Traces of embryogenesis are the same in monozygotic and dizygotic twins: not compatible with double ovulation.

Common knowledge of over a century has it that monozygotic and dizygotic twinning events occur by unrelated mechanisms: monozygotic twinning 'splits' embryos, producing anomalously re-arranged embryogenic asymmetries; dizygotic twinning begins with independent ovulations yielding undisturbed parallel embryogeneses with no expectation of departures from singleton outcomes. The anomalies statistically associated with twin births are due to the re-arranged embryos of the monozygotics. Common knowledge further requires that dizygotic pairs are dichorionic; monochorionicity is exclusive to monozygotic pairs.

Embryogenesis of chimeras, twins and anterior midline asymmetries.

Human spontaneous chimerism, with one body built from cells of both twins of a dizygotic (DZ) pair, is supposed to be extremely rare, arising from the exchange of blood cells through placental anastomoses. Mosaicism is supposed to be far more common, arising from single zygotes by embryonic mutation. Because typical diagnosis of mosaicism can neither identify nor exclude chimerism, 'mosaicism' may often be chimerism undiscovered.

The epigenetic environment: secondary sex ratio depends on differential survival in embryogenesis.

Live human births are usually more than half male, in spite of excess losses of males throughout fetal development. These observations together demand an excess of males near the beginning of pregnancy greater than that seen at birth. Reductions of the usual excess of males among human live births have widely been considered to represent consequences of untoward circumstances surrounding conception.

[Intraoperative ventricular fibrillation in a patient with chronic cocaine abuse--a case report].

With increasing drug abuse of cocaine, the chances are growing that an anaesthetist comes into contact with an acutely intoxicated patient or chronic cocaine user while on call or during his daily routine. In South America chewing coca leaves is daily practise, while in the industrialised world the drug is sniffed, smoked or injected intravenously. Clinically, cocaine is used topically in ENT and ophthalmology due to its local analgesic and strong vasoconstrictive properties.