X-linked borderline mental retardation with prominent behavioral disturbance: phenotype, genetic localization, and evidence for disturbed monoamine metabolism.

We have identified a large Dutch kindred with a new form of X-linked nondysmorphic mild mental retardation. All affected males in this family show very characteristic abnormal behavior, in particular aggressive and sometimes violent behavior. Other types of impulsive behavior include arson, attempted rape, and exhibitionism. Attempted suicide has been reported in a single case. The locus for this disorder could be assigned to the Xp11-21 interval between DXS7 and DXS77 by linkage analysis using markers spanning the X chromosome. A maximal multipoint lod score of 3.69 was obtained at the monoamine oxidase type A (MAOA) locus in Xp11.23-11.4. Results of 24-h urine analysis in three affected males indicated a marked disturbance of monoamine metabolism. These data are compatible with a primary defect in the structural gene for MAOA and/or monoamine oxidase type B (MAOB). Normal platelet MAOB activity suggests that the unusual behavior pattern in this family may be caused by isolated MAOA deficiency.     

Asymmetric somatic hybrids between Lycopersicon esculentum and irradiated Lycopersicon peruvianum

Summary Asymmetric somatic hybrids of Lycopersicon esculentum and Lycopersicon peruvianum were analysed for the retention of genes and alleles specific for L. peruvianum. The hybrids were obtained by fusion of protoplasts from L. esculentum with those of L. peruvianum (the donor), the latter having been irradiated before fusion with 50, 300 or 1,000 Gy of gamma-rays. The retention of three different types of genes or alleles was analysed. (1) The gene coding for kanamycin resistance, which is dominant and had been introduced in most of the L. peruvianum donor plants by transformation. It was present at one locus in 16 L. peruvianum donor plants and at two loci in one donor plant. (2) The genes coding for acid phosphatase, locus Aps-1, and glutamate oxaloacetate transaminase (GOT); different alleles of these genes are co-dominant and were detected by isozyme analysis. (3) Eighteen single gene morphological markers for which most of the L. esculentum genotypes used were homozygous recessive. Kanamycin resistance from donor plants with one locus was retained in about 50% of the asymmetric 30H-hybrids (the donor was irradiated with 300 Gy). L. peruvianum specific alleles of Aps-1 and GOT were present in at least 70% of the hybrids; the retention of donor alleles was lower in 30H- than in 5H-hybrids (donor irradiated with 50 Gy). On average, 73% of the L. peruvianum-specific alleles (one or both) of the morphological markers were detected in the 30H-hybrids. Several of the L. esculentum genotypes used were homozygous recessive for two morphological markers on the same chromosome; in 43% of the 30H-hybrids derived from them, only one of these markers was complemented by the L. peruvianum allele. This is an indication of frequent breakage of the L. peruvianum chromosomes. Several hybrid calli regenerated genotypically different shoots. On the whole, this analyses confirms the conclusion drawn from the cytogenetic and morphological analysis of these asymmetric hybrids, namely that irradiation prior to fusion eliminates the L. peruvianum genome to only a limited extent.     

Polymer length of teichuronic acid released from cell walls of Micrococcus luteus.

Teichuronic acid released from its phosphodiester linkage to peptidoglycan in the cell walls of Micrococcus luteus by mild acid treatment is resolved into a ladderlike series of bands by electrophoresis on polyacrylamide gels in the presence of borate. Each band of the ladder differs from its nearest neighbor by one disaccharide repeat unit, ----4)-2-acetamido-2-deoxy-beta-D-mannopyranuronosyl-(1----6)- alpha-D-glucopyranosyl-(1-. Acid-fragmented teichuronic acid, after conversion to the phenylamine derivative, was fractionated by preparative-scale molecular sieve column chromatography, which produced a series of elution peaks. Fast-atom-bombardment mass spectrometry of the smallest member of the series determined its molecular weight and established its identity as the phenylamine derivative of one disaccharide repeat unit of teichuronic acid. Homologous fractions of the same series were used to index the ladder of bands obtained by polyacrylamide gel electrophoresis from samples containing a more extensive distribution of polymer lengths. Nearly native teichuronic acid consists of polymers with a broad range of molecular sizes ranging from 20 to 55 disaccharide units. The most abundant species are those which have 25 to 40 repeat units. Prolonged treatment of teichuronic acid with the acid conditions used to release it from peptidoglycan causes gradual fragmentation of the teichuronic acid.     

Effect of membrane fatty acid substitution and temperature on repair of sublethal damage in mammalian cells

Repair of sublethal radiation damage (SLD) has been investigated as a function of temperature in mouse fibroblast LM cells with different membrane lipid composition. Rigidification or fluidization of the cellular membranes was accomplished by incorporation of myristic acid and arachidonic acid, respectively, in the phospholipids of the membranes. The SLD repair after radiation was essentially the same for the cells with the more rigid (saturated fatty acid) membranes and the cells with the more fluid (polyunsaturated fatty acid) membranes. This observation was made for repair at 37 degrees C as well as for repair at hypothermic temperatures. Incorporation of polyunsaturated fatty acid protected the cells against hypothermic death. These experiments demonstrate that although membranes are likely targets for cell killing by low temperature treatments, membrane lipids are probably not involved in the repair of sublethal radiation damage. It must be concluded that neither the degree of polyunsaturation of the lipids nor the degree of fluidity of the membrane is important for radiation-induced killing of mammalian cells.     

The response of carabids to landscape simplification differs between trophic groups

We studied the response of carabid species richness and density to landscape simplification (measured as percentage cover of non-crop habitat surrounding each study site) in 36 wheat fields using pitfall traps. Carabids were divided to trophic groups following the literature. The number of species from different trophic groups declined with increasing landscape simplification in the order: carnivores > phytophages > omnivores. Density compensation of both carnivores and phytophages suggests that species decline is caused by the loss of specific resources rather than by an overall reduction in food availability. Increasing evenness indicates that a greater share of phytophagous species contributes to density compensation at poorer sites. A comparison with data from complementing studies shows that marked differences in species numbers (carnivores > omnivores > phytophages) are due to a different sensitivity of trophic groups to agricultural management. Since our findings seem to be partly due to increasing sensitivity to landscape changes with trophic rank, and partly to decreasing sensitivity of depauperate communities to local environmental stress, species loss can best be explained by the co-action of factors at local and regional scales. Species richness decline might significantly alter the role of carabids as biocontrol agents.     

Stable isotope measurements confirm consumption of submerged macrophytes by macroinvertebrate and fish taxa

Many macrophyte species in lowland streams exhibit signs of grazing and herbivore damage, even though herbivory by aquatic macroinvertebrates and fish is generally considered to be of little importance. In this study, we collected evidence for the hypothesis that herbivory on macrophytes by macroinvertebrates and fish is more widespread than assumed. We measured the dual stable isotope signatures (δ¹³C and δ¹⁵N) of organic matter, epiphyton, submerged macrophytes, macroinvertebrates and fish in a Belgian lowland stream. There was a clear distinction in isotopic signatures of the different basal resources, allowing the use of the SIAR mixing model. These calculations revealed the consumption of macrophyte tissue not only by the phytophagous larvae of Nymphula nitidulata Hufnagel (Lepidoptera: Crambidae), but also by Baetidae nymphs (Ephemeroptera), Orthocladiinae larvae (Diptera: Chironomidae), the crayfish Orconectus limosus Rafinesque (Decapoda: Cambaridae) and the fish Gobio gobio L. (Cypriniformes: Cyprinidae) which are classified as feeding on other resources. Although the potential share of macrophyte biomass in the diet of macroinvertebrates and fish was demonstrated to be up to 49%, this amount is only a small percentage of the total standing macrophyte biomass in a lowland stream. However, the impact of this herbivory may still be substantial because consumption may comprise a significant fraction of the daily primary production. Additionally, small-scale herbivory may still have a negative impact on macrophyte growth and survival, for example through consumption of apical meristems and the increased susceptibility to diseases and toxins if the macrophyte’s epidermis is damaged.     

The microfood web of grassland soils responds to a moderate increase in atmospheric CO2

The response of the soil microfood web (microflora, nematodes) to a moderate increase in atmospheric CO₂ (+20%) was investigated by means of a free air CO₂ enrichment experiment. The study was carried out in a seminatural temperate grassland for a period of 4 consecutive years (1 year before fumigation commenced and 3 years with fumigation). Several soil biological parameters showed no change (microbial biomass, bacterial biomass) or decline (microbial respiration) in the first year of elevated CO₂ treatment as compared with controls. Each of these parameters were higher than controls, however, after 3 years of treatment. The relative abundance of predaceous nematodes also decreased in year 1 of the experiment, increased in year 2, but decreased again in year 3. In contrast, the relative abundance of root hair feeding nematodes, at first, increased under elevated CO₂ and then returned to the initial level again. Increased microbial biomass indicates enhanced C storage in the labile carbon pool of the active microfood web in subsequent years. According to measurements on the amounts of soil extractable C, changes in resource availability seem to be key to the response of the soil microfood web. We found a strong response of bacteria to elevated CO₂, while the fungal biomass remained largely unchanged. This contrasts to findings reported in the literature. We hypothesize that this may be because of contrasting effects of different levels of CO₂ enrichment on the microbial community (i.e. stimulation of bacteria at moderate levels and stimulation of fungi at high levels of CO₂ enrichment). However, various CO₂ effects observed in our study are similar in magnitude to those observed in other studies for a much higher level of atmospheric carbon. These include the particular sensitivity of predaceous nematodes and the long‐term increase of microbial respiration. Our findings confirm that the potential of terrestrial ecosystems to accumulate additional carbon might be lower than previously thought. Furthermore, CO₂‐induced changes of temperate grassland ecosystems might emerge much earlier than expected.     

Mitotic and meiotic irregularities in somatic hybrids of Lycopersicon esculentum and Solanum tuberosum.

Chromosome numbers were determined in metaphase complements of root-tip meristems of 107 tomato (+) potato somatic hybrids, obtained from five different combinations of parental genotypes. Of these hybrids 79% were aneuploid, lacking one or two chromosomes in most cases. All four hybrids that were studied at mitotic anaphase of root tips showed laggards and bridges, the three aneuploids in a higher frequency than the single euploid. Hybrid K2H2-1C, which showed the highest percentage of aberrant anaphases, possessed 46 chromosomes. Fluorescence in situ hybridization with total genomic DNA showed that this hybrid contained 23 tomato, 22 potato, and 1 recombinant chromosome consisting of a tomato chromosome arm and a potato chromosome arm. The potato parent of K2H2-1C was aneusomatic in its root tips with a high frequency of monosomic and trisomic cells and a relatively high frequency of cells with one fragment or telosome. Meiotic analyses of three tomato (+) potato somatic hybrids revealed laggards, which occurred most frequently in the triploid hybrids, and bridges, which were frequently present in pollen mother cells (PMCs) at anaphase I of hypotetraploid K2H2-1C. We observed putative trivalents in PMCs at diakinesis and metaphase I of eutriploid A7-82A and quadrivalents in part of the PMCs of hypotetraploid K2H2-1C, suggesting that homoeologous recombination between tomato and potato chromosomes occurred in these hybrids. All three hybrids showed a high percentage of first division restitution, giving rise to unreduced gametes. However, shortly after the tetrad stage all microspores completely degenerated, resulting in exclusively sterile pollen.