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G Ballejo

Publications and source records attributed to G Ballejo.

At least 37 records · Page 2Linked to original sources
PubMed1995

Rat duodenum nitrergic-induced relaxations are cGMP-independent and apamin-sensitive.

The effects of the K+ channel blockers, apamin, tetraethylammonium and 4-aminopyridine, upon the relaxations of the isolated rat proximal duodenum induced by nitregic nerve activation, nitric oxide (NO), the NO donor 3-morpholinosydnonimine (SIN-1) and Br-cyclic GMP were determined. The effects of the guanylate cyclase inhibitors, cystamine and N-methylhydroxylamine, on NO-, SIN-1- and nitrergic nerve-induced responses were also investigated. Apamin inhibited nitrergic nerve-, NO-and SIN-1-induced relaxations but did not affect those induced by Br-cGMP. Tetraethylammonium and 4-aminopyridine as well as cystamine and N-methylhydroxylamine failed to affect the relaxations caused by any of the agents tested. These findings indicate that, in the rat proximal duodenum, nitrergic nerve activation as well as exogenous nitric oxide cause relaxation through a cGMP-independent, apamin sensitive mechanism.

4-Aminopyridine↗
PubMed1995

Effects of lithium and myoinositol on the rat bisected vas deferens.

1. The effects of lithium (Li+) on the concentration-response curves (CRC) to norepinephrine (NE) and acetylcholine (Ach) on the bisected rat vas deferens (RVD) were investigated, as well as its action on the neuronal uptake of [3H] NE. 2. Li+ did not affect the 50% effective concentration (EC50) of NE and Ach in the epididymal (EP) portion of the RVD. 3. Li+ caused a significant increase of the EC50 to NE and Ach in the prostatic (PP) portion of the RVD. This shift to the right of the CRC to NE was prevented by the presence of myoinositol. 4. Incubation of the PP of the RVD with Li+, increased the neuronal uptake of NE. The simultaneous incubation with myoinositol prevented this increase. 5. After the pre-treatment of the rats with 6-hydroxydopamine (6-OHDA), or in the presence of cocaine, Li+ failed to desensitize the PP of the RVD to NE. 6. These results suggest that the effect of Li+ on the PP of the RVD occurs mainly at the pre-synaptic level and may be related to the increase of neuronal uptake and to the interference of Li+ on phosphatidylinositol hydrolysis.

Acetylcholine↗
PubMed1995

Effect of chronic estradiol administration on the acute pressor response to aortic coarctation in conscious rats.

We investigated the effect of chronic estradiol administration on the pressor response elicited by acute (45 min) partial aortic constriction in conscious Wistar rats and on vascular reactivity to angiotensin II and vasopressin in vitro. Estradiol (10 micrograms kg-1 day-1, sc) or vehicle was administered for 7 days to young castrated male and female rats and to female rats that had stopped cycling (14-16 months of age). In the acute experiment of aortic coarctation in conscious rats, carotid pressure was monitored continuously before and for 45 min after partial abdominal aortic coarctation. In ovariectomized females the mean carotid pressure and heart rate before aortic coarctation were significantly lower in estradiol-treated animals (107 +/- 3 vs 119 +/- 3 mmHg and 360 +/- 31 vs 494 +/- 12 bpm). Estradiol did not affect the pressor response (145-150 mmHg) to aortic coarctation of castrated male rats or ovariectomized female rats but blunted the reflex bradycardia of ovariectomized rats. The onset of the pressor response to aortic coarctation was delayed in aged female rats as compared to the other groups. While estradiol treatment significantly accelerated the onset of hypertension in aged rats, it did not affect the pressor response of castrated animals. Full dose-response curves to angiotensin II and vasopressin were constructed in vitro in the isolated mesenteric arterial bed obtained from similarly treated groups. Estradiol did not affect the vasopressin sensitivity or responsiveness of any group, but caused a significant increase in angiotensin II sensitivity in ovariectomized rats only.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1994

Anxiolytic effect of nitric oxide synthase inhibitors microinjected into the dorsal central grey.

Nitric oxide synthase (NOS) accounts for most of the NADPH-diaphorase neuronal activity in the brain. NADPH-diaphorase-positive neurones have been localized at the dorso-lateral part of the periaqueductal grey (PAG), a region related to anxiety. Microinjections of the NOS inhibitors L-NAME (10-200 nmol 0.5 microliter-1) and L-NOARG (10-100 nmol) at this site induced anxiolytic-like effects in the elevated plus maze. These effects, however, occurred only at a limited range of doses and the dose-effect curve had a bell shape, higher doses of both compounds tending to be anxiogenic. The anxiolytic effect of L-NAME was antagonized by a previous microinjection of L-arginine (50 nmol 0.5 microliter-1). These results suggest that NO may play a role in PAG neurotransmission involved in anxiety.

Amino Acid Oxidoreductases↗
PubMed1994

Blockers of the L-arginine-nitric oxide-cyclic GMP pathway facilitate baroreceptor resetting.

We investigated the role of nitric oxide on rapid (25- and 40-minute) baroreceptor resetting during the onset of acute hypertension in rats treated with NG-nitro-L-arginine, an inhibitor of nitric oxide synthesis, and methylene blue, an inhibitor of guanylate cyclase. The effect of treatment with glibenclamide, an ATP-dependent K+ channel blocker, was also investigated. Arterial hypertension was provoked in a ramp progression by the drug NG-nitro-L-arginine alone or in association with aortic coarctation. Whole aortic nerve activity and carotid pressure were recorded in the anesthetized rats. The extent of rapid resetting was evaluated by means of the ratio (delta Systolic Threshold Pressure/delta Control Diastolic Pressure) x 100 as well as by the extent of displacement of the pressure-nerve activity curve defined by the ratio (delta Mean Arterial Pressure at 50% of maximum activity/delta Mean Arterial Pressure) x 100. All groups gave the same increase in mean arterial pressure at 25 and 40 minutes after the onset of hypertension. A greater extent of resetting to hypertensive levels was observed in the treated groups compared with coarctation alone. At 40 minutes after the onset of hypertension, the coarctation and nitro-L-arginine groups exhibited a further increase in the extent of resetting. The rats submitted to glibenclamide plus coarctation presented a slight but significant decrease in gain. These findings suggest that an active L-arginine-nitric oxide-cyclic GMP pathway blunts rapid resetting during the onset of hypertension. In addition, they also indicate that ATP-dependent K+ channels can also modulate rapid resetting of the baroreceptors to hypertensive levels.

Analysis of Variance↗
PubMed1993

Alpha 1-adrenoceptor subtypes mediating the norepinephrine-induced contractile response in the rat vas deferens.

1. The effects of chlorethylclonidine (CEC), 5-methyl-urapidil (5-MU), ryanodine and prolonged exposition to norepinephrine (NE) on the concentration-response curves (CRC) to this agonist on the bisected rat vas deferens (RVD) were investigated. 2. CEC did not affect the 50% effective concentration (EC50) of NE in either the prostatic (PP) or the epididymal (EP) portions of the RVD. 3. 5-MU did not alter the EC50 of NE in the PP but caused a significant and concentration-dependent rightward shift of the CRC to NE in the EP. 4. Ryanodine caused a shift to the right of the CRC to NE in the PP associated to a decrease in maximal response, but did not affect the CRC to NE in the EP. 5. Incubation of the EP with NE for 6 hr elicited a significant decrease in the maximal response with no changes in the EC50. Similar treatment of the PP was associated with a significant shift to the right of the CRC to NE without modifications in the maximal response. 6. These results suggest that in the RVD, NE interacts with two different alpha 1-adrenoceptors subtypes which are disposed in a selective manner along the RVD: the alpha 1(a) subtype in the EP, and non-alpha 1b-non-alpha 1a adrenoceptor subtype mainly located at the PP.

Adrenergic alpha-1 Receptor Antagonists↗
PubMed1993

Evidence for the participation of the L-arginine-nitric oxide pathway in neurally induced relaxation of the isolated rat duodenum.

1. Electrical field stimulation (EFS) of intrinsic nerves in the rat proximal duodenum induces a frequency-dependent non-adrenergic-non-cholinergic (NANC) relaxation response. 2. The inhibitors of L-arginine-NO synthase L-NG-nitro arginine methyl-ester (L-NAME) and L-NOARG (L-NG-nitro arginine) reduced the NANC relaxations elicited by EFS in a dose- and time-dependent manner; L-NOARG was two times more potent than L-NAME (IC50 = 14.3 vs 25.2 microM) and these effects were partially reverted by the addition of 300-1000 microM L-arginine but not of 300-1000 microMD-arginine. Relaxation caused by vasoactive intestinal peptide (VIP; 0.1 microM) or ATP (20 microM) was not blocked by L-NAME or L-NOARG. 3. The magnitude of the blockade caused by L-NAME and L-NOARG was dependent on the frequency of stimulation. At low frequencies (below 1 Hz) both L-NAME and L-NOARG abolished the relaxations, while at 2 to 8 Hz only partial inhibition was observed (maximal inhibition: 44.6% +/- 5.2 and 63.4% +/- 3.4, respectively) 4. The basal tonus of the duodenum was increased by 10-300 microM L-NAME and 10-300 microM L-NOARG and this effect was blocked by 1 mM L-arginine. 5. Nitric oxide generated from acidified NaNO2 caused a dose-dependent (EC50 = 2.75 microM) relaxation of the duodenum which was not affected by 100 microM L-NAME, 100 microM L-NOARG or 1 microM tetrodotoxin (TTX). 6. NADPH-diaphorase positive neurons and fibers identified by histochemistry were present in the myenteric plexus and along both circular and longitudinal muscle fibers indicating that nitric oxide could be synthetized by these neural structures.

Animals↗
PubMed1992

Differential effects of estrogen and antiestrogen on transforming growth factor gene expression in endometrial adenocarcinoma cells.

While antiestrogens are useful agents in the treatment of breast cancer, the usefulness of these agents in the treatment of endometrial cancer remains controversial. There is some concern that the currently available antiestrogens may have partial agonist activity in uterine tissue. To better understand the mechanisms by which estrogens and antiestrogens modulate growth of endometrial adenocarcinoma cells, we have compared the effects of 17-beta estradiol and three antiestrogens, 4-hydroxytamoxifen (OH-TAM), ICI 164384, and LY 117018 on proliferation and transforming growth factor (TGF) mRNA accumulation in two human endometrial adenocarcinoma cell lines. In HEC-50 cells, neither estradiol nor anti-estrogens had any effect on cell proliferation or TGF mRNA abundance under estrogen-depleted culture conditions [basal medium containing 1% twice charcoal-treated fetal bovine serum (ctFBS)] or in the presence of estrogen (basal medium containing 5% fetal bovine serum). At very high concentrations, both estradiol and OH-TAM caused a small decrease in HEC-50 cell proliferation in medium containing 5% serum. In contrast, the antiestrogens had different effects on Ishikawa cells, depending upon the culture conditions. In medium containing 5% fetal bovine serum, the antiestrogens inhibited cell proliferation and significantly decreased TGF-alpha mRNA abundance and TGF-alpha secretion. OH-TAM was more potent than the other antiestrogens. Under these culture conditions, estradiol had no effect on cell proliferation or TGF-alpha mRNA levels but increased TGF-alpha secretion. In medium supplemented with 1% ctFBS, estradiol increased cell proliferation and TGF-alpha mRNA (2.72-fold, P less than 0.005) and TGF-alpha secretion (700 +/- 156 versus 250 +/- 23 pg/10(6) cells/24 h, P less than 0.05), whereas OH-TAM, which also stimulated cell proliferation, reduced TGF-alpha mRNA abundance (P less than 0.05) but had no significant effect on TGF-alpha secretion. Under these conditions, ICI 164384 and LY 117018 had no effect on either cell proliferation or TGF-alpha expression. Estradiol treatment decreased, whereas OH-TAM increased, epidermal growth factor receptors in Ishikawa cells. Both estradiol and the antiestrogens decreased TGF-beta 1 mRNA abundance when cells were grown in media containing 1% ctFBS. In summary, the response of human endometrial adenocarcinoma cells to estrogen and antiestrogens varied between cell lines and was dependent upon the culture conditions used. In addition, OH-TAM, unlike the other two antiestrogens tested, had growth-stimulating effects on Ishikawa cells.

Adenocarcinoma↗
PubMed1992

Mechanism of pain induced by radiocontrast media.

In lightly-anesthetized dogs, ionic or non-ionic RCM (Iotalamato and iohexol, respectively) when injected by intracarotid route (i.c.), elicit a pain response comparable to that caused by bradykinin (BK) or capsaicin (CAP). This response, which is characterized by vocalization, hyperpnea, bradycardia and neck muscle contraction, was dose dependent and related to the osmolarity of the RCM. In the present study we observed that indomethacin did not interfere with CAP and RCM-induced pain at dose (2 mg/kg i.c.) that reduced BK-elicited responses. In contrast, Ruthenium Red (RR), in dose (1 mg/kg i.c.) that reduced CAP and/or RCM-induced effects did not affect BK-induced phenomena. We also verified that L-NAME (50 mg/kg i.c.) reduced the BK-, but not the CAP- and/or RCM-induced pain responses which suggests that an L-arginine-derived NO or related compound is involved in BK activation of perivascular nociceptors. Indeed, we found that i.c. injection of 20 mg of S-nitrosocysteine, a putative EDRF, caused BK-like responses. On the other hand, RCM and CAP appear to activate the same RR sensitive ionic channels of primary afferent endings. Therefore, RR-analogues could constitute a novel approach to minimizing or eventually abolishing the RCM side effects.

Animals↗
PubMed1992

Phorbol esters differentially regulate the expression of insulin-like growth factor-binding proteins in endometrial carcinoma cells.

We have examined the effects of protein kinase-C (PKC) activation on expression of the six known insulin-like growth factor-binding proteins (IGFBPs) by human endometrial carcinoma cells. Each of six known IGFBPs was expressed in one or more of the three cell lines examined. The addition of 10(-7) M 4 beta-phorbol 12-myristate 13-acetate (PMA) to HEC-50 and HEC-1B cells resulted in changes in cell morphology, growth inhibition, activation of PKC, and an increase in expression of IGFBP-1. PMA had no effect on these parameters in the Ishikawa cell line, which did not express IGFBP-1. In HEC-50 cells, the effect of PMA was blocked by the concomitant addition of the PKC inhibitor staurosporin and the simultaneous addition of cycloheximide. PMA also resulted in an increase in IGFBP-3 in HEC-50 cells and an increase in IGFBP-6 expression in HEC-1B cells. In contrast, IGFBP-3 expression was down-regulated by PMA in HEC-1B and Ishikawa cells. The abundance of IGFBP-2 and IGFBP-5 mRNAs was also reduced in HEC-1B and Ishikawa cells, respectively. IGFBP-4 was expressed only in HEC-50 cells and was not affected by PMA treatment. These data establish a role for the PKC pathway in regulation of expression of IGFBP-1, -2, -3, and -5 in endometrial adenocarcinoma cells and illustrate the complexity of cell type-specific expression of the IGFBPs.

Adenocarcinoma↗
PubMed1992

Evidence for the involvement of nitric oxide in the electrically induced relaxations of human lower esophageal sphincter and distal pylorus.

The aim of the present study was to investigate in vitro the effect of NG-nitro-L-arginine methyl ester (L-NAME), a nitric oxide (NO) synthase inhibitor, on neurogenic relaxation of human lower esophageal sphincter (LES) and distal pylorus (DP) circular muscle strips induced by electrical field stimulation (EFS). Muscle strips obtained from 5 patients who underwent total gastrectomy were suspended in 10-ml organ baths containing Krebs solution for recording isometric tension. L-NAME (30 microM) reduced the amplitude of the EFS-induced relaxation by 85 +/- 9% (N = 3) in the LES and by 52 +/- 16% (N = 3) in the DP but did not affect sodium nitroprusside-induced relaxation. L-Arginine (300 microM) partially reversed the L-NAME inhibition in the LES and totally in the DP. These findings suggest a role for L-arginine-derived NO in the nerve-mediated NANC relaxation of the human LES and DP.

Adult↗
PubMed1992

Is guanylate cyclase activation through the release of nitric oxide or a related compound involved in bradykinin-induced perivascular primary afferent excitation?

In dogs under light thiopentobarbital anesthesia, intracarotid injection of bradykinin (BK) causes a dose-dependent "pain response" represented by hyperpnea, bradycardia, vocalization and ipsilateral contraction of the sternocephalic muscle. These events result from the activation of primary afferent nerves located in the wall of the carotid vessels distributed mainly in occipital artery territory. We present evidence indicating that these BK-induced reflex phenomena are 1) mediated by the activation of B2 receptors; 2) potentiated by prostaglandin E2 (PGE2) and serotonin (5-HT) the latter acting via sub-type 5-HT3 receptors; 3) reduced by indomethacin and/or NG-nitroarginine, and 4) abolished by methylene blue. These results suggest that 5-HT plays a modulatory role on BK action; the latter depends on the release of prostaglandins and nitric oxide or a related compound and includes the activation of guanylate cyclase which appears to be involved in primary afferent excitation.

Animals↗
PubMed1991

Transforming growth factor gene expression in human endometrial adenocarcinoma cells: regulation by progestins.

In an attempt to understand the antiproliferative effects of progestins in endometrial cancer, we have examined the effects of the potent progestin, medroxyprogesterone acetate (MPA), on the cell proliferation and the expression of transforming growth factor (TGF) alpha and beta genes in human endometrial adenocarcinoma cell lines. The two cell lines used were Ishikawa, var 1, and HEC-50. In addition, the effects of exogenous TGF-alpha and anti-epidermal growth factor (EGF) receptor monoclonal antibody on cell proliferation were determined. Incubation of both cell lines with MPA resulted in a time- and dose-dependent inhibition of cell proliferation. Half-maximal growth inhibition was observed at 0.6 nM. In Ishikawa cells, the relative abundance of TGF-alpha was significantly reduced by MPA. A significant decrease in TGF-alpha mRNA was apparent 6 h after exposure to MPA and a further decrease was seen 12-24 h after addition of the progestin. The concentration of TGF-alpha immunoreactivity in conditioned medium of MPA-treated cells was also significantly reduced compared to control cultures. MPA had no effect on TGF-alpha expression by HEC-50 cells. EGF mRNA was not detected by Northern blot analysis in either cell type. MPA had no significant effect on EGF receptor mRNA abundance but resulted in a small increase in EGF receptor number in Ishikawa cells. Anti-EGF receptor monoclonal antibody (0.6-6 nM) inhibited Ishikawa cell growth but had no effect on HEC-50 cell proliferation. Exogenous TGF-alpha stimulated proliferation of both cell lines, but Ishikawa cells were significantly more sensitive to exogenous TGF-alpha than HEC-50 cells. Furthermore, TGF-alpha could reverse the growth inhibitory effects of MPA on Ishikawa cells. A decrease in TGF-beta mRNA abundance was also observed in MPA-treated Ishikawa and HEC-50 cells. This effect was of small magnitude, variable, and only observed after prolonged exposure to MPA. These observations are consistent with the hypothesis that the antiproliferative effects of progestins on Ishikawa cells are mediated by decreased expression and autocrine action of TGF-alpha. Since similar growth inhibition is also seen in the HEC-50 cells in which progestins have no effect on TGF-alpha expression, additional mechanisms are likely to be involved in the antiproliferative effects of progestins in human endometrial cancer.

Antineoplastic Agents↗
PubMed1990

Identification and characterization of a rat decidual insulin-like growth factor-binding protein complementary DNA.

A partial cDNA which encodes the rat homolog of human placental protein-12, the low mol wt insulin-like growth factor-binding protein (IGFBP-1), has been isolated from a rat decidual cDNA library using low stringency hybridization with a human IGFBP-1 cDNA probe. The incomplete cDNA obtained from this library was used to screen a rat liver cDNA library from which a full-length cDNA was obtained. The predicted amino acid sequence of rat IGFBP-1 showed 66%, 29%, and 34% sequence identity with the human IGFBP-1, the human GH-dependent binding protein IGFBP-3, and rat IGFBP-2, the BP secreted by buffalo rat liver cells, respectively. The rat IGFBP-1 cDNA hybridized with a 1.6-kilobase transcript which was easily detected in uterine RNA from the pseudopregnant rat and RNA from the liver and kidney of adult rats. A low level of expression was apparent in the brain and the diestrous uterus. Of the tissues examined the order of abundance of IGFBP-1 mRNA was deciduoma tissue greater than or equal to liver much greater than kidney much greater than uterus greater than brain. The 1.6-kb mRNA was more abundant in RNA from neonatal rat liver than in that from maternal liver, but was not detected in total RNA (50 micrograms) from other neonatal rat tissues (kidney, lung, brain, and heart). Under stringent conditions, rat IGFBP-1 did not hybridize with RNA from the BRL-3A rat liver cell line. In food-deprived rats, hepatic IGFBP-1 mRNA was increased 10.0 +/- 2.2-fold compared to that in control rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1989

Selective inhibition of protein disulfide isomerase by estrogens.

Protein disulfide isomerase (PDI) is a multifunctional microsomal enzyme that participates in the formation of protein disulfide bonds. PDI catalyzes the reduction of protein disulfide bonds in the presence of excess reduced glutathione and has been implicated in the reductive degradation of insulin; E. coli thioredoxin is homologous to two regions in PDI and can also degrade insulin. PDI activity, measured by 125I-insulin degradation or reactivation of randomly oxidized RNase in the presence of reduced glutathione, is non-competitively inhibited by estrogens; half-maximal inhibition was observed at approximately 100 nM estrogen. Other steroid hormones at 1 microM had little or no effect. PDI segment 120-163 (which corresponds to exon 3 of the PDI gene) and 182-230 have significant similarity with estrogen receptor segments 350-392 and 304-349, respectively, located in the estrogen binding domain but not with the steroid domains of the progesterone and glucocorticoid receptors or with thioredoxin, which is insensitive to estrogens. We propose the hypothesis that enzymes can acquire sensitivity to a hormone via exon shuffling to the enzyme gene from the DNA region coding for the hormone binding domain of the hormone's receptor.

Amino Acid Sequence↗
PubMed1989

Decreased gamma-aminobutyric acid (GABA) modulatory effect on rat vas deferens neurotransmission after chronic administration of imipramine.

1. Chronic (10 mg/kg, i.p., once daily for 14 days) but not acute (10 mg/kg, i.p., 24 hr) administration of imipramine resulted in a decrease in both the responsiveness and the sensitivity of the contractions of the isolated rat vas deferens elicited by field stimulation to GABA and (-)-baclofen. 2. In contrast, clonidine and isoproterenol effects were not altered by either treatment. 3. This study shows for the first time that GABA action in the peripheral nervous system is altered by chronic treatment with antidepressants, possibly by inducing changes in a postreceptor element.

Animals↗
PubMed1988

Inhibitory effect of GnRH on isolated rat uterine muscle contractility.

The effect of GnRH upon uterine contractions of both non-pregnant and pregnant rats was examined in vitro. In the non-pregnant rat uterus, GnRH inhibited in a concentration-and-time dependent manner the contractions induced by acetylcholine and oxytocin, but not those caused by bradykinin and angiotensin II. GnRH also inhibited the rhythmic contractions induced by oxytocin in uterine strips from late pregnant rats. These findings show that GnRH has a direct inhibitory effect on the rat uterine contractions, suggesting that GnRH-like substances may exert modulatory influences upon rat uterine contractility.

Acetylcholine↗