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Biomedical subjects

A J Simons

Publications and source records attributed to A J Simons.

33 records · Page 2Linked to original sources
PubMed1992

Detection of genetic variation between and within populations of Gliricidia sepium and G. maculata using RAPD markers.

Gliricidia sepium and G. maculata are multi-purpose leguminous trees native to Central America and Mexico. Research programmes have been initiated to define the native distribution of Gliricidia and sample the spectrum of genetic variation. To date, there has been little systematic assessment of genetic variability in multi-purpose tree species. Accurate estimates of diversity between- and within-populations are considered a prerequisite for the optimization of sampling and breeding strategies. We have used a PCR-based polymorphic assay procedure (RAPDs) to monitor genetic variability in Gliricidia. Extensive genetic variability was detected between species and the variability was partitioned into between- and within-population components. On average, most (60 per cent) of the variation occurs between G. sepium populations but oligonucleotide primers differed in their capacity to detect variability between and within populations. Population-specific genetic markers were identified. RAPDs provide a cost-effective method for the precise and routine evaluation of variability and may be used to identify areas of maximum diversity. The approaches outlined have general applicability to a range of organisms and are discussed in relation to the exploitation of multi-purpose tree species of the tropics.

Americas↗
PubMed1984

Processing of the electroencephalogram in cardiac surgery.

The objective of this investigation was to find a method to automatically detect several types of abnormal EEG patterns which occurred during cardiac surgery. The EEGs were analyzed by means of several EEG processing and pattern recognition methods. It was found that a good classification into normal and abnormal EEG patterns was generally obtained if only two EEG features were used. The results of this investigation are of importance for implementing into a computer-based monitoring system for use during cardiac surgery.

Adult↗
PubMed1982

[Electroencephalographic findings during open heart surgery. Automatic analysis in relation to parameters of anesthesia and use in intraoperative monitoring of cerebral function].

It is generally agreed upon by experts that EEG monitoring of brain function during open heart surgery is of the utmost importance in preventing postoperative neurological and psychopathological consequences. Up to now, however, this monitoring has not been performed on a large scale: (1) it is a very time-consuming task for the clinical neurophysiologist: (2) the anesthetist does not generally possess enough knowledge of this part of neurophysiology to get more than only a rough impression of the alterations of brain function during these procedures. To improve this situation we developed an automatic method to monitor brain function: the results of period-amplitude analysis of the EEG are continuously related to a number of important parameters--blood pressure, temperature, anesthesia. The way this is done resembles to a large degree the procedure which the neurophysiologist uses to judge the EEG during monitoring. The system generates warning and alerting signals, which also indicate the kind of disturbance when a marginal situation occurs. The anesthetist may take measures within 1 min to restore the condition. This is in complete agreement with the needs of anesthesiology. By means of a special function keyboard the anesthetist uses the system interactively and introduces all the necessary information which is needed for the proper functioning of the warning system (kind and quantity of different anesthetics and other drugs). At the end of the procedure the total information about the EEG, patient parameters and anesthetic measures are plotted in graphical form and printed as a table for documentation purposes which to a large degree may do away with the usual documentation. The introduction of this automatic monitoring system opens the way to a large scale use of EEG monitoring during open heart surgery.

Anesthesia, General↗
PubMed1980

Measurement of rise time of averaged muscle action potential in normal subjects and patients with myopathy.

As a result of diminution of the number of muscle fibers in patients with myopathy, the rise time of the fast negative phase of the spike potentials in the EMG becomes shorter. By using a small special purpose computer (averager) a mean action potential is obtained from which the rise time of the "spike" is determined. In normal muscles the mean value is 509 microseconds (SD 118). Myopathic muscles show a mean value of 225 microseconds (SD 76). There is a slight overlap and uncertainty between 280 and 370 microseconds. Because of the short time needed to examine the muscle for this parameter many muscles may be examined during one routine EMG.

Electromyography↗
PubMedDate not supplied

Intra-abdominal abscesses following laparoscopic and open appendectomies.

Recent findings in a small number of studies have suggested a trend toward increased infectious complications following laparoscopic appendectomy. The purpose of the present review was to evaluate the incidence of postappendectomy intra-abdominal abscess formation following laparoscopic and open appendectomies. Using the surgical database of the Los Angeles County-University of Southern California Medical Center, we reviewed the records of all appendectomies performed at the center between March 1993 and September 1995. Incidental appendectomies as well as appendectomies in pediatric patients under the age of 18 years were excluded. A total of 2497 appendectomies were identified; indications for these procedures included acute appendicitis in 1422 cases (57%), gangrenous appendicitis in 289 (12%), and perforated appendicitis in 786 (31%). The intraoperative diagnosis made by the surgeon was used for classification. A two-tailed P value of <0.05 was considered significant. There was no significant difference in the rate of abscess formation between the groups undergoing open and laparoscopic appendectomies for acute and gangrenous appendicitis. In patients with perforated appendicitis, a total of 26 postappendectomy intra-abdominal abscesses occurred following 786 appendectomies for an overall abscess formation rate of 3.3%. Eighteen abscesses occurred following 683 open appendectomies (2.6%), six abscesses occurred following 67 laparoscopic appendectomies (9.0%), and the remaining two abscesses occurred following 36 converted cases (5.6%). For perforated appendicitis, however, there was a statistically significant increase in the rate of abscess formation following laparoscopic appendectomy compared to conventional open appendectomy (9.0% vs. 2.6%, P = 0.015). There was no significant difference in the rate of abscess formation between open vs. converted cases or between laparoscopic vs. converted cases. A comparison of the length of the postoperative hospital stay showed no significant difference between open and laparoscopic appendectomy for perforated appendicitis (6.1 days vs. 5.9 days). Laparoscopic appendectomy for perforated appendicitis is associated with a higher rate of postoperative intra-abdominal abscess formation without the benefit of a shortened hospital stay. Given these findings, laparoscopic appendectomy is not recommended in patients with perforated appendicitis.

Abdominal Abscess↗