Suppression of kisspeptin expression and gonadotropic axis sensitivity following exposure to inhibitory day lengths in female Siberian hamsters

To avoid breeding during unsuitable environmental or physiological circumstances, the reproductive axis adjusts its output in response to fluctuating internal and external conditions. The ability of the reproductive system to alter its activity appropriately in response to these cues has been well established. However, the means by which reproductively relevant cues are interpreted, integrated and relayed to the reproductive axis remain less well specified. The neuropeptide kisspeptin has been shown to be a potent positive stimulator of the hypothalamo-pituitary-gonadal (HPG) axis, suggesting a possible neural locus for the interpretation/integration of these cues. Because a failure to inhibit reproduction during winter would be maladaptive for short-lived female rodents, female Siberian hamsters (Phodopus sungorus) housed in long and short days were examined. In long "summer" photoperiods, kisspeptin is highly expressed in the anteroventral periventricular nucleus (AVPV), with low expression in the arcuate nucleus (Arc). A striking reversal in this pattern is observed in animals held in short, "winter" photoperiods, with negligible kisspeptin expression in the AVPV and marked staining in the Arc. Although all studies to date suggest that both populations act to stimulate the reproductive axis, these contrasting expression patterns of AVPV and Arc kisspeptin point to disparate roles for these two cell populations. Additionally, we found that the stimulatory actions of exogenous kisspeptin are blocked by acyline, a gonadotropin-releasing hormone (GnRH) receptor antagonist, suggesting an action of kisspeptin on the GnRH system rather than pituitary gonadotropes. Finally, females held in short day lengths exhibit a reduced response to exogenous kisspeptin treatment relative to long-day animals. Together, these findings indicate a role for kisspeptin in the AVPV and Arc as an upstream integration center for reproductively relevant stimuli and point to a dual mechanism of reproductive inhibition in which kisspeptin expression is reduced concomitant with reduced sensitivity of the HPG axis to this peptide.     

MTII attenuates ghrelin- and food deprivation-induced increases in food hoarding and food intake

Food deprivation triggers a constellation of physiological and behavioral changes including increases in peripherally-produced ghrelin and centrally-produced agouti-related protein (AgRP). Upon refeeding, food intake is increased in most species, however hamsters primarily increase food hoarding. Food deprivation-induced increases in food hoarding by Siberian hamsters are mimicked by peripheral ghrelin and central AgRP injections. Because food deprivation stimulates ghrelin as well as AgRP synthesis/release, food deprivation-induced increases in hoarding may be mediated by melanocortin 3 or 4 receptor (MC3/4-R) antagonism via AgRP, the MC3/4-R inverse agonist. Therefore, we asked: Can a MC3/4-R agonist block food deprivation- or ghrelin-induced increases in foraging, food hoarding and food intake? This was accomplished by injecting melanotan II (MTII), a synthetic MC3/4-R agonist, into the 3rd ventricle in food deprived, fed or peripheral ghrelin injected hamsters and housed in a running wheel-based food delivery foraging system. Three foraging conditions were used: a) no running wheel access, non-contingent food, b) running wheel access, non-contingent food or c) a foraging requirement for food (10 revolutions/pellet). Food deprivation was a more potent stimulator of foraging and hoarding than ghrelin. Concurrent injections of MTII completely blocked food deprivation- and ghrelin-induced increases in food intake and attenuated, but did not always completely block, food deprivation- and ghrelin-induced increases in food hoarding. Collectively, these data suggest that the MC3/4-R are involved in ghrelin- and food deprivation-induced increases in food intake, but other neurochemical systems, such as previously demonstrated with neuropeptide Y, also are involved in increases in food hoarding as well as foraging.     

Multi-locus real-time PCR for quantitation of bacteria in the environment reveals Exiguobacterium to be prevalent in permafrost

We developed a multi-locus quantitative PCR approach to minimize problems of precision, sensitivity and primer specificity for quantifying a targeted microbial group in nature. This approach also avoids a systematic error in population quantitation when 16S rRNA genes are used because of copy number heterogeneity. Specific primers were designed to assess the abundance of psychrotrophic and mesophilic Exiguobacterium spp. that excluded the thermophilic members of the genus. The chosen primers targeted genes for DNA gyrase B (gyrB), the beta subunit of the RNA polymerase gene (rpoB) and a hypothetical gene so far found only in this group. The results demonstrate that the multiple primer approach provides a more reliable estimate of population density; that the targeted Exiguobacterium group is found at a median density of 50,000 gene copies per mug of total community DNA in 27 of 29 permafrost soils but was found in only one of the four temperate and tropical soils tested.     

Resolving Terreneuvian stratigraphy in subtidal–intertidal carbonates: palaeontological and chemostratigraphical evidence from the Turukhansk Uplift,Siberian Platform

Both diverse assemblages of small skeletal fossils and a representative chemostratigraphical record make the Siberian Platform widely regarded as one of the key regions for the reconstruction of global biotic and abiotic events in the late Ediacaran and early Cambrian. However, the wide distribution of intertidal–subtidal facies in the Ediacaran–Cambrian transitional strata of the central and southwestern Siberian Platform (Turukhansk–Irkutsk–Olekma facies region) produces a dramatic depletion of the palaeontological record and considerably limits their age‐calibration and long‐distance correlation. We report new lithological, palaeontological and carbonate carbon‐isotope data for the Ediacaran–Cambrian sections of the Turukhansk Uplift (northwestern Siberian Platform, western facies region). These data provide a robust framework for the chemostratigraphical correlation of the western facies region with sections of the transitional and eastern regions of the Siberian Platform and further confirms a depositional hiatus at the base of the Tommotian Stage in the stratotype section (Aldan River, SE Siberia). The carbon‐isotope curve from the Turukhansk Uplift sections correlates positively with the most chemostratigraphically representative Ediacaran–Cambrian sections (Siberia, Morocco, South China). It records major carbon‐isotope oscillations globally recognized in the lower Cambrian, enabling localization of the Fortunian and Cambrian Stage 2 boundaries in the Platonovskaya Formation. Although there is extreme paucity and poor preservation of the small skeletal fossils in the western facies region, we report individual Barskovia, Blastulospongia and chancelloriid sclerites from the Platonovskaya Formation. A combination of palaeontological and chemostratigraphical data suggests the base of P. antiqua Assemblage Zone is located in the middle Platonovskaya Formation. The earliest spiral gastropods probably occurred at ~541 Ma, as demonstrated by the discovery of a specimen of Barskovia near the base of the large negative excursion in the lower Platonovskaya Formation, correlated with the BACE negative carbon‐isotope peak in the sections of the Yangtze Platform.     

Global phylogeography of the genus Capreolus (Artiodactyla: Cervidae), a Palaearctic meso‐mammal

Areas of sympatry and hybridization of closely related species can be difficult to assess through morphological differences alone. Species which coexist and are similar morphologically may be distinguished only with molecular techniques. The roe deer (Capreolus spp.) is a meso‐mammal having a Palaearctic distribution, with two closely related species: the European C. capreolus and the Siberian C. pygargus. We analysed mtDNA sequences from 245 individuals, sampled through all the entire range of the genus, to investigate the distribution of genetic lineages and outline phylogeographical patterns. We found that: (1) a C. pygargus lineage occurs in Poland and Lithuania, much farther west than the area which so far was believed its westernmost limit; (2) no haplotype of this C. pygargus lineage matches any found in East Europe and Asia – this should rule out human introductions and may indicate Pleistocene–Holocene migrations from the east; (3) no geographical structuring of C. pygargus lineages occurs, questioning the existence of putative subspecies; (4) several genetic lineages of C. capreolus can be recognized, consistent with the existence of two subspecies, respectively in central–southern Italy and southern Spain. Coalescence times suggest that intraspecific variation in C. capreolus and C. pygargus developed approximately 100–10 kya. The extant mitochondrial lineages pre‐dated the Last Glacial Maximum. Capreolus pygargus must have moved westward to Central Europe, where at least one genetic lineage still survives, coexisting with C. capreolus. © 2013 The Linnean Society of London     

The biological affinity of Amsassia: new evidence from the Ordovician of North China

Amsassia shaanxiensis sp. nov. occurs in the Middle Ordovician part of the Jinghe Formation in Yongshou and the lower part of the Upper Ordovician Beiguoshan Formation in Longxian, Shaanxi Province, north‐central China. In addition to module increase by bipartite longitudinal fission, which is also known in other species of Amsassia, tripartite and rare quadripartite fission are recognized in A. shaanxiensis. All species previously assigned to Lichenaria from the Middle to Upper Ordovician of Shaanxi probably belong to Amsassia. Therefore, Amsassia, rather than the tabulate coral Lichenaria, should be credited as an important contributor to reef‐building in this area. Reports of Lichenaria from elsewhere in the North China Platform require confirmation in the light of the present study. Some morphological characteristics of Amsassia are comparable to those of tabulate corals, tetradiids and chaetetid sponges. Consequently, various authors have assigned Amsassia to the Lichenariida, Tetradiida (now Prismostylales; florideophycean rhodophyte algae) and Chaetetida. Other important characters, however, seem to exclude Amsassia from those taxonomic groups. The phacelocerioid organization of modules having separate walls would not be expected in sponges. The basic symmetry of individuals may have been radial, unlike the tetramerous symmetry of tetradiids. Module increase by longitudinal fission, involving infoldings of the wall, is fundamentally different from modes of increase in corals, tetradiids and chaetetids. The skeleton was probably aragonitic, whereas that of tabulates was calcitic. The affinity of Amsassia remains unresolved, but it is unlikely to have been a coral, tetradiid or sponge. Perhaps, like the tetradiids, Amsassia was an alga.     

Natural durability of selected larch and Scots pine heartwoods in laboratory and field tests

The aim of this study was to compare natural durability of Siberian larch heartwood grown in Siberia and Sweden as well as European larch and Scots pine heartwood grown in Sweden. The study was based on standard in- and above ground tests lasting 12 years but laboratory decay tests with white and brown rot fungi was also included. Field test results showed that Siberian larch heartwood from Siberia was the most durable among the studied heartwoods with a decay index of 60 after 12 years in Simlångsdalen (Sweden), while European larch heartwood grown in Sweden, was decayed to failure before the end of the test. Scots pine heartwood was found to perform similarly to Siberian larch from Siberia. No relationship could be established between natural durability of examined heartwoods and their water absorption behavior; however, strong correlation to the total amount of extractives was observed. Scots pine and Siberian larch heartwood from Siberia had 12.7 and 19.6% total extractives content respectively but the extractives composition differs. The study revealed also that lignin and monosaccharide content could not explain the variations in decay resistance of the studied heartwoods. No similarities in the natural durability revealed by laboratory and field tests were observed.     

Seasonal development of phloem in Siberian larch stems

The seasonal development of phloem in the stems of Siberian larch (Larix sibirica Ldb.) was studied over two seasons on 50–60-year-old trees growing in a natural stand in the Siberian forest-steppe zone. Trees at the age of 20–25 years were used to study metabolites in differentiating and mature phloem elements, cambial zone, and radially growing xylem cells in the periods of early and late wood formation. The development of the current-year phloem in the stems of 50–60-year-old trees started, depending on climatic conditions, in the second-third decades of May, 10–20 days before the xylem formation, and ended together with the shoot growth cessation in late July. Monitoring of the seasonal activity of cambium producing phloem sieve cells and the duration of their differentiation compared to the xylem derivatives in the cambium demonstrated that the top production of phloem and xylem cells could coincide or not coincide during the season, while their differentiation activity was always in antiphase. Sieve cells in the early phloem are separated from those in the late phloem by a layer of tannin-containing cells, which are formed in the period when late xylem formation starts. The starch content in the structural elements of phloem depends on the state of annual xylem layer development. The content of low molecular weight carbohydrates, amino acids, organic acids, and phenols in phloem cells, cambial zone, and xylem derivatives of the cambium depends on the cell type and developmental stage as well as on the type of forming wood (early or late) differing by the cell wall parameters and, hence, by the requirement for assimilates. Significant differences in the dynamics of substances per dry weight and cell were observed during cell development.     

Ammonites of Tethyan origin from the Ryazanian of the Russian platform: Genus <Emphasis Type="Italic">Riasanites</Emphasis> spath

The genus Riasanites, represented in Central Russia by two successive dimorphic species, is revised. R. swistowianus is found in the basal beds of the rjasanensis Zone. Its descendant R. rjasanensis is also found in this zone, but upwards in the section, including the beds with Surites spasskensis and Externiceras solowaticum. The representatives of Riasanites from the Crimea and Northern Caucasus are assigned to two species, R. crassicostatus and R. maikopensis, respectively. It is suggested that Riasanites evolved from Sub-Mediterranean Himalayatidae, which migrated from the Western Tethys via the Polish Passage into the Central Russian Basin, and from there to Mangyshlak, the Northern Caucasus, and the Crimea.