Complement with 38 chromosomes in two south American populations ofRattus rattus

Resumen Se estudiaron los cromosomas de 16 ejemplares deRattus rattus provenientes de la Provincia de Buenos Aires (Argentina) y del Estado de Rio Grande do Sul (Brasil). En todos los animales el complemento estuvo formado por 38 cromosomas. Considerando que en las ratas el complemento de 42 cromosomas es probablemente el mas generalizado, se sugiere que el complemento de 38 cromosomas ha derivado del de 42 mediante un proceso de reordenamiento cromosómico con fusión céntrica.     

Germ cell chromosomes in two species of terrestrial isopods from India

Summary In 2 species of terrestrial isopods, namelyPorcellio assamensis andP. laevis, the diploid and haploid numbers of chromosomes have been established to be 48 and 24 respectively for the former species and 50 and 25 respectively for the latter species. Female heterogamety of the ZW type has been found to exist inP. laevis.The authors express their sincere thanks to Prof. G.P. Sharma, and to Prof. S. Khera, Department of Zoology, Panjab University, Chandigarh, for the necessary laboratory facilities.     

The karyotype of the black rat (Rattus rattus L.). Another population with a 38-chromosomes complement

Riassunto In una popolazione italiana diRattus rattus L. è stato messo in evidenza un cariotipo a 38 cromosomi; la differenza nel numero diploide rispetto a quanto noto per altre popolazioni della stessa specie è dovuta a due fusioni centriche in condizione omozigote. Il confronto con i cariotipi forniti da altri autori per la specieRattus rattus ci fa proporre anche per questa specie di Roditori la presenza di un fenomeno di polimorfismo cromosomico.     

Chromosomal identity of black rats (Rattus rattus) from the Galápagos Islands,Ecuador

Resumen Muestras de ratas negras (Rattus rattus) de siete islas del Archipiélago de Galápagos fueron examinadas para estudios de chromosomas. El número diploide de todos los animales es 38 y los cariotipos son idénticos a los de las poblaciones europeas, americanas, y australianas. La conclusión general es que la falta de variabilidad cariotípica de las poblaciones introducidas se explica por la capacidad de ratas de establecerse por medio de cambios fenotípicos.     

Oceanian type black rats (Rattus rattus) with a subtelocentric M2 chromosome and C-type transferrin obtained from North America

Résumé Dix rats (Rattus rattus) d'une colonie californienne ont été examinés. Cinq sont de type océanique. Les cinq autres ont 1 paire M₂ hétéromorphe, formée d'un métacentrique et d'un sub-métacentrique, ce qui implique une inversion péricentrique. Les transferrines sont du type océanique.     

The chromosomes ofBufo rubropunctatus andBufo chilensis (Anura,Bufonidae) and other species of thespinolosus group

Summary The chromosomes ofBufo rubropunctatus andB. chilensis (on basis of adults) are described for the first time. These chromosomic sets are compared with the karyotypes ofB. spinolosus andB. variegatus and other species ofspinolosus group. The importance of the secondary constrictions applied to the phylogeny ofBufo are discussed.Supported by Proyecto N⁰ S-77-47, Dirección de Investigación, Universidad Austral de Chile.I would like to thank Dr J. M. Cei for collecting the Argentinian toads. Mr N. Diaz collected the specimens from Santiago, Chile.The technical assistence of Sonia Lacrampe is acknowledged with appreciation.     

The question of lens regeneration from parts of the optic vesicle in the chick embryo

Résumé Après excision du cristallin des yeux d'embryons de poulet de 48–72 h d'incubation les vésicules optiques étaient cultivées in vitro ou sur le chorio-allantoöide d'autres embryons. Elles étaient cultivées en quelques cas seules et en autres cas avec l'ectoderme céphalique. Nouveaux cristallins ne se formaient que si l'ectoderme céphalique était inclus avec la vésicule optique et si les vésicules étaient prélevées des jeunes embryons. On peut conclure que les nouveaux cristallins se forment dans l'ectoderme céphalique par induction. Nous n'avons trouvé aucune évidence de régénération du cristallin des tissus de l'oeil.

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This work was supported by a grant from the National Research Council of Canada to D. J. McCallion.     

Structural correspondence between nucleolus- and sphere-organizing regions of the lampbrush chromosomes and secondary constrictions of the mitotic chromosomes

Riassunto Le regioni nucleolo-e sfera-organizzatrici dei «lampbrush chromosomes» diTriturus alpestris apuanus corrispondono a costrizioni secondarie presenti sui rispettivi cromosomi mitotici. Questo dato ripropone l'interesse per lo studio dell'origine e del significato delle sfere negli ovociti in accrescimento.

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With financial support by C.N.R., Rome.     

Structure of the centromere in telocentric chromosomes

Résumé Les centromères terminaux se présentent comme formés par un chromomère. Leur structure apparaît comme la moitié de la structure centromérique des chromosomes métacentriques.     

Mutagenicity experiments with the tranquillizer meprobamate inDrosophila melanogaster and in human leukocyte chromosomes in vitro

Zusammenfassung Mutagenitätsuntersuchungen mit Meprobamat anDrosophila melanogaster (X-chromosomale rezessive Letalmutationen, Chromosomenaberrationen in reifen Spermien) und an menschlichen Leukozytenchromosomen in vitro ergaben keine Anhaltspunkte für eine genetische Wirksamkeit dieser Substanz.     

Increased silver stainability of metaphase chromosomes from rat hepatocytes during in vivo hepatocarcinogenesis

Silver stainability of metaphase chromosomes was studied in hepatocytes obtained from rats exposed or not to a partial or complete carcinogenic treatment with diethylnitrosamine and phenobarbital. An increased hyperstaining is reported in the carcinogen-treated animals.     

Nonrandom assortment of centromeres with implications regarding random assortment of the chromosomes

Zusammenfassung Das Vorkommen «umgekehrter Koppelung» (reverse linkage) bei der Hefe deutet auf die Möglichkeit, dass die Zentromeren nicht homologer Chromosomen zu Beginn der Meiose eine Synapsis eingehen und dementsprechend nicht unabhängig voneinander auf die beiden Tochterkerne der ersten meiotischen Teilung verteilt werden.

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This work has been supported by research grants from the National Cancer Institute of the National Institutes of Health, U.S. Public Health Service C-1179 and C-2140.     

Increased silver stainability of metaphase chromosomes from rat hepatocytes during in vivo hepatocarcinogenesis

Summary Silver stainability of metaphase chromosomes was studied in hepatocytes obtained from rats exposed or not to a partial or complete carcinogenic treatment with diethylnitrosamine and phenobarbital. An increased hyperstaining is reported in the carcinogen-treated animals.     

Permissivity of the rat (Rattus rattus) of Guadeloupe with regard to Schistosoma mansoni and evidence for migration of adult schistosomes to the lungs]

In contrast to the laboratory Rat, the Rat (Rattus rattus) of Guadeloupe is a favorable host for the life cycle of S. mansoni: the parasite population is maintained at a high level (between 8 and 16% in this host until the 16th week and reproduces normally). The evolution of the parasitose is marked, shortly after the 8th week, by a transfer of schistosomes from the liver to the lungs.     

Reaction of lysozyme with dithiothreitol and with other mercaptans

Riassunto Sono misurate le velocità di reazione della lisozima con 0.05M ditiotreitolo, HSCH₂CH₂OH, (HSCH₂CH₂COO^–) e H₂SCH₂CH₂NH₂ in tampone borace di pH 10 e in alcune altre concentrazioni e pH. La cinetica della reazione col ditiotreitolo è differente da quella con HSCH₂CH₂OH e viene data una interpretazione di questo fenomeno.

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This work was aided by a grant and a Career Development Award (to G.G.) from the National Institutes of Health, U.S. Public Health Service.     

The origin of the brown frogs with 2n=24 chromosomes

Late replication and C-banding analyses of somatic metaphase chromosomes were attempted on three species of brown frogs with 2n=26 chromosomes (Rana japonica, R. tsushimensis andR. temporaria), and three with 2n=24 chromosomes (R. ornativentris, R. dybowskii andR. chensinensis), which are distributed in the Palearctic region. The late replication banding patterns were highly conserved in these species. Four chromosome inversions were demonstrated inR. ornativentris, two inR. dybowskii and two inR. tsushimensis. From a detailed comparison of late replication and C-banding patterns between the 2n=26 and the 2n=24 species, it was found that an end-to-end fusion of two small chromosomes (nos 11 and 13) in an ancestral 2n=26 species may have produced the medium-sized no. 6 chromosome of the 2n=24 species.     

Junctions of polytene chromosomes and the inner nuclear membrane

Summary Polytene chromosomes in salivary gland nuclei from chironomid larvae of defined stages are connected along their entire length, by some 100 chromatin fibers, to the inner nuclear membrane.Dedicated to Professor Friedrich Mechelke on the occasion of his 60th anniversary.