Ataxia with Vitamin E Deficiency: Refinement of Genetic Localization and Analysis of Linkage Disequilibrium by Using New Markers in 14 Families

Ataxia with vitamin E deficiency (AVED) is an autosomal recessive disease characterized clinically by neurological symptoms with often striking resemblance to those of Friedreich ataxia. This disorder has been reported previously as familial isolated vitamin E deficiency. We have mapped recently the AVED locus to a 5-cM confidence interval on chromosome 8q by homozygosity mapping in six Mediterranean families. We have now analyzed six new and two previously described families and demonstrate genetic homogeneity despite important clinical variability and wide geographic origins. Analysis of nine new tightly linked microsatellite markers, including four characterized in this study, revealed a predominant but not unique mutation in northern African populations, where this condition is more frequent. Haplotype analysis but also classical recombinations allowed us to refine the AVED position to a 1-cM interval. A YAC contig over this interval was constructed from marker STSs and YAC fingerprint data, in order to facilitate the search of the AVED gene.     

Direct molecular analysis of the fragile X syndrome in a sample of Egyptian and German patients using non-radioactive PCR and Southern blot followed by chemiluminescent detection

Molecular genetic analysis of individuals from 6 Egyptian and 33 German families with fragile X syndrome and 240 further patients with mental retardation was performed applying a completely non-radioactive system. The aim of our study was the development of a non-radioactive detection method and its implementation in molecular diagnosis of the fragile X syndrome. Furthermore, we wanted to assess differences in the mutation sizes between Egyptian and German patients and between Egyptian and German carriers of a premutation. Using non-radioactive polymerase chain reaction (PCR), agarose gel electrophoresis and blotting of the PCR products, followed by hybridisation with a digoxigenin-labelled oligonucleotide probe (CGG)₅ and chemiluminescent detection, we identified the fragile X full mutation (amplification of a CGG repeat in the FMR-1 gene ranging from several hundred to several thousand repeat units) in all patients. We observed no differences in the length of the CGG repeat between the Egyptian and German patients and carriers, respectively. However, in one prenatal diagnosis, we detected only one normal sized allele in a female fetus using the PCR-agarose assay, whereas Southern blot analysis with the digoxigenin labelled probe StB 12.3 revealed presence of a full mutation. Our newly established nonradioactive genomic blotting method is based on the conventional radioactive Southern blot analysis. Labelling of the probe StB 12.3 with digoxigenin via PCR allowed the detection of normal, premutated and fully mutated alleles. For exact sizing of small premutated or large normal alleles, we separated digoxigenin labelled PCR products through denaturing poly-acrylamide gelelectrophoresis (PAGE) and transfered them to a nylon membrane using a gel dryer. The blotted PCR-fragments can easily be detected with alkaline phosphate-labelled anti-digoxigenin antibody. The number of trinucleotide repeat units can be determined by scoring the detected bands against a digoxigenated M13 sequencing ladder. Our newly developed digoxigenin/chemiluminescence approach using PCR and Southern blot analysis provides reliable results for routine detection of full fragile X mutations and premutations.     

Cloning of the natural gene for the sweet-tasting plant protein thaumatin

Five different clones, homologous to the structural gene for the sweet-tasting plant protein thaumatin, have been isolated from leaf DNA of Thaumatococcus daniellii Benth. Restriction maps, hybridization studies, S1-nuclease mapping and R-loop formation revealed that the thaumatin genes isolated belong to one multigene family, and have two very small introns situated at different positions in the various structural genes. A similar situation prevails in a number of seed storage genes. This suggests a similarity between the sweet-tasting protein thaumatin and seed storage proteins.     

Catecholamines in fetal pig plasma and the response to acute hypoxia and chronic fetal decapitation

Summary Dopamine, norepinephrine and epinephrine were measured by radioenzymatic assay in blood plasma samples drawn from the umbilical arteries of 30 anaesthetised Landrace pig fetuses. Just prior to term, the concentrations of dopamine (0.46±0.14 ng·ml^–1) and norepinephrine (1.74±0.60 ng·mg^–1) were lower than earlier in gestation, whereas epinephrine concentrations at term (0.80±0.31 ng·ml^–1) were similar to those at mid-gestation, intervening stages of gestation having higher levels of plasma epinephrine. Fetal hypoxia was induced by clamping the umbilical cord for 2 min and the catecholamines determined in arterial blood samples immediately thereafter, then again 3 min after removal of the clamp. Inconsistent effects of cord clamping on catecholamine levels were seen at 55 days, but thereafter, in all but one instance, the hormone levels were increased. Fetuses near term tended to respond less than fetuses at 75 and 96 days gestation (term=114±1 day). Catecholamines were also present in the circulation of fetuses decapitated at 42 days gestation and studied at 109±1 days. The average concentrations of dopamine (1.12±0.27 ng·ml^–1) and norepinephrine (8.23±3.04 ng·ml^–1) were greater than in intact fetuses, the plasma epinephrine levels being comparable to, or slightly higher than, those in intact fetuses. The results demonstrate that catecholamines are present in the circulation of the intact and decapitated pig fetus and that the actual concentrations and the type of response to umbilical cord clamping are dependent on gestation age.     

Callus formation from Malus x domestica cv. ‘Jonathan’ protoplasts

Protoplasts could be successfully isolated and cultured from callus and suspension cultures of Malus xdomestica cv. Jonathan. Protoplast-derived colonies were recovered when the osmoticum (glucose) was gradually reduced in semi-solid 8p medium or by the use of feeder plates. Formation of embryo-like structures was induced from the protoplast-derived callus on media supplemented with IAA and BA. These structures formed roots but plants failed to develop. Protoplasts could be isolated from leaves, but not from stems or petioles. The leaf protoplasts failed to divide.List of abbreviations BA benzyladenine - 2,4-D 2,4-dichlorophenoxyacetic acid - ABA abscisic acid - IAA indole acetic acid     

Genetic and biosynthetic studies of families carrying hemoglobin J α Mexico: Association of α-thalassemia with Hb J

Summary Hemoglobin J Mexico, an chain mutant, was studied in eight unrelated Algerian families. The quantities of the abnormal hemoglobin in 116 subjects are trimodally distributed: 55% in homozygotes, 31% and 38% in heterozygotes. Both hematological data and the / chain biosynthetic ratio are normal in heterozygotes with 31% Hb J and in homozygotes. In contrast, the MCV and MCH as well as the / biosynthetic ratio are slightly reduced in heterozygotes with 38% Hb J and in their relatives carrying Hb A. The elevated expression of ^J chains in heterozygotes with 38% Hb J may be due to an thalassemia gene trans to the ^>J locus.     

Architecture of the outer membrane of Escherichia coli K12. II. Freeze fractur morphology of wild type and mutant strains

Freeze fracturing electron microscopy of Escherichia coli K12 cells showed that the outer fracture face of the outer membrane is densily occupied with particles. On the inner fracture face of the outer membrane, pits are visible, which are probably complementary to the particles at opposite fracture face. This observation suggests that the particles are micelle-like. In some mutants which lack one or more major outer membrane proteins the density of particles is reduced. The loss of protein d appeared to a prerequisite for this phenomenon. However, mutants which lack all glucose and heptose-bound phosphate in their lipopolysaccharide also have a reduction in particle density whereas, the amount of protein d is normal. Moreover, loss of lipopolysaccharide by EDTA treatment also caused a reduction in the density of particles. From these results it is hypothesized that the particles consist of lipopolysaccharide aggregates stabilized by divalent cations and probably complexed with protein and/or phospholipid.     

Retinoic acid induces transglutaminase activity but inhibits cornification of cultured epidermal cells

In cultured mouse epidermal basal cells, retinoic acid is a potent inducer of transglutaminase, the enzyme responsible for isodipeptide bond formation in protein cross-linking in the production of the cornified membrane during terminal differentiation. Paradoxically retinoic acid also inhibits the formation of the cross-linked envelope and greatly reduces the level of dipeptide bond formation in epidermal cells induced to differentiate by calcium. These results suggest a novel mechanism by which retinoids can modify transglutaminase activity and epidermal differentiation.     

The effect of monochromatic radiation in the range 350 to 750 nm on the carotenogenesis in Verticillium agaricinum

An action spectrum for carotenogenesis in V. agaricinum has maxima at 395, 433, 660 and 737 nm. In a previous study it had been shown that a light-minus-dark difference spectrum of a crude extract from V. agaricinum had maxima at 390 and 420 nm, and furthermore a red, far-red interaction suggesting phytochrome involvement has been proposed. All these data suggest that there may be at least two photoreceptor systems operating in the photoinduction process here; one for the near-ultraviolet (UV-A)-mediated carotenogenesis, presumably a novel pigment, and the other for the red, far-red region, most likely phytochrome.