Late Holocene volcanic and anthropogenic mercury deposition in the western Central Andes (Lake Chungará, Chile).

Volcanism is one of the major natural processes emitting mercury (Hg) to the atmosphere, representing a significant component of the global Hg budget. The importance of volcanic eruptions for local-scale Hg deposition was investigated using analyses of Hg, inorganic elemental tracers, and organic biomarkers in a sediment sequence from Lake Chungará (4520 m a.s.l.). Environmental change and Hg deposition in the immediate vicinity of the Parinacota volcano were reconstructed over the last 2700 years, encompassing the pre-anthropogenic and anthropogenic periods. Twenty eruptions delivering large amounts of Hg (1 to 457 µg Hg m-2 yr-1 deposited at the timescale of the event) were locally recorded. Peaks of Hg concentration recorded after most of the eruptions were attributed to a decrease in sedimentation rate together with the rapid re-oxidation of gaseous elemental Hg and deposition with fine particles and incorporation into lake primary producers. Over the study period, the contribution of volcanic emissions has been estimated as 32% of the total Hg input to the lake. Sharp depletions in primary production occurred at each eruption, likely resulting from massive volcaniclastic inputs and changes in the lake-water physico-chemistry. Excluding the volcanic deposition periods, Hg accumulation rates rose from natural background values (1.9 ±â€¯0.5 µg m-2 yr-1) by a factor of 2.3 during the pre-colonial mining period (1400-900 yr cal. BP), and by a factor of 6 and 7.6, respectively, during the Hispanic colonial epoch (400-150 yr cal. BP) and the industrial era (~140 yr cal. BP to present). Altogether, the dataset indicates that lake primary production has been the main, but not limiting, carrier for Hg to the sediment. Volcanic activity and climate change are only secondary drivers of local Hg deposition relative to the magnitude of regional and global anthropogenic emissions.

[Systematic literature review on patient safety in medical departments]. / Revisión sistemática de la literatura acerca de la seguridad de los pacientes hospitalizados en servicios médicos.

UNLABELLED: Patient safety is an issue of interest. All scenarios of health care have a risk of adverse events (AE) and determination of its incidence has been reported in virtually all medical specialties. OBJECTIVE: To determine the incidence reported in the medical literature of adverse events in medical departments. DESIGN AND METHODS: An exhaustive search of biomedical databases using different strategies, search in high impact journals and a manual search of related articles. RESULTS: We reviewed 17,437 entries. After reading the abstracts and articles, and applying previously defined inclusion and exclusion criteria, we selected 10 articles that reported the incidence of adverse events in medical departments. Most studies corresponded to a historical cohort, had used an AE screening to identify high risk patients, and had used a structured review to check clinical records. None of them had as their ultimate objective to report on the impact of adverse events or characterize them. The incidence reported in medical departments ranged from 3.6% to 21.7%. The definitions of adverse events and forms of detection were similar; however the few differences put the comparability at risk. CONCLUSION: No studies were aimed at quantifying or characterising the adverse events in health care. None of them defined what constitutes a medical department, although the results reported are within the published values for health systems. Further research is needed in this area.

Development of an experimental ovarian tumor: immunocytochemical analysis.

OBJECTIVE: The aim of the present work was to study whether immunocytochemical parameters present in the normal ovary were altered after tumor development under high gonadotropin levels. METHODS: Ovarian tumors (luteoma): castrated female rats had an ovary grafted into the spleen; tumors were left to develop for 1, 2, 3 or 7 months. The presence of apoptotic cells (TUNEL method) and the expression of proliferating cell nuclear antigen (PCNA), gap junction protein (Cx43), steroidogenic acute regulatory protein (StAR), aromatase and synaptosome-associated protein of 25 kDa (SNAP-25) were determined by immunocytochemistry. Some of these findings were confirmed by RT-PCR (Cx43, StAR, SNAP-25). Inhibin subunit mRNAs were investigated by Northern blot. RESULTS: PCNA staining of tumors was mainly found in granulosa cells of transforming follicles and was absent from luteinized follicles. A nearly complete absence of apoptosis was observed. Cx43 was mainly found in follicles, while it was very weakly expressed or absent in luteinized follicles. StAR protein expression, indicating active steroidogenesis, was demonstrated only in luteinized follicles and in thecal cells, but was absent from granulosa cells. Aromatase immunoreactivity was very intense in granulosa and also present in luteal cells. Membrane-associated and cytoplasmic SNAP-25 immunostaining was determined in patches of endocrine cells in the follicles, as well as in the luteinized follicles. The expression of mRNAs for Cx43, StAR and SNAP-25 (RT-PCR) and inhibin subunits (Northern blots) were confirmed in 1-, 3- and 7-month-old tumors. CONCLUSIONS: These results indicated that luteoma most likely develop from unruptured follicles by hypertrophy and proliferation of follicular cells. Circulating gonadotropins seem to play a fundamental role in maintaining the expression of proteins typically expressed in normal ovary, while avoiding apoptosis in this tissue.

Tropical climate changes at millennial and orbital timescales on the Bolivian Altiplano.

Tropical South America is one of the three main centres of the global, zonal overturning circulation of the equatorial atmosphere (generally termed the 'Walker' circulation). Although this area plays a key role in global climate cycles, little is known about South American climate history. Here we describe sediment cores and down-hole logging results of deep drilling in the Salar de Uyuni, on the Bolivian Altiplano, located in the tropical Andes. We demonstrate that during the past 50,000 years the Altiplano underwent important changes in effective moisture at both orbital (20,000-year) and millennial timescales. Long-duration wet periods, such as the Last Glacial Maximum--marked in the drill core by continuous deposition of lacustrine sediments--appear to have occurred in phase with summer insolation maxima produced by the Earth's precessional cycle. Short-duration, millennial events correlate well with North Atlantic cold events, including Heinrich events 1 and 2, as well as the Younger Dryas episode. At both millennial and orbital timescales, cold sea surface temperatures in the high-latitude North Atlantic were coeval with wet conditions in tropical South America, suggesting a common forcing.

The history of South American tropical precipitation for the past 25,000 years.

Long sediment cores recovered from the deep portions of Lake Titicaca are used to reconstruct the precipitation history of tropical South America for the past 25,000 years. Lake Titicaca was a deep, fresh, and continuously overflowing lake during the last glacial stage, from before 25,000 to 15,000 calibrated years before the present (cal yr B.P.), signifying that during the last glacial maximum (LGM), the Altiplano of Bolivia and Peru and much of the Amazon basin were wetter than today. The LGM in this part of the Andes is dated at 21,000 cal yr B.P., approximately coincident with the global LGM. Maximum aridity and lowest lake level occurred in the early and middle Holocene (8000 to 5500 cal yr B.P.) during a time of low summer insolation. Today, rising levels of Lake Titicaca and wet conditions in Amazonia are correlated with anomalously cold sea-surface temperatures in the northern equatorial Atlantic. Likewise, during the deglacial and Holocene periods, there were several millennial-scale wet phases on the Altiplano and in Amazonia that coincided with anomalously cold periods in the equatorial and high-latitude North Atlantic, such as the Younger Dryas.

Sources and function of neuronal signalling molecules in the gonads.

While the hypothalamic-pituitary-gonadal axis is crucial for the function of the gonads, non-endocrine regulatory influences are exerted by other factors within the gonads. Among these factors are neurotransmitters, such as catecholamines. Several types of receptors for catecholamines exist in the gonads on vascular or endocrine cells. Their activation can alter blood flow, steroidogenesis and gene expression, depending on the target cells. Recently a neuronal-like cell type expressing catecholamine-biosynthetic enzymes and neuronal proteins was identified in testis and ovary of human and non-human primates. Together with the well-known sympathetic innervation, this gonadal nervous system may serve as a source of catecholamines. Dopamine is present in the follicular fluid. Oocytes, while not able to perform de novo synthesis of catecholamines, were shown to utilize dopamine to produce norepinephrine. This catecholamine then acts on beta-adrenoreceptors of follicular cells to increase cAMP. Oocytes may thus indirectly via dopamine and cAMP be able to control their own meiotic arrest. In addition, neurotransmitters may also be synthesized in other, non-neuronal ovarian cells. Thus, cultured human granulosa-luteal cells possess the acetylcholine synthesizing enzyme and the acetylcholine-specific vesicular transporter protein. These cells also express muscarinic-receptors (M1), which are linked to the mobilization of intracellular calcium and cell proliferation. This suggests involvement of the acetylcholine system in follicular growth and in the periovulatory events. In neurons, neurotransmitters alter the properties of the neuronal cell membrane. If this is the case in endocrine cells of the gonads is not yet clear, but the recent identification of voltage-activated potassium and sodium channels in human luteinized granulosa-luteal cells raises this question and opens a door to a new area of investigation.