Production of ethanol by Saccharomyces cerevisiae under high-pressure conditions

A research project was initiated to examine the possibility of using supercritical carbon dioxide for in situ recovery of ethanol during its production by yeast Saccharomyces cerevisiae. As a preliminary step, it was necessary to study the behavior of ethanol production under high-pressure conditions, up to 7 MPa (1000 psi). The results show that pressure has a significant inhibiting effect on the production of ethanol. There is a significant decrease in the initial rate of production as well as in the final ethanol concentration as pressure is increased. This decrease is more significant when carbon dioxide is used to pressurize the fermentor. The pressure affects the ability of the cells to produce ethanol in a reversible way. When the fermentor is returned to atmospheric conditions, the reaction resumes its normal fermentation rate.     

Physiological analysis of running performance: revision of the hyperbolic model

1 This paper presents a physiological model for the analysis of the "running curve" (i.e. the relationship between running time and power output) (Table I and Fig. 1). This model is derived from the basic hyperbolic model (Eq. 2: Fig. 2 a) modified in order to take into account the slow adjustment of oxygen utilization and of glycolysis at the onset of exercise (Eq. 7) and the progressive reduction of average aerobic power sustained with increasing running time for races lasting longer than 7 min (Eq. 10; Fig. 2 b, 2 d). 2 This model provides a satisfactory smoothing of the running curve from 200 m to marathon. Average errors (in absolute value) between actual and estimated power output are 0.9 +/- 0.2% (+/- SE) and 1.3 +/- 0.4% for male and female world records respectively (Table II). The basic hyperbolic model (Ptc = A/tc + B) provides a satisfactory smoothing of the running curve on comparatively narrow ranges of events (Table III). 3 Estimations of anaerobic energy stores and of VO2 max made for male and female from world records (1,219 J.kg-1 and 76.4 ml.kg-1.min-1; 1,118 J.kg-1 and 67.8 ml.kg-1.min-1 respectively) are in reasonable agreement with expected values in elite runners (Table IV). 4 The model allows the computation of an objective measure of endurance, i.e. the so-called "ability to sustain a high percentage of VO2 max for a long period of time".(ABSTRACT TRUNCATED AT 250 WORDS)     

Inhibitory effect of human syncytiotrophoblast plasma membrane vesicles on Jurkat cells activated by phorbol ester and calcium ionophore.

The effects of syncytiotrophoblast plasma membrane vesicles (STPM) on stimulated Jurkat leukemic T cells have been investigated. STPM inhibited IL-2 production and the expression of protein P55 of the IL-2 receptor (IL-2R P55), when Jurkat cells were stimulated by a combination of calcium ionophore A23187 (CaI) + phorbol 12-myristate 13-acetate (PMA). STPM also inhibited IL-2R P55 when cells were stimulated by PMA alone, a situation in which IL-2 production is negligible. On the other hand, STPM had no effect on the sustained mobilization of intracellular Ca2+ induced by CaI nor on the PKC-dependent CD3 down regulation induced by PMA. Finally STPM had no effect on intracellular cAMP levels. These results show that (i) the inhibitory effect of STPM on IL-2R P55 expression is independent of the inhibition of IL-2 production, and (ii) the inhibitory effects of STPM are at least partially independent of phosphatidylinositol 4,5-bisphosphate hydrolysis. They suggest that STPM affect a signaling pathway activated by PMA but possibly PKC independent.     

Quantitative Autoradiography of Tyrosine Hydroxylase Immunoreactivity in the Rat Brain

Levels of tyrosine hydroxylase (TH) were quantified in discrete areas of unfixed rat brain tissue sections using a rapid and sensitive radioimmunohistochemical method. The immunological reaction with the TH monoclonal antibody was revealed by a 35S-labelled secondary antibody and thus permitted autoradiographic detection of the enzyme. Autoradiograms were generated by apposition of tissue sections to high-sensitivity films or by dipping into autoradiographic emulsion. A detailed analysis of antibody concentration, incubation time, tissue section thickness, and exposure time of the film was undertaken to determine optimal conditions to produce a linear radiolabelling intensity with respect to the amount of antigen. Quantification of the antigen at regional levels was assessed by computer-assisted image analysis. Autoradiographic optical density of radiolabelling in brain areas was converted to enzyme concentrations by interpolation with a constructed TH calibration curve processed in parallel with tissue sections. The specificity of the labelling and the validity and reproducibility of the quantification were investigated. The distribution of TH radiolabelling was comparable to that described using immunofluorescence histochemistry or measuring TH enzymatic activity on homogenates. Using a 35S-labelled antibody, the detection of TH could be performed at the cellular level.     

Contribution of blood and systemic circulation to the processing of pro-(atrial natriuretic factor).

Atrial natriuretic factor-(Asn1-Tyr126)-peptide, the 13.6 kDa propeptide of atrial natriuretic factor (ANF), is stored in the secretory granules of atrial cardiocytes. ANF-(Ser99-Tyr126)-peptide, the 28-amino-acid species, is the circulating form of this hormone in the rat. As the site of maturation of the prohormone is still unknown, the present study was undertaken to understand the contribution of the circulation to the maturation process of pro-ANF. 125I-ANF-(Asn1-Tyr126)-peptide was incubated with whole rat blood, plasma or serum for different time intervals, and the products were analysed. There was minimal activation of the propeptide in either whole blood or plasma. Incubation with serum, however, resulted in the formation of an 11 kDa and a 3 kDa peptide which corresponded respectively to the N-terminal and C-terminal parts of the propeptide. These results suggest that hydrolysis of the propeptide in serum is brought about by enzymes that may be stimulated during coagulation but which may not play a major role in the activation of pro-ANF in the circulation. Plasma analysis at different time intervals after prohormone injection indicated a non-specific hydrolysis of the pro-ANF molecule. The disappearance rate curves, obtained with radiolabelled pro-ANF, suggested the presence of two components with half-lives of 2.1 +/- 0.4 min and 52.5 +/- 8.4 min respectively. A metabolic clearance rate of 1.49 +/- 0.22 ml/min and an initial distribution volume of 47.4 +/- 8 ml were calculated. These results indicate that the maturation of pro-ANF to its active circulating form takes place before it is released into the circulation.     

Mass spectrometric determination of the inorganic carbon species assimilated by photoautotrophic cells of Euphorbia characias L

The chemical forms of inorganic carbon, CO2 or HCO3-, incorporated during photosynthesis in photoautotrophic Euphorbia characias cell suspension cultures were determined in experiments using 13CO2 and a mass spectrometry technique. From the equations of the CO2 hydration reaction, a kinetic model was first developed, and the effect of photosynthesis on the external CO2 concentration was simulated. It was predicted from this model that CO2 and HCO3- uptakes could be differentiated by recording only the CO2 variation rate in the external medium, successively in absence then in presence of an exogenous carbonic anhydrase activity. The results obtained with either CO2-grown or air-grown photoautotrophic cells were in good agreement with the model and demonstrated that CO2 was the sole species taken up during photosynthesis. In addition no accumulation of inorganic carbon within the cells was observed in the light. Similarly, in dark, CO2 was the only species released by respiration in the external medium.     

Evaluation of bull semen fertility by homologous in vitro fertilization tests

In vitro fertilization assays were performed to investigate their validity in evaluating artificial insemination (AI) bull fertility. A total of 1,532 oocytes, collected from ovaries at the abattoir, were subsequently used in a 4 x 6 x 2 factorial design: 4 doses of heparin added into the capacitation and fertilization medium (0; 0.05; 0.1 and 0.2 micrograms/ml), 6 different bulls with known on-field non-return (NR) rates (range: 64.6-75.3%) and 2 different ejaculates for each bull, collected within a approximately 1-month interval. Oocytes were considered fertilized when 2 pronuclei (or more) were seen in the ooplasm. Both the heparin dose and bull exerted a highly significant effect on the in vitro fertilization (IVF) rates which ranged, per oocyte group, from 30-80%; bull x dose of heparin interaction was significant (P less than 0.001). The 0.05 micrograms/ml dose of heparin was optimal for discriminating individual bulls. At that dose, the correlation coefficients between the bulls, NR rates and the IVF rates from each ejaculate (within-bull or the mean of two ejaculates), were highly significant (r = 0.83). The rates of polyspermy were also significantly influenced by bull and heparin dose, but there was no interaction. In conclusion, capacitation and fertilization in a modified Tyrode medium containing 0.05 micrograms/ml of heparin may be a valuable tool for evaluating AI bull fertility.     

Effects of biaxial deformation on pulmonary artery endothelial cells

An apparatus has been designed to subject vascular cells grown on a compliant substrate in vitro to uniform, quantifiable levels of biaxial deformation. The system described can be controlled with respect to strain level, rate, and frequency to mimic the pulsatile force to which vascular cells are exposed in vivo under both physiologic and pathologic conditions. In the experiments presented here, bovine pulmonary artery endothelial cells were grown on a substrate of segmented polyurethane urea (Mitrathane). Cell growth and morphology on this substrate were compared with those of cells grown on standard tissue culture polystyrene with no difference noted between the two substrates. Primary cultures of pulmonary artery endothelial cells were seeded onto Mitrathane, which was then subjected to cyclic biaxial deformation-producing strains of 0.78%, 1.76%, 4.9%, or 12.5% at a frequency of 1 sec-1 and a duty cycle of 0.5 sec-1 for 7 h. Cells subjected to deformations generating strains of either 4.9% or 12.5% secreted significantly less fibronectin than nondeformed cells. Similar results were obtained in experiments using cloned pulmonary artery endothelial cells on Mitrathane subjected to the 4.9% strain; however, total protein synthesis was increased. Cell viability and DNA synthesis were not affected by cyclic biaxial deformation in these experiments.     

Relationship of decreased hepatic lipase activity and lipoprotein abnormalities to essential fatty acid deficiency in cystic fibrosis patients

Polyunsaturated fatty acids are known to affect plasma lipids and lipoproteins but there is no information on the effect of essential fatty acid (EFA) deficiency on lipoprotein composition. The purpose of this study was to characterize lipoproteins from 17 cystic fibrosis (CF) patients in relationship to their EFA status (eicosatrienoic/arachidonic acid ratio) and compare them with those of 10 healthy siblings (SIB) and of 10 unrelated controls. In 7 EFA-deficient (EFAD) and 10 EFA-sufficient (EFAS) patients, hypocholesterolemia was associated with a decrease of HDL-cholesterol and of LDL-cholesterol which was more marked in the EFAD group. Similarly, although triglyceride enrichment of VLDL, LDL, HDL2, and HDL3 with a concomitant reduction of cholesteryl esters from all particles except HDL2 was observed in both CF groups, it was more sizable in the EFAD patients. These changes led to an increase in the particle size of VLDL, LDL, and HDL2 whereas the distribution of HDL3 was skewed to smaller particles. Alterations in the apoprotein composition of particles were greater in EFAD than in EFAS. A decrease of total postheparin lipolytic activity was observed in the two groups of CF patients as well as in siblings. It was entirely accounted for by hepatic lipase (mumol FFA/ml per h) which was more severely diminished in EFAD (2.8 +/- 0.6) than in EFAS (4.4 +/- 0.7) and SIB (5.1 +/- 0.5). Although the two groups of CF children differed in terms of growth, severity of malabsorption, and vitamin E status, these data suggest that disturbance of lipoprotein concentration, composition, size, and metabolism (hepatic lipase) may be in part related to EFA deficiency. Further studies are necessary to explore the effect of EFA deficiency on hepatic lipase activity.