Second- and third-generation beta-blocking drugs in chronic heart failure

The left-ventricular (LV) functional, hemodynamic, and antiadrenergic effects of metoprolol, bucindolol, and carvedilol have been compared in three concurrent placebo-controlled clinical trials in patients with symptomatic idiopathic dilated cardiomyopathy. All three drugs were well tolerated, all produced at least moderate degrees of beta-blockade as assessed by reduction in exercise heart rate, and all increased the left-ventricular ejection fraction. Compared with the beta 1-selective, second-generation compound metoprolol, the third-generation compounds bucindolol and carvedilol lowered indices of adrenergic activity and tended to improve LV function to a greater extent. In patients with chronic heart failure there may be important therapeutic response differences between second- and third-generation beta-blocking agents.

Body mass index, waist circumference, waist-hip ratio, and glucose intolerance in Chinese and Europid adults in Newcastle, UK

OBJECTIVE

To compare the prevalence of glucose intolerance (impaired glucose tolerance and diabetes), and its relationship to body mass index (BMI) and waist-hip ratio in Chinese and Europid adults.

DESIGN

This was a cross sectional study.

SETTING

Newcastle upon Tyne.

SUBJECTS

These comprised Chinese and Europid men and women, aged 25-64 years, and resident in Newcastle upon Tyne, UK.

MAIN OUTCOME MEASURES

Two hour post load plasma glucose concentration, BMI, waist circumference, and waist-hip ratio.

METHODS

Population based samples of Chinese and European adults were recruited. Each subject had a standard WHO oral glucose tolerance test.

RESULTS

Complete data were available for 375 Chinese and 610 Europid subjects. The age adjusted prevalences of glucose intolerance in Chinese and Europid men were 13.0% (p = 0.04). Mean BMIs were lower in Chinese men (23.8 v 26.1) and women (23.5 v 26.1) than in the Europids (p values < 0.001), as were waist circumferences (men, 83.3 cm v 90.8, p < 0.001; women, 77.3 cm v 79.2, p < 0.05). Mean waist-hip ratios were lower in Chinese men (0.90 v 0.91, p = 0.02) but higher in Chinese women (0.84 v 0.78, p < 0.001) compared with Europids. In both Chinese and Europid adults, higher BMI, waist circumference, and waist-hip ratio were associated with glucose intolerance.

CONCLUSIONS

The prevalence of glucose intolerance in Chinese men and women, despite lower BMIs, is similar to or higher than that in local Europid men and women and intermediate between levels found in China and those in Mauritius. It is suggested that an increase in mean BMI to the levels in the Europid population will be associated with a substantial increase in glucose intolerance in Chinese people.

Effects of age on cardiovascular responses to adrenaline in man

AIMS

Whereas the effects of ageing on beta-receptor mediated responses have been extensively studied in vitro and in vivo using the beta-adrenoceptor agonist isoprenaline, little is known regarding ageing induced changes in responses to endogenous catecholamines. In the present study, we assessed age-related changes in cardiac responses to the endogenous beta-adrenoceptor agonist adrenaline and the influence of age-related changes in arterial baroreflex function on these responses.

METHODS

Adrenaline alone was infused in 14 young subjects, age 30 +/- 2 years (eight males, six females), and 18 older subjects (six males, 12 females), age 60 +/- 2 years, and together with ganglionic blockade (trimetaphan) in seven young and 11 older subjects. Adrenaline was infused at 3-4 incremental rates, each rate for 8 min. Cardiac function was assessed by echocardiography.

RESULTS

Adrenaline alone, at infusion rates 20-160 ng kg-1 min-1 caused similar increases in heart rate in the two groups. In contrast, adrenaline caused larger increases in stroke volume, ejection fraction, cardiac index and systolic blood pressure and larger decreases in end-systolic wall stress and diastolic blood pressure in the young compared with older subjects. Older females exhibited the smallest increases in stroke volume index and ejection fraction. With concomitant ganglionic blockade, all above cardiovascular responses to adrenaline were similar in the young and older group. Plasma adrenaline increased similarly in the two groups.

CONCLUSIONS

We conclude that ganglionic blockade does not unmask an age-related decrease in cardiovascular responses to adrenaline (in contrast to isoprenaline). A concomitant ageing induced decrease in neuronal uptake (which applies to adrenaline, but not isoprenaline) may explain such a differential effect.

Clinically used antimicrobial drugs against experimental pneumocystosis, singly and in combination: analysis of drug interactions and efficacies

We analyzed single drugs and combinations of drugs used clinically in the treatment of opportunistic infections and other conditions for their activities against Pneumocystis carinii pneumonia in immunosuppressed rats. When they were used alone, atovaquone, rifabutin, and dapsone were more active than clarithromycin or trimethoprim. Drug combinations were evaluated for synergistic activity by an analysis of variance model for two-way factorial experiments and a response surface model. Atovaquone combined with trimethoprim trimethoprim and some combinations of dapsone and clarithromycin was synergistic; however, the activities of combinations of atovaquone and rifabutin, atovaquone and clarithromycin, and atovaquone and dapsone were simply additive. Lovastatin, which inhibits 3-hydroxy-methylglutaryl coenzyme A reductase, was inactive whether it was used alone or in combination with other agents. None of the synergistic drug combinations was as effective as trimethoprim-sulfamethoxazole. We conclude that the rat model can be used to test combinations of anti-P. carinii agents for synergistic activity by well-established statistical techniques. While some combinations of clinically used antimicrobial drugs have enhanced anti-P. carinii activity, further studies are needed before clinical trials can be contemplated.

Immunodeficient and immunosuppressed mice as models to test anti-Pneumocystis carinii drugs

Congenitally immunodeficient and immunosuppressed normal mice with naturally acquired Pneumocystis carinii infection were compared as models for testing anti-P. carinii drugs. Among the immunodeficient mice, mice with severe combined immunodeficiency disease (scid), which lack B and T cells, had higher levels of P. carinii pneumonia than did microMT mice, which lack K cells. Normal mice administered dexamethasone in the drinking water had more extensive pneumocystosis than mice administered parenteral methylprednisolone or hybridoma cells making a monoclonal antibody to CD4 cells. The standard anti-P. carinii drugs trimethoprim (TMP)-sulfamethoxazole (SMX), pentamidine, and atovaquone, which work well in rats and humans, worked well in the mice. Clindamycin and primaquine were effective in the scid and microMT mice but not in the immunosuppressed normal mice. High doses of epiroprim, an analog of TMP, appeared to enhance the activities of low doses of SMX and dapsone, while high doses of TMP did not; however, further studies are needed before definitive conclusions about the actions of these drugs can be drawn. Taken together, the data obtained in this study support the growing body of literature suggesting that the mouse is a valid alternative to the rat as a model for testing anti-P. carinii drugs. Additional differences involving the activities of individual drugs in these models will probably emerge as more experience is gained.

Parental evaluation of a tour of the neonatal intensive care unit during a high-risk pregnancy

OBJECTIVE

To describe parents' reaction to a prenatal tour of the neonatal intensive care unit (NICU) during a high-risk pregnancy and identify advice they have for other parents and health care professionals who participate in a such a tour.

DESIGN

Naturalistic inquiry, a qualitative approach.

SETTING

Semistructured interviews were conducted in the hospital or parents' home.

PARTICIPANTS

Thirteen expectant parents who had toured a NICU during a high-risk pregnancy.

MAIN OUTCOME MEASURES

Three categories of information were described by the parents: (a) a description of the tour; (b) benefits of the tour; and (c) an evaluation of the way that the tour was arranged and conducted, including advice to health care professionals and other parents.

RESULTS

All parents recommended that parents diagnosed with a high-risk pregnancy be offered a prenatal tour of the NICU. The tour benefited parents and (a) decreased fears, (b) inspired hope for the infant's prognosis, (c) provided reassurance about the care in the NICU, and (d) prepared parents for their infant's hospitalization in the NICU.

CONCLUSIONS

Parents experiencing a high-risk pregnancy benefit from a tour of the NICU. The tour familiarized parents with the NICU and the type of care that their newborn would require. However, during the tour, more attention should be given to the parental role in the NICU.

Effects of chromium on lymphocyte subsets and immunoglobulins from normal population and exposed workers

Blood lymphocyte subsets and serum immunoglobulins were studied in 15 men (mean age: 35 years), not exposed to toxic agents, and in 15 healthy men, exposed to dust containing several compounds (including lead chromate), working in a factory producing plastic materials. Worker blood lead and urine chromium (Cr) levels were significantly higher than controls, while serum Cr concentration was unchanged. In the worker blood, CD4+ helper-inducer (mainly CD4+-CD45RO- "virgin"), CD5--CD19+ B, CD3--CD25+ activated B and CD3--HLA-DR+ activated B and natural killer (NK) lymphocytes were significantly reduced (about 30-50 %). The investigated workers were exposed to hexavalent Cr, as lead chromate, whereas normal population (control group) was mainly exposed to trivalent Cr. In the control group, urinary Cr showed a significant positive correlation with CD16+-56+ NK, CD5+-CD19+ B and HLA-DR+ activated T, B and NK lymphocytes and a negative correlation with serum IgA immunoglobulins; moreover, serum Cr was significantly correlated with all blood lymphocytes and HLA-DR+, CD3--HLA--DR+ and CD3--CD25+ lymphocyte subsets. These data suggest that trivalent Cr may be involved in mechanisms regulating the immune response in humans.

Effect of pentoxifylline on renal toxicity of cyclosporine: results of a clinical trial after heart transplantation

BACKGROUND

Pentoxifylline was suggested to prevent the renal release of endothelin caused by cyclosporine.

METHODS

We studied the renal-sparing effect of pentoxifylline in 44 patients who underwent heart transplantation between 1991 and 1994 and were randomized to a group treated with pentoxifylline (400 mg three times daily) or to a control group. All patients were treated according to the same immunosuppression protocol, including induction with perioperative rabbit anti-thymocyte antibody and maintenance with azathioprine, cyclosporine, and prednisone. Five patients withdrew voluntarily because of lack of compliance, and five patients died during the first month of the study.

RESULTS

There was no difference between the two groups in regard to age, sex, initial cardiopathy, the number of acute rejections, and the number of infection episodes. Urinary clearance of creatinine averaged 1.1 +/- 0.1 ml/sec, 1.3 +/- 0.1 ml/sec, and 1.3 +/- 0.1 ml/sec in the control patients (n = 16) and 1.2 +/- 0.1 ml/sec, 1.4 +/- 0.1 ml/sec, and 1.3 ml/sec in patients treated with pentoxifylline (n = 18) at initiation, 12 months, and 24 months of the study (p > 0.05), respectively. At these three times, the serum creatinine levels averaged 106 +/- 4 mmol/L, 119 +/- 4 mmol/L, and 126 +/- 5 mmol/L in the control group and 94 +/- 4 mmol/L, 114 +/- 4 mmol/L, and 127 +/- 5 mmol/L in patients treated with pentoxifylline, respectively (p > 0.05). Trough levels of cyclosporine throughout the study period averaged 212 +/- 8 mmol/L and 206 +/- 8 mmol/L in the control and treated groups, respectively (p > 0.05). Endothelin blood levels averaged 0.4 +/- 0.2 pg/ml for nine control patients and 0.4 +/- 0.1 pg/ml for a group of 10 patients treated with pentoxifylline (p > 0.05).

CONCLUSIONS

Pentoxifylline in association with cyclosporine did not result in a significant improvement in renal function during the first 2 years after heart transplantation.

Comparative hemodynamic, left ventricular functional, and antiadrenergic effects of chronic treatment with metoprolol versus carvedilol in the failing heart

BACKGROUND

The basic pharmacology of the third-generation beta-blocking agent carvedilol differs considerably from second-generation compounds such as metoprolol. Moreover, carvedilol may produce different, ie, more favorable, clinical effects in chronic heart failure. For these reasons, we compared the effects of carvedilol and metoprolol on adrenergic activity, receptor expression, degree of clinical beta-blockade, hemodynamics, and left ventricular function in patients with mild or moderate chronic heart failure.

METHODS AND RESULTS

The effects of carvedilol versus metoprolol were compared in two concurrent placebo-controlled trials with carvedilol or metoprolol that had common substudies focused on adrenergic, hemodynamic, and left ventricular functional measurements. All subjects in the substudies had chronic heart failure resulting from idiopathic dilated cardiomyopathy. Carvedilol at 50 to 100 mg/d produced reductions in exercise heart rate that were similar to metoprolol at 125 to 150 mg/d, indicating comparable degrees of beta-blockade. Compared with metoprolol, carvedilol was associated with greater improvement in New York Heart Association functional class. Although there were no significant differences in hemodynamic effects between the carvedilol and metoprolol active-treatment groups, carvedilol tended to produce relatively greater improvements in left ventricular ejection fraction, stroke volume, and stroke work compared with changes in the respective placebo groups. Carvedilol selectively lowered coronary sinus norepinephrine levels, an index of cardiac adrenergic activity, whereas metoprolol did not lower coronary sinus norepinephrine and actually increased central venous norepinephrine levels. Finally, metoprolol was associated with an increase in cardiac beta-receptor density, whereas carvedilol did not change cardiac beta-receptor expression.

CONCLUSIONS

The third-generation beta-blocking agent carvedilol has substantially different effects on left ventricular function, hemodynamics, adrenergic activity, and beta-receptor expression than dose the second-generation compound metoprolol. Some or all of these differences may explain the apparent differences in clinical results between the two compounds.

U.S. experience with the AddVent VDD(R) pacing system. AddVent Phase I Investigators

The AddVent pacemaker generator and model 1328C AV single-pass lead is a new pacemaker system capable of VDD or VDDR modes. The purpose of this study was to present the initial experience with AddVent in the United States and Canada. Between May 10, 1995 and May 3, 1996, 53 devices were implanted in 52 patients and followed for a mean of 217 (+/- 39) days. At the predischarge, 1-, 3-, and 6-month follow-up evaluations, atrial sensing thresholds and ventricular sensing and capture thresholds were measured in the supine, sitting, and standing positions to evaluate stability of atrial sensing with respect to body posture at rest. At the 1-month follow-up, a treadmill exercise test was performed to evaluate atrial sensing during exercise and to evaluate two new features of the AddVent called "sensor-mediated rate smoothing" and "preferential P wave sensing." Atrial sensing thresholds were not significantly different (P > 0.05) among body postures for any follow-up period or among follow-up periods for each posture. At rest, the percentage of appropriately tracked P waves observed was > 99% at each follow-up period. During treadmill exercise, the percentage of appropriately tracked P waves was > 98.7%. Appropriate preferential P wave sensing and sensor-mediated rate smoothing (VDDR mode) was observed. The AddVent pacing system provides safe and effective pacing therapy. Several features of VDDR pacing offer advantages over standard VDD pacing.

Changes in R-R variability before and after endurance training measured by power spectral analysis and by the effect of isometric muscle contraction

The long-term conditioning effects of physical training on cardiorespiratory interaction in 11 young healthy males were studied. Significant increases in maximum oxygen uptake (VO2max) (P < 0.05) and decreases in heart rate (P < 0.05) were achieved in all subjects following a 6-week training programme consisting of cycling for 25 min each day at a work level that increased heart rate to 85% of maximum. Heart rate variability, measured as the differences between the maximum and minimum R-R interval in a respiratory cycle, increased in nine of the subjects and decreased in two. The respiratory-cycle-related high-frequency peak in the power spectral plot of R-R variability also showed significant increases in the same nine subjects and decreases in two. The latter result was similar after normalisation of the data for changes in heart rate by calculating the common coefficient of variance [symbol: see text], where HF is the high-frequency component of the power spectral plots, using a further measure of vagal tone it was shown that, for all subjects, the R-R interval change in response to isometric contractions of the arm flexors in one respiratory cycle were significantly greater after training. These data suggest that cardiac vagal tone is increased by aerobic training for all subjects and that this is accompanied by a respiratory sinus arrhythmia (RSA) in most, but may be associated with a decrease in RSA in subjects with a very low (< 50 beats.min-1 heart rate.

Interactions of recombinant human pulmonary surfactant protein D and SP-D multimers with influenza A

To further study the structure and function of surfactant protein D (SP-D), recombinant human SP-D (rhSP-D) was isolated from the culture medium of Chinese hamster ovary (CHO)-K1 cells stably transfected with a full-length hSP-D cDNA. Although a significant fraction of the secreted rhSP-D was recovered as dodecamers similar to recombinant rat SP-D (rrSP-D), a major fraction accumulated as multimers of dodecamers indistinguishable from human proteinosis SP-D. As previously shown for the rat protein, rhSP-D agglutinated specific strains of influenza A virus (IAV), inhibited viral hemagglutinin activity, and protected neutrophils (PMN) from deactivation by IAV. However, the potency of rhSP-D multimers was severalfold greater than for purified dodecamers, comparable to natural, proteinosis hSP-D. Although rhSP-D multimers were also more potent than the serum collectins in mediating viral aggregation and protection of PMN, they were less potent than conglutinin in inhibiting infectivity in vitro. These studies establish that the propensity of hSP-D to form multimers of dodecamers is determined by its primary structure and demonstrate carbohydrate recognition domain valency-dependent interactions of SP-D with IAV.

Expression of insulin-like growth factor II (IGF-II), IGF binding protein-2 and myogenin during differentiation of myogenic satellite cells derived from the turkey

Myogenic satellite cells are essential for the development of postnatal skeletal muscle. The proliferation and differentiation of these cells are, in part, regulated by the insulin-like growth factors (IGFs), and it has been shown that the IGF binding proteins (IGFBPs) are capable of modulating the actions of IGFs. We have examined the endogenous expression of IGF-II, IGFBP-2 and the myogenic regulatory factor, myogenin, during differentiation of clonally derived turkey muscle satellite cells. Cells were harvested at approximately 80% of confluent density. Additional cultures were rinsed, fed differentiation medium and harvested when approximately 20%, 60% and 80% differentiated (fused). Northern blot analyses were performed using total cellular RNA and labeled rat cDNAs specific for IGF-II, IGFBP-2 and myogenin. A single IGF-II mRNA transcript of approximately 4.0 kb was observed. The relative mRNA abundance was highest in proliferating cultures and decreased with the onset of differentiation, to approximately 60% of initial levels where it remained throughout differentiation. Use of the IGFBP-2 cDNA probe indicated a single mRNA transcript of approximately 2.0 kb. The level of expression of IGFBP-2 mRNA was highest in proliferating cells and decreased to 25%, 16% and 11% of initial levels as differentiation progressed. A single 1.8 kb mRNA transcript was detected with the myogenin probe. Expression of myogenin was undetectable in proliferating cultures and increased significantly as differentiation progressed. Serum-free medium was conditioned for 24 h (CM) at each time point and collected from similar cultures. An IGFBP species of M(r) approximately 30,000 was detected in CM by probing western blots with [125I] IGF-I (ligand blot analysis). The intensity of this band decreased with differentiation to 35%, 24% and 18% of the level for proliferating cultures. Western blots were also probed with an antibody raised against the M(r)-34,000 bovine IGFBP-2. This antibody specifically bound to the M(r)-30,000 IGFBP, and the level of antibody binding decreased as differentiation progressed. It therefore appears that IGF-II, IGFBP-2 and myogenin are expressed in a differentiation-dependent manner by turkey myogenic satellite cells and may thus be involved in the process of differentiation of avian muscle cells.