Selective effects of PHA on rat brush border hydrolases along the crypt-villus axis

Summary The mechanism of the toxicity of lectin fromPhaseolus vulgaris seeds has been investigated on rat enterocytes. Cell isolation procedures showed a selectivity in the loss of brush border hydrolases; this indicated that the microvilli blebbing was not the only mechanism of action of lectins on rat enterocytes.     

Origin of the synaptonemal complex

Résumé La microscopie életronique des noyaux méiotiques de l'amphibien tétraploïdeO. americanus et de la souris a permis d'émettre l'hypothese suivant laquelle le complexe synaptonémique résulte de l'invagination de la membrane nucléaire, le synapsis étant la conséquence de ce mécanisme.     

The generation of random ultrametric matrices representing dendrograms

Many methods and algorithms to generate random trees of many kinds have been proposed in the literature. No procedure exists however for the generation of dendrograms with randomized fusion levels. Randomized dendrograms can be obtained by randomizing the associated cophenetic matrix. Two algorithms are described. The first one generates completely random dendrograms, i.e., trees with a random topology, random fusion level values, and random assignment of the labels. The second algorithm uses a double-permutation procedure to randomize a given dendrogram; it proceeds by randomization of the fixed fusion levels, instead of using random fusion level values. A proof is presented that the double-permutation procedure is a Uniform Random Generation Algorithmsensu Furnas (1984), and a complete example is given. This work was supported by NSERC Grant No. A7738 to P. Legendre and by a NSERC scholarship to F.-J. Lapointe.     

The hexose content of theα-chains of bone collagen

Résumé Les 3 chaînes du collagène de l'os de poulet ont été isolées en combinant les techniques de filtration sur gel et d'électrophorèse en veine libre. Des substances donnant une réaction d'anthrone positive, avec spectre d'absorption caractéristique des hexoses, ont été mises en évidence dans ces 3 chaînes. En utilisant le glucose comme standard, la détermination des hexoses fournit une valeur de 12 moles d'hexoses par molécule de collagène.     

Artificial triploid hybrids by interspecific mating ofOdontophrynus (Amphibia,anura)

Résumé Des hybrides triploïdes ont été obtenus par croisement deOdontophrynus cultripes, amphibien diploïde, avecO. americanus, tétraploide. Les hybrides interspécifiques présentent normalement 33 chromosomes dans les cellules somatiques. Les hybridesO. cultripes ×O. americanus sont plus viables que lesO. americanus ×O. cultripes .

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This work was supported by Public Health Service Research Grant No. GM-14577-02 from the National Institute of General Medical Sciences and by Fundo de Pesquisas do Instituto Butantan.     

Senataxin, the ortholog of a yeast RNA helicase, is mutant in ataxia-ocular apraxia 2

Ataxia-ocular apraxia 2 (AOA2) was recently identified as a new autosomal recessive ataxia. We have now identified causative mutations in 15 families, which allows us to clinically define this entity by onset between 10 and 22 years, cerebellar atrophy, axonal sensorimotor neuropathy, oculomotor apraxia and elevated alpha-fetoprotein (AFP). Ten of the fifteen mutations cause premature termination of a large DEAxQ-box helicase, the human ortholog of yeast Sen1p, involved in RNA maturation and termination.