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At least 145 records · Page 8Linked to original sources
PubMed1980

Inhibition of cell-mediated lysis by xenoantibodies reactive with effector T lymphocytes.

The aim of the present study was to determine whether rabbit antisera against various murine tissue antigens contain antibodies that affect the activity of cytotoxic T lymphocytes in the absence of complement. Following heat inactivation, the xenoantisera were absorbed with mouse liver and kidney and tested for their capacity to inhibit cell-mediated lysis (CML). In the presence of complement (C), rabbit anti-brain antiserum (RABr), rabbit anti-thymus antiserum (RAT) and rabbit anti-boiled thymus antiserum (RABT) lysed effector T cells, and CML was abolished. In the absence of C, RAT maintained its strong inhibitory activity on CML, RABr had no inhibitory effect, whereas only some batches of RABT were effective. Monovalent Fab fragments of RAT inhibited CML as effectively as intact antibody molecules. The activity of RAT could be removed by absorption with T and B lymphocytes of various sources. Inhibitory antibodies could be removed by absorption with C3 H B lymphoma cells and upon elution from antibody-coated cells proved again highly effective in inhibiting CML. These results show that RAT contains antibodies which react with determinants shared by T and B lymphocytes and which block the activity of cytotoxic T cells.

Animals↗
PubMed2006

Kinetics of batch ethanol fermentation of cheese-whey powder (CWP) solution as function of substrate and yeast concentrations.

A lactose utilizing yeast strain, Kluyveromyces marxianus DSMZ-7239 was used for ethanol formation from cheese-whey powder (CWP) solution in batch experiments. Effects of initial substrate (CWP) and yeast concentrations on the rate and extent of ethanol formation were investigated. The initial pH and oxidation-reduction potential (ORP) was kept at 5 and -250 mV, respectively. The rate and extent of ethanol formation increased with increasing CWP concentration up to 156 g l(-1) (75 g l(-1) sugar) and then decreased for larger CWP concentrations due to substrate inhibition at high sugar concentrations. The ethanol yield coefficient was also maximum (0.54 g EtOH/g sugar) and equal to the theoretical yield at CWP concentration of 156 g l(-1). The growth yield coefficient was found to be Y(x/s)=1.2+/-0.1g biomass g sugar(-1). The rate of sugar utilization and ethanol formation also increased linearly with increasing initial biomass concentrations. A kinetic model describing the rate of sugar utilization and substrate inhibition as function of the initial substrate and the biomass concentrations was developed. The kinetic constants were determined using the experimental data. Model predictions of sugar utilization rates were in good agreement with the experimental data. The results indicated that the initial sugar concentration should be below 75 g l(-1) (CWP<156 g l(-1)) and the initial biomass should be above 850 mg l(-1) to obtain high rates and yields of ethanol formation and to avoid substrate inhibition.

Cheese↗
PubMed2005

Kinetic modeling of liquid-phase adsorption of reactive dyes on activated carbon.

In this paper, adsorption equilibrium and kinetics of three reactive dyes from their single-component aqueous solutions onto activated carbon were studied in a batch reactor. Effects of the initial concentration and adsorbent particle size on adsorption rate were investigated Adsorption equilibrium data were then correlated with several well-known equilibrium isotherm models. The kinetic data were fitted using the pseudo-first-order equation, the pseudo-second-order equation, and the intraparticle diffusion model. The respective characteristic rate constants were presented. A new adsorption rate model based on the pseudo-first-order equation has been proposed to describe the experimental data over the whole adsorption process. The results show that the modified pseudo-first-order kinetic model generates the best agreement with the experimental data for the three single-component adsorption systems.

Journal Article↗
PubMed2004

Vero-cell rabies vaccine produced using serum-free medium.

A new rabies vaccine was developed from Vero cells adhered to microcarriers, cultivated in a bioreactor in serum-free medium and infected with the PV/VERO-Paris rabies virus strain. The viral suspensions were concentrated by tangential filtration, purified by chromatography and inactivated with beta-propiolactone. In immunogenicity studies performed in mice immunized with three doses of the new vaccine (seven batches) and the commercial Verorab and HDCV, mean titers of neutralizing antibodies of 10.3-34.6, 6.54 and 9.36 IU/ml were found, respectively. The vaccine presented stability during 14 months at 2-8 degrees C, 30 days at 37 degrees C and 8 h at 45 degrees C. The use of serum-free medium facilitated the downstream process leading to residual cellular DNA values <22.8 pg per dose of vaccine in all produced batches. The effective immunogenicity induced in mice by this vaccine, the degree of purity of the product, the high antigen yield and the reduction of the cost of the product due to the virus production and purification processes, makes this technology very important for countries where rabies presents a great public health problem.

Animals↗
PubMed2001

Immobilized penicillin G acylase as reactor and chiral selector in liquid chromatography.

In this paper, the use of penicillin G acylase (PGA) as a biocatalyst and as a chiral selector is described. Penicillin G-acylase is an interesting enzyme used in the manufacture of semisynthetic antibiotics and, in particular, in the production of 6-APA by hydrolysis of penicillin G. Five PGA-based HPLC columns have been prepared by using two different silica supports by employing two immobilization methods, namely "in situ" and "in batch". The effects of the immobilization techniques and of different silica pore size on the catalytic properties of the enzyme as well as the applicability of the PGA-bonded stationary phases as chiral selectors for a number of chiral drugs have been investigated. The HPLC columns based on immobilized PGA combine the hydrolytic activity and the chiral recognition properties of PGA, therefore they have been used for the development of a combined reaction-separation system for chiral and achiral substrates.

Catalysis↗
PubMed2001

A novel airlift photobioreactor with baffles for improved light utilization through the flashing light effect.

A newly developed flat panel airlift photobioreactor with a defined circulation path was tested for microalgal culture. The bioreactor exposed the cells to intermittent light to improve the efficiency of light utilization through the flashing-light effect. During batch cultures in the new photobioreactor, the biomass productivity of Chlorella vulgaris was 1.7 times greater than in a randomly mixed bubble column of identical dimension. A reduction in light path from 30 to 15 mm increased the biomass productivity by 2.5-fold. A maximum dry biomass productivity of 0.11 g l(-1) h(-1) was obtained at an artificial illumination of 980 mu E m(-2) s(-1).

Biomass↗
PubMed1999

The use of multi-parameter flow cytometry to compare the physiological response of Escherichia coli W3110 to glucose limitation during batch, fed-batch and continuous culture cultivations.

Multi-parameter flow cytometric techniques have been developed for the 'at-line' study of bacterial cultivations. Using a mixture of specific fluorescent stains it is possible to resolve an individual cells physiological state beyond culturability, based on the presence or absence of an intact polarised cytoplasmic membrane, enabling assessment of population heterogeneity. It has been shown that during the latter stages of small-scale (5 l), well mixed fed-batch cultivations there is a considerable drop in cell viability, about 17%, as characterised by cytoplasmic membrane depolarisation and permeability. These phenomena are thought to be due to the severe and steadily increasing stress associated with glucose limitation at high cell densities, during the fed-batch process. Such effects were not found in either batch or continuous culture cultivations. The possibility of using these findings for improved process control using 'on-line' flow cytometry are discussed.

Adaptation, Physiological↗
PubMed2001

Anterior chamber depth estimation by Scheimpflug photography.

PURPOSE: To obtain a model suitable for evaluation of the anterior chamber depth (ACD) maintaining capacity of viscoelastic substances--a critical parameter in cataract surgery. METHODS: ACD was estimated using an anterior segment analysis system (EAS-1000, Nidek Co Ltd, Japan). Variation was studied as an effect of batch number and eye within batch, storage, globe fixation, globe position, and repeated analyses of Scheimpflug images. RESULTS: Considerable variation in ACD was found between eyes, batches, and as a result of prolonged storage (biological factors). Different IOPs before surgery caused significant alterations in ACD after overfilling with a viscoelastic substance. No significant differences were found when the globe position was altered or when the ACD was re-estimated repeatedly from the same photograph. CONCLUSION: Differences due to biological factors are more important than methodological errors caused by the Scheimpflug instrument. To reduce these variations when viscoelastics are evaluated, all measurements should be calculated as % of ACD before surgery and the anterior chamber should be overfilled with a viscoelastic solution.

Animals↗
PubMed1988

Effect of sorbinil on myo-inositol metabolism in cultured neuroblastoma cells exposed to increased glucose levels.

Neuroblastoma cells were used to determine the effect of sorbinil on myo-inositol metabolism in cells exposed to elevated levels of glucose in culture. Exposing cells to elevated levels of glucose led to an increase in levels of intracellular sorbitol. The increase in sorbitol levels was dependent on the extracellular glucose concentration. In contrast, the myo-inositol content of cells was decreased in the presence of increasing concentrations of extracellular glucose. Increasing the concentration of glucose in the culture medium caused a decrease in myo-inositol uptake and in the incorporation of extracellular myo-inositol into phospholipid. The effect of elevated glucose levels on myo-inositol metabolism and sorbitol accumulation was blocked by addition of 0.4 mM sorbinil. The ability of sorbinil to block the decrease in myo-inositol metabolism and sorbitol accumulation caused by 30 mM extracellular glucose was dependent on its concentration. Maximal effects were obtained with 0.4 mM sorbinil. However, there was some variation in the degree of effectiveness among batches of sorbinil. These results at the cellular level suggest that the intracellular accumulation of sorbitol is responsible for the alteration of myo-inositol metabolism observed in neuroblastoma cells exposed to elevated glucose concentrations.

Animals↗
PubMed1981

Unsuitability of evacuated tubes for monitoring heparin therapy by activated partial thromboplastin time.

Activated partial thromboplastin times (APTT) for monitoring heparin therapy for venous thromboembolism tended to be inappropriately short if blood was collected in commercially available evacuated glass tubes. Five types of evacuated tubes marketed under the trade names Vacutainer and Venoject were examined. The APTT of heparinized blood collected in these tubes correlated poorly (r = 0.04 to 4 = 0.25) with that of blood samples from the same patients collected in plastic tubes. Most of the evacuated tube APTT were shorter than that of blood collected in plastic or siliconised glass tubes, but the results were unpredictable and varied from tube to tube and from batch to batch. This effect on heparin is apparently due to an unidentified substances which is eluted from the rubber stoppers of the tubes. Heparin control according to the APTT blood collected in these evacuated tubes is hazardous.

Blood Coagulation Tests↗
PubMed2000

Scale-up effects on dissolution and bioavailability of propranolol hydrochloride and metoprolol tartrate tablet formulations.

This study evaluated the effects of batch size on the in vitro dissolution and the in vivo bioavailability of immediate release formulations of propranolol hydrochloride and metoprolol tartrate. The formulations were manufactured as small and large batches (6 kg and 60 kg for propranolol; 14 kg and 66 kg for metoprolol), and dissolution was performed using USP Apparatus I at 100 rpm and pH 1.2. Two panels of 14 subjects each were randomly assigned to receive the small and large batches of either propranolol or metoprolol in an open, randomized single-dose study. Blood samples were collected over a 24-hour (propranolol) or 18-hour (metoprolol) period and analyzed by validated methods. As determined by the f2 metric (similarity factor), the dissolution of the small and large batches of propranolol and metoprolol was similar. The mean Cmax and AUC(inf) for the small batch of propranolol were 79.0 microg/L and 536 microg/L/hr, and for the large batch they were 83.5 microg/L and 575 microg/L/hr. Cmax and AUC(inf) for the small batch of metoprolol were found to be 95.5 microg/L and 507 microg/L/hr and for the large batch, 95.1 microg/L and 495 microg/L/hr. The 90% confidence intervals for the small and large batches were within the 80% to 120% range for lnCmax, and lnAUC(inf) for both the propranolol and metoprolol formulations. These results suggest that the scale-up process does not significantly affect the bioavailability of highly soluble, highly permeable drugs and in vitro dissolution tests may be useful in predicting in vivo behavior.

Adult↗
PubMed1994

Application of reliability models to studies of biomarker validation.

We present a model of biomarker validation developed in our laboratory, the results of the validation study, and the impact of the estimation of the variance components on the design of future molecular epidemiologic studies. Four different biomarkers of exposure are illustrated: DNA-protein cross-link (DNA-PC), DNA-amino acid cross link (DNA-AA), metallothionein gene expression (MT), and autoantibodies to oxidized DNA bases (DNAox). The general scheme for the validation experiments involves n subjects measured on k occasions, with j replicate samples analyzed on each occasion. Multiple subjects, occasions, and replicates provide information on intersubject, intrasubject, and analytical measurement variability, respectively. The analysis of variance showed a significant effect of batch variability for DNA-PC and MT gene expression, whereas DNAox showed a significant between-subject variability. Among the amino acids tested, cysteine and methionine showed a significant contribution of both batch and between-subject variability, threonine showed between-subject variability only, and tyrosine showed between-batch and between-subject variability. The total variance estimated through the experiment was used to calculate the minimum sample size required for a future epidemiologic study including the same biomarkers used for the reliability study. Such validation studies can detect the various components of variability of a biomarker and indicate needed improvements of the assay, along with possible use in field studies.

Amino Acids↗
PubMed1987

Poultry offal ensiled with lactobacillus acidophilus for growing and finishing swine diets.

Poultry offal (heads, feet, viscera) from a broiler processing plant was ground and mixed with corn, dried molasses and a Lactobacillus acidophilus culture. Fermentation was shown to be effective in batch sizes of 3.8, 75.7 and 208.1 liters, as well as a 1,360-kg silo. It was generally complete at 72 h. In trial 1, rats were fed silage mixtures of 60:30:5:5, 45:45:5:5 and 30:60:5:5, offal, corn, molasses and inoculant, respectively. Rats did not gain as well when fed the silage diets (P less than .05) as when fed the basal diet; however, the ranking of silages was 45:45, 60:30 and 30:60, offal-to-corn ratio for rat daily gains and feed conversions. In trial 2, growing-finishing pigs were fed the 60:30:5:5 silage at rates of 0, 10, 20 and 30% of the diet. Average daily gains and feed-to-gain ratios were not affected by including offal silage at up to 20% of the diet, but 30% offal silage in diets resulted in depressed gains (P less than .05) and increased feed-to-gain ratios. Carcasses were not different among treatments for dressing percentage, length, average backfat and percentage of ham, loin, shoulder, lean cuts and primal cuts. Carcasses from pigs fed 20 and 30% offal silage had significantly darker and firmer loin-eyes than those from control fed pigs. Marbling was higher (P less than .05) in loin-eyes from pigs fed 30% offal silage as compared with those from pigs fed 0% offal silage.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed2000

A kinetic analysis of hybridoma growth and metabolism in batch and continuous suspension culture: effect of nutrient concentration, dilution rate, and pH. Reprinted from Biotechnology and Bioengineering, Vol. 32, Pp 947-965 (1988).

Hybridomas are finding increased use for the production of a wide variety of monoclonal antibodies. Understanding the roles of physiological and environmental factors on the growth and metabolism of mammalian cells is a prerequisite for the development of rational scale-up procedures. An SP2/0-derived mouse hybridoma has been employed in the present work as a model system for hybridoma suspension culture. In preliminary shake flask studies to determine the effect of glucose and glutaminE, it was found that the specific growth rate, the glucose and glutamine metabolic quotients, and the cumulative specific antibody production rate were independent of glucose concentration over the range commonly employed in cell cultures. Only the specific rate of glutamine uptake was found to depend on glutamine concentration. The cells were grown in continuous culture at constant pH and oxygen concentration at a variety of dilution rates. Specific substrate consumption rates and product formation rates were determined from the steady state concentrations. The specific glucose uptake rate deviated from the maintenance energy model(1) at low specific growth rates, probably due to changes in the metabolic pathways of the cells. Antibody production was not growth-associated; and higher specific antibody production rates were obtained at lower specific growth rates. The effect of pH on the metabolic quotients was also determined. An optimum in viable cell concentration was obtained between pH 7.1 and 7.4. The viable cell number and viability decreased dramatically at pH 6.8. At pH 7.7 the viable cell concentration initially decreased, but then recovered to values typical of pH 7.1-7.4. Higher specific nutrient consumption rates were found at the extreme pH values; however, glucose consumption was inhibited at low pH. The pH history also influenced the behavior at a given pH. Higher antibody metabolic quotients were obtained at the extreme pH values. Together with the effect of specific growth rate, this suggests higher antibody production under environmental or nutritional stress.

Animals↗
PubMed1980

Bioavailability of two preparations of frusemide.

This study examined the relative diuretic effectiveness of batches of 40 mg tablets of the Frusid and Lasix formulations of frusemide in health volunteers. There were no significant differences in the urinary volume or urinary contents of Na+, K+ and Cl- following the oral administration of either preparation. It is concluded therefore that the batches studied had equivalent bioavailability.

Adult↗
PubMed1994

[Effect of various rabbit complement batches of HLA class I antigen determination in lymphocytotoxicity testing].

HLA class I lymphocytotoxicity testing is strongly complement-dependent. We tested 13 commercially available rabbit complement batches (7 distributors) using a panel of 14 donors with decisive patterns of HLA antigens. We defined a scoring system that weights the different possible faulty reactions. The rating score ranged from 12.45 to 46.55 (median 16.09). Comparing the reactions in batches with low and high rating scores gave statistically significant differences (chi 2 test, p < 0.05). Our complement reaction score may be helpful to find the optimal complement batch for HLA class I lymphocytotoxicity testing.

Animals↗
PubMed2000

Response of the thermophile Thermus sp. RQ-1 to hyperbaric air in batch and fed-batch cultivation.

The effects of increased air pressure in a culture of the thermophilic microorganism Thermus sp. RQ-1 were investigated. Cell growth dependence on oxygen supply was investigated in a fermenter at atmospheric pressure. Total oxygen depletion from the medium for low values of kLa was observed during the exponential growth phase. It was possible with this strain to enhance the oxygen transfer rate by increasing the air pressure. Cell productivity was improved by pressurisation up to 0.56 MPa for batch cultivation; and an induction of the antioxidant enzymes, superoxide dismutase and catalase, was observed with the rise in pressure. Cell pre-cultivation under pressurised conditions conferred to the cells more resistance to an exposure to hydrogen peroxide and more sensitivity to paraquat (methyl viologen). The usefulness of bioreactor pressurisation on the cultivation of Thermus sp. RQ-1 was demonstrated for fed-batch operation, with the attainment of higher cell densities. A two-fold increase in cell mass productivity was obtained by the use of hyperbaric air (0.5 MPa). With the pressurisation of the head-space in the reactor, it was also possible to eliminate the loss of liquid by evaporation, which amounted to more than 10% at 70 degrees C and atmospheric pressure.

Air Pressure↗