Multisample parallel array fraction collector: application in DNA alkaline elution studies.

A fraction collector designed specifically to be compatible with the analytical techniques of alkaline and neutral elution of DNA from carcinogen-treated cells is described. This apparatus, which is operated by microchip controls, permits simultaneous collection of as many as 20 eluted samples directly into standard- or small-size scintillation vials contained in manufacturer's shipping cartons. This instrument saves operator time, offers considerable flexibility, and has several fail-safe features.

Analytical techniques for cell fractions. XXIII. A stable thermal gradient device for heat denaturation studies on proteins.

The ISO-DALT two-dimensional electrophoretic system (1,2), based on the method of O'Farrell (3), is capable of performing large numbers of analysis on complex mixtures of proteins. However, both separations employed are carried out under dissociating or denaturing conditions and no enzyme activities are readily observable in the analyzed proteins. In order to identify the spots corresponding to particular enzymes, it is therefore necessary to employ some nondestructive resolving technique first and as a second step to perform both enzyme and two-dimensional electrophoretic analyses on the fractions generated. By correlating enzyme activity with intensity of various spots on the two-dimensional gels throughout the series of initial fractions, identifications, can be made. This approach, unlike the more direct immunoprecipitation methods (4), requires the running of large numbers of enzyme analyses and two-dimensional gels and some convenient initial resolving procedure. Convenient and rapid techniques for the analyses (5,6) and gels (1,2) have been described previously in this series and elsewhere. This paper deals with the use of selective denaturation in a temperature gradient as an initial resolving procedure and describes a simple thermal gradient device for generating such a gradient.

Improved temperature control of the Technicon tissue processor paraffin bath.

Modifications of the Auto-Technicon Tissue Processor Paraffin Bath are described. The modification are a combination of electrical and mechanical changes that will ensure long-term reliability of the unit and dependable temperature maintenance of the paraffin. Extensive testing has verified that modified units are able to stabilize temperature within a range of 0.25C over many months of continuous operation.

Dual channel temperature recorder.

A dual channel temperature recorder is described which can measure temperatures linearly over a range of 0 to 80 C. The sensitivity can be adjusted so that any temperature span, as small as 3 degrees , will cover recorder full scale, and temperatures can be read to 0.1 degrees . The recorder provides two independent, permanent records of temperature variations which can be related directly to the time of day.

High-intensity vapor lamp for biological research.

A vapor arc light source has been adapted to the study of the lethal action on bacteria of near-ultraviolet (UV) and visible light. Its use makes possible much shorter exposure times than could be obtained from previously available sources. The output of radiant energy is sufficient to provide a fairly detailed action spectrum for lethality in the long-UV and visible region without the addition of exogenous sensitizers. Populations of cells of Escherichia coli WP2 were inactivated through five log(10) cycles with light at 460 nm. Significant inactivation also was obtained with light at 550 and 650 nm.

Automated continuous culture of mammalian cells in suspension.

A system has been developed for the continuous culture of mammalian cells in suspension. The system maintains constant cell concentrations (monitored as the degree of light scattering) over a wide range of previously selected values by automatic additions of known amounts of medium and simultaneous withdrawals of equal volumes of cell suspension.

Electronically controlled continuous culture device.

A photocell-controlled continuous culture device, a Nephelostat, is described that maintains a wide variety of cultures of microorganisms in balanced growth. This Nephelostat controls concentrations of bacteria within +/-3% over a cell concentration range of 10(6) to 10(9) cells per ml. Growth rates are recorded so that changes in the growth rate are observed over small increments of time. Spontaneous and caffeine-induced mutation rates of two strains of Escherichia coli were compared under Nephelostat and chemostat conditions.

Automatic sample collector for continuous cultures.

An automatic sample collector is described that samples growing cultures sequentially. It can be programmed to collect at preselected intervals (usually several hours apart) for a prescribed period (usually from minutes to hours). Samples are collected serially but during intermediate time periods; when the sample is not required, it is disposed of by diverting it into a discard reservoir. This device collects culture samples on a predetermined schedule and stores them under refrigeration for study at a later time.