Polymer-Based Conductive Nanocomposites for the Development of Bioanodes Using Membrane-Bound Enzyme Systems of Bacteria Gluconobacter oxydans in Biofuel Cells

The development of biofuel cells (BFCs) currently has high potential since these devices can be used as alternative energy sources. This work studies promising materials for biomaterial immobilization in bioelectrochemical devices based on a comparative analysis of the energy characteristics (generated potential, internal resistance, power) of biofuel cells. Bioanodes are formed by the immobilization of membrane-bound enzyme systems of Gluconobacter oxydans VKM V-1280 bacteria containing pyrroloquinolinquinone-dependent dehydrogenases into hydrogels of polymer-based composites with carbon nanotubes. Natural and synthetic polymers are used as matrices, and multi-walled carbon nanotubes oxidized in hydrogen peroxide vapor (MWCNTox) are used as fillers. The intensity ratio of two characteristic peaks associated with the presence of atoms C in the sp³ and sp² hybridization for the pristine and oxidized materials is 0.933 and 0.766, respectively. This proves a reduced degree of MWCNTox defectiveness compared to the pristine nanotubes. MWCNTox in the bioanode composites significantly improve the energy characteristics of the BFCs. Chitosan hydrogel in composition with MWCNTox is the most promising material for biocatalyst immobilization for the development of bioelectrochemical systems. The maximum power density was 1.39 × 10^-5 W/mm², which is 2 times higher than the power of BFCs based on other polymer nanocomposites.

Antagonistic activity of synbiotics: Response surface modeling of various factors

Synbiotic compositions have a great potential for curing microbial intestinal infections. Novel targeted synbiotics are a promising field of the modern functional food industry. The present research assessed the effect of various fructan fractions, initial probiotic counts, and test strains on the antagonistic properties of synbiotics. The research involved powdered roots of Arctium lappa L. and strains of Bifidobacterium bifidum, Bacillus cereus, and Salmonella enterica. The experiment was based on the central composite rotatable design. A water extract of A. lappa roots was purified and concentrated. Fructan fractions were precipitated at various concentrations of ethanol, dried, and sub jected to carbon-13 nuclear magnetic resonance (13C-NMR) spectrometry. The bifidobacteria and the test strains were co-cultivated in the same medium that contained one of the fractions. Co-cultivation lasted during 10 h under the same conditions. The acid concentrations were determined by high-performance liquid chromatography to define the synbiotic factor. The obtained fructans were closer to commercial oligofructose in terms of the number and location of NMR peaks. However, they were between oligofructose and inulin in terms of signal intensity. The response surface analysis for bacilli showed that the minimal synbiotic factor value corresponded to the initial probiotic count of 7.69 log(CFU/mL) and the fructan fraction precipitated by 20% ethanol. The metabolites produced by the bacilli also affected their growth. The synbiotic factor response surface for the experiments with Salmonella transformed from parabolic to saddle shape as the initial test strain count increased. The minimal synbiotic factor value corresponded to the lowest precipitant concentration and the highest probiotic count. The research established a quantitative relationship between the fractional composition of fructans and the antagonistic activity of the synbiotic composition with bifidobacteria. It also revealed how the ratio of probiotic and pathogen counts affects the antagonism. The proposed approach can be extrapolated on other prebiotics and microbial strains in vivo.

Lacidipine: effects on vascular pressor responses throughout the dosage interval in normotensive subjects

AIMS

To assess the duration and consistency of the pharmacological activity of the dihydropyridine calcium antagonist drug, lacidipine.

METHODS

Eight healthy normotensive young males participated in a double-blind randomised crossover comparison of single and multiple doses (for 2 weeks) of lacidipine and placebo. The calcium antagonist effects were quantified at 2, 6 and 24 h post dose by the extent of the attenuation of the pressor responses to the intravenous administration of the vasoconstrictors angiotensin II and noradrenaline.

RESULTS

After 2 weeks of treatment, lacidipine consistently and significantly attenuated the pressor responses to both agents at 2 h post dose. At 6 and 24 h post dose there was a significant and progressive decline in the effectiveness of lacidipine in attenuating the pressor responses and for the response to angiotensin II there was no statistically significant effect at either 6 or 24 h post dose.

CONCLUSIONS

These results indicate that there is an obvious 'peak' in the pharmacological activity of lacidipine at about 2 h post dose and that this activity is not fully and consistently maintained throughout 24 h.

Do beta-blockers have a role in the treatment of chronic heart failure?

There has been growing interest in and recognition of the role of beta-blockers in chronic heart failure (CHF). The mode of action is complex and several mechanisms have been proposed. The principal rationale for the use of beta-blockade is to counteract neurohormonal activation and its deleterious consequences in CHF. While the positive effect of this treatment on haemodynamics, exercise tolerance and quality of life, and a clear trend in favour of improved prognosis have been shown, there is still no concrete proof that beta-blockers reduce mortality in CHF. Several large-scale, prospective, randomised, placebo-controlled trials, designed to provide a definitive answer, are underway.

The effects of rilmenidine and atenolol on mental stress, dynamic exercise and autonomic function in mild to moderate hypertension

1. The effects of 4 week treatment with rilmenidine or atenolol on tests of mental stress, dynamic exercise, autonomic function and psychometric tests were evaluated in a randomized, double-blind, placebo-controlled, cross-over study. 2. After a 4 week placebo run-in, 12 patients with essential hypertension (blood pressure [BP] 160/95 +/- 15/7 mmHg) received rilmenidine 1-2 mg day-1, and atenolol 50-100 mg day-1, each for 4 weeks, with a 4 week placebo wash-out between drug treatments. 3. Both agents produced a comparable reduction in supine and erect BP. During the mental arithmetic test, BP and heart rate (HR) responses were similar for rilmenidine and atenolol. 4. During bicycle exercise, the increase in HR was significantly greater after rilmenidine (+50 vs 41 beats min-1, P = 0.04). During recovery, the areas under the curve for diastolic BP (46,450 vs 51,400 mmHg s, P = 0.02) and HR (49,445 vs 63,597 beats min-1 s, P = 0.001) were significantly less with atenolol than rilmenidine. 5. Neither rilmenidine nor atenolol affected mental performance as judged by arithmetic and psychomotor tests. Physiological responses to autonomic function tests (deep breathing, facial immersion, isometric handgrip and cold pressor) were preserved with both drugs. The standing to lying ratio was higher on atenolol (P = 0.01) and Valsalva ratio was higher on rilmenidine (P = 0.03). 6. In conclusion, rilmenidine and atenolol exerted comparable antihypertensive effects both at rest and during mental and dynamic stress. Atenolol attenuated HR responses to dynamic exercise and the Valsalva manoeuvre; rilmenidine did not interfere with the physiological responses of BP and HR during autonomic function tests.

Clinical pharmacology of drugs acting on imidazoline and adrenergic receptors. Studies with clonidine, moxonidine, rilmenidine, and atenolol

Centrally acting antihypertensive drugs are recognized to be safe and effective treatment for high blood pressure. Centrally mediated side effects, such as sedation, are commonly dose- and treatment-limiting events. Imidazoline-preferring receptors, while functionally similar to alpha 2 adrenoceptors, are distinguishable not only on the basis of in vitro radioligand binding but also in vivo in terms of side effects. Drugs with an imidazoline structure lower blood pressure but are less likely to impair psychomotor function. A placebo-controlled study compared moxonidine 0.1 mg with clonidine 0.1 mg orally in nine normal subjects. Both active drugs lowered blood pressure compared to placebo (clonidine more than moxonidine). However, psychomotor function and self-scored sedation and dry mouth were significantly affected only by clonidine. In a long-term (4 weeks) double-blind cross-over study in essential hypertension, rilmenidine was well tolerated and had similar effects to those of atenolol on erect and supine blood pressure. Rilmenidine had no effect on a wide range of autonomic and psychomotor tests or on responses to mental or physical stress. Atenolol, by contrast, had the predicted effects of a beta adrenoceptor antagonist on heart rate during exercise and the Valsalva maneuver. Imidazoline-preferring drugs offer a new and realistic approach to antihypertensive therapy with blood pressure reduction not limited by marked sedation within the therapeutic dose range.

Use of beta-adrenoceptor blockers in patients with congestive heart failure

The beneficial effect of chronic beta-blockade in patients with congestive heart failure has been repeatedly shown since its introduction into treatment for this condition in 1975. Still this kind of therapy remains controversial, it is sometimes regarded as a therapeutic paradox, and its use is mainly limited to specialist centers. Various favorable effects of beta-blockers in patients with heart failure due to idiopathic dilated cardiomyopathy and ischemic heart disease have been demonstrated, the principal among them being reduction in energy requirements and ischemia, antiarrhythmogenic effect, improvement of diastolic function, protection of myocytes against catecholamine overload, centrally mediated increase in vagal tone, upregulation of beta-adrenergic receptors, and possible blockade of autoantibodies against beta 1-receptors. Although most of the studies used metoprolol, these effects may be relevant to certain other beta-blockers. Despite very solid pathophysiological and pharmacological rationales for the use of beta-blockade, a major obstacle for a general acceptance of this therapeutic concept is the striking contrast between hemodynamic changes during the acute effect and long-term treatment. When titrated carefully from very low doses and used with a true commitment to long-term treatment, beta-blockers have been shown to prevent further deterioration of heart failure and to improve hemodynamics, exercise tolerance, quality of life, and prognosis.

Body weight and fat cell size in young men with mild blood pressure elevation

The aim of the study was to assess the relationship between body fat distribution and blood pressure. Forty-four men, aged 19-22 years, with mild blood pressure elevation (MBPE) and 29 normotensive controls (NC) were investigated. Body fat distribution was assessed by calculating fat cell size in biopsy samples of adipose tissue from different subcutaneous depots. The subjects in MBPE group were heavier than those in NC group (79.7 +/- 2.7 and 71.5 +/- 1.6 kg, p < 0.05). Total body fat was also significantly higher in the MBPE group (12.5 +/- 1.6 and 8.1 +/- 1.3 kg, p < 0.05) but not the lean body cell mass (36.8 +/- 1.1 and 34.7 +/- 0.9 kg, n.s.). Fat cell size (microgram/cell) in the lower abdominal area were significantly bigger in MBPE than in NC (respectively 40.9 +/- 4.4 and 28.0 +/- 3.1, p < 0.05). The same differences applied for fat cell size in the upper abdominal (respectively 43.1 +/- 3.0 and 26.8 +/- 3.0, p < 0.001) and averaged abdominal areas (respectively 40.1 +/- 3.4 and 26.8 +/- 2.8; p < 0.05). Fat cell size in gluteal, femoral and averaged gluteofemoral areas did not differ between MBPE and NC. Therefore, the abdominal/gluteofemoral ratio was significantly higher in MBPE than in NC (respectively 1.1 +/- 0.1 and 0.7 +/- 0.1; p < 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Circulatory effects of nitroglycerin ointment (Nitrong) with special reference to venous distensibility

Nitroglycerin ointment (Nitrong 2%, 5 cm) and an identical placebo ointment were tested in a double-blind crossover study in five healthy volunteers to determine its influence on heart rate, blood pressure, and venous distensibility during supine rest and at 45 degrees tilt. Two hours after administration, a significantly higher venous distensibility was observed with the active ointment than with placebo. There were insignificant changes in heart rate and blood pressure. Three of the five subjects experienced headache for 6 h or more after active ointment.

Effect of nitroglycerin ointment (Nitrong) on exercise tolerance and several circulatory parameters in patients with angina pectoris

Nine patients with coronary heart disease, 8 of whom were taking adrenergic beta-blockers, were tested by dynamic (bicycle) and isometric (sitting handgrip) exercise before and 2 and 6 h after application of nitroglycerin 30 mg in an ointment, or a matching placebo ointment, over 225 cm2 surface on the chest, in a double-blind, cross-over, single dose study. Exercise time until stopping from chest pain was significantly increased (by about 20%) by active ointment, and electrocardiographic ST-depression and chest pain intensity were significantly less pronounced during exercise both 2 and 6 h after application. During seated rest, active ointment also produced a significantly lower systolic blood pressure and a significantly higher heart rate at both 2 and 6 h, whereas during handgrip, significant differences from placebo were seen only at 2 h. All patients experienced headache for at least the 6 h of the study. At a given heart rate, ST-depression was less pronounced with active ointment than with placebo.

Cardiovascular effect of nicotine chewing gum in healthy non-smokers

Nicotine chewing gum (Nicorette 4 mg) and an identical placebo gum were administered on different days, in a double-blind cross over fashion, to 4 men, aged 25-52 years, and 4 women, aged 21-49 years, all healthy non-smokers. The subjects chewed the gum for 30 min and heart rate, blood pressure, electrocardiogram, finger tip temperature, calf and hand blood flow and whole blood nicotine levels were measured for 240 min in the supine position, under indirect body heating. 72% -96% of the nicotine was absorbed. Only heart rate showed a significant increase (10%-12%) during the study as compared to placebo. The mean peak nicotine level was 6.5 ng/ml, which occurred at 15-60 min and roughly coincided with the peak heart rate, and then levelled off to around 3 ng/l at 120-240 min. All subjects complained of nausea, dizziness or anxiety to varying degrees. It is concluded that if healthy non-smokers chew Nicorette gum 4 mg by mistake, they would probably suffer more from generally unpleasant symptoms than from any cardiovascular upset.

Haemodynamic effects of withdrawal of long-term treatment with beta-adrenoceptor blocking agents in subjects with essential hypertension

1. After 10 years of beta-adrenoceptor blockade in five female patients with essential hypertension, the beta-adrenoceptor-blocking agent was withdrawn, and the women were then followed up for 1 year, with measurements of cardiac output and peripheral resistance. 2. Blood pressure remained low during the first year after withdrawal in spite of the fact that the heart rate increased within the first few days. 3. Cardiac output was found to increase during the first year after withdrawal, although total peripheral resistance was essentially unchanged. 4. The maintenance of low blood pressure after withdrawal of the antihypertensive drug might indicate a regression of structural changes in the resistance vessels during successful long-term antihypertensive treatment. 5. Minimal resistance in hands and calves did not increase during the year after withdrawal.