The right tool for the right question: contrasting biogeographic patterns in the notothenioid fish Harpagifer spp. along the Magellan Province.

Molecular-based analysis has become a fundamental tool to understand the role of Quaternary glacial episodes. In the Magellan Province in southern South America, ice covering during the last glacial maximum (20 ka) radically altered the landscape/seascape, speciation rates and distribution of species. For the notothenioid fishes of the genus Harpagifer, in the area are described two nominal species. Nevertheless, this genus recently colonized South America from Antarctica, providing a short time for speciation processes. Combining DNA sequences and genotyping-by-sequencing SNPs, we evaluated the role of Quaternary glaciations over the patterns of genetic structure in Harpagifer across its distribution in the Magellan Province. DNA sequences showed low phylogeographic structure, with shared and dominant haplotypes between nominal species, suggesting a single evolutionary unit. SNPs identified contrastingly two groups in Patagonia and a third well-differentiated group in the Falkland/Malvinas Islands with limited and asymmetric gene flow. Linking the information of different markers allowed us to infer the relevance of postglacial colonization mediated by the general oceanographic circulation patterns. Contrasting rough- and fine-scale genetic patterns highlights the relevance of combined methodologies for species delimitation, which, depending on the question to be addressed, allows discrimination among phylogeographic structure, discarding incipient speciation, and contemporary spatial differentiation processes.

Indoor radon exposure and excess of lung cancer mortality: the case of Mexico-an ecological study.

Radon is a radioactive gas that can migrate from soils and rocks and accumulate in indoor areas such as dwellings and buildings. Many studies have shown a strong association between the exposure to radon, and its decay products, and lung cancer (LC), particularly in miners. In Mexico, according to published surveys, there is evidence of radon exposure in large groups of the population, nevertheless, only few attention has been paid to its association as a risk factor for LC. The aim of this ecological study is to evaluate the excess risk of lung cancer mortality in Mexico due to indoor radon exposure. Mean radon levels per state of the Country were obtained from different publications and lung cancer mortality was obtained from the National Institute of Statistics, Geography and Informatics for the period 2001-2013. A model proposed by the International Commission on Radiological Protection to estimate the annual excess risk of LC mortality (per 105 inhabitants) per dose unit of radon was used. The average indoor radon concentrations found rank from 51 to 1863 Bq m-3, the higher average dose exposure found was 3.13 mSv year-1 in the north of the country (Chihuahua) and the mortality excess of LC cases found in the country was 10 ± 1.5 (range 1-235 deaths) per 105 inhabitants. The highest values were found mainly in the Northern part of the country, where numerous uranium deposits are found, followed by Mexico City, the most crowded and most air polluted area in the country. A positive correlation (r = 0.98 p < 0.0001) was found between the excess of LC cases and the dose of radon exposure. Although the excess risk of LC mortality associated with indoor radon found in this study was relatively low, further studies are needed in order to accurately establish its magnitude in the country.

Contrasting biogeographical patterns in Margarella (Gastropoda: Calliostomatidae: Margarellinae) across the Antarctic Polar Front.

Members of the trochoidean genus Margarella (Calliostomatidae) are broadly distributed across Antarctic and sub-Antarctic ecosystems. Here we used novel mitochondrial and nuclear gene sequences to clarify species boundaries and phylogenetic relationships among seven nominal species distributed on either side of the Antarctic Polar Front (APF). Molecular reconstructions and species-delimitation analyses recognized only four species: M. antarctica (the Antarctic Peninsula), M. achilles (endemic to South Georgia), M. steineni (South Georgia and Crozet Island) and the morphologically variable M. violacea (=M. expansa, M. porcellana and M. pruinosa), with populations in southern South America, the Falkland/Malvinas, Crozet and Kerguelen Islands. Margarella violacea and M. achilles are sister species, closely related to M. steineni, with M. antarctica sister to all these. This taxonomy reflects contrasting biogeographic patterns on either side of the APF in the Southern Ocean. Populations of Margarella north of the APF (M. violacea) showed significant genetic variation but with many shared haplotypes between geographically distant populations. By contrast, populations south of the APF (M. antarctica, M. steineni and M. achilles) exhibited fewer haplotypes and comprised three distinct species, each occurring across a separate geographical range. We hypothesize that the biogeographical differences may be the consequence of the presence north of the APF of buoyant kelps - potential long-distance dispersal vectors for these vetigastropods with benthic-protected development - and their near-absence to the south. Finally, we suggest that the low levels of genetic diversity within higher-latitude Margarella reflect the impact of Quaternary glacial cycles that exterminated local populations during their maxima.

Quaternary ice sheets and sea level regression drove divergence in a marine gastropod along Eastern and Western coasts of South America.

The southern coastline of South America is a remarkable area to evaluate how Quaternary glacial processes impacted the demography of the near-shore marine biota. Here we present new phylogeographic analyses in the pulmonate Siphonaria lessonii across its distribution, from northern Chile in the Pacific to Uruguay in the Atlantic. Contrary to our expectations, populations from the southwestern Atlantic, an area that was less impacted by ice during glacial maxima, showed low genetic diversity and evidence of recent expansion, similar to the patterns recorded in this study across heavily ice-impacted areas in the Pacific Magellan margin. We propose that Atlantic and Pacific shallow marine hard-substrate benthic species were both affected during the Quaternary in South America, but by different processes. At higher latitudes of the southeast Pacific, ice-scouring drastically affected S. lessonii populations compared to non-glaciated areas along the Chile-Peru province where the species was resilient. In the southwest Atlantic, S. lessonii populations would have been dramatically impacted by the reduction of near-shore rocky habitat availability as a consequence of glacio-eustatic movements. The increase of gravelly and rocky shore substrates in the southwest Atlantic supports a hypothesis of glacial refugia from where the species recolonized lower latitudes across the Atlantic and Pacific margins. Our results suggest that current patterns of genetic diversity and structure in near-shore marine benthic species do not solely depend on the impact of Quaternary glacial ice expansions but also on the availability of suitable habitats and life-history traits, including developmental mode, bathymetry and the likelihood of dispersal by rafting.

Lipid-based nanovesicles for nanomedicine.

Molecular self-assembly has enabled the fabrication of biologically inspired, advanced nanostructures as lipid-based nanovesicles (L-NVs). The oldest L-NVs, liposomes, have been widely proposed as potential candidates for drug delivery, diagnostic and/or theranostic applications and some liposome-based drug products have already stepped from the lab-bench to the market. This success is attributed to their ability to encapsulate both hydrophobic and/or hydrophilic molecules, efficiently carry and protect them within the body and finally deliver them at the target site. These positive features are also coupled with high biocompatibility. However, liposomes still present some unsolved drawbacks, such as poor colloidal stability, short shelf-life, restricted and expensive conditions of preparation because of the inherent nature of their fundamental constituents (phospholipids). The new tools available in the self-assembly of controlled molecules have significantly advanced the field of L-NV design and synthesis, and non-liposomal L-NVs have been recently developed; this new generation of nanovesicles can represent a paradigm shift in nanomedicine: they may complement liposomes, showing their advantages and overcoming most of their drawbacks. Clearly, being still young, their rocky way to the clinic first and then to the market has just started and it is still long, but they have all the potentialities to reach their objective target. The purpose of this review is to first present the large plethora of L-NVs available, focusing on this new generation of non-liposomal L-NVs and showing their similarities and differences with respect to their ancestors (liposomes). Since the overspread of a nanomaterial to the market is also strongly dependent on the availability of technological-scale preparation methods, we will also extensively review the current approaches exploited for L-NV production. The most cutting-edge approaches based on compressed fluid (CF) technologies will be highlighted here since they show the potential to represent a game-change in the production of L-NVs, favouring their step from the bench to the market. Finally, we will briefly discuss L-NV applications in nanomedicine, looking also for their future perspectives.

Arsenic and fluoride in the groundwater of Mexico.

Concentrations of arsenic and fluoride above Mexican drinking water standards have been detected in aquifers of various areas of Mexico. This contamination has been found to be mainly caused by natural sources. However, the specific processes releasing these toxic elements into groundwater have been determined in a few zones only. Many studies, focused on arsenic-related health effects, have been performed at Comarca Lagunera in northern México. High concentrations of fluoride in water were also found in this area. The origin of the arsenic there is still controversial. Groundwater in active mining areas has been polluted by both natural and anthropogenic sources. Arsenic-rich minerals contaminate the fractured limestone aquifer at Zimapán, Central México. Tailings and deposits smelter-rich fumes polluted the shallow granular aquifer. Arsenic contamination has also been reported in the San Antonio-El Triunfo mining zone, southern Baja California, and Santa María de la Paz, in San Luis Potosí state. Even in the absence of mining activities, hydrogeochemistry and statistical techniques showed that arsenopyrite oxidation may also contaminate water, as in the case of the Independencia aquifer in the Mexican Altiplano. High concentrations of arsenic have also been detected in geothermal areas like Los Azufres, Los Humeros, and Acoculco. Prevalence of dental fluorosis was revealed by epidemiological studies in Aguascalientes and San Luis Potosí states. Presence of fluoride in water results from dissolution of acid-volcanic rocks. In Mexico, groundwater supplies most drinking water. Current knowledge and the geology of Mexico indicate the need to include arsenic and fluoride determinations in groundwater on a routine basis, and to develop interdisciplinary studies to assess the contaminant's sources in all enriched areas.

Radioactive and stable metal bioaccumulation, crystalline compound and siderophore detection in Clavariadelphus truncatus.

137Cs and 40K activity concentrations and stable elements have been measured in Clavariadelphus truncatus collected in Mexico. Iron-chelating compounds of siderophore-type was also studied in the species. 137Cs and 40K were determined in soil and mushroom samples with HpGe gamma-ray spectrometry. Macro- and micro-elemental concentrations were determined by XRF and ICP-MS. Siderophore detection was obtained with a colorimetric assay and X-ray diffraction analysis was performed using a Siemens D5000 diffractometer. 137Cs geometric mean concentration in C. truncatus was 26 times higher as compared with other Mexican edible mushroom species, while 40K showed stability. Soil-C. truncatus concentration ratio for 137Cs and other micro-elements such as Cs, Rb and Pb were also higher than other Mexican edible species. The 137Cs committed effective dose due to the ingestion of C. truncatus was 8 x 10(-6) Sv year(-1). The main crystalline structure found in C. truncatus was D-Mannitol.

Environmental radon studies in Mexico.

Radon has been determined in soil, groundwater, and air in Mexico, both indoors and outdoors, as part of geophysical studies and to estimate effective doses as a result of radon exposure. Detection of radon has mainly been performed with solid-state nuclear track detectors (SSNTD) and, occasionally, with active detection devices based on silicon detectors or ionization chambers. The liquid scintillation technique, also, has been used for determination of radon in groundwater. The adjusted geometric mean indoor radon concentration (74 Bq m-3) in urban developments, for example Mexico City, is higher than the worldwide median concentration of radon in dwellings. In some regions, particularly hilly regions of Mexico where air pollution is high, radon concentrations are higher than action levels and the effective dose for the general population has increased. Higher soil radon levels have been found in the uranium mining areas in the northern part of the country. Groundwater radon levels are, in general, low. Soil-air radon contributing to indoor atmospheres and air pollution is the main source of increased exposure of the population.

In vitro toxicity of several dithiocarbamates and structure-activity relationships.

Dithiocarbamates (DTCs) are chemicals featuring a great chelating capacity. The toxicological study of DTCs is very important in view of their relatively simple synthesis and wide array of sanitary and industrial applications. In this study, the toxicity of some of the more recently synthesized DTCs is determined using an extremely simple bioassay, described in previous studies, based on the inhibition of growth of Escherichia coli (IGEC). The lowest-observed-effect concentration (LOEC), the median effective concentration (EC(50)) and no-observed-effect concentration (NOEC) of the following sodium dithiocarbamates was determined: N-benzyl-N-methyldithiocarbamate x 2H(2)O, N-benzyl-N-isopropyldithiocarbamate x 3H(2)O, N-benzyl-N-ethyldithiocarbamate x 2H(2)O, N-butyl-N-methyldithiocarbamate x 2H(2)O, N,N-dibenzyldithiocarbamate x 2H(2)O and N-benzyl-2-phenethyldithiocarbamate x 4H(2)O. Our results showed N,N-dibenzyl-DTC to be the least toxic of the tested substances, with an EC(50) value of 1,269.9 micro g ml(-1), whereas N-butyl-N-methyl-DTC and N-benzyl-N-methyl-DTC, with respective EC(50) values of 14.9 micro g ml(-1) and 23.5 micro g ml(-1), were the most toxic. Regression analysis showed, through exponential models, that the degree of toxicity of this group of substances correlated with the molecular weight of the compound, the molecular weight of the smallest chemical radical linked to the dithiocarbamate group and the number of benzene rings present in the molecule. The consideration of these models allows us to establish that in general terms the toxicity of DTCs decreases exponentially with a greater molecular weight and the number of benzene rings.

137Cs and relationships with major and trace elements in edible mushrooms from Mexico.

137Cs and 40K specific activity together with major and trace elements were determined in soil samples and in different edible wild mushroom species collected from a seminatural temperate forest ecosystem located in the central part of the Mexican Volcanic Belt. The activity measurements were made using a gamma-ray spectrometer system with a high purity germanium (HpGe) detector. The major and trace elements were determined using emission spectrography and mass spectrometry, respectively. The aggregated transfer factors for 137Cs were estimated in 30 local mushroom species collected from 1993 to 1999. Differences as large as three orders of magnitude were observed. The contribution of mushrooms for the total 137Cs dietary intake by the local population was estimated to be 37%. Mushrooms also showed to be good accumulators for Rb, Cu, Cs and Se.

Groundwater flow system in the valley of Toluca, Mexico: an assay of natural radionuclide specific activities.

Natural radionuclides and physicochemical parameters have been evaluated in groundwater samples from boreholes belonging to the drinking water supply system of the Toluca City, Mexico. The results obtained for radon and radium, together with the physicochemical parameters of the studied samples, indicate a fast and efficient recharge pattern. The presence of a local and a regional groundwater flows was also observed. The local flow belongs to shallower water, recognized by its low radon content and dissolved ions, as compared with the regional, deeper groundwater flow with a longer residence time.

Radiocesium accumulation in edible wild mushrooms from coniferous forests around the Nuclear Centre of Mexico.

Cs-137 and K-40 have been determined in soil samples and in wild edible mushrooms from a forest ecosystem located at the Nuclear Centre of Mexico (NCM) and in several surrounding localities. The transfer factors for Cs-137 were studied in 21 mushroom species from 1993 to 1997. The Cs-137 and K-40 determinations were performed using a gamma spectrometer system of low level counting with a high purity germanium (HPGe) detector. The local mushroom species that were found to show higher Cs-137 transfer factors were Clavariadelphus truncatus, Cortinarius caerulescens, Gomphus floccosus and Lyophyllum decastes. The Cs-137 levels obtained at the NCM in some mushroom samples were slightly lower than those from surrounding localities indicating that the nuclear facility has not emitted Cs-137 to the atmosphere.

Radon concentration levels in ground water from Toluca, Mexico.

Concentration levels of 222Rn have been analysed in water samples from deep wells of the aquifers around the City of Toluca, Mexico. The 222Rn source is the decay of 226Ra within the solid matrix of the aquifer. With a half life of 1600 years the 226Ra continuously releases 222Rn to the pores, from which it diffuses into the main body of water. This paper describes the methods used for sampling and measuring solubilized and 226Ra-supported 222Rn in the water samples, in order to evaluate possible health hazards due to the presence of radon in the drinking water supplies. The relationship of 222Rn with the hydrogeologic characteristics of the zone is also described. The analytical method involves laboratory extraction of 222Rn into toluene. Alpha disintegrations of 222Rn and contributions from short-lived daughters are counted by the liquid scintillation technique. The system was calibrated using a 226Ra standard solution. Results up to 11.3 Bq/l of 222Rn were obtained in the water samples.

S-adenosyl-L-methionine in the treatment of patients with intrahepatic cholestasis of pregnancy: a randomized, double-blind, placebo-controlled study with negative results.

S-Adenosyl-L-methionine has been reported to induce beneficial effects in intrahepatic cholestasis of pregnancy. Because cholestasis of pregnancy has a high prevalence in Chile and a deleterious effect on fetal prognosis, we decided to verify the efficacy of S-adenosyl-L-methionine in this disease. Eighteen patients with pruritus that appeared during pregnancy and with elevated serum levels of bile salts (68.1 +/- 15.9 mumol/L; mean +/- S.E.M.) and ALT (226 +/- 50 KU/L) were enrolled in a prospective double-blind study comparing the effects of the drug with a placebo. S-Adenosyl-L-methionine, 900 mg, or placebo was administered in daily intravenous infusions for 20 days. Every 5 days liver function tests were done and pruritus was assessed using a preestablished score. No significant differences in pruritus or in serum levels of bile salts, ALT, bilirubin and alkaline phosphatases were seen during or after treatment between patients who received S-adenosyl-L-methionine (n = 9) or placebo (n = 9). No relevant adverse reactions were detected. Most patients had cesarean sections because of reasons unrelated to the therapeutic trial. All newborns had Apgar scores greater than 7 and normal postnatal development. Our patients had moderately severe to severe cholestasis of pregnancy as indicated by the onset of pruritus before wk 32 of pregnancy. Seven of nine multiparous patients had a past history of recurrent cholestasis of pregnancy. In this study, the administration of S-adenosyl-L-methionine during 20 days did not improve intrahepatic cholestasis of pregnancy.

Intrahepatic cholestasis of pregnancy in twin pregnancies.

To clarify whether the increase in estrogen levels occurring during twin pregnancies (TP) is associated with a greater risk of developing intrahepatic cholestasis of pregnancy (ICP), we followed up 62 consecutive patients with TP and compared them with single pregnancies delivered in our hospital during 1 year. The prevalence of ICP was significantly higher in twin than in single pregnancies (20.9% versus 4.7%, respectively; P less than 0.001). Urinary estriol excretion was also significantly higher in twin compared to single pregnancies, although no quantitative differences were detected in TP with or without ICP. In multiparous patients with a proband TP affected by ICP, the disease recurred only in further TP, emphasizing the important role that estrogens seem to play in the pathogenesis of ICP. In contrast, in multiparous patients with a proband single pregnancy affected by ICP, the disease occurred in 70.5% of their other single pregnancies, suggesting the presence of a metabolic predisposition in these cases. However, in both groups of multiparous women a notable number of single pregnancies were not affected by the disease, supporting the postulate that the pathogenesis of ICP is multifactorial and that some as yet unidentified environmental factor needs to be present in order to develop the disease and also to modulate its expressivity.

Steatorrhea in patients with intrahepatic cholestasis of pregnancy.

A prospective study was undertaken to evaluate fat malabsorption during intrahepatic cholestasis of pregnancy (ICP), a disease characterized by a mild cholestasis of short duration appearing in otherwise healthy young women. An abnormal fecal fat excretion (mean 15.8 g/24 h, range 6-31 g/24 h) was demonstrated in 10 of 12 patients with the icteric form of ICP and in 2 of 11 patients with pruritus gravidarum. The increased fecal fat excretion was generally asymptomatic, could be detected as early as 3 wk after the clinical onset of ICP, remained stable during the affected pregnancies, and returned to normal from 3 to 9 wk after delivery. Steatorrhea correlated with the severity of ICP, estimated by serum levels of bilirubin, total bile salts, and glutamic pyruvic transaminase. A significant fall in the maternal weight/height index was detected after the onset of ICP, being more intense in patients with steatorrhea than in those without it (to 92.6% +/- 3.0% of initial values versus 96.7% +/- 2.8%, respectively; p less than 0.05). A high risk of premature deliveries and fetal distress was demonstrated in these patients, also correlating with the severity of ICP. No direct relationship could be established between steatorrhea or maternal nutritional impairment and fetal prognosis.

HLA in Chileans with intrahepatic cholestasis of pregnancy.

A possible association between intrahepatic cholestasis of pregnancy (ICP) and human-leukocyte histocompatibility (HLA) antigens--used as genetic markers--was studied in 100 women with ICP compared to 100 multiparous women without a past history of the disease. Because we previously found a higher frequency of ICP in women with an overt Araucanian Indian descent than in Chilean Caucasoids, women from both ethnic groups were studied. Among the 37 specificities of the HLA system studied (17 of HLA-A, 16 of HLA-B, and 4 of HLA-C series), only HLA-BW16 showed a tendency to be more frequent in women with ICP rather than in control women. This finding appears to be related with ethnic origin and not ICP, HLA-BW16 was significantly more frequent in women with Araucanian Indian descent (43.4%) than in Chilean Caucasoids (16.3%) (p less than 0.01). The high frequency of HLA-BW16 in the predominantly Caucasoid population in Chile, in comparison with Caucasians in Europe and in North America, may be another indicator of their ethnic admixture with aborigine groups. The high frequency of HLA-BW16 reported in North American Indian-admixed groups (16%) suggests that HLA-BW16 may be a genetic characteristic common to some aboriginal populations in North and South America.