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R Garcia

Publications and source records attributed to R Garcia.

At least 433 records · Page 24Linked to original sources
PubMed1984

Structure-activity relationships of atrial natriuretic factor (ANF). I. Natriuretic activity and relaxation of intestinal smooth muscle.

Atrial natriuretic factor-related peptides were produced from synthetic ANF (101-126) either by chemical hydrolysis at the N-terminal end or by treatment with carboxypeptidases at the C-terminal end. The biological activities of these peptides were characterized in vivo by a natriuretic bioassay and in vitro by relaxation of contracted intestinal smooth muscle (chick rectum). In the natriuretic assay, the removal of Asn122, Ser123 and Phe124 at the C-terminal end alters considerably the renal response. Deletion or extension of amino acids at the N-terminal end affects only slightly the natriuretic activity. Removal of N-terminal or C-terminal amino acids decreases the relaxant activity of ANF on the chick rectum. In both bioassays, simultaneous deletions of residues at both ends drastically affect the activity in an additive manner.

Amino Acid Sequence↗
PubMed1984

Effect of native and synthetic atrial natriuretic factor on cyclic GMP.

Mammalian atrial cardiocyte granules contain a potent natriuretic and diuretic peptide. Since cGMP appears to be involved in the modulation of cholinergic and toxin-induced sodium transport, we examined the effect of atrial natriuretic factor (ANF) on this nucleotide. Atrial but not ventricular extracts elicited approximately a 28-fold increase of urinary cGMP excretion parallel to the natriuresis and diuresis. The atrial extracts also elevated cGMP levels in kidney slices and primary cultures of renal tubular cells. The effect of ANF on cGMP appeared to be specific since antibodies which were capable of inhibiting the ANF-induced diuresis also suppressed cGMP excretion. Furthermore, during the course of ANF purification, the ANF-induced increase of cGMP production by kidney cells paralleled the heightened specific natriuretic activity of the atrial factor. A synthetic peptide (8-33)-ANF similarly increased urinary plasma and kidney tubular cGMP levels. The exact mechanism of action of ANF on cGMP remains to be elucidated, but indirect inhibition of cGMP phosphodiesterase appears to participate in its effect.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1984

Atrial pronatriodilatin: a precursor for natriuretic factor and cardiodilatin. Amino acid sequence evidence.

Numerous peptides isolated from rat heart atria, including two containing 33 and 73 amino acids, were isolated and shown to exhibit natriuretic activities. Here, we describe the purification and partial amino acid sequence of a 106-residue peptide containing the previously sequenced 33- and 73-amino-acid ANF peptides. The determined sequence is a novel one and is not significantly homologous to any known protein or segment thereof. In fact, this sequence shows significant homology only to another novel partial sequence obtained from sequence analysis of a porcine peptide, called cardiodilatin, also found in heart atria. This relationship is taken as evidence that ANF and cardiodilatin are part of the same precursor molecule which would contain at the very least 126 amino acids.

Amino Acid Sequence↗
PubMed1984

Comparative vasoactive effects of native and synthetic atrial natriuretic factor (ANF).

The presence of a natriuretic factor in mammals atria has been confirmed by many laboratories. In addition to its natriuretic and diuretic activities, atrial preparation of uncertain degree of purification are known to contain a vasoactive substance. By the use of pure atrial natriuretic factor of known amino acid sequence and its synthetic homologue we have presented strong evidences suggesting that natriuretic and vasoactive activities are indeed mediated by the same peptide. As this peptide has not yet been detected in the circulation, its actual physiological relevance remains to be elucidated.

Animals↗
PubMed1984

Primary structure of a high Mr form of rat atrial natriuretic factor.

During the purification of rat atrial natriuretic factor (ANF), low, intermediate and high Mr forms were observed. In this report we describe the purification and amino acid sequence of a 73 residue peptide containing at its C-terminus the previously sequenced 33 amino acid ANF peptide. The cleavage necessary to produce the 33 amino acid ANF from the 73 amino acid precursor occurs at a Leu-Leu bond. We also report the amino acid composition of an even longer form of ANF containing about 103 residues, in which the extension is amino terminal to the 73 peptide. A computer data bank search showed that the determined sequence is a novel one and is not homologous to any known proteins or segment thereof. The natriuretic activity of the 73 amino acid form when compared to that of a synthetic ANF peptide, comprising the sequence of the last 26 amino acids of ANF, was found to be slightly lower.

Amino Acid Sequence↗
PubMed1984

Immunocytochemical localization of atrial natriuretic factor in the heart and salivary glands.

Antibodies produced in the mouse by repeated intraperitoneal injections of partly purified atrial natriuretic factor (low molecular weight peptide (LMWP) and high molecular weight peptide (HMWP)) have been used to localize these factors by immunohistochemistry (immunofluorescence and immunoperoxidase method) and by immunocytochemistry (protein A-gold technique) in the heart of rats and of a variety of animal species including man and in the rat salivary glands. Immunofluorescence and the immunoperoxidase method gave identical results; in the rat, atrial cardiocytes gave a positive reaction at both nuclear poles while ventricular cardiocytes were consistently negative. The cardiocytes of the right atrial appendage were more intensely reactive than those localized in the left appendage. A decreasing gradient of intensity was observed from the subpericardial to the subendocardial cardiocytes. The cardiocytes of the interatrial septum were only lightly granulated. Sodium deficiency and thirst (deprivation of drinking water for 5 days) produced, as already shown at the ultrastructural level, a marked increase in the reactivity of all cardiocytes from both atria with the same gradient of intensity as in control animals. Cross-reactivity of intragranular peptides with the rat antibodies allowed visualization of specific granules in a variety of animal species (mouse, guinea pig, rabbit, rat, dog) and in human atrial appendages. No reaction could be elicited in the frog atrium and ventricle although, in this species, specific granules have been shown to be present by electron microscopy in all cardiac chambers. With the protein A-gold technique, at the ultrastructural level, single labeling (use of one antibody on one face of a fine section) or double labeling (use of two antibodies on the two faces of a fine section) showed that the two peptides are localized simultaneously in all three types (A, B and D) of specific granules. In the rat salivary glands, immunofluorescence and the immunoperoxidase method showed reactivity exclusively in the acinar cells. The reaction was most intense in the acinar cells of the parotid gland. In the sublingual gland, only the serous cells, sometimes forming abortive "demi-lunes", were reactive. In the submaxillary gland, the reaction was weaker and distributed seemingly haphazardly in the gland. The most constantly reactive cells were localized near the capsule while many cells did not contain visible reaction product.

Adult↗
PubMed1984

Similar growth pattern of mouse mammary epithelium cultivated in collagen matrix in vivo and in vitro.

Mouse mammary ductal cells cultured in type I collagen gels give rise to three-dimensional multicellular outgrowths consisting of thin spikes which are often branched, and which may have pointed or blunt ends. The significance of these spikes to normal ductal morphogenesis has been unclear, since identical structures are not known to occur in vivo; conversely, it has not been possible to maintain in gel culture the highly structured end buds which are characteristic of ductal elongation in the animal. In order to evaluate whether the pattern of radiating spikes observed in collagen gel cultures results from chemical or physical peculiarities of the culture environment, a small volume of unpolymerized type I collagen solution was injected into mammary gland-free fat pads of young adult mice. After the bubble of collagen had polymerized, an implant of mammary ductal epithelium was introduced into the center of the gel. Histological examination of the implants after 3 to 6 days of growth revealed numerous small epithelial spikes, similar to those observed in gel culture, extending into the fibrous matrix. The early stages of regeneration of mammary implants placed in gland-free fat pads were then examined without the addition of exogenous collagen. In cases where the epithelium happened to contact a fibrous region of the fatty stroma, spikes were also seen to form in these natural collagenous substrates. Whether or not exogenous collagen was used, normal end buds were formed only when epithelial spikes contacted adipocytes. It was concluded that the three-dimensional pattern of radiating tubules in collagen gels in vitro is not merely an artifact of culture, but has a counterpart in vivo whereever regenerating mammary epithelium is surrounded by fibrous stroma. A model is presented in which the pattern of epithelial outgrowth is determined by the physical characteristics of the surrounding stroma; in collagen matrix a comparatively primitive and unspecialized type of morphogenesis occurs which may not require the participation of stromal cells. In contrast, epithelial-adipocyte interactions appear to be necessary for the formation of end buds and subsequent morphogenesis of fully structured mammary ducts.

Animals↗
PubMed1984

Amino acid sequence of homologous rat atrial peptides: natriuretic activity of native and synthetic forms.

A substance called atrial natriuretic factor (ANF), localized in secretory granules of atrial cardiocytes, was isolated as four homologous natriuretic peptides from homogenates of rat atria. The complete sequence of the longest form showed that it is composed of 33 amino acids. The three other shorter forms (2-33, 3-33, and 8-33) represent amino-terminally truncated versions of the 33 amino acid parent molecule as shown by analysis of sequence, amino acid composition, or both. The proposed primary structure agrees entirely with the amino acid composition and reveals no significant sequence homology with any known protein or segment of protein. The short form ANF-(8-33) was synthesized by a multi-fragment condensation approach and the synthetic product was shown to exhibit specific activity comparable to that of the natural ANF-(3-33).

Amino Acid Sequence↗
PubMed1984

Three sea urchin actin genes show different patterns of expression: muscle specific, embryo specific, and constitutive.

The expression of three different actin genes in the sea urchin, Strongylocentrotus purpuratus, was monitored in embryos and adult tissues by using untranslated mRNA sequences as specific hybridization probes. Three distinct patterns of expression were found: muscle specific, embryo specific, and constitutive (i.e., present in all tissues examined). The actin genes encoding the muscle-specific and constitutively expressed genes were each found to be present once in the haploid genome. The embryo-specific probe could derive from either a single gene or a small subset of actin genes. These data demonstrate that at least three members of the sea urchin actin gene family are expressed in distinct ways and thus are probably associated with different regulatory programs of gene expression necessary for development of this metazoan.

Actins↗
PubMed1984

Release of prostaglandins by the mesenteric artery of the renovascular and spontaneously hypertensive rat.

The release of prostaglandin E2 (PGE2) and 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha), the stable metabolite of prostacyclin (PGI2), by the perfused mesenteric arteries of renal and spontaneously hypertensive rats (SHR) have been measured. Unstimulated mesenteric arteries from two-kidney one-clip hypertensive rats (2K-1C) released 1.6 times as much PGE2 and 2.7 times as much 6-keto-PGF1 alpha as those of control rats. The release of PGE2 by mesenteric arteries from one-kidney one-clip hypertensive rats (1K-1C) was not significantly different from that of uninephrectomized normotensive rats, but the release of 6-keto-PGF1 alpha was 3.5 times higher in the former than in the latter. Norepinephrine (NE) induced a dose-related increase in perfusion pressure, in PGE2, and 6-keto-PGF1 alpha release in all four groups. However, its effect on the release of PGE2 was more pronounced in 2K-1C than in sham-operated rats. There was no difference between 1K-1C and the uninephrectomized group. The effect of NE on the release of 6-keto-PGF1 alpha was significantly higher for both renal hypertensive groups. These results indicate that the release of PGE2 is more dependent on the loss of renal mass than on hypertension, while the reverse applies to the release of 6-keto-PGF1 alpha. Unstimulated mesenteric arteries from SHR released less PGE2 and less 6-keto-PGF1 alpha than those of Wistar-Kyoto normotensive rats (WKY), but the release was not significantly different from Wistar rats. Under NE stimulation, WKY mesenteric arteries showed almost no increase in release of PGs. Compared with those of Wistar rats, SHR mesenteric arteries showed a greater pressor response to NE, a lower PGE2 release, and the same release of 6-keto-PGF1 alpha. These findings reveal the difficulty of selecting an appropriate control group in studies involving SHR.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗
PubMed1984

Atrial natriuretic factor and urinary kallikrein in the rat: antagonistic factors?

The rat atrium contains a potent natriuretic factor which appears to inhibit the sodium reabsorption in the collecting tubules of the kidneys. We examined the effects of the injection of partially purified atrial natriuretic factor (ANF) and synthetic ANF (8-33) into rats with simultaneous infusions of dextrose or aprotinin. Aprotinin, an inhibitor of serine proteases, increases the natriuretic and diuretic effects of the atrial factor by 50%. Urinary kallikrein excretion is also slightly increased by ANF but is not affected by aprotinin. As a comparison, aprotinin has no effect on the diuretic or natriuretic responses of furosemide, although it inhibits by 50% the kallikrein excretion induced by furosemide. When ANF is incubated with purified rat urinary kallikrein, the natriuretic and diuretic effects are decreased by more than 50%. We conclude that glandular kallikrein or a similar serine protease may be involved in the catabolism of ANF.

Animals↗
PubMed1984

Lymphatic, renal, and urinary kallikreins in the rat.

In pentobarbital-anesthetized rats the lymphatic vessels next to the renal artery and the urinary bladder were cannulated and lymph and urine were collected for 3 h. The kidneys were then washed and removed. Four experimental groups were studied. Kallikrein was measured in lymph, urine, and kidney extracts by a direct radioimmunoassay. Immunoreactive renal and urinary kallikreins were higher in a Na-deficient group. No changes were brought about by furosemide administration or Na supplementation. A very low concentration of immunoreactive kallikrein was found in lymph, with no differences between the groups. In the same urine and kidney extract samples, both total (trypsin-activated) kallikrein and naturally active kallikrein were determined as kininogenase activity in the rat uterus bioassay. Both active and inactive kallikreins were found in kidney and urine, but most of the changes induced by a Na-deficient diet or furosemide administration were restricted to the active form. It is suggested that the lymphatic route in the kidney is probably not an important source of circulating immunoreactive glandular kallikrein.

Animals↗
PubMed1984

Effect of a purified atrial natriuretic factor on rat and rabbit vascular strips and vascular beds.

Rat atrium cardiocytes contain a powerful natriuretic and diuretic peptide that has been localized in the specific granules. This atrial natriuretic factor (ANF) produced a potent, dose-dependent relaxant effect on rabbit and rat arterial strips previously made to contract by application of either norepinephrine (NE) or angiotensin II. The effect was not seen if KCl was used as contractile agent or under any conditions with rabbit mesenteric strips. After the application of ANF the vascular strips were refractory to subsequent stimulation by either NE or angiotensin II. The infusion of ANF into a high-resistance isolated perfused rat kidney produced a rapid decrease (33 +/- 5 mmHg) in perfusion pressure that lasted for 18 +/- 3 min. This effect was not seen in the isolated rat mesenteric arterial preparation, even when the perfusion pressure was raised by the infusion of NE. These effects of ANF on vascular smooth muscle are not mediated by prostaglandins, by alpha- and beta-adrenergic and muscarinic receptors, or by an impairment of Ca2+ influx, but they are mimicked by sodium nitroprusside. A low- and a high-molecular-weight ANF produced the same effects. The existence of specific receptive sites for these peptides is suggested.

Angiotensin II↗
PubMed1984

Transmethylation reactions in human basophils induced by anti-IgE or specific antigen.

The activation of methyl transferases in the membrane of human basophilic leukocytes was measured by incorporation of 3H-methyl groups into phospholipids. Basophils of healthy individuals were activated by anti-IgE, those of pollen allergic patients by the specific antigen, Lolium perenne extract. Basophil-rich fraction was obtained from peripheral blood by centrifugation in a gradient of Ficoll/metrizamide (g = 1.085). After incubation with anti-IgE an increase in the 3H-methyl incorporation was detected during the first 30 s of the reaction. The maximal incorporation in basophils of the pollen allergic patients, activated by L. perenne extract, was enhanced at 15 s. Appropriate controls showed that the activation of methyl transferases occurred in basophils only.

Animals↗
PubMed1984

Atrial natriuretic factor inhibits the stimulation of aldosterone secretion by angiotensin II, ACTH and potassium in vitro and angiotensin II-induced steroidogenesis in vivo.

Since atrial natriuretic factor (ANF) blocks the contractile effect of angiotensin II on vascular strips, we investigated the action of the synthetic 48-73 ANF (previously called 8-33 ANF) on another target tissue of angiotensin II, the adrenal glomerulosa. ANF did not affect basal aldosterone output by isolated rat adrenal glomerulosa cells. ANF inhibited aldosterone secretion stimulated by 10(-8)M angiotensin II with an IC50 of 1.3 X 10(-9)M. Aldosterone secretion stimulated by 2.9 X 10(-10)M ACTH and by 15 mM potassium was similarly inhibited by ANF. In vivo, ANF blocked the effect of angiotensin II infused iv on aldosterone secretion in conscious unrestrained rats. We conclude that ANF is a non-selective inhibitor of stimulated aldosterone output.

Adrenal Glands↗
PubMed1984

The heart as an endocrine gland.

The evidence presented here indicates that atrial cardiocytes, apart from their contractile function, are bona fide endocrine cells which synthesize a peptide of known composition (152AA) through identified pathways [6,7]. Part of the peptide is released into the circulation where it can be measured by radio-immunoassay. A synthetic fragment (8-33AA) of the peptide is endowed with potent and variegated effects on several target tissues: massive diuresis and natriuresis of rapid onset and short duration, inhibition of the secretion of aldosterone from beef and rat zona glomerulosa and, to a lesser extent, of cortisol from beef zona fasciculata, vasodilatation and inhibition of the arterial contraction induced by catecholamines or angiotensin II. This peptide is a potent antihypertensive agent. The presence of receptors in the anterior and posterior pituitary, as well as the significant decrease of adenylate cyclase activity observed in both portions of the gland, indicate that the hormone may act at these levels as well. Thus, the heart is raised from the status of a pump to that of a putative endocrine integrator of cardiovascular homeostasis.

Adenylyl Cyclase Inhibitors↗
PubMed1984

Leave-takings and reunions of infants, toddlers, preschoolers, and their parents.

The leave-taking and reunion behaviors of infants, toddlers, preschoolers, and their parents were observed as the children were "dropped off" and "picked up" at their nursery school each day. On arrival at their classroom, infants and toddlers related primarily to their parents, whereas preschoolers related to their teachers. Girls more frequently engaged in interaction with their teachers, and boys more frequently approached the children's play activities. Distress behaviors during the parents' departures were most frequently shown by toddlers, and the toddlers' parents hovered about them and " sneaked out of the room" more frequently. Children dropped off by mothers versus fathers showed more attention-getting behavior and crying, and mothers versus fathers engaged in more "distracting-the-child" behaviors and showed a longer latency to leave the classroom. During the second semester of observations parents and children spent less time relating to each other during leave-taking, children protested the departures less frequently, and the parents left the classroom more quickly. Regression analyses on distress behaviors during leave- takings and ambivalent behavior during reunions suggested that parent behaviors such as verbal explanation, distracting the child, latency to leave, and " sneaking out of the room" were correlated with children's distress and leave-taking distress was related to ambivalent behavior at reunion.

Attitude↗