Cell attachment to collagen: The ionic requirements

This study is concerned with three aspects of the ionic requirements for cell attachment to collagen; namely (a) the divalent, (b) monovalent cation specificities and (c) pH optima for cell interaction with collagen. The divalent cation requirement for cell attachment to collagen can be sufficed by Ca²⁺, Mg²⁺ and certain transition group metals; whereas Ba²⁺, Sr²⁺, and polyamines are inactive. The pH optimum for cell attachment in this system occurs in the physiological range. The monovalent cation requirement for cell attachment to collagen is satisfied by isotonic NaCl, KCl, LiCl, NH₄Cl, sucrose, and glucose. Pronounced inhibition of cell attachment occurs under both hypertonic and hypotonic conditions.     

QTL mapping and confirmation for tolerance of anaerobic conditions during germination derived from the rice landrace Ma-Zhan Red

Wide adoption of direct-seeded rice practices has been hindered by poorly leveled fields, heavy rainfall and poor drainage, which cause accumulation of water in the fields shortly after sowing, leading to poor crop establishment. This is due to the inability of most rice varieties to germinate and reach the water surface under complete submergence. Hence, tolerance of anaerobic conditions during germination is an essential trait for direct-seeded rice cultivation in both rainfed and irrigated ecosystems. A QTL study was conducted to unravel the genetic basis of tolerance of anaerobic conditions during germination using a population derived from a cross between IR42, a susceptible variety, and Ma-Zhan Red, a tolerant landrace from China. Phenotypic data was collected based on the survival rates of the seedlings at 21 days after sowing of dry seeds under 10 cm of water. QTL analysis of the mapping population consisting of 175 F_2:3 families genotyped with 118 SSR markers identified six significant QTLs on chromosomes 2, 5, 6, and 7, and in all cases the tolerant alleles were contributed by Ma-Zhan Red. The largest QTL on chromosome 7, having a LOD score of 14.5 and an R ² of 31.7 %, was confirmed using a BC₂F₃ population. The QTLs detected in this study provide promising targets for further genetic characterization and for use in marker-assisted selection to rapidly develop varieties with improved tolerance to anaerobic condition during germination. Ultimately, this trait can be combined with other abiotic stress tolerance QTLs to provide resilient varieties for direct-seeded systems.     

Inheritance genetics of the trait vector competence in Frankliniella occidentalis (Western flower thrips) in the transmission of Tomato spotted wilt virus

The complexity of tospovirus–vector–host plant interaction is linked to a range of factors influencing vector's efficacy in virus transmission, leading to high variability in the transmission efficiency within vector populations. Main shortcomings of most studies are the missing information on the intrinsic potential of individual insects to serve as efficient vectors, both at phenotypic and at genotypic levels. Moreover, detailed analysis of vector competence heredity and monitoring the splitting of both genotypes and phenotypes in filial generations has not been reported. In this study, using the model system Frankliniella occidentalis and Tomato spotted wilt virus, we evaluated the inheritance and stability of the trait vector competence in a population through basic crossings of individually characterized partners, as well as virgin reproduction. We hypothesized that the trait is heritable in F. occidentalis and is controlled by a recessive allele. From the results, 83% and 94% of competent and noncompetent males respectively, inherited their status from their mothers. The trait was only expressed when females were homozygous for the corresponding allele. Furthermore, the allele frequencies were different between males and females, and the competent allele had the highest frequency in the population. These suggest that the trait vector competence is inherited in single recessive gene in F. occidentalis, for which the phenotype is determined by the haplodiploid mechanism. These findings are fundamental for our understanding of the temporal and spatial variability within vector populations with respect to the trait vector competence and at the same time offer an essential basis for further molecular studies.     

A phosphoramidon-sensitive metalloprotease induces apoptosis of human endothelial cells by Group B Streptococcus

We explored Group B Streptococcus (GBS)-induced apoptosis in human umbilical vein endothelial cells (HUVEC) and the role of phosphoramidon, a zinc metalloprotease inhibitor, in this process. GBS 90186 strain (serotype V, a blood isolate) and concentrated supernatant (CS) were used to investigate the viability and morphological alterations in HUVEC by Trypan blue uptake, electrophoresis in 2 % agarose gel and scanning electron microscopy assays. Apoptosis before and after phosphoramidon-treatment were verified by flow cytometry using annexin V-FITC labeling. Differences were considered significant when P < 0.05 using unpaired Student’s t test. GBS and CS induced HUVEC death by apoptosis (76.5 and 32 %, respectively) with an increasing pro-apoptotic Bax expression and decreasing anti-apoptotic Bcl-2 expression. Caspase-3 was activated during GBS-induced endothelial apoptosis. Phosphoramidon reduced 89.3 and 100 % of GBS and CS cell death by apoptosis, respectively. Some GBS strains may induce cell death by apoptosis with involvement of metalloproteases and signaling through the intrinsic pathway of apoptosis, which may contribute to GBS survival during sepsis of adults and neonates.     

Polymeric IgA1 controls erythroblast proliferation and accelerates erythropoiesis recovery in anemia

Anemia because of insufficient production of and/or response to erythropoietin (Epo) is a major complication of chronic kidney disease and cancer. The mechanisms modulating the sensitivity of erythroblasts to Epo remain poorly understood. We show that, when cultured with Epo at suboptimal concentrations, the growth and clonogenic potential of erythroblasts was rescued by transferrin receptor 1 (TfR1)-bound polymeric IgA1 (pIgA1). Under homeostatic conditions, erythroblast numbers were increased in mice expressing human IgA1 compared to control mice. Hypoxic stress of these mice led to increased amounts of pIgA1 and erythroblast expansion. Expression of human IgA1 or treatment of wild-type mice with the TfR1 ligands pIgA1 or iron-loaded transferrin (Fe-Tf) accelerated recovery from acute anemia. TfR1 engagement by either pIgA1 or Fe-Tf increased cell sensitivity to Epo by inducing activation of mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K) signaling pathways. These cellular responses were mediated through the TfR1-internalization motif, YXXΦ. Our results show that pIgA1 and TfR1 are positive regulators of erythropoiesis in both physiological and pathological situations. Targeting this pathway may provide alternate approaches to the treatment of ineffective erythropoiesis and anemia.     

Signaling of the neurotrophin receptor p75 in relation to Alzheimer’s disease

The cellular mechanism of neuronal apoptosis in Alzheimer’s disease (AD) is poorly understood. Many hypotheses have been put fourth to explain the underlying reason for neuro-degeneration in AD. Here, it is demonstrated that all neurotrophins that activated p75, without co-activation of the relevant Trk co-receptor, mediated apoptosis in hippocampal neurons. Thus, proneurotrophins and amyloid β peptides (Aβ) can induce p75-mediated apoptosis in hippocampal neurons since they do not bind or activate Trk receptors. Based on the combined effects of aging, proneurotrophins, neurotrophins, and Aβ, a novel model of pathogenesis in AD is proposed. This mini-review explores the ligand and cell type based signaling pathways of the neurotrophin receptor p75 relating to Alzheimer’s disease.