Transformation by integration in Podospora anserina. III. Replacement of a chromosome segment by a two-step process

Summary We have developed in Podospora anserina a two-step procedure for DNA sequence replacement through transformation which might be applicable to other filamentous fungi. Targeting of transforming DNAs to their homologous locus is achieved provided a cosmid vector is used. Southern blot analysis of genomic DNAs from a set of transformants is presented. The data confirm that cosmids integrate into the chromosome through mostly homologous recombination which leads to a duplicated sequence separated by the vector. This event was found to be unstable in crosses. We show that this instability is due to the frequent excision of the vector together with the selective marker and one copy of the duplication, either the resident or foreign sequence. The two sequences can be distinguished because they exhibit restriction fragment length polymorphism. Therefore, Podospora anserina treats duplications occurring through transformation in a way differing from that exhibited by Neurospora crassa and Ascobolus immersus.     

Prevalence of Antibody to Current Influenza Viruses and Effect of Vaccination on Antibody Response

The extent of antibody to the influenza virus A/Hong Kong/68 (H3N2) after four years of prevalence was investigated in Britain and in the U.S.A. The results indicated a high incidence in both populations. The prevalence of antibody to a variant A/England/42/72 (H3N2) which has been causing epidemics of influenza in the southern hemisphere during the middle months of 1972 was also investigated. The differences reflect the shift in antigenic content of this variant, and although the overall proportion of the sera with antibody at > 1/40 was 37%, some age groups had an incidence of only 20% or less with antibody at this level. A commercial inactivated A/Hong Kong/68 influenza vaccine was given to a group of volunteers in Britain to see how effective it might be in stimulating antibody to the variant A/England/42/72. The antibody responses were better than expected from earlier vaccine studies, and 63% of the vaccinees developed antibody to the A/England/42/72 to levels thought likely to be protective. This suggested that until a vaccine made with the variant A/England/42/72 becomes available the present A/Hong Kong/68 vaccine would be of use to protect those at special risk this winter.     

EFFECT OF COCAINE ON THE GROWTH OF LUPINUS ALBUS. A CONTRIBUTION TO THE COMPARATIVE PHARMACOLOGY OF ANIMAL AND PLANT PROTOPLASM

1. The effects of cocaine and its decomposition products were studied on the growth of the young roots of Lupinus albus. 2. The results obtained were compared with similar experiments on animal tissues. 3. It was found that, while cocaine is the most toxic of these compounds studied for animal tissues, it was of comparatively low toxicity in respect to its effect on the growth of roots. On the other hand, sodium benzoate, being practically non-toxic for animals, was the most toxic of the compounds studied for the plant roots.     

Analyse Durch ?thylurethan Bei Drosophila Induzierter Mutationen

Zusammenfassung Urethan hat bei Drosophila eine deutliche mutationsauslösende Wirkung. Die durch Urethan induzierten Mutationen waren entweder mit Chromosomenstückausfällen verbunden oder sie gehörten zur Klasse der sog. Punkt-Mutationen. Die vorwiegend zur letzteren Klasse gehörenden letalen und sichtbaren Mutationen traten in einem Zahlenverhältnis zueinander auf, das dem von anderen Autoren an bestrahltem oder unbehandeltem Material beobachteten Zahlenverhältnis entspricht. Ferner ergaben sich keine Anzeichen einer selektiven Wirkung des Urethans auf bestimmte Chromosomen-Loci. Die Loci, die nach Urethanbehandlung vorwiegend befallen wurden, sind die gleichen Loci, die eine erhöhte spontane Mutationsrate besitzen und zugleich eine erhöhte Empfindlichkeit gegenüber Röntgenstrahlen zeigen.Mit 5 Textabbildungen.     

Compartmental models for human iodine metabolism

Compartmental models for the various aspects of human iodine metabolism are reviewed, emphasizing the role of Mones Berman in the development of this field. The review first presents published submodels for the peripheral distribution of inorganic iodine, for the thyroidal iodide trapping function, and for the peripheral distribution and metabolism of the thyroid hormones. Approaches to improving understanding of the physiology of the thyroid gland itself through compartmental modeling techniques are then discussed in more detail. The three submodels described above are incorporated into overall models of thyroid iodine metabolism after being simplified to various degrees. Previously published models for thyroid-gland radioiodine metabolism, as well as current work in progress, are illustrated by attempting to fit the models to data from a single (previously unpublished) detailed prolonged ¹²⁵I feeding experiment in a normal human subject. Published thyroid gland models reviewed include: (1) the usual presentation, where the thyroid is a single homogeneous iodine compartment; (2) the model of DeGroot and colleagues, where thyroidal iodine is presented as MIT, DIT, T3, and T4, each with an active and linked storage compartment; (3) the thyroid model developed by Berman and colleagues, with less chemical subcategorization but incorporating a delay compartment, in which a fraction of the iodinated material in the thyroid is partially or completely inaccessible to secretion during the delay; and the later updating of Berman's model to include a thyroidal iodide recirculation pool. The experimental data presented fits most of these models for the first 1–2 weeks, but the fit could not be extended to longer data collection times. To overcome this shortcoming, a new thyroid gland model is introduced. It is based on the latest Berman model but describes thyroglobulin metabolism as incorporating multiple delay compartments of various time periods. The overall fit of the long term data is better with this model construct than with any of the published models. It appears that a complex thyroidal substructure, such as that of the multidelay model under development, will be required to account for overall thyroid iodine metabolism as isotopic equilibrium in man is approached.     

Calorimetric determination of the conformational transition of kappa carrageenan

This paper deals with measurements of the heat of the helix-coil transition by microcalorimetry for kappa carrageenans; data are given in the absence of gel in various solvents (H₂O, Me₂SO, and formamide) with two counterions (K⁺, Rb⁺). In water, the influence of gel formation on ΔH is pointed out and the influence of the time of ageing is demonstrated. The ΔH values measured in the absence of gel are interpreted in terms of the electrostatic model proposed by Manning; the agreement is quite good if a double helix is formed in water, but a monochain, ordered conformation is suggested for solutions in Me₂SO and formamide.     

Mutations affecting translational fidelity in the eucaryote Podospora anserina: Characterization of two ribosomal restrictive mutations

Summary Fifty-nine mutations that restrict suppressor efficiency were selected in the fungus Podospra anserina using four different screening methods. Previous genetic analysis has shown that these antisuppressors lie in six loci and that they could be similar to ribosomal restrictive mutations known in Escherichia coli. The present study deals with the response of two of them, AS1-1 and AS6-1, to paromomycin and low temperature both in vivo and in vitro. The data demonstrate that ribosomes of the mutant and double-mutant strains are equally resistant to the ambiguity effect of paromomycin. These data are the first demonstration of mutations that increase translational fidelity in a eucaryotic organism.     

La variabilité cytologique dans la descendance des femelles de Luffia ferchaultella steph. (Lepidoptera psychidae)

Summary The procedure which leads to the restoration of the diploid chromosomal number in the egg of the parthenogenetic Luffia ferchaultella is similar in all the eggs laid by one female. But it may vary in the eggs of closely related females (mother and daughters or sisters). Therefore it is not a characteristic of the parthenogenetic strain.

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Au Professeur Bauer, en témoignage d'admiration.

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Travail subventionné par le Fonds National Suisse de la Recherche Scientifique.