This study explores the genetic relationship between schizophrenia and the dopamine transporter gene (DAT) by a variety of methods. In a sample of 48 families - each family containing at least one nuclear family with a pair of affected siblings - we performed linkage analysis using the maximum likelihood (LOD score) method as well as sibpair analysis (identity by descent). In addition, we investigated a sample of 108 nuclear families - index case affected with schizophrenia/chronic schizoaffective disorder - for association using the haplotype relative risk method. Linkage between schizophrenia and DAT using two- and three-point linkage analysis was excluded with all disease models employed. No evidence for association between haplotypes of the VNTR-probe of the DAT and schizophrenia has been detected. Thus, a contribution of the DAT gene to the genetic diathesis of schizophrenia is unlikely in the families studied.

The fatty acid (FA) relative concentration (g/100g) of human milk triglyceride (TG) was compared to that of adipose tissue (AT). A high concentration of linoleic acid (C-18:2) was present in AT, probably reflecting long term high linoleic acid dietary intake. Linoleic acid was slightly lower in colostrum and transitional milk. No difference in C-18:2 relative concentration was seen between AT and human milk obtained 6 weeks post-partum. Marked short-term dietary modification in linoleic acid intake of the mother, 6 weeks post-partum, did not result in changes in C-18:2 relative concentration of human milk. In spite of measured marked intradiurnal variability in C-18:2 intake, human milk TG FA relative concentration remained remarkably constant. It is suggested that human milk TG FA composition reflects, mainly, the composition of AT. With the increased dietary intake of polyunsaturated fat in many populations, high levels of linoleic acid in human milk are to be expected. The intake of this fatty acid may exceed the suggested daily allowance and thus cause harmful effects, particularly in preterm infants.