PubMed Health⌕ Search

Biomedical subjects

J G Ramos

Publications and source records attributed to J G Ramos.

At least 19 recordsLinked to original sources
PubMed2005

The estrogen receptor alpha sigma3 mRNA splicing variant is differentially regulated by estrogen and progesterone in the rat uterus.

The gene for estrogen receptor alpha (ER alpha) has been shown to be under complex hormonal control and its activity can be regulated by mRNA alternative splicing. Here we examined the regulation of ER alpha transcription and translation in the rat uterus by ovarian steroid hormones. We examined whether expression of ER alpha mRNA splice isoforms is hormonally regulated in ovariectomized (OVX) and cycling rats. Adult OVX female rats were treated daily with 17-beta estradiol (E2) (0.05 microg/rat or 5 microg/rat), progesterone (P4) (1 mg/rat) or a combination of both hormones for 4 days. Animals were killed 24 h after the last injection and uterine horns were removed. In order to determine whether ER alpha mRNA isoforms are differentially expressed under various physiological conditions, animals were evaluated at proestrus, estrus and diestrus. The ER alpha protein and mRNA were detected by immunohistochemistry and comparative RT-PCR analysis respectively. The presence of ER alpha mRNA isoforms was evaluated using a nested RT-PCR assay. In OVX control rats, ER alpha mRNA and protein levels were high, demonstrating a constitutive expression of the ER alpha gene in the uterus. When animals received P4 or the high dose of E2, a significant decrease in both ER alpha mRNA and protein was observed in the uterus. However, when rats were protein was treated with the low dose of E2, only the ER alpha down-regulated; no changes were observed in ER alpha mRNA expression. In addition to the full-length ER alpha mRNA, OVX control rat uteri expressed three shorter transcripts: sigma3, sigma4 and sigma3,4 (lacking exon 3, exon 4, or both 3 and 4 respectively). Surprisingly, when OVX animals were treated with P4, the low dose of E2 or a combination of both steroids, expression of the sigma3 isoform was completely abolished. During the estrous cycle, all ER alpha mRNA splicing variants were detected at proestrus and estrus. However, in diestrus, significant low levels of the sigma3 isoform were observed. In summary, our results suggest a dose-dependent relationship between E2 concentrations and the level of control in the ER alpha transcription-translation cascade. Moreover, the alternative splicing of the ER alpha primary transcript is influenced by the hormonal milieu, suggesting that these events could affect the estrogen responsiveness of the rat uterus during the estrous cycle.

Alternative Splicing↗
PubMed2004

Mast cells degranulation affects angiogenesis in the rat uterine cervix during pregnancy.

During pregnancy, it is essential that sufficient nutrients are supplied by the vascular system to support the dramatic modifications of the rat uterine cervix. Angiogenesis refers to the growth of new blood vessels from pre-existing microcirculation and mast cells have been associated with this process. This study examined the modifications of the vascular compartment and the distribution of mast cells on cervical tissue during pregnancy. Using disodium cromoglycate as a mast cell stabilizer, we determined the effects of the mast cell degranulation on cervical angiogenesis. Mast cell distribution and their degranulation status were evaluated by immunohistochemistry. Endothelial cell proliferation was measured by bromodeoxyuridine incorporation. Vascular areas (absolute and relative) and maturation indices were assessed by quantitative immunohistochemistry of von Willebrand factor and alpha-smooth muscle actin respectively. Mast cells were predominantly observed during the first half of pregnancy in the perivascular zones. The values of bromodeoxyuridine incorporation, absolute vascular area and vascular maturation index exhibited a significant increase throughout pregnancy. All animals that received mast cell stabilizer showed more than 40% of non-degranulated mast cells. Treated rats exhibited a decrease in endothelial proliferation and in relative vascular area; in addition, a large proportion of mature blood vessels was observed, suggesting a diminished level of new vessel formation. The effects of the mast cell stabilizer were sustained beyond the end of treatment. This is the first report that brings evidence that mast cell degranulation could be a necessary process to contribute to the normal angiogenesis of the rat cervix during pregnancy. Further investigations are needed to elucidate the possible implications of abnormal vascular development of the uterine cervix on the physiological process of ripening and parturition.

Animals↗
PubMed2003

Sex reversal effects on Caiman latirostris exposed to environmentally relevant doses of the xenoestrogen bisphenol A.

Exposure to environmental contaminants known as endocrine disruptors (EDs) alters the development and function of reproductive organs in several species. Bisphenol A (BPA) is an estrogenic chemical that leaches from dental materials and plastic food and beverage containers. BPA has been found in sewage, surface and drinking water, and therefore poses a potentially significant risk for human and wildlife. Prenatal exposure of rodents to environmentally relevant doses of BPA alters the development of the reproductive organs of male and female offspring. Species with temperature dependent sex determination (TSD) could act as sentinels of ecosystem health by providing sensitive biomarkers of endocrine disruptor's effects. We selected Caiman latirostris as an animal model to study endocrine disruption caused by BPA. The aim of this study was to determine whether exposure in ovum to BPA could cause estrogen-like effects on the reproductive system of C. latirostris. Sex determination and gonadal histoarchitecture were the endpoints evaluated after in ovum exposure to different doses of BPA and 17beta-estradiol (E(2)). We confirmed that C. latirostris is a species with TSD and additionally demonstrated that BPA causes estrogen-like developmental effects by reversing gonadal sex and altering gonadal histoarchitecture. Differences in responses to BPA and E(2) in our in vivo system were on the order of 100-fold. In contrast published in vitro studies have reported differences on the order of 10,000x or more. These results support the utility of C. latirostris, a species in which sex determination is temperature dependent, as a tool in assessing estrogenic activity in vivo and as a sentinel to monitor EDs in aquatic environment.

Air Pollutants, Occupational↗
PubMed2003

Collagen remodelling in the guinea-pig uterine cervix at term is associated with a decrease in progesterone receptor expression.

In human and guinea-pig parturition, progesterone withdrawal and estrogen action are not mediated by changes in their circulating levels. Instead, these events might be promoted by changes in the responsiveness of the uterus and cervix to progesterone and estrogen via changes in their receptors. In this study, the guinea-pig model was used to investigate whether high levels of progesterone and estrogen at term are associated with regional changes in PR and ERalpha levels in uterus and cervix. PR and ERalpha profiles were established in both subepithelium and the muscular layer of the cervix and the lower uterine horns during pregnancy, parturition and postpartum; while collagen remodelling was measured in the subepithelium. Our data showed that collagen remodelling involved in cervical ripening is temporally and spatially associated with a decrease in PR, whereas high expression of ERalpha is observed. This association was found in the subepithelium of the cervical tissue but not in the same region of the uterus. The muscular region of the cervix and uterus also present a transiently decreased expression of PR while ERalpha levels remain high. Thus, the present results indicate that, before parturition, diminished responsiveness of the cervix to progesterone might be caused by a decrease in PR levels and that this may be the mechanism of functional progesterone withdrawal. The guinea-pig was further validated as an animal model for human parturition studies.

Animals↗
PubMed2002

Phenotypic modulation of fibroblastic cells in the mucous layer of the human uterine cervix at term.

The uterine cervix is a dynamic structure with a high capacity to adapt to different, even opposing, roles during the sequence of physiological events of gestation (for example, acting as a barrier to retain the fetus during pregnancy and dilating to allow delivery at term). Histoarchitectural changes of the uterine cervix allow its successful adaptation. The aim of this study was to investigate whether fibroblastic cell plasticity, described in the lamina propria of the rat uterine cervix at term, could be observed in women too. Biopsy specimens of non-pregnant and intrapartum human cervices were studied under the transmission electron microscope, and cytoskeletal differentiation markers were identified by immunohistochemistry under the light microscope. Desmin-positive cells were present in the mucous layer of the cervix during labour. These cells displayed cytoplasmic processes (typical of myofibroblasts) that also stained positively for vimentin. The main ultrastructural features for defining the myofibroblast under the electron microscope were also observed in these cells. However, cervices of non-pregnant women contained resident fibroblasts at the same location. Examination of the differentiation repertoire of fibroblastic cells in the mucous layer of the uterine cervix resulted in the characterization of myofibroblasts at term. The implications of the plasticity of fibroblastic-myofibroblastic cells in the physiological changes displayed in the uterine cervix during pregnancy, labour and postpartum involution require further investigation.

Biomarkers↗
PubMed2001

Characterization of fibroblastic cell plasticity in the lamina propria of the rat uterine cervix at term.

Different organs contain fibroblasts with specific features and functions, indicating the complexity of fibroblast biology. In the rat cervical stroma, fibroblasts are preferentially located in the fibrous ring that surrounds the mucous layer. The purpose of this study was to investigate the morphological features and immunophenotype of fibroblastic cells of the uterine cervix in cycling, pregnant, and postpartum rats. Expression of the cytoskeletal proteins desmin, vimentin, and alpha-smooth muscle actin (alpha-SMA) were studied by immunohistochemistry. The optical density of immunohistochemical staining was quantified by image analysis. The ultrastructural features of fibroblastic cells were observed under transmission electron microscopy. Cervical fibroblastic cells always expressed vimentin and desmin but never alpha-SMA. During the first half of pregnancy (Day 5 [D5] to D14), desmin intensity values were similar to those of cycling and postpartum fibroblasts. In contrast, a strong expression of desmin was found from D15 to D22, with maximal expression at term (D23). Immunohistochemical expression for vimentin was constant throughout pregnancy and showed no differences with cycling and postpartum uterine cervices. Stromal cells from cycling and early pregnant rats displayed ultrastructural features characteristic of typical fibroblasts. In contrast, at the end of pregnancy, fibroblasts differentiated and showed increased secretory characteristics, reaching the ultrastructural features of a myofibroblast. Based on the differential expression of desmin and the electron microscopic observations, the foregoing results showed a modulation of the fibroblastic phenotype in the uterine cervix during pregnancy. To our knowledge, this is the first report that addresses the presence of myofibroblasts derived from resident fibroblasts in the fibrous ring of the rat uterine cervix. Fibroblastic-myofibroblastic cell plasticity may have implications in the physiological changes displayed in the uterine cervix during pregnancy, parturition, and postpartum involution.

Actins↗
PubMed2001

Prenatal exposure to low doses of bisphenol A alters the periductal stroma and glandular cell function in the rat ventral prostate.

Environmental estrogens (xenoestrogens) are chemicals that bind to estrogen receptor, mimic estrogenic actions, and may have adverse effects on both human and wildlife health. Bisphenol A (BPA), a monomer used in the manufacture of epoxy resins and polycarbonate has estrogenic activity. In male rodents prenatal exposure to BPA resulted in modifications at the genital tract level. Our objective was to examine the effects of in utero exposure to low, environmentally relevant levels, of the xenoestrogen BPA on proliferation and differentiation of epithelial and stromal cells on the prepubertal rat ventral prostate. To characterize the periductal stromal cells phenotype the expression of vimentin and smooth muscle alpha-actin was evaluated. Androgen receptor (AR) and prostatic acid phosphatase (PAP) expression were also evaluated in epithelial and stromal compartments. Prenatal exposure to BPA increases the fibroblastic:smooth muscle cells ratio and decreases the number of AR-positive cells of periductal stroma of the ventral prostate. In contrast, no differences in AR expression were observed in epithelial cells between control and BPA-treated groups. No changes in proliferation patterns were observed in epithelial and stromal compartments; however, the expression of PAP was diminished in prostate ductal secretory cells of rats in utero exposed to BPA. Our results suggest that prenatal exposure to BPA altered the differentiation pattern of periductal stromal cells of the ventral prostate. These findings are significant in light of the data on human prostate cancers where alterations in the stroma compartment may enhance the invasive and/or malignant potential of the nascent tumor.

Acid Phosphatase↗
PubMed2001

Relaxin has a minor role in rat mammary gland growth and differentiation during pregnancy.

Growth and differentiation of mammary gland is associated with numerous hormones and a variety of cell-cell, cell-matrix interactions. This study addressed the role of relaxin (Rlx) on these processes. Morphologic and biochemical changes that occur throughout the second half of pregnancy are reported. Temporal patterns and spatial distributions of markers useful to evaluate proliferation, secretion, and collagen remodeling were established. To evaluate the role of Rlx, an ablation/replacement animal model was used. Considering Rlx secretion pattern, two periods were selected: d 11 through d 13, and d 20 through d 23. In the stroma, the extracellular compartment showed changes associated with the lack of Rlx. Collagen remodeling within the lobuloalveolar structure, measured by a significant increase in collagen birefringence, decreased at d 12, d 21, and d 22. Parenchymal structures were less sensitive to the absence of Rlx than stroma. Epithelial cell proliferation was lower in Rlx-deficient rats only at d 12, and alpha-lactalbumin expression decreased at d 21 and d 22. Both lobuloalveolar diameter and percentage of area occupied by these structures showed no changes. In the absence of Rlx, some of the studied markers showed statistically significant differences in scattered days; these do not make clear trends. No differences were found on d 23 on any of the studied parameters suggesting that compensatory mechanisms might be activated to overcome the effects of the absence of Rlx. Unlike the critical role of Rlx either in uterine cervix dilation or in nipple development during rat pregnancy, Rlx had a minor role in growth and differentiation of rat mammary gland.

Animals↗
PubMed2000

Estrogen and progesterone modulation of eosinophilic infiltration of the rat uterine cervix.

Ripening of the rat cervix involves widespread collagenolysis that follows an eosinophilic leukocyte infiltration. The hormonal control of these events is not well understood. The aims of this study were to investigate the mechanism through which progesterone (P) and 17beta-estradiol (E(2)) modulate eosinophilic invasion and to determine if this event is protein synthesis mediated. Cervical eosinophilic invasion was measured in intact rats during the second half of pregnancy and compared with values from ovariectomized (O) pseudopregnant (PSP) rats treated with P and E(2) in doses that mimicked the levels of pregnancy. Other O-PSP rats were treated with an E(2) antagonist (tamoxifen) and the antiprogestin RU-486. To study the role of protein synthesis in eosinophilic invasion of the cervix, rats were treated with actinomycin-D (an inhibitor of mRNA synthesis), and animals were sacrificed on D21 or D22 to evaluate eosinophilic invasion. Rats treated with E(2) showed high levels of infiltration and tamoxifen blocked this E(2) effect. On the other hand, P antagonized the stimulatory effects of E(2) on eosinophilic invasion, however when the P and E(2) treated rats were injected with RU-486 the inhibitory effect of P was reversed. In intact pregnant rats a sharp rise in eosinophilic infiltration was detected on D23, 20 h after the fall of serum P. Finally, E(2) treated rats injected with actinomycin-D had no invasion of eosinophils. In conclusion, the estrogen-triggered eosinophil invasion is affected by the classic estrogen receptor antagonist tamoxifen and by the mRNA synthesis blocker actinomycin-D suggesting a genomic action of E(2). Furthermore, the estrogen effect is blocked by P and this inhibition is reversed by RU-486.

Animals↗
PubMed1999

Urinary protein/creatinine ratio in hypertensive pregnant women.

OBJECTIVES: To determine the correlation between the protein/creatinine ratio and 24-h proteinuria; to estimate the sensitivity and specificity of this ratio for the diagnosis of significant proteinuria; to establish its cutoff point with the best predictive value for the diagnosis of significant proteinuria in patients with systemic arterial hypertension. STUDY DESIGN: A cross-sectional study of 47 hypertensive patients who had been pregnant for 20 weeks or more seen at the Maternity of the University Hospital of Porto Alegre. The studied factor was the protein/creatinine ratio measured in a single random urine sample and the outcome was protein determination in 24-h urine. The level of significance was set at 0.05. RESULTS: The correlation coefficient between the protein/creatinine ratio and 24-h proteinuria was 0.94 when urine was properly collected. A receiver-operator characteristic curve was constructed to determine the sensitivity and specificity of the ratio for the diagnosis of significant proteinuria (> or = 300 mg in 24 h). Specificity and predictive positive value were 100% for a ratio > or = 0.8. The best values for sensitivity, specificity, positive predictive value, and negative predictive value in the diagnosis of proteinuria > or = 300 mg in 24 h were obtained when the protein/creatinine ratio was 0.5 (0.96, 0.96, 0.96, and 0.96, respectively). CONCLUSION: The protein/creatinine ratio measured in a single urine sample taken at random from hypertensive pregnant women showed good sensitivity and specificity for the diagnosis of 24-h proteinuria > or = 300 mg and was strongly correlated with 24-h proteinuria. A ratio of 0.5 mg/mg is predictive of significant proteinuria and can be used for the diagnosis and follow-up of hypertensive pregnant women.

Adolescent↗
PubMed1998

Role of relaxin and estrogen in the control of eosinophilic invasion and collagen remodeling in rat cervical tissue at term.

Ripening and dilation of the rat cervix at term involves a widespread reduction in the density and organization of collagen fibers following a polymorphonuclear eosinophilic invasion. These are hormonally regulated events; however, the correlation between hormonal milieu and these morphological changes is not well understood. To investigate the role of preparturient relaxin and estradiol-17ss (E2) in cervical collagen remodeling and eosinophilic infiltration, pregnant rats were either sham-ovariectomized (group C) or ovariectomized in the morning of Day 22. Ovariectomized rats were treated with E2 (group OE), relaxin (group OR), E2 plus relaxin (group OER), or hormone vehicles (group O). There were 4 or 5 animals per group. Cervices were taken from animals killed approximately 1 h before expected parturition. Five-micrometer serial sections of paraffin-embedded cervices were stained with either Sirius Red in alkaline solution to measure eosinophil infiltration or in Picrosirius to measure collagen birefringence. Ovariectomized rats treated with E2 (group OE or OER) showed high levels of eosinophilic infiltration that did not differ from those in group C intact controls. However, the values of eosinophilic infiltration in ovariectomized rats treated with relaxin or hormone vehicles (groups OR and O) were low and far below (p < 0.01) those of groups OE and C. In ovariectomized rats treated with E2 alone (group OE), the widespread reduction in collagen organization that occurred in group C controls was not observed. It was only in ovariectomized rats treated with relaxin or E2 + relaxin (groups OR and OER) that the values of birefringence were low, and they were as low as in control group C. In conclusion, this study indicates that eosinophilic infiltration and collagen remodeling in the rat cervix at term are under the control of different hormones: E2 stimulates eosinophilic invasion, and relaxin promotes a widespread reorganization of collagen fibers.

Animals↗
PubMed1998

Calciuria and preeclampsia.

Urinary calcium excretion has been reported to be diminished in preeclampsia. The objective of the present study was to determine urinary calcium excretion in pregnant patients with chronic arterial hypertension (CAH) and preeclampsia (PE), and in normotensive patients (N). Forty-four pregnant patients (gestational age, 20-42 weeks; 18 CAH, 17 PE, 9 N) were evaluated for calciuria, proteinuria, plasma uric acid and blood pressure. Patients with PE (82 +/- 15.1 mg/24 h) showed significantly lower calciuria (P < 0.05) than the group with CAH (147 +/- 24.9 mg/24 h) and the N group (317 +/- 86.0 mg/24 h) (P < 0.05, Student t-test). Plasma uric acid was significantly higher in the PE group (6.1 +/- 0.38 mg/dl) than the CAH group (5.0 +/- 0.33 mg/dl; P < 0.05), which also presented higher proteinuria levels, although the difference was not statistically significant. Diastolic and systolic blood pressure did not differ between the PE (164 +/- 105 mmHg) and CAH (164 +/- 107 mmHg) groups. Calciuria was significantly lower in the group with preeclampsia than in the group with chronic arterial hypertension. We conclude that calciuria can be a further factor for identifying preeclampsia.

Calcium↗
PubMed1997

Leukocyte infiltration and collagenolysis in cervical tissue from intrapartum sheep.

Sheep uterine cervices and cervical mucus were heavily infiltrated by neutrophils during labour, whereas samples of cervices obtained from non-pregnant controls had no infiltrate. The neutrophilic infiltrate of the sheep uterine cervix at term was not homogeneously distributed throughout the organ: luminal mucus contained more neutrophils than tissues which, in turn, displayed a differential distribution, the superficial subepithelial layer being more heavily infiltrated than the deeper submucous layers. A widespread collagenolysis was observed in the sheep uterine cervix at term. The homogeneous morphological aspect of degradation of collagen fibres throughout the whole cervical stroma contrasted with the above-mentioned differential distribution of neutrophils. On the basis of previous reports showing that collagenolysis follows the leukocytic invasion of human and rat cervices at term, a possible role for the neutrophilic infiltrate of the sheep uterine cervix is discussed.

Animals↗
PubMed1996

Dissociation in the control of cervical eosinophilic infiltration and collagenolysis at the end of pregnancy or after pseudopregnancy in ovariectomized steroid-treated rats.

Previous studies have demonstrated that during parturition the physiological ripening that permits dilation of the cervical canal is due to a widespread collagenolysis that follows a heavy polymorphonuclear leukocyte invasion of the uterine cervix. The aim of this study was to investigate whether there is any association between the ovarian steroid hormones involved in rat parturition and this phenomenon. Pregnant or pseudopregnant rats were ovariectomized (OVX) at Day 9 and then given a hormonal treatment (sufficient to maintain fetal viability) until Day 23. Cervical biopsies, taken from animals killed intrapartum or 1 h before expected parturition, were studied for eosinophilic infiltration and collagen birefringence. Intrapartum or sham-OVX pregnant rats showed a massive eosinophilic infiltration and a widespread collagenolysis as indicated by a loss of collagen birefringence. Ovariectomized pregnant rats treated with estrogen plus progesterone or with progesterone alone showed neither infiltration nor collagenolysis. In rats OVX during pseudopregnancy, estrogen given alone induced a significant infiltration of eosinophils in the cervical stroma; however, treatment with the combination of estrogen and progesterone was not able to promote eosinophilic infiltration. Collagenolysis was absent in all pseudopregnant animals. These results show that estrogen induced a cervical eosinophilic infiltration in rats but that when progesterone was added to the estrogen treatment the infiltration was not present; in addition, none of the steroid hormones assessed were responsible for the collagenolysis found in the cervical tissue at term.

Animals↗
PubMed1995

Placental bed lesions and infant birth weight in hypertensive pregnant women.

Sixty pregnant women with systemic arterial hypertension, whose pregnancies were interrupted by cesarean section at the Maternity Ward of Hospital de Clínicas de Porto Alegre between May 1989 and October 1990, were examined. Specimens of the placental bed were collected by biopsy and the presence of acute atheromatosis and/or fibrinoid necrosis was investigated. The patients were divided into two groups according to the presence or absence of vascular lesions. The biopsy findings of the placental bed were compared with adequate weight at birth related to gestational age, and to the following clinical parameters of the mother: arterial blood pressure, serum creatinine, serum uric acid and proteinuria. Twenty-seven (45%) patients presented vascular lesions in the placental bed compatible with acute atheromatosis and/or fibrinoid necrosis. The presence of vascular changes in the placental bed correlated significantly to diminished weight of the newborn, in terms of the mean weight and in terms of small-for-gestational-age infants, non-nephrotic proteinuria ( > or = 300 mg/24 h) and increased levels of uric acid ( > 5.5 mg/dl).

Adult↗
PubMed1977

The mescaline or strychnine spikes as a tool for physiological and pharmacological studies.

The all-or-nothing spikes elicited by antidromic, afferent, or direct electrical stimulation of a cortical area treated with mescaline or strychnine were studied. These potentials are most probably originated in nonsynaptic dentritic membranes and their changes in amplitude and latency can be an index of the excitability of these structures. Several factors are considered as sources of error when measurements of such parameters are made to follow their changes in different experimental conditions. When these sources of error can be eliminated, the frequency, amplitude and latency of those spikes can be taken as an index of the variations in cortical excitability under some physiological conditions. Another use of these giant potentials can be for the study of humoral and pharmacological agents.

Animals↗