Wind patterns as a potential driver in the evolution and maintenance of a North American migratory suture zone

Suture zones are areas where range contact zones and hybrid zones of multiple taxa are clustered. Migratory divides, contact zones between divergent populations that breed adjacent to one another but use different migratory routes, are a particular case of suture zones. Although multiple hypotheses for both the formation and maintenance of migratory divides have been suggested, quantitative tests are scarce. Here, we tested whether a novel factor, prevailing winds, was sufficient to explain both the evolution and maintenance of the Cordilleran migratory divide using individual‐based models. Empirical observations of eastern birds suggest a circuitous migratory route across Canada before heading south. Western breeders, however, travel south along the Pacific coast to their wintering grounds. We modeled the effect of wind on bird migratory flights by allowing them to float at elevation using spatially explicit modeled wind data. Modeled eastern birds had easterly mean trajectories, whereas western breeders showed significantly more southern trajectories. We also determined that a mean airspeed of 18.5 m s^–1 would be necessary to eliminate this difference in trajectory, a speed that is achieved by waterfowl and shorebirds, but is faster than songbird flight speeds. These results lend support for the potential importance of wind in shaping the phylogeographic history of North American songbirds.     

具过顶古口缝的沟鞭藻化石记录及古生态

本文列举了大量具过顶古口缝的沟鞭藻囊孢在海相和非海相沉积中的记录,指出具有一构造的沟鞭藻囊孢可以细分成两个亚类,分别代表晚白垩世从海相澡类家族中分化出的两个分支：一个以Ｐａｌａｃｅｐｅｒｉｄｉｎｉｕｍ为代表,具有ｂｉｐｅｓｉｏｉｄ型反映板式;另一支以Ｓａｅｐｔｏｄｉｎｉｕｍ为代表,具有ｂｉｐｅｓｉｏｉｄ或ｃｉｎｃｔｉｏｉｄ型反映板式,前者在晚白垩世开始向淡水环境迁移,但仍有部分留在海水中,一直延续     

Effect of low-intensity millimeter wave electromagnetic radiation on regeneration of the sciatic nerve in rats

The effect of low-intensity millimeter wave electromagnetic radiation (MWR) on regeneration of the rat sciatic nerve after transection and microsurgical reapproximation was examined. Rats were exposed to 54 GHz MWR at a power density of 4 mW/cm². It was found that MWR treatment of the femoral skin in the area of suture accelerated the regeneration of nerve fibers. At the twentieth postoperative day, the MWR-treated animals had a 32% increase in the regeneration distance compared to the control animals. The conduction velocity showed a 26% increase in the MWR-treated animals. © 1996 Wiley-Liss, Inc.     

A discussion of dental homology with reference to primates

The inconsistencies which exist when the traditional tooth-to-bony-landmark/tooth-to-occlusal-relationship criteria of identification of teeth are maintained are discussed. It is pointed out how these (e.g., "the canine is the tooth behind the premaxillary-maxillary suture") can be falsified. It is also suggested that some mammals, including Tarsius and Homo sapiens, develop homologies of three sets of "teeth," and that the "adult" antemolar dentition of a mammal may be composed of retained deciduous teeth as well as permanent teeth. Following a revision of dental homologies in most primates, an approach to reevaluating dental homologies is proposed, and a model of tooth "loss" presented.     

The role of suture complexity in diminishing strain and stress in ammonoid phragmocones

Several hypotheses have been put forward to explain the sinuosity and complexity of suture lines in Ammonoidea. At present, the two principal opponent views maintain either that high complexity was a requisite to reinforce the shell in response to hydrostatic pressure, or that complexity augmented the attachment area for muscles. By using finite element calculations and analytical estimates of simplified ammonoid shell geometries, it is shown that complex suture lines reduced dramatically the strain and the stress in the phragmocone. The calculations lend support to the hypothesis that high sinuosity is an evolutionary response to external pressure. Additionally, it is found that without complex septa, the inward deformation of an ammonoid with thin shell would cause it to shrink in response to pressure and to lose buoyancy by a non-negligible amount.     

Ectocranial suture closure in Pan troglodytes and Gorilla gorilla: pattern and phylogeny

The order in which ectocranial sutures undergo fusion displays species-specific variation among primates. However, the precise relationship between suture closure and phylogenetic affinities is poorly understood. In this study, we used Guttman Scaling to determine if the modal progression of suture closure differs among Homo sapiens, Pan troglodytes, and Gorilla gorilla. Because DNA sequence homologies strongly suggest that P. troglodytes and Homo sapiens share a more recent common ancestor than either does with G. gorilla, we hypothesized that this phylogenetic relationship would be reflected in the suture closure patterns of these three taxa. Results indicated that while all three species do share a similar lateral-anterior closure pattern, G. gorilla exhibits a unique vault pattern, which, unlike humans and P. troglodytes, follows a strong posterior-to-anterior gradient. P. troglodytes is therefore more like Homo sapiens in suture synostosis.     

A new late Miocene Lymnaea with aberrant suture structure unique for the family (Gastropoda: Pulmonata: Lymnaeidae)

A new fossil species of the pond snails (family Lymnaeidae Rafinesque, 1815), Lymnaea bogatschevi sp. n., from the Neogene (Khersonian–Maeotian transition) of southern Russia is described. It is characterised by a peculiar structure of the shell suture not found elsewhere in the family Lymnaeidae (both in living and extinct taxa). The suture of L. bogatschevi sp. n. may be described as a narrow groove that penetrates deep into the shell matter. This feature is developed both in protoconch and teleoconch whorls and is presented in several 100s of specimens that precludes its origin as an individual abnormality. There are no environmental factors known to induce such groove-like sutures in aquatic pulmonates indicating a genetic basis for this structure in L. bogatschevi. Also, we report a single shell with the similar channelled suture from a sample of Lymnaea megarensis (Gaudry in Fischer, 1867) from the Pliocene of Greece. It seems, in this species the groove-like suture was represented as a rare individual aberration, and later this trait disappeared completely from the lymnaeid morphological repertoir. Possible phylogenetic relationships between L. bogatschevi and the recent L. (Kazakhlymnaea) taurica (Clessin, 1880) are suggested and briefly discussed.     

BMP9 induces osteogenesis and adipogenesis in the immortalized human cranial suture progenitors from the patent sutures of craniosynostosis patients

The cranial suture complex is a heterogeneous tissue consisting of osteogenic progenitor cells and mesenchymal stem cells (MSCs) from bone marrow and suture mesenchyme. The fusion of cranial sutures is a highly coordinated and tightly regulated process during development. Craniosynostosis is a congenital malformation caused by premature fusion of cranial sutures. While the progenitor cells derived from the cranial suture complex should prove valuable for studying the molecular mechanisms underlying suture development and pathogenic premature suture fusion, primary human cranial suture progenitors (SuPs) have limited life span and gradually lose osteoblastic ability over passages. To overcome technical challenges in maintaining sufficient and long‐term culture of SuPs for suture biology studies, we establish and characterize the reversibly immortalized human cranial suture progenitors (iSuPs). Using a reversible immortalization system expressing SV40 T flanked with FRT sites, we demonstrate that primary human suture progenitor cells derived from the patent sutures of craniosynostosis patients can be efficiently immortalized. The iSuPs maintain long‐term proliferative activity, express most of the consensus MSC markers and can differentiate into osteogenic and adipogenic lineages upon BMP9 stimulation in vitro and in vivo. The removal of SV40 T antigen by FLP recombinase results in a decrease in cell proliferation and an increase in the endogenous osteogenic and adipogenic capability in the iSuPs. Therefore, the iSuPs should be a valuable resource to study suture development, intramembranous ossification and the pathogenesis of craniosynostosis, as well as to explore cranial bone tissue engineering.     

Structural effects of an innovative surgical technique to repair heart valve defects

The structural and functional effects of the “edge-to-edge” technique on the human mitral valve have been investigated, paying particular attention to the diastolic phase. An advanced finite element model of the valve has been developed, using a hyperelastic material schematization, suitable geometry and constraint conditions, and an effective fluidodynamic analysis. The edge-to-edge suture has been applied on this model and the diastolic phase has been simulated. The results of this calculation show that the operation increases the transvalvular pressure and the maximum stress in the leaflets, which reaches a level similar to that of the systolic phase. The influence of suture position and extension, and the mitral annulus dimension has also been investigated. The results indicate that a lateral location of the stitch is better than a central one, both regarding valve functionality (pressure level and mobility) and internal stresses level, that a longer suture worsens the valve functionality but reduces the stresses level, finally, that the dilatation of the mitral annulus does not affect the valve functionality but increases the stresses level.     

Genetic consequences of the ice ages on nurseries of the bat Myotis myotis: a mitochondrial and nuclear survey

Analyses of mitochondrial DNA (mtDNA) control region polymorphism and of variation at 10 nuclear microsatellite loci were used to investigate the mechanisms and genetic consequences of postglacial expansion of Myotis myotis in Europe. Initial sampling consisted of 480 bats genotyped in 24 nursery colonies arranged along a transect of approximately 3000 km. The phylogeographical survey based on mtDNA sequences revealed the existence of major genetic subdivisions across this area, with several suture zones between haplogroups. Such zones of secondary contact were found in the Alps and Rhodopes, whereas other potential barriers to gene flow, like the Pyrenees, did not coincide with genetic discontinuities. Areas of population admixture increased locally the genetic diversity of colonies, which confounded the northward decrease in nucleotide diversity predicted using classical models of postglacial range expansion. However, when analyses were restricted to a subset of 15 nurseries originating from a single presumed glacial refugium, mtDNA polymorphism did indeed support a northwards decrease in diversity. Populations were also highly structured (PhiST = 0.384). Conversely, the same subset of colonies showed no significant latitudinal decrease in microsatellite diversity and much less population structure (FST = 0.010), but pairwise genetic differentiation at these nuclear markers was strongly correlated with increasing geographical distance. Together, this evidence suggests that alleles carried via male bats have maintained enough nuclear gene flow to counteract the effects of recurrent bottlenecks generally associated with recolonization processes. As females are highly philopatric, we argue that the maternally transmitted mtDNA marker better reflects the situation of past, historical gene flow, whereas current levels of gene flow are better reflected by microsatellite markers.