Effects of ovariectomy on the secretory apparatus in the right atrial cardiomyocytes of middle-aged mice

OBJECTIVE : The aim of the present study was to evaluate the effects of ovariectomy on the secretory apparatus of natriuretic peptides in right atrial cardiomyocytes. METHODS: Nine-month-old mice underwent bilateral ovariectomy or sham surgery. The blood exam of the ovariectomized mice showed results consistent with castrated females. Systolic blood pressure was measured after ovariectomy (9 mo of age) and at the moment of sacrifice (12 mo of age). Fragments of the right atrium were collected and prepared for electron microscopy examination. The following variables were quantified: the quantitative density and area of the natriuretic peptide granules, the relative volume of euchromatin in the nucleus, the number of pores per 10 μm of the nuclear membrane and the relative volumes of the mitochondria and Golgi complex. RESULTS: The cardiomyocytes obtained from ovariectomized mice indicated that the quantitative density and the area of secretory granules of natriuretic peptides were significantly lower compared with the sham-operated mice. Furthermore, there was a decrease in the relative volume of euchromatin, a lower density of nuclear pores, and lower relative volumes of the mitochondria and Golgi complex in the ovariectomized mice compared with the sham-operated mice. These findings suggest a pool with a low turnover rate, i.e., low synthesis and elimination of natriuretic peptides. CONCLUSION: A lack of estrogen caused hypotrophy of the secretory apparatus in right atrial cardiomyocytes that could explain the weak synthesis of natriuretic peptides in mice. Furthermore, one of the mechanisms of blood pressure control was lost, which may explain, in part, the elevated blood pressure in ovariectomized mice. .

The fine structure of the muscle-tendon junction in the rabbit

Ultra-estrutura da junçäo músculo-tendínea em diafragma de coelho. Os autores estudam, no presente trabalho, a ultra-estrutura da junçäo músculo-tendínea do diafragma de coelho. Na extremidade da fibra muscular, o sarcolema apresenta várias fendas e invaginaçöes como dedos de luva. As fibrilas colágenas do tendäo säo sinuosas e estäo inseridas obliquamente na superfície externa da lâmina basal do sarcolema. Esta disposiçäo parece estar relacionada ao mecanismo de transmissäo de tensäo. Na extremidade da fibra muscular, miofibrilas ramificam-se e prendem-se no sarcolema

A quantitative study of the myenteric plexus of the distal end of the human esophagus

The density of ganlia and nerve cells in the myenteric plexus of the last distal (12 cem. of the human esophagus was determined in six esophagi from autops y material. The density of ganglia and nerve cells in cresyl violet stained stretch preparations of twelve esophageal segments, each 1 cm. in length, were compared. The highest values were recorded in segments 4,5 and 6 cm. above the cardiac incisura. The lowest densities of ganglia and nerve cells were found in segments 1,2 and 3 cm. above the cardiac incisura. The segments contained 659-3316 perikarya/cm2; ganglia contained 3-310 cells

Fibras elásticas, elaunínicas e oxitalánicas no plexo mientérico do esôfago humano / Elastic fibers, eleaunic and oxitalanic of the human esophagus myenteric plexus

The elastic system in the myenteric plexus of the human esophagus was studied by light and electron microscopy. Elastic, elaunin and oxytalan fibers were identified by their staining characteristic a fine structural morphology. The bulk of the ganglionic sheet consists of coarse eladtic fibers and elaunin fibers. Elaunin fibers and oxytalan fibers form the intraganglionic network. The oxytalan, elaunin and elastic fibers appear to be located in area related to different stresses and deformation to which the ganglia if the myenteric plexus are exposed during the motor activity of the esophageal wall