Efficient purification of PCR products using ultrafiltration.

The use of disposable ultrafiltration devices for the purification of PCR-amplified DNA products from the other components of the reaction mixture is outlined. The advantages of using a 100,000 molecular weight cutoff membrane are discussed. The integrity of the membrane-purified DNA is checked by its successful use in sequencing, ligation and cloning procedures.

A new microporous membrane for diagnostic immunoassays.

A family of new microporous composite membranes that do not require post-immobilization blocking or quenching steps has been developed for diagnostic immunoassay applications. These membranes, Autobloc membranes, are shown to have low nonspecific binding of proteins. Immobilization of antibody or antigen to the membrane can be achieved either by covalent binding or by adsorption. The correlation between the initial immobilization capacity for IgG and the effective immobilization capacity of microporous membranes is discussed. The performance of Autobloc membranes is demonstrated by dot-enzyme-linked immunoassays in the flow-through mode with several commonly used enzyme-substrate systems and compared to the performance of other membranes. The advantages of using Autobloc membranes are suggested.

Transducer offset by electrocautery resulting in erroneous blood pressure measurement.

During a coronary artery bypass operation arterial blood pressure measured with a Bentley Trantec model 800 transducer increased erroneously while continuous electrocautery was being used. This phenomenon has recurred infrequently, with fictitious hypotension being observed in one patient. To reproduce the problem of pressure offset during electrosurgery a bench test demonstrated that with peak to peak voltage of 20 volts from the electrosurgical unit, three of seven Bentley transducers had offsets as much as +/- 50 mmHg. It is important for anaesthetists to determine if electrosurgery units are functioning before treating apparent pressure drifts.

A simple method for analysis of DNA histograms in human myeloid cells perturbed by stimulators of DNA synthesis.

In the past, phase fractionation has been used as a determinate of the level of stimulation of cells perturbed by stimulators and inhibitors of DNA synthesis. This method has, in our hands, proven to be insensitive and unreliable with human myeloid cells. A new method of analysis is described in this paper which involves utilization of the magnitude of the slope of a line fit to the mid-portion of S phase as an index of the level of stimulation of cultured human myeloid cells. This method is fast, reliable and simple to implement on an inexpensive microcomputer.

On-line microcomputer system for analysis of precordial maps.

An inexpensive system was developed for automated on-line analysis of ST segment heights, Q, R, and S heights and areas under these peaks, using an LSI-11 microcomputer. System accuracy was evaluated using a computer graphics technique which enabled magnification and labelling of the computed peaks on 60 maps from 17 patients. To compare the computer with hand analysis, the sigma ST (.06 seconds from S nadir) for 20 maps was calculated by three blinded observers. Correct computer evaluation occurred in all but five of 2058 leads. The mean observer sigma ST was 3.2 millivolts (range 0.77-7.5 mv). Mean inter-observer SD was +/-0.21 mv. The mean computer sigma ST was 3.5 mv (range 0.82-9.3 mv). The spread between computer and observer was +/-0.45 mv. Discrepancies between computer and observer were due to cumulative imprecision in observer measurements. This system has proven to be a practical and economic solution to handling the large volume of data accumulated with serial precordial mapping. It is considerably more precise than conventional hand analysis. Additionally, the system's versatility makes it ideally suited to many clinical and research functions.