Reproducibility of multistage graded exercise testing in patients with chronic stable angina.

Exercise testing is widely used for the diagnosis of ischaemic heart disease and for the evaluation of antianginal drugs. To assess reproducibility, analysis was carried out on 128 paired graded exercise tests from 103 patients performed at the same time of day and under identical conditions. Six different parameters were evaluated and compared between the basal test (no treatment) and the placebo test. During the basal period the mean (+/- SEM) exercise time to the development of angina was 6.0 (+/- 0.2) min and the 1 mm ST depression time was 4.1 (+/- 0.2) min. After 2 weeks of placebo the exercise time was 6.1 (+/- 0.2) min (P = NS) and the 1 mm ST depression time was 4.2 (+/- 0.2) min (P = NS). There was no significant difference between the resting or maximum heart rate on either test and the maximum ST segment depression (leads CM5 and CC5) was unaltered. In a second group of 17 patients where the basal tests were performed in the afternoon and the placebo tests in the morning, heart rate and ST segment were found to be reproducible but there was a significant difference in exercise time: 5.7 (+/- 0.7) min for the basal test and 8.3 (+/- 0.5) min for the placebo test (P less than 0.001); and of the 1 mm ST depression time: 2.7 (+/- 0.4) min for the basal test, and 5.4 (+/- 0.5) min for the placebo test (P less than 0.001). We conclude that exercise tests done under standardised conditions in the morning are highly reproducible in patients with chronic stable angina and therefore provide a valuable test for the evaluation of antianginal drugs.

BOD5 estimation for pulp and paper mill effluent using UV absorbance.

A novel method based on UV absorbance, is presented for estimating the BOD5 in pulp and paper mill effluent. This method could eventually be incorporated into an on-line sensor for BOD5 that is suitable for process control applications. Two streams, the reactor entrance and the final effluent, from two different mills were studied. One mill employed the Kraft pulping process, while the second mill was a thermo-mechanical one. The absorbance over the range 200-350 nm showed significant differences between the two mills. Because the two mills use very distinct processes, separate correlations were used to relate the absorbance to the BOD5 for both the mills. Results indicate that prediction of reactor entrance BOD5 was reasonable, whereas prediction of final effluent BOD5 was inaccurate, for both mills. Also studied was the effect of aeration on BOD5 results obtained at low BOD5 values for the Kraft mill.

Acute and chronic effects of nicardipine on systolic and diastolic left ventricular performance in patients with heart failure: a pilot study.

Nicardipine is a new calcium ion antagonist with vasodilating properties which has been shown to be effective in the treatment of hypertension and angina. We have studied its effect on systolic and diastolic left ventricular function in patients with mild to moderate degrees of congestive heart failure. Ten male patients with New York Heart Association Class II and III heart failure underwent acute treatment with an intravenous infusion of nicardipine (10 mg over 10 minutes). A nuclear probe was used to monitor left ventricular ejection fraction, peak filling rate, and relative cardiac output. Blood pressure and heart rate were also measured. The blood pressure (mean +/- SD) fell from 133 +/- 26/86 +/- 11 mmHg to 103 +/- 22/69 +/- 13; the heart rate rose from 67 +/- 9 beats/min to 85 +/- 10; left ventricular ejection fraction from 31 +/- 7 to 38 +/- 6%; relative cardiac output from 24 +/- 9 to 41 +/- 11; peak filling rate from 1.18 +/- 0.4 end-diastolic volume per second to 1.82 +/- 0.4 (p less than 0.001 in all cases) at the end of infusion. After 4 weeks of chronic treatment in eight patients (20 mg to be taken three times daily (tds) in one and 40 mg tds in 7), the blood pressure and heart rate had returned to baseline values but the improvements in left ventricular ejection fraction, relative cardiac output, and peak filling rate were sustained; this was associated with functional improvement in all 8 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Comments on the communication: on the calculation of shear rate and apparent viscosity in airlift and bubble column bioreactors.

The determination of the shear rate in bubble column and airlift bioreactors is an important question from both the perspective of cell damage and the correlation of hydrodynamic parameters in non-Newtonian fluids in these contractors. In the context of correlating hydrodynamic parameters in non-Newtonian fluids, a common approach involves assuming that there exists an average shear rate in the column that is proportional to the superficial gas velocity. This average shear rate is then used to evaluate an effective viscosity of the non-Newtonian fluid that is subsequently used to quantify the fluid's rheological behavior in correlation. Contrary to a recent communication, this report illustrates that this approach, which has mainly been applied to bubble columns, can also be applied to external loop airlift contractors, replacing the superficial gas velocity by the superficial gas velocity by the superficial gas velocity supplied to the riser of the contractor. This extension is based upon consideration of the relevant characteristic velocity in the active zone (i.e., the riser section) of the reactor.

Enhanced disruption of Candida utilis using enzymatic pretreatment and high-pressure homogenization.

The enhancement of the overall disruption of a native strain of Candida utilis (ATCC 9226) was studied using a combination of two methods, namely, pretreatment in the form of partial enzymatic lysis by Zymolyase followed by mechanical disruption in a Microfluidizer high-pressure homogenizer. The cells were grown in both batch and continuous cultures to examine the effect of specific growth rate on disruption. Cell suspensions ranging in concentration from 7 to 120 g DW/L were disrupted with and without enzymatic pretreatment. For yeast grown in batch culture, final total disruption obtained using the combined protocol approached 95% with four passes at a pressure of 95 MPa, as compared with only 65% disruption using only mechanical homogenization. A modified model was developed to predict the fraction disrupted by the enzymatic pretreatment-mechanical homogenization two-stage process. Predicted disruptions agreed favorably with experimental observations (maximum deviation of 20%) over a wide range of operating conditions. (c) 1994 John Wiley & Sons, Inc.

Hydrodynamics and mass transfer in Aspergillus niger fermentations in bubble column and loop bioreactors.

The influence of Aspergillus niger broth rheology, bioreactor geometry, and superficial gas velocity on the volumetric liquid phase oxygen transfer coefficient (k(L)a(L)), riser gas holdup (epsilon(GR)), and circulating liquid velocity (u(LR)) was studied in a bubble column (BC) and two external-circulation-loop airlift (ECLAL) bioreactors. The results are compared to those of previous studies on homogeneous fluids and in particular with a recent study on non-Newtonian carboxymethylcellulose (CMC) solutions conducted in the same contactors used for the A. niger fermentations. As expected from the CMC-based studies, in the heterogeneous broths of A. niger epsilon(GR), k(L)a(L), and u(LR) decreased with increasing broth apparent viscosity; epsilon(GR) and k(L)a(L) decreased with increasing downcomer-to-riser cross-sectional area ratio, A(d)/A(r), whereas u(LR) increased with increasing A(d)/A(r). Gas holdup data in the airlift fermentations of A. niger were well predicted by the CMC-based correlation. However, the CMC-based correlations produced conservative estimations of k(L)a(L) and overestimates of u(LR) compared to the observed values in the A. niger broths.

External-circulation-loop airlift bioreactors: study of the liquid circulating velocity in highly viscous non-Newtonian liquids.

In order to obtain further information on the behavior and optimal design of external-circulation-loop airlift (ECL-AL) bioreactors, the liquid circulating velocity, gas holdup and average bubble diameter in the downcomer were studied using highly viscous pseudoplastic solutions of various types of CMC. A few comparative measurements also were made using a viscous Newtonian aqueous sucrose solution. For the liquid velocity measurements, an ultrasonic flow meter (Doppler frequency shift principle) was applied for the first time to the gas/non-Newtonian liquid dispersion in downward flow and satisfactory results were obtained. For viscous liquids, the circulating liquid velocity in the riser section of an ECL-AL (u(LR)) is shown to be dependent mainly on the downcomer-to-riser cross-sectional area ratio (A(d)/A(r)), the effective viscosity (eta(eff)) and the gas superficial velocity (u(GR)) as described by the following equation uLR = 0.23uGR0.32 (Ad /Ar)0.97 eta(eff)- 0.39. The circulating liquid velocity exerts opposing effects on the mass transfer and liquid-phase mixing performances of ECL-AL fermentors. Therefore, it is proposed that the optimum operating conditions for a given fermentation may be best achieved by means of independently regulating the circulating liquid velocity.

Chemical and enzymic pretreatment of corn stover to produce soluble fermentation substrates.

Corn stover was pretreated with various chemical agents, including sodium hydroxide, sulfuric acid, ethylenediamine, n-butylamine (either alone or in solution with methanol), and acetonitrile or ethanol containing hydrochloric acid. Of these chemicals, n-butylamine was the best reagent for pretreatment of corn stover, considering the degree of loss of total carbohydrate, delignification, cumulative weight loss, cumulative yield of reducing sugars per original total carbohydrate, and the potential ease of recovery and reuse of reagent. In comparison to the other reagents tested, n-butylamine (n-BA) selectively delignified corn stover. The best conditions were as follows: a 12-h presoak of about a 155 g dry wt/L slurry (1 mm average particle size) in 100% n-BA at room temperature, followed by 30 min of refluxing (86.5 degrees C) with 40% (w/w) n-BA-distilled water solution. The cumulative yield of reducing sugars after enzymic hydrolysis was 44.5% of the original total carbohydrate and the cumulative total weight loss (dry basis) was 59%. Degradative loss of total carbohydrate during pretreatment was not detected.

Gas holdup and overall volumetric oxygen transfer coefficient in airlift contactors.

The two major types of airlift contactors, concentric-tube and external-loop, were investigated for their gas holdup (riser and downcomer) and overall mass transfer characteristics. Results obtained in batch charges of tap water and 0.15 kmol/m(3) NaCl solution are reported for external-loop airlift contactors having downcomer-to-riser cross-sectional area ratios, A(d)/A(r), ranging from 0.11

Review: optimizing inducer and culture conditions for expression of foreign proteins under the control of the lac promoter.

This review examines factors which influence the expression of foreign proteins in Escherichia coli under the transcriptional control of the lac and tac promoters, and discusses conditions for maximizing the production of a foreign protein using this system. Specifically, the influence of IPTG (isopropyl-beta-D-thiogalactoside) concentration, temperature, composition of the growth medium, the point in the growth curve at which cells are induced with either IPTG or lactose, and the duration of the induction phase are discussed.

Disruption of native and recombinant Escherichia coli in a high-pressure homogenizer.

The disruption of native and recombinant strains of Escherichia coli was studied using a high-pressure homogenizer (Microfluidizer). The cells were grown in both batch and continuous fermentations. Cell suspensions ranging from 4 to 175 g dry wt/L were investigated at disruption pressures ranging from 30-95 MPa and at up to five passes. For both types of cells, the fraction of cells disrupted was dependent on the growth rate and concentration of the cells, the disruption pressure, and the number of passes through the disruptor. A model is presented that correlates the fractional disruption with these operating variables. The recombinant strain disrupted more readily than the native strain; 95 to 98% disruption of the former was achieved in two to three passes at a pressure of 95 MPa.

Induction of T4 DNA ligase in a recombinant strain of Escherichia coli.

The kinetics of cell growth and foreign protein production, as well as factors affecting protein stability, were studied and optimized in batch and fed-batch fermentations of a recombinant strain of Escherichia coli. The pL promoter from bacteriophage lambda under the control of a temperature-sensitive cl represser, with the entire construct integrated into the E. coli chromosome through the use of a defective bacteriophage lambda lysogen, was used to direct the synthesis of T4 DNA ligase. The biphasic fermentations consisted of a primary growth phase at 30 degrees C followed by an induction phase which was initiated by shifting the temperature to 42 degrees C. In the fed-batch fermentations, additional nutrients were added at the time of initiating induction. Maintenance of sufficiently high concentrations of the organic substrates (glucose and casamino acids) during the induction phase was required for continued cell growth at 42 degrees C. Such growth was essential for T4 DNA ligase formation and in vivo stability. Hence, fed-batch fermentations produced the highest yield of the foreign protein Commensurate with providing lower total amounts of substrates. In such cases, high cell densities (6 g dry wt/L) with substantial intracellular levels of T4 DNA ligase (4.6% total cellular protein, or 2.7% of the dry biomass) were achieved.

Evaluation of organosolv processes for the fractionation and modification of corn stover for bioconversion.

Corn stover was pretreated for compositional fractionation and structural modification for maximum conversion of carbohydrate to soluble sugars. The process scheme consisted of three steps: (1) mild prehydrolysis in dilute sulfuric acid, (2) delignification with various organosolv solvents, and (3) enzymatic hydrolysis in an agitated bead reactor. Prehydrolysis of corn stover can be achieved at temperatures ranging from 95 to 120 degrees C, which is a much milder condition than must be applied to wood. Various organosolv solvents, including several alcohols with acid as catalyst, ethylene glycol, and its derivatives, and amines were used for delignification of the prehydrolyzed corn stover. Aromatic alcohols were found to be more effective in solubilizing the prehydrolyzed corn stover than were the aliphatic alcohols. Butanol was the most effective among the aliphatic alcohols; on the other hand, phenol was the best among the aromatic alcohols. Ethylene glycol, methylcellosolv, and ethylcellosolv were effective in solubilizing the prehydrolyzed corn stover but not for enhancing the enzymatic hydrolysis. Various amines achieved delignification at the mild temperature of 95 degrees C, but they tended to solubilize substantial amounts of carbohydrate in addition to lignin. n-Butylamine was effective in enhancing the conversion during enzymatic hydrolysis; it was a good delignifying agent as well as one that achieved a concomitant swelling of the cellulose structure. The low enzymic conversion (20-37%) of prehydrolyzed and solvent-extracted corn stover that was achieved implies that lignin is not the only major barrier for enzymatic hydrolysis. Modification of cellulose structure also should be accomplished to achieve a high degree of conversion. Enzymatic hydrolysis in the agitated bead system increased the rate and extent of conversion of corn stover substantially compared to systems without beads.

Effect of temperature on the inhibition kinetics of phenol biodegradation by Pseudomonas putida Q5.

The temperature-dependent performance of mixed-culture wastewater treatment processes may be strongly influenced by their content of psychrotrophic bacteria. In this work, the effect of temperature on cell growth and phenol biodegradation kinetics of the psychrotrophic bacterium Pseudomonas putida Q5 were determined using both batch and continuous cultures in the range of 10-25 degrees C. The Haldane equation was found to be the most suitable substrate-inhibition model for the specific growth rate. The Haldane parameters mu(max) and K(I) were best modeled by a square-root dependency on temperature. However, the Arrhenius model provided a better prediction of the temperature dependence of K(S). The variation of the yield constant with temperature also was studied experimentally. Comparisons with results of previous workers are presented.

Optimizing the expression of a monoclonal antibody fragment under the transcriptional control of the Escherichia coli lac promoter.

The expression of a monoclonal antibody Fab fragment in Escherichia coli strain RB791/pComb3, induced with either lactose or isopropyl-beta-D-thiogalactoside (IPTG), was compared to determine if lactose might provide an inexpensive alternative to induction with IPTG. Induction of Fab expression imposed a metabolic load on the recombinant cells, resulting in lower final cell yields compared to the non-induced controls. An IPTG concentration of 0.05 mM was sufficient to achieve maximal expression of soluble Fab protein when inducing in the early-, mid-, or late-log phases of batch cultures grown using either glucose or glycerol as a carbon source. The largest overall yield of Fab fragments when using 0.05 mM IPTG was achieved by increasing the final yield of cells through glycerol feeding following induction in late-log phase. Lactose was as effective as IPTG for inducing Fab expression in E. coli RB791/pComb3. The greatest overall level of Fab expression was found when cells grown on glycerol were induced with 2 g/L lactose in late-log phase. Since the cost of 0.05 mM of IPTG is significantly greater than the cost of 2 g/L lactose, lactose provides an inexpensive alternative to IPTG for inducing the expression of Fab fragments, and possibly other recombinant proteins, from the E. coli lac promoter.

Growth of Chaetomium cellulolyticum on Alkali-Pretreated Hardwood Sawdust Solids and Pretreatment Liquor.

The treatment of a hardwood sawdust with 1% NaOH solution at 121 degrees C dissolved 19.7% of the dry matter, mainly hemicellulose and lignin. Fermentation of the treated solids by Chaetomium cellulolyticum for 48 h gave a product containing 12.5% crude protein (total N x 6.25) on a dry weight basis. The in vitro rumen digestibility of the 48-h fermentation product was 30%, compared to 24% for the alkali-treated but unfermented sawdust. Growth was independent of sawdust particle size in the range 40 to 100 mesh. Fermentation of the pretreatment liquor gave a product containing up to 50% crude protein (dry weight basis) with an in vitro rumen digestibility of 65 to 76%. Approximately 6.7 g of crude protein was obtained from the treated solids and 2.2 g from the pretreatment liquor per 100 g of sawdust treated. The product from the pretreatment liquor fermentation has potential as a high-protein animal feed supplement but could not be produced economically without an outlet for the relatively indigestible product from the solids fermentation. Growth on the pretreatment liquor was strongly pH dependent; there was a considerable increase in the lag phase when the pH was lowered from 7.5 to 5.2. This effect appears to be due to an inhibitor whose toxicity is reduced at high pH.

Tiapamil, a new calcium channel blocking agent for the treatment of effort induced chronic stable angina pectoris.

The anti-anginal efficacy of tiapamil, a new calcium channel blocking agent was studied in 24 patients with established effort induced chronic stable angina pectoris. The patients were allocated randomly in a double-blind fashion to tiapamil 300 mg thrice daily or placebo for 2 weeks and thereafter all the patients received tiapamil 300 mg thrice daily in a single-blind fashion for a further 2 weeks. All patients performed symptom limited multistage graded exercise testing with computer-assisted analysis of the electrocardiogram before entering the study and at the end of the double-blind and single-blind phases. The mean exercise time to develop angina during the control test in the group which received placebo during the double-blind phase was 7.1 min; this increased to 8.5 min after 2 weeks of placebo and 9.7 min after 2 weeks of subsequent tiapamil therapy. Similarly in the group which received tiapamil during the double-blind phase the mean exercise time on control test was 6.4 min, increasing to 9.7 min and 9.7 min after 2 and 4 weeks of tiapamil therapy respectively. There were no statistical significant differences between the changes from control, seen with tiapamil and placebo during the double-blind phase. However, the changes observed between control and active therapy in the tiapamil group did reach statistical significance (p = 0.003). Similarly, 1 mm ST-segment depression time was prolonged by tiapamil therapy. The heart rate at rest and maximal exercise remained unaltered with tiapamil therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Double inhibition model for degradation of phenol by Pseudomonas putida Q5.

A semiempirical model, based on the presence of an inhibitory intermediate metabolite excreted to the broth, was developed to better predict the dynamic responses to shock loadings of Pseudomonas putida Q5 degrading phenol. Compared to the Haldane equation, the new model exhibited better prediction capabilities for a broad range of inlet concentration and dilution rate step changes. The experiments were performed at 10 degrees and 25 degrees C and ranged from stable responses to washouts. The time delays observed experimentally were successfully predicted with the dual-inhibition model and a very good agreement with the observed phenol profile also was found in a pulse experiment. A possible intermediate metabolite was detected by HPLC analyses based on the high correlation shown with the predicted inhibitory intermediate metabolite in the model.