Free and polymerized tubulin in cultured bone cells and Chinese hamster ovary cells: the influence of cold and hormones

A low pH method of liposome-membrane fusion (Schneider et al., 1980, Proc. Natl. Acad. Sci. U. S. A. 77:442) was used to enrich the mitochondrial inner membrane lipid bilayer 30-700% with exogenous phospholipid and cholesterol. By varying the phospholipid-to- cholesterol ratio of the liposomes it was possible to incorporate specific amounts of cholesterol (up to 44 mol %) into the inner membrane bilayer in a controlled fashion. The membrane surface area increased proportionally to the increase in total membrane bilayer lipid. Inner membrane enriched with phospholipid only, or with phospholipid plus cholesterol up to 20 mol %, showed randomly distributed intramembrane particles (integral proteins) in the membrane plane, and the average distance between intramembrane particles increased proportionally to the amount of newly incorporated lipid. Membranes containing between 20 and 27 mol % cholesterol exhibited small clusters of intramembrane particles while cholesterol contents above 27 mol % resulted in larger aggregations of intramembrane particles. In phospholipid-enriched membranes with randomly dispersed intramembrane particles, electron transfer activities from NADH- and succinate-dehydrogenase to cytochrome c decreased proportionally to the increase in distance between the particles. In contrast, these electron- transfer activities increased with decreasing distances between intramembrane particles brought about by cholesterol incorporation. These results indicate that (a) catalytically interacting redox components in the mitochondrial inner membrane such as the dehydrogenase complexes, ubiquinone, and heme proteins are independent, laterally diffusible components; (b) the average distance between these redox components is effected by the available surface area of the membrane lipid bilayer; and (c) the distance over which redox components diffuse before collision and electron transfer mediates the rate of such transfer.     

Effects of the administration of cadmium and zinc on the concentration of zinc in the thymus of rats

The zinc content of thymus glands of male Wistar rats has been determined during five weeks of treatment with ZnCl₂ and CdCl₂, and compared with a group of control rats. THymus gland extracts were chromatographed on columns of Sephadex G-75 and the zinc content of the one hundred fractions obtained were determined by atomic absorption spectrophotometry. The rats treated with ZnCl₂ showed an increase in the thymus concentration of zinc bound to high and low molecular weight proteins. The rats treated with CdCl₂ showed an increase in zinc concentration, as opposed to the control group, during the first three weeks of treatment, and thereafter show a toxic effect of cadmium on the gland, with ulterior regression of the latter, and a decrease in the concentration of zinc.     

The activity of tissue enzymes in iron-deficient rat and man: an overview

The effects of iron deficiency in rat and/or man on iron-containing enzymes of different tissues is reviewed. Iron deficiency results in a decrease of skeletal muscle iron containing proteins e.g. myoglobin, cytochromes c, a + a3, and alpha-glycerophosphate oxidase. Iron deficiency produces a reduction in the activity of several respiratory enzymes in the mitochondrial fraction of cardiac muscle, particularly: NADH cytochrome c reductase, succinic cytochrome c reductase, succinic dehydrogenase and NADH ferricyanide oxidoreductase. The effects of iron deficiency on brain tissue is emphasized with respect to cytochromes, monoaminoxidase and amino acids metabolism. Host defence to infection (controversial data), decrease in body temperature, alteration of DNA synthesis, collagen and lipid metabolism, liver and gastrointestinal mucous cytochromes activity perturbations are discussed.     

Movements and associations of ribosomal subunits in a secretory cell during growth inhibition by starvation

In Chironomus tentans salivary gland cells, the cytoplasm can be dissected into concentric zones situated at increasing distances from the nuclear envelope. After RNA labeling, the newly made ribosomal subunits are found in the cytoplasm mainly in the neighborhood of the nucleus with a gradient of increasing abundance towards the periphery of the cell. The gradient for the small subunit lasts for a few hours and disappears entirely after treatment with puromycin. The large subunit also forms a gradient but one which is only partially abolished by puromycin. The residual gradient which which is resistant to the addition of the drug is probably due to the binding of some large ribosomal units to the membranes of the endoplasmic reticulum (J.-E. Edstrom and u. Lonn. 1976. J. Cell Biol. 70:562-572, and U. Lonn and J.-E. Edstrom. 1976. J. Cell. Biol. 70:573-580). If growth is inhibited by starvation, only the puromycin-sensitive type gradient is observed for the large subunit, suggesting that the attachment of these newly made subunits to the endoplasmic reticulum membranes will not occur. If, on the other hand, the drug-resistant gradient is allowed to form in feeding animals, it is conserved during a subsequent starvation for longer periods than in control feeding animals. This observation provides a further support for an effect of starvation on the normal turnover of the large subunits associated with the endoplasmic reticulum. These results also indicate a considerable structural stability in the cytoplasm of these cells worth little or no gross redistribution of cytoplasmic structures over a period of at least 6 days.     

Interleukin 2 production in iron-deficient children

The relationship between iron status and capacity for IL-2 production by lymphocytes was assessed in 81 children from 6 mo to 3 yr of age selected at random from a population with low socioeconomic status, undergoing free systematic examination in four children's health centers in the Paris area. Iron deficiency was defined by the existence of at least two abnormal values among the three indicators of iron status: serum ferritin level ≤12 μg/L, transferrin saturation <12%, and erythrocyte protoporphyrin concentration >3 μg/g hemoglobin. According to this definition, 53 children were classified as iron deficient and 28 as iron sufficient. No differences were observed between the iron-deficient and iron-sufficient groups in terms of the IL-2 concentration without stimulation by PHA. IL-2 production by lymphocytes stimulated with PHA, as well as the stimulation index (ratio of IL-2 concentration following stimulation by PHA to that of IL-2 concentration without stimulation by PHA) were significantly lower in iron-deficient children. The reduction in IL-2 production by activated lymphocytes observed in our study of iron-deficient children may be responsible for impairments in immunity found by other authors, particularly in cell-mediated immunity.     

In silico and empirical evaluation of twelve metabarcoding primer sets for insectivorous diet analyses

During the most recent decade, environmental DNA metabarcoding approaches have been both developed and improved to minimize the biological and technical biases in these protocols. However, challenges remain, notably those relating to primer design. In the current study, we comprehensively assessed the performance of ten COI and two 16S primer pairs for eDNA metabarcoding, including novel and previously published primers. We used a combined approach of in silico, in vivo‐mock community (33 arthropod taxa from 16 orders), and guano‐based analyses to identify primer sets that would maximize arthropod detection and taxonomic identification, successfully identify the predator (bat) species, and minimize the time and financial costs of the experiment. We focused on two insectivorous bat species that live together in mixed colonies: the greater horseshoe bat (Rhinolophus ferrumequinum) and Geoffroy's bat (Myotis emarginatus). We found that primer degeneracy is the main factor that influences arthropod detection in silico and mock community analyses, while amplicon length is critical for the detection of arthropods from degraded DNA samples. Our guano‐based results highlight the importance of detecting and identifying both predator and prey, as guano samples can be contaminated by other insectivorous species. Moreover, we demonstrate that amplifying bat DNA does not reduce the primers' capacity to detect arthropods. We therefore recommend the simultaneous identification of predator and prey. Finally, our results suggest that up to one‐third of prey occurrences may be unreliable and are probably not of primary interest in diet studies, which may decrease the relevance of combining several primer sets instead of using a single efficient one. In conclusion, this study provides a pragmatic framework for eDNA primer selection with respect to scientific and methodological constraints.     

Identification of the Components of a Glycolytic Enzyme Metabolon on the Human Red Blood Cell Membrane

Glycolytic enzymes (GEs) have been shown to exist in multienzyme complexes on the inner surface of the human erythrocyte membrane. Because no protein other than band 3 has been found to interact with GEs, and because several GEs do not bind band 3, we decided to identify the additional membrane proteins that serve as docking sites for GE on the membrane. For this purpose, a method known as “label transfer” that employs a photoactivatable trifunctional cross-linking reagent to deliver a biotin from a derivatized GE to its binding partner on the membrane was used. Mass spectrometry analysis of membrane proteins that were biotinylated following rebinding and photoactivation of labeled GAPDH, aldolase, lactate dehydrogenase, and pyruvate kinase revealed not only the anticipated binding partner, band 3, but also the association of GEs with specific peptides in α- and β-spectrin, ankyrin, actin, p55, and protein 4.2. More importantly, the labeled GEs were also found to transfer biotin to other GEs in the complex, demonstrating for the first time that GEs also associate with each other in their membrane complexes. Surprisingly, a new GE binding site was repeatedly identified near the junction of the membrane-spanning and cytoplasmic domains of band 3, and this binding site was confirmed by direct binding studies. These results not only identify new components of the membrane-associated GE complexes but also provide molecular details on the specific peptides that form the interfacial contacts within each interaction.     

Immune gene variability influences roe deer natal dispersal

Dispersal is a key life‐history trait governing the response of individuals, populations and species to changing environmental conditions. In the context of global change, it is therefore essential to better understand the respective role of condition‐, phenotype‐ and genetic‐dependent drivers of dispersal behaviour. Although the importance of immune function and pathogen infestation in determining patterns of dispersal is increasingly recognised, no study to our knowledge has yet investigated the influence of immune gene variability on dispersal behaviour. Here, we filled this knowledge gap by assessing whether individual heterozygosity at five immune gene loci (one from the Major histocompatibility complex and four from encoding Toll‐like receptors) influences roe deer natal dispersal. We found that dispersal propensity was affected by immune gene diversity, suggesting potential pathogen‐mediated selection through over‐dominance. However, the direction of this effect differed between high and low quality individuals, suggesting that dispersal propensity is driven by two different mechanisms. In support of the condition‐dependent dispersal hypothesis, dispersal propensity increased with increasing body mass and, among high quality individuals only (standardized body mass > 18 kg), with increasing immune gene diversity. However, among poor quality individuals, we observed the opposite pattern such that dispersal propensity was higher for individuals with lower immune gene diversity. We suggest that these poor quality individuals expressed an emergency dispersal tactic in an attempt to escape a heavily infested environment associated with poor fitness prospects. Our results have potentially important consequences in terms of population genetics and demography, as well as host–pathogen evolution.     

Glycosyltransferase activity can be selectively modulated by chemical modifications of acceptor substrates

A range of N-acetyllactosamine derivatives, which are modified by a wide range of functionalities at C-2(') and C-6, have been synthesised and the kinetic parameters of transfer catalysed by recombinant alpha-2,6-sialyltransferase and alpha-1,3-fucoyltransferase VI determined. Several of the chemical modifications led to selective modulate the activity the enzymes and offer promising lead compounds for the development of oligosaccharide primers for selective metabolic inhibition of oligosaccharide biosynthesis.