Plant species with extremely small populations (PSESP) in China: A seed and spore biology perspective

Approximately one fifth of the world's plants are at risk of extinction. Of these, a significant number exist as populations of few individuals, with limited distribution ranges and under enormous pressure due to habitat destruction. In China, these most-at-risk species are described as ‘plant species with extremely small populations’ (PSESP). Implementing conservation action for such listed species is urgent. Storing seeds is one of the main means of ex situ conservation for flowering plants. Spore storage could provide a simple and economical method for fern ex situ conservation. Seed and spore germination in nature is a critical step in species regeneration and thus in situ conservation. But what is known about the seed and spore biology (storage and germination) of at-risk species? We have used China's PSESP (the first group listing) as a case study to understand the gaps in knowledge on propagule biology of threatened plant species. We found that whilst germination information is available for 28 species (23% of PSESP), storage characteristics are only known for 8% of PSESP (10 species). Moreover, we estimate that 60% of the listed species may require cryopreservation for long-term storage. We conclude that comparative biology studies are urgently needed on the world's most threatened taxa so that conservation action can progress beyond species listing.     

Crystal structure and thermal characterization of cadmium oxalate [CdC2O4 · 3H2O] and barium-doped cadmium oxalate [Ba0.5Cd0.5(C2O4)2 · 5H2O] single crystals grown in silica gel

Pure cadmium oxalate trihydrate (COT) and barium added cadmium oxalate (BCO) single crystals were grown by controlled diffusion of Cd²⁺ and Ba²⁺ ions in silica gel at ambient temperature. A single test tube technique coupled with gel aging conferred maximum size crystals by controlling the nucleation rate. It was found that the pH and age of the gel greatly influenced the crystal quality, their size and transparency. Grown crystals CdC₂O₄ · 3H₂O and Ba_0.5Cd_0.5(C₂O₄)₂ · 5H₂O were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and thermal analysis. Effect of barium dopant on the growth and morphology of cadmium oxalate was studied. Pure cadmium oxalate crystallized in triclinic system and the barium-doped cadmium oxalate crystallized in hexagonal system with massive changes in their unit cell parameters. The infrared spectrum revealed the presence of oxalate ligands and water of hydration in both the pure and barium-doped crystals. Thermal analysis showed that the grown crystals were dehydrated thermally even from lower temperatures and the doped crystals were found more stable.     

Immune-Mediated Competition in Rodent Malaria Is Most Likely Caused by Induced Changes in Innate Immune Clearance of Merozoites

Malarial infections are often genetically diverse, leading to competitive interactions between parasites. A quantitative understanding of the competition between strains is essential to understand a wide range of issues, including the evolution of virulence and drug resistance. In this study, we use dynamical-model based Bayesian inference to investigate the cause of competitive suppression of an avirulent clone of Plasmodium chabaudi (AS) by a virulent clone (AJ) in immuno-deficient and competent mice. We test whether competitive suppression is caused by clone-specific differences in one or more of the following processes: adaptive immune clearance of merozoites and parasitised red blood cells (RBCs), background loss of merozoites and parasitised RBCs, RBC age preference, RBC infection rate, burst size, and within-RBC interference. These processes were parameterised in dynamical mathematical models and fitted to experimental data. We found that just one parameter , the ratio of background loss rate of merozoites to invasion rate of mature RBCs, needed to be clone-specific to predict the data. Interestingly, was found to be the same for both clones in single-clone infections, but different between the clones in mixed infections. The size of this difference was largest in immuno-competent mice and smallest in immuno-deficient mice. This explains why competitive suppression was alleviated in immuno-deficient mice. We found that competitive suppression acts early in infection, even before the day of peak parasitaemia. These results lead us to argue that the innate immune response clearing merozoites is the most likely, but not necessarily the only, mediator of competitive interactions between virulent and avirulent clones. Moreover, in mixed infections we predict there to be an interaction between the clones and the innate immune response which induces changes in the strength of its clearance of merozoites. What this interaction is unknown, but future refinement of the model, challenged with other datasets, may lead to its discovery.     

Biophysical Characteristics of Successful Oilseed Embryo Cryoprotection and Cryopreservation Using Vacuum Infiltration Vitrification: An Innovation in Plant Cell Preservation

Heterogeneity in morphology, physiology and cellular chemistry of plant tissues can compromise successful cryoprotection and cryopreservation. Cryoprotection is a function of exposure time × temperature × permeability for the chosen protectant and diffusion pathway length, as determined by specimen geometry, to provide sufficient dehydration whilst avoiding excessive chemical toxicity. We have developed an innovative method of vacuum infiltration vitrification (VIV) at 381 mm (15 in) Hg (50 kPa) that ensures the rapid (5 min), uniform permeation of Plant Vitrification Solution 2 (PVS2) cryoprotectant into plant embryos and their successful cryopreservation, as judged by regrowth in vitro. This method was validated on zygotic embryos/embryonic axes of three species (Carica papaya, Passiflora edulis and Laurus nobilis) up to 1.6 mg dry mass and 5.6 mm in length, with varying physiology (desiccation tolerances) and 80°C variation in lipid thermal profiles, i.e., visco-elasticity properties, as determined by differential scanning calorimetry. Comparisons between the melting features of cryoprotected embryos and embryo regrowth indicated an optimal internal PVS2 concentration of about 60% of full strength. The physiological vigour of surviving embryos was directly related to the proportion of survivors. Compared with conventional vitrification, VIV-cryopreservation offered a ∼ 10-fold reduction in PVS2 exposure times, higher embryo viability and regrowth and greater effectiveness at two pre-treatment temperatures (0°C and 25°C). VIV-cryopreservation may form the basis of a generic, high throughput technology for the ex situ conservation of plant genetic resources, aiding food security and protection of species from diverse habitats and at risk of extinction.     

An Evaluation of the Impact of PD‐1 Pathway Blockade on Reproductive Safety of Therapeutic PD‐1 Inhibitors

This report discusses the principles of reproductive toxicity risk assessment for biopharmaceuticals blocking the PD‐1/programmed cell death ligand 1 (PD‐L1) pathway, which have been developed for the treatment of patients with advanced malignancies. The PD‐1/PD‐L1 pathway is a T‐cell co‐inhibitory pathway that normally maintains immune tolerance to self. Its role in pregnancy is to maintain immune tolerance to the fetal allograft. In cancer patients, this signaling pathway is hijacked by some neoplasms to avoid immune destruction. PD‐1/PD‐L1‐blocking agents enhance functional activity of the target lymphocytes to eventually cause immune rejection of the tumor. A therapeutic blockade of PD‐1/PD‐L1 pathway that occurs at full target engagement provides a unique challenge to address the risk to pregnancy because disruption of the same pathway may also reduce or abrogate maternal immune tolerance to the fetal alloantigens inherited through the father. Typically, nonclinical reproductive and developmental toxicity (DART) studies in animals (rats and rabbits) with clinical drug candidates are conducted to identify potential risk in humans and to determine exposure margin for the effects on reproduction as part of the risk assessment. However, for biopharmaceuticals for which the desired mechanism of action cannot be separated from potential deleterious effects to the fetus and when the only relevant toxicology species is nonhuman primate (NHP), the risk to reproduction can be predicted by a mechanism‐based assessment using data generated from murine surrogate models as supportive information without conducting DART in NHPs. Such an approach has been used in the evaluation of pregnancy risk of anti‐PD‐1 agent, pembrolizumab, and has been demonstrated as an important alternative to performing DART studies in NHPs     

Fructose diphosphate aldolase from Mycobacterium smegmatis. Purification and properties.

Fructose diphosphate aldolase has been purified to homogeneity from Mycobacterium smegmatis. Physicochemical studies showed that the enzyme is a tetramer of molecular weight 158,000. Mycobacterium smegmatis aldolase, though a bacterial enzyme, possesses properties similar to other class I aldolases. Inactivation of the enzyme by sodium borohydride in presence of dihydroxyacetone phosphate suggested the formation of a Schiff-base intermediate.     

Identification of avian vasotocin receptor subtype-specific antagonists involved in the stress response of the chicken,Gallus gallus

Vasotocin 1a and 1b receptors (V1aR and V1bR) have been shown to play important roles in the neuroendocrine regulation of stress responses via the anterior pituitary (AP) of birds. To identify effective subtype-specific antagonists for the chicken V1aR (cV1aR) and cV1bR, potential antagonists to the mammalian V1R were screened against the cV1aR and cV1bR 3D structural models by molecular docking analysis with determination of binding pocket/amino acid residues involved in the interaction. The antagonistic effects of the selected ligands were examined by measuring pro-opiomelanocortin (POMC) heteronuclear RNA (hnPOMC) levels following the in vitro stress administration to primary chicken AP cells. Results of in silico analysis showed that the Manning compound and several other antagonists were bound to cV1bR with higher affinity than the natural agonist, arginine vasotocin (AVT). Similarities and differences in the antagonist-receptor binding interface with receptors were characterized for each ligand. Non-peptide mammalian V1bR antagonists, SSR-149415 and L-368899, were shown to be effective and had an additive effect in blocking POMC hnRNA expression in pituitary cell culture studies. SR-49059 antagonized the effect(s) of AVT/CRH on the downregulation of the cV1aR and the upregulation of the cCRH-R2 expression but not the cV1bR and cCRH-R1. The Manning compound antagonized the downregulation of cV1aR, cV1bR and cCRH-R1 and the upregulation of cCRH-R2 expression. The specificity of antagonists apparently resulted from unique differences in the interacting residues and their binding affinities. Collectively, these results provide valuable leads for future development of novel compounds capable of blocking or attenuating the AP stress response of avian species and perhaps other non-mammalian vertebrates as well.