Metabolic differences between primary cultures of astrocytes and neurons from cerebellum and cerebral cortex. Effects of fluorocitrate

Astrocytes and neurons cultured from mouse cerebellum and cerebral cortex were analyzed with respect to content and synthesis of amino acids as well as export of metabolites to the culture medium and the response to fluorocitrate, an, inhibitor of aconitase. The intracellular levels of amino acids were similar in the two astrocytic populations. The release of citrate, lactate and glutamine, however, was markedly higher from cerebellar than from cortical astrocytes. Neurons contained higher levels of glutamate, aspartate and GABA than astrocytic cultures. Cortical neurons were especially high in GABA and aspartate, and the level of aspartate increased specifically when the extracellular level of glutamine was elevated. Fluorocitrate inhibited the TCA cycle in the astrocytes, but was less effective in cerebellar neurons. Whereas neurons responded to fluorocitrate with an increase in the formation of lactate, reflecting, glycolysis, astrocytes decreased the formation of lactate in the presence of fluorocitrate, indicating that astrocytes to a high degree synthesize pyruvate and hence lactate from TCA cycle intermediates.     

Fermenter production of an artificial fab fragment,rationally designed for the antigen cystatin,and its optimized crystallization through constant domain shuffling

The synthetic antibody model “M41” was rationally designed with a binding site complementary to chicken egg white cystatin as the prescribed antigen. In order to permit comparison between the computer model and an experimental three-dimensional structure of the artificial protein, its X-ray crystallographic analysis was pursued. For this purpose, M41 was expressed as a recombinant Fab fragment in E. coli by medium cell density fermentation employing the tightly regulated tetracycline promoter. The Fab fragment was efficiently purified via a His-6 tail fused to its heavy chain and immobilized metal affinity chromatography. To raise the chances for the productive formation of crystal packing contacts, three versions of the Fab fragment were generated with differing constant domains. One of these, the variant with murine C_K and C_H 1_γ1 domains, was successfully crystallized by microseeding in a sitting drop. The orthorhombic crystals exhibited symmetry of the space group P2₁2₁2₁ with unit cell dimensions a = 104.7 Å, b = 113.9 Å, c = 98.8 Å and diffracted X-rays to a nominal resolution of 2.5 Å. © 1995 Wiley-Liss, Inc.     

Quantitative studies on brown algal phenols. I. Estimation of absolute polyphenol content of Ascophyllum nodosum (L.) Le Jol. and Fucus vesiculosus (L.)

Methods for estimating the absolute polyphenol content of the brown algae Ascophyllum nodosum (L.) Le Jol. and Fucus vesiculosus (L.) have been developed and tested. Polyphenols were extracted almost quantitatively from Ascophyllum nodosum using aqueous acetone, whereas this procedure was somewhat less efficient with Fucus vesiculosus. Colorimetric methods based on the Folin-Denis reagent, Brentamine Fast Red 2G Salt, and vanillin-H₂SO₄ were applied to acetone-free extracts for determination of polyphenol content relative to suitable reference compounds. Gravimetric methods based on hide powder and on haemoglobin were employed to derive ‘estimation factors’ (EFs) which allow calculation of the absolute polyphenol content from the relative polyphenol content. The values calculated for absolute polyphenol content are considered to be reasonably accurate, despite imprecisions in the methods and despite often large standard deviations, and re-emphasize the potential physiological and ecological significance of brown algal polyphenols. Although the precise EFs calculated here are not valid for other brown algae, the methods are considered to be generally applicable to other Phaeophyceae.     

ACTIVITY AND ISOENZYME PATTERN OF LACTATE DEHYDROGENASE IN ASTROBLASTS CULTURED FROM BRAINS OF NEWBORN MICE

Lactate dehydrogenase activity and isoenzyme distribution was determined in primary cultures of astroblasts as a function of the culture period. The specific activity increased during this period with a peak value (1.91 ± 0.18μmol x min^-1 x mg^-1 cell protein) after 2 weeks in culture. The isoenzyme pattern changed during 3 weeks in culture towards a higher proportion of the H₄ (LDH-1) isoenzyme which is analogous to the in vivo pattern. Omission of serum with or without dBcAMP (0.5 mM) in the culture medium during the third week of culture further enhanced this prominence of the H₄ isoenzyme. The specific activity (1.58 × 0.06 μmol x min^-1 x mg^-1 cell protein) of cultures grown in the presence of 0.5 mM-dBcAMP and absence of serum was close to the activity in the adult brain.     

Species Specificity in Thermostable and Ethanol Insoluble Tissue Antigens

In a previous experiment, rabbits and goats were immunized with boiled and ethanol precipitated (BE) bovine kidney antigen, and the specificity of the antibodies produced was compared (Andersen 1975). The caprine sera were species specific while the rabbit sera, however, cross-reacted with BE antigens from other ruminant species. Sera from 2 rabbit littermates differed somewhat in that 1 serum seemed to be mainly species specific giving only weak reactions against BE antigens from kidney and spleen from other ruminants, whilst the other serum was more organ specific and reacted equally with homologous and heterologous kidney antigens.     

Thermal Rearrangement of 4-Alkyl-1,2,4-triazoles. Rearrangements in the Crystalline State

Studies of the thermolyses of 4-alkyl substituted 1,2,4-triazoles was reviewed. They were observed to rearrange at 200–350 °C to the corresponding 1-alkylated triazoles. When substituted in the 4-position with aryl- or vinylic substituents the triazoles were inert to thermolysis, contrary to what was observed for the 4-alkyl- and 4-allyl substituted systems. The mechanisms for the reactions were elucidated, e.g., by studies of substituents effects and by kinetic measurements in solution as well as for the neat samples. Reactions in solutions were slow. The rearrangements in melts of the neat triazoles readily proceeded to the products, and were proposed to take place via a series of nucleophilic displacement steps. X-ray crystallographic measurements of selected structures, showed that the interatomic distances and angles between the relevant atoms in these structures, to a large degree resembled the geometry expected for the S_N2-type transition states proposed for the rearrangement mechanism. Thus, thermolyses of a series of triazole structures at temperatures below their melting points, confirmed that rearrangements actually did take place. The “kinetics” of the reactions in the crystalline state were investigated and rate constants and thermodynamic data were correlated with the structural characteristics of the crystals.     

Population structure,growth and fecundity of perch (Perca fluviatilis L.) in an acidified river system in Southern Norway

Population structure, density and reproductive potential of perch (Perca fluviatilis L.) from 4 acidified lakes in a river system in Southern Norway were investigated. The upper 3 lakes were most affected by acidification and the number of perch caught per unit effort indicate three-fold increase in density from the upper Gjerstadvann to the lower Brøbørvann. Low density of perch in the upper lakes is explained by; 1) Abnormal mortality occurring in episodes due to acidification, probably caused by aluminium toxicity at pH = 5.2–5.4. 2). Acid water (pH ≤ 5.0) during spawning and development of eggs and larvae, resulting in recruitment failure. Juvenile mortality of perch may depend on the density of the parental stock. In the 3 upper lakes, the density of adult perch probably was too low to produce significant juvenile mortality, and in these lakes the recruitment probably depended more on the May water quality. Improved water quality increases egg hatching and survival and also benefits zooplankton production, the main food for perch during the first summer. Low population density has reduced competition for food and thus improved growth of perch in the 3 upper lakes compared to the lower lake. The perch in Brøbørvann mature at higher age and have lower individual fecundity than perch in Gjerstadvann, an effect of both slower growth and lower length specific fecundity in Brøbørvann. In Gjerstadvann, the perch therefore have a higher reproductive potential relative to the stock density, and may, when the water quality is good enough, give rise to strong year-classes and more frequent year-class fluctuations than perch in the less acid Brøbørvann.     

A common sequence in the inverted terminal repetitions of human and avian adenoviruses

The termini of the avian chick embryo lethal orphan (CELO) virus DNA have been sequenced. The results revealed a 63-bp-long inverted terminal repetition (ITR) which shared the sequence ATAATA with all adenovirus termini, thus far analyzed. The CELO virus ITR differed from those of the mammalian adenoviruses in two major aspects: (i) it is not a perfect duplication; (ii) it begins with a 5'-guanylic acid residue instead of the cytidylic acid normally observed in adenoviruses.     

Specificity in the inactivation of enzymes by periodate-oxidized nucleotides

Periodate-oxidized ATP (oATP) inactivates the partial reaction of aminoacyl-tRNA synthetases in which amino acid is transferred to tRNA without altering the other partial reaction in which ATP is a substrate or a product. The inactivation has been shown to be nonspecific with regard to substituents on the dialdehyde and with regard to the enzymes susceptible to inactivation; oxidized GTP and oxidized uridine react as well as oATP with aminoacyl-tRNA synthetases and all three dialdehydes also inactivate rabbit muscle aldolase.     

Differences in drifting of larval stages of Rhyacophila nubila (Trichoptera)

Larval drift of the trichopteran Rhyacophila nubila (Zett.) was studied in a West Norwegian river. The frequency distribution of different instars in the drift samples was significantly different compared with the benthic samples. The drift, measured as the number which passed a transect of the river, rised markedly in periods of high water discharge. Different instars can be arranged according to the extent in which they are drifting: 2>3>4>1>5. Instar 1 and 2 shared a neutral phototaxis. From the 2nd instar and on, the larvae became increasingly night-active with a culmination in the last instar which was highly night active, also confined by laboratory studies. It is suggested that changes in activity patterns is associated with a shift towards a more carnivorous way of life.