Revista de Biología Tropical Vol.32 (2)
URI permanente para esta colección
Examinar
Envíos recientes
Ítem Estudios cariológicos de cinco especies de serpientes costarricenses de la familia colubridae(1984) Solórzano López, Alejandro; Gutiérrez, José María; Cerdas Fallas, LuisThe karyotypes of five species of colubrid snakes from Costa Rica are as follows: Imuntodes cenchao and Drymobius margaritiferus have a diploid number of 36, with 16 macro- and 20 microchromosomes. The fourth pair is heteromorphic in females of I. cenchoa, with a metacentric Z and a submetacentric W chromosomes. Karyotypes of Erythrolampius bizonus and Leimadophis epinephalus have 28 chromosomes, without a clearcut separation between macro- and microchromosomes. In the case of E. bizomus, the fourth pair contains the sex chromosomes Z and W, both are submetacentric, but the W is smaller. Xenedon rabdocephalus has a diploid number of 34 chromosomes (22 macro- and 12 microchromosomes); pair 3 is heteromorphic in femaJes, with a submetacentric Z and a smaller metacentric W. The karyotype of X. rabdocephalus may be derived from a primitive karyotype by means of reduction in the number of microchromosomes and centric fissions of two pairs of metacentric autosomes.Ítem Mecanismo de acción de miotoxinas aisladas de venenos de serpientes(1984) Cerdas Fallas, Luis; Gutiérrez, José MaríaBiochemically and pharmacologically, myotoxins isolated from snake venoms can be placed in four main groups: myolaxic phospholipases A, low molecular weight basic toxins, cardiotoxins, and hemorrhagic myotoxins. The myotoxic phospholipascs A notexin, taipoxin, crotoxin, and Bothrops asper myotoxin induce muscle necrosis by first affecting the integrity of the plasma membrane, thereby inducing a calcium influx that culminates in cell death. The small basic myotoxin crotamine acts on the voltage-sensitive sodium channels of skeletal muscle sarcolemma, inducing a sodium influx which is responsible for depolarization and contraction of skeletal muscle, as well as for vacuolization of sarcoplasmic reticulum. Cardiotoxins are basic membrane-active polypeptides that disorganize the structure of membranes; the myotoxic activity of cardiotoxins results from their ability to disrupt skeletal muscle sarcolemma. Finally, two hemorrhagic toxins (hemorrhagic toxin b and viriditoxin) are myotoxic; apparently, they induce myonecrosis secondarily to ischemia which develops in muscular tissue as a consequence of the hemorrhagic action of these toxins.Ítem Rotavirus y campylobacter fetus jejuni asociados a un brote de diarrea en terneros(Revista de Biología Tropical 32 (2) 303-304, 1984-04-27) Simhon Edgar, Alberto; Gamboa Coronado, María del Mar; Mata Jiménez, LeonardoRotaviruses and Campylobacter fetus jejuni are ubiquitous agents of diarrheal disease in animals and humans. Under natural conditions they do not seem to cross inter-species barriers; a zoonosis has not been documented for man. However, animal rotaviruses might contribute to the emergence of new reassortment strains in view of their segmented genome, and thus, produce new antigenic variants. On the contrary, Campylobacter fetus jejuni produces a true zoonosis. Man acquires bacilli by ingesting water and foodstuffs contaminated with feces from infected animals. In an outbreak of diarrhea in 22 calves, rotavirus was detected in 8 (36%) and Campylobacter in 6 (27%). Three (14%) calves experienced double infection. There were no human cases involved in this outbreak.