Body mass estimation for †Cyonasua (Procyonidae,Carnivora) and related taxa based on postcranial skeleton

Procyonidae were the first northern placental carnivorans that reached the Neotropics. They are represented by two extinct genera: ?Cyonasua and ?Chapalmalania (late Miocene – early Pleistocene). Postcranial elements are only known for ?Cyonasua and related taxa (?Parahyaenodon argentinus and ?Tetraprothomo argentinus). To obtain highly reliable allometric equations for body mass estimations of fossil procyonids, we performed least squares regressions (multiple and bivariate lineal models) using 51 postcranial linear measurements. The extant sample included 124 taxa corresponding to nine families of Carnivora, with body mass data from the literature. We obtained about 63 equations from diverse combinations of postcranial measurements; 14 of them were selected using several reliability indexes as criteria. Our results show that body masses calculated for ?Cyonasua range between 12.63 and 28.45 kg, ?P. argentinus was estimated at 14.41 kg, while ?T. argentinus at 25.31 kg. Thus, the body mass of ?Cyonasua would have been at least twice as high as the mean of the extant procyonid Procyon cancrivorus. ?Cyonasua was probably able to fend off predators and quite capable of climbing slowly on thick-enough branches. Other palaeoecological and palaeobiological inferences are discussed.     

Nitrogen Cycling of Active Bacteria within Oligotrophic Sediment of the Mid-Atlantic Ridge Flank

Microbial ecology within oligotrophic marine sediment is poorly understood, yet is critical for understanding geochemical cycles. Here, 16S rRNA sequences from RNA and DNA inform the structure of active and total microbial communities in oligotrophic sediment on the western flank of the Mid-Atlantic Ridge. Sequences identified as Bacillariophyta chloroplast were detected within DNA, but undetectable within RNA, suggesting preservation in 5.6-million-year-old sediment. Statistical analysis revealed that RNA-based microbial populations correlated significantly with nitrogen concentrations, whereas DNA-based populations did not correspond to measured geochemical analytes. Bioenergetic calculations determined which metabolisms could yield energy in situ, and found that denitrification, nitrification, and nitrogen fixation were all favorable. A metagenome was produced from one sample, and included genes mediating nitrogen redox processes. Nitrogen respiration by active bacteria is an important metabolic strategy in North Pond sediments, and could be widespread in the oligotrophic sedimentary biosphere.     

GKAP, a Novel Synaptic Protein That Interacts with the Guanylate Kinase-like Domain of the PSD-95/SAP90 Family of Channel Clustering Molecules

The molecular mechanisms underlying the organization of ion channels and signaling molecules at the synaptic junction are largely unknown. Recently, members of the PSD-95/SAP90 family of synaptic MAGUK (membrane-associated guanylate kinase) proteins have been shown to interact, via their NH₂-terminal PDZ domains, with certain ion channels (NMDA receptors and K⁺ channels), thereby promoting the clustering of these proteins. Although the function of the NH₂-terminal PDZ domains is relatively well characterized, the function of the Src homology 3 (SH3) domain and the guanylate kinase-like (GK) domain in the COOH-terminal half of PSD-95 has remained obscure. We now report the isolation of a novel synaptic protein, termed GKAP for guanylate kinase-associated protein, that binds directly to the GK domain of the four known members of the mammalian PSD-95 family. GKAP shows a unique domain structure and appears to be a major constituent of the postsynaptic density. GKAP colocalizes and coimmunoprecipitates with PSD-95 in vivo, and coclusters with PSD-95 and K⁺ channels/ NMDA receptors in heterologous cells. Given their apparent lack of guanylate kinase enzymatic activity, the fact that the GK domain can act as a site for protein– protein interaction has implications for the function of diverse GK-containing proteins (such as p55, ZO-1, and LIN-2/CASK).     

The evolution of self-fertilization in perennials

Abstract Many plants are perennials, but studies of self-fertilization do not usually include features of perennial life histories. We therefore develop models that include selfing, a simple form of perenniality, adult inbreeding depression, and an adult survivorship cost to seed production. Our analysis shows that inbreeding depression in adults diminishes the genetic transmission advantage associated with selfing, especially in long-lived perennials that experience inbreeding depression over many seasons. Perennials also pay a cost when selfing increases total seed set at the expense of future survivorship and reproduction. Such life-history considerations shed new light on the generalization that annuals self-fertilize more than perennials. Past research suggested reproductive assurance as an explanation for this association, but common modes of selfing offer equal reproductive assurance to annuals and perennials. Instead, perennials may avoid selfing because of adult inbreeding depression and the cost to future survivorship and reproduction.     

Manganese metabolism is impaired in the Belgrade laboratory rat

Homozygous Belgrade rats have a hypochromic anaemia due to impaired iron transport across the cell membrane of immature erythroid cells. This study aimed at investigating whether there are also abnormalities of Mn metabolism in erythroid and other types of cells. The experiments were performed with homozygous (b/b) and heterozygous (+/b) Belgrade rats and Wistar rats and included measurements of Mn uptake by reticulocytes in vitro, Mn absorption from in situ closed loops of the duodenum, and plasma clearance and uptake by several organs after intravenous injection of radioactive Mn bound to transferrin (Tf ) or mixed with serum. Similar measurements were made with ⁵⁹Fe-labelled Fe in several of the experiments. Mn uptake by reticulocytes and absorption from the duodenum was impaired in b/b rats compared with +/b or Wistar rats. The plasma clearance of Mn-Tf was much slower than Mn-serum, but both were faster than the clearance of Fe-Tf. Uptake of ⁵⁴Mn by the kidneys, brain and femurs was less in b/b than Wistar or +/b rats, but uptake by the liver was greater in b/b rats. Similar differences were found for ⁵⁹Fe uptake by kidneys, brain and femurs but ⁵⁹Fe uptake by the liver was also impaired in the liver. It is concluded that the genetic abnormality present in b/b rats affects Mn metabolism as well as Fe metabolism and that Mn and Fe share similar transport mechanisms in the cells of erythroid tissue, duodenal mucosa, kidney and blood-brain barrier. Accepted: 20 February 1997     

Immunocytochemical identification of metallothionein- positive cells in rheumatoid synovium and analysis of their cell lineage

Metallothionein is a ubiquitous low molecular weight metalloprotein with powerful protective properties against oxygen radical-mediated cytotoxicity associated with inflammatory processes. In rheumatoid arthritis, the inflammatory damage to the synovium appears to be mediated by free radicals released by the high concentration of neutrophils found in the synovial fluid of the inflamed joint. Synovial tissue obtained during routine surgery on rheumatoid and non-rheumatoid joints was subjected to an indirect immunoperoxidase protocol for the immunolocalization of metallothionein using mouse monoclonal anti-metallothionein antibody E9, reactive against the two major isoforms of mammalian metallothionein. A layer of large dendritic-like cells situated subsynovially in the rheumatoid synovium stained very positively for the metalloprotein, both cytoplasmically and in their nuclei. These cells were not found in non-rheumatoid osteoarthritic or in undamaged synovial tissue associated with traumatic joint injury. An attempt was made to investigate their lineage using a series of antibody markers against epithelial cells, endothelial cells, smooth muscle, mesothelial cells, fibroblasts, neutrophils, dermal dendrocytes, macrophages, low and high molecular weight cytokeratin as well as a cell proliferation marker. From our results, it is suggested that these metallothionein-positive cells are probably myofibroblasts similar to the highly motile cells present in granulation tissue. They may originate from perivascular areas of synovium and their movement into the inflamed synovium may reflect the cytoprotective role of metallothionein acting as a free radical scavenger against oxidative damage     

Induction of apoptosis in neoplastic cells by depletion of vitamin B12

Methionine synthase, a critical enzyme in deoxyribonucleotide biosynthesis for DNA replication, requires vitamin B12 as a cofactor. We have tested the hypothesis that depletion of cells of vitamin B12 would block growth of neoplastic cells and divert them into apoptosis and could form the basis of a new therapeutic strategy for cancer treatment. Using nitrous oxide to inactivate vitamin B12 we show that, in a variety of cell lines in vitro, methionine synthase is rapidly inhibited, the cells cease proliferation and undergo apoptosis. The kinetics of cell death, once started, are similar to those observed following methotrexate treatment or serum withdrawal. This is the first observation of apoptosis being induced following depletion of an essential metabolite as opposed to the more conventional strategy of adding a toxic drug to damage cells thereby triggering apoptosis. Moreover, vitamin B12 depletion has no effect on the nonproliferating cell population.     

Survival of Xenorhabdus nematophilus and Photorhabdus luminescens in water and soil

Strains of Xenorhabdus nematophilus and Photorhabdus luminescens were genetically marked with kanamycin resistance and the xylE gene to aid theirdetection in water and soil. Following release in river water, cells declined to undetectable levelsin 6 d. In sterile river water, this decline was enhanced with cells detectable for only 2 d. In sterileMilli-Q purified water, the decline was slower than in either sterile or non-sterile river water.Survival in soil was also restricted with cells only detectable for 7 d. These experiments indicatedthat both X. nematophilus and P. luminescens have limited survival orcompetitive abilities in these environments. The faster decline of populations in sterile river waterwas unexpected, and the possible formation of specialized survival stages was investigated. Insterile water, a non-culturable but viable population of cells was detected, indicating that cellsmay survive longer than anticipated in the environment and remain undetectable using standardmicrobiological methods. The implications of this work to the use of these strains in biologicalcontrol and the release of genetically-modified micro-organisms is discussed.