and intention to treat analysis, taking into account the number of observations per patient, indicated that enalapril significantly reduced the rate of deterioration of renal disease: glomerular filtration rate (P = 0.038), reciprocal of plasma creatinine (P = 0.017), or creatinine clearance (P = 0.031). The renal protective effects of enalapril were shown to be in addition to its antihypertensive effect when blood pressure was held constant. Proteinuria was reduced by enalapril (P = 0.007) and was slightly increased in the placebo-treated patients (P = 0.051). The difference between these two groups was highly significant (P = 0.002). In conclusion, enalapril retarded the progression of chronic renal failure, as assessed by changes in glomerular filtration rate, creatinine clearance, and 1/plasma creatinine, and reduced proteinuria in patients with nondiabetic severe chronic renal insufficiency.

Preeclampsia: the effects of serum on endothelial cell prostacyclin, endothelin, and cell membrane integrity

OBJECTIVE

Our purpose was to determine whether serum from women with preeclampsia or gestational hypertension (1) decreased endothelial cell prostacyclin, (2) increased endothelial cell endothelin, and (3) caused endothelial cell damage.

STUDY DESIGN

Production of 6-keto-prostaglandin F1 alpha and endothelin by cultured endothelial cells was measured after 48 hours' incubation with sera from 23 nonpregnant women, 23 normal pregnant women, 12 women with preeclampsia, and 11 women with gestational hypertension. Structure damage of endothelial cells was assessed by a chromium release assay.

RESULTS

Serum from normal pregnant women induced more endothelial prostacyclin but less endothelin than did serum form nonpregnant women (p<0.05). No difference was found between normal pregnant and hypertensive pregnant women for prostacyclin production, but serum of preeclamptic women induced less endothelin production than did that of normal pregnant women (p<0.05). Chromium 51 release by endothelial cells was similar between normal pregnant and hypertensive pregnant groups.

CONCLUSIONS

Serum from preeclamptic women stimulates less endothelin production than does serum from normal pregnant women but does not alter prostacyclin production and is not cytotoxic to endothelial cells after short-term incubation.

L-arginine prevents corticotropin-induced increases in blood pressure in the rat

In this study we examined whether L-arginine treatment could prevent corticotropin (ACTH)-induced increases in blood pressure in the Sprague-Dawley rat. Sixty rats were randomly divided into six groups (n = 10): sham injection, ACTH injection (0.5 mg/kg per day in divided doses), L-arginine (0.6%) in food plus sham injection, L-arginine plus ACTH treatment, D-arginine (0.6%) in food plus sham injection, and D-arginine plus ACTH. Systolic pressure, water intake, urine volume, body weight, plasma and urinary electrolytes, and serum corticosterone concentrations were measured. ACTH increased systolic pressure (from 127 +/- 2 to 165 +/- 6 mm Hg, P < .001), water intake, and urine volume and decreased body weight body weight. L-Arginine reduced ACTH-induced blood pressure rises (130 +/- 3 mm Hg, P < .001) but had no effect on blood pressure in sham-treated rats. D-Arginine did not affect blood pressure in sham-treated rats, and systolic pressure in D-arginine+ACTH-treated rats was similar to that of ACTH-treated rats. L-Arginine decreased serum corticosterone concentrations in sham-treated rats (424 +/- 42 versus 238 +/- 25 ng/mL, P < .01), but D-arginine had no effect. However, both drugs decreased serum corticosterone concentrations in ACTH-treated rats (1071 +/- 117 versus 739 +/- 95 and 695 +/- 72 ng/mL for L- and D-arginine, respectively; both P < .05). As L-arginine but not D-arginine prevented ACTH-induced increases in blood pressure in Sprague-Dawley rats and both L- and D-arginine reduced serum corticosterone concentrations in ACTH-treated rats, the effects of L-arginine in preventing ACTH-induced hypertension were not simply a consequence of decreased corticosterone secretion.

A community trial of ivermectin for onchocerciasis in Sierra Leone: compliance and parasitological profiles after three and a half years of intervention

We have studied the compliance patterns and the long-term effects of repeated ivermectin at various dosing intervals in a randomized controlled trial. The setting for the trial was six neighbouring communities hyperendemic for onchocerciasis in southern Sierra Leone. A total of 335 subjects attended a survey 18 months after the fifth treatment round. Of those randomized to ivermectin, over 85% had received at least three doses. There was no evidence that women of childbearing age were consistently under-treated, despite the criteria for exclusion from treatment. An intention-to-treat analysis showed that a 6-monthly ivermectin treatment regime satisfactorily suppressed microfilarial loads. Microfilarial repopulation was significantly slower over an 18-month period after multiple doses compared to a single dose. Further analysis of microfilarial repopulation suggests that there is a cumulative suppressive effect after at least the first three doses of ivermectin, and that an annual treatment interval is as effective for short-term microfilarial suppression as a 6-monthly interval.

Long-term ouabain administration does not alter blood pressure in conscious Sprague-Dawley rats

1. We tested the ability of ouabain to cause chronic hypertension by continuously infusing ouabain for 28 days (miniosmotic pump implantation; i.p.). The blood pressure and metabolic effects of sham (150 mmol/L NaCl; n = 12) or ouabain infusion (10 micrograms/kg per day; n = 14; 100 micrograms/kg per day; n = 14) were examined in conscious Sprague-Dawley rats. 2. Plasma ouabain concentrations measured after 28 days of ouabain infusion were as follows: sham, not detectable (n = 11); ouabain 10 micrograms/kg per day, 0.60 +/- 0.07 nmol/L (n = 14); and ouabain 100 micrograms/kg per day, 7.17 +/- 0.57 nmol/L (n = 14; P < 0.001). 3. Sham or ouabain infusion did not alter food intake, bodyweight, water intake or urine output in conscious rats. 4. Blood pressure was not altered by sham treatment. Ouabain at 10 micrograms/kg per day or 100 micrograms/kg per day did not produce consistent rises in blood pressure. Ouabain at 10 micrograms/kg per day increased blood pressure on treatment day 12 only (+6 mmHg; P < 0.05), while at 100 micrograms/kg per day blood pressure increased on treatment days 16 (+9 mmHg; P < 0.05) and day 18 (+8 mmHg; P < 0.05) only. There was no significant difference in blood pressure between sham and ouabain groups. 5. Renal blood flow was decreased in rats infused with ouabain at 10 micrograms/kg per day (2.0 +/- 0.3 mL/min per 100 g bodyweight; n = 5; P < 0.01) and 100 micrograms/kg per day (2.2 +/- 0.4 mL/min per 100 g bodyweight; n = 7; P < 0.05) compared with sham treatment (3.5 +/- 0.2 mL/min per 100 g bodyweight; n = 6). Renal vascular resistance was increased in rats treated with ouabain at 10 micrograms/kg per day (65.5 +/- 12.6 mmHg/mL per min per 100 g bodyweight; n = 5; P < 0.01) and 100 micrograms/kg per day (66.0 +/- 15.6 mmHg/mL per min per 100 g bodyweight; n = 7; P < 0.05) compared with sham treatment (32.6 +/- 2.5 mmHg/mL per min per 100 g bodyweight; n = 6). 6. High plasma concentrations of ouabain do not cause consistent increases in blood pressure in conscious Sprague-Dawley rats.