Circadian changes in carrageenin-induced edema: the anti-inflammatory effect and bioavailability of phenylbutazone in rats

The circadian variations in paw-edema produced by carrageenin and the anti-inflammatory effect of phenylbutazone were studied, in rats kept under a 12 light-12 dark regimen, in comparison with the variations of plasma phenylbutazone and oxyphenbutazone levels. When the experiment was performed during the light span (08.00 and 14.00 h), the rats were highly sensitive to the phlogistic effect of carrageenin, the plasma levels of phenylbutazone and oxyphenbutazone were lower, and the anti-inflammatory effect of phenylbutazone, weaker. Opposite results were obtained when the experiment was performed during the dark span (02.00 and 20.00 h). The results indicate that the chronoeffectiveness of phenylbutazone is influenced by both its chronokinetics and the chronesthesy of the biosystem involved.     

Energy migration in the poly(ra-rU)-ethidium complex. determination of the unwinding angle of the polyribonucleic helix

The polarized fluorescence of the ethidium bromide (EB)-poly(rA-rU) complex has been studied by pulse fluorometry. As expected for a polynucleotide snowing one single kind of intercalation site, the decay of the whole emission is a single exponential (time constant 27 ns). The anisotropy decay is analysed as follows: (1) A brownian contribution having two correlation times, one of which characterizes local motions and the other a macromolecular motion. (2) A contribution due to transfers between EB molecules fixed to the same polynucleotide molecule, is analysed by a method analogous to the method used in previous work on EB-DNA complexes. That method consists in choosing a molecular model of the complex depending on geometrical parameters, and in simulating the energy migration on that model with a Monte Carlo calculation. Poly(rA-rU) is assumed here to adopt the structure A of RNA. Intercalated EB molecules modify the anale between two consecutive base pairs by δ. The angular position of the EB transition moment is defined by an angle φ. One finds that the angle φ is situated between 0° and 30°, which corresponds to a whole intercalation of the chroniophore as opposed to the semi-intercalation which has been proposed for certain dyes. The angle δ is negative; therefore there is an unwinding of the polyribonucleotide helix. Its absolute value is about 38°, sensibly greater than The value previously found for EB-DNA complexes.     

Grouped sequential exploitation of food patches in a flock feeder,the feral pigeon

Feral and laboratory flocks of rock doves ($\text{Columba}$$\text{livia}$) show a pattern of grouped sequential exploitation when simultaneously presented with two dispersed, depleting patches of seed. This behavior contrasts with the ideal free distribution pattern shown when patches are small and concentrated. Grouped sequential exploitation consists of two phases: all pigeons first land together and feed at one patch, then leave one by one for the other patch. Departure times of individuals for the second patch are correlated with feeding rate at patch 1, which is in turn correlated with position in the dominance hierarchy. The decision to switch from patch 1 to patch 2 improves individual feeding rates in all cases, but is done slightly later than it should according to optimal foraging theory.     

The use of fluorescence anisotropy decay of poly d(A-T) ethidium bromide complex to estimate the unwinding angle of the double helix.

We measured the fluorescence decay under polarized light, of ethidium bromide bound to the poly d(A-T) isolated from Cancer Pagurus. The decay of the whole fluorescence is a single exponential function revealing a good homogeneity of the binding sites. The anisotropy decay due to energy transfers between the ethidium bromide molecules bound to a same poly d(A-T) molecule has been analysed, with a Monte Carlo calculation. We found the dye unwinds the poly d(A-T) duplex by an angle of 17 degrees plus or minus 2 degrees. This result is in agreement with the value previously found in the case of calf thymus DNA-ethidium bromide complex, although the base compositions of the two nucleic acids are different.     

Fine structure of bovine lens epithelial cells in vitro in relation to modifications induced by a retinal extract (EDGF)

Cultured bovine lens epithelial cells are polygonal in shape. In confluent and multilayer cultures they exhibit elaborate arrays of 6 nm filaments, bundles of intermediate-sized filaments, and a fibrous meshwork of subcellular and intercellular material. Cells grown in the presence of a retinal extract (RE) have a higher growth rate, and are smaller and more regular in shape. In them the 6 nm filaments are mostly aligned in sheets, the intermediate-sized filaments form a fine network, and the cells are closely apposed to the plastic substratum. Some homogeneous material is formed intercellularly in older cultures. Cellular elongation, induced in the former cultures by the addition of RE, is accompanied by an alignment of cytoskeletal elements, including microtubules, parallel to the long axis. Other structural features are similar in all cell types. The response to RE is discussed in terms of shape modulations associated with the restricted expression of structural characteristics acquired in vitro.     

Mutagenesis in multinucleate cells: the effects of N-methyl-N'-nitro-N-nitrosoguanidine on Phycomyces spores

Multinucleate cells, such as the spores of the fungus Phycomyces, are unsuitable for the isolation of recessive mutants. Nuclear killing by N-methyl-N'-nitro-N-nitrosoguanidine (henceforth nitrosoguanidine) eliminates all but one of the nuclei in some of the cells and allows the expression of recessive mutations. Even in the best conditions, only about 35% of the survivors have a single functional nucleus. Functionally uninucleate cells can be positively selected. This involves the exposure to nitrosoguanidine of the spores of a heterokaryon and selection for a recessive marker present in a small fraction of its nuclei. The optimal conditions for nitrosoguanidine mutagenesis in Phycomyces differ from those for bacteria and yeast. Buffer composition and pH are less important than in other organisms. Survival is an exponential function and mutation induction a linear function of the dose of the mutagen (concentration X time). Spore germination leads to an immediate increase in the number of gene copies per cell, thus further hindering the expression of recessive mutations; dominant mutations are then nearly always isolated in heterokaryotic form.     

The increase in cyclic-AMP levels elicited by vasoactive intestinal peptide (VIP) in mouse cerebral cortical slices is potentiated by ergot alkaloids

We have recently observed that noradrenaline potentiates, via the activation of specific -receptors, the stimulatory effects of vasoactive intestinal peptide on cyclic-AMP levels. We report here that certain ergot derivatives of the ergopeptine class, such as bromocriptine, ergotamine and codergocrine known to interact with alpha-adrenergic receptors, will also potentiate the effects of VIP on cyclic-AMP levels, without increasing directly the levels of the cyclic nucleotide. To our knowledge, these results demonstrate for the first time the existence of an interaction between a neuropeptide and ergot alkaloids within the cerebral cortex.     

Prey capture by the cuttlefish (Sepia officinalis L): An experimental study of two strategies

This study shows that the size of the prey ($\text{Carcinus maenas}$) relative to the predator ($\text{Sepia officinalis}$) is of importance in the choice between two types of attack: either capture by ejection of the two extensible tentacles, or capture by jumping on the prey. Small crabs are preferentially captured by the first method and large crabs by the second. Other factors which may explain the observed variations, include previous experience of the predator and the behaviour of the prey.     

Perinuclear organelles of the sensory cell of the Grandry cutaneous corpuscle. Ultrastructure and formation

Perinuclear organelles are found in the sensory cell of the Grandry cutaneous corpuscle in the duck. They are ovoid, fusiform or conical. They measure up to 5 µ length and l µ in diameter. They are formed by regular alternation of granular layers (mornolayers of RNA-rich granules which can be interpreted as ribosomes) and fibrous layers (generally formed by two sublayers of parallel fibrils). These fibrils (60-80 Å diameter) are in continuity with the intra-cytoplasmic fibrils which are very abundant in the Grandry cell. The central part of the organelles is devoid of RNA-rich granules.The formation of these organelles begins about one week after hatching, in the cytoplasmic perinuclear area where abundant granular endoplasmic reticulum and very numerous ribosomes and fibrils are present. The function of these perinuclear organelles remains unknown.     

Cell multiplication and type II collagen production by rabbit articular chondrocytes cultivated in a defined medium

The complexity and the variations in the efficiency of different batches of serum stimulated the preparation of a serum-free medium which could promote not only growth, but also the differentiation properties of rabbit articular chondrocytes in culture. The serum-free medium (SFM) developed in this study contained insulin, transferrin, Na-selenite, human fibronectin bovine serum albumin (BSA), brain growth factor (BGF) or fibroblast growth factor (FGF), hydrocortisone and multiplication stimulating activity (MSA). Primary or secondary cultures of chondrocytes in such a medium attained a proliferation rate equal to 70-80% of that obtained with chondrocytes grown in a serum control medium. The deletion of various factors from SFM indicates that BGF or FGF are the most stimulating of growth factors. Insulin was beneficial when used individually; when combined with BGF or FGF, they had a synergistic effect on cell proliferation. MSA seemed not to play any role in chondrocyte growth in culture. The SFM medium did not modify either the morphology or the progression of cells into the cell cycle. It moreover allowed the maintenance of the specific function of chondrocytes to synthesize type II collagen.     

Stimulatory effects of 5 beta-dihydrotestosterone on the sexual behavior in the domestic chick

During in vitro incubations, brain tissues of chicks transform testosterone mainly into 5β-reduced androgens including 5β-dihydrotestosterone (β-DHT). Although β-DHT is generally believed to have no androgenic effects, we showed recently that it stimulates sexual behavior in young chicks during hand thrust tests. This result was confirmed during three experiments presented here and the possible interactions of β-DHT with the endogenous sex steroids have been analyzed. There is no synergism between β-DHT and estradiol in the induction of sexual behavior in the chicks. β-DHT is still partly active in chicks injected with the antiandrogen, cyproterone acetate in doses sufficient to block all action of the endogenous testosterone. β-DHT is also active in castrated chicks. The effects of β-DHT on the sexual behavior thus do not seem to depend on an interaction with other sex steroids and the reasons why it is active in chicks during hand thrust tests and not in other test situations in other birds are briefly discussed.     

Transferrin binding to K562 cell line : Effect of heme and sodium butyrate induction

Experiments demonstrating the existence of receptors for iron-saturated transferrin on K562 cells are described. Binding of ¹²⁵I-labelled transferrin is rapid, saturable and reversible, and can be specifically inhibited by unlabelled transferrin, but not by other proteins. The number of receptors determined by Scatchard analysis significantly decreased when K562 cells moved from the exponential to the quiescent phase of growth. Induction by hemin or sodium butyrate resulted in a marked reduction of transferrin binding. This phenomenon was due entirely to reduction in the number of receptors and was without effect on the affinity of interaction. The effect of butyrate and hemin on the number of transferrin receptors in other hematopoietic cell lines was investigated. Butyrate on the various cell lines was variable in its effect, whereas hemin constantly elicited a significant reduction in the number of transferrin receptors.     

Kinetic cooperativity in the concerted model for allosteric enzymes.

The cooperativity of enzyme-substrate interactions is investigated in the concerted allosteric model of Monod, Wyman and Changeux. The general case of K-V systems is considered, in which the two protomer conformational states R and T postulated in the theory differ in catalytic and binding properties. An expression for the Hill coefficient nH defined with respect to the asymptotic velocity V infinity to is analyzed in conditions which exclude substrate inhibition. Kinetic cooperativity is always positive (nH greater than 1) in the case of a dimer enzyme, and in the case of an inactive T state. Slight kinetic negative cooperativity (nH less than 1) occurs under restrictive conditions for larger numbers of protomers when the substrate binds significantly to the less active state of the enzyme, but the phenomenon remains negligible for trimers and tetramers. These conclusions differ from those obtained [A. Goldbeter, J. Mol.Biol.90 (1974) 185] with the Hill coefficient based on the absolute maximum velocity, which may exceed the experimental value V infinity to in K-V systems. The results extend those of Paulus and DeRiel [J. Mol. Biol. 97 (1975) 667] and support the view that in most cases, negative cooperativity is not compatible with a mechanism based on a concerted and conservative allosteric transition. The Hill coefficients for binding and catalysis are compared in K-V systems.     

Requirement of successive protein syntheses for the progress of meiosis in Blepharisma

Germ nuclei of Blepharisma japonicum begin meiosis within a few hours when cells of complementary mating types conjugate. We synchronized the onset of conjugation and treated cells in different stages of meiosis with 10 micrograms/ml cycloheximide which strongly inhibits protein synthesis in this ciliate. Cycloheximide arrested meiosis at six stages: I, between pairing of cells and swelling of germ nuclei; II, leptotene; III, zygotene; IV, pachytene; XI, interkinesis; XII, prometaphase II. Five of these arrests were reversible. Puromycin (250-500 micrograms/ml) also inhibited the progress of meiosis, though to lesser extents. We propose that the progression of meiosis of B. japonicum requires at least six proteins which are synthesized sequentially during meiosis.