The depression of phagocytosis by exogenous cyclic nucleotides, prostaglandins, and theophylline.

The effects of agents that elevate intracellular cyclic adenosine 3',5'-monophosphate (cAMP) have been studied with respect to phagocytosis by guinea pig polymorphonuclear leukocytes. The investigation depends upon the use of a precise method for following ingestion. Theophylline, dibutyryl cAMP, and prostaglandins inhibited the phagocytosis of starch particles. The inhibitions caused by prostaglandins E(1), E(2), and F(2alpha) (PGE(1), PGE(2), and PGF(2alpha)) were synergistic with that due to theophylline. Inhibition by PGA(1) and PGA(2) was not. At equal concentrations the order of increasing inhibition of phagocytosis (assayed at 10 min) by the prostaglandins was PGE(1) < PGF(2alpha) < PGE(2) < PGA(1) = PGA(2). Our results are consistent with the hypothesis that increased intracellular levels of cAMP impair the phagocyte's ability to ingest particles. The mechanism of the inhibition has not been defined. The increment in oxidation of [1-(14)C]glucose to (14)CO(2) that normally accompanies phagocytosis was found to be depressed in the presence of PGE(1) or theophylline, together or individually as expected from the inhibition of phagocytosis. Paradoxically, oxygen consumption although depressed by theophylline or PGE(1) plus theophylline, was stimulated by PGE(1) alone.

Dissecting the structure of a partially folded protein. Circular dichroism and nuclear magnetic resonance studies of peptides from ubiquitin.

The nature and interaction of structural elements in a partially ordered form of ubiquitin, the A-state, which is populated at low pH in 40 to 60% aqueous methanol, have been investigated. Two synthetic peptides have been studied under the same conditions: U(1-21), corresponding to the N-terminal beta-hairpin in the native (N) and A-states of ubiquitin and U(1-35), which includes this hairpin plus an alpha-helix. Circular dichroism studies indicate that, although these peptides are largely unfolded in water, their structural content in 30 and 60% methanol is comparable with the corresponding native secondary structure. Sequence-specific assignments of the 1H n.m.r. spectra of U(1-35) in aqueous methanol and subsequent secondary structure determination confirm the conservation in detail of native-like secondary structure. Corresponding resonances in spectra of U(1-35), U(1-21) and the A-state itself were found to have closely similar chemical shifts, suggesting that the beta-hairpin exists independently in the partially folded protein, with little or no influence from the rest of the molecule. This is confirmed by the virtual absence in nuclear Overhauser enhancement spectroscopy and rotating frame nuclear Overhauser enhancement spectroscopy spectra of nuclear Overhauser enhancement effects between structural elements. c.d. and n.m.r. evidence suggests that structure in the C-terminal half of the molecule in the A-state is largely non-native. Thus, although methanol is necessary to assure its stability in the absence of wider native interactions, the structure of the beta-hairpin, including the register of its hydrogen bonding, appears to be determined entirely by its own sequence. This intrinsic structural preference in the first part of the ubiquitin sequence is much stronger than in the C-terminal half, a conclusion reflected in the results from a variety of secondary structure prediction algorithms.

Renal chloride channel, CLCN5, mutations in Dent's disease.

Dent's disease is an X-linked renal tubular disorder characterized by low-molecular-weight proteinuria, hypercalciuria, nephrocalcinosis, nephrolithiasis, and renal failure. Patients with Dent's disease may also suffer from rickets and other features of the renal Fanconi Syndrome. Patients may have mutations in the X-linked renal chloride channel gene, CLCN5, which encodes a 746-amino-acid protein with 12-13 transmembrane domains. We have investigated the 11 coding exons of CLCN5 for mutations in eight unrelated patients with Dent's disease. Leukocyte DNA was used for the polymerase chain reaction amplification of CLCN5 and the products analyzed for single-stranded conformational polymorphisms (SSCPs). Abnormal SSCPs were sequenced and revealed eight mutations. These consisted of three nonsense mutations (Arg34Stop, Arg648Stop, Arg704Stop), four deletions involving codons 40, 86, 157, and 241, and one acceptor splice consensus sequence mutation tgcag --> tgaag. The mutations were confirmed either by restriction endonuclease or sequence-specific oligonucleotide hybridization analysis. In addition, an analysis of 110 alleles from 74 unrelated normal individuals demonstrated that the DNA sequence changes were not common polymorphisms. All of the mutations predict truncated chloride channels that are likely to result in a functional loss. Thus, our findings expand the spectrum of CLCN5 mutations associated with Dent's disease and the results will help to elucidate further the functional domains of this novel chloride channel.

Long-term data storage in DNA.

This article discusses how DNA might be used to store data. It is argued that, at present, DNA would be best employed as a long-term repository (thousands or millions of years). How data-containing DNA might be packaged and how the data might be encrypted, with particular attention to the encryption of written information, is also discussed. Various encryption issues are touched on, such as how data-containing DNA might be differentiated from genetic material, error detection, data compression and reading frame location. Finally, this article broaches the difficulty of constructing very large pieces of DNA in the laboratory and highlights some complications that might arise when attempting to transmit DNA-encrypted data to recipients who are a long period of time in the future.

Retention of native-like structure in an acyclic counterpart of a beta-sheet antibiotic.

An acyclic derivative of the cyclic peptide antibiotic, ramoplanin, has been prepared. In aqueous solution, two-dimensional NMR spectroscopy indicates that the acyclic form adopts a threshold population of conformers in which at least part of the beta-sheet characteristic of the intact ramoplanin persists. Thus, despite losing the entropic benefit which the macrocycle must lend to beta-sheet formation, the polypeptide chain of the acyclic ramoplanin appears to display an innate tendency to adopt a native-like conformation.

Choice of drug treatment for elderly hypertensive patients.

It is generally agreed that moderate and severe hypertension in the elderly should be treated, but it is not clear which drug or drugs are most appropriate. Thiazide diuretics are inexpensive and effective, but they are associated with metabolic side effects that are becoming less acceptable as newer agents become available. Beta blockers are effective, but can be associated with central nervous system side effects and are often contraindicated by coexisting disease. Recently, attention has been focused on the newer agents, including calcium antagonists and angiotensin-converting enzyme inhibitors. The advantage of calcium antagonists is that they do not produce metabolic side effects. However, they are expensive and may cause vasodilatory side effects. The angiotensin-converting enzyme inhibitors are effective and relatively free of side effects and may be particularly useful for elderly hypertensive patients with congestive heart failure.

A double-blind evaluation of captopril in elderly hypertensives.

To establish the role of angiotensin converting enzyme inhibitors in the management of hypertension in the elderly, 16 patients were treated with captopril in a randomized double-blind placebo-controlled cross-over study. Clinic blood pressure, ambulatory blood pressure, renal function and mental performance, with emphasis on mood and psychological well-being, were assessed. Twelve patients, aged 73 (+/- 4.4) years, completed the study. The doses of captopril used were 50 mg (11 patients) and 25 mg (one patient) twice daily for 4 weeks. Mean (+/- s.e.m.) clinic sitting blood pressure during captopril therapy was significantly lower than during administration of placebo (172 +/- 4.5/83 +/- 25 versus 188 +/- 4.4/89 +/- 3.4 mmHg; P less than 0.001/P less than 0.05). Mean ambulatory blood pressure was also significantly lower on captopril treatment than during administration of placebo (166 +/- 5.3/87 +/- 1.6 versus 179 +/- 5.1/94 +/- 2.4 mmHg; P less than 0.02/P less than 0.02) and this effect was sustained over the dosing interval. Renal blood flow and mental performance were unaltered by treatment. Gastrointestinal discomfort occurred in two patients, one of whom was withdrawn and cough developed in one patient. We conclude that captopril is effective as monotherapy in lowering blood pressure in the elderly.

Discrepancy between clinic and ambulatory blood pressure measurement in the evaluation of two antihypertensive agents.

Discrepancies between clinic and ambulatory BP measurements may be important in the assessment of antihypertensive drug efficacy. Trimazosin (50-200 mg twice daily) and propranolol (40-160 mg twice daily) were compared in 22 hypertensive subjects in a randomised double-blind cross-over study. Daytime ambulatory BP was measured with a non-invasive portable recorder (Remler M2000). Clinic BP measurements were made with a random zero sphygmomanometer. While both drugs reduced clinic supine BP (trimazosin by 16/10 mmHg, P less than 0.01/P less than 0.001; propranolol by 25/14 mmHg, P less than 0.001/P less than 0.001), equivalent decreases on ambulatory measurement occurred with propranolol (28/11 mm/Hg, P less than 0.001/P less than 0.001) but not trimazosin (8/3 mmHg, P less than 0.05/NS). This difference in drug efficacy persisted throughout the 12-hour dosing interval. We conclude that clinic BP measurements alone cannot be relied upon to reflect accurately changes in BP induced by antihypertensive drugs. Moreover this study confirms the necessity for ambulatory BP measurement in the evaluation of antihypertensive drugs.

The antihypertensive efficacy of ketanserin in the elderly evaluated by ambulatory blood pressure measurement.

To assess the role of the serotonin antagonist ketanserin in the management of hypertension in the elderly, 12 patients with a mean age of 68 years (range 60-79 years) were treated with ketanserin in a randomised double-blind placebo-controlled cross-over trial. Clinic BP, ambulatory BP, renal function, and pharmacokinetics were assessed. The doses of ketanserin used were 40 mg (ten patients) and 20 mg (two patients) twice daily for 8 weeks. Mean clinic sitting BP was reduced from 169 +/- 5/98 +/- 2 on placebo to 155 +/- 5/88 +/- 3 mmHg (NS/P less than 0.05/P less than 0.05) and standing pressure from 168 +/- 6/100 +/- 3 to 157 +/- 5/91 +/- 3 mmHg (NS/P less than 0.01). Mean ambulatory systolic BP was unaffected by active treatment (167 +/- 7 vs 164 +/- 5) while diastolic pressure was lowered from 99 +/- 2 to 94 +/- 2 mmHg (P less than 0.05). This effect appeared to be mainly confined to the first two hours after drug administration. Renal blood flow was unaltered by treatment. The mean plasma half-life of ketanserin was 20.9 +/- 5.5 hours. Side effects were minimal. In conclusion, while ketanserin may be effective as assessed in the clinic, its efficacy on ambulatory monitoring is substantially less impressive.

The antihypertensive efficacy of verapamil in the elderly evaluated by ambulatory blood pressure measurement.

To assess the efficacy, tolerability and pharmacokinetics of verapamil in the elderly, ten patients with blood pressure greater than 160/90 mmHg were studied in a randomized double-blind placebo-controlled cross-over trial. Nine patients aged 75 (+/- 4.9) years completed the study. After titration, doses of verapamil varying from 40 to 120 mg (40 mg in four, 80 mg in one and 120 mg in four patients) twice daily for six weeks were taken. Mean (+/- SEM) clinic lying blood pressure was reduced on verapamil from 187 +/- 6.8/100 +/- 4.1 to 167 +/- 4.6/86 +/- 3.1 mmHg, [P less than 0.001). Mean ambulatory blood pressure was reduced from 174 +/- 1.4/95 +/- 1.0 to 169 +/- 1.3/90 +/- 0.8 mmHg, (P less than 0.01). Lying heart rate was significantly reduced but glomerular filtration rate, renal blood flow and mental function, were not altered by treatment. The mean plasma half-life of verapamil was 6.9 +/- 1.1 hours. Side effects were minimal. We conclude that verapamil is an effective blood pressure lowering agent in the elderly.

Ambulatory blood pressure measurement in the elderly.

A number of problems relating to clinic measurements of blood pressure may be particularly relevant to elderly patients with isolated systolic hypertension. First, there are large discrepancies in the blood pressure levels measured by these two techniques in the elderly population. Second, while blood pressure is universally accepted as one of the most important risk factors for the development of cardiovascular morbidity, its predictive value in the individual is relatively poor. Clinic and 24-h ambulatory recordings from 318 patients aged 17-80 years, diagnosed as having isolated systolic hypertension on clinic measurement, were compared with reference values determined from 815 healthy bank employees. In the isolated systolic hypertension group, mean systolic blood pressure by daytime ambulatory measurement was 27 mmHg lower than that recorded in the clinic, while diastolic pressure was similar (151 +/- 17/87 +/- 11 versus 178 +/- 28/84 +/- 9 mmHg). This discrepancy was greater in women than men, increased slightly but significantly with age (r = 0.12, P less than 0.05) and raised the crucial question as to which of the two measurements might best predict prognosis in this population. In a further study of the association between electrocardiographic (ECG) voltages and blood pressure measured in the clinic and by ambulatory monitoring in 216 patients with isolated systolic hypertension, the sum of SV1 + RV5 and the sum of SV1 + RV6 were significantly and positively related to systolic pressure both in the clinic and with daytime and night-time ambulatory measurement.(ABSTRACT TRUNCATED AT 250 WORDS)

The J-shaped curve in elderly hypertensives.

PURPOSE: To review the relationship between mortality and morbidity and achieved blood pressure, after drug treatment in elderly hypertensive patients. CONTENTS: Recent studies have suggested that a reduction in systolic blood pressure, with drug treatment, to levels below about 140 mmHg in elderly patients (greater than 60 years) may increase the risk of stroke. However, a J-shaped relationship between both mortality and morbidity and blood pressure has been reported in the untreated controls of the Hypertension in Elderly Patients in primary care (HEP) study. In the European Working Party on High Blood Pressure in the Elderly trial (EWPHE) there was a U-shaped relationship between total mortality and treated systolic pressure, but a similar U-shaped relationship was observed with diastolic pressure in patients on placebo. In addition, patients with the lowest pressure during treatment showed the greatest falls in body weight and haemoglobin concentrations, suggesting that the increased mortality seen with lower blood pressure levels may have been an expression of a deterioration in general health. Moreover, a U-shaped relationship between blood pressure and mortality has been observed in the very old (aged 80 + years). CONCLUSIONS: While it is premature to conclude, on the basis of present evidence, that reducing blood pressure to the lower part of the normal range is harmful in older patients, it appears prudent, nonetheless, not to lower blood pressure excessively with treatment in this age group.

Do subjects with stiff arteries have high blood pressure?

It has been argued that age-related increases in arterial stiffness could lead to spuriously high indirect blood pressure measurements, with consequent overdiagnosis of hypertension in older patients. To study the relationship between arterial stiffness and blood pressure, we identified patients with 'arterial stiffness', using Osler's manoeuvre, and compared their blood pressure levels with patients of a similar age. A total of 250 hospital inpatients were assessed independently by two doctors. In the 198 patients (79%) where both observers agreed on Osler's manoeuvre status, positive Osler's manoeuvre was uncommon under the age of 50 years but became more common thereafter, rising to 58% of patients aged over 75 years. However, blood pressure levels were similar in each age group, irrespective of Osler's manoeuvre status. We conclude that increased arterial stiffness as measured by Osler's manoeuvre is not necessarily associated with raised blood pressure levels in the elderly.