The karyotype ofOxymycterus sp (Cricetidae,Rodentia) from Central Brazil

Cytogenetical data, including G-, C-bands and NORs distribution ofOxymycterus sp (2n=54; FN=64) captured in Distrito Federal, state of Goiás, Central Brazil are presented. Our results are compared to the karyotype information already available on this genus.     

Karyotypes of two species of insectivora from Taiwan (Insectivora,Soricidae)

Summary The karyotypes of two Insectivora species from Taiwan are described here for the first time.Soriculus caudatus fumidas has 2n=40 chromosomes, FN=52 andAnourosorex squamipes yamashinai has 2n=50 chromosomes, FN=96. ForA. s. yamashinai the G- and C-banding pattern are presented.Acknowledgment. The authors are grateful to Dr P. T. Tseng, and Mr H. M. Lin of Taiwan Provincial Institute of Infectious Diseases and to Prof. I. Sawada of Nara University of Education for their help during the collection of the material and their encouragement.     

Chromosomal evolution and zoogeographic origin of southeast Asian shrews (genusCrocidura)

To the origins and evolution of Indomalayan shrews, we investigated the chromosomal variations of 14 species ofCrocidura from SE Asia. Intraspecific polymorphism was mainly due to variation in the number of short chromosomal arms butC. lepidura andC. hutanis showed a polymorphism due to a centric fusion. The undifferentially stained karyotypes were similar in 9 species, all possessing 2n=38 and FN=54–56 (68);C. fuliginosa had 2n=40 and FN=54–58. These karyotypes are close to the presumed ancestral state for the genusCrocidura. Four species from Sulawesi had a reduced diploid number (2n=30–34), a trend not observed among other SE Asian species but present in few Palaearctic taxa. Compared to the apparent stasis of karyotypic evolution observed among other SE Asian species, the high degree of interspecific differences reported among Sulawesian shrews is unusual and needs further investigation.Stasis and reduction in diploid number found in both Indomalayan and Palaearctic species suggest that these two groups share a common ancestry. This is in sharp contrast to most Afrotropical species which evolved towards higher diploid and fundamental numbers. The zoogeographical implications of these results are discussed.     

Chromosomal homology in southern Akodon

Summary Differential staining (G and C) of southern South AmericanAkodon are presented.A. olivaceus, A. longipilis andA. sanborni all have the same karyotype (2n=52, NF=58). A virtually identical band sequence is observed. This situation is interpreted using the canalization model of chromosomal evolution which stresses an optimum karyotype for each adaptive zone. Despite the high degree of conservation of the chromosome structures, the specific status of these species is supported by maintenance of distinctness when they occur in areas of sympatry.The research was partially supported by Proyecto de Investigación I-78-86, Dirección de Investigación, Universidad Austral de Chile and Programa Especial de Citogenética, U. de Chile sede Norte, Santiago, Chile.     

Sex determining mechanismXY 1Y2 inArtibeus lituratus lituratus (Chiroptera-phyllostomidae)

Resumen En el murciélagoArtibeus lituratus lituratus el nÚmero de cromosomas es de 2n=30 en la hembra y de 2n=31 en el macho. El mecanismo de determination del sexo esXX/XY ₁Y₂. La translocación de un autosoma alX resultó en la diferenciación del neo-Y. Son descritos los aspectos del comportamiento del trivalente sexual durante la meiosis. Estos son comparados a los que presenta la especieNoctilio leporinus (2n=34) cuyo mecanismo esXX/X Y.

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This work was supported by Public Health Service Research Grant No. GM-14577-03 from the National Institute of General Medical Sciences and by the Fundo de Pesquisas do Instituto Butantan. R. F. B. holds a FAPESP training fellowship.     

Elektrophoretische Differenzierung von Säure- und Labcasein

Summary The electrophoretic patterns of normal casein (precipitated with acid from cow's milk) and of rennetcasein obtained in a veronal buffer at ap _H of 7.3 are remarkably different from each other. The ascending boundary of the -fraction of casein treated with rennet splits off into two peaks showing the presence of two subfractions (₁ and ₂). The proportion of quantity of the faster (₁) and of the slower (₂) subfraction was found to be about 0.9:1. The -component of casein which was not treated with active rennet behaved under the same conditions electrophoretically uniform.     

Cytogenetics of South American akodont rodents (Cricetidae). V. Segregation of chromosome No. 1 polymorphism inAkodon molinae

Summary Akodon molinae is polymorphic with 2n=42, 43, 44, where the metacentric autosome No. 1 is homologous to 2 acrocentrics 1a and 1b. Matings between 2n=43 heterozygotes 1/1a, 1b gave a surplus of 1/1 offspring, a moderate reduction of heterozygous and a strong reduction of homozygous 1a, 1b/1a, 1b offspring. The latter type also has a highly reduced fertility.This work was supported by grants from the Consejo Nacional de Investigaciones Científicas y Técnicas, the Comisión de Investigaciones Científicas de la Provincia de Buenos Aires and the Organización de Estados Americanos.     

A diploid population of the polyploid amphibianOdontophrynus americanus and an artificial intraspecific triploid hybrid

Resumen La ocurrencia de poliploidia ha sido relatada en anuros de la familia Ceratophrydidae incluyendo la especie tetraploideO. americanus (4n=44). En una área geográfica distinta, sin embargo, fue observada una población diploide deO. americanus (2n=22). Fueron obtenidos híbridos intraespecíficos triploides (3n=33) por cruzamiento de ejemplares diploides y tetraploides deO. americanus.     

A chromosome study ofScarites occidentalis (Coleoptera,Caraboidea)

Summary Scarites occidentalis has 2n=41 (females 2n=42), n=19+X₁X₂Y. This multiple sex-chromosome system and other karyotypic characteristics suggest that this species andS. buparius share a recent common ancestor in which the sex trivalent was probably originated.Thanks are due to Dr N. Virkki for his valuable comments and his help with the English, to Dr Ramos and Dr Aparicio for discussion and advice, to Dr F. Hiraldo and M. Mañez for collecting the specimens. This work has been supported by a postdoctoral fellowship of the Consejo Superior de Investigaciones Científicas.     

Isomorphic sex-chromosomes in two venezuelan populations of the spiny rat,genusProechimys (Rodentia,Caviomorpha)

Resumen Un machoy una hembra deProechimys del Alto Orinoco (La Esmeralda) referidos aP. cherriei resultaron poseer cariotipos idénticos de 2n=26 cromosomas, sin que sea posible distinguir morfológicamente elX y elY en el macho. Un macho y 2 hembras deProechimys guyannensis guairae del Estado Aragua, proporcionaron un cariotipo de 2n=46 cromosomas, también sin par heteromórfico en el macho. Se discuten las implicaciones taxonómicas de estos hallazgos, que sugieren queP. guyannensis es una especie compleja.     

Inhibition of mammalian acetylcholinesterase by phenylmethanesulfonyl fluoride

Resumen El fenilmentano sulfonil fluoro (FMSF) 4×10^–5 M inhibe a la acetilcolinesterasa (E. C. 3.1.1.7) de cerebro de rata en más de 50%, y 9×10^–4 M más de 90%. La constante de reacción inhibidor enzima es de 4.7×10² (1 mol^–1 min^–1). La colinesterasa (E. C. 3.1.1.8) de cerebro de rata es insensible a FMSF.

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Supported by NIMH Grant No. 1 RO3 MH 19125, by Comisión Nacional de Investigación Cientiffica Proyecto No. 80, and by Comisión de Investigación Cientiffica Universidad de Chile, Proyecto No. 95.     

Chromosome replication in cells of a continuous line derived fromAedes albopictus (Skuse) larvae

Resumen El análisis del cuadro de duplicación cromosómica en una linea celular derivada del mosquitoAedes albopictus (Skuse) reveló un período G2 de 3 horas y la presencia de varias areas de duplicación tardía. La mayor parte de estas aread correspondieron a la heterocromatina constitutiva. Sin embargo, la porción distal de ambos brazos en los pares 2 y 3 mostraron duplicación tardía no asociada con la heterocromatina constitutiva. Se sugiere que estas regiones corresponden al a heterocromatina facultative.     

The occurrence of an intermediate didelphid karyotype in the short-tailed opossum (GenusMonodelphis)

Resumen Se han estudiado los cromosomas de dos especies de didélfidos del géneroMonodelphis: M. brevicaudata palliolata del norte de Venezuela yM. dimidiata de la Prov. de Buenos Aires, Argentina. Ambas especies tienen un cariotipo muy similar, compuesto de 18 cromosomas. Este cariotipo es intermedio entre el que presentanCaluromys yMarmosa (2n=14) y el deDidelphis, Philander yLutreolina (2n=22). Se postula la fisión céntrica en dos pares de submetacentricos del primer tipo, para explicar el origen del cariotipo deMonodelphis.     

Effect of alkali cations on the interaction between detergents and erythrocyte membranes

Resumen Los distintos cationes alcalinos monovalentes (145 mM) y divalentes (100 mM) modifican marcadamente el grado de hemólisis de eritrocitos humanos provocado por Triton X-100 y por desoxicolato de Na (DOC). La serie de actividad con cationes monovalentes en hemólisis por Triton es K>Rb=Cs>NaLi, y por DOC es Li>Rb=Cs>K>Na. Por el contrario, el grado de solubilización de membranas eritrocitarias producido por Triton o DOC es independiente de los distintos cationes alcalinos.     

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.     

The effects of IPC,CIPC, sevin and zectran onBacillus subtilis

Résumé On a étudié les effets phénotypiques et génotypiques de 2 insecticides (Sevin et Zectran) et 2 herbicides (IPC et CIPC) surB. subtilis. Les composés carbamiques inhibent la croissance, induisent une tendance à la formation de longues chaînes. Ils n'ont toutefois pas un effet mutagénique sur le locus de l'indole deB. subtilis.This work was supported by Research Contract No. PH 43-64-57 National Cancer Institute, National Institutes of Health, Public Health Service and is paper No. 40 published under this contract.     

Effect of sulpiride on oxygen uptake by rat's brain tissue in vitro

Resumen El Sulpiride in vitro a la concentración de 1×10^–2 M disminuye el consumo de Oxígeno en cortes de cerebro de rata. El exceso de potasio o ausencia de calcio en el medio de incubación, no modifican este efecto. En homogeneizado de cerebro total, unicamente a la concentración de 1×10^–2 M deprime el consumo de oxígeno. A las concentraciones 1×10^–3 y 1×10^–4 M no modifica el consumo de oxígeno en cortes ni homogeneizados de cerebro.     

The karyotype ofDusicyon griseus (Carnivora canidae)

Resumen Se describe el cariotipo deDusicyon griseus el cual posee una fórmula cromosómica de2N=74 y un número fundamental (NF) de 76. Por otra parte, se entrega por primera vez información acerca de los cromosomas sexuales de una especie de este género. Desde este punto de vista llama la atención que el cromosomay es un microcromosoma.     

Chromosome complement of two species of Amelinae (Dictyoptera: Mantodea)

Summary The karyotypes ofApteromantis aptera (Fuente) andAmeles decolor (Charpentier) are described. Chromosomes numbers in females are 2n=30 and 2n=28 respectively. Sex determination mechanism in both is XO-XX.     

Constitutive heterochromatin and nucleolus organizer region in the knifefish,Apteronotus albifrons (Pisces,Apteronotidae)

Summary The C-banding and silver staining of the chromosomes of the knifefishApteronotus albifrons (2n=24), demonstrated the presence of constitutive heterochromatin in the centromeric region of every chromosome, except pair 4, where the entire long arm was darkly stained, the silver stain positive nucleolus organizer region (NOR) being embedded in it.The authors are grateful to Dr Sen Pathak (University of Texas System Cancer Center at Houston, Texas, USA) and Dr Yatiyo Yassuda (Universidade de São Paulo, São Paulo, Brasil) for their suggestions. This study was supported in part by grants of the Conselho Nacional de Desenvolvimento Cientifico e Tecnológico (CNPq).