Stoichiometry of microbial continuous-flow purification of toluene-contaminated air.

The applicability of a recently published modification of the chemostat, named "titrostat", for microbial continuous-flow purification of toluene-contaminated air is discussed. This article describes the operative range and the toluene elimination efficiency of a 2-l titrostat running with a mixed bacterial culture dominated by two Acinetobacter species: A. calcoaceticus and A. radioresistens. The study focuses on the kinetics and stoichiometry of the process. Special attention is paid to the peculiarities of toluene as an unconventional growth substrate having high carbon and energy content. Removal productivity as high as 2.24 g l(-1) h(-1) with 99.9% elimination efficiency was observed at air flow rate 60 l h(-1), temperature 32 degrees C, pH 6.2, toluene concentration in the inlet air 37.4 mg l(-1) and titrant solution containing NH3 at 1.87 g l(-1). The maximum biomass yield from assimilated toluene, Ysm=0.880+/-0.011, and a rate of substrate expenditures for cell maintenance, ms=0.022+/-0.002 h(-1), were estimated.

Titrostat: a reliable technique for continuous cultivation of microorganisms utilizing liquid or gaseous water insoluble substrates.

We describe a method for continuous cultivation of microorganisms utilizing liquid or gaseous water insoluble substrates as a single source of carbon and energy. The water insoluble substrate, which is also the growth-limiting factor, enters the cultivation space as a manually adjustable single-compound material flow. All nonlimiting nutrients (with the exception of oxygen) enter the cultivation space as ingredients of titrant solution which feed rate is reliably coupled to the rate of substrate addition by means of the system titrator. The method provides mild starting conditions appropriate for primary isolation of microorganisms utilizing substrates with growth-inhibiting properties such as BTEX (benzene, toluene, ethylbenzene, and xylene). The sound control over the microbial specific growth rate makes it suitable for precise kinetic studies as well. We provide a detailed description of both the principles of the method and the equipment used. The dependence of the systems operative range on the concentration of titrant solution is illustrated in the case of continuous cultivation of a mixed bacterial culture on toluene.

Involvement of renal nerves and endothelins in the regulation of renal water excretion in diabetes insipidus rats.

The interaction between renal nerves, endothelins acting via endothelin-A receptors and vasopressin in the regulation of renal excretory function was investigated. In conscious intact and renal denervated diabetes insipidus (DI) Brattleboro rats, as well as their controls, Long-Evans (LE) rats, an infusion of 16.4 nmol/kg/min ET(A) receptor antagonist BQ-123 was performed in the course of 50 min. Femoral artery blood pressure, heart rate, Ccr, V x U(Na), V x U(K) and V x U(Cl) did not alter in any of the groups. Urine flow rate diminished by 38.1% (p < 0.02), while urine osmolality increased by 30.3% (p < 0.05) as a result of BQ-123 infusion in the intact LE rats but neither urine flow rate nor urine osmolality changed in the DI rats. In contrast to intact LE rats, BQ-123 infusion in renal denervated LE rats did not alter urine flow rate or urine osmolality. However, urine flow rate in renal denervated DI rats surprisingly decreased by 71.1% (p < 0.01) while urine osmolality increased by 161% (p < 0.001) as a result of BQ-123 infusion. Endogenous endothelins can regulate renal water excretion through ET(A) receptor activation. Renal sympathetic nerves participate in the modulation of renal water excretion influencing the ET(A) receptor-mediated effects of endothelins in the kidney.

Renal nerves and endothelins interaction in the control of renal excretory function in conscious Long-Evans rats.

The role of renal nerves and endothelins, acting at ET(A) receptors, in the regulation of renal excretory function was investigated in male Long-Evans rats. Catheters were placed in the femoral vein for fluid and drug infusion, in the femoral artery for blood pressure recording as well as in the bladder for urine collection. Infusion of 16.4 nmol/kg/min of the ET(A) receptor antagonist BQ-123 for 50 min was performed in freely moving, intact and renal denervated rats. As a result of BQ- 123 infusion, urine flow rate diminished (P < 0.02) and Uosm increased (P < 0.05) in the intact rats, but not in the renal denervated rats. Bilateral renal denervation itself as well as ET(A) receptor inhibition in both intact and renal denervated rats did not change the mean arterial pressure, heart rate, or the excretion of sodium, potassium and chloride. The data obtained suggest an interrelationship between renal nerves and endothelin-A receptors in the regulation of renal water excretion.

Effect of lesions to the supramammillary area of the posterior hypothalamus on atrial natriuretic peptide release following acute blood volume expansion in conscious Wistar rats.

Acute blood volume expansion (AVE) is a potent stimulus for atrial natriuretic peptide (ANP) release. Since several central nervous structures are well known for their involvement in the regulation of fluid and electrolyte homeostasis and in the secretion of central ANP, we carried our experiments on 33 conscious Wistar rats in order to determine if the integrity of the supramammillary (SMA) hypothalamic area is essential for the peripheral ANP response to AVE. We performed stereotaxic electrolytic lesions of SMA in part of the animals. To obtain AVE we administered 2 mL saline/100 g b.m. for 2 minutes into v. jugularis through the chronically implanted venous catheters. Plasma ANP was assayed radioimmunologically. AVE significantly increased plasma ANP both in the intact animals and in the lesioned rats. This concluded that SMA is not involved in the regulation of peripheral ANP release during AVE.

Interrelation between the renal sympathetic nerve and atrial natriuretic peptide in conscious long Evans rats subjected to sodium restriction.

The renal excretory function and plasma renin activity (PRA) were studied in conscious rats on a low sodium diet (25 mmol/kg) after atrial natriuretic peptide (ANP) infusion (100 ng/kg b.w./min) for 80 min through a catheter implanted in the right atrium. The half of the animals were with bilateral kidney denervation. The rats were housed every day from 8 a.m. to 2 p.m. in individual metabolic cages for urine collection and Na, Cl, osmolality and endogenous creatinine determination. At the last day of the experiments after the ANP infusion, blood was taken from the heart for electrolytes, endogenous creatinine and PRA. The effect of denervation was monitored by measuring of noradrenaline in kidney homogenate. The data indicated that even at low sodium diet ANP stimulates the diuresis and sodium excretion without changing the glomerular filtration rate (GFR). The kidney denervation combined with ANP infusion increased twice the diuresis and four times sodium excretion vs. the control animals. In the same time PRA was decreased by about 70%. We assume that the low sodium diet attenuates the effect of ANP in respect to the excretory function. This inhibitory effect is amplified by the renal sympathetic nerves. The decrease of PRA and possibly the increased activity of renal receptors after the denervation could explain the data obtained.

Renal excretory function, atrial natriuretic peptide (ANP) and plasma renin activity (PRA) during long-term sodium loading in rats.

The effect of chronic sodium loading on the level of plasma atrial natriuretic peptide (ANP) and on plasma renin activity (PRA), as well as on the renal excretory function was studied. Fifty-six standardly bred Long Evans rats were divided into three experimental groups: controls, rats drinking 170 mmol NaCl/l solution instead of water, and rats consuming food with high sodium content (850 mmol NaCl/kg) for 21 days. During the study, we measured the amount of fluid intake, the parameters of the renal function: diuresis (VU); sodium, potassium and cloride excretion (UNa V, UKV and UClV), and the dynamics of body mass. On the 21st day the animals were sacrificed by decapitation. Plasma ANP and PRA were determined radioimmunologically. Packed cells volume and plasma Na and Cl concentrations were measured. The data showed a full compensation in sodium balance: the body mass dynamics in the three groups was similar; no changes in packed cells volume and plasma electrolytes were seen; UNaV and UClV were significantly increased in the groups with high sodium intake. PRA was significantly depressed in the two groups while ANP did not show any real changes. We concluded that it is PRA and not ANP that might participate in the regulation of chronic sodium balance.

The influence of polymerization conditions on the 3-ketosteroid delta 1-dehydrogenase activity of Mycobacterium globiforme cells included in a gel.

The influence of the conditions of polymerization and the structure of the polyacrylamide gel (PAG) on the 3-ketosteroid delta 1-dehydrogenase activity of a culture of M. globiforme 193 was studied. A clear dependence of the enzymatic activity on the temperature regime and the duration of the polymerization process was established. The reason for the fall in activity with a rise in temperature and an increase in the duration of the polymerization process is the diminution of the quantity of viable cells. The death of the cells is caused by the action of the monomers. The maximum 3-ketosteroid delta 1-dehydrogenase activity appears when the immobilized cells are maintained in a viable state, accomplished by adopting a short time of polymerization (1--2 min) at a temperature of 4--12 degrees C. The specific activity of free cells of M. globiforme and cells immobilized under these conditions is 0.15 mumoles/mg cells . min. The reason for the low activity in a 20% gel is apparently the limited rate of diffusion of the substrate into the gel, conditioned by the small dimensions of the pores of the gel. A change in the concentration of N,N'-methylene bisacrylamide (MBA) from 0.25 to 2% in 5 and 10% gels does no affect the rate of delta 1-dehydrogenation of the substrate.