A simple,reliable rapid-mixing apparatus for continuous-flow studies

We have developed a simple and economical system for rapid mixing of solutions where a continuous-flow, chemically quenched mode of operation is appropriate. This has proved especially useful for studies of pyruvate dehydrogenase which produces a stable, enzyme-bound intermediate when the terminal acceptors are absent. It has also proved convenient for studies of the overall reaction in which fluorescence of pyridine nucleotide can be measured after quenching in alkaline solution.Syringes containing reactants are driven by a Harvard infusion pump, which provides sufficient speed and power (torque) to give good mixing with conventional commercially available mixing chambers and delay lines. Liquid chromatography fittings and valves are used for the switching operations necessary in the continuous-flow mode.     

A simple automatic dispensing apparatus

A simple dispenser using a 2-ml disposable syringe is described. The range of operation is 0.02–1.5 ml and an unusual accuracy is obtained by employing a new principle for dispensers: the dispensed volume is only a fraction of total tidal flow of fluid in the dispenser.     

The sucked-flow analyser: A simple apparatus for automatic determination of steady-state enzyme kinetics

The sucked-flow analyser is a modified stopped-flow apparatus for automatic measurements of initial rates of enzyme reactions at varying concentrations of substrate or inhibitor. The flow through the system is driven by a water suction pump and regulated by magnetic valves. Sample and reagent solution are aspired through tubes whose resistances to laminar flow determine a precise ratio of mixing in the observation cell. A minicomputer controls all operations, collects the data and calculates the results. Measurements on teh β-galactosidase and the cytochome P-450 reactions are presented.     

Bovine serum albumin-hemoglobin fractionation: significance of ultrafiltration system and feed solution characteristics

This work investigates the fractionation of similar molecular weight proteins bovine serum albumin (69 kD) and bovine hemoglobin (67 kD) by ultrafiltration. Three different membranes, viz. regenerated cellulose, poly(sulfone) and surface modified poly(acrylonitrile), each with a nominal molecular cutoff rating of 100 kD, were examined. The experiments were conducted in dead end, crossflow and vortex flow filtration modes and the separation was studied as a function of feed pH and ionic strength. Under similar system hydrodynamics, the surface modified poly(acrylonitrile) membrane displayed the highest resolution with minimum membrane fouling. The separation could be improved further by operating at low applied pressure (40 kPa) and high mass transfer (> 20 × 10^–6 m/s) in a vortex flow module. Under these conditions, the highest separation factor of 40 was obtained at the pI of hemoglobin.     

A simple apparatus for ultrafiltration of small volumes: application to the measurement of free and albumin-bound tryptophan in plasma.

An ultrafiltration apparatus which is cheap, easy to make, and simple to operate has been developed (patent pending) and assessed for the measurement of nonprotein-bound tryptophan concentration in blood plasma. Large batches of 200-μl samples can be rapidly ultrafiltered at controlled pH. The apparatus is of potentially wide applicability to protein-binding studies and to the determination of free and bound concentrations of drugs and other substances in plasma.     

A simple apparatus for measuring cell settling velocity

Accurate cell settling velocity determination is critical for perfusion culture using a gravity settler for cell retention. We have developed a simple apparatus (a settling column) for measuring settling velocity and have validated the procedure with 15-μm polystyrene particles with known physical properties. The measured settling velocity of the polystyrene particles is within 4% of the value obtained using the traditional Stokes' law approach. The settling velocities of three hybridoma cell lines were measured, resulting in up to twofold variation among cell lines, and the values decreased as the cell culture aged. The settling velocities of the nonviable cells were 33-50% less than the corresponding viable cells. The significant variation of settling velocities among cell populations and growth phases confirms the necessity of routine measurement of this property during long-term perfusion culture.     

A simple pressure filtration apparatus for field use

A simple apparatus for pressure-filtering water samples in the field is described. It is used in conjunction with the low pressure outlet of a standard regulator attached to an aqualung. The apparatus is useful in situations where electricity to run electric vacuum pumps is not available and is superior to conventional hand vacuum pumps.     

A simple,inexpensive apparatus for rotating bottles during zooplankton feeding experiments

By using the bearings in the hub of bicycle wheels to support the weight of jars containing zooplankton and experimental food, a small laboratory stirring motor can be used to slowly rotate several kilograms of jars for zooplankton feeding experiments. This apparatus is quickly assembled from easily obtainable parts at almost no cost.     

Evaluation of ultrafiltration cartridges for a water sampling apparatus

Aims:  To determine the efficiency of various ultrafiltration cartridges (UFC) in concentrating test micro-organisms from drinking water.
Methods and Results:  Replicate drinking water samples from three potable water supplies were dosed with Bacillus anthracis Sterne, Francisella tularensis LVS, Yersinia pestis CO92, bacteriophages MS2 and phi-X174, and Cryptosporidium parvum. The test micro-organisms were dosed together in 100 l of water, which was then recirculated through one of five different UFC until the retentate volume was reduced to c. 500 ml. The micro-organisms were assayed before and after ultrafiltration concentration and per cent recoveries were calculated. There were nine statistically significant differences among pairs of filters out of a possible 180 different combinations of UFC, test micro-organisms, and water types.
Conclusions:  No filter consistently performed better or worse than the others for each test micro-organism in all water samples tested.
Significance and Impact of the Study:  This study provides performance data on the ability of several different UFC to concentrate a panel of test micro-organisms from three sources of potable water. Water utilities and first responders may use these data when selecting UFC for use in emergency response protocols. This study also provides additional data as to the efficacy of ultrafiltration for recovering bacteria, virus-like particles, and protozoan oocysts from water samples.     

A simple and inexpensive apparatus for measuring fish metabolism

A simple, noninvasive, and economical home-made respirometer has been used to determine the standard metabolism of goldfish. The apparatus has been tested on several fishes and has proved its accuracy in determining a mass effect on standard metabolism. The apparatus can be made easily by middle school, high school, and undergraduate students and can be used to introduce them to basic concepts in animal physiology and in biological statistics.