Flemish population data and sequence structure of the hypervariable tetranucleotide repeat locus D12S1090.

The allele frequency and sequence structure of the STR locus D12S1090 were investigated in 598 Flemish individuals. The locus shows a complex organisation with repetitions of GATA interrupted by TA and other tetra- and pentanucleotide blocks. No deviation from Hardy-Weinberg equilibrium was observed. The extensive polymorphism makes it a powerful tool for identity as well as paternity testing and even permits differentiation of closely related populations, such as Flemish and Germans. D12S1090 seems to be one of the most informative STRs, however, as seen in other highly variable STRs, the observed mutation frequency of 5.1 x 10(-3), is relatively high. of STR loci is typing highly polymorphic STRs such as ACTBP2 [3]. We thus investigated the tetranucleotide (GATA) repeat locus D12S1090 (GDB accession number GDB:376560, also known as GATA5A09) in a population sample from Flanders, the Dutch speaking part of Belgium. Although this STR is considered to be highly polymorphic [4], compared with other STRs, it has only scarcely been studied.

Mutation of the repeat number of the HPRTB locus and structure of rare intermediate alleles.

During routine paternity testing a mutation of a paternal allele at the HPRTB locus was observed. The opportunity was taken to analyse this mutation at a molecular level. The repeat sequence is flanked by an imperfect repeat sequence and this region could be involved in the mutation mechanism. For this reason, we also examined the structure of "intermediate" alleles. Sequencing confirmed the insertion of a perfect repeat motif and revealed a deletion of a dinucleotide some 50 nucleotides downstream from the repeat sequence for the intermediate alleles. It is likely that these intermediate alleles are rare biallelic deletion polymorphisms and are probably not involved in the mutation or variation mechanism of this locus.

Allele frequencies of nine STR systems in the Flemish population and application in parentage testing.

In order to apply a set of nine STR loci in parentage testing, we performed a population genetic study on a sample of the Flemish population. Genotypes for HUMHPRTB, HUMFABP, HUMCD4, HUMCSF1PO, HUMTH01, HUMPLA2A, HUMPLA2A1, HUMF13A01, HUMCYAR04 and HUMLIPOL were determined using three triplex PCR reactions and silver staining. Allele frequencies showed no deviation from Hardy-Weinberg equilibrium. The frequency distribution agreed well with other Caucasian populations but three intermediate fragments, not previously found in Caucasians, were observed. We then resolved a series of 151 parentage disputes of which 103 were exclusions. In six cases, evidence for exclusion was obtained by only one informative STR locus out of eight for male children or out of nine for female children. These exclusions were confirmed with additional polymorphic markers. In one case of inclusion, a paternal allele expanded with one repeat unit of HUMHPRTB. This observation illustrates that STRs do not differ from other genetic systems in the fact that more than one excluding locus is required before exclusion is demonstrated.

The mechanism of white cell reduction by synthetic fiber cell filters.

The mechanism of white cell (WBC) retention by synthetic fiber-based WBC filters was studied. Filters were made of nonwoven fleece prepared from polyester, surface-modified polyester, or polypropylene fibers. Human platelet concentrates were filtered through experimental filters consisting of 8 to 54 layers of nonwoven fleece with mean pore sizes from 7.3 to 14.2 microns. Filters made of fleece of smaller pore size removed WBCs less effectively than filters with larger-pore fleece. Retention of lymphocytes and granulocytes gradually dropped to 0 percent as increasing loads were applied to the filters. The maximal retention capacity for these cell types (i.e., the number of cells retained when "saturating" numbers of WBCs were applied) was proportional to the number of layers of filter material used. Platelet retention did not correlate with WBC retention. Depth filtration, rather than mechanical sieving, seems to be the principal means of WBC removal by nonwoven fiber filters. A low initial number of WBCs in the component to be filtered is important for successful WBC filtration.

Embryo-derived platelet activating factor, a marker of embryo quality and viability following ovarian stimulation for in vitro fertilization.

Embryo-derived platelet-activating factor (PAF) may be an important mediator of early maternal recognition of pregnancy. PAF was higher in media associated with clinical pregnancies when compared to preclinical pregnancies but not higher in pregnant vs nonpregnant groups. The production of PAF by the preimplantation embryo was not related to follicle size or embryo morphology. However, differences in PAF concentrations in the culture media were related to the age of the embryo culture medium and the developmental stage of the embryo.

Comparison between different pre-treatment techniques for sperm recovery prior to intrauterine insemination, GIFT or IVF.

An attempt was made to compare different pre-treatment techniques in 16 normal and proven fertile and 30 subnormal and hitherto infertile semen samples. The techniques used were (i) standard, (ii) layering, (iii) discontinuous Percoll density gradient and (iv) albumin columns. Percoll gradient was most effective in separating a high fraction of progressive motile spermatozoa (75 and 57% in normal and subnormal semen samples, respectively). The albumin columns, as well as the standard techniques, were equally effective in recovering 45 and 24% respectively of progressive motile spermatozoa in normal and subnormal semen samples. The layering method was the least effective of the four techniques (4% recovery in normal and subnormal semen samples). In cases of contamination with inflammatory cells, the standard and layering methods were significantly (P less than 0.001) more advantageous than isolations with Percoll gradient and albumin columns. The percentage of ideal forms of spermatozoa recovered from a normal semen sample was significantly higher with the standard (P less than 0.01), layering (P less than 0.05) and Percoll gradient (P less than 0.05) techniques. In subnormal samples, only the Percoll gradient gave a significantly (P less than 0.02) higher percentage of ideal forms, whereas the other techniques were less effective. The significance and practical use of the various pre-treatment techniques are discussed in relation to the characteristics of the pre-treatment semen sample.