Automated assessment reveals that the extinction risk of reptiles is widely underestimated across space and phylogeny

The Red List of Threatened Species, published by the International Union for Conservation of Nature (IUCN), is a crucial tool for conservation decision-making. However, despite substantial effort, numerous species remain unassessed or have insufficient data available to be assigned a Red List extinction risk category. Moreover, the Red Listing process is subject to various sources of uncertainty and bias. The development of robust automated assessment methods could serve as an efficient and highly useful tool to accelerate the assessment process and offer provisional assessments. Here, we aimed to (1) present a machine learning–based automated extinction risk assessment method that can be used on less known species; (2) offer provisional assessments for all reptiles—the only major tetrapod group without a comprehensive Red List assessment; and (3) evaluate potential effects of human decision biases on the outcome of assessments. We use the method presented here to assess 4,369 reptile species that are currently unassessed or classified as Data Deficient by the IUCN. The models used in our predictions were 90% accurate in classifying species as threatened/nonthreatened, and 84% accurate in predicting specific extinction risk categories. Unassessed and Data Deficient reptiles were considerably more likely to be threatened than assessed species, adding to mounting evidence that these species warrant more conservation attention. The overall proportion of threatened species greatly increased when we included our provisional assessments. Assessor identities strongly affected prediction outcomes, suggesting that assessor effects need to be carefully considered in extinction risk assessments. Regions and taxa we identified as likely to be more threatened should be given increased attention in new assessments and conservation planning. Lastly, the method we present here can be easily implemented to help bridge the assessment gap for other less known taxa.

The Red List of Threatened Species, published by the IUCN, is a crucial tool for conservation decision making, but is subject to various sources of uncertainty and bias. Modelling the threat status of all global reptiles identifies increased threat to many groups of reptiles across many regions of the world, beyond those currently recognized; moreover, it highlights the effects of the IUCN assessment procedure on eventual threat categories.     

In vivo modulation of brain cholesterol level and learning performance by a novel plant lipid: indications for interactions between hippocampal-cortical cholesterol and learning

In this account we report in vivo effects of a plant lipid preparation (MMPL) on brain cholesterol and the activity and learning performance of aging male rats. Three-month-old rats were fed for 3 months with a diet that was enriched with 3% MMPL. Another group of 18 month-old rats was fed for 6 months with a 3% MMPL-enriched diet. This food regime lowered markedly the cholesterol level in the hippocampal and cortical regions and increased their lipid membrane fluidity. The animals of both age groups also responded to MMPL with a higher activity and their learning performances, compared to normal diet-fed animals, improved notably. This improvement continued at least 4 months after terminating the supply of MMPL. Significant inverse correlationships were obtained between the length of the training period required to attain proper criteria and cholesterol levels of the hippocampal and cortical brain fractions.     

Beta-carotene from cassava (Manihot esculenta Crantz) leaves improves vitamin A status in rats

The bioavailability of beta-carotene from cassava (Manihot esculenta Crantz) leaves was assayed in vitamin A deficient Wistar rats (Rattus norvegicus). Rats were separated into three groups and fed with a modified AIN-93G--vitamin A deficient--diet. Deficient rat received this diet without any additional vitamin A source. Controls received the diet with 7200 microg of synthetic beta-carotene (control), while experimentals (test) received 19.5 g of cassava leaves powder per kg of diet. The cassava leaves with beta-carotene promotes similar growth and tissue weight in rats to the synthetic beta-carotene. The relative bioavailability, estimated as the Retinol Accumulation Factor (RAF), was 16.5 and 27.5 for control and test groups, respectively, indicating that control and test rats should have an intake of 16.5 microg or 27.5 microg of beta-carotene from synthetic form or cassava leaves powder for each 1 microg of hepatic retinol stored, respectively. The cassava leaves beta-carotene bioavailability was lower than the synthetic beta-carotene probably because the beta-carotene from the leaf matrix may be bounded to protein complex or inside organelles, which impair carotenoid absorption. Our findings showed that beside the hepatic retinol recovery, cassava leaf beta-carotene could maintain rat growth and avoid vitamin A deficient symptoms.     

ARL8 Relieves SKIP Autoinhibition to Enable Coupling of Lysosomes to Kinesin-1

1. Download : Download high-res image (156KB)
2. Download : Download full-size image

     

The crucial role of elasticity in regulating liquid–liquid phase separation in cells

Biomechanics and Modeling in Mechanobiology - Liquid–liquid phase separation has emerged as a fundamental mechanism underlying intracellular organization, with evidence for it being reported...     

Visualization of the F9 antigen on sperm from normal and T/t-complex mutants by immunoscanning electron microscopy

The antigens defined by conventional syngeneic antiserum against F9 embryonal carcinoma cells were localized on mature sperm using immunolabeling and scanning electron microscopy. Labeling patterns were compared for normal (+ / +) mice and mice bearing recessive t-haplotypes. The results showed that antigens detected by intact anti-F9 antiserum are expressed similarly in all genotypes, except for sperm from mice bearing the t¹²-haplotype where the frequency of labeled cells was reduced. Labeling with the IgM fraction of anti-F9 antiserum was lower on sperm from all t-genotypes examined, with sperm from + /t¹² males showing the most marked reduction. In all cases, the labeling patterns were similar, and included a labeling of the whole sperm head with complete anti-F9 antiserum and a restriction of the label to the postacrosomal region when the IgM fraction was used.     

Modification of d-amphetamine- or chlorpromazine-induced hypothermia by β-endorphin,MIF-I,and α-MSH: Mediation by the dopaminergic system

The effects of β-endorphin, MIF-I, and α-MSH on d-amphetamine- and CPZ-induced hypothermias in rats kept at 4°C were tested in three experimental groups: (a) intact; (b) rats with lesions of the olfactory tubercle; and (c) rats in which the link between the DA mesolimbic pathway and the striatum was disconnected. All drugs tested alone (except MIF-I) caused significant hypothermia. Pretreatment with CPZ, MIF-I, and α-MSH potentiated d-amphetamine-induced hypothermia in intact rats. Pretreatment with α-MSH potentiated CPZ-induced hypothermia. β-Endorphin partially blocked d-amphetamine-induced hypothermia, but did not interact with CPZ, MIF-I, or α-MSH. All potentiations were either reduced or disappeared in the incisioned rats. CPZ and α-MSH caused hypothermia in olfactory tubercle-lesioned rats. The results indicate that: (a) the DA mesolimbic pathway is involved in the hypothermic response of all drugs tested; (b) an intact feedback loop is required for the potentiation of the hypothermic response of CPZ on d-amphetamine, MIF-I on d-amphetamine, and α-MSH on d-amphetamine and CPZ; (c) β-endorphin acts as a partial blocker of d-amphetamine; MIF-I is a weak potentiator of d-amphetamine. α-MSH acts as a negative modulator of the DA system, most probably in the striatum.     

Dab2 inhibits the cholesterol-dependent activation of JNK by TGF-β

Transforming growth factor-β (TGF-β) ligands activate Smad-mediated and noncanonical signaling pathways in a cell context–dependent manner. Localization of signaling receptors to distinct membrane domains is a potential source of signaling output diversity. The tumor suppressor/endocytic adaptor protein disabled-2 (Dab2) was proposed as a modulator of TGF-β signaling. However, the molecular mechanism(s) involved in the regulation of TGF-β signaling by Dab2 were not known. Here we investigate these issues by combining biophysical studies of the lateral mobility and endocytosis of the type I TGF-β receptor (TβRI) with TGF-β phosphoprotein signaling assays. Our findings demonstrate that Dab2 interacts with TβRI to restrict its lateral diffusion at the plasma membrane and enhance its clathrin-mediated endocytosis. Small interfering RNA–mediated knockdown of Dab2 or Dab2 overexpression shows that Dab2 negatively regulates TGF-β–induced c-Jun N-terminal kinase (JNK) activation, whereas activation of the Smad pathway is unaffected. Moreover, activation of JNK by TGF-β in the absence of Dab2 is disrupted by cholesterol depletion. These data support a model in which Dab2 regulates the domain localization of TβRI in the membrane, balancing TGF-β signaling via the Smad and JNK pathways.     

Satiation differentially affects performance in a learning assay by nurse and forager honey bees

When not satiated prior to training, there were no differences between foragers and nurse honey bees in the acquisition of an appetitively based conditioned response in an olfactory associative learning assay, but when satiated foragers showed faster acquisition than did nurses. Satiation-related differences between foragers and nurses were more a function of behavioral state than age, because satiated precocious foragers also showed faster acquisition rates than did satiated nurse bees, despite their similar ages. Tests of sucrose responsiveness and retention of conditioned responses indicate that the observed performance differences between nurses and foragers were more likely due to differential sensitivity of sensory and motor processes related to satiation rather than differences in cognitive ability.