A COMPARED STUDY ON THE PURIFICATION OF FETAL AND ADULT RAT HEPATOCYTE SUSPENSIONS BY BIOMAGNETIC ISOLATION TECHNIQUES AND FLOW CYTOMETRY ANALYSIS

An analysis of liver cell populations from both adult and 21 day pregnancy rat fetuses (E21) was carried out. The results show that E21 hepatocytes express OX-43, as do endothelial cells but not adult hepatocytes. OX-43 could be used in future as a cell marker for the hepatocyte maturation.     

Additive main effect and multiplicative interaction model for a diallel-cross analysis

Diallel mating designs have proved informative in determining the inheritance of quantitative traits of interest to plant breeders. Apart from the well-established analyses of a complete diallel, the two-way factorial data structure of this design lends itself to analysis by the additive-main-effects-and-multiplicative-interaction (AMMI) model. This research article describes the joint application of the AMMI model and Griffing’s method 1, model I, to gain insight into the breeding value of inbred lines in a self-pollinated crop such as disomic, hexaploid bread wheat. Data from a multi-environment trial of a complete diallel cross between eight lines adapted to the East African highlands were analyzed to provide an example of this joint analysis. This combined approach identified not only the direction of a cross, i.e. which parent should be male or female, but also which crosses produce offspring showing F₁ heterosis. Received: 10 June 2000 / Accepted: 31 July 2000     

Tooth pulp tissue promotes neurite outgrowth from rat trigeminal ganglia in vitro

The mammalian tooth pulp becomes innervated by nociceptive and sympathetic axons relatively late during development, when part of the root has formed. In the adult, regenerating axons from an injured tooth nerve or sprouting axons from uninjured nerves in the vicinity rapidly reinnervate denervated tooth pulps. These observations indicate that tooth pulp tissue can use molecular factors to attract pulpal axons from local nerve trunks. The present study examines the hypothesis that these factors include nerve growth factor (NGF), brain derived neurotrophic factor (BDNF) and glial cell line derived neurotrophic factor (GDNF). Explants of trigeminal ganglia from neonatal rat pups showed a distinct neurite outgrowth when co-cultured with pulpal explants collected from molar teeth of 12-day old pups, or after application of a pulpal extract. Control cultures, containing single ganglionic explants, or explants co-cultured with heat-treated pulpal tissue, exhibited a sparse neurite outgrowth. Exogenous NGF and/or GDNF, but not exogenous BDNF, stimulated neurite outgrowth from ganglionic explants. Unexpectedly, application of antibodies against NGF, BDNF and/or GDNF to co-cultures of ganglionic and pulpal explants did not inhibit neuritogenesis. Control experiments showed that IgG molecules readily penetrate the gel used for culture and that even very high concentrations of NGF and GDNF antibodies in combination failed to block neurite growth. On the basis of these data we suggest that other as yet unknown neurite-promoting factors might be present and active in TG/pulpal co-cultures.     

ER-localized phosphatidylethanolamine synthase plays a conserved role in lipid droplet formation

The asymmetric distribution of phospholipids in membranes is a fundamental principle of cellular compartmentalization and organization. Phosphatidylethanolamine (PE), a nonbilayer phospholipid that contributes to organelle shape and function, is synthesized at several subcellular localizations via semiredundant pathways. Previously, we demonstrated in budding yeast that the PE synthase Psd1, which primarily operates on the mitochondrial inner membrane, is additionally targeted to the ER. While ER-localized Psd1 is required to support cellular growth in the absence of redundant pathways, its physiological function is unclear. We now demonstrate that ER-localized Psd1 sublocalizes on the ER to lipid droplet (LD) attachment sites and show it is specifically required for normal LD formation. We also find that the role of phosphatidylserine decarboxylase (PSD) enzymes in LD formation is conserved in other organisms. Thus we have identified PSD enzymes as novel regulators of LDs and demonstrate that both mitochondria and LDs in yeast are organized and shaped by the spatial positioning of a single PE synthesis enzyme.     

ESAT-6 (EsxA) and TB10.4 (EsxH) Based Vaccines for Pre- and Post-Exposure Tuberculosis Vaccination

The ESX systems from Mycobacterium tuberculosis are responsible for the secretion of highly immunogenic proteins of key importance for bacterial survival and growth. The two prototypic proteins, ESAT-6 (EsxA from ESX-1) and TB10.4 (EsxH from ESX-3) share a lot of characteristics regarding genome organization, size, antigenic properties, and vaccine potential but the two molecules clearly have very different roles in bacterial physiology. To further investigate the role of ESAT-6 and TB10.4 as preventive and post-exposure tuberculosis vaccines, we evaluated four different fusion-protein vaccines; H1, H4, H56 and H28, that differ only in these two components. We found that all of these vaccines give rise to protection in a conventional prophylactic vaccination model. In contrast, only the ESAT-6-containing vaccines resulted in significant protection against reactivation, when administered post-exposure. This difference in post-exposure activity did not correlate with a difference in gene expression during infection or a differential magnitude or quality of the vaccine-specific CD4 T cells induced by ESAT-6 versus TB10.4-containing vaccines. The post-exposure effect of the ESAT-6 based vaccines was found to be influenced by the infectious load at the time-point of vaccination and was abolished in chronically infected animals with high bacterial loads at the onset of vaccination. Our data demonstrate that there are specific requirements for the immune system to target an already established tuberculosis infection and that ESAT-6 has a unique potential in post-exposure vaccination strategies.     

From Mexico to Michigan and back: An international collaboration investigating primate behavior,ecology, and evolution from multiple perspectives

Evolutionary research benefits form the integration of laboratory and field components to determine factors and processes that affect the evolutionary trajectories of species. Our shared interest in understanding hybridization with genetic admixture as a process that may impact social, behavioral, and ecological features of primates, brought us together in a collaborative project aimed at addressing how vocal variation in two species of howler monkeys in Mexico affects and is affected by hybridization. To achieve this goal, we joined our academic expertise in studying primate genetics, ecology, and behavior under different natural and experimental conditions. We took advantage of decades of experience studying and handing wild howler monkeys for translocation projects to safely sample and study wild populations for this project. Here, we describe the history of our collaboration highlighting how our different perspectives, academic realities, and individual strengths built the foundation for our successful collaboration. We also share our perspectives on how this collaboration opened up new academic venues, broadened our individual perspectives on the integration of different research approaches to address a complex topic, and allowed us to recognize the strength of international collaboration.     

Depletion of the SR-Related Protein TbRRM1 Leads to Cell Cycle Arrest and Apoptosis-Like Death in Trypanosoma brucei

Arginine-Serine (RS) domain-containing proteins are RNA binding proteins with multiple functions in RNA metabolism. In mammalian cells this group of proteins is also implicated in regulation and coordination of cell cycle and apoptosis. In trypanosomes, an early branching group within the eukaryotic lineage, this group of proteins is represented by 3 members, two of them are SR proteins and have been recently shown to be involved in rRNA processing as well as in pre-mRNA splicing and stability. Here we report our findings on the 3rd member, the SR-related protein TbRRM1. In the present study, we showed that TbRRM1 ablation by RNA-interference in T. brucei procyclic cells leads to cell-cycle block, abnormal cell elongation compatible with the nozzle phenotype and cell death by an apoptosis-like mechanism. Our results expand the role of the trypanosomal RS-domain containing proteins in key cellular processes such as cell cycle and apoptosis-like death, roles also carried out by the mammalian SR proteins, and thus suggesting a conserved function in this phylogenetically conserved protein family.     

Fungal evolution: diversity,taxonomy and phylogeny of the Fungi

The fungal kingdom comprises a hyperdiverse clade of heterotrophic eukaryotes characterized by the presence of a chitinous cell wall, the loss of phagotrophic capabilities and cell organizations that range from completely unicellular monopolar organisms to highly complex syncitial filaments that may form macroscopic structures. Fungi emerged as a ‘Third Kingdom’, embracing organisms that were outside the classical dichotomy of animals versus vegetals. The taxonomy of this group has a turbulent history that is only now starting to be settled with the advent of genomics and phylogenomics. We here review the current status of the phylogeny and taxonomy of fungi, providing an overview of the main defined groups. Based on current knowledge, nine phylum‐level clades can be defined: Opisthosporidia, Chytridiomycota, Neocallimastigomycota, Blastocladiomycota, Zoopagomycota, Mucoromycota, Glomeromycota, Basidiomycota and Ascomycota. For each group, we discuss their main traits and their diversity, focusing on the evolutionary relationships among the main fungal clades. We also explore the diversity and phylogeny of several groups of uncertain affinities and the main phylogenetic and taxonomical controversies and hypotheses in the field.     

Notes on the diet of the critically endangered orange–fronted parakeet (Cyanoramphus malherbi) on Maud Island

Abstract

We conducted opportunistic observations on the diet of translocated orange-fronted parakeets (Cyanoramphus malherbi) on Maud Island to provide a first account of the diversity of food types ingested in the wild by this critically endangered species. Orange-fronted parakeets consumed fruits and leaves of 14 plant species as well as non–dietary items such as bark sticks and grit. Of dietary items, 96% were on plant species and 4% invertebrates. Of the plant species ingested 10% were non-natives. A major dietary component consisted of fruits and leaves of mahoe (Melicytus ramiflorus). In contrast to the only other published account of the diet of orange-fronted parakeets, invertebrates constituted a minor part of identified ingested items. This may be related to the different composition of vegetation at the study sites, the low parakeet population density during the time of our study and methodological restrictions during our survey. Our observations on undocumented food items add information about the biology of New Zealands’ rarest parakeet species and indicate dietary flexibility of the species highlighting the potential of other regenerating islands as release sites to expand the geographic distribution of orange–fronted parakeets.     

Effect of indigenous mycobiota on ochratoxin A production by Aspergillus carbonarius isolated from soil

This study determined the biotic interaction between 30 non-toxigenic indigenous strains of Aspergillus niger aggregate, Aspergillus flavus, Trichoderma spp., Mucor spp., Cladosporium spp., Ulocladium spp., Curvularia spp., Absidia spp., Geotrichum spp. and Acremonium spp., isolated from soil destined for maize crops, with respect to their ability to prevent ochratoxin A (OTA) production by A. carbonarius on “in vitro” assay, on liquid and solid medium. OTA production was completely inhibited when A. carbonarius was inoculated in a interactive mixed culture with all A. niger aggregate strains assayed, a 80 % of Trichoderma spp. strains, a 40 % of Cladosporium spp. strains, Acremonium spp and Geotrichum spp; only one strain of A. flavus tested was able to completely inhibit the mycotoxin accumulation. OTA production increased when A. carbonarius ACS 8 was growing on liquid interactive mixed culture with Mucor spp strains. These results demonstrated that OTA production by Aspergillua carbonarius strain was significantly influenced by the presence of different non-toxigenic fungal strains when growing together on paired cultures.