Host-based morphometric differentiation in three Cinara species (Insecta: Hemiptera: Aphididae) feeding on Pinus edulis and P. monophylla

Cinara edulis (Wilson), C. terminalis (Gillette and Palmer), and C. wahtolca Hottes were all larger when feeding on Pinus monophylla Torr. & Frem. than when feeding on P. edulis Engelm. Almost all nonsetal morphometric characters were longer in aphids on the former of these pinyon pines. Although mouthpart characters also followed this pattern of size in C. edulis and C. wahtolca , rostrum length showed the opposite pattern in C. terminalis and was shorter when on P. monophylla . This reversal in size pattern suggests that mouthpart size can be independent of overall aphid size. Principal components analyses corroborate the univariate statistics and we discuss the contribution of various characters to the principal components. We compare environmental induction and environmental selection as explanations for the observed size differences and discuss the taxonomic implications of our results.     

Differential phytosociological interactions involving male and female Atriplex bonnevillensis

Wind-pollinated dioecious plants often exhibit spatial segregation of the sexes. This partial niche separation has most often been explored using abiotic niche axes. However, if the sexes are truly separated in space, then they are apt to encounter different plant species that may heavily affect growth and reproduction. Also, to the extent that their niches differ, the sexes may respond differently to the same co-occurring species. Here we examine interspecific interactions that influence male and female reproductive potential in Atriplex bonnevillensis. Using Emlen’s interaction assessment, a technique which assesses species interactions based on cover classes, we show that Salsola species compete significantly with females but not males, while Halogeton glomeratus competes with males but not females. The effect of competition only became apparent when we corrected for site-specific fertility. These results imply that differential competition must be considered when studying dioecious plants that display spatial segregation of the sexes.     

Isozymes of an autopolyploid shrub, Atriplex canescens (Chenopodiaceae)

Diploid, tetraploid, and hexaploid populations of Atriplex canescens ( x =9) were examined for 18 isozyme systems. Of 24 interpretable loci, only one locus (Per 1 ) was polymorphic. Another locus (Per 2 ) showed a dosage effect. Genetic distance values, D, ranged from near 0 to 0.05, which are in the normal range for local species races. Results from clonal ramets gave identical results. The data and analyses support an essentially autopolyploid origin for the polyploid populations examined.     

The transmembrane protein meckelin (MKS3) is mutated in Meckel-Gruber syndrome and the wpk rat

Meckel-Gruber syndrome is a severe autosomal, recessively inherited disorder characterized by bilateral renal cystic dysplasia, developmental defects of the central nervous system (most commonly occipital encephalocele), hepatic ductal dysplasia and cysts and polydactyly. MKS is genetically heterogeneous, with three loci mapped: MKS1, 17q21-24 (ref. 4); MKS2, 11q13 (ref. 5) and MKS3 (ref. 6). We have refined MKS3 mapping to a 12.67-Mb interval (8q21.13-q22.1) that is syntenic to the Wpk locus in rat, which is a model with polycystic kidney disease, agenesis of the corpus callosum and hydrocephalus. Positional cloning of the Wpk gene suggested a MKS3 candidate gene, TMEM67, for which we identified pathogenic mutations for five MKS3-linked consanguineous families. MKS3 is a previously uncharacterized, evolutionarily conserved gene that is expressed at moderate levels in fetal brain, liver and kidney but has widespread, low levels of expression. It encodes a 995-amino acid seven-transmembrane receptor protein of unknown function that we have called meckelin.     

Localization and possible role of membrane type metallo-proteinase and tissue inhibitors of metalloproteinase-1 in early stages of placentation

Human placental tissues from the first and second trimesters of gestation have been investigated using riboprobein situ hybridisation of mRNA sequences coding for membrane type metalloproteinase (MT-1-MMP) and tissue inhibitors of metalloproteinase-1 (TIMP-1). Results show that (i) both mRNAs express at a relatively high level in the chorion laeve trophoblast cells and the adjacent decidual cells of fetal membrane; (ii) the most abundant expression of the two mRNAs was found in the extravillous trophoblast between Rohrs and Nitabuch striae of basal plate, trophoblast shell and gland cells of the decidua; (iii) isolated or small groups of cytotrophoblast cells in the chorionic villi and in the cells lining arterioles in decidua and stem villi also expressed both MT-1-MMP and TIMP-1 at defferent extents. The data suggest that the coordinated expression of the MT-MMP and its inhibitor TIMP in defferent cells of the placental tissue may play an essential role in trophoblast invasion and angiogenesis related to placentation in the first two trimesters of gestation. They may also have an ability to effect separation of fetal from material tissue at a favorable junctional site during parturition.     

Sequence polymorphism of HLA DR beta 1 alleles relating to T-cell-recognized determinants

HLA class II molecules are a highly polymorphic family of dimeric cell-surface proteins primarily involved in regulating T-cell responses to extrinsic antigens. To define regions of class II molecules involved in T-cell recognition, we have now compared sequences of three HLA DR beta cDNA clones obtained from cells that all express the same serologically defined determinants but differ in terms of T-cell-recognized specificities. The comparisons indicate that very few (one to four) nucleotides differ between what are almost certainly alleles of the DR beta 1 locus. All differences were in the first domain of the molecule and all localized to a region from amino acids 71-86. Because all differences were found only in this region of the molecule, and because DR alpha-chains seem to be relatively non-polymorphic, these positions in the DR beta-chain must have a major role in influencing T-cell recognition of the DR molecule.     

Increasing adult hippocampal neurogenesis is sufficient to improve pattern separation

Adult hippocampal neurogenesis is a unique form of neural circuit plasticity that results in the generation of new neurons in the dentate gyrus throughout life. Neurons that arise in adults (adult-born neurons) show heightened synaptic plasticity during their maturation and can account for up to ten per cent of the entire granule cell population. Moreover, levels of adult hippocampal neurogenesis are increased by interventions that are associated with beneficial effects on cognition and mood, such as learning, environmental enrichment, exercise and chronic treatment with antidepressants. Together, these properties of adult neurogenesis indicate that this process could be harnessed to improve hippocampal functions. However, despite a substantial number of studies demonstrating that adult-born neurons are necessary for mediating specific cognitive functions, as well as some of the behavioural effects of antidepressants, it is unknown whether an increase in adult hippocampal neurogenesis is sufficient to improve cognition and mood. Here we show that inducible genetic expansion of the population of adult-born neurons through enhancing their survival improves performance in a specific cognitive task in which two similar contexts need to be distinguished. Mice with increased adult hippocampal neurogenesis show normal object recognition, spatial learning, contextual fear conditioning and extinction learning but are more efficient in differentiating between overlapping contextual representations, which is indicative of enhanced pattern separation. Furthermore, stimulation of adult hippocampal neurogenesis, when combined with an intervention such as voluntary exercise, produces a robust increase in exploratory behaviour. However, increasing adult hippocampal neurogenesis alone does not produce a behavioural response like that induced by anxiolytic agents or antidepressants. Together, our findings suggest that strategies that are designed to increase adult hippocampal neurogenesis specifically, by targeting the cell death of adult-born neurons or by other mechanisms, may have therapeutic potential for reversing impairments in pattern separation and dentate gyrus dysfunction such as those seen during normal ageing.