Isolation of oligodendroglial cells from young and adult whole rat brains using an in situ generated percoll density gradient

A method for the isolation of oligodendroglial cells from young and adult whole rat brains, using a Percoll density gradient is presented. The minced tissue, incubated in a balanced salt solution containing 0.1% trypsin is further dissociated by forcing it through nylon screens to 145 and 74 μm pore size. The crude suspension is then mixed with an isosmotic Percoll solution and centrifuged for 15 min. An in situ generated density gradient allows the separation of five bands, only one of which (Band C) lying between δ1.050 and δ1.062 contains cellular elements. The isolated cells show the typical morphological characteristics of oligodendroglia.A detailed morphological study of the cells isolated from whole brains of 10-, 30- and 120-day old rats is presented for the first time in the literature and immunocytochemical characterization is carried out using specific (antigalactocerebroside) and non specific (anti-glial fibrillary acidic protein) anti-sera.The method is simple and rapid and isosmotic conditions are maintained throughout, resulting in a better preservation of cell integrity. It represents an improvement over the two previous methods described in the literature and will be useful for studying different developmental events (biochemical and morphological) occurring in oligodendroglial cells at early stages of myelin formation.     

Production and characterization of DR xenoantisera: use for detection of serum DR antigens.

Immunoadsorbents consisting of rabbit anti-DR antibodies bound to Staphylococcus aureus were used to bind DR antigens from NP40 cellular extracts of cultured B lymphoid cells. When injected into rabbits, these DR antibody absorbents elicited the production of antibodies that were shown by both serologic and immunochemical techniques to react specifically with the DR antigen molecule. A rosette inhibition assay with B lymphoid cells and anti-DR xenoantisera was used to detect DR antigens in human serum. DR serum antigens could be found in an enriched preparation of serum lipoproteins obtained by centrifugation in KBr. In addition, sera from some patients with neoplastic diseases contained higher levels of DR serum antigens than those found in normal individuals.     

So similar and yet so different: taxonomic status of Pallid Swift Apus pallidus and Common Swift Apus apus

Capsule: Common Swift Apus apus and Pallid Swift Apus Pallidus are morphologically very similar but are genetically distinct and diverged 1.9–2.1 million years ago (mya).

Aims: To examine genetic differentiation and to estimate separation time between Common and Pallid Swifts.

Methods: Estimation of differences in three different mitochondrial DNA markers (COI, ND2 and control region), and a fourth marker, the cytb, that did not differ between taxa. Fossils were used to calibrate the estimate of separation date between the two taxa.

Results: The genetic between-species distances were 0.010, 0.006 and 0.033 for the three markers, respectively. These values were from three to ten times higher than within-species distances. Results show that the separation dates back to 1.9–2.1?mya, at the Plio-Pleistocene transition, when global climate underwent a period of significant cooling and Northern latitudes were probably more favourable to the Common than to the Pallid Swift.

Conclusion: Differences in breeding biology, migration, moult and vocalizations between the two species are mirrored by a clear genetic separation.     

Effect of starvation and refeeding on amino acid metabolism in muscle of crab Neohelice granulata previously fed protein- or carbohydrate-rich diets

The present study assesses the effects of starvation and refeeding on 1-[¹⁴C]-methyl aminoisobutyric acid (¹⁴C-MeAIB) uptake, ¹⁴C-total lipids, ¹⁴CO₂ production from ¹⁴C-glycine, ¹⁴C-protein synthesis from ¹⁴C-leucine and Na⁺–K⁺-ATPase activity in jaw muscle of Neohelice granulata previously maintained on a carbohydrate-rich (HC) or high-protein (HP) diet. In N. granulata the metabolic adjustments during starvation and refeeding use different pathways according to the composition of the diet previously offered to the crabs. During starvation, ¹⁴CO₂ production from ¹⁴C-glycine, and ¹⁴C-protein synthesis from ¹⁴C-leucine were reduced in HC-fed crabs. In crabs maintained on the HP or HC diet, ¹⁴C-total lipid synthesis increased after 15 days of starvation. In crabs fed HP diet, ¹⁴C-MeAIB uptake and Na⁺–K⁺-ATPase activity decreased in refeeding state. In crabs refeeding HC diet, ¹⁴C-MeAIB uptake and ¹⁴CO₂ production decreased during the refeeding. In contrast, the ¹⁴C-protein synthesis increased after 120 h of refeeding. In both dietary groups, ¹⁴C-total lipid synthesis increased during refeeding. Changes in the carbon amino acid flux between different metabolic pathways in muscle are among the strategies used by this crab to face starvation and refeeding. Protein or carbohydrate levels in the diet administered to this crab modulate the carbon flux between the different metabolic pathways.     

Asymbiotic nitrogen fixation in the litter and surface soil of a Pinus laricio Poiret forest (Sila,Calabria, Italy)

Abstract

Nitrogen fixation was measured in a Corsican pine (Pinus laricio Poiret) forest in Calabria (Southern Italy). Acetylene reduction activity (ARA) and CO₂ production levels were determined by incubation of litter and superficial (0–5 cm) soil layer samples in the field, at monthly intervals. ARA variations were not correlated to those of substrate moisture, air temperature and microbial respiration. In fact N₂ fixation presented phases of different intensity which irregularly followed each other. Both litter and soil showed similar rates of N₂ fixation. Based on a C₂H₂:N₂ ratio of 3:1 0.8 Kg N ha^–1 y^–1 in each layer are fixed in the Pinus laricio forest, thus contributing to the N status of the soil in this nutrient–poor forest.