Low-speed purification of human placental nuclei.

A simple method for the purification of human placental nuclei is described. Nuclei were isolated by homogenizing tissue in standard saline citrate solution in the presence of zinc chloride to stabilize the nuclear membranes, NP40 as non-ionic detergent and sodium bisulphite for inhibition of proteolytic activity. Nuclei purification was achieved by low-speed centrifugation through a discontinuous sucrose gradient. The purified nuclei were evaluated by morphological criteria using phase contrast and electron microscopy. The extent of contamination by cytoplasmic debris was estimated by Papanicolaou's staining technique. Biochemical criteria include measurements of alkaline phosphatase activity as a plasma membrane enzyme marker and DNA-dependent RNA polymerase activity for the functional integrity of nuclear components. Transcriptionally active nuclei were obtained but the yield of nuclei was low; however, this low yield is compensated by the high degree of purity, the simplicity of the method and the functional and morphological integrity of the purified nuclei.

Ultrastructure of the seminiferous epithelium of ethyl methanesulphonate-treated mouse.

Ethyl methanesulphonate (EMS) is a mutagenic alkylating agent that induces marked elevations of sperm abnormalities in mice. In this paper, we report the ultrastructural findings on the morphology of the seminiferous epithelium of mice resulting from EMS administration. Eight- to twelve-weeks-old male mice were injected intraperitoneally with EMS at 200 mg kg(-1) body weight daily for five consecutive days. Analysis of smears of epididymis and semi-thin sections of testes revealed that the more suitable specimens for the ultrastructural analysis were tissues of mice killed at the third week, following EMS administration. At this time, the spermatid was the damaged cell type. Abnormalities were mainly observed in the morphology of the nucleus, the acrosome, chromatin distribution and in the arrangement of the cytoplasmic microtubules, and binucleated spermatids were also observed. EMS has the capacity to penetrate the blood-testis barrier, and thus it can damage post-meiotic spermatogenic cells. However, morphological abnormalities could be the consequence of damage exerted on the differentiated spermatogonia stage, the most sensitive spermatogenic cell to the action of chemical agents or drugs. Our findings contribute to elucidate the action mechanism of the damage exerted by EMS administration on the germinal male cells.

Sarcocystis neotomafelis sp. n (Protozoa; Apicomplexa) from the woodrat Neotoma micropus in Mexico.

The developmental cycle of a new species of Sarcocystis (S. neotomafelis) was investigated. Cysts obtained from the muscle fibers of the woodrats were given orally to 19 laboratory newborn kittens, 5 pups and 5 crotalids. Infection developed only in newborn kittens. Macrogametes, microgamonts and immature oocysts were observed principally in the jejunum. Immature oocysts were detected at 6-21 post infection days. Based on morphological observations made by light and electron microscopy, and repeating transmission experiments, S. neotomafelis is described as a new species. Also the prevalence of cysts and the statistical frequency of sarcocystosis according to location and hosts's sex are given. This is the first species described in Mexico, and also the first report for Neotoma.

Division nuclear y presencia de microtubulos en la diferenciacion de Entamoeba invadens. / Nuclear division and presence of microtubules in the differentiation invadens

El curso de la division nuclear, asi como el tiempo en el que ocurren las divisiones nucleares durante la diferenciacion de Entamoeba invadens IP-1 fueron estudiados a traves de microscopia optica y microscopia electronica. Las divisiones nucleares ocurrieron entre las 28 y 32 h de iniciado el enquistamiento, alcanzando una maxima proporcion de aproximadamente 50 por ciento a las 30 horas.Durante la division nuclear es carecteristica la presencia de una estructura central densa que desaparecee antes de la metafase y alrededor de la cual se inicia la condensacion de cromatina. Los cromosomas, atipicos en relacion a los de eucariotes superiores, son evidentes particularmente durante la anafase. Condensaciones de cromatina asociadas a la membrana nuclear no participan en la formacion de cromosomas y la membrana nuclear permanece intacta durante todo el proceso de division nuclear. Existe la formacion de un huso intranuclear formado por microtubulos de aproximadamente 240 A de diametro. No fueron detectados centriolos