Beyond genomics.

The sequencing of the human genome has already had an enormous impact on medicine, particularly with single-gene changes that predispose to a serious disease such as cystic fibrosis or the overexpression of Her2 in about one-third of breast cancers. Genetic technology has led to some very important therapeutic innovations, including the use of imatinib mesylate (Gleevec) in BCR-ABL chronic myeloid leukemia and of trastuzumab (Herceptin) in Her2-positive breast cancer, but the much anticipated explosion of new effective treatments has been more modest than expected.

Cigarette smoking: profiles of thromboxane- and prostacyclin-derived products in human urine.

Thromboxane (TX) B2, 2,3-dinor-TXB2, 11-dehydro-TXB2, 6-oxoprostaglandin (PG)F1 alpha and 2,3-dinor-6-oxo-PGF1 alpha were measured in 24 h urine samples obtained from 30 apparently healthy chronic cigarette smokers and 37 closely matched non-smoking control subjects. Samples were analysed using a newly developed assay based on immunoaffinity chromatography and capillary column gas chromatography/electron capture negative ion chemical ionisation mass spectrometry. There were significant and comparable increases in the excretion rates of both 2,3-dinor-TXB2 and 11-dehydro-TXB2 in the smoking compared with the non-smoking group (2P less than 0.001). Excretion rates of 2,3-dinor-TXB2 were 418 +/- 35 and 265 +/- 26 pg/mg creatinine in the two groups, respectively. 11-Dehydro-TXB2 excretion rates were 440 +/- 54 and 221 +/- 18 pg/mg creatinine, respectively (mean +/- S.E.). There were significant (2P less than 0.05) positive correlations between average reported cigarette consumption and excretion of both thromboxane metabolites. There were small but significant (2P less than 0.02) increases in the excretion rates of both 6-oxo-PGF1 alpha and 2,3-dinor-6-oxo-PGF1 alpha in the smoking compared with the non-smoking group. There was no significant difference in the rates of excretion of TXB2 in the two groups. The effects of acute cigarette smoke exposure (five cigarettes in 2 h) was also studied in four normally non-smoking healthy volunteers. There was no significant change in the excretion rate of any of the eicosanoids measured during control and smoking periods (at least 2 weeks apart), indicating that increased TXA2 biosynthesis in chronic smokers is unlikely to be a consequence of acute platelet activation.

Generation of hydroxyeicosatetraenoic acids by human inflammatory cells: analysis by thermospray liquid chromatography-mass spectrometry.

Arachidonic acid was converted to a series of hydroxyeicosatetraenoic acids (HETEs) by mixed human inflammatory cells following stimulation with the calcium ionophore A23187. HETEs were purified by a simple one-step extraction procedure followed by HPLC. The HPLC was coupled to a Finnigan quadrupole mass spectrometer using the now commercially available thermospray liquid chromatography-mass spectrometry interface. The HPLC eluant was monitored 'on line' by the mass spectrometer. Soft ionisation occurs, generating intense molecular ion species in the negative ion mode (M - H-:m/z 319) for each of the isomeric HETEs. The (M + H+ - H2O) ion at m/z 303 is the major species in the positive ion spectra of HETEs. Mass spectra were obtained on-line post-HPLC for HETEs formed by the human cells, and the HPLC-MS profile compared with that obtained from standards; species corresponding to the 11-, 9- and 5-HETEs were observed.

The identity of IgE receptors (Fc epsilon RII) that mediate cellular activation of human macrophages: evidence against a role for CD23.

There is now compelling evidence that macrophages bind IgE, and are involved in several IgE-dependent responses. The CD23 antigen mediates a mitogenic response in "primed" B-lymphocytes, although its expression is not confined to B cells, and CD23 is inducably expressed in many cells including macrophages. CD23 is also known to bind IgE, a property that leads to inhibition of the mitogenic response in B cells. In the present review, the possibility that CD23 mediates IgE-dependent responses in macrophages has been re-examined, and it is proposed that the functional receptor for IgE on macrophages may be quite separate from the CD23 antigen.

Influence of hospitalization and placebo therapy on blood pressure and sympathetic function in essential hypertension.

The decline in blood pressure (BP) in essential hypertensives following hospitalization may result from: 1) regression toward the mean; 2) reduction of anxiety as patients habituate to a new environment; 3) the placebo effect of medication; and 4) an independent effect of hospitalization itself. A randomized crossover study of 12 essential hypertensives demonstrated a fall in supine blood pressure from 165.0/97.9 +/- 2.3/1.1 mm Hg to 154.3/89.6 +/- 2.7/1.1 mm Hg (p less than 0.005) due to hospitalization. A similar reduction in BP from 164.9/99.5 +/- 8.4/4.1 mm Hg to 151.9/93.4 +/- 4.5/1.9 mm Hg (p less than 0.005) resulted from regression toward the mean and habituation during the study period. Urinary catecholamines fell from 68.7 +/- 5.0 to 55.1 +/- 4.3 micrograms/g creatinine/24 hours (p less than 0.05) due to hospitalization and from 56.1 +/- 5.4 to 49.7 +/- 4.3 micrograms/g creatinine/24 hours (p less than 0.05) with time. Although placebo therapy tended to reduce BP, it failed to do so significantly. When expressed as a percentage of the individual's overall mean, urinary catecholamine excretion fell from 110.5% +/- 3.7% to 89.5% +/- 3.7% (p less than 0.001) during hospitalization and from 105.8% +/- 3.9% to 94.2% +/- 3.9% (p less than 0.05) during the outpatient period. Blood pressure and sympathetic activity rapidly returned to prehospitalization values on discharge. These factors may confound the analysis of drug effects on BP and sympathetic activity in essential hypertensives following admission to hospital.

Efficacy of nifedipine as a step 3 antihypertensive drug.

The efficacy of nifedipine (N) as a "step 3" antihypertensive drug was assessed in 15 patients who remained hypertensive in spite of atenolol 100 mg and bendrofluazide 5 mg daily. Nifedipine was added in doses of 10, 20, and 30 mg three times daily in a placebo-controlled double-blind trial. Supine mean blood pressure was reduced by 11.9% +/- 6.2% by N 10 mg three times daily, by 13.9% +/- 7.6% by N 20 mg three times daily and by 20.3% +/- 6.2% by N 30 mg three times daily. Plasma potassium was reduced from 3.9 +/- 0.5 mEq/liter on placebo to 3.6 +/- 0.5 mEq/liter on N 10 mg three times daily, 3.6 +/- 0.4 mEq/liter on N 20 mg three times daily (p less than 0.05), and 3.5 +/- 0.5 mEq/liter on N 30 mg three times daily (p less than 0.05). Heart rate, body weight, renal function, and plasma glucose were not altered. Nifedipine is thus a useful third-line hypotensive agent that should be used in combination with a potassium-sparing diuretic.

Glucose tolerance during antihypertensive therapy in patients with diabetes mellitus.

Many antihypertensive drugs have adverse effects on glycemic control when they are used in diabetic patients. This was noted for thiazide diuretics in 1960, and the mechanism of the effects remains uncertain. Indirect evidence suggests that changes in the serum potassium are at least contributory, although the principal mechanism of thiazide-induced hyperglycemia is probably a reduction in the insulin response to glucose. Beta blockers also adversely affect blood sugar control but only by a small margin. The main cause for concern with beta blockers, however, is their effect during hypoglycemia in which nonselective agents delay blood sugar recovery. In diabetic patients, the institution of antihypertensive therapy should be followed by a reassessment to note any changes in sugar, potassium, and lipids, or side effects.

Fifteen-year survival of patients beginning treatment with methyldopa between 1962 and 1966.

The 15-year survival of a group of 205 patients who started treatment in the period 1962 through 1966 and who received methyldopa for two-thirds or more of the time has been investigated. At entry these patients had severe hypertension with an average pretreatment pressure of 216/126 mm Hg. Twenty-one percent had retinal hemorrhages, cotton-wool spots, or papilledema. Blood pressure showed a large fall in the first year, followed by a small, progressive, further fall up to the sixth year. After 5 years of treatment the blood pressure averaged 144/90 mm Hg in men and 151/91 mm Hg in women. The average daily dose of methyldopa was approximately 1500 mg and changed little over the 15-year period. Survival was analyzed by life tables. Approximately 81% of men and women aged 30 to 49.9 years at entry were still alive 10 years later. In the age group 60 to 69.9 years, 53.8% of men and 63.2% of women were still alive 10 years later. Seventy-nine of the patients died during the follow-up period, 89% from cardiovascular or renal disease. Ischemic heart disease (40%) was the major cause of death, followed by stroke (19%). No patients died from drug toxicity.

Drug regulation in the United Kingdom.

The British system under the Medicines Act by which new drug applications are evaluated is described in a step-by-step manner from submission of application to the issuance of a clinical trial certificate by the licensing authority. At the end of a period by clinical trials the submission is brought back for a product license. Once a drug is marketed it falls within the purview of the adverse reaction monitoring group of the Committee on Safety of Medicines (CSM). A recent innovation is "monitored release", by which, for a period of time after marketing, case reports are submitted by the pharmaceutical company to the CSM. The advantages of the British system are: (1) the final licensing decisions being made by the academic members of the Committee means that they are insulated from commercial and political pressures, and are additionally reached without undue delay; (2) academic members are not permitted to be retained as consultants to the industry on a long-term basis; (3) evaluation solely on British studies is not obligatory--foreign studies are also acceptable. Weakness in the system are: (1) recruitment of people experienced in pharmacology and therapeutics is difficult; (2) there is an inordinate work load on the academic members of the Main Committee and Subcommittees. Importance of an effective monitoring in the postmarketing stage is emphasized, because the long-term judgement must necessarily be based on wide experience in the field. The multiplication of the same of similar drugs is deplored, and innovative efforts in the quest for new drugs, especially for rare diseases, are to be encouraged.

Regulation of norepinephrine release by peripheral alpha 2-receptor stimulation.

Although extensive evidence obtained in animals and in vitro supports the existence of an alpha-receptor-mediated inhibitory regulation of norepinephrine release, the importance of such a system in man is not established. Norepinephrine release was physiologically stimulated by change of posture and dynamic exercise in subjects while they were infused with phenylephrine, a predominant alpha 1-receptor agonist, alpha-methylnorepinephrine, a predominant alpha 2-agonist, and saline. Agonist infusions were administered both at rates that induced a slight elevation in supine systolic pressure and at nonpressor rates. Agonist concentrations that induced much the same pressor responses (alpha 1) were assumed on the basis of in vitro experiments to differ substantially in their affinity for alpha 2-receptors. The hemodynamic response and the increase of plasma norepinephrine induced by changes in posture and exercise were of the same order during infusions of alpha-methylnorepinephrine, phenylephrine, and saline. Similar results from the "nonpressor" as from "pressor" agonist infusions suggested that baroreflex-induced reduction in sympathetic neuronal activity had not confounded the results. Correction of plasma concentrations for individual values of norepinephrine clearance provided an index of norepinephrine release into the circulation that was not changed by phenylephrine or alpha-methylnorepinephrine. These results raise the question of the importance of peripheral alpha 2-receptors in the regulation of norepinephrine release in man.

Norepinephrine release in essential hypertension.

Supine basal plasma norepinephrine was higher in a group of newly diagnosed patients with mild essential hypertension than in age- and sex-matched "laboratory-naive" volunteers. Sympathetic activation by exercise and change of posture increased plasma norepinephrine in both groups, with a tendency toward higher values in the hypertensive patients, but norepinephrine clearance was slower and half-life longer in these patients. Thus the estimate of neuronal norepinephrine release obtained by correction of plasma norepinephrine for individual values of clearance was in the same range in both groups. Plasma norepinephrine was lower in younger "laboratory-adapted" subjects than in the "laboratory-naive" normotensive subjects, but clearance was in the same range in both. Thus, variations in kinetics may contribute to differences in plasma norepinephrine between patients with essential hypertension and matched controls. In contrast, the lower plasma concentration of norepinephrine in "laboratory-adapted" than in "laboratory-naive" controls appears to reflect a lower level of sympathetic activity in the former.

Clinical and cardiovascular effects of alpha methyldopa in combination with decarboxylase inhibitors.

The peripheral decarboxylase inhibitor carbidopa, given (100 mg/day) for 6 wk in a double-blind trial, lowered supine diastolic pressure of 10 patients with essential hypertension treated with alpha methyldopa by a small (6 mm Hg) but significant (p less than 0.05) amount. Large doses of benserazide (1.5 gm) did not modify the hypotensive effect of 1.0 gm of alpha methyldopa in untreated hypertension but significantly reduced the central nervous side effects of sedation and dry mouth. These studies indicate that extensive peripheral decarboxylation is not necessary for alpha methyldopa to lower blood pressure and would be compatible with the central nervous site of hypotensive action of this drug.

Antihypertensive action of bendroflumethiazide: increased prostacyclin production?

A within-patient randomized, double-blind, crossover study was performed to investigate mechanisms of action of bendroflumethiazide in mild essential hypertension. Significant reductions in lying, standing, and postexercise blood pressure were seen after both 3 days and 10 wk treatment with bendroflumethiazide 10 mg daily. Plasma levels of 6-oxo-PGF1 alpha, the chemical hydrolysis product of prostacyclin, were increased by both 3 days and 10 wk therapy with bendroflumethiazide. This raises the possibility that thiazides may reduce peripheral resistance by increasing prostacyclin biosynthesis.

Atenolol in essential hypertension.

The effect of atenolol, a beta adrenoceptor autogonist, on arterial pressure in patients with benign essential hypertension has been investigated. Eighteen patients were started on atenolol, 75 mg/day; the dose was increased at 2-wk intervals to a maximum of 900 mg if tolerated. When the maximum effective dose was determined, each patient was randomly allocated into a double-blind crossover study comparing atenolol and placebo treatments. The mean supine and erect arterial pressures of the 16 patients completing the run-in period were markedly reduced by atenolol therapy. The pretreatment mean (+/-SEM) supine and erect arterial pressures of the 16 patients completing the run-in period (187 +/-4.7/114 +/-2.6 and 182 +/-4.5/115 +/-3.0 mm Hg, respectively) were reduced (150 +/-5.3/97 +/-2.9 and 151 +/-5.9/100 +/-2.7 mm Hg) with atenolol therapy (p less than 0.01). In the crossover study, the mean (+/-SEM) supine arterial pressure after 8 wk of atenolol therapy in 14 patients (144 +/-5.2/89 +/-1.7 mm Hg) was lower (p less than 0.01) than at the end of placebo therapy (163 +/-4.4/105 +/-2.8 mm Hg). Similar reductions in pressure were recorded in the erect position and after exercise. No severe side effects were observed.

Assessment of MK-467, a peripheral alpha 2-adrenergic receptor antagonist, with intravenous clonidine.

The activity of MK-467, a new peripherally acting alpha 2-antagonist, was assessed in volunteers by a randomized, double-blind, crossover design. One hour after administration of either 15 mg or 30 mg MK-467 or placebo, 200 micrograms clonidine was given intravenously and observations were made for a further 8 hours. Clonidine reduced plasma norepinephrine levels to 79% +/- 7% of that of control 1 hour after infusion, an effect that was antagonized by low-dose MK-467 (p less than 0.05). Mean systolic blood pressure increased by 4 mm Hg in the first hour after the 30 mg dose of MK-467 (p less than 0.01), although there was no significant difference between the 3 study days in the maximal clonidine-induced decrease in systolic pressure, diastolic pressure, or heart rate. Clonidine induced a peak increase in mean blood glucose of 13%, which was antagonized by both doses of MK-467 (p less than 0.05). Plasma insulin was suppressed by clonidine from 72 +/- 14 to 47 +/- 7 IU.L-1, an effect antagonised by both doses of MK-467 (p less than 0.05 in each case). MK-467 had no effect on clonidine-induced increased drowsiness, xerostomia, or increase in growth hormone secretion, which is consistent with it being a peripherally acting specific alpha 2-antagonist. The small effect of MK-467 on clonidine-induced changes in plasma glucose and insulin suggests that peripheral alpha 2-adrenergic receptors play only a minor role in normal glucose homeostasis.

Oral absorption and concentration-effect relationship of tyramine with and without cimoxatone, a type-A specific inhibitor of monoamine oxidase.

The mechanism of increased sensitivity to oral tyramine in patients taking monoamine oxidase inhibitors was investigated by measurement of plasma norepinephrine and tyramine with a reversible, monoamine oxidase form A selective inhibitor, cimoxatone. In the first open study, the pressor activity of 80 mg oral tyramine after cimoxatone was of the order of that of 800 mg without the drug. In a second double-blind study, the equivalent tyramine dose was between 400 and 800 mg. Absorption of unmetabolized tyramine increased in the presence of cimoxatone. Peak plasma concentration of tyramine after an 80-mg dose was approximately three times that of placebo when given after cimoxatone. The plasma tyramine concentration required to induce a similar pressor effect averaged 130.5 ng ml-1 without pretreatment and 17.4 ng ml-1 after cimoxatone in the open study. Another plasma concentration, 16.4 ng ml-1, elicited a lower pressor effect in the double-blind study. The increased sensitivity to oral tyramine has two components: decreased presystemic clearance in the gut wall and increased sensitivity to circulating tyramine. The tyramine dose required to induce a pressor effect after cimoxatone is relatively higher than after irreversible inhibitors such as phenelzine. This may reflect the dose of cimoxatone used, the activity of monoamine oxidase form B (MAO-B) in the gut and liver or displacement of the predominantly reversible and predominantly competitive inhibitor, cimoxatone, from the enzyme by a high local tyramine concentration.

Blood pressure and plasma norepinephrine concentrations after endogenous norepinephrine release by tyramine.

To determine whether small changes in sympathetic activity would cause detectable changes in plasma norepinephrine (NE) levels, and whether the effects of endogenously released and exogenous NE differ, we injected tyramine infusions and l-norepinephrine (l-NE), into six healthy subjects, and the changes in blood pressure (BP) and plasma NE were related. The mean increase in systolic BP was approximately 17 mm Hg with both infusions; diastolic BP increased with l-NE but did not rise significantly with tyramine. Heart rate fell more with l-NE than with tyramine infusions. The maximum increase in plasma NE levels was more than 500% during l-NE infusions but less than 200% with tyramine. There was no correlation between plasma NE and absolute levels of systolic BP when individual data were plotted for tyramine infusions, whereas mean group changes in systolic BP correlated strongly with mean group plasma NE, both during tyramine and l-NE infusions. The slope of the relationship was much steeper for tyramine than for l-NE. We conclude that the use of plasma NE to measure small differences in sympathetic activity among individuals is limited by interindividual variability, whereas changes in sympathetic activity within groups are more likely to be detected.

Nifedipine and alpha adrenoceptor antagonism.

The effects of nifedipine and placebo on the pressor responses to methoxamine, alpha-methylnorepinephrine, and angiotensin II were compared in normal subjects. Nifedipine shifted the pressor dose-response curves of all three agonists to the right. The dose ratios of the three agonists were of the same order. Thus in contrast to the findings in animals, nifedipine is not a selective alpha 2-adrenergic antagonist in man, although it may lower blood pressure partly by antagonism of norepinephrine and angiotensin II.

Absence of opiate and histamine H2 receptor-mediated effects of clonidine.

The possibility that clonidine might exert some of its effects via opiate or histamine H2 receptors has been suggested from observations in animals and man. We undertook a double-blind, randomized study in six normal subjects, comparing the effects of 0.2 mg intravenous clonidine after pretreatment with 300 mg cimetidine, 0.8 mg naloxone, and saline. There was no attenuation of the hypotension, bradycardia, sedation, inhibition of salivary flow, or reduction in plasma catecholamines after cimetidine and naloxone, but the fall in plasma catecholamines ater clonidine correlated with blood pressure, sedation, and salivary flow, suggesting a central adrenergic mechanism for these effects. It is not known whether cimetidine can cross the blood-brain barrier after short-term dosing. We conclude that in normotensive subjects the short-term effects of intravenous clonidine are probably not mediated by an action at peripheral histamine H2 or central opiate receptors.

Sedative and cardiovascular effects of clonidine and nitrazepam.

Five healthy male subjects, aged 26 to 35 yr, received single oral doses of clonidine 0.3 mg, nitrazepam 20 mg, or placebo double-blind with an interval of at least 1 wk between each treatment. Clonodine induced a maximal fall in systo9lic blood pressure from 104.2 +/- 1.6 to 84.7 +/- 1.4 mm Hg (mean +/- SEM) after 3.5 hr and nitrazepam from 102.9 +/- 1.9 to 90.3 +/- 2.6 mm Hg after 1.0 hr while after placebo blood pressure rose steadily from 102.5 +/- 2.9 to 109.6 +/- 3.5 mm Hg at the end of the 8-hr study. Total sleep time increased from 90.3 +/- 2.5. min after placebo to 256.2 +/0 21.0 min after clonidine (p < 0.001) and 281.0 +/- 40.3 min after nitrazepam (p < 0.001). Stage I sleep increased from 49.7 +/- 11.2 to 76.9 +/- 10.2 min after clonidine and to 76.3 +/- 25.2 min after nitrazepam (p < 0.0), while the greatest increase was observed in stage II: 230.7 +/- 25.6 min after clonidine and 236.6 +/- 35.4 min after nitrazepam compared with only 48.5 +/- 15.8 min after placebo (p < 0.001). Plasma norepinephrine did not change after placebo but fell after nitrazepam from 0.28 +/- 0.04 to 0.14 +/- 0.02 ng/ml after 3 hr (p < 0.05) and after clonidine from 0.23 +/- 0.07 to 0.07 +/- 0.02 ng/ml after 2 hr (p < 0.01). Clonidine and nitrazepam both induced similar hypnotic and hypotensive effects with some evidence that this might be due to a reduction in sympathetic tone.