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J M Saavedra

Publications and source records attributed to J M Saavedra.

At least 55 records · Page 3Linked to original sources
PubMed1996

Gene expression of angiotensin II receptor subtypes in the cerebellar cortex of young rats.

Both AT1 and AT2 receptors were detected in the cerebellar cortex of 2-week-old rats by [125I]Sar1-angiotensin II binding. In contrast, using in situ hybridization histochemistry we found only AT1A and AT1B but not AT2 receptor mRNA in the cerebellar cortex of young rats. Expression of AT1A and AT1B receptor mRNA coding for either receptor subtype was found in the molecular or granular cell layers. Our results suggest that AT1 receptors may be located on dendrites of Purkinje cells expressing AT1A and AT1B receptor mRNA, whereas the AT2 receptor binding in the molecular layer may be located on nerve terminals of fibers projecting to the cerebellar, cortex from distant areas.

Animals↗
PubMed1996

Angiotensin II receptor expression in the conduction system and arterial duct of neonatal and adult rat hearts.

Paralleling the classic circulating system, recent evidence has demonstrated the presence of a cardiac renin-angiotensin system, as well as the synthesis of angiotensin II in the heart. Two receptors for angiotensin II have been identified and classified as AT1 and AT2. The proportions of these receptor subtypes vary with the tissues, species and stage of development. From the results of other studies, it might be generalized that the expression of angiotensin II receptors and the proportion of AT2 receptor subtype are much higher in fetal and neonatal tissues than in the same tissues from an adult. The aim of this study was to specifically evaluate the AT1/AT2 ratio in the neonatal and adult conduction systems of rat hearts by means of quantitative autoradiogrphy. In the neonatal hearts, angiotensin II binding sites were highly concentrated in the vasculature, arterial duct, and conduction system, whereas their concentrations were barely detectable in the myocardium. Incubation with selective angiotensin II receptor ligands (losartan and CGP 42112) revealed that AT2 was the major subtype in vasculature (86 +/- 3%) and conduction system (73 +/- 4%). In the adult conduction system, the total expression of angiotensin II receptors was greatly reduced meanwhile the AT1 receptors represented the major proportion of the binding sites (80 +/- 3%). Our results demonstrated that the pattern of angiotensin II receptor expression in the conduction system of the rat heart is developmentally regulated. We suggest, as others have already, that the renin-angiotensin system plays a role during the early stage of cardiac development.

Angiotensin II↗
PubMed1996

Enteric pathogens associated with gastrointestinal dysfunction in children with HIV infection.

Infants and young children with HIV infection commonly suffer from gastrointestinal manifestations of their disease. Many HIV infected children have evidence of persistent diarrhoea, malabsorption, malnutrition or growth failure. The aetiology and pathogenesis of gastrointestinal dysfunction in HIV infected children have not been well defined. We performed immunocytochemical analyses on intestinal tissue from 19 HIV-infected children with gastrointestinal dysfunction or growth failure. None of these 19 children had microbial pathogens identified in faecal samples using standard microbiological methods. Intestinal tissues were obtained from the children by biopsy and were examined for antigens from Pneumocystis carinii, cytomegalovirus (CMV) and herpes simplex virus (HSV) using the avidin-biotin-complex immunohistochemical technique and monoclonal or monospecific antibodies. We detected at least one of these pathogens in samples from eight (42%) of 19 HIV infected children. P. carinii was the most prevalent pathogen, found in five of the eight HIV infected children. All of the children with intestinal pneumocystis infection were receiving prophylaxis directed at the prevention of pulmonary disease with this organism and none of them were undergoing active pulmonary infection. We also identified CMV antigens in intestinal tissues from four children and HSV antigens in intestinal tissues from one child. Two children were infected with more than one pathogen. On the other hand, none of these pathogens were found in the tissues obtained from 10 HIV-uninfected patients who had intestinal tissues obtained for chronic non-infectious diarrheal and inflammatory diseases (P < 0.01, Fisher's exact test). Our findings indicate that some children with HIV infection and gastrointestinal dysfunction may be infected with opportunistic pathogens despite negative analyses employing standard microbiological methods. Our study also indicates that HIV infected children can undergo intestinal infection with P. carinii despite the administration of standard immunoprophylactic regimens directed at the prevention of infection with this organism.

AIDS-Related Opportunistic Infections↗
PubMed1996

Localization of AT2 angiotensin II receptor gene expression in rat brain by in situ hybridization histochemistry.

To localize the gene expression of AT2 angiotensin II receptors in rat brain we performed in situ hybridization histochemistry using 35S-labeled antisense riboprobes. The AT2 receptor mRNA expression pattern was compared in consecutive brain sections, from 2 week old rats, with the receptor expression by means of [125I]Sar1-ANG II binding and displacement with AT2 selective ligands followed by autoradiography. Expression of AT2 receptor mRNA was found in several thalamic nuclei (ventral posterolateral, mediodorsal, central medial, paracentral, and paraventricular), the medial geniculate nuclei, the nucleus of the optic tract, the subthalamic nucleus, the interposed nucleus of the cerebellum, and in the inferior olive. In these areas the AT2 receptor gene expression corresponds well with [125I]Sar1-ANG II binding. In addition, AT2 receptor mRNA expression was found in the red nucleus where no [125I]Sar1-ANG II binding was present. No significant hybridization of the AT2 receptor antisense probe was found in septal nuclei, the locus coeruleus, the dorsolateral geniculate nucleus, or the cerebellar cortex, areas rich in [125I]Sar1-ANG II binding. Our results indicate that some brain regions may be involved in AT2 receptor formation, transporting the receptor protein to other brain areas. However, in most structures, both the formation and expression of receptors occur, suggesting the existence of local AT2 receptor circuits, or that of AT2 autoreceptors. Other structures express only the receptor protein, indicating that these AT2 receptors are produced elsewhere. Our present data are the basis for further studies on the clarification of AT2 receptor pathways in the brain.

Angiotensin II↗
PubMed1996

Increased non-angiotensin II [125I]CGP 42112 binding in rat carotid artery after balloon injury.

In this study, [125I]CGP 42112, a ligand of high affinity and selectivity for the angiotensin II AT2 receptor, was used to detect and quantify a non-angiotensin II binding site in the balloon-injured carotid artery of the rat. The amount of [125I]CGP 42112 binding was significantly enhanced in the adventitia of the injured arteries. Localization of the binding site using emulsion autoradiography and immunocytochemistry suggests that the binding sites may be expressed by macrophages in the inflamed tissue surrounding the injured artery.

Angiotensin II↗
PubMed1996

Expression of AT1A and AT1B angiotensin II receptor messenger RNA in forebrain of 2-wk-old rats.

The gene expression of angiotensin II receptor subtypes AT1A and AT1B was localized in the forebrain of 2-wk-old rats by in situ hybridization histochemistry and compared with [125I]Sar1-angiotensin II binding patterns. AT1A receptor mRNA was expressed in circumventricular organs, in hypothalamic nuclei like the paraventricular nucleus, in the lateral olfactory tract, in the basolateral amygdaloid and anterior olfactory nuclei, and in the piriform cortex. No AT1B receptor mRNA was detected in these areas. AT1A and AT1B receptor mRNA was detected in the hippocampus, cingulate cortex, and choroid plexus. No forebrain area studied expressed AT1B receptor mRNA exclusively. Most often, a good match for receptor mRNA and binding was found. In some areas, apparent mismatches suggested receptor formation elsewhere (median eminence) or receptor presence in local neuronal circuits (hippocampus, cingulate, and piriform cortex). Our results support the hypothesis that AT1A receptors are involved in the classical central functions of angiotensin II. Both AT1A and AT1B receptors may play roles in cortical and limbic system function, particularly early in development.

Animals↗
PubMed1996

Smooth muscle DNA replication in response to angiotensin II is regulated differently in the neointima and media at different times after balloon injury in the rat carotid artery. Role of AT1 receptor expression.

We have reported that angiotensin II (Ang II) infusion to rats during the third and fourth weeks after vascular injury stimulates DNA replication in a larger proportion of smooth muscle cells (SMCs) in the arterial neointima than in the underlying media or the normal arterial media. Whether this increased responsiveness to Ang II is a transient or stable property of neointimal cells after vascular injury remained unclear. The present study examined smooth muscle DNA replication in response to Ang II infusion (250 ng.kg-1.min-1 for 2 weeks) at 3 to 4, 9 to 10, or 27 to 28 weeks after balloon injury to the rat carotid artery. Control rats received Ringer's lactate. BrdU (0.8 mg.kg-1.d-1) was coinfused to label replicating DNA. The increased replicative response to Ang II in the neointima versus the normal arterial media did not persist beyond the period of rapid lesion growth shortly after injury, even in neointimal areas without endothelial regeneration. By 9 to 10 weeks after injury, replication frequencies were comparable in the neointima and the normal arterial wall. In the presence of a regenerated endothelium, neointimal DNA replication was lowered but not abolished. After the early period, however, the most marked difference may be the loss of ability of medial SMCs to respond mitogenically to systemic Ang II. As a consequence, Ang II-induced DNA replication in injured arteries was greater in the neointima than in the underlying media at all times studied after injury. DNA replication levels correlated with AT1 receptor levels in the injured artery neointima but not media, as shown by receptor binding in vascular sections at 3 and 10 weeks after injury. The growth response to systemic Ang II is differentially regulated in adjacent smooth muscle layers in the injured arterial wall in vivo via mechanisms that include, but are not restricted to, the regulation of AT1 receptor expression in SMCs.

Angiotensin II↗
PubMed1996

Longitudinal growth during the first 2 years of life in children born to HIV-infected mothers in Malawi, Africa.

To evaluate the longitudinal growth patterns of infants born to HIV-infected and uninfected mothers in Malawi, Africa, 92 HIV-infected infants, 270 uninfected infants born to HIV-infected mothers, and 686 infants born to uninfected mothers between birth and 24 months of life were studied. Weight and length were evaluated longitudinally utilizing generalized estimating equations. HIV-infected children were compared with uninfected children born to HIV-infected and uninfected mothers, and to United States National Center for Health Statistics (NCHS) growth standards. Median weight and length-for-age of seronegative infants born to either seronegative or seropositive mothers approximated the NCHS median from birth to approximately 4 months of age. Median weight and length of HIV-infected infants deviated from the NCHS median at an earlier age, and the deviation was more pronounced than was observed for uninfected infants. Mean growth curves constructed by generalized estimating equations indicated that HIV-infected and uninfected infants born to HIV-infected mothers weighed less and were smaller than infants born to HIV-uninfected mothers initially. Mean weight and length of uninfected infants attained the median of infants born to uninfected mothers by 24 months of age, while HIV-infected infants remained below this median. The difference in mean weight-for-age for HIV-infected and uninfected infants born to HIV-infected mothers was statistically significant from birth. The difference in mean length-for-age was statistically significant after 5 months of age. Thus, although infants born to HIV-infected mothers were smaller and weighed less initially, uninfected infants caught up, while HIV-infected infants remained below the median, and the deficit in weight occurred earlier in life than the deficit in length.

Body Height↗
PubMed1995

Stimulation of angiotensin II AT1 receptors in rat median eminence increases phosphoinositide hydrolysis.

The aim of our study was to determine the second messenger systems for angiotensin II in the rat median eminence. Angiotensin II AT1 receptors are highly expressed in the median eminence and binding is selectively inhibited by the guanine nucleotide GTP gamma S, indicating possible coupling to G-proteins. In male rats, angiotensin II increased phosphatidylinositol hydrolysis about 45% over basal values, with an EC50 of about 2.7 nM. This effect was antagonized by 10 microM losartan, the selective AT1 antagonist, but not by the AT2 competitor PD 123319. Conversely, angiotensin II, 1 microM, did not alter basal or forskolin-stimulated cAMP production, and failed to influence cGMP production. These results support a role for angiotensin II, through stimulation of AT1 receptors and increased phosphatidylinositol hydrolysis, in the median eminence. Angiotensin II increased the phosphatidylinositol hydrolysis not only in male rats but also in ovariectomized rats, with or without estrogen-progesterone replacement. However, angiotensin II (up to 1 microM) failed to increase the phosphatidylinositol hydrolysis in randomly selected intact female rats. Estrogen treatment did not alter the number or affinity of median eminence AT1 receptors in ovariectomized rats. The increase in phosphatidylinositol hydrolysis resulting from stimulation of median eminence AT1 receptors appears to be sexually dimorphic, but hormonal manipulations failed to point to a role for reproductive hormones in this phenomenon.

Angiotensin II↗
PubMed1995

Expression of a novel angiotensin II receptor subtype in gerbil brain.

Angiotensin II receptors are highly localized in adult gerbil brain. Apparent receptor number is high in subfornical organ, vascular organ of the lamina terminalis, nucleus of the solitary tract, hippocampus, and in the anterior pituitary gland. In the hippocampus, binding is localized to the stratum oriens, radiatum, the lacunar molecular layers of the CA1 subfield, and the molecular layer of the gyrus dentatus, with a medial to lateral and anterior to posterior gradient in receptor expression. Binding is absent from the pyramidal layer of the CA1 subfield and from the granular cell layer of the gyrus dentatus, areas rich in angiotensin IV binding. Characterization in the hippocampus revealed the presence of a high affinity receptor, sensitive to incubation with the guanine nucleotide GTP gamma S, and displaced by angiotensin II = angiotensin III < Sar1-Ile8-angiotensin II, but not by angiotensin IV or other angiotensin fragments, the AT1 receptor antagonist losartan, or the AT2 ligands CGP 42112 or PD 123177. In other brain areas, binding was equally insensitive to displacement by AT1 or AT2 ligands, with the exception of binding in the olfactory bulb, which was totally displaced by CGP 42112 and PD 123177, but not by losartan. In the gerbil, most of the brain and pituitary angiotensin II receptors are different from the AT1, AT2 and AT4 subtypes, and should be considered 'atypical' until further characterization.

Angiotensin II↗
PubMed1995

AT1A, AT1B, and AT2 angiotensin II receptor subtype gene expression in rat brain.

We localized the gene expression of angiotensin II receptor subtypes (AT1A, AT1B, and AT2) in 2-week-old rat brain by in situ hybridization using subtype specific riboprobes. AT1A receptor mRNA but not AT1B or AT2 receptor mRNA was expressed in the subfornical organ and paraventricular nucleus of the hypothalamus. AT1B as well as AT1A receptor mRNA were found in the cerebral cortex and hippocampus. Conversely, AT2 receptor mRNA, but not AT1A or AT1B, was expressed in the medial geniculate nucleus and inferior olive. Our results indicate that AT1A receptors are involved in the well known central functions of angiotensin II. These results also support the hypothesis of the involvement of AT2 receptors in sensory and motor function.

Angiotensin II↗
PubMed1995

Expression of non-angiotensin II -125I-CGP 42112 binding sites on activated microglia after kainic acid induced neurodegeneration.

[125I]CGP 42112, first developed to identify angiotensin II receptor subtype 2 (AT2), was recently shown to bind to a novel non-angiotensin binding site in injured rat brain tissue. We addressed the question whether non-angiotensin [125I]CGP 42112 binding appears after kainic acid induced hippocampal neurodegeneration, a process of neuronal cell death at a distance from the toxin injection site. After intraventricular kainic acid injection, we found non-angiotensin [125I]CGP 42112 binding in the hippocampal areas CA3 (4 and 14 days after injection), CA1 and CA4 and the subiculum (14 days after injection). In addition, 14 days after kainic acid injection, [125I]CGP 42112 binding was found in 50% of the animals, in the thalamus, amygdala and piriform cortex, areas receiving projections from the hippocampus and suffering kainic acid induced delayed neurodegeneration. The loss of neurons in these regions was accompanied by an accumulation of activated microglia as demonstrated by immunostaining with the specific antibodies OX-42 and ED1. The time course and regional pattern of OX-42/ED1 positive immunostaining was identical with the appearance and distribution of the non-angiotensin [125I]CGP 42112 binding site. The non-angiotensin [125I]CGP 42112 binding was not detected in brain regions unaffected by kainic acid injection. Our findings indicate the expression of a novel [125I]CGP 42112 binding site on activated microglia. This site appears at a distance from the lesion and may be of importance in the process of neuronal death and brain tissue repair.

Angiotensin II↗
PubMed1995

Quantitative autoradiography of angiotensin II AT2 receptors with [125I]CGP 42112.

Most radiolabeled ligands for angiotensin II (Ang II) receptors do not discriminate between the AT1 and AT2 receptor subtypes, which must be distinguished by displacement with selective AT1 or AT2 ligands. We compared [125I]CGP 42112 with the non-selective agonist [125I]Sar1 Angiotensin II. We studied the inferior olive, medial geniculate nucleus and the adrenal medulla, areas rich in AT2 receptors, using both ligands with quantitative autoradiography and membrane binding techniques. [125I]CGP 42112 bound with high affinity (Kd = 0.07-0.3 nM, depending on the area studied). [125I]CGP 42112 binding was selective for AT2 receptors, as determined by lack of competition with the AT1 ligand losartan, and competition by the AT2 ligands PD 123177 and unlabeled CGP 42112 and the non-selective peptides Ang II and angiotensin III (Ang III). Using [125I]CGP 42112 binding, we found the same order of potency: CGP 42112 > Ang II = Ang III > PD 123177 using both quantitative autoradiography or membrane binding methods. Our results demonstrate that [125I]CGP 42112 is the most selective, highest affinity ligand available for AT2 receptors. Because of these characteristics, and low non-specific binding, quantitative autoradiography with [125I]CGP 42112 is the method of choice to selectively characterize AT2 receptors, especially in tissues like the brain, with a highly heterogeneous distribution of receptor subtypes.

Adrenal Medulla↗
PubMed1995

Longitudinal assessment of growth in children born to mothers with human immunodeficiency virus infection.

OBJECTIVES: To describe and to evaluate the longitudinal growth of children born to mothers with human immunodeficiency virus (HIV) infection. DESIGN: Measurements of weight, length (measured in infants in a recumbent position) and height (measured in older children in an upright position), and head circumference were documented and evaluated longitudinally using generalized estimating equations in a group of children born to HIV-infected mothers. Children infected with HIV were compared with uninfected children and with National Center for Health Statistics standards. SETTING: Primary care clinic in an urban hospital devoted to the medical care of children born to HIV-infected mothers. PATIENTS: One hundred nine children born to HIV-infected mothers, 59 HIV-infected and 50 uninfected, between birth and 70 months of age. RESULTS: The mean birth weights of both groups were below the 50th percentile. While the mean weight-for-age curve of uninfected children attained the 50th percentile by age 24 months, the mean birth weight-for-age curve of HIV-infected children remained below the 50th percentile. Weight gain became significantly different between the two groups by age 36 months. The mean birth length-for-age curves of HIV-infected and uninfected children was also below the 50th percentile. The mean height-for-age curve of uninfected children attained the 50th percentile by age 40 months, while that of HIV-infected children remained well below the 50th percentile. Linear growth between HIV-infected and uninfected children diverged earlier than weight, becoming significantly different by age 15 months. CONCLUSIONS: Although children born to HIV-infected mothers are born with weight and length below the 50th percentile, uninfected children catch up, while HIV-infected children remain below the 50th percentile and experience an earlier and more pronounced decrease in linear growth (height-for-age) than in weight-for-age.

Body Height↗