Statistical mechanics of relative species abundance

Statistical mechanics of relative species abundance (RSA) patterns in biological networks is presented. The theory is based on multispecies replicator dynamics equivalent to the Lotka–Volterra equation, with diverse interspecies interactions. Various RSA patterns observed in nature are derived from a single parameter related to productivity or maturity of a community. The abundance distribution is formed like a widely observed left-skewed lognormal distribution. It is also found that the “canonical hypothesis” is supported in some parameter region where the typical RSA patterns are observed. As the model has a general form, the result can be applied to similar patterns in other complex biological networks, e.g. gene expression.     

Effect of ethacrynic acid on contractility and Ca flux of guinea pig taenia coli smooth muscle (author's transl)

The effects of ethacrynic acid (ETCA) which has been known as an -SH groups inhibitor on the contractility and the Ca flux of guinea pig taenia coli were investigated. The results obtained were as follow: 1) Contractures induced by 10(-4) M ACh, or the tonic component of 150 mM K-contractures were markedly suppressed by previous treatment with a low concentration (2 X 10(-4) M) of ETCA for 40 min. Conversely with the same treatment, the phasic component of this K-contracture was only slightly suppressed. The inhibitory effects of ETCA in both cases were reversed by the repetitive washing out of ETCA from taenia coli with normal tris-buffered solution. 2) ETCA, at concentrations higher than 10(-3) M, more markedly inhibited the ACh-, and the K-contractures. In this case these inhibitions were irreversible. 3) Cysteine in an equimolar concentration of ETCA prevented the inhibitory effects of ETCA on both contractures. 4) ETCA (10(-4) M) inhibited the ACh-contracture in Ca2+-free isotonic KCl solution to approximately the same degree as that in normal solution. 5) Inhibition of ACh-contracture by ETCA in Na+-free isotonic LiCl solution was less than that in normal solution. 6) ETCA (2 X 10(-4), or 10(-3) M) markedly stimulated 45Ca efflux from taenia coli in 20 mM Ca-EGTA tris-buffered solution. 7) 45Ca efflux acceleration by ETCA in Na+-free (replaced by Li+) 20 mM Ca-EGTA tris-buffered solution was less than that in 20 mM Ca-EGTA tris-buffered solution. These results may be explained by assuming that the inhibitory effect of ETCA on ACh-contracture can be attributed to the depletion of stored intracellular Ca and the acceleration of Ca efflux as a result of ETCA treatment.     

Normal embryonic development of the greater horseshoe bat Rhinolophus ferrumequinum,with special reference to nose leaf formation

The order Chiroptera (bats) is the second largest group of mammals, composed of more than 1,300 species. Although powered flight and echolocation in bats have attracted many biologists, diversity in bat facial morphology has been almost neglected. Some bat species have a “nose leaf,” a leaf-like epithelial appendage around their nostrils. The nose leaf appears to have been acquired at least three times independently in bat evolution, and its morphology is highly diverse among bats species. Internal tissue morphology of nose-leaves has been investigated through histological analyses of late-stage fetuses of some bat species possessing the nose leaf. However, the proximate factors that bring about chiropteran nose-leaves have not been identified. As an initial step to address the question above, we describe the normal embryonic development of the greater horseshoe bat Rhinolophus ferrumequinum, and examine development of the tissues associated with their nose leaf during embryogenesis through histological analyses. We found that the nose leaf of R. ferrumequinum is formed through two phases. First, the primordium of the nose leaf appears as two tissue bulges aligned top and bottom on the face at embryonic stages 15–16. Second, the sub-regions of the nose leaf are differentiated through ingrowth as well as outgrowth of the epithelium at stage 17. In embryogenesis of Carollia perspicillata, a phyllostomid species with a nose leaf, the nose leaf primordium is formed as a small tissue bulge on the nostril at stage 17. This tissue bulge grows into a dorsally projected thin epithelial structure. Such differences in the nose leaf developmental process between chiropteran lineages may suggest that distinct developmental mechanisms have been employed in each lineage's nose leaf evolution.     

Contact with basement membrane heparan sulfate enhances the growth of transformed vascular endothelial cells, but suppresses normal cells.

Modulation of vascular endothelial cell growth by basement membrane heparan sulfate was investigated using four lines of normal and transformed cells. The growth of transformed endothelial cells, but not normal cells, on reconstituted basement membrane was severely suppressed when heparan sulfate, one of the components of the membrane, was specifically degraded by an enzyme, heparitinase. Similarly, when cells were grown on surfaces coated with heparan sulfate, as little as 60 pg/cm2 of heparan sulfate caused growth enhancement of transformed cells, but suppression of normal cells. These results together with our previous observations (IMAMURA, T and MITSUI, Y. (1987) Exp. Cell Res., 172: 92-100) argue that transformed cells have reversed a mechanism by which basement membrane heparan sulfate functions as a physiological suppressor for the growth of normal endothelial cells.     

Creating morphological diversity in reptilian temporal skull region: A review of potential developmental mechanisms

Reptilian skull morphology is highly diverse and broadly categorized into three categories based on the number and position of the temporal fenestrations: anapsid, synapsid, and diapsid. According to recent phylogenetic analysis, temporal fenestrations evolved twice independently in amniotes, once in Synapsida and once in Diapsida. Although functional aspects underlying the evolution of tetrapod temporal fenestrations have been well investigated, few studies have investigated the developmental mechanisms responsible for differences in the pattern of temporal skull region. To determine what these mechanisms might be, we first examined how the five temporal bones develop by comparing embryonic cranial osteogenesis between representative extant reptilian species. The pattern of temporal skull region may depend on differences in temporal bone growth rate and growth direction during ontogeny. Next, we compared the histogenesis patterns and the expression of two key osteogenic genes, Runx2 and Msx2, in the temporal region of the representative reptilian embryos. Our comparative analyses suggest that the embryonic histological condition of the domain where temporal fenestrations would form predicts temporal skull morphology in adults and regulatory modifications of Runx2 and Msx2 expression in osteogenic mesenchymal precursor cells are likely involved in generating morphological diversity in the temporal skull region of reptiles.