Oogenesis in the Apogamous Fern Pteris cretica

The events that characterize egg formation and maturation inPteris cretica were investigated using transmission electronmicroscopy and electron microscope microprobe analysis. Theydid not differ significantly from those described for sexuallyreproducing ferns. The significance of these findings is discussedin relation to current theories concerning phase change in ferns. Pteris cretica, fern, apogamy, agamospory, transmission electron microscopy, oogenesis     

Exclusion of linkage of loci on chromosome 19 with multiple endocrine neoplasia, type 2

Linkage between seven loci on chromosome 19 and multiple endocrine neoplasia type 2a (MEN2A) was examined in a single large Swedish pedigree. A total of 50 cM was excluded from the male genetic map by pairwise analysis and an estimated 63 cM by multipoint analysis. Using existing data on the likelihood of different marker-marker distances and taking into account current exclusions on other chromosomes, the probability that the gene for MEN2A segregating in this pedigree could still be located on chromosome 19 is approximately 0.28%.     

Linkage analysis of chromosome 17 markers in British and South African families with neurofibromatosis type 1

Nine markers from the pericentromeric region of chromosome 17 were typed in 16 British and five South African families with neurofibromatosis type 1 (NF1). The markers--p17H8, pHHH202, and EW204--were linked to NF1 at recombination fractions less than 1%. No evidence of locus heterogeneity was detected. Inspection of recombinant events in families informative for several markers suggests that the NF1 gene is located between the markers EW301 (cen-p11.2) and EW206 (cen-q12) and possibly distal to pHHH202 (q11.2-q12).     

Organ-related differences in binding of Dolichos biflorus agglutinin to vascular endothelium

We screened cryostat sections of tissues from 10 inbred strains of mice with a panel of conjugated lectins, in a search for polymorphisms which could be used as markers in mouse chimeras. In DDK and RIII mice, but not the other strains tested, there are binding sites on the membrane of vascular endothelial cells for Dolichos biflorus agglutinin (DBA), which is specific for terminal nonreducing N-acetyl galactosamine residues. The expression of DBA binding sites on RIII and DDK endothelium is not, however, uniform: there are consistent differences between blood vessels in different organs. These observations provide evidence of an organ-related heterogeneity in vascular endothelium which is open to biochemical analysis, and which raises the possibility that endothelial cells carry a “tissue address.”     

The Electrophoretic Velocity of Human Red Cells, of Their Ghosts and Mechanically Produced Fragments, and of Certain Lipid Complexes

Ghosts prepared in CO₂-saturated water from unwashed human red cells can be fragmented mechanically, but ghosts from thrice washed cells cannot. If the ghosts are prepared by freezing and thawing, this difference is not observed. The electrophoretic velocity varies also with the way in which the ghosts are prepared. The pH-mobility dependence of washed red cells flatten off to a plateau at pH 9, and the electrophoretic velocity is zero at about pH 2. Ghosts prepared by freezing and thawing have almost the same pH-mobility dependence, but if the ghosts are prepared in CO₂-saturated hyptonic saline, the mobility at pH 9.4 is 0.75 times that of washed cells. Fragments of ghosts of unwashed red cells have a smaller mobility than that of the red cells. Trypsin reduces the mobility of washed red cells and of ghosts. Sols of lipid complexes (lecithin, cephalin, and lipositol), at varying pH's, have a mobility 1.2 times that of the washed red cell. The pH-mobility relation is otherwise similar. These complexes can be coated with dextran and trypsin.     

Familial Site-specific Ovarian Cancer Is Linked to BRCA1 on 17q12-21

In a study of nine families with “site-specific” ovarian cancer (criterion: three or more cases of epithelial ovarian cancer and no cases of breast cancer diagnosed at age <50 years) we have obtained evidence of linkage to the breast-ovarian cancer susceptibility gene, BRCA1 on 17q12-21. If the risk of cancer in these families is assumed to be restricted to the ovary, the best estimate of the proportion of families linked to BRCA1 is .78 (95% confidence interval .32–1.0). If predisposition to both breast and ovarian cancer is assumed, the proportion linked is 1.0 (95% confidence interval .46–1.0). The linkage of familial site-specific ovarian cancer to BRCA1 indicates the possibility of predictive testing in such families; however, this is only appropriate in families where the evidence for linkage to BRCA1 is conclusive.     

Human familial and sporadic breast cancer: analysis of the coding regions of the 17β-hydroxysteroid dehydrogenase 2 gene (EDH17B2) using a single-strand conformation polymorphism assay

17-Hydroxysteroid dehydrogenase (17HSD) is one of the key enzymes in estrogen metabolism, catalyzing the reversible reaction between estradiol and the less active estrogen, estrone. The gene encoding this enzyme, EDH17B2, has been mapped to chromosome 17, region q12–q21, in the vicinity of BRCA1, an as yet unidentified gene that appears to be involved in familial breast cancer and in familial ovarian cancer. The possibility that EDH17B2 gene is the same as BRCA1 was tested by screening for mutations in the coding regions of EDH17B2, using a polymerase chain reaction/single-strand conformation polymorphism method. An AG transition creating a new BstUI site at exon 6 was the only frequent sequence alteration found in the coding region of the gene. This mutation also led to an amino acid substitution of serine to glycine at position 312 (312^S312^G) in the 17HSD protein. Since the nucleotide change was detected both in specimens from patients with familial or sporadic cancer and in control samples, and at similar rates, this mutation appears to be of a polymorphic nature. In addition, a rare polymorphism located at intron 5 was detected. This CT substitution creates a BbvI site and is not thought to have any effect on 17HSD activity. The results indicate that there are no major alterations in the coding areas of EDH17B2 and thus studies testing the hypothesis that EDH17B2 may be the same as BRCA1 should be extended to the promoter and regulatory elements of EDH17B2.