Suppression of savanna ants alters invertebrate composition and influences key ecosystem processes.

In almost every ecosystem, ants (Hymenoptera: Formicidae) are the dominant terrestrial invertebrate group. Their functional value was highlighted by Wilson (1987) who famously declared that invertebrates are the "little things that run the world." However, while it is generally accepted that ants fulfil important functions, few studies have tested these assumptions and demonstrated what happens in their absence. We report on a novel large-scale field experiment in undisturbed savanna habitat where we examined how ants influence the abundance of other invertebrate taxa in the system, and affect the key processes of decomposition and herbivory. Our experiment demonstrated that ants suppressed the abundance and activity of beetles, millipedes, and termites, and also influenced decomposition rates and levels of herbivory. Our study is the first to show that top-down control of termites by ants can have important ecosystem consequences. Further studies are needed to elucidate the effects ant communities have on other aspects of the ecosystem (e.g., soils, nutrient cycling, the microbial community) and how their relative importance for ecosystem function varies among ecosystem types (e.g., savanna vs. forest).

Low affinity heparin is an antithrombotic agent.

We have investigated the antithrombotic activities and haemorrhagic side effects of a low affinity heparin (LAH). In the rabbit thrombosis model using activated human serum as the thrombogenic challenge, the effect of LAH on 10' and 20' stasis was studied. At 10' stasis, 150 micrograms/kg of LAH reduced thrombus formation by 67% and total prevention was achieved at 500 micrograms/kg. At 20' stasis, 150 micrograms/kg was totally ineffective, 500 micrograms/kg was partially effective and 1000 micrograms/kg was required to achieve complete prevention of thrombosis. Mean peak circulatory level following infusion of 500 micrograms/kg of LAH was found to be 1.6 micrograms/ml by heparin cofactor II based assay and 0.13 iu/ml by anti-factor Xa assay. Thrombin generation tests of the same post injection samples showed an 80% reduction in thrombin production when compared with pre-injection samples. At 2.5 mg/kg, the mean bleeding time ratio (challenge:control) measured in the rabbit ear template model was 1.25 (cf saline control 0.88). Compared with results from previous studies on unfractionated heparin and dermatan sulphate, LAH is approximately 6 times less effective than UFH but 5 times more potent than dermatan sulphate. Since the mean bleeding time for UFH at 2.5 mg/kg was previously found to increase nearly two fold over the control value, LAH may present a lesser haemorrhagic risk than UFH. These data suggest that LAH is more effective in directly preventing venous thrombosis than dermatan sulphate. Although LAH is not as effective as UFH on a weight basis in the impairment of thrombogenesis, it may carry significantly lower bleeding risk.

Combined therapy with verapamil and propranolol in chronic stable angina.

The comparative efficacy of verapamil (360 mg daily) and propranolol (240 mg daily) was evaluated with computerized treadmill exercise in 22 patients with chronic stable angina in a placebo-controlled double-blind crossover study with 4 weeks on each active phase. Fourteen of these patients still had angina despite active drug therapy and they were further treated with a combination of verapamil (360 mg) and propranolol (120 mg) for 4 weeks. The mean exercise time for these patients taking placebo was 4.8 +/- 0.22 minutes (mean +/- standard error of the mean) and this increased to 6.8 +/- 0.64 minutes with propranolol and 8.0 +/- 0.5 minutes with verapamil. A further increase to 10.1 +/- 0.88 minutes was observed with the combination of both drugs and seven patients became symptom-free. S-T segment criteria improved with both drugs, and combination therapy produced a further reduction in peak S-T depression. Electrocardiographic ambulatory monitoring showed no evidence of conduction defects and mean hourly heart rates were similar to those seen with propranolol alone. Left ventricular function indexes were not significantly different from those obtained with propranolol. Combination therapy with verapamil and propranolol appears to be efficacious in the treatment of selected patients with severe chronic stable angina. The patients need to be carefully monitored for adverse effects.

Long-term antianginal action of verapamil assessed with quantitated serial treadmill stress testing.

The long-term efficacy of verapamil in a dose of 360 mg daily in patients with chronic stable angina pectoris was assessed by quantitated serial treadmill exercise tests. Twenty-eight patients were investigated with a placebo-controlled, double-blind, crossover protocol of 2 weeks each and afterward all patients were put on long-term therapy. Exercise tests were performed at the end of the placebo period and after 2, 4, 8, 16, 24 and 52 weeks of verapamil therapy. All 28 experienced angina during treadmill tests on placebo and the mean (+/- standard error of the mean) exercise time was 6.6 +/- 0.5 minutes. This increased to 9.2 +/- 0.8 minutes at 2 weeks and 50 11.2 +/- 0.8 minutes at 4 weeks. Fifteen and 20 of the 28 patients became angina-free during treadmill exercise at 2 and 4 weeks, respectively. The consumption of nitroglycerin showed a similar improvement. The improvement was maintained at 1 year of follow-up. The on-line computer-analyzed S-T segment changes showed a statistically significant improvement at all follow-up periods. Withdrawal of verapamil produced a return to pretreatment levels. The adverse effects noted were constipation in seven patients and reversible P-R interval prolongation in two. No heart failure occurred in any patient. These findings suggest that verapamil possesses a powerful and sustained antianginal action and, in a dose of 360 mg daily, merits a place as a primary therapeutic agent in the management of chronic stable angina.

Calcium channel blockade as primary therapy for stable angina pectoris. A double-blind placebo-controlled comparison of verapamil and propranolol.

The effectiveness and safety of the beta-adrenergic blocking agent propranolol and the calcium channel antagonist verapamil were compared in 22 patients with chronic stable angina pectoris using a double-blind randomized placebo-controlled crossover protocol. The double-blind phase was preceded by a 2 week single-blind placebo period, followed by randomization to either 4 weeks' therapy with verapamil, 360 mg/day, or propranolol, 240 mg/day, followed by crossover to the other drug. Both verapamil and propranolol increased exercise tolerance (5.5 +/- 0.4 minutes with placebo, 7.8 +/- 0.5 minutes with propranolol [p less than 0.001], and 9.1 +/- 0.5 minutes with verapamil [p less than 0.001]), but the increase with verapamil was significantly greater (p less than 0.01). Both drugs prolonged the exercise duration to 1 mm S-T depression (3.3 +/- 0.4 minutes with placebo, 5.7 +/- 0.5 minutes with propranolol [p less than 0.001] and 5.5 +/- 0.6 minutes with verapamil [p less than 0.001]); the degree of improvement was similar with both active drugs. Both drugs decreased the resting heart rate (76 +/- 3 beats/min with placebo, 56 +/- 2 beats/min with propranolol [p less than 0.001], and 71 +/- 3 beats/min with verapamil [p less than 0.01]), but the heart rate decreased more with propranolol than with verapamil (p less than 0.001). Neither drug produced significant adverse reactions. This study, along with 8 similar double-blind placebo-controlled randomized investigations which have compared verapamil with propranolol, indicate that verapamil is as effective and safe as propranolol in relieving symptoms and improving exercise tolerance in patients with chronic stable angina pectoris and may be considered a first-line therapeutic agent in patients with ischemic heart disease.

Rationale for the choice of calcium antagonists in chronic stable angina. An objective double-blind placebo-controlled comparison of nifedipine and verapamil.

The effectiveness and safety of verapamil, nifedipine, and placebo in patients with chronic stable angina pectoris were evaluated and compared in two double-blind randomized crossover trials. In the first study, nifedipine (10 mg 3 times daily) was compared with placebo in 24 patients with chronic effort-related angina pectoris; no significant differences in exercise performance were observed with nifedipine compared with placebo. In the second study, the effects of verapamil (120 mg 3 times daily), nifedipine (20 mg 3 times daily), and placebo were compared in 32 patients with chronic stable angina using a double-blind crossover study design. Compared with placebo, both nifedipine and verapamil prolonged exercise duration (5.7 +/- 0.3 minutes with placebo, 7.9 +/- 0.5 minutes with nifedipine [p less than 0.001], and 10.0 +/- 0.7 minutes with verapamil [p less than 0.001]), but the improvement with verapamil was greater than that seen with nifedipine (p less than 0.01). Seven patients had increasing angina with nifedipine, none did with verapamil; the exacerbation of angina during nifedipine therapy appeared related to our observation that, compared with placebo, patients receiving nifedipine had higher heart rates, while patients receiving verapamil had slower heart rates. This study indicates that, at the doses used, verapamil was more effective and better tolerated than nifedipine in patients with chronic stable angina pectoris.

Randomized double-blind comparison of verapamil and nifedipine in chronic stable angina.

A randomized double-blind crossover trial was performed in 32 patients with chronic stable angina to compare the antianginal actions of verapamil (120 mg 3 times daily) and nifedipine (20 mg 3 times daily). Efficacy was assessed using objective end points obtained by computer-assisted exercise testing and 24 hour ambulatory monitoring for S-T segment shift. Twenty-eight patients completed the trial. The mean exercise time to produce angina improved from 5.7 +/- 0.3 minutes (mean +/- standard error of the mean) in patients on placebo, to 7.9 +/- 0.5 minutes in those on nifedipine and 10.0 +/- 0.7 minutes in those on verapamil. Similar improvement was seen in all other objective variables. Generally verapamil produced mild bradycardia and nifedipine mild tachycardia. Four patients complained of palpitations and angina after ingestion of nifedipine and were identified by ambulatory monitoring to have tachycardia and persistent S-T depression. These opposite effects on heart rate may explain the differences in efficacy between these 2 potent calcium ion antagonists.

Multiple unipolar lead electrocardiographic monitoring during exercise in severe coronary artery disease: a comparison with bipolar lead monitoring.

A system of 21-lead electrocardiography was used to assess 21 patients with severe angina during and after exercise using on-line computerised ST segment analysis. A direct comparison was made between the results obtained from 18 unipolar precordial leads and those from bipolar leads CM5 and CC5. Treadmill exercise was performed 48 hr prior to cardiac catheterization, which revealed luminal narrowing of at least 70% in one or more major coronary arteries in all cases. In all cases the ST depression exceeded 1 mm in both CM5 and CC5 at the peak of exercise. The magnitude of ST depression was greater in the bipolar leads in 75% of cases and in the remaining 25% the greatest peak ST depression occurred in a single unipolar lead. There was no correlation between the magnitude of ST depression and the number of coronary vessels involved. Isopotential surface mapping in the anterior, lateral and inferior projections from the unipolar leads at each stage of exercise failed to show a correlation between the area or distribution of ST segment change and the number or anatomical location of the vessels involved. It was not possible to show that the multiple-lead system could differentiate the site and severity of coronary artery disease in these patients with angina. The multiple-lead system was cumbersome and time-consuming in application and therefore cannot be recommended for routine exercise testing.

Changes of Q wave amplitude during exercise for the prediction of coronary artery disease.

We have examined the changes of Q wave amplitude during exercise in 156 patients with chest pain with a view to improving the accuracy of stress testing for the diagnosis of coronary artery disease. Coronary arteriography showed significant disease in 127 patients and normal arteries or minimal disease in 29. The Q wave amplitude was measured in lead CM5 from the computer-derived average of 25 consecutive beats immediately before and at the peak of maximal treadmill exercise. The amplitude was greater in the normal subjects at rest and increased with exercise, but the reverse occurred in those with coronary disease. Using the criterion of decrease or no change of Q wave amplitude during exercise as indicating a positive test, the discriminative capacity of Q wave changes was equivalent to that of ST segment depression and was maintained when patients with myocardial infarction were excluded. Using either an abnormal Q wave or ST segment response to exercise improved the test's sensitivity with a loss of specificity but no change of predictive value. In 42% of patients with coronary disease when both the Q wave and ST segment exercise responses were abnormal coronary disease was predicted with an accuracy of 91%. Analysis of subgroups of patients with coronary artery disease suggested a possible explanation for the observed changes in Q wave amplitude, measurement of which can improve the stress test's accuracy for predicting obstructive coronary artery disease.

Severe obesity: effects on foot mechanics during walking.

The purpose of our study was to determine the effects of severe obesity on the foot mechanics of adult females. Twenty-nine adult females between the ages of 20 and 48 years volunteered as subjects for this investigation. The subjects were separated into a severely obese (O) group (body mass index = 41.14 +/- 2.61; N = 16) and a normal weight control group (body mass index = 20.84 +/- 0.47; N = 13). A Locam camera (100 Hz) positioned perpendicular to the subjects' posterior aspect was used to film the rearfoot movement of the subjects during the final 15 sec of a 10 min treadmill walk. The O group had a significantly greater touchdown angle (P = .05), more total eversion range of motion (P = .001), and a faster maximum eversion velocity (P < .001). Moreover, analysis of dynamic foot angles indicated that the O group had significantly (P = .003) more forefoot abduction. Finally, anthropometric data revealed statistically different (P < .001) Q angle measurements between the O and control groups. The results of this study suggest that severely obese females have significantly greater rearfoot motion, foot angle, and Q angle values than normal weight females.

Pulmonary telangiectasia.

Two patients with pulmonary telangiectasia are described. One of these is by far the oldest yet reported. The diagnosis and prognosis of this condition are discussed.

Carotid sinus hypersensitivity in patients presenting with syncope.

In 23 patients (ages 44 to 81) presenting with syncope, vertigo, or transient amnesia, carotid sinus massage produced a significant bradycardia in association with symptoms. The 10 most severely symptomatic patients were studied electrophysiologically, including measurement of intracardiac conduction times and corrected sinus node recovery times, as well as with carotid sinus massage before and after atropine. The only detectable abnormality in five of this group was asystole produced by carotid sinus massage; the other five had, in addition, evidence of either sinuatrial disease or an intracardiac conduction defect. Cardiac pacing in these 10 patients completely abolished their symptoms. In a control group of 52 asymptomatic patients (ages 36 to 87), an abnormal response to carotid sinus massage was uncommon (2%).

Alpha-adrenoreceptor blockade with indoramin in hypertension.

We have evaluated the effects of indoramin, an alpha-adrenoreceptor blocking drug, used as sole therapy in a group of 27 patients with essential hypertension. Blood pressure and heart rate were measured continuously over prolonged ambulatory periods using an established invasive technique before and after six weeks of therapy. The protocol was randomised, double-blind, and with double-dummy placebo control. A standardised programme of physiological stress testing was also performed during each study. Placebo produced no appreciable change in the levels or patterns of blood pressure over 24-h periods, but indoramin produced a significant reduction, which was particularly marked during the night. Physiological testing did not reveal any postural hypotension, and the response to dynamic and isometric exercise was modified in level but not in degree of change. There were many unwanted effects, which may limit the clinical value of this drug.