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Biomedical subjects

M Westergaard

Publications and source records attributed to M Westergaard.

8 recordsLinked to original sources

[Fetal chylothorax].

Foetal chylothorax was diagnosed in female foetus by ultrasound scanning on account of suspected twin pregnancy at the 34th week. No other signs of hydrops foetalis were found. The chylothorax reformed rapidly following intrauterine thoracocentesis which was therefore repeated immediately before Cesarean section at the 38th week in order to facilitate the perinatal cardiopulmonary adjustment. Pulmonary maturation was found to be normal. Postnatally, marked chylous effusion in the pleural cavity continued. Conservative treatment with pleural drainage and total parenteral nutrition was attempted initially. On account of the absence of response and supervening infection, it was decided to operate after the elapse of three weeks. Pleural decortication was performed with good result.

Adult

Presynaptic events in meiocytes of Lilium longiflorum and their relation to crossing-over: a preselection hypothesis.

We are proposing a "Preselection Hypothesis" to account for the regulation of crossing-over in eukaryotic organisms. The hypothesis characterized meiosis in terms of three major physiological stages: (1) a presynaptic stage when pairs of homologous DNA stretches are selected so as to become trapped within the synaptinemal complex during synapsis, (2) an alignment of homologous chromosomes and stabilization of paired bivalents via the synaptinemal complex, and (3) a scission and rejoining of DNA stretches leading to the formation of chiasmata and crossovers. The hypothesis centers on the first stage and is based on evidence for the occurrence of significant cytological and biochemical changes prior to synapsis. The major feature of the hypothesis is that crossing-over occurs only in trapped DNA stretches. Thus, potential crossing-over sites, though not crossing-over itself, are determined well before chromosomes pair. Since, to a large degree, crossovers are distributed randomly along the length of each chromosome, the preselection process must result in a random assortment of trapped DNA stretches, the assortment differing from one meiocyte to another.

Chromosomes