Sublittoral epifaunal communities at Signy Island,Antarctica. I. The ice-foot zone

Photographs were taken every 0.5 m along three transects of 5.5 m length on shallow rock faces at Signy Island, Antarctica, during the austral summer of 1991/1992. The percentage cover of substratum ranged from 0 to 100% and the colonising communities included representatives of ten phyla. The zone from mean low-water neap level to 1.5 m depth was mostly devoid of organisms as a result of the seasonal formation of the encrusting ice foot. Coralline and macroalgae dominated from 2 to 3 m, and animal groups from 3.5 to 5.5 m. Bryozoans, and to a lesser extent sponges, were the most abundant animal phyla. Within the bryozoans a succession of colonisation of different species was observed, the most abundant two of which occupied >80% of substratum in places. Substratum type seemed to be the main factor influencing community development in the shallow sublittoral at Signy Island, although ice impact prevents community development in the top 1.5 m and limits it over the rest of the transect down to 5.5 m. Depth and profile of substratum also influenced communities within this depth range (particularly taxonomic composition).     

Preimplantation genetic diagnosis of the fragile X syndrome by use of linked polymorphic markers

Fragile X syndrome is the most common cause of familial mental retardation. The most common mutation is expansion of a triplet (CGG)_n repeat in the 5′ untranslated region of the FMR1 gene on Xq27.3. The expansion is refractory to PCR due to preferential amplification of the smaller allele in heterozygous cells and the high GC content of the repeat and surrounding sequences. Direct detection of the normal parental alleles in preimplantation embryos has been used for preimplantation genetic diagnosis (PGD) of this disorder. However, this approach is only suitable for approximately 63% of couples due to the heterozygosity of the repeat in the normal population. As an alternative we investigated the use of polymorphic markers flanking the mutation to track the normal and premutation carrying maternal chromosomes in preimplantation embryos. Using a panel of 11 polymorphisms, six (CA)_n repeats and five single nucleotide polymorphisms, diagnosis was developed for 90% of referred couples. Multiplex amplification of informative markers was tested in 300 single buccal cells from interested couples with efficiency and allele drop out (ADO) rates ranging from 69% to 96% and 6% to 18%, respectively. Use of this approach is accurate and applicable to a larger number of patients at risk of transmitting fragile X to their offspring. Copyright © 2001 John Wiley & Sons, Ltd.     

The influence of lindane and lindane metabolites on microsomal and mitochondrial ATPase in vitro

In vitro investigations of the influence of lindane and its metabolites were performed on microsomal and mitochondrial ATPases from liver, kidney and brain of rat and mouse. The microsomal Na+-K+-ATPases in rat liver were inhibited by the tested substances. An increase of activity was observed only with 2.5 X 10(-5) M gamma-HCH. Effects on the microsomal Na+-K+-ATPase from kidney and brain of rat were also indicated. The mitochondrial enzyme in rat liver was stimulated by all the compounds tested at concentrations of 10(-4) M - 10(-2) M. The effects on mitochondrial enzymes from kidney and brain varied in dependence on the tested substances. In the microsomes and mitochondria of mouse an influence on the Na+-K+-ATPases similar to the effects on the preparations from organs of rat was evident.     

Prenatal diagnosis of a 45,X male with a SRY-bearing chromosome 21

Male phenotype associated with a 45,X karyotype is an infrequent finding. We present a case diagnosed prenatally on amniocentesis performed for maternal age. The male phenotype was associated with a translocation of a distal part of Yp including the pseudoautosomal SHOX gene and SRY gene on the short arm of a chromosome 21. By DNA analysis we could show that the X chromosome was of maternal origin and that the breakpoint was in interval 3 of the Y chromosome. Mechanisms and genetic counselling are discussed based on a review of published cases of 45,X and XX males. Copyright © 2002 John Wiley & Sons, Ltd.     

Prenatal diagnosis of Apert syndrome: report of two cases

Two de novo cases with Apert Syndrome detected prenatally are presented herein. In the first, fetal ultrasound findings of syndactyly of the hands, craniosynostosis and proptosis resulted in a prenatal diagnosis in the nineteenth week of gestation. This is the earliest prenatal diagnosis of this syndrome in a not-at-risk case. Following counseling, this pregnancy was terminated and subsequent pathological examination and DNA analysis confirmed the diagnosis of Apert Syndrome and coarctation of the aorta. In the second case, fetal ultrasound at 21 weeks' gestation revealed a hypoplastic left heart and clover-leaf skull. Following counseling, this pregnancy was also terminated. Further examination of the fetus and DNA analysis led to a diagnosis of Apert Syndrome. These cases emphasize the need to complete a thorough fetal ultrasound in cases with potentially lethal cardiac abnormality and the importance of incorporating a fetal pathologist, as well as a medical geneticist, in the investigations performed after delivery or pregnancy termination when a fetal abnormality is detected on ultrasound. Copyright © 2003 John Wiley & Sons, Ltd.     

Role of vitamin A in the haematotoxicity of hexachlorocyclohexane (HCH) in the rat.

The haematotoxicity of technical hexachlorocyclohexane (HCH) (1000 ppm) was investigated in male albino rats fed with diet free of vitamin A or containing vitamin A at 2000 or 10(5) I.U./kg. Assessment of HCH-induced haematotoxicity at the end of the 7 weeks feeding period was done on the basis of haemoglobin content, total count of red blood cells and white blood cells and the differential counts of the white blood cells as well as by parameters such as packed cell volume, mean corpuscular volume, mean corpuscular haemoglobin, mean corpuscular haemoglobin content, prothrombin time and clotting time. In the rats fed with vitamin A-free diet containing HCH, significant reductions were noticed in the total white blood cells count, clotting time and prothrombin time indicating severe haematotoxicity. Differential count of the white blood cells of these rats revealed a non-significant reduction in the lymphocyte count. The only indication of haematotoxicity caused by hexachlorocyclohexane in the vitamin A supplemented rats was a slight but statistically significant reduction of the total count of white blood cells. These results demonstrate that the haematotoxicity of hexachlorocyclohexane in the rats is enhanced by vitamin A-deficiency and its supplementation particularly in excess but not at hypervitaminotic level is protective against the toxicity.