J. A. Van Zyl

CHROMOSOME STUDIES IN 496 INFERTILE MALES WITH A SPERM COUNT BELOW 10 MILLION/ML

SummaryChromosome studies were performed on 106 men with azoospermia and 390 men with oligozoospermia (consistant sperm count below 10 million/ml). Constitutional chromosome abnormalities were found in 14.1% of the azoospermia group and in 5.1% of the oligozoospermia group. An overall incidence of 7.1% constitutional abnormalities indicates that this criterion of selection may be advisable for routine chromosome analysis of infertile men. A reduction of 25% in the workload increases the yield of chromosome abnormalities in the group of infertile men to 10–14 times above that expected in the normal population.

Myxofibroma of the jaws

Abstract The clinical, radiographic and histological features of a large unilateral myxofibroma of the maxilla are described. The literature pertaining to myxofibroma is reviewed.

Chondrosarcoma of the mandibular condyle. Report of a case with special reference to radiographic features

A case of chondrosarcoma of the mandibular condyle is described. With carefully taken tomographs, a diagnosis of chondrosarcoma of the mandibular condyle can be made with some degree of certainty, on radiological evidence alone. Chondrosarcomata of the mandibular condyle may manifest with the typical symptoms of the temporomandibular joint dysfunction syndrome. Tumours of the condyle can reach a large size without producing clinically obvious swellings. The literature pertaining to chondrosarcoma of the mandibular condyle is reviewed.

Oligozoospermia : recent prognosis and the outcome of 73 pregnancies in oligozoospermic couples

The minimum value for each of the five main semen parameters, below which conception rarely occurred or did not occur at all, was calculated in a group of 1884 couples complaining of primary and secondary infertility: 304 conceptions including first as well as consecutive conceptions, occurred. The parameters evaluated were (minimum value calculated in this study between brackets) volume (1.0 ml), sperm count ml−1 (2.0 million), total sperm count (4.0 million), motility (10%), forward progression (2.0 MacLeod units: scale 1–4) and normal sperm morphology (3%). The pregnancy rate in the group of 308 oligozoospermic men and the minimum value of semen parameters were the cornerstones in determining the prognosis for oligozoospermic patients. A sperm count of >2.0 million ml−1 was considered relatively adequate for eventual conception judged by the 68 of 308 (22.1%) pregnancies that occurred among oligozoospermic men in this study, provided that the other five semen parameters showed values above the minimum value. In cases where the average sperm count was <2 million ml−1, the chances for conception became rare, viz five of 308 (1.6%). The total number of pregnancies in the group classified as oligozoospermic was 73 (23.7%). With these pregnancies there was no increase in the rate of foetal wastage and congenital abnormalities. Abortion occurred in 15.09% and ectopic pregnancy in 0.9% among first and consecutive pregnancies. One infant among the 56% boys and 44% girls was born with congenital abnormalities. Most of these infants had a normal birth mass of >2500 g.

Prediction of seismic events in mines using neural networks

A number of fatalities and accidents in hard-rock mining could be avoided if rockbursts could be predicted accurately. Until recently, this goal was elusive because seismicity could not be measured accurately. Recent advances in monitoring technology have improved the accuracy of seismic source parameter measurements. This creates the possibility of modelling the rock dynamics, thus allowing prediction of seismic events. This paper investigates the use of neural networks for modelling seismic time series in hard-rock mines.

Prior knowledge for fuzzy knowledge-based artificial neural networks from fuzzy set covering

Prior knowledge in a symbolic form can serve to initialize a knowledge-based neural network. We present a method for encoding fuzzy classification rules derived from a machine learning algorithm based on a fuzzy set covering framework. The inductive-bias of the encoding can be adjusted to allow further rule refinement and acquisition. We investigate the effect of these parameters, and show that the classification results correspond exactly to the prior knowledge.

Impact of unfortified human milk feeding on weight gain and mineral status of very-low-birth-weight infants after discharge from a kangaroo mother care unit

Kangaroo mother care (KMC) and human milk feeding have significantly improved the neonatal survival of very- low-birth-weight infants in developing countries (Lincetto et al. 2000). These infants are discharged at low weights (1,800 g) and receiving only human milk, a multivitamin, and iron syrup. There is concern regarding the long-term effects of feeding these infants unfortified human milk. We hypothesized that the low caloric and low phosphorous content of human milk will result in hypophosphatemia and poor weight gain after discharge. The aim of our study was to determine the milk feeding pattern, weight gain, and calcium and phosphorous levels at 6 and 12 weeks corrected age of infants with birth weights > 1,600 g who received intermittent KMC and whose mothers actively were encouraged to breastfeed during the hospitalization period.