Effects of leaf litter and precipitation on germination and seedling survival of the endangered tree Beilschmiedia miersii

Question: What effects do leaf litter and rainfall regime have on seed germination (time and probability) and seedling survival of the endangered tree species Beilschmiedia miersii (Lauraceae)? Location: The species is a native tree from the mediterranean climate region of Chile. Seeds were collected from La Campana National Park (Chile). The study was carried out under controlled conditions at the Laboratory of Ecology, University of Chile, Santiago, Chile. Methods: During April 2001,200 seeds were assigned to four experimental treatments: high precipitation, with and without litter and low precipitation, with and without litter. Each treatment had 50 individual seeds, each seed in an individual pot. For statistical purposes, we considered each seed as one replicate. High and low values of artificial rainfall corresponded to mean dry and wet years, respectively, for the period 1958–1993 in the central zone of Chile. Results: Seeds germinated earlier, and in higher proportion, in the presence of leaf litter, but only under low rainfall. Seedling survival was insensitive to both litter and precipitation. Conclusions: We conclude that the presence of litter in native populations facilitates seed germination and recruitment of B. miersii, particularly during dry years. We suggest that the reduction of leaf litter due to extraction for gardens and horticultural activities might preclude regeneration of this endangered species.     

Deamidation drives molecular aging of the SARS-CoV-2 spike protein receptor-binding motif

The spike protein is the main protein component of the SARS-CoV-2 virion surface. The spike receptor-binding motif mediates recognition of the human angiotensin-converting enzyme 2 receptor, a critical step in infection, and is the preferential target for spike-neutralizing antibodies. Posttranslational modifications of the spike receptor-binding motif have been shown to modulate viral infectivity and host immune response, but these modifications are still being explored. Here we studied asparagine deamidation of the spike protein, a spontaneous event that leads to the appearance of aspartic and isoaspartic residues, which affect both the protein backbone and its charge. We used computational prediction and biochemical experiments to identify five deamidation hotspots in the SARS-CoV-2 spike protein. Asparagine residues 481 and 501 in the receptor-binding motif deamidate with a half-life of 16.5 and 123 days at 37 °C, respectively. Deamidation is significantly slowed at 4 °C, indicating a strong dependence of spike protein molecular aging on environmental conditions. Deamidation of the spike receptor-binding motif decreases the equilibrium constant for binding to the human angiotensin-converting enzyme 2 receptor more than 3.5-fold, yet its high conservation pattern suggests some positive effect on viral fitness. We propose a model for deamidation of the full SARS-CoV-2 virion illustrating how deamidation of the spike receptor-binding motif could lead to the accumulation on the virion surface of a nonnegligible chemically diverse spike population in a timescale of days. Our findings provide a potential mechanism for molecular aging of the spike protein with significant consequences for understanding virus infectivity and vaccine development.     

Dogs as a tool to improve bird-strike mortality estimates at wind farms

Management of avian populations near anthropogenic infrastructures, specifically wind farms, has been hampered due to biased bird fatalities estimates. Currently, these estimations are based on field surveys performed by humans, which is a method with low efficiency and accuracy. Detection dogs have been used for decades to assist humans, and their use for wildlife surveys is of increasing interest to scientists and wildlife managers. We evaluate the accuracy rates of human and dog-handler teams in real field conditions to address if dogs could be used instead of humans for bird carcass searches. Furthermore, to verify the efficiency of detection dogs (determined by the time spent to detect each bird carcass) searching for bird carcasses, we investigate the influence of several factors that affect the performance of dogs (carcass decomposition condition, distance to the target and weather conditions). Results indicate that dogs are more accurate than humans, independently of vegetation density. Furthermore, carcass decomposition condition, distances to the carcass and weather conditions significantly affect the efficiency of working dogs. The influence of these factors on detection time was minor. Results demonstrate the usefulness of dogs in field surveys to improve bird-strike mortality estimates at wind farms and other anthropogenic structures that cause bird fatalities worldwide.     

Perinatal asphyxia pathophysiology in pig and human: a review

In utero fetuses are evidently exposed to several factors that cause an interruption of the oxygen flow through the umbilical cord causing asphyxia leading to hypoxia and metabolic acidosis. These conditions are important causes of intra-partum and neonatal mortality. The main objective of this review is to provide current information regarding the pathophysiology of asphyxia in piglets around parturition; the physiological mechanisms invoked by affected piglets to compensate perinatal hypoxemia are discussed. This review also addresses some similarities and differences of asphyxia between piglets and other mammals, including human neonates. Metabolic acidosis and hypoxia are sequela to asphyxia and can cause profound health effects in postnatal performance because of an abnormal suckling, a reduced absorption of colostrum and inadequate passive transfer of neonatal immunity. Acidosis also cause hypothermia, increased mortality and reduced survival in neonates. One of the first deleterious effects of intrauterine hypoxia is the expulsion of meconium into the amniotic sac leading to meconium staining of the skin, and in severe cases, meconium aspiration into the lungs. Even though there have been technological changes and improvements in husbandry, piglet mortality due to asphyxia remains a major problem. One potential alternative to reduce neonatal mortality in pigs is the monitoring of fetal stress during birth and the implemention of strategies such as the Apgar score, that is often used in human pediatrics. It is also important to consider the physiological, behavioral and biochemical changes that take place during parturition which subsequently impact the vitality, maturity and development of neonatal pigs. Understanding the pathophysiology of fetal hypoxia should help practitioners and farmers implement more effective delivery techniques aimed at reducing neonatal mortality and improving postnatal performance.     

A new Ecuadorian species of the Andean fish genus Grundulus (Characiformes: Characidae)

The new species Grundulus quitoensis is described from El Voladero Lake, El Angel Biological Reserve, Northern Ecuador. The new taxon can be distinguished from all congeners by the following characters, respectively: a low number of unbranched rays in the anal fin (three vs. four-five) and in pectoral fins (on vs. two - three), a higher number of dentary teeth (12-14 vs. 8-10), a second infraorbital about three times larger than the first (vs. about two times larger), a third infraorbital which is not in contact with the preopercle (vs. in contact with preopercle), the presence of four small fenestrae in the infero-lateral bone dentary (vs. one - two); and a premaxilla which presents a long lateral process (vs. short), a maxilla with two notches in the infero-lateral surface (vs. one notch in the infero-lateral surface).     

Purification of a lipid-activated and Ca2+-independent protein kinase from the mantle tissue of Mytilus galloprovincialis Lmk.

A phospholipid-sensitive Ca²⁺-independent protein kinase (p105) was purified to homogeneity from mantle tissue of the mussel Mytilus galloprovincialis Lmk., employing consecutively DE-52 cellulose, Sephacryl S-200 and Biogel HTP chromatographies. The purified enzyme appeared as a single band on 10% SDS-PAGE, and had a molecular weight of 105 kDa.The positive Western blotting of the purified eluate for anti-human-PKC and PKC suggests that the enzyme from mussel mantle may be an ancestral nPKC isoform, with the kinetic properties of the enzyme very close to those of PKC isoform of vertebrates.Western blotting of samples from different steps of purification using specific mouse anti-p105, showed two protein bands in samples from the initial steps. However, only one band was detected in the Biogel-HTP eluate, the most purified fraction. The purification steps did not affect the presence of P-serine in p105. No P-tyrosine peptides were detected in any of the purification steps. These results open a new field of work on the study of several molecular processes related to energetic metabolism and reproduction in molluscs, whose regulation is associated with the activation of protein kinases.     

Genetic diversity and evolution of the human leptin locus tetranucleotide repeat

To better understand the evolutionary history of the gene region containing the multifunctional adipose tissue hormone leptin, we genotyped 1,957 individuals from 12 world populations for a highly variable tetranucleotide repeat polymorphism located 476 bp 3' of exon 3 of the leptin gene. Common alleles shared among populations, alleles specific to geographically defined populations, and the homologous alleles in the common and pygmy chimpanzee, the gorilla and the orangutan, were sequenced to define the allelic variation at the nucleotide level. These data reveal a common set of alleles shared among world populations, presumed to have arisen from a great ape ancestral allele prior to the divergence of the major geographical subdivisions of the human population, a subset of alleles specific to populations of African ancestry and a second set of alleles that arose by tandem duplication of the core repeat unit following the separation of African and non-African populations. These findings emphasize the complex evolutionary history of this locus and raise cautions about the pooling of alleles at this locus in association studies.