Persistence of Artemisia steppe in the Tangra Yumco Basin, west-central Tibet, China: despite or in consequence of Holocene lake-level changes?

The closed Tangra Yumco Basin underwent the strongest Quaternary lake-level changes so far recorded on the Tibetan Plateau. It was hitherto unknown what effect this had on local Holocene vegetation development. A 3.6-m sediment core from a recessional lake terrace at 4,700 m a.s.l., 160 m above the present lake level of Tangra Yumco, was studied to reconstruct Holocene flooding phases (sedimentology and ostracod analyses), vegetation dynamics and human influence (palynology, charcoal and coprophilous fungi analyses). Peat at the base of the profile proves lake level was below 4,700 m a.s.l. during the Pleistocene/Holocene transition. A deep-lake phase started after 11 cal ka BP, but the ostracod record indicates the level was not higher than similar to 4,720 m a.s.l. (180 m above present) and decreased gradually after the early Holocene maximum. Additional sediment ages from the basin suggest recession of Tangra Yumco from the coring site after 2.6 cal ka BP, with a shallow local lake persisting at the site until similar to 1 cal ka BP. The final peat formation indicates drier conditions thereafter. Persistence of Artemisia steppe during the Holocene lake high-stand resembles palynological records from west Tibet that indicate early Holocene aridity, in spite of high lake levels that may have resulted from meltwater input. Yet pollen assemblages indicate humidity closer to that of present potential forest areas near Lhasa, with 500-600 mm annual precipitation. Thus, the early mid-Holocene humidity was sufficient to sustain at least juniper forest, but Artemisia dominance persisted as a consequence of a combination of environmental disturbances such as (1) strong early Holocene climate fluctuations, (2) inundation of habitats suitable for forest, (3) extensive water surfaces that served as barriers to terrestrial diaspore transport from refuge areas, (4) strong erosion that denuded the non-flooded upper slopes and (5) increasing human influence since the late glacial.

The Peri-Implant Sulcus Compared with Internal Implant and Suprastructure Components: A Microbiological Analysis

Purpose: A recent in vivo study has shown considerable contamination of internal implant and suprastructure components with great biodiversity, indicating bacterial leakage along the implant-abutment interface, abutment-prosthesis interface, and restorative margins. The goal of the present study was to compare microbiologically the peri-implant sulcus to these internal components on implants with no clinical signs of peri-implantitis and in function for many years. Checkerboard DNA-DNA hybridization was used to identify and quantify 40 species. Material and Methods: Fifty-eight turned titanium Brånemark implants in eight systemically healthy patients (seven women, one man) under regular supportive care were examined. All implants had been placed in the maxilla and loaded with a screw-retained full-arch bridge for an average of 9.6 years. Gingival fluid samples were collected from the deepest sulcus per implant for microbiological analysis. As all fixed restorations were removed, the cotton pellet enclosed in the intra-coronal compartment and the abutment screw were retrieved and microbiologically evaluated. Results: The pellet enclosed in the suprastructure was very similar to the peri-implant sulcus in terms of bacterial detection frequencies and levels for practically all the species included in the panel. Yet, there was virtually no microbial link between these compartments. When comparing the abutment screw to the peri-implant sulcus, the majority of the species were less frequently found, and in lower numbers at the former. However, a relevant link in counts for a lot of bacteria was described between these compartments. Even though all implants in the present study showed no clinical signs of peri-implantitis, the high prevalence of numerous species associated with pathology was striking. Conclusions: Intra-coronal compartments of screw-retained fixed restorations were heavily contaminated. The restorative margin may have been the principal pathway for bacterial leakage. Contamination of abutment screws most likely occurred from the peri-implant sulcus via the implant-abutment interface and abutment-prosthesis interface.

An ice-core based history of Siberian forest fires since AD 1250

Forest fires play a key role in the global carbon cycle and thus, can affect regional and global climate. Although fires in extended areas of Russian boreal forests have a considerable influence on atmospheric greenhouse gas and soot concentrations, estimates of their impact on climate are hampered by a lack of data on the history of forest fires. Especially regions with strong continental climate are of high importance due to an intensified development of wildfires. In this study we reconstruct the fire history of Southern Siberia during the past 750 years using ice-core based nitrate, potassium, and charcoal concentration records from Belukha glacier in the continental Siberian Altai. A period of exceptionally high forest-fire activity was observed between AD 1600 and 1680, following an extremely dry period AD 1540-1600. Ice-core pollen data suggest distinct forest diebacks and the expansion of steppe in response to dry climatic conditions. Coherence with a paleoenvironmental record from the 200 km distant Siberian lake Teletskoye shows that the vegetational shift AD 1540-1680, the increase in fire activity AD 1600-1680, and the subsequent recovery of forests AD 1700 were of regional significance. Dead biomass accumulation in response to drought and high temperatures around AD 1600 probably triggered maximum forest-fire activity AD 1600-1680. The extreme dry period in the 16th century was also observed at other sites in Central Asia and is possibly associated with a persistent positive mode of the Pacific Decadal Oscillation (PDO). No significant increase in biomass burning occurred in the Altai region during the last 300 years, despite strongly increasing temperatures and human activities. Our results imply that precipitation changes controlled fire-regime and vegetation shifts in the Altai region during the past 750 years. We conclude that high sensitivity of ecosystems to occasional decadal-scale drought events may trigger unprecedented environmental reorganizations under global-warming conditions.

Mummies and skeletons from the Coptic monastery complex Deir el-Bachit in Thebes-west, Egypt

Deir el-Bachit is the largest known Coptic monastery complex in Thebes-West. It dates to the Late Antiquity period between the 6th and the beginning of the 10th century AD. So far, at least 26 individuals from the site were analysed anthropologically. 22 of them were excavated directly at the necropolis, the other 4 are special burials that were found at other locations nearby.Most individuals from the necropolis are male adults. There are two categories of human remains: “mummified” and “skeletonised”. The differences are probably due to social stratification. A substance similar to bitumen was found at the mummies. At that time, resin containing oils and bitumen were normally not used any more. One of the Special burials was an approximately three years old child which was found enclosed within a wall. Another special burial was a juvenile or young adult female who was found in the vault of an abandoned granary. The female was most likely pregnant and fell victim to a violent crime. This is indicated by the bones of a six months old foetus and an intravital skull fracture. She was no contemporary from the time the monastery was cultivated but was later deposited in this area.

The Mediterranean climate: An overview of the main characteristics and issues

The Mediterranean Region has many morphologic, geographical, historical, and societal characteristics, which make its climate scientifically interesting. The concept of Mediterranean climate is characterized by mild wet winters and warm to hot, dry summers and occur on the west side of continents between about 30° and 40° latitude. However, the presence of a relatively large mass of water is unique to the actual Mediterranean region. The Mediterranean Sea is a marginal and semi-enclosed sea; it is located on the western side of a large continental area and is surrounded by Europe to the North, Africa to the South, and Asia to the East. The chapter discusses that the climate of the Mediterranean region is to a large extent forced by planetary scale patterns. The time and space behavior of the regional features associated with such large-scale forcing is complex. Orography and land–sea distribution play an important role establishing the climate at basin scale and its teleconnections with global patterns. Different levels of services of readiness to emergencies, technological, and economic resources are likely to result in very different adaptation capabilities to environmental changes and new problems. The different economic situations and demographic trends are likely to produce contrasts and conflicts in a condition of limited available resources and environmental stress.

Silhouettella loricatula (Arachnida, Araneae, Oonopidae): a Haplogyne spider with complex female genitalia

The female genital system of the oonopid Silhouettella loricatula is astonishingly complex. The genital opening is situated medially and leads into an oval receptaculum that is heavily sclerotized except for the ventral half of the posterior wall that appears chitinized only. A large striking sclerite lying in the posterior wall of the uterus externus is attached anteriorly to the receptaculum and continues dorsally into a globular appendix that bears a furrow. The uterus externus shows a peculiar modification in its anterior wall: a paddle-like sclerite with a nail-like posterior process. This sclerite lies opposite to the furrow proceeding in the globular appendix and may serve females to lock the uterus externus by muscle contractions. Massive muscles connect the sclerite with the anterior scutum of the opisthosoma and with two other sclerites that are attached to the receptaculum and serve as attachments for further muscles. Gland cells extend around a pore field of the receptaculum. They produce secretion that encloses spermatozoa in a discrete package (secretory sac) inside the receptaculum. In this way, the mixing of sperm from different males and thus sperm competition may be severely limited or completely prevented. During a copulation in the laboratory the ejection of a secretory sac that most probably contained spermatozoa was observed, indicating sperm dumping in S. loricatula. The ejection of the secretory sac may be caused by female muscle contractions or by male pedipalp movements. The majority of the investigated females have microorganisms in the receptacula that could represent symbionts or infectious agents. The microorganisms can be identified partly as bacteria. They are enclosed in secretion and are always found in the same position inside the receptaculum.

Natale und neonatale Zähne

Natal teeth have been defined as teeth which are present at birth, while neonatal teeth erupt during the first 30 days. Their occurrence is rare, the prevalence ranges from 1:2000 to 1:3000 with a higher frequency in the lip and palate clefts and syndroms. In about 85% natal or neonatal teeth are lower central incisors (60% in pairs), rare are upper teeth, molars and multiple teeth. In almost 90% they are part of the deciduous dentition. A lot of possible causes of early eruption are discussed, but only the relation to hereditary factors seems to be evident. An autosomal dominant trait is often described. The appearance of these teeth is dependent on the degree of maturity, but most of the time it is loose, small, discoloured and hypoplastic. Histologically, enamel hypoplasia with normal prism structure is apparent. No significant disturbances of the dentin structures are observed, only cervically dentin becomes atubular with spaces and enclosed cells. A large vascular pulp and failure of root formation are further investigations. Our microhardness measurements showed values from 24.3-32.4 KHN for enamel and 48.3-62.2 KHN for dentin, while normal deciduous teeth have an enamel hardness of 322.0 +/- 17.5 KHN. The thickness of enamel was never more than 280 microm compared to up to 1200 microm in normal teeth. This shows the retarded development of natal and neonatal teeth, because mineralization has not finished at the time of birth. In accordance with developmental age tooth structure and appearence are normal. In consideration of complications as Riga-Fede-disease, feeding problems, possibility of infection and hypermobility most of the time extraction is the treatment of choice, but in the interest of protecting the child this decision should be made carefully.

Life and death partners: apoptosis, autophagy and the cross-talk between them

It is not surprising that the demise of a cell is a complex well-controlled process. Apoptosis, the first genetically programmed death process identified, has been extensively studied and its contribution to the pathogenesis of disease well documented. Yet, apoptosis does not function alone to determine a cell's fate. More recently, autophagy, a process in which de novo-formed membrane-enclosed vesicles engulf and consume cellular components, has been shown to engage in a complex interplay with apoptosis. In some cellular settings, it can serve as a cell survival pathway, suppressing apoptosis, and in others, it can lead to death itself, either in collaboration with apoptosis or as a back-up mechanism when the former is defective. The molecular regulators of both pathways are inter-connected; numerous death stimuli are capable of activating either pathway, and both pathways share several genes that are critical for their respective execution. The cross-talk between apoptosis and autophagy is therefore quite complex, and sometimes contradictory, but surely critical to the overall fate of the cell. Furthermore, the cross-talk is a key factor in the outcome of death-related pathologies such as cancer, its development and treatment.

HAMLET (human alpha-lactalbumin made lethal to tumor cells) triggers autophagic tumor cell death

HAMLET, a complex of partially unfolded alpha-lactalbumin and oleic acid, kills a wide range of tumor cells. Here we propose that HAMLET causes macroautophagy in tumor cells and that this contributes to their death. Cell death was accompanied by mitochondrial damage and a reduction in the level of active mTOR and HAMLET triggered extensive cytoplasmic vacuolization and the formation of double-membrane-enclosed vesicles typical of macroautophagy. In addition, HAMLET caused a change from uniform (LC3-I) to granular (LC3-II) staining in LC3-GFP-transfected cells reflecting LC3 translocation during macroautophagy, and this was blocked by the macroautophagy inhibitor 3-methyladenine. HAMLET also caused accumulation of LC3-II detected by Western blot when lysosomal degradation was inhibited suggesting that HAMLET caused an increase in autophagic flux. To determine if macroautophagy contributed to cell death, we used RNA interference against Beclin-1 and Atg5. Suppression of Beclin-1 and Atg5 improved the survival of HAMLET-treated tumor cells and inhibited the increase in granular LC3-GFP staining. The results show that HAMLET triggers macroautophagy in tumor cells and suggest that macroautophagy contributes to HAMLET-induced tumor cell death.

Building silent compartments at the nuclear periphery: a recurrent theme.

In eukaryotes, the genetic material is stored in the nucleus, which is enclosed in a double lipid bilayer, the nuclear envelope (NE). It protects the genome from physical stress and separates it from the rest of the cell. On top of this physical function, growing evidence shows that the nuclear periphery contributes to the 3D organization of the genome. In turn, tridimensional organization of chromatin in the nuclear space influences genome expression. Here we review recent findings on the function of this physical barrier in gene repression and latest models on how silent subnuclear compartments at the NE are built in yeast as well as in the nematode C. elegans and mammalian cells; trying to draw parallels between the three systems.

Integrated reconstruction of Holocene millennial-scale environmental changes in Tierra del Fuego, southernmost South America

This study presents new paleoenvironmental data obtained from sedimentary cores from Lago Fagnano, an elon- gated lake located at 54°S in southernmost South America. Data from palynomorphs (pollen, spores and algae) and associated palynofacies as well as from diatom taxa retrieved from these cores compared with other regional proxies contribute to evaluate the similarities and differences in the climate patterns based on different proxies from southernmost Patagonia. The pollen analysis reveals that a grass steppe environment existed during the early Holocene (11,300–~8000 cal a BP) followed by a major vegetation change characterized by development of forest-steppe ecotone communities between ~8000 and ~6500 cal a BP, under more humid conditions. Between ~ 6500 and ~ 4000 cal a BP, expansion and colonization by Nothofagus forests reflect an increase in effec- tive moisture levels, while openness in the forest communities characterizes the region after ~ 1100 cal a BP. The palynological organic matter combined with the algal content reflects hydrological changes occurring in the lake and its nutrient status, probably in close relation with past climate oscillations. All these past ecological changes are closely related to oscillations in precipitation and temperature as a response to the variations in the latitudinal position and/or strength of the Southern Westerlies wind belt during the Holocene.

Recent trends in Inner Asian forest dynamics to temperature and precipitation indicate high sensitivity to climate change

Semi-arid ecosystems play an important role in regulating global climate with the fate of these ecosystems in the Anthropocene depending upon interactions among temperature, precipitation, and CO2. However, in cool-arid environments, precipitation is not the only limitation to forest productivity. Interactions between changes in precipitation and air temperature may enhance soil moisture stress while simultaneously extending growing season length, with unclear consequences for net carbon uptake. This study evaluates recent trends in productivity and phenology of Inner Asian forests (in Mongolia and Northern China) using satellite remote sensing, dendrochronology, and dynamic global vegetation model (DGVM) simulations to quantify the sensitivity of forest dynamics to decadal climate variability and trends. Trends in photosynthetically active radiation fraction (FPAR) between 1982 and 2010 show a greening of about 7% of the region in spring (March, April, May), and 3% of the area ‘browning’ during summertime (June, July, August). These satellite observations of FPAR are corroborated by trends in NPP simulated by the LPJ DGVM. Spring greening trends in FPAR are mainly explained by long-term trends in precipitation whereas summer browning trends are correlated with decreasing precipitation. Tree ring data from 25 sites confirm annual growth increments are mainly limited by summer precipitation (June, July, August) in Mongolia, and spring precipitation in northern China (March, April, May), with relatively weak prior-year lag effects. An ensemble of climate projections from the IPCC CMIP3 models indicates that warming temperatures (spring, summer) are expected to be associated with higher summer precipitation, which combined with CO2 causes large increases in NPP and possibly even greater forest cover in the Mongolian steppe. In the absence of a strong direct CO2 fertilization effect on plant growth (e.g., due to nutrient limitation), water stress or decreased carbon gain from higher autotrophic respiration results in decreased productivity and loss of forest cover. The fate of these semi-arid ecosystems thus appears to hinge upon the magnitude and subtleties of CO2 fertilization effects, for which experimental observations in arid systems are needed to test and refine vegetation models.

Quantifying the turnover of transcriptional subclasses of HIV-1-infected cells

HIV-1-infected cells in peripheral blood can be grouped into different transcriptional subclasses. Quantifying the turnover of these cellular subclasses can provide important insights into the viral life cycle and the generation and maintenance of latently infected cells. We used previously published data from five patients chronically infected with HIV-1 that initiated combination antiretroviral therapy (cART). Patient-matched PCR for unspliced and multiply spliced viral RNAs combined with limiting dilution analysis provided measurements of transcriptional profiles at the single cell level. Furthermore, measurement of intracellular transcripts and extracellular virion-enclosed HIV-1 RNA allowed us to distinguish productive from non-productive cells. We developed a mathematical model describing the dynamics of plasma virus and the transcriptional subclasses of HIV-1-infected cells. Fitting the model to the data allowed us to better understand the phenotype of different transcriptional subclasses and their contribution to the overall turnover of HIV-1 before and during cART. The average number of virus-producing cells in peripheral blood is small during chronic infection. We find that a substantial fraction of cells can become defectively infected. Assuming that the infection is homogenous throughout the body, we estimate an average in vivo viral burst size on the order of 104 virions per cell. Our study provides novel quantitative insights into the turnover and development of different subclasses of HIV-1-infected cells, and indicates that cells containing solely unspliced viral RNA are a good marker for viral latency. The model illustrates how the pool of latently infected cells becomes rapidly established during the first months of acute infection and continues to increase slowly during the first years of chronic infection. Having a detailed understanding of this process will be useful for the evaluation of viral eradication strategies that aim to deplete the latent reservoir of HIV-1.