J. M. Echave Llanos

Ultrastructure of STH cells of the pars distalis of hepatectomized mice

SummaryAn electron microscopic analysis was performed on the pars distalis of the hypophysis of hepatectomized mice. Intact and sham operated mice served as controls. The STH cells presented striking changes that were most intense and widespread in those animals sacrificed at midnight of the second day after hepatectomy. These changes can be summarized as follows: 1) Hypertrophy of the Golgi complex with increased number of immature granules within the Golgi zone. This change appeared also in otherwise unmodified STH cells. 2) Strong dilatation of the endoplasmic reticulum whose cisternae contained much electron dense material. 3) Granules with partially diminished electron density, some of them in spatial relation with the plasma membrane and others swelling and bursting within the cytoplasm. All transitions between unchanged 350–400 mμ granules and extremely altered ones, were seen. 4) Release sites, characterized by dense zones in the plasmalemma, close to aggregates of electron lucent microvesicles, and almost empty granule membranes. 5) Increase in the density of the mitochondria which appeared grouped near the Golgi zone. 6) Increase in the number of large lysosomes of the autophagic vacuole type. 7) Irregular nuclear outlines. These data suggest increased synthesis and release of growth hormone in STH cells stimulated by hepatectomy.

Circadian variations of DNA synthesis, mitotic activity, and cell size of hepatocyte population in young immature male mouse growing liver

SummaryCircadian variations in DNA synthesis after tritiated thymidine and autoradiography, mitotic activity with the Colcemid method, and cell size, represented inversely by the number of cells per microscopic field, are reported for the hepatocyte population of the young immature growing liver of the male mouse. The peak of DNA synthesis is at 04:00 hours and that of mitotic activity at 12:00 hours. The 8-hour interval between the two peaks is considered, in agreement with other authors, a good estimation of the lag period between DNA synthesis and the initiation of mitotic activity.The minimum cell number per microscopic field, which is considered to correspond to the maximum cell size, coincides with the starting of the circadian mitotic wave. The significance of this coincidence and the relationships of the circadian curves of the parameters controlled with the feeding pattern and food consummatory curve of standardized mice, are discussed.

Circadian rhythm in the feeding activity of Oxymycterus Rutilans. Role played by light and food availability

Abstract A circadian rhythm in the feeding activity of an argentine wild rodent (Oxymycterus Rutilans) is described.The role played by light and food supply in the synchronization of this rhythm is analyzed. The rhythm is regularly maintained in singly caged animals, with light reaching every corner of the cage and with enough and constant quantity of food.

Growth hormone release after hepatectomy.

El plasma de ratones hepatectomizados, recogido a la medianoche del segundo día de la regeneración, estimula, al igual que la hormona de crecimiento pura, la síntesis de ADN de los hepatocitos y células litorales del hígado del ratón adulto intacto. Este efecto no se observa con el plasma de ratones intactos sacrificados a medianoche ni con solución fisiológica. Se sugiere que el factor estimulante del plasma de ratones hepatectomizados en hormona de crecimiento.

Circadian rhythm in the gastric content of normal and hepatectomized mice

Abstract A circadian rhythm in gastric content is reported in normal mice. The high values appear in the middle of the activity (dark) period and the trough figures are seen at the end of the rest (light) period. The rhythm appears delayed during the first 24‐hr period after hepatectomy but reappears with its normal timing during the second 24‐hr period.

24‐hour variations in DNA of the liver in young and adult male mice

Abstract Higher values of liver DNA content, determined with the diphenylamine reaction, are found in young and adult standardized male mice, during the activity (dark) period, than during the resting (light) period. The rise of DNA concentration, at the starting of the activity period coincide with a rise in DNA synthesis in hepatic and mesenchymal liver cells, measured with TH3 and autoradiography. Young mice have more DNA per g wet or dry liver and per 100 g body weight than adult mice. Adult mice have more DNA per liver than young mice but the difference is proportionally lower than the difference in the weight of the liver.

Variations in the golgi complex of mouse somatotrops at different times in a 24-hour period.

El aparato de Golgi de las células somatotropas de la pars distalis de la hipofisis del ratón, presenta importantes diferencias ultraestructurales en distintos momentos de un período de 24 horas. Es pequeño a mediodia y marcadamente hipertrófico a mediodía y 6 de la tarde.

Inhibiting effect of a hepatoma extract on the mitotic rate of regenerating liver

SummaryAqueous tumor extracts were prepared by the homogenization of a fast-growing, undifferentiated, transplantable malignant murine hepatoma in distilled water. After centrifugation, an aliquot of 0.01 ml of the supernatant g body weight was injected intraperitoneally into partially hepatectomized mice. Control animals were injected with saline. Groups of mice were killed at various times in relation to the hepatectomy. Four h before killing the animals were given Colcemid (1 μg/g body weight). The number of Colcemid-arrested mitoses in the hepatocytes and in the littoral cells, respectively, were counted in 140 microscopic fields. The extract significantly inhibited the mitotic rate in hepatocytes when the injection was given between 22 h before, and up to 26 h after hepatectomy. In the littoral cells, a slight initial stimulation was followed by a slight but significant inhibition which occurred when the injection was given at hepatectomy or until 18 h after hepatectomy. The effect was not modified by exposing the extracts to temperatures of 47° C for 30 min or 22° C for 24 h, but 10 min of boiling destroyed their inhibitory effect. Lyophilization and storing at —18° C for up to 4 weeks did not modify the effect. The mitosis-inhibiting effect was also measurable when the extract was injected subcutaneously. There was an almost linear dose-response curve. The results are discussed in relation to circadian rhythms, the pattern of liver cell proliferation after hepatectomy, and recent similar reports from the literature. The conclusion is drawn that extracts of a hepatoma contain one or more growth-inhibitory factors significantly active on regenerating liver cells, and less significantly on littoral cells.

The pars distalis of the pituitary as a source of liver growth stimulating factors during liver regeneration

SummaryPlasma and pituitary extracts from hepatectomized mice as well as pure growth hormone, stimulate DNA synthesis in hepatocyte population of adult intact mouse liver. This effect is not observed with plasma and pituitary extracts from intact or sham operated mice. The corresponding effects on the litoral cell population of the liver follow the same pattern, but the results are not so clearcut as in the hepatocyte population. The possibility that growth hormone, released by STH cells of the pituitary, is one of the factors responsible for the stimulating effect of plasma during liver regeneration, is discussed on the basis of the present results and of those already reported in the literature.

Release of growth hormone from somatotropin producing cells of hepatectomized mice without the participation of the Golgi complex

El reticulo endoplasmico de las celulas somatotropas del raton hepatectomizado se encuentra muy dilatado y contiene material denso en el interior de sus cisternas. Estas se observan frecuentemente en contacto con la membrana celular en zonas en que ésta y el intersticio presentan un aumento de densidad. Se sugiere un mecanismo directo de secreción de la hormona sintetizada en exceso en el reticulo endoplasmico, sin pasar previamente por el complejo de Golgi.