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.      

Tension-volume relationship of the wall of the isolated right ventricle]

The variations of tension on the wall of the isolated right verticle have been observed on 18 dogs. The Tension/Volume curve we got can be superimposed to that obtained by pressures. The wall of the right ventricle itself (the radius of the curve in the cavity and the wall-thickness) seems to vary only with the changes in its tension in a rather small part of the curve.     

Pressure-volume relationship in the right ventricle]

The curve of the pressure-volume relationships of the right ventricular cavity is not a mono-exponential one. It can be characterized by the presence of two successive segments: linear and exponential. The points that constitute the first of them could not be subjected to Starling's law. This is material for the physiopathology of the tamponade.     

Synthesis and biological evaluation of novel anticancer bivalent colchicine-tubulizine hybrids

A series of novel antimitotic hybrids were synthesized in good yields by linking of azide-containing colchicine congeners with acetylene-substituted tubulizine-type derivatives using copper-mediated 1,3-dipolar cycloaddition. Obtained compounds exhibit good cytotoxicity against HBL100 epithelial cell lines (IC(50)=0.599-2.93 μМ). Several newly synthesized compounds are the substoichiometric inhibitors of microtubule assembly (R=0.41-0.78). The results highlight the importance of the length of spacer linking the tubulin binding ligands in heterodimeric molecules.     

Lymph heart musculature is under distinct developmental control from lymphatic endothelium

Lymph hearts are pulsatile organs, present in lower vertebrates, that function to propel lymph into the venous system. Although they are absent in mammals, the initial veno-lymphatic plexus that forms during mammalian jugular lymph sac development has been described as the vestigial homologue of the nascent stage of ancestral anterior lymph hearts. Despite the widespread presence of lymph hearts among vertebrate species and their unique function, extremely little is known about lymph heart development. We show that Xenopus anterior lymph heart muscle expresses skeletal muscle markers such as myoD and 12/101, rather than cardiac markers. The onset of lymph heart myoblast induction can be visualized by engrailed-1 (en1) staining in anterior trunk somites, which is dependent on Hedgehog (Hh) signaling. In the absence of Hh signaling and upon en1 knockdown, lymph heart muscle fails to develop, despite the normal development of the lymphatic endothelium of the lymph heart, and embryos develop edema. These results suggest a mechanism for the evolutionary transition from anterior lymph hearts to jugular lymph sacs in mammals.     

Phylogenetic analysis of the alpha-globin pseudogene-4 (Hba-ps4) locus in the house mouse species complex reveals a stepwise evolution of t haplotypes [published erratum appears in Mol Biol Evol 1994 Jan;11(1):158]

A parsimony analysis was performed on restriction sites at the Hba-ps4 pseudogene locus within one of four inversions associated with mouse t haplotypes. The results suggest that all t haplotypes form a monophyletic group and that the in (17)4 inversion originated before the radiation of the Mus musculus species complex but after the divergence of the lineages leading to M. spretus, M. abbotti, and M. hortulanus. A time frame based on the evolutionary rate of mouse pseudogenes places the origin of this t haplotype inversion at 1.5 Mya, or approximately 1.5 Myr after the origin of the more proximal t complex inversion, in (17)2. The accumulated evidence indicates that complete t haplotypes have been assembled in a stepwise manner, with each of these inversions occurring on separate chromosomal lineages and at different evolutionary times. In addition, the evolutionary relationships of pseudogene sequences resulting from genetic exchange between wild-type and t haplotype alleles were examined. Analysis of sequences from the 5' and 3' sides of a putative site of recombination resulted in cladograms with different topologies. The implications for hypotheses concerning the evolutionary forces acting on t haplotypes and their rapid propagation throughout worldwide populations of mice are discussed.