Middle Eocene chondrichthyan fauna from Antarctic Peninsula housed in the Museo de La Plata,Argentina

In recent years,the taxonomy and systematics of the cartilaginous fish taxa from the Eocene La Meseta Formation of Seymour(Marambio)Island,Antarctica have been extensively discussed in a series of papers,resulting in a complete revision of the Antarctic Eocene ichthyofauna housed in the Vertebrate Paleontology collection of the Museo de La Plata,Argentina.This collection constitutes one of the largest and taxonomically most diverse in the world,with approximately 20000 specimens,which provides a solid database used for the analysis of qualitative and quantitative chondrichthyan taxonomic composition.The information provided herein might be useful to understand the sudden decline in chondrichthyan taxonomic diversity towards the top of La Meseta Formation as well as its potential relationship with environmental changes during the Eocene.

Sudden openings and gradual closures in canopy cover modulate acclimation,survival,and growth of a shade-tolerant rainforest tree species

Forest disturbances at gap levels are one of the most important events for the regeneration and establishment of intermediate tree species.Abrupt canopy openings expose plants to high light intensity and high evaporative demands that stress shade-acclimated plants.Later,the slow closure of gaps reduces light availability to plants established when the incident irradiation was higher.This work evaluated the morphological and physiological acclimation of Cabralea canjerana(Vell)Mart.regeneration to sudden and to gradual changes in canopy cover.A pot experiment was carried out with plants exposed to a sudden opening.A few days after the light shock,plants rapidly increased photosynthetic rates and decreased leaf water potential.After two months,plants activated physiological responses at leaf and whole plant levels to high light and water stresses,e.g.,increased stoma-tal conductance,stomatal index and reduction of leaf:fine roots ratio and chlorophyll.After seven months,hydraulic conductivity of petioles and the whole leaf increased,and growth was much higher than plants that remained under the canopy.In a field experiment in gaps in the rainforest,plants acclimated to all canopy covers.Seven years after planting,growth was maximum in open environments within the gaps,even if the canopy closed during the first 20 months after planting.In conclusion,if this species is planted to enrich the rainforest,positions within gaps with lower canopy cover should be chosen and gap closure will not affect growth.To manage C.canjerana natural regeneration,the opening of gaps and removal of understory will increase survival and growth without the risk that the stress caused by these sudden openings could lead to the death of seedlings.Com-bining pot and field experiments helps to understand the autecology of trees with particular ecological interest,and to build sound restoration practices.

Evaluation of p53 codon 72 polymorphism in adenocarcinomas of the colon and rectum in La Plata, Argentina

AIM： To evaluate the potential association between p53 codon 72 polymorphism and sporadic colorectal adenocarcinoma development, and human papillornavirus （HPV） infection. METHODS： One-hundred and nine controls and 53 patients with colon cancer from the city of La Plata, Argentina were analyzed, p53 codon 72 genotypes and HPV infection were identified using allele-specific polymerase chain reaction and nested polymerase chain reaction, respectively. RESULTS： The differences in the distribution ofp53 codon 72 polymorphisrn between the cases and controls were statistically significant. The arginine allele had a prevalence of 0.65 in controls and 0.77 in cases. The corresponding odds ratio for the homozygous arginine genotype was 2.08 （95% CI, 1.06-4.05; P〈0.05）. Lack of association was found between ,053 polymorphism and HPV infection in the set of adenocarcinomas. CONCLUSION： The findings of the present study indicate that p53 codon 72 arginine homozygous genotype may represent a genetic predisposing factor for colon cancer development. However, further studies are needed in order to elucidate the role of p53 codon 72 polymorphism in colorectal cancer.

Fine‑tuning genomic and pedigree inbreeding rates in equine population with a deep and reliable stud book:the case of the Pura Raza Española horse

Background:Estimating inbreeding,which is omnipresent and inevitable in livestock populations,is a primary goal for management and animal breeding especially for those interested in mitigating the negative consequences of inbreeding.Inbreeding coefficients have been historically estimated by using pedigree information;however,over the last decade,genome-base inbreeding coefficients have come to the forefront in this field.The Pura Raza Espanola(PRE)horse is an autochthonous Spanish horse breed which has been recognised since 1912.The total PRE population(344,718 horses)was used to estimate Classical(F),Ballou’s ancestral,Kalinowski’s ancestral,Kalinowski’s new and the ancestral history coefficient values.In addition,genotypic data from a selected population of 805 PRE individuals was used to determine the individual inbreeding coefficient using SNP-by-SNP-based techniques(methods of moments-FHOM-,the diagonal elements of the genomic-FG-,and hybrid matrixes-FH-)and ROH measures(FRZ).The analyse of both pedigree and genomic based inbreeding coefficients in a large and robust population such as the PRE horse,with proven parenteral information for the last 40 years and a high degree of completeness(over 90%for the last 70 years)will allow us to understand PRE genetic variability better and the correlations between the estimations will give the data greater reliability.Results:The mean values of the pedigree-based inbreeding coefficients ranged from 0.01(F for the last 3 generations-F3-)to 0.44(ancestral history coefficient)and the mean values of genomic-based inbreeding coefficients varied from 0.05(FRZ for three generations,FH and FHOM)to 0.11(FRZ for nine generations).Significant correlations were also found between pedigree and genomic inbreeding values,which ranged between 0.58(F3 with FHOM)and 0.79(F with FRZ).In addition,the correlations between FRZ estimated for the last 20 generations and the pedigree-based inbreeding highlight the fact that fewer generations of genomic data are required when comparing total inbreeding values,and the opposite when ancient values are calculated.Conclusions:Ultimately,our results show that it is still useful to work with a deep and reliable pedigree in pedigreebased genetic studies with very large effective population sizes.Obtaining a satisfactory parameter will always be desirable,but the approximation obtained with a robust pedigree will allow us to work more efficiently and economically than with massive genotyping.

The first record of dermochelyid turtles in the Eocene of Tierra del Fuego:new insights on the evolution of the Weddellian faunas

The Antarctic Paleogene marine fossil record has been the key to reconstructing the evolution of the Weddellian Sea and final dismemberment of Southern Gondwana.In this context,Eocene marine vertebrates from Seymour(Marambio)Island have provided valuable information.We present the first Eocene record of marine reptiles from the southern Atlantic Coast of South America.This corresponds to several postcranial turtle remains represented by a proximal end of the right humerus,three caudal and one thoracic vertebrae,a fragment of the left pubis,and ten ossicles of the dorsal carapace,coming from the Leticia Formation(late-mid Eocene)at Cabo Tiburones,Tierra del Fuego,Argentina.These materials show severalfeatures such as the size and general morphology of the humerus and vertebrae,and the presence of relatively small,irregular,smooth,and unkeeled ossicles,which allow us to assign them to Dermochelyidae indet.Dermochelyids are a cosmopolitan group ofcryptodiran turtles,registered from the late Cretaceous up to the recent,with some physiological-biological peculiarities(e.g.,endothermy and an exclusive jellyfish-based diet)and characterized by the presence of an osseous carapace formed by ossicles.The new finding from the Leticia Formation is an addition to the scarce and extremely fragmentary record of Eocene dermochelyids from the southern seas like those from the La Meseta and Submeseta formations(Antarctica)and the Waihao and Burnside formations(New Zealand).This new information allows us to discuss the presence of these turtles in such high latitudes in the past and its implication in the evolution of the Weddellian fauna.

Coefficient Determination in Parabolic Equations Solved as a Moment Problem Two-Dimensional in a Rectangular Domain

The problem is to considerer a parabolic equation depending on a coefficient a (t), and find the solution of the equation and the coefficient. The objective is to solve the problem as an application of the inverse moment problem. An approximate solution and limits will be found for the error of the estimated solution using the techniques of inverse problem moments. In addition, the method is illustrated with several examples.

New insights into petrogenesis of Miocene magmatism associated with porphyry copper deposits of the Andean Pampean flat slab,Argentina

The Paramillos de Uspallata mining district located in the backarc region of the Pampean flat-slab segment(28°-33°S) features porphyry-type deposits genetically associated with Middle Miocene volcanics. This mineralizing magmatism comprising hydrothermally altered(sodic-calcic, potassic and phyllic alteration) subvolcanic and pyroclastic rocks of andesite-basaltic andesite and dacite-rhyolite composition with a typical arc signature, represents the eastward broadening of the Farellones arc by ~17 Ma. Its geochemistry also reveals a residual mineralogy of amphibole ± garnet with limited plagioclase fractionation resulting in an adakitic signal; however, according to the isotopic data collected in our study, the contributions of MASH(melting-assimilation-storage-homogenization) processes in the acquisition of this signal cannot be disregarded.Both the broadening of the Farellones arc and its residual mineralogy e typical of relatively deep magmatic chambers e are consistent with a slab shallowing and outcoming crustal thickening setting.This tectonic scenario could be interpreted as a result of an early effect of the Juan Fernandez Ridge collision that was further to the north by ~17 Ma. Our findings suggest that magmas were fertile for porphyry type deposits during the early stages of the slab shallowing.

Demographic Expansion and Contraction in a Neotropical Fish during the Late Pleistocene-Holocene

Demographic changes during the late Pleistocene-Holocene left signatures in the DNA of contemporary populations. These signatures reveal demographic phenomena like the increase or decrease in effective population size. In this paper we searched for signatures of demographic change in the DNA of the Neotropical freshwater fish Poecilia vivipara. Also, we investigated whether demographic changes are correlated with palaeoclimatic events of the late Pleistocene-Holocene, in particular, if changes in effective population size are correlated with expansion and contraction of available habitats, induced by global ice-volume changes and sea-level fluctuations. We used Bayesian Skyline Plot (BSP) analysis with sequences from the mitochondrial gene cytochrome b to estimate the ancestral demography of the Neotropical freshwater fish P. vivipara. To test the assumptions of neutrality and absence of population structure we used Tajima’s D and Spatial Analysis of Molecular Variance (SAMOVA), respectively. Effective population size of P. vivipara remained stable until 75,000 years ago, increased by 10-fold reaching a maximum at approximately 25,000 years ago, then suddenly declined at the Pleistocene-Holocene boundary. Variation in effective population size in P. vivipara correlates with expansion and contraction of habitats induced by sea-level fluctuations, caused by the advance and retreat of ice sheets during the Last Glacial Maximum (LGM).

Development of a Method for Identification and Quantification of Sulfadiazine and Pyrimethamine in Serum of Congenital Toxoplasmosis Pediatric Patients

Infection with Toxoplasma gondii, is one of the most widespread zoonoses in the world. Congenital Toxoplasmosis (CT) is particularly risky due to its fetal complications. Sulfadiazine (SDZ) and Pyrimethamine (PYR) are usually used for CT treatment in Argentina, to prevent morbidity. Due to the lack of commercial pediatric formulations, these must be prepared in the hospital pharmacy. This is the first report of serum concentrations measures in pediatric CT therapy for this combination of drugs. A bioanalytical method was developed for identification and simultaneous quantification of SDZ and PYR by High Performance Liquid Chromatography (HPLC) with UV detection. The validated method was applied to residual serum samples obtained from 6 pediatric patients undergoing treatment with SDZ 42.20 a 93.70 mg/kg/day and PYR 0.77 a 2.70 mg/kg/day. Sample pretreatment consisted on a deproteinization step followed by centrifugation and then injection of supernatant. Limit of Detection (LOD) and Quantification (LOQ) were (0.17 ± 0.02 and 0.13 ± 0.02) μg/mL and (0.46 ± 0.01 and 0.36 ± 0.01) μg/mL for SDZ and PYR respectively, with an appropriate linear range. Concentrations range found were ( - 162.04 ± 0.02) μg/mL for SDZ and ( - 7.30 ± 0.03) μg/mL for PYR. We developed and validated in real pediatric samples, an acute, precise and low-cost method for quantification of SDZ and PYR using a non-sophisticate chromatographic equipment, suitable for hospital therapeutic monitoring for public health system.

Long-term trends in the abundance and breeding performance in Adélie penguins:the Argentine Ecosystem Monitoring Program

In this work,we report long-term trends in the abundance and breeding performance of Adélie penguins(Pygoscelis adeliae)nesting in three Antarctic colonies(i.e.,at Martin Point,South Orkneys Islands;Stranger Point/Cabo Funes,South Shetland Islands;and Esperanza/Hope Bay in the Antarctic Peninsula)from 1995/96 to 2022/23.Using yearly count data of breeding groups selected,we observed a decline in the number of breeding pairs and chicks in crèche at all colonies studied.However,the magnitude of change was higher at Stranger Point than that in the remaining colonies.Moreover,the index of breeding success,which was calculated as the ratio of chicks in crèche to breeding pairs,exhibited no apparent trend throughout the study period.However,it displayed greater variability at Martin Point compared to the other two colonies under investigation.Although the number of chicks in crèche of Adélie penguins showed a declining pattern,the average breeding performance was similar to that reported in gentoo penguin colonies,specifically,those undergoing a population increase(even in sympatric colonies facing similar local conditions).Consequently,it is plausible to assume a reduction of the over-winter survival as a likely cause of the declining trend observed,at least in the Stranger Point and Esperanza colonies.However,we cannot rule out local effects during the breeding season affecting the Adélie population of Martin Point.

Review of the Cretaceous avian diversity of Antarctica:a changing scenario for the evolution of early Neornithine birds

The worldwide record of Cretaceous Neornithes and Neornithine-like birds is both controversial and poorly understood.However,in recent years,the Antarctic continent has yielded a substantial number of Maastrichtian avian specimens,contributing significantly to our understanding of the early evolution of this group.Simultaneously,the keen interest and collaborative efforts of various paleornithologists have resulted in a wealth of knowledge,which we have thoroughly reviewed,updated,and discussed in the context of recent discoveries.

Contributions to the knowledge of Antarctodon sobrali(Mammalia:Astrapotheria)from the Eocene of Antarctica

The Astrapotheria constitutes one of the five orders of extinct South American native ungulates,with a fossil record that also extends to the Eocene of the Antarctic Peninsula.In contrast to the abundant specimens known for litoptern Sparnotheriodontidae and metatherians,astrapotheres are represented by scant remains assigned to the endemic Antarctodon sobrali and indeterminate astrapotheres,restricted to levels 35C_(u0)and 35n of the Cucullaea I Allomember of the La Meseta Formation.The discovery of alower molar assignable to this species in the Eocene levels of Seymour(Marambio)Island,enables a revision of the diagnosis and the homologies of the dental characters used to describe this taxon.A reanalysis of its phylogenetic relationships reveals the nearly simultaneous presence of basal astrapotheres in the early Eocene of Itaboraí(Brazil),Patagonia,and West Antarctica.These taxa are characterized by lacking dental specializations usually associated with more abrasive diets like terminal forms of Uruguaytheriinae and Astrapotheriinae.Antarctodon appears to have thrived on the Antarctic continent during the Early Eocene Climatic Optimum within the paleoclimatic context of a hot-house world.Unlike present conditions in Antarctica where no terrestrial mammals inhabit,the early Eocene climate was characterized by warmer temperatures and a biologically diverse environment rich in primary producers,dominated by Nothofagus forests,encompassing both deciduous and evergreen forests,which supported a diverse assemblage of continental vertebrates.

Metformin revisited: Does this regulator of AMP-activated protein kinase secondarily affect bone metabolism and prevent diabetic osteopathy?

Patients with long-term type 1 and type 2 diabetes mellitus(DM) can develop skeletal complications or "diabetic osteopathy". These include osteopenia, osteoporosis and an increased incidence of low-stress fractures. In this context, it is important to evaluate whether current anti-diabetic treatments can secondarily affect bone metabolism. Adenosine monophosphateactivated protein kinase(AMPK) modulates multiple metabolic pathways and acts as a sensor of the cellular energy status; recent evidence suggests a critical role for AMPK in bone homeostasis. In addition, AMPK activation is believed to mediate most clinical effects of the insulin-sensitizer metformin. Over the past decade, several research groups have investigated the effects of metformin on bone, providing a considerable body of pre-clinical(in vitro, ex vivo and in vivo) as well as clinical evidence for an anabolic action of metformin on bone. However, two caveats should be kept in mind when considering metformin treatment for a patient with type 2 DM at risk for diabetic osteopathy. In the first place, metformin should probably not be considered an antiosteoporotic drug; it is an insulin sensitizer with proven macrovascular benefits that can secondarily improve bone metabolism in the context of DM. Secondly, we are still awaiting the results of randomized placebo-controlled studies in humans that evaluate the effects of metformin on bone metabolism as a primary endpoint.

Eucalyptus grandis plantations:effects of management on soil carbon,nutrient contents and yields

The expansion of fast-growing tree plantations is a worldwide process,with consequences on soil fertility and soil carbon storage.Disparate results were found on the effects of afforestation with Eucalyptus on soil carbon and other nutrient contents.These discrepancies are usually caused by differences in climate,land use history,soil texture as well as by management related factors such as plantation age,number of rotations,method of establishment(plantation or coppice),harvest residue management and soil preparation.We studied the effect of plantation age,number of rotations,and method of establishment on soils and plant nutrient concentrations in Eucalyptus grandis plantations in NE Argentina on different textured soils.We also determined if yields changed with nutrient variations in soils,and compared soils under plantations to soils under grasslands they replaced.Thirty-one E.grandis stands of different ages,number of rotations and method of establishment were evaluated as well as eight grassland sites.Levels of carbon,nitrogen,phosphorus,potassium,calcium and magnesium were determined for soils and plants.Soil carbon and nitrogen decreased over the number of rotations and were more pronounced in soils with 50-60%sand than soils with>75%sand.Coppice stands showed higher soil carbon and nitrogen levels than plantations,suggesting a negative effect of site preparation before planting on soil nutrient conservation,especially in fine-textured soils.Foliar nutrient concentrations did not follow the trends observed for soil nutrients nor did they reflect nutrient limitations.There was no evidence of decreased yields over successive rotations.Soil carbon and nitrogen contents decrease when grasslands are replaced by E.grandis plantations,and therefore a yield limitation may occur in a medium to long-term frame,especially in stands re-established for short-rotation management.Harvest residue management and site preparation must be specifically designed for improving soil nutrient management.

The Use of Chloride, Citric and Ascorbic Acid Dip and Packaged Film to Extend the Shelf Life of Pejerrey (<i>Odonthested bonaerensis</i>) during Storage at Different Temperatures

The objective of this study was to analyze the effect of chloride, citric and ascorbic acid dip treatments in conjunction with two types of packaging films (with high and low gas permeability) on microbial growth in samples of pejerrey fillets (Odonthestes bonaerensis) at three storage temperatures (4&#176;C, 0&#176;C and -1.5&#176;C). Colour, pH, texture modification and chemical changes were also studied. Psychrotrophic microorganisms, sp. were modelled by the Gompertz’ equation. Lag phase duration, specific growth rate and maximum population density were calculated. The activation energy (E&#181;) was calculated reaching values of 147 and 177 kJ/mol when the low permeability packaging films were employed. We used psychrotrophic microorganisms, sp., as a predictor of the shelf life of product. The application of treatment with chloride, citric and ascorbic acids, extended 1 - 2 days the storage life of the product (time to reach 106 CFU/g) when the packaging material used was polyethylene. The use of chloride, citric and ascorbic acids and vacuum packaging produced shelf life values of 7.7, >25 and >25 days at 4&#176;C, 0&#176;C and -1.5&#176;C respectively. The products had very good organoleptic characteristics, maintained their colour and texture appropriate, and absence of pathogenic microorganisms. These values indicated that the growth models were acceptable for expressing the growth of microorganisms on pejerrey fillets, which can be applied to ensure the safety of fish and to establish standards for avoiding microbial contamination.

Microbial oxidation of refractory gold sulfide concentrate by a native consortium

A defined mesophilic consortium including an iron oxidizing bacterium and a sulfur oxidizing bacterium was constructed to evaluate its ability for bioleaching a flotation concentrate from Andacollo mine in Neuquén,Argentina.Experiments were performed in shake flasks with a pulp density of10%(w/v),using a basal salt medium containing ferrous iron at pH1.8.The leaching solutions were analyzed for pH,redox potential(using specifics electrodes),ferrous iron(by UV-Vis spectrophotometry)and metal concentrations(by atomic absorption spectroscopy).The results showed that the consortium was able to reduce the refractory behavior of the concentrate,allowing91.6%of gold recovery;at the same time,high dissolution of copper and zinc was reached.These dissolutions followed a shrinking core kinetic model.According to this model,the copper solubilization was controlled by diffusion through a product layer(mainly jarosite),while zinc dissolution did not show a defined control step.This designed consortium,composed of bacterial strains with specific physiological abilities,could be useful not only to optimize gold recovery but also to decrease the leachates metallic charge,which would be an environmental advantage.

The fossil record of Antarctic land mammals:commented review and hypotheses for future research

The fossil record of terrestrial mammals in Antarctica is temporally and geographically constrained to the Eocene outcrops of La Meseta and Submeseta formations in Seymour(Marambio)Island in West Antarctica.The faunal assemblage indicates a clear South American imprint since all the groups have a close phylogenetic relationship with Cretaceous and Paleogene mammals from Patagonia.Despite the presence of several mammalian taxonomic groups:Dryolestida,Gondwanatheria,Eutheria and Metatheria,the presence of other major mammalian taxa should be expected and will probably be confirmed by new findings.Placental mammals with an inferred body mass between 10 to 400 kg in size,are represented by xenarthrans,and two groups of the so called South American native ungulates:Astrapotheria and Litopterna.The Metatheria are the smaller(less than 1 kg)and most abundant components of the fauna.Marsupials are represented by derorhynchid ameridelphians,several microbiotherian australidelphians(both microbiotheriids and woodburnodontids),and?glasbiid prepidolopod and polydolopid polydolopimorphians.Plus,there are remains of several mammalian teeth of indeterminate phylogenetic affinities.The present knowledge of the Southern Hemisphere mammalian evolution and paleogeographic change through time,indicates that Antarctica played a major role for land mammals,at least since the Jurassic.The actual representation of Paleogene terrestrial mammals in Antarctica is most probably biased,as all the evidence indicates that australosphenidan mammals should be present in this continent since the Jurassic.

The westward lithospheric drift,its role on the subduction and transform zones surrounding Americas:Andean to cordilleran orogenic types cyclicity

We investigate the effect of the westerly rotation of the lithosphere on the active margins that surround the Americas and find good correlations between the inferred easterly-directed mantle counterflow and the main structural grain and kinematics of the Andes and Sandwich arc slabs.In the Andes,the subduction zone is shallow and with low dip,because the mantle flow sustains the slab;the subduction hinge converges relative to the upper plate and generates an uplifting doubly verging orogen.The Sandwich Arc is generated by a westerly-directed SAM(South American) plate subduction where the eastward mantle flow is steepening and retreating the subduction zone.In this context,the slab hinge is retreating relative to the upper plate,generating the backarc basin and a low bathymetry single-verging accretionary prism.In Central America,the Caribbean plate presents a more complex scenario:(a) To the East,the Antilles Arc is generated by westerly directed subduction of the SAM plate,where the eastward mantle flow is steepening and retreating the subduction zone.(b) To the West,the Middle America Trench and Arc are generated by the easterly-directed subduction of the Cocos plate,where the shallow subduction caused by eastward mantle flow in its northern segment gradually steepens to the southern segment as it is infered by the preexisting westerly-directed subduction of the Caribbean Plateau.In the frame of the westerly lithospheric flow,the subduction of a divergent active ridge plays the role of introducing a change in the oceanic/continental plate’s convergence angle,such as in NAM(North American)plate with the collision with the Pacific/Farallon active ridge in the Neogene(Cordilleran orogenic type scenario).The easterly mantle drift sustains strong plate coupling along NAM,showing at Juan de Fuca easterly subducting microplate that the subduction hinge advances relative to the upper plate.This lower/upper plate convergence coupling also applies along strike to the neighbor continental strike slip fault systems where subduction was terminated(San Andreas and Queen Charlotte).The lower/upper plate convergence coupling enables the capture of the continental plate ribbons of Baja California and Yakutat terrane by the Pacific oceanic plate,transporting them along the strike slip fault systems as para-autochthonous terranes.This Cordilleran orogenic type scenario,is also recorded in SAM following the collision with the Aluk/Farallon active ridge in the Paleogene,segmenting SAM margin into the eastwardly subducting Tupac Amaru microplate intercalated between the proto-LiquineOfqui and Atacama strike slip fault systems,where subduction was terminated and para-autochthonous terranes transported.In the Neogene,the convergence of Nazca plate with respect to SAM reinstalls subduction and the present Andean orogenic type scenario.

Antarctic Paleontological Heritage:Late Cretaceous–Paleogene vertebrates from Seymour(Marambio)Island,Antarctic Peninsula

Antarctica has significant environmental,scientific,historic,and intrinsic values,all of which are worth protecting into the future.This continent has a discrete number of places of scientific interest that exhibit great potential as natural heritage sites;its geodiversity is of fundamental importance to scientific values of the continent,and the pursuit of geological and paleontological knowledge has had a strong influence on its historical values.Seymour Island was once called the‘Rosetta Stone’of Southern Hemisphere paleobiology,because this small island provides the most complete and richly fossiliferous Late Cretaceous–Paleogene sequence in Antarctica.In particular,fossil vertebrates form part of the evidence used in reconstructing the history of life on Antarctica.Paleontological heritage is considered a subset of geo-heritage that embodies both natural and historical components which has received only indirect recognition.Seymour Island is an outstanding paleontological area with high heritage value of its Late Cretaceous/Paleogene vertebrates and should be considered for geo-conservation and protection.This paper reviews vertebrate fossil occurrences and outcrops on Seymour Island and discusses some threats to these fossil sites.

Has Stewart approach improved our ability to diagnose acid-base disorders in critically ill patients?

The Stewart approach-the application of basic physicalchemical principles of aqueous solutions to blood-is an appealing method for analyzing acid-base disorders. These principles mainly dictate that p H is determined by three independent variables, which change primarily and independently of one other. In blood plasma in vivo these variables are:(1) the PCO2;(2) the strong ion difference(SID)-the difference between the sums of all the strong(i.e., fully dissociated, chemically nonreacting) cations and all the strong anions; and(3) the nonvolatile weak acids(Atot). Accordingly, the p H and the bicarbonate levels(dependent variables) are only altered when one or more of the independent variables change. Moreover, the source of H+ is the dissociation of water to maintain electroneutrality when the independent variables are modified. The basic principles of the Stewart approach in blood, however, have been challenged in different ways. First, the presumed independent variables are actually interdependent as occurs in situations such as:(1) the Hamburger effect(a chloride shift when CO2 is added to venous blood from the tissues);(2) the loss of Donnan equilibrium(a chloride shift from the interstitium to the intravascular compartment to balance the decrease of Atot secondary to capillary leak; and(3) the compensatory response to a primary disturbance in either independent variable. Second, the concept of water dissociation in response to changes in SID is controversial and lacks experimental evidence. In addition, the Stewart approach is not better than the conventional method for understanding acid-base disorders such as hyperchloremic metabolic acidosis secondary to a chloride-rich-fluid load. Finally, several attempts were performed to demonstrate the clinical superiority of the Stewart approach. These studies, however, have severe methodological drawbacks. In contrast, the largest study on this issue indicated the interchangeability of the Stewart and conventional methods. Although the introduction of the Stewart approach was a new insight into acid-base physiology, the method has not significantly improved our ability to understand, diagnose, and treat acid-base alterations in critically ill patients.