A NEW ANGUIMORPH LIZARD FROM THE LOWER MIOCENE OF NORTH-WEST BOHEMIA, CZECH REPUBLIC

Abstract:  The cranial remains of a new Lower Miocene anguimorph, Merkurosaurus ornatus gen. et sp. nov., are described from north-west Bohemia (Czech Republic). The animal is morphologically very similar to the Recent Shinisaurus crocodilurus , but it differs in several ways. The distinctive features of Merkurosaurus are: the nasal process of premaxilla is long and slender with a bilaterally constricted shaft and bilaterally broadened dorsal portion; the dorsal portion of the nasal process divides into three processes of which the median one is the longest; the ornamented surface of the parietal is subdivided into five pustule-like mounds on both right and left sides, with one further mound around the posterior and lateral margins of the parietal foramen. A close phylogenetic affinity to the anguimorph genera Shinisaurus , Bahndwivici , Dalinghosaurus and Carusia , and partially to Xenosaurus , is indicated by characters such as: frontal fused with deep cristae cranii; lateral border of frontals strongly constricted between orbits; double interorbital row of large mounds diverge posteriorly along orbital margin; sculptured postorbital ramus of jugal; small mounds on frontal and parietal with ornamented vermiculate structures; and parietal foramen within parietal but close to anterior margin. Merkurosaurus is the only taxon of this affinity known from the Cenozoic of Eurasia.     

The Proteolytic Potential of Normal Human Melanocytes: Comparison With Other Skin Cells and Melanoma Cell Lines

To understand the contribution of epidermal melanocytes in the proteolytic potential of human skin, we have studied melanocytes grown in a low-serum medium deprived of phorbol esters, cholera toxin, and other non-physiological supplements. We focused on the plasminogen activation system and certain matrix metalloproteinases (gelatinases). Supposing that the proteolytic activity of cells can influence binding to collagen matrix and its reorganization, we have analyzed these parameters as well. We found that human melanocytes secreted tissue-type plasminogen activator and utilised it to generate cell-bound plasmin. No urokinase-type plasminogen activator was detected in the cultures but its receptor was found in cell extracts. Both the 72 kDa and 92 kDa gelatinases were secreted by the cells and in equal amounts. In addition, melanocytes secreted the wide-spectrum proteinase inhibitor alpha-2-macroglobulin. Melanocytes cast into collagen matrices retained a rounded morphology, did not extend processes, and were unable to contract collagen lattices. As a control, these parameters were investigated in parallel in cultures of human keratinocytes, dermal fibroblasts, and two melanoma cell lines. The obtained characteristics suggest that normal human melanocytes are proteolytically active cells. This function may pertain to skin physiology and pathophysiology.     

Variation in Discosauriscus austriacus (Makowsky, 1876) from the Lower Permian of the Boskovice Furrow (Czech Republic)

Two genera and four species of discosauriscids, Discosauriscus potamites, D. pulcherrimus, Letoverpeton austriacum and L. moravicum , have previously been described from the Boskovice Furrow in Moravia. These laxa were differentiated primarily on the basis of proportional differences of the skull together with other morphological characters.
Excavations at two localities in the Boskovice Furrow have produced new, relatively abundant, skeletal material. The specimens are preserved three-dimensionally. In order to evaluate the differences in skull proportions, 17 variable characters on 70 skulls were measured. Statistical analysis demonstrates the existence of several morphological trends in the shape of the skull. However, no trend permits the division of this set of specimens into two clearly differentiated groups. The morphological differences used previously to define genera and species seem to be incorrect. Pending the discovery of distinct morphological differences, the Moravian discosauriscids can be considered as belonging to only one taxon: Discosauriscus austriacus (Makowsky, 1876).     

The cranial anatomy,ontogeny, and relationships of Karpinskiosaurus secundus (Amalitzky) (Seymouriamorpha,Karpinskiosauridae) from the Upper Permian of European Russia

The Upper Permian seymouriamorph tetrapod Karpinskiosaurus from European Russia includes two species: Karpinskiosaurus secundus and Karpinskiosaurus ultimus. Karpinskiosaurus secundus is represented by two specimens with skull lengths of about 75 mm. All specimens of K. ultimus are smaller than those of K. secundus. Revision of the cranial anatomy of all previously known and several new specimens of Karpinskiosaurus shows that the specimens of K. secundus and most of the specimens of K. ultimus represent the ontogenetic series of one species: K. secundus. The holotype specimen of K. ultimus requires revision, with the aim to find out whether it represents a second species of Karpinskiosaurus or not. The available material permits new reconstructions of the largest, holotype skull, and one smaller skull with a length of about 36 mm. Karpinskiosaurus secundus is included in a cladistic analysis for the first time here. The analysis shows it to form a sister taxon to Discosauriscidae. The clade comprising Karpinskiosaurus secundus plus Discosauriscidae forms a sister group to Seymouriidae. Karpinskiosaurus secundus has a large postorbital and a short preorbital region, and the orbits are placed in the posterior portion of the anterior half of the skull length. Among all seymouriamorphs, such cranial proportions are exhibited only by the largest known specimens of Discosauriscus austriacus. None of the specimens of K. secundus described here exhibits the presence of sensory grooves; thus, all specimens composing the ontogenetic sequence of K. secundus are considered to be terrestrial. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010.     

MtZR1, a PRAF protein,is involved in the development of roots and symbiotic root nodules in Medicago truncatula

PRAF proteins are present in all plants, but their functions remain unclear. We investigated the role of one member of the PRAF family, MtZR1, on the development of roots and nitrogen‐fixing nodules in Medicago truncatula. We found that MtZR1 was expressed in all M. truncatula organs. Spatiotemporal analysis showed that MtZR1 expression in M. truncatula roots was mostly limited to the root meristem and the vascular bundles of mature nodules. MtZR1 expression in root nodules was down‐regulated in response to various abiotic stresses known to affect nitrogen fixation efficiency. The down‐regulation of MtZR1 expression by RNA interference in transgenic roots decreased root growth and impaired nodule development and function. MtZR1 overexpression resulted in longer roots and significant changes to nodule development. Our data thus indicate that MtZR1 is involved in the development of roots and nodules. To our knowledge, this work provides the first in vivo experimental evidence of a biological role for a typical PRAF protein in plants.     

Patterns of allozyme variation in western Eurasian Fagus

Fagus sylvatica L. is one of the most widespread broad‐leaved trees in the temperate forests of the northern hemisphere. In addition to two subspecies, F. sylvatica ssp. sylvatica in Europe and F. sylvatica ssp. orientalis in south‐western Asia, two further taxa were described: F. moesiaca (Maly) Czeczott in the south‐western Balkans and F. taurica Popl. in Crimea. The opinions about the number and ranks of taxa within this complex are highly controversial. To assess the degree of genetic differentiation among them, and to reveal geographical patterns of genetic diversity and their relationships to history and biogeography of beech populations, genetic variation at 12 allozyme loci was studied in 279 populations in western Eurasia. A Bayesian analysis of population structure revealed the existence of two clusters, which fairly well coincided with F. sylvatica ssp. sylvatica and F. sylvatica ssp. orientalis, whereby the populations from the south‐western Balkans and Crimea contained a mixture of these two gene pools. On the other hand, a neighbour‐joining tree based on pairwise F_ST failed to separate the subspecies into well‐defined distinct clades. Populations of F. sylvatica ssp. orientalis proved to be incomparably more differentiated than ssp. sylvatica (F_ST = 0.157 and 0.032, respectively). Asian populations also showed higher levels of allelic richness both on population and taxon levels than the European ones (the number of alleles after rarefaction was 3.40 and 4.27 in F. sylvatica ssp. sylvatica and ssp. orientalis, respectively). This indicates that the gene pool of F. sylvatica ssp. orientalis has not been depleted by reduced population sizes during the Pleistocene glaciations, as is the case of F. sylvatica ssp. sylvatica. Genetic similarities between isolated regional populations are explained by shared ancestral polymorphisms and/or range overlaps with subsequent hybridization in the past. © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 154 , 165–174.