Screening and diagnosis for the fragile X syndrome among the mentally retarded: an epidemiological and psychological survey. Collaborative Fragile X Study Group.

The fragile X syndrome is an X-linked mental retardation disorder caused by an expanded CGG repeat in the first exon of the fragile X mental retardation (FMR1) gene. Its frequency, X-linked inheritance, and consequences for relatives all prompt for diagnosis of this disorder on a large scale in all affected individuals. A screening for the fragile X syndrome has been conducted in a representative sample of 3,352 individuals in schools and institutes for the mentally retarded in the southwestern Netherlands, by use of a brief physical examination and the DNA test. The attitudes and reactions of (non)consenting parents/guardians were studied by (pre- and posttest) questionnaires. A total of 2,189 individuals (65%) were eligible for testing, since they had no valid diagnosis, cerebral palsy, or a previous test for the FMR1 gene mutation. Seventy percent (1,531/2,189) of the parents/guardians consented to testing. Besides 32 previously diagnosed fragile X patients, 11 new patients (9 males and 2 females) were diagnosed. Scoring of physical features was effective in preselection, especially for males (sensitivity .91 and specificity .92). Major motives to participate in the screening were the wish to obtain a diagnosis (82%), the hereditary implications (80%), and the support of research into mental retardation (81%). Thirty-four percent of the parents/guardians will seek additional diagnostic workup after exclusion of the fragile X syndrome. The prevalence of the fragile X syndrome was estimated at 1/ 6,045 for males (95% confidence interval 1/9,981-1/ 3,851). On the basis of the actual number of diagnosed cases in the Netherlands, it is estimated that >50% of the fragile X cases are undiagnosed at present.     

Isolated lissencephaly sequence associated with a microdeletion at chromosome 17p13

Summary DNA markers YNZ22.1, YNH37.3, 144D6 and VAW508 were studied in a patient with the isolated lissencephaly sequence (ILS). A normal karyotype was found in the patient. The DNA of the patient showed deletions of markers YNZ22.1 and YNH37.3. This is the first report of a case of ILS (with grade 3 lissencephaly) with a submicroscopic deletion. The presence of a micro deletion in 17p13 in an ILS patient indicates that Miller-Dieker syndrome and ILS have a common etiology.     

Primary antibody-forming cells and secondary B cells are generated from separate precursor cell subpopulations

Two precursor cell subpopulations have been isolated from the spleen cells of nonimmune mice. The major B cell subpopulation binds high levels of the J11D monoclonal antibody and, upon T cell-dependent antigenic stimulation, gives rise to primary antibody-forming cell clones but not secondary B cells. A minority of the 10%-14% of Ia+ precursors that bind low levels of J11D (J11Dlo) also generate antibody-forming cell clones after primary stimulation. However, over 70% of J11Dlo precursors yield no primary antibody-forming cell clones but instead give rise to secondarily responsive B cells. The existence of a distinct precursor cell subpopulation that is responsible for the generation of B cell memory is further evidenced by the distribution of variable region clonotypes among J11Dlo primary precursors, which resembles the clonotype patterns of secondary B cells, and by the accumulation of somatic mutations in their clonal progeny.     

Nitric oxide degradation by potato tuber mitochondria: Evidence for the involvement of external NAD(P)H dehydrogenases

The mechanisms of nitric oxide (NO) synthesis in plants have been extensively investigated. NO degradation can be just as important as its synthesis in controlling steady-state levels of NO. Here, we examined NO degradation in mitochondria isolated from potato tubers and the contribution of the respiratory chain to this process. NO degradation was faster in mitochondria energized with NAD(P)H than with succinate or malate. Oxygen consumption and the inner membrane potential were transiently inhibited by NO in NAD(P)H-energized mitochondria, in contrast to the persistent inhibition seen with succinate. NO degradation was abolished by anoxia and superoxide dismutase, which suggested that NO was consumed by its reaction with superoxide anion (O₂⁻). Antimycin-A stimulated and myxothiazol prevented NO consumption in succinate- and malate-energized mitochondria. Although favored by antimycin-A, NAD(P)H-mediated NO consumption was not abolished by myxothiazol, indicating that an additional site of O₂⁻ generation, besides complex III, stimulated NO degradation. Larger amounts of O₂⁻ were generated in NAD(P)H- compared to succinate- or malate-energized mitochondria. NAD(P)H-mediated NO degradation and O₂⁻ production were stimulated by free Ca²⁺ concentration. Together, these results indicate that Ca²⁺-dependent external NAD(P)H dehydrogenases, in addition to complex III, contribute to O₂⁻ production that favors NO degradation in potato tuber mitochondria.     

Properties of natural double-strand-break sites at a recombination hotspot in Saccharomyces cerevisiae

This study addresses three questions about the properties of recombination hotspots in Saccharomyces cerevisiae: How much DNA is required for double-strand-break (DSB) site recognition? Do naturally occurring DSB sites compete with each other in meiotic recombination? What role does the sequence located at the sites of DSBs play? In S. cerevisiae, the HIS2 meiotic recombination hotspot displays a high level of gene conversion, a 3''-to-5'' conversion gradient, and two DSB sites located approximately 550 bp apart. Previous studies of hotspots, including HIS2, suggest that global chromosome structure plays a significant role in recombination activity, raising the question of how much DNA is sufficient for hotspot activity. We find that 11.5 kbp of the HIS2 region is sufficient to partially restore gene conversion and both DSBs when moved to another yeast chromosome. Using a variety of different constructs, studies of hotspots have indicated that DSB sites compete with one another for DSB formation. The two naturally occurring DSBs at HIS2 afforded us the opportunity to examine whether or not competition occurs between these native DSB sites. Small deletions of DNA at each DSB site affect only that site; analyses of these deletions show no competition occurring in cis or in trans, indicating that DSB formation at each site at HIS2 is independent. These small deletions significantly affect the frequency of DSB formation at the sites, indicating that the DNA sequence located at a DSB site can play an important role in recombination initiation.     

The <Emphasis Type="Italic">CLCA</Emphasis> gene locus as a modulator of the gastrointestinal basic defect in cystic fibrosis

To determine whether the CLCA gene family of calcium-activated chloride channels is a modulator of the basic defect of cystic fibrosis (CF), an association study was performed with polymorphic microsatellite markers covering a 40-Mbp region spanning the CLCA gene locus on human chromosome 1p in CF patients displaying CF transmembrane conductance regulator (CFTR)-independent residual chloride conductance in gastrointestinal epithelia. Statistically significant association of the electrophysiological phenotype with the allele distribution of markers 5 of and within the CLCA locus was observed. Transmission disequilibrium and the significance of the association decreased within the locus from hCLCA2 towards hCLCA4. Expression of hCLCA1 and hCLCA4 in human rectal mucosa was proven by microarray analysis. The CLCA gene region was identified to encode mediators of DIDS-sensitive anion conductance in the human gastrointestinal tract that modulate the CF basic defect.     

Antiparasite treatments reduce humoral immunity and impact oxidative status in raptor nestlings

Parasites are natural stressors that may have multiple negative effects on their host as they usurp energy and nutrients and may lead to costly immune responses that may cause oxidative stress. At early stages, animals may be more sensitive to infectious organisms because of their rapid growth and partly immature immune system. The objective of this study was to explore effects of parasites by treating chicks of two raptor species (northern goshawk Accipiter gentilis and white‐tailed sea eagle Haliaeetus albicilla) against both endoparasites (internal parasites) and ectoparasites (external parasites). Nests were either treated against ectoparasites by spraying with pyrethrin or left unsprayed as control nests. Within each nest, chicks were randomly orally treated with either an antihelminthic medication (fenbendazole) or sterile water as control treatment. We investigated treatment effects on plasma (1) total antioxidant capacity TAC (an index of nonenzymatic circulating antioxidant defenses), (2) total oxidant status TOS (a measure of plasmatic oxidants), and (3) immunoglobulin levels (a measure of humoral immune function). Treatment against ectoparasites led to a reduction in circulating immunoglobulin plasma levels in male chicks. TOS was higher when not receiving any parasite reduction treatment and when receiving both endo‐ and ectoparasitic reduction treatment compared with receiving only one treatment. TAC was higher in all treatment groups, when compared to controls. Despite the relatively low sample size, this experimental study suggests complex but similar relationships between treatment groups and oxidative status and immunoglobulin levels in two raptor species.     

The effect of nitrate assimilation deficiency on the carbon and nitrogen status of Arabidopsis thaliana plants

Carbon (C) and nitrogen (N) metabolism are integrated processes that modulate many aspects of plant growth, development, and defense. Although plants with deficient N metabolism have been largely used for the elucidation of the complex network that coordinates the C and N status in leaves, studies at the whole-plant level are still lacking. Here, the content of amino acids, organic acids, total soluble sugars, starch, and phenylpropanoids in the leaves, roots, and floral buds of a nitrate reductase (NR) double-deficient mutant of Arabidopsis thaliana (nia1 nia2) were compared to those of wild-type plants. Foliar C and N primary metabolism was affected by NR deficiency, as evidenced by decreased levels of most amino acids and organic acids and total soluble sugars and starch in the nia1 nia2 leaves. However, no difference was detected in the content of the analyzed metabolites in the nia1 nia2 roots and floral buds in comparison to wild type. Similarly, phenylpropanoid metabolism was affected in the nia1 nia2 leaves; however, the high content of flavonol glycosides in the floral buds was not altered in the NR-deficient plants. Altogether, these results suggest that, even under conditions of deficient nitrate assimilation, A. thaliana plants are capable of remobilizing their metabolites from source leaves and maintaining the C–N status in roots and developing flowers.     

The role of glyceraldehyde 3-phosphate dehydrogenase (GapA-1) in <Emphasis Type="Italic">Neisseria meningitidis</Emphasis> adherence to human cells

Background  

Glyceraldehyde 3-phosphate dehydrogenases (GAPDHs) are cytoplasmic glycolytic enzymes, which although lacking identifiable secretion signals, have also been found localized to the surface of several bacteria (and some eukaryotic organisms); where in some cases they have been shown to contribute to the colonization and invasion of host tissues. Neisseria meningitidis is an obligate human nasopharyngeal commensal which can cause life-threatening infections including septicaemia and meningitis. N. meningitidis has two genes, gapA-1 and gapA-2, encoding GAPDH enzymes. GapA-1 has previously been shown to be up-regulated on bacterial contact with host epithelial cells and is accessible to antibodies on the surface of capsule-permeabilized meningococcal cells. The aims of this study were: 1) to determine whether GapA-1 was expressed across different strains of N. meningitidis; 2) to determine whether GapA-1 surface accessibility to antibodies was dependant on the presence of capsule; 3) to determine whether GapA-1 can influence the interaction of meningococci and host cells, particularly in the key stages of adhesion and invasion.