Molecular evidence for the rapid propagation of mouse t haplotypes from a single, recent, ancestral chromosome

Mouse t haplotypes are variant forms of chromosome 17 that exist at high frequencies in worldwide populations of two species of commensal mice. To determine both the relationship of t haplotypes to each other and the species within which they exist, 35 representative t haplotypes were analyzed by means of 10 independent molecular probes, including five DNA clones and five polypeptide spots identified by means of two- dimensional gel electrophoresis. All of the tested haplotypes were found to share restriction fragments and polypeptide spots that are absent in mice carrying wild-type forms of chromosome 17. This observation provides the first direct evidence that all of the known t haplotypes are descendents of a single ancestral chromosome. The absence of variation among t haplotypes could mean that this ancestral chromosome existed relatively recently, in which case it would be necessary to postulate introgressions of t haplotypes across species lines to explain their presence in both Mus domesticus and M. musculus. Alternatively, it is possible that the ancestral chromosome existed prior to the split between M. domesticus and M. musculus and that, by chance, our probes fail to detect polymorphisms that exist among the t haplotypes. A further result of our analysis is the characterization of a partial t haplotype in a wild population of Israeli mice.      

Beta-lactamase inhibitors. The inhibition of serine beta-lactamases by specific boronic acids.

Two kinds of phosphoinositide-specific phospholipase C (PLC) were purified from rat liver by acid precipitation and several steps of column chromatography. About 50% of the activity could be precipitated when the pH of the liver homogenate was lowered to pH 4.7. The redissolved precipitate yielded two peaks, PLC I and PLC II, in an Affi-gel Blue column, and each was further purified to homogeneity by three sequential h.p.l.c. steps, which were different for the two enzymes. The purified PLC I and PLC II had estimated Mr values of 140,000 and 71,000 respectively on SDS/polyacrylamide-gel electrophoresis. Both enzymes hydrolysed phosphatidylinositol (PI), phosphatidylinositol 4-phosphate (PIP) and phosphatidylinositol 4,5-bisphosphate (PIP2) in a Ca2+- and pH-dependent manner. PLC I was most active at 10 microM- and 0.1 mM-Ca2+ for hydrolysis of PI and PIP2 respectively, whereas PLC II showed the highest activity at 5 mM- and 10 microM-Ca2+ for that of PI and PIP2 respectively. The optimal pH of the two enzymes also differed with substrates or Ca2+ concentration, in the range pH 5.0-6.0. Hydrolysis of phosphoinositides by these enzymes was completely inhibited by Hg2+ and was affected by other bivalent cations. From data obtained by peptide mapping and partial amino acid sequencing, it was clarified that PLC I and PLC II had distinct structures. Moreover, partial amino acid sequences of three proteolytic fragments of PLC I completely coincided with those of PLC-148 [Stahl, Ferenz, Kelleher, Kriz & Knopf (1988) Nature (London) 332, 269-272].     

Effect of sensory input from the tongue on jaw movement in normal feeding in the opossum

Opossums were presented with solid and liquid foods. The movements of the jaw and tongue were recorded cineradiographically together with recordings of the EMG activity in muscles opening the jaw and moving the base of the tongue (hyoid). The jaw opening in each cycle was in two stages--01 and 02; 01 had a constant amplitude irrespective of the food ingested. Ingestion of liquid (which involved continuous accumulation of a liquid bolus in the valleculae prior to swallowing) was associated with cycles of oral movement in which 02 was small; tongue retraction was associated with this opening. In contrast, solid and semisolid food ingestion was associated with large angles of jaw opening in 02 that also coincided with the tongue retraction. In this latter case a characteristic pattern of EMG activity, in which all the muscles moving the hyoid were simultaneously active, was added to the pattern seen in lapping; this additional activity had an EMG pattern that was consistent with a jaw opening reflex. The findings contrast with other reports that the jaw opening reflex is suppressed in mastication. Experimentally induced tongue contact with a variety of solid surfaces during lapping (an activity involving accumulation of a liquid bolus in the valleculae) induced neither increased jaw opening nor the additional EMG pattern. However, in situations when there was no bolus in the valleculae, additional jaw opening activity was elicited when the tongue contracted solids intra- or extra-orally. It is suggested that the ability of sensory input, from the anterior tongue, to elicit a jaw opening reflex and to change the type of jaw/tongue cycle was dependent upon the extent of bolus accumulation in the valleculae and therefore indirectly upon the consistency of the food.     

Masticatory loading and bone adaptation in the supraorbital torus of developing macaques

Research on the evolution and adaptive significance of primate craniofacial morphologies has focused on adult, fully developed individuals. Here, we investigate the possible relationship between the local stress environment arising from masticatory loadings and the emergence of the supraorbital torus in the developing face of the crab‐eating macaque Macaca fascicularis. By using finite element analysis (FEA), we are able to evaluate the hypothesis that strain energy density (SED) magnitudes are high in subadult individuals with resulting bone growth in the supraorbital torus. We developed three micro‐CT‐based FEA models of M. fascicularis skulls ranging in dental age from deciduous to permanent dentitions and validated them against published experimental data. Applied masticatory muscle forces were estimated from physiological cross‐sectional areas of macaque cadaveric specimens. The models were sequentially constrained at each working side tooth to simulate the variation of the bite point applied during masticatory function. Custom FEA software was used to solve the voxel‐based models and SED and principal strains were computed. A physiological superposition SED map throughout the face was created by allocating to each element the maximum SED value from each of the load cases. SED values were found to be low in the supraorbital torus region throughout ontogeny, while they were consistently high in the zygomatic arch and infraorbital region. Thus, if the supraorbital torus arises to resist masticatory loads, it is either already adapted in each of our subadult models so that we do not observe high SED or a lower site‐specific bone deposition threshold must apply. Am J Phys Anthropol, 2009. © 2008 Wiley‐Liss, Inc.     

Arboreality,terrestriality and bipedalism

The full publication of Ardipithecus ramidus has particular importance for the origins of hominin bipedality, and strengthens the growing case for an arboreal origin. Palaeontological techniques however inevitably concentrate on details of fragmentary postcranial bones and can benefit from a whole-animal perspective. This can be provided by field studies of locomotor behaviour, which provide a real-world perspective of adaptive context, against which conclusions drawn from palaeontology and comparative osteology may be assessed and honed. Increasingly sophisticated dynamic modelling techniques, validated against experimental data for living animals, offer a different perspective where evolutionary and virtual ablation experiments, impossible for living mammals, may be run in silico, and these can analyse not only the interactions and behaviour of rigid segments but increasingly the effects of compliance, which are of crucial importance in guiding the evolution of an arboreally derived lineage.     

The cost of ant attendance and melezitose secretion in the black bean aphid Aphis fabae

1. The aphid Aphis fabae (Scopoli) is facultatively tended by Lasius niger (Linnaeus) ants. Previously, we found that A. fabae colonies can be made up of several clones, and that clones display significant differences in the composition of their honeydew sugars, especially in the amount of the ant attractant sugar melezitose that they produce. 2. These clonal differences could greatly impact the strength of the mutualistic interaction with ants as well as the aphids' fitness. 3. Hence, the aim of this study was to compare the fitness of different A. fabae clones that differed in their melezitose secretion, and whether or not they were tended by ants. 4. Individual fitness indices, colony growth, and alate production of single‐clone aphid colonies were analysed. 5. The results demonstrate that the fitness consequences of ant attendance critically depend on an interaction between levels of melezitose production. In particular, we show that high‐melezitose secreting clones produce fewer alates and hence might have a lower dispersal ability in the presence of ants. 6. Furthermore, these data confirm previous evidence that ant attendance is costly and results in the production of fewer apterae.     

Ascaris suum: Nutrient absorption,growth, and intestinal pathology in young pigs experimentally infected with 15-day-old larvae

Three-week-old pigs on high (HP) or low (LP) protein diets were infected with 15-day-old Ascaris suum larvae (W). Including noninfected pigs (C), the experimental groups were HPW, LPW, HPC, and LPC. After 8 weeks, worm burden in the intestine averaged 42 in LPW and 31 in HPW. Nitrogen balance during Week 4 showed nonsignificantly less nitrogen absorption and retention in LPW compared to LPC. A similar, nonsignificant decrease in fat absorption was recorded in LPW vs LPC and in HPW vs HPC. The weight of the small intestine was significantly greater in W than C pigs but did not differ because of protein level. The weight correlated positively to worm burden and the increase was due mainly to hypertrophy of the tunica muscularis (muscle layers).