César L.A. Gómez Dumm

Regression of Isoproterenol-Induced Cardiac Hypertrophy by Na+/H+ Exchanger Inhibition

Abstract— Cardiac hypertrophy is often associated with an increased sympathetic drive, and both in vitro and in vivo studies have demonstrated the development of cardiomyocyte hypertrophy in response to either [alpha]‐ or [beta]‐adrenergic stimulation. Because an association between the Na+/H+ exchanger and cellular growth has been proposed, this study aimed to analyze the possible role of the antiporter in isoproterenol‐induced cardiac hypertrophy. Isoproterenol alone (5 mg/kg IP once daily) or combined with a selective inhibitor of the Na+/H+ exchanger activity (3 mg · kg‐1 · d‐1 BIIB723) was given to male Wistar rats for 30 days. Sex‐ and age‐matched rats that received 0.9% saline IP daily served as controls. Echocardiographic follow‐up showed a 33% increase in left ventricular mass in the isoproterenol‐treated group, whereas it did not increase in the isoproterenol+BIIB723‐treated group. Heart weight–to–body weight ratio at necropsy was 2.44±0.11 in controls and increased to 3.35±0.10 (P <0.05) with isoproterenol, an effect that was markedly attenuated by BIIB723 (2.82±0.07). Intense cardiomyocyte enlargement and severe subendocardial fibrosis were found in isoproterenol‐treated rats, and both effects were attenuated by BIIB723. Myocardial Na+/H+ exchanger activity and protein expression significantly increased in isoproterenol‐treated rats compared with the control group (1.45±0.11 vs 0.91±0.05 arbitrary units, P <0.05). This effect was significantly reduced by BIIB723 (1.17±0.02, P <0.05). In conclusion, our results show that Na+/H+ exchanger inhibition prevented the development of isoproterenol‐induced hypertrophy and fibrosis, providing strong evidence in favor of a key role played by the antiporter in this model of cardiac hypertrophy.

Sequential Morphological Changes in Pancreatic Islets of Spontaneously Diabetic Rats

This study describes the sequential morphological changes in pancreaticislets from 1-, 6-, and 18-month-old male eSS rats, as compared to aged-matched control animals. Spontaneous diabetes mellitus was confirmed in 6- and 18-month-old eSS rats after an oral glucose tolerance test. Lightmicroscopic immunocytochemical and morphometric techniques were used to study islet-cell populations. The pancreas was normal, and the morphometric methods did not reveal significant changes in islets from 1-month-old rats. However, 6-month-old eSS animals showed disruption of islet architecture and fibrosis in the stroma. The volume density (Vvi) of endocrine tissue and the Vvi and percentage of B cells were increased, whereas the Vvi of exocrinetissue and the Vvi and percentage of A cells were diminished. Eighteen month-old eSS rats also exhibited conspicuous islet lesions. Nevertheless, the Vvi of endocrine tissue and the Vvi and percentage of B cells were diminished, while the Vvi of exocrine tissue and the Vvi and percentage of D cells were increased. Our results provide further quantitative evidence for the sequentialmor phological events occurring in the pancreatic islets of a useful animalmodel of diabetes mellitus.

Catecholamine Metabolizing Enzymes and Synthesis of Dopamine in Normal and Grafted Pituitary Partes distales

The presence of enzymatic activity (tyrosine hydroxylase, dopa-decarboxylase, dopamine-beta-hydroxylase, monoamine oxydase and catechol-O-methyl transferase), as well as dopamine (DA) content and DA synthesis from tyrosine and dopa, were investigated in intact rats partes distales and in grafts (both estrogenized and nonestrogenized). Counts of prolactin cells showed the following regression in the number of these cells: estrogenized grafts greater than nonestrogenized grafts greater than intrasellar intact glands. Tyrosine hydroxylase activity was not found in intact glands, but this enzyme was detected in the two types of grafts. An approximate correlation could be established between the number of prolactin cells and the diverse enzyme activities. Dopamine was not synthesized from tyrosine in intact glands, but it occurred in the transplants. However, when dopa was used, both intact and grafted glands produced dopamine. Estrogen administration decreased dopamine content in all the glands investigated. The significance of these results in relation to the physiology of the pars distalis is discussed.

Altered Functional Responses with Preserved Morphology of Gonadotrophic Cells in Congenitally Athymic Mice

Neonatal thymectomy or congenital absence of the thymus induces severe reproductive deficiencies in female mice, which are associated with reduced levels of circulating and pituitary gonadotropins. In contrast, the reproductive function is well preserved in nude males. It was therefore of interest to assess gonadotrophic cell morphology and function in congenitally athymic male mice. Circulating gonadotropins were measured under basal and stressful conditions, taking as a reference their haired counterparts. Adult normal (+/+), heterozygous nude (nu/+), and homozygous (nu/nu) CD-1 mice were subjected to 1-h immobilization stress. Serum levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were assessed by RIA at 0, 30, and 60 min poststress. Athymic animals showed significantly lower basal levels of serum LH and FSH than their heterozygous littermates. Immunohistochemical assessment of LH and FSH cell populations revealed a normal morphology and cell number in the athymic animals compared to their normal littermates. Immobilization stress induced a significant reduction in gonadotrophin levels, particularly LH, in normal mice but had only a weak effect in athymic animals. It is concluded that congenital athymia in the adult male mouse is associated with decreased basal levels of serum LH and FSH, in the presence of a normal gonadotroph number and morphology. The anomalous responses of athymic mice to stress do not appear to be due to primary hypopituitarism but, rather, to an altered modulation of pituitary hormone secretion. .

Quantitative morphological changes in endocrine pancreas of rats with spontaneous diabetes mellitus

SummaryThe present study describes the cytopathology of the pancreatic islets in 18-old male eSS rats with spontaneous diabetes mellitus as compared to aged-matched normal animals. Lightmicroscopic immunocytochemical and morphometric techniques were used to study islet-cell populations, while quantitative methods were employed specifically for the analysis of B-cell ultrastructure. The diabetic rats showed disruption of the islet structure and fibrosis in the stroma. The volume density (Vvi) of endocrine tissue and the Vvi and percentage of B cells were diminished, whereas the Vvi of exocrine tissue and the Vvi and percentage of D cells were increased. The number of medium and large islets as well as their mean volume (μm3) decreased in these animals. Pancreatic B cells from eSS rats showed an increase in the Vvi of endoplasmic reticulum, immature secretory granules and lysosomes. Conversely, the Vvi of total secretory granules and microtubules appeared diminished. The current observations contribute to our understanding of this useful animal model of diabetes mellitus, in the attempt to clarify the pathogenesis of the disease.

Morphological and Functional Changes in Several Endocrine Glands Induced by Hypothyroidism in the Rat

The effect of hypothyroidism upon the morphology and the function of several endocrine glands was studied in radiothyroidectomized male rats. It was found that T3, T4, insulin, prolactin and corticosterone levels were significantly lower in hypothyroid rats. TSH levels were significantly higher in these animals while no changes were depicted in testosterone levels. The administration of T4 drew back to normal range the above-mentioned altered serum hormone levels. The studies performed with light microscopy revealed alterations only in the TSH secretory cells of the adenohypophysis. Conversely, when using the electron microscope to study the different endocrine glands, clear alterations were depicted in the TSH and prolactin secretory cells of the adenohypophysis, as well as in the pancreatic B cells and the cells of the zona fasciculata of the adrenal cortex. No abnormal changes were demonstrable at the level of the seminiferous tubules of the testis. All the above morphological changes were corrected by the administration of T4 to hypothyroid rats. These results suggest that the hypothyroid state is a complex hormonal dysfunction rather than a single hormonal defect. The secretory alterations are accompanied by fine cellular alterations in the corresponding glands.

On the presence of conspicuous electron dense bodies in the pinealocytes of the pig

SummaryThe pinealocytes of the pig contain a large number of aldehydefuchsin positive granules. In order to determine their nature an ultrastructural study was carried out. Numerous bodies having a maximal diameter of about 1,600 nm were found. These elements showed a great variety of internal structure, ranging from a “homogeneous” content and amorphous dense aggregates to lamellate bodies. Although only a few of them displayed a positive reaction for acid phosphatase, their morphological appearance strongly suggests that they belong to the lysosomal system.

Effects of Androgens and Antiandrogens on the Quantitative Immunohistochemistry of Gonadotrope Cells in Prepubertal Male Rats

In the male rat, androgens are involved in the feedback regulation of gonadotropin synthesis and secretion. Specific androgen-receptor blockade by the nonsteroidal antiandrogens, flutamide and Casodex, has proven to be a valid tool for studying androgen effects in vivo. The aim of the present study was to investigate the effect of antiandrogen administration at the pituitary level by evaluating the changes in gonadotropes through quantitative immunohistochemistry, and by comparing these alterations with the effect of androgen deprivation by castration either with or without subsequent androgen replacement. Male Sprague-Dawley rats (23 days old) were randomly divided into 5 groups for the following treatments: (a) controls; (b) flutamide-injected (10 mg/rat/day in a gelatin vehicle); (c) Casodex-injected (10 mg/rat/day in an oil vehicle); (d) castrated, and (e) castrated and dihydrotestosterone propionate-replaced (40 µg/rat/day in an oil vehicle). Groups were then sacrificed after 10 days of maintenance under each condition. Pituitaries were fixed in Bouin’s fluid and embedded in paraffin. Serial sections (4 µm) were obtained at different levels and immunostained by means of the primary murine monoclonal antibodies anti-FSH and anti-LH and a peroxidase-mediated EnVision System (Dako). Measurements of volume density (VD) and individual mean cell area were made by means of an image-analysis system (Imaging Technology, Optimas). Serum FSH and LH levels were determined by radioimmunoassay (RIA). Serum gonadotropin levels, VD, and mean cell area increased significantly in the flutamide-treated, Casodex-treated, and castrated groups (p < 0.05). Androgen replacement in the castrated rats, however, reduced VD, mean cell area, and serum gonadotropins to levels comparable to those of controls. We conclude that either androgen blockade by antiandrogens or castration produce an enhancement in the gonadotrope cell population in prepubertal rats, as shown by an increase in both VD and mean cell area, as well as an elevation in FSH- and LH-immunoreactive cells. These observations correlate well with the changes found in the levels of circulating gonadotropins as measured by RIA.

Immunohistochemical and radioimmunological study of pituitary gonadotrophs during aging in male rats.

The impact of aging on pituitary gonadotrophs in rats is little known. We therefore undertook a quantitative immunohistochemical assessment of the follicle-stimulating hormone (FSH) and luteinizing hormone (LH) immunoreactive cell population in the pituitaries of young (4 months), old (20 months) and senescent (29 months) male rats. In addition, an attempt was made to correlate morphometric parameters with serum levels of FSH and LH. Gonadotrophs were immunostained by the peroxidase-antiperoxidase method using anti-rat LH and anti-rat FSH rabbit sera as primary antibodies. Hormones were measured in serum by specific radioimmunoassays. Analysis of morphological parameters revealed, for both types of gonadotrophs, a marked age-related reduction in cell density, volume density and surface density. Gonadotroph cell perimeter and area showed a trend towards an increase from 5 to 20 months of age but appeared drastically reduced in the 29-month-old rats. Basal serum levels of LH and FSH showed a significant increase from 4 to 20 months of age but remained at the same level in the senescent rats. The correlation between serum levels of gonadotropins and gonadotroph morphometric parameters was low in all cases. We conclude that in male rats aging brings about a significant reduction in both the number and size of pituitary gonadotrophs which, nevertheless, seem to be still capable of keeping appropriate basal levels of circulating LH and FSH.

Quantitative Ultrastructural Study of Somatotropic Cells in Malnourished Weanling Rats

A quantitative ultrastructural study of somatotropic cells was carried out in 21-day-old malnourished rats after maternal food restriction during the nursing period. Changes represented mainly by a reduced cytoplasmic mass and diminished secretory material were found. A decrease in growth hormone secretion of malnourished weanling rats is suggested.