Social play does not reduce aggression in wild meerkats

Of the numerous hypotheses advanced to explain the adaptive significance of play, several assert that social play increases social harmony, cementing alliances and reducing aggression between group members or littermates. These hypotheses are frequently cited, but their validity remains unknown. We examined the relation between social play and aggression in juvenile meerkats, Suricata suricatta, living in a wild population in the southern Kalahari Desert. We tested the hypothesis that social play reduces aggression, by examining rates of play, play partner choices, the structure of social play and rates of aggressive interactions during foraging. We found no relation between frequency of play and level of aggression, either between individuals or during the course of development. Pups that played together frequently were just as aggressive towards one another as pairs of pups that played infrequently, and play interactions had no subsequent effect on the likelihood of aggression. In contrast, aggressive interactions during foraging inhibited the subsequent likelihood of play, and high levels of aggression during foraging changed the structure of social play, with victimized pups avoiding play wrestling. We conclude that social play does not reduce aggression in young meerkats. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.      

Transgenic mouse model of kidney disease: insertional inactivation of ubiquitously expressed gene leads to nephrotic syndrome.

Transgenic mouse strains carrying proviruses were generated by exposing mouse embryos to a recombinant retrovirus. Animals carrying a single provirus were intercrossed to derive mice homozygous for a given proviral insertion. Adult mice homozygous for the Mpv17 integration developed nephrotic syndrome and chronic renal failure. Histologically, affected kidneys showed progressive glomerular sclerosis. Similar lesions are seen in patients with progressive renal function deterioration. A probe to DNA sequences flanking the provirus detected a 1.7 kb RNA ubiquitously expressed during embryogenesis and in adults with high levels in kidney, brain, and heart. This RNA was not detected in tissues of homozygous animals, suggesting that the provirus interferes with RNA expression. Sequence analysis of the cDNA revealed that the gene encodes a 176 amino acid peptide containing hydrophobic regions, suggesting membrane association of the putative protein. The Mpv17 mutant is a potentially useful experimental system for studying mechanisms leading to renal disorders in man.     

Cell wall elasticity: I. A critique of the bulk elastic modulus approach and an analysis using polymer elastic principles

The traditional bulk elastic modulus approach to plant cell pressure-volume relations is inconsistent with its definition. The relationship between the bulk modulus and Young's modulus that forms the basis of their usual application to cell pressure-volume properties is demonstrated to be physically meaningless. The bulk modulus describes stress/strain relations of solid, homogeneous bodies undergoing small deformations, whereas the plant cell is best described as a thin-shelled, fluid-filled structure with a polymer base. Because cell walls possess a polymer structure, an alternative method of mechanical analysis is presented using polymer elasticity principles. This initial study presents the groundwork of polymer mechanics as would be applied to cell walls and discusses how the matrix and microfibrillar network induce nonlinear stress/strain relationships in the cell wall in response to turgor pressure. In subsequent studies, these concepts will be expanded to include anisotropic expansion as regulated by the microfibrillar network.     

Analysis of the human alpha globin upstream regulatory element (HS-40) in transgenic mice.

We have analysed the effect of a 1.4 kb segment of DNA containing the upstream alpha globin regulatory element (HS-40) on human alpha globin gene expression in fetal mice and lines of transgenic mice. High levels of tissue-specific, human alpha mRNA expression were seen in all transgenic animals and in this sense expression was position independent. However, the level of human alpha mRNA expression per integrated gene copy decreased during development and was inversely related to copy number. The limitation in expression with increasing gene copy number was shown to be in cis since homozygotes for the transgene produced twice as much human alpha mRNA as hemizygotes. In many respects HS -40 appears similar to single elements within the previously described beta globin locus control region and in cross breeding experiments we have shown that HS -40 behaves in a similar manner to such elements in transgenic mice.     

Three dimensional typological studies using scanning electron microscopy for characterization of Termitomyces pellets obtained from submerged growth conditions

There are gaps in existing understanding of fungal pellet growth dynamics. We used scanning electron microscopy (SEM) for morphological characterization of the biomass organization of Termitomyces pellets for seven species: T. microcarpus (TMI1), T. albuminosus (TAL1, TAL2), T. striatus (TSTR), T. aurantiacus (TAUR), T. heimii (THE1, THE2), T. globulus (TGLO) and T. clypeatus (TCL1, TCL2, TCL3, TCL4, TCL5). We assessed the utility of SEM for morphological and structural characterization of Termitomyces spp. in three dimensional (3D) pellet form to identify ideal pellet morphology for industrial use. Typological classification of Termitomyces species was based on furrows, isotropy, total motifs and fractal dimensions. The pellets formed were entangled and exhibited highly compacted mycelial mass with microheterogeneity and microporosity. The mean density of furrows of Termitomyces species was between 10,000 and 11,300 cm/cm², percentage isotropy was 30?80 and total motifs varied from 300 to 2500. TGLO exhibited the highest furrow mean density, 11243 cm/cm², which indicated a compact, cerebroid structure with complex ridges and furrows, whereas TAL2 exhibited the lowest furrow density. TMI1a exhibited a high percentage isotropic value, 74.6, TSTR exhibited the lowest, 30.9. Total motif number also was used as a typological classification parameter. Fractal values were 2.64?2.78 for various submerged conditions of Termitomyces species. TAL1 exhibited the highest fractal dimension and TAL2 the lowest, which indicates the complexity of branching patterns. Three-dimensional SEM image analysis can provide insight into pellet micromorphology and is a powerful tool for exploring topographical details of pellets.