Cardioselective and nonselective beta-adrenoceptor blocking drugs in hypertension: a comparison of their effect on blood pressure during mental and physical activity.

The ability of cardioselective and nonselective beta-adrenoceptor blocking drugs, with and without partial agonist activity, to control increases in blood pressure associated with mental and physical activity was compared in 35 subjects with hypertension. Direct measurements of blood pressure and radioenzymatic determinations of plasma norepinephrine were obtained before, during and after four activities, and were repeated after random allocation to treatment with atenolol, metoprolol, pindolol or propranolol. Cardioselective and nonselective drugs modestly reduced the pressor response to reaction time testing, but not to mental arithmetic or isometric exercise. The increase in systolic blood pressure during bicycling was attenuated significantly by the cardioselective drugs atenolol (by 23 mm Hg, or 38%) and metoprolol (21 mm Hg, or 41%), but not by the nonselective agents pindolol (with partial agonist activity) (13 mm Hg, or 20%) and propranolol (10 mm Hg, or 17%) (p less than 0.02 cardioselective versus nonselective; p = NS pindolol versus propranolol). Only bicycle exercise increased plasma norepinephrine concentrations (by 80%). These results suggest that beta-adrenoceptor blocking drugs will not attenuate increases in blood pressure during mental or physical activities unless intense sympathoadrenal activation also occurs. Marked elevations in circulating epinephrine, with or without norepinephrine, and peripheral beta 2-blockade appear necessary for alpha-mediated vasoconstriction to predominate and for the contrasting effects of cardioselective and nonselective drugs to be appreciated.

Investigation of the mechanisms underlying the increased contraction of hypertrophied ventricular myocytes isolated from the spontaneously hypertensive rat.

OBJECTIVE: The aim was to investigate the cellular mechanisms responsible for the increased contraction of left ventricular myocytes isolated from the spontaneously hypertensive rat (SHR). METHODS: Single myocytes were isolated enzymatically from the left ventricles of SHR, Wistar-Kyoto (WKY), and Wistar rats. WKY and Wistar myocytes were used as normotensive controls. Cytoplasmic calcium was measured with Fura-2 and contraction was measured optically. Membrane potential was measured with microelectrodes and cells were voltage clamped to measure the amplitude of L-type calcium current (iCa). RESULTS: Under action potential conditions, SHR myocytes had a larger calcium transient and an increased sarcoplasmic reticular calcium content compared to normotensive myocytes. There was no detectable difference in the resting cytoplasmic calcium concentration between SHR and control myocytes. SHR myocytes also had a prolonged action potential compared to normotensive cells. However, when cells were voltage clamped and short pulses of 120 ms duration were applied (a similar duration of depolarisation to the action potential), the difference in the calcium transient or contraction between SHR and normotensive myocytes was abolished. SHR myocytes had an unchanged amplitude of ICa in comparison to control myocytes, and there was no detectable difference in the myofilament response to calcium between SHR and control myocytes. CONCLUSIONS: (1) Hypertrophied SHR myocytes stimulated with action potentials had an increased calcium transient compared to normotensive cells. The greater calcium transient in the SHR cells is likely to be a major factor responsible for their increased contraction. (2) SHR myocytes had a prolonged action potential in comparison to normotensive cells. (3) The amplitude of ICa and myofilament response to calcium were unchanged in SHR myocytes, suggesting that these factors do not play a role in the increased contraction of these cells. (4) Since the difference between SHR and control cells was abolished by voltage clamping the cells to prevent the difference of action potential, it is unlikely that an alteration of intrinsic mechanisms in SHR myocytes is responsible for their increased contraction. Rather, it suggests that the prolonged action potential of SHR myocytes plays a important role in causing their increased calcium transient and contraction. Our results indicate that the prolonged action potential in SHR cells results in an increased calcium content of the sarcoplasmic reticulum, which leads to a greater sarcoplasmic reticular calcium release upon stimulation and an increased contraction.

Haemodynamic changes during tilt after autonomic blockade in spontaneously hypertensive rats.

The haemodynamic shifts during head up and head down tilt were investigated in adult spontaneously hypertensive rats (SHR) and matched normotensive control rats (NCR) under nembutal anaesthesia and autonomic blockage. During head up tilt a greater fall in blood pressure and stroke volume was observed in SHR than in NCR, while the reverse was true when tilted in the opposite direction. This altered cardiac response to venous filling, also observed in patients with essential hypertension, is suggested to be caused by an altered Frank-Starling relationship of the hypertrophied heart in hypertensive individuals.

Wall stress induced arrhythmia is enhanced by low potassium and early left ventricular hypertrophy in the working rat heart.

OBJECTIVE: The aim was to investigate the effect of lowering external potassium on the sensitivity of the normal and hypertrophied rat heart to arrhythmias induced by increases in ventricular wall stress. METHODS: The isolated working heart model was used to compare hypertrophied hearts from the spontaneously hypertensive rat (SHR) with hearts from normotensive control rats (NCR) from the Wistar and Wistar-Kyoto strains. Young animals [131.5(SEM 0.64) days] were used to ensure uncomplicated left ventricular hypertrophy. Arrhythmias were induced by 20 s increases in ventricular wall stress. The ECG was recorded and the arrhythmic response of each heart was compared during perfusion with Tyrode solutions containing [K] 6, 4.8, 3.6, and 2.4 mM. RESULTS: Hypertrophied SHR hearts showed a significantly greater arrhythmic response than control hearts at all levels of afterload increase when perfused with [K] 3.6 and 2.4 mM (t test P < 0.05 and P < 0.01). Both the number and complexity of arrhythmias were increased in the SHR hearts; ventricular tachycardia occurred in 10/12 compared with 4/12 control hearts whereas ventricular fibrillation occurred in 5/12 hearts but in none of the control hearts. CONCLUSIONS: At higher levels of [K] the sensitivity of SHR and normal hearts to wall stress induced arrhythmias is similar. However, as [K] is lowered to 3.6 mM or below, hypertrophied hearts show a greatly enhanced response to increases in ventricular wall stress. They develop a larger number of ventricular ectopics and more complex ventricular arrhythmias when compared to normal hearts. This may be of relevance to arrhythmic sudden death in hypertensive patients in whom left ventricular hypertrophy, potassium depletion, and blood pressure lability is common. Excessive fluctuations in systolic pressure and therefore ventricular wall stress could provide a powerful arrhythmic stimulus in hypertensive patients with left ventricular hypertrophy, even before ischaemia, cardiac failure, or extensive extracellular fibrosis have developed.

Effect of streptomycin on wall-stress-induced arrhythmias in the working rat heart.

OBJECTIVE: To assess whether streptomycin, an inhibitor of mechano-sensitive cation channels, has an effect on arrhythmias-induced by an increase of ventricular wall stress in the rat heart. METHODS: The isolated working rat heart preparation was used. Arrhythmias were induced by increasing the afterload (i.e., aortic pressure) against which the left ventricle (LV) pumped for 20 s. This led to an increase of LV pressure, stretch of the LV and an increase in LV wall stress. The number of ventricular premature beats induced by each afterload step was compared in the absence and presence of streptomycin, a compound known to block mechano-sensitive cation channels in the heart. RESULTS: Perfusion with 200 microM streptomycin caused a significant reduction in wall-stress-induced arrhythmias. The effect of streptomycin on arrhythmias reached steady-state within 10 min of application. In the presence of streptomycin, arrhythmias elicited by a 40 mmHg afterload increase were reduced to 38% of control. Arrhythmias induced by an 80 mmHg afterload increase were reduced to 61% of control. Complex arrhythmias (ventricular tachycardia) induced by an afterload increase were also reduced in the presence of 200 microM streptomycin. There was no change in inotropic state with streptomycin, as assessed either by cardiac output or by maximum developed LV pressure. Streptomycin 50 microM (a typical therapeutic plasma concentration in patients) had no effect on wall-stress-induced arrhythmias. CONCLUSIONS: The results were inconsistent with streptomycin acting by modulating inositol phosphate production, or altering the level of intracellular calcium or inotropic state. The anti-arrhythmic effect of streptomycin appears more consistent with inhibition of mechano-sensitive cation channels, suggesting that these ion channels might be involved in causing wall-stress-induced arrhythmias.

Wall stress-induced arrhythmias in the working rat heart as left ventricular hypertrophy regresses during captopril treatment.

OBJECTIVES: (1) To determine whether regression of left ventricular hypertrophy (LVH) leads to a reduction in wall stress induced arrhythmia. (2) To determine the relationship between the time course of LVH regression and changes in arrhythmias in the spontaneously hypertensive rat heart. METHODS: 67 male spontaneously hypertensive rats (SHR) and 67 normotensive Wistar Kyoto rats (WKY) rats were studied at 100 days of age. 39 of each were treated with the ACE inhibitor captopril 2 mg/ml in drinking water, and the remaining 28 were controls. At 0, 2, 4, 8 and 16 weeks hearts were removed and perfused in the working heart mode. Control afterload was 80 mm Hg and perfusate K+ was 2.4 mM. Step increases in afterload (20, 40 and 80 mm Hg rises; 20 s duration; 2 min between each) were applied in random order to increase ventricular wall stress and induce arrhythmias. RESULTS: Total number of ventricular premature beats (VPBs) elicited by each afterload step were counted. The ratio of left ventricular weight to body weight in the SHR (an index of LVH) showed a rapid and marked decline with captopril treatment (2.65 +/- s.e.m. 0.07 mg/g after 2 weeks treatment compared to 3.38 +/- 0.08 before treatment; P < 0.01), indicating that captopril produced rapid regression of LVH. In contrast, the number of wall stress-induced arrhythmias in SHR did not show a significant decline over the 16 week treatment period. However, when the effect of regression of LVH on wall thickness was taken into account, and compensation was made for differences in wall stress applied, there did appear to be a slow reduction in arrhythmias in SHR. This decline in VPBs was significant after 16 weeks treatment for 40 and 80 mm Hg rises in afterload (P < 0.05). CONCLUSIONS: Treatment with captopril produced a rapid regression of LVH in the SHR. In contrast, arrhythmias declined more slowly over the 16 week period. There did not appear to be a direct relationship between the degree of regression of LVH and wall stress-induced arrhythmias in this model.

Involvement of the baroreceptor reflexes in the changes in blood pressure with sleep and mental arousal.

We have measured baroreflex sensitivity and blood pressure in 13 subjects during sleep and three stages of progressive mental arousal after waking. Baroreflex sensitivity was measured by correlating the increase in pulse interval with the increase in systolic pressure produced by an intravenous injection of 80 micrograms of phenylephrine. Blood pressure was measured directly from the brachial artery. During sleep, blood pressure fell and baroreflex sensitivity increased; with increasing mental arousal, blood pressure rose and baroreflex sensitivity decreased. These results suggest that baroreflex activity may be involved in the medium-term regulation of blood pressure during the day and night in addition to its recognized role in buffering acute changes in blood pressure.

Flutamide, testolactone, and reduced hydrocortisone dose maintain normal growth velocity and bone maturation despite elevated androgen levels in children with congenital adrenal hyperplasia.

Treatment outcome in congenital adrenal hyperplasia is often sub-optimal due to hyperandrogenism, treatment-induced hypercortisolism, or both. We previously reported better control of linear growth, weight gain, and bone maturation in a short term cross-over study of a new four-drug treatment regimen containing an antiandrogen (flutamide), an inhibitor of androgen to estrogen conversion (testolactone), reduced hydrocortisone dose, and fludrocortisone, compared to the effects of a control regimen of hydrocortisone and fludrocortisone. Twenty-eight children have completed 2 yr of follow-up in a subsequent long term randomized parallel study comparing these two treatment regimens. During 2 yr of therapy, compared to children receiving hydrocortisone, and fludrocortisone treatment, children receiving flutamide, testolactone, reduced hydrocortisone dose (average of 8.7 +/- 0.6 mg/m2 x day), and fludrocortisone had significantly (P < or = 0.05) higher plasma 17-hydroxyprogesterone, androstenedione, dehydroepiandrosterone, dehydroepiandrosterone sulfate, and testosterone levels. Despite elevated androgen levels, children receiving the new treatment regimen had normal linear growth rate (at 2 yr, 0.1 +/- 0.5 SD units), and bone maturation (at 2 yr, 0.7 +/- 0.3 yr bone age/yr chronological age). No significant adverse effects were observed after 2 yr. We conclude that the regimen of flutamide, testolactone, reduced hydrocortisone dose, and fludrocortisone provides effective control of congenital adrenal hyperplasia with reduced risk of glucocorticoid excess. A long term study of this new regimen is ongoing.

Increased final height in precocious puberty after long-term treatment with LHRH agonists: the National Institutes of Health experience.

We report 98 children who have reached final adult height in a long-term trial of LHRH agonist treatment. These children were 5.3 +/- 2.1 yr old at the start of treatment and were treated with either deslorelin (4 microg/kg.d sc) or histrelin (4-10 microg/kg.d) for an average of 6.1 +/- 2.5 yr. Final height averaged 159.8 +/- 7.6 cm in the 80 girls, which was significantly greater than pretreatment predicted height (149.3 +/- 9.6 cm) but still significantly less than midparental height (MPH) (163.7 +/- 5.6). Final height averaged 171.1 +/- 8.7 cm in the 18 boys, which was significantly greater than pretreatment predicted height (156.1 +/- 14.2 cm) but still significantly less than MPH (178.3 +/- 5.2 cm). However, the average adult height of the 54 children who had less than a 2-yr delay in the onset of treatment was not significantly different from their MPH, and 21 children exceeded MPH. Final height SD score correlated positively with duration of treatment (P < 0.01), midparental height (P < 0.001), predicted height at the start of treatment (P < 0.001), and growth velocity during the last year of treatment (P < 0.001) and correlated inversely with delay in the onset of treatment (P < 0.001), age at the start of treatment (P < 0.001), bone age at the start of treatment (P < 0.001), bone age at the end of treatment (P < 0.001), breast stage at the start of treatment (P = 0.02), and bone age minus chronological age at the start of treatment (P = 0.001). We conclude that LHRH agonist treatment improves the final height for children with rapidly progressing precocious puberty treated before the age of 8 yr for girls or 9 yr for boys. Less delay in the onset of treatment, longer duration of treatment, and lower chronological and bone age at the onset of treatment all lead to greater final height. All children with onset of pubertal symptoms before age 8 in girls and age 9 in boys should be evaluated for possible treatment. Treatment is appropriate in children with rapidly progressing puberty, accelerated bone maturation, and compromise of adult height prediction, regardless of bone age or chronological age at time of evaluation. However, once treatment is considered appropriate, it should be initiated quickly, because longer delays lead to shorter final height. In addition, the longer the treatment is continued, the greater is the final height outcome.

A preliminary study of flutamide, testolactone, and reduced hydrocortisone dose in the treatment of congenital adrenal hyperplasia.

Treatment outcome in congenital adrenal hyperplasia is often suboptimal due to hyperandrogenism, treatment-induced hypercortisolism, or both. As a new approach, we hypothesized that the effects of androgen could be blocked by an antiandrogen (flutamide) and an inhibitor androgen to estrogen conversion (testolactone), thus allowing the hydrocortisone dose to be reduced. We conducted a short term pilot study in 12 children with congenital adrenal hyperplasia in a randomised cross-over open design to determine whether flutamide, testolactone, reduced hydrocortisone dose, and fludrocortisone are more effective than hydrocortisone and fludrocortisone treatment in normalizing linear growth, weight gain, and bone maturation. Each regimen was administered for 6 months, with a 3-month washout period, consisting of hydrocortisone and fludrocortisone treatment, between regimens. Compared to hydrocortisone and fludrocortisone treatment, the regimen of flutamide, testolactone, reduced hydrocortisone dose (from 12.9 to 7.9 mg/m2 day), and fludrocortisone produced an increase in plasma 17-hydroxyprogesterone levels (P < 0.05) and a decline in urinary cortisol (P < 0.01), linear growth rate (-0.9 +/- 0.5 vs. 1.4 +/- 0.6 SD U; P = 0.003), weight velocity (-0.80 +/- 4.0 vs 0.6 +/- 0.4 SD U; P = 0.01), and bone maturation (0.6 +/- 0.6 vs. 1.4 +/- 0.9 yr bone age/yr chronological age; P = 0.02). Although no important adverse effects were observed, the known potential for flutamide-induced hepatotoxicity made frequent monitoring essential. We conclude that the regimen of flutamide, testolactone, reduced hydrocortisone does, and fludrocortisone improve the short term control of growth and bone maturation in children with congenital adrenal hyperplasia. Long term studies are required to determine whether this approach can improve these children's growth and development.

Boys with precocious puberty due to hypothalamic hamartoma: reproductive axis after discontinuation of gonadotropin-releasing hormone analog therapy.

Hypothalamic hamartoma is an important cause of precocious puberty in boys. Although the GnRH analogs are known to be effective therapy, there are few studies of the recovery of the pituitary-gonadal axis following long-term treatment. To this end, we studied 11 boys with HH after 8.8+/-3.2 yr (range, 4.0-12.6) of treatment with the GnRH agonist D-Trp6,Pro9,NEt-LHRH. The patients' levels of LH and FSH, testosterone, testis volume, and body mass index were compared with those of six normal boys in pubertal stage IV-V. We found that the patients' mean +/- SD peak GnRH-stimulated LH and FSH had returned to the normal range by 1 yr after stopping therapy. Whereas testosterone returned to normal levels by 1 yr, the patients' testis volume remained smaller than normal until 2 yr after therapy. Ultrasonography revealed diffuse, punctate, echogenic foci in the testicular parenchyma of two patients; these were first observed during GnRH agonist therapy and persisted unchanged after discontinuation of treatment. Neither of these two patients reported pain or testicular discomfort, no mass or irregularity was detected by manual examination in either patient at any time, and levels of beta-hCG and alpha1-fetoprotein were normal. By 4 yr after therapy, all patients had pubertal stage V pubic hair; their body mass index was not different from that of the normal boys at any time point. The dimensions of the patients' hamartomas did not change during or after therapy, and no patient reported new neurological symptoms or signs suggestive of an enlarging lesion at any time during or after discontinuation of treatment. Two families did report episodes of emotional lability and truancy as the patients reentered puberty after discontinuation of treatment.

Reproductive axis after discontinuation of gonadotropin-releasing hormone analog treatment of girls with precocious puberty: long term follow-up comparing girls with hypothalamic hamartoma to those with idiopathic precocious puberty.

Although the GnRH agonist analogs have become an established treatment for precocious puberty, there have been few long term studies of reproductive function and general health after discontinuation of therapy. To this end, we compared peak LH and FSH after 100 microg sc GnRH, estradiol, mean ovarian volume (MOV), age of onset and frequency of menses, body mass (BMI), and incidence of neurological and psychiatric problems in 2 groups of girls: those with precocious puberty due to hypothalamic hamartoma (HH; n 18) and those with idiopathic precocious puberty (IPP; n = 32) who had been treated with deslorelin (4-8 microg/kg x day, s.c.) or histrelin (10 microg/kg x day, s.c.) for 3.1-10.3 yr and were observed at 1, 2, 3, and 4-5 yr after discontinuation of treatment. The endocrine findings were also compared to those in 14 normal perimenarcheal girls. There were no differences between the HH and IPP groups in age or bone age at the start of treatment, at the end of treatment, or during GnRH analog therapy. We found that whereas the peak LH level was higher in HH than in IPP girls before (165.5 +/- 129 vs. 97.5 +/- 55.7; P < 0.02) and at the end (6.8 +/- 6.0 vs. 3.9 +/- 1.8 mIU/mL; P < 0.05) of therapy, this difference did not persist at any of the posttherapy time points. LH, FSH, and estradiol rose into the pubertal range by 1 yr posttherapy in both HH and IPP. However, the mean posttherapy peak LH levels in both HH and IPP groups tended to be lower than normal, whereas the peak FSH levels were not different from normal, so that the overall posttherapy LH/FSH ratio was decreased compared to that in the normal girls (HH, 2.7 +/- 0.3; IPP, 2.6 +/- 0.1; normal, 5.2 +/- 4.8; P < 0.05). The MOV was larger in HH than IPP at the end of treatment (3.7 +/- 3.5 vs. 2.0 +/- 1.2 mL; P < 0.05) and tended to increase in both groups over time to become larger than that in normal girls by 4-5 yr posttherapy (HH, 14.9 +/- 12.9; IPP, 7.6 +/- 2.2; normal, 5.4 +/- 2.5 mL; P < 0.05). Whereas the onset of spontaneous menses varied widely in both groups, once menses had started, the HH group had a higher incidence of oligomenorrhea. Pelvic ultrasonography revealed more than 10-mm hypoechoic regions in 4 HH patients, 15 IPP patients, and 3 normal girls, all of whom were reporting regular menses. Live births of normal infants were reported by 2 HH and 2 IPP patients, and elective terminations of pregnancy were reported by 1 HH and 2 IPP patients. BMI was greater than normal in HH and IPP both before treatment and at all posttherapy time points and tended to be higher in the HH patients. Marked obesity (BMI, +2 to +5.2 SD score) was observed in 5 HH and 6 IPP patients, 1 of whom had a BMI of +2.5 SD score and developed acanthosis nigricans, insulin resistance, and hyperglycemia. Seizure disorders developed during GnRH analog therapy in 5 HH and 1 IPP patient, and 2 additional HH girls developed severe depression and emotional lability posttherapy. Although the mean anterior-posterior dimension of the hamartoma was larger in the HH patients with seizure than in those who were seizure free (1.7 +/- 1.2 vs. 0.9 +/- 0.4 cm; P < 0.05), no change in hamartoma size was observed either during or after therapy, and no patient has reported the onset of a seizure disorder posttherapy. Other than a tendency toward a larger MOV, a higher incidence of oligomenorrhea, obesity, and frequency of neurological disorders, recovery of the reproductive axis after GnRH analog therapy was not markedly different in HH compared to IPP. Continued follow-up of these patients may determine whether the decreased LH responses and increased BMI in both groups compared to those in normal girls remain clinically significant problems.

Factors influencing blood pressure and heart rate variability in hypertensive humans.

We examined the influence of baroreceptor reflex sensitivity (the increase in pulse interval in response to a phenylephrine-induced increase in blood pressure), age, blood pressure, and beta-adrenergic receptor blockade on the variability of blood pressure and heart rate in essential hypertension. Fifty-six subjects were studied before treatment; intra-arterial blood pressure was recorded outside the hospital for 24 hours. Variability was defined (from all beats occurring while subjects were awake) as the standard deviation about the average waking value for mean arterial pressure (MAP) or pulse interval. The correlation (r) between baroreceptor reflex sensitivity and blood pressure variability was -0.47 (p less than 0.0002). Baroreceptor reflex sensitivity was the only independent determinant of blood pressure variability on multiple regression analysis. Thirty subjects were restudied after 5 months of beta-adrenergic receptor blockade. Ambulatory blood pressure was lower during treatment, whereas pulse interval, its variability, and baroreceptor reflex sensitivity were higher. Blood pressure variability was unchanged. The variability of MAP was inversely correlated with baroreceptor reflex sensitivity before (r = -0.42, p less than 0.02) and during (r = -0.45, p less than 0.02) treatment, but it was unrelated to the average ambulatory MAP or to the variability of pulse interval either before or during beta-blockade. Sixteen subjects whose average waking ambulatory blood pressure was 140/90 mm Hg or less were not treated. This group of borderline hypertensive subjects had less variable MAP than did the remaining 40 subjects (12.4 +/- 2.3 [SD] vs 14.5 +/- 2.5 mm Hg; p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Hypocomplementemic urticarial vasculitis syndrome. Clinical and serologic findings in 18 patients.

We identify and describe clinical findings in hypocomplementemic urticarial vasculitis syndrome (HUVS), an uncommon to rare illness related to systemic lupus erythematosus (SLE). A patient with recurrent, idiopathic urticaria-like lesions was diagnosed as having HUVS if a lesional biopsy showed leukocytoclastic vasculitis, the serum C1q was markedly decreased, and antibody to C1q was detected in the patient's serum. The clinical characteristics, serologic findings, and outcome of patients who met these criteria were determined from prospective and retrospective data, including hospital and office records, patient interviews, previously banked serum samples, and freshly drawn sera. Eighteen patients with HUVS were identified, and high incidences of angioedema, ocular inflammation, glomerulonephritis, and obstructive pulmonary disease were found. Renal and lung biopsies showed mesangial or membranoproliferative glomerulonephritis and severe pulmonary emphysema without vasculitis. Pulmonary function was measured in 17 patients, 11 of whom had dyspnea. All dyspneic patients had moderate to severe airflow obstruction, which progressed in all 11 and subsequently improved in only 1. Six of these 11 patients died of respiratory failure, 1 underwent lung transplantation, and 3 of the remaining 4 have moderately severe to life-threatening respiratory insufficiency. Treatment did not appear to alter the progression of obstructive lung disease. In contrast, renal insufficiency improved with treatment in 2 of 2 patients. Angioedema, ocular inflammation, obstructive lung disease, and glomerulonephritis appear to be common in HUVS, and lung disease causes substantial morbidity and mortality. The pathogenesis of HUVS may involve humoral autoimmunity, although it is not clear how autoimmunity would participate in development of obstructive lung disease. Cigarette smoking appears to be a risk factor for fatal lung disease in HUVS. All patients with HUVS should be made aware of this possibility and should be advised, encouraged, and helped to avoid tobacco smoke.

A substrate amplification system for enzyme-linked immunoassays. II. Demonstration of its applicability for measuring anti-DNA antibodies.

We have recently described a substrate amplification system, based on the method of Self, which increases the sensitivity of alkaline phosphatase (AP)-dependent enzyme-linked immunosorbent assays (ELISA) by a factor of 30-50. This increase is achieved by having AP, the primary enzyme, produce an activator for a secondary enzyme-substrate system, within which marked amplification occurs. We have now demonstrated that this amplification method can be applied to the measurement of human antibodies to DNA. The sensitivity is greater by a factor of 10 than the conventional method, which uses p-nitrophenyl phosphate (p-NPP) as substrate. On replicate assays the method is reproducible, with a coefficient of variation of less than 0.1. This great increase in sensitivity should be of value in conserving specimens of serum and in screening monoclonal antibodies.

A substrate amplification system for enzyme-linked immunoassays. Demonstration of its general applicability to ELISA systems for detecting antibodies and immune complexes.

Self recently described a substrate system for alkaline phosphatase (AP)-dependent ELISAs which markedly increased sensitivity, compared to using p-nitrophenyl phosphate. This increase is achieved by having AP, the primary enzyme, produce an activator for a secondary enzyme-substrate system, within which marked amplification occurs. We adapted this technique to study antibodies to casein, bovine serum albumin, ovalbumin, and cardiolipin in the sera of patients with systemic lupus erythematosus (SLE) and normal individuals. The new substrate system yielded titres 30-50-fold higher than those with p-nitrophenyl phosphate (Sigma 104, p-NPP). In addition, when used in a solid-phase C1q binding assay we were able to use a 1 : 100,000 dilution of AP-conjugated anti-human IgG with the amplified substrate, compared to the 1 : 1000 dilution needed with p-NPP. This system is extremely valuable because of its flexibility. It can either be very sparing of limited samples, or if the added sensitivity is not needed, 100-fold less AP conjugate may be used. Thus rare or expensive conjugates can be significantly conserved.

Beta-adrenoreceptor blockade in hypertension.

There is good evidence from many sources that beta-adrenoreceptor blockade is an effective form of therapy in mild, moderate and severe hypertension either alone or in combination with other antihypertensive agents. Although a number os such beta blocking compounds are now available, they appear to have a hypotensive effect of approximately equal magnitude. This hypotensive effect is obtained in both the supine and standing positions thus avoiding postural hypotension. The maximum hypotensive effect may take some time to become apparent. Despite considerable work the mode of action remains uncertain, reduction in cardiac output, resetting of baroreceptors, reduction in plasma renin and a central nervous system effect have been suggested but remain unproved. There is evidence to suggest that these compounds can control, to some degree, the surges in blood pressure resulting from either mental or physical stress. A low incidence of serious side effects has been reported by many workers. Only the long-term use of these compounds in comparison with other antihypertensive agents will determine their place in the management of hypertension.

Therapeutic trial of cryofiltration in patients with rheumatoid arthritis.

Cryofiltration, a new technique for on-line plasma separation and its treatment by cold filtration, enables the selective removal of immune complexes and eliminates the need for replacement proteins. Fifteen patients with rheumatoid arthritis were treated for nine to 10 consecutive sessions over a three- to five-week period. Circulating immune complexes decreased by an average of 78 percent and rheumatoid factor by 32 percent. This was accompanied by significant clinical improvement in morning stiffness, articular index, 50-foot walking time, grip strength, and target joint circumference. Cryofiltration might thus be beneficial for a subgroup of rheumatoid arthritis patients in whom conventional therapy has failed.

Ventricular arrhythmia in untreated newly presenting hypertensive patients compared with matched normal population.

There is evidence to suggest that hypertensive patients are at increased risk of sudden death. However, to date this evidence is restricted to treated hypertensives and it is not clear whether this risk is due to the hypertension itself, its treatment, or its long-term consequences. This study has investigated, by 24-h ambulatory electrocardiography, a total of 58 newly diagnosed hypertensive patients who have never previously been treated and compared the first 50 of them with 50 matched control subjects. The results show that there is an increased prevalence of ventricular arrhythmia in hypertensive patients, compared with normal controls, and that this arrhythmia is present from the outset and thus not dependent on treatment or the development of long-term complications. Multivariate analysis showed that age (positive correlation) and potassium (negative correlation) made the most important independent contributions to the prevalence of arrhythmia in these patients, but even so only accounted for about 33% of the observed arrhythmia. This suggests that the precursors of arrhythmia in hypertension are multifactorial. One other factor appeared to make an important contribution to ventricular arrhythmia in these patients. In contrast to recent evidence from the study of treated hypertensives, the prevalence of ventricular arrhythmia was significantly lower in patients exhibiting electrocardiographic evidence of left ventricular hypertrophy. However, left ventricular hypertrophy did also appear to sensitize the myocardium to the arrhythmogenic effect of low serum potassium levels. These findings may help to explain some of the previous confusion surrounding treatment, hypertension and ventricular arrhythmia.

The paradoxical role of left ventricular hypertrophy in wall stress-related arrhythmia.

OBJECTIVE: To investigate the interrelationship between arrhythmias provoked by acute pressure changes, and the presence of left ventricular hypertrophy and electrolyte imbalances. DESIGN: An isolated working rat heart model was used in a prospective comparison of the effects of acute pressure changes in hypertensive and normotensive hearts during perfusion with perfusate containing differing electrolyte compositions. SETTING: An experimental laboratory study. STUDY MATERIALS: Forty-four rat hearts (20 hypertensive, 24 normotensive). INTERVENTIONS: Hearts were subjected to sudden pressure changes of varying sizes during perfusion with two different electrolyte solutions and the arrhythmias provoked were recorded. MAIN OUTCOME MEASURES: The size of the pressure change necessary to provoke arrhythmias, and the amount and severity of arrhythmias provoked by equivalent-sized pressure changes. RESULTS: During perfusion with normal electrolyte concentrations, no hypertrophied hearts developed arrhythmia compared with more than half of the normal hearts during equivalent-sized pressure changes, and a much larger pressure increase was necessary to produce any arrhythmia in the hypertrophied hearts. During perfusion with cation-depleted perfusate, arrhythmias significantly increased in both groups of hearts, but the pattern was reversed; more than half of the hypertrophied hearts compared with none of the normal hearts developed ventricular tachycardia during equivalent-sized pressure increases, whilst the minimum pressure change necessary to provoke arrhythmia became significantly smaller in the hypertrophied hearts compared with the normal hearts. CONCLUSIONS: Left ventricular hypertrophy plays a paradoxical role in the development of arrhythmias in this model. It appears to protect the heart from developing arrhythmias in response to sudden pressure changes when electrolyte concentrations are normal. However, it also seems to lead to a marked increase in the sensitivity of the myocardium to pressure changes during perfusion with low levels of potassium and magnesium. Under these conditions, potentially fatal arrhythmias can be readily provoked by relatively small pressure changes. These results may be of importance for the management of hypertension and may provide insight into some of the mechanisms underlying sudden death in hypertension. The findings may also be of relevance to other cardiac diseases associated with ventricular hypertrophy or abnormal wall stress.