Biomedical subjects

M A Cruz

Publications and source records attributed to M A Cruz.

At least 55 records · Page 3Linked to original sources

PubMed1993

The interaction of the von Willebrand factor-A1 domain with platelet glycoprotein Ib/IX. The role of glycosylation and disulfide bonding in a monomeric recombinant A1 domain protein.

The interaction of von Willebrand factor (vWF) with platelet glycoprotein Ib/IX plays an important role in primary hemostasis. Previous studies have localized the GpIb alpha binding domain of vWF to amino acid residues 449-728, a region containing the vWF-A1 domain. In order to assess the role of A1 domain structure in vWF binding functions, a cDNA encoding residues 475-709 of vWF was expressed in Escherichia coli (non-glycosylated) and in Chinese hamster ovary (CHO) cells (glycosylated). These recombinant proteins contain a single intrachain disulfide bond between C509 and C695 and were purified as monomers with apparent molecular weights of 36,000 (E. coli) and 39,000 (CHO). 35S-Labeled-vWF-A1 proteins bound directly to GpIb/IX receptors on platelets. The non-glycosylated form had a slightly higher affinity (Kd = 1.4 +/- 0.4 microM) than the glycosylated vWF-A1 protein (Kd = 4.5 +/- 0.9 microM) but had similar binding capacity of 28,000 GpIb/IX-specific binding sites per platelet. Additionally, both recombinant vWF-A1 proteins bound to heparin but neither bound to immobilized type I and III collagen. Both E. coli- and CHO-derived vWF-A1 proteins inhibited ristocetin-induced platelet agglutination with IC50 values of 300 and 700 nM, respectively. Reduction of the only disulfide bond between C509 and C695 abolished platelet binding activity at concentration up to 2 microM of protein. Confirmation of the importance of the 509-695 disulfide bond was obtained from a full-length vWF mutant containing substitutions at C509 and C695 (C509/695S) which failed to bind to the platelet GpIb/IX receptor. These studies document that vWF-A1 domain can bind to GpIb/IX and heparin but not collagen, and that binding to GpIb/IX requires an intact disulfide bond between C509 and C695. Furthermore, glycosylation increases the solubility but reduces binding affinity of recombinant vWF A1.

Animals↗

PubMed1993

Distribution of mast cells and the effect of their mediators on contractility in human myometrium.

OBJECTIVE: To examine the distribution of mast cells in human uterine tissue and to study the interactions between mast cell mediators (histamine and serotonin) and PGF2 alpha in human myometrium contractile activity. DESIGN: Distribution of mast cells were analysed in cryostat sections of myometrium samples stained with Toluidine blue. Contractile activity was evaluated in an isolated organ bath preparation on myometrial strips obtained from women whose pregnancies ended in elective caesarean section. SETTING: Biological Science Laboratories at the University of Concepción. SUBJECTS: Twenty women undergoing elective caesarean and 10 women undergoing hysterectomy at the G. Grant Hospital. MAIN OUTCOME MEASUREMENTS: Cumulative concentration-response curves for histamine and serotonin before and after the addition of subumbral concentrations of the PGF2 alpha or serotonin were performed. RESULTS: Serotonin was more active than histamine to evoke contractions (EC50:0.20 (SE 0.02) mumol/l vs 1.5 (SE 0.2) mumol/l, respectively). Furthermore, threshold concentrations of serotonin (0.05 mumol/l) potentiated the contractile effect of histamine (EC50:0.3 (SE 0.06) mumol/l and 50% increase in E(max)). PGF2 alpha had a poor contractile effect, but threshold concentrations (0.05 and 0.10 mumol/l) enhanced the contractile effect of both serotonin and histamine. A population of mast cells was found in close apposition to smooth muscle fibres. CONCLUSIONS: It is postulated that the simultaneous release of mast cell mediators (histamine and serotonin) in myometrium could be an important stimulus for evoking strong contractions in the human uterus. PGF2 alpha may have indirect effects in myometrium by amplifying the effects of histamine and serotonin.

Dinoprost↗

PubMed1993

Venous placental reactivity to serotonin in normal and preeclamptic gestants.

The effect of serotonin (5-HT) on the contractile activity of venous chorionic rings from normal and preeclamptic gestants was analyzed. The results indicate that the resting tension did not differ between the groups, but the spontaneous rhythmic contractions began earlier and were of higher amplitude in the preeclamptic group. Dose-response data indicate that venous segments from preeclamptic patients developed a 1.7-fold increase in sensitivity to 5-HT. These effects were accompanied by an increase in maximal isometric tension (Emax) and relaxation times. Decreased desensitization and lack of tachyphylaxis was observed in most of the vascular preparations from the preeclamptic group. These data suggest that 5-HT may have a role in the modulation of preeclampsia.

Chorionic Villi↗

PubMed1993

Serotonin-induced vasoconstriction in human placental chorionic veins: interaction with prostaglandin F2 alpha.

In vitro experiments using isolated rings and perfused segments of human chorionic veins, were designed to determine the effects of serotonin and their interaction with PGF2 alpha on vascular tension and perfusion pressure. These vessels responded vigorously with high sensitivity to the vasoconstrictor effects of serotonin in both experimental designs. Administration of PGF2 alpha also led to constriction of the veins, but this autacoid is at least 100 times less potent than serotonin. When adding PGF2 alpha previously to serotonin to the bathing fluid or to the perfusate, the serotonin response was significantly potentiated, increasing the maximal contractile response in 116 +/- 12% and the perfusion pressure in 180 +/- 25%. Both autacoids probably operate in this vascular bed interacting with each other and playing an important role in the regulation of placental blood flow in vivo.

Analysis of Variance↗

PubMed1992

[Comparative study of the survival of gastric B-cell lymphoma of mucosal origin with respect to lymph node lymphoma of similar histology].

BACKGROUND: The differences in clinical presentation, morphology, phenotype and genetic changes between lymphomas originating in the gastrointestinal tract and the lymph nodes justified the proposal of a system of specific classification for lymphomas originating in lymphoid tissue associated to mucosa (MALT). Nevertheless, there is no conclusive evidence that the types of lymphoma defined as such have a different clinical evolution with respect to the lymph nodes lymphomas. METHODS: With the aim of analyzing this problem a clinical follow up of 33 patients with primary gastric lymphomas (high and low grade) was compared with the results of a group of 99 lymphomas of the lymph nodes was carried out with classification according to the criteria of Kiel classification and the proposal by Isaacson et al for MALT lymphomas. Survival obtained by the Kaplan-Meier method was compared by the Mantel-Haenzel test. RESULTS: The results obtained showed that all gastric lymphomas have a less aggressive evolution than those of lymph node origin (p < 0.01). This significant statistical difference was also observed when lymphomas of similar histology were compared. Similarly, the subgroups of large cell lymphoma (p < 0.05) and small cells (p < 0.01) differ with respect to lymphomas of similar histology and of lymph node origin. In contrast with the results expected, no significant difference was observed between the two main groups of lymphomas of high and low grade mucosal origin. CONCLUSIONS: The analysis of the results supports the convenience of a system of specific classification for lymphomas of mucosal origin. Nevertheless, the specific existence of groups of high and low grade lymphomas is questioned since the probability of survival between both subgroups does not show statistically significant differences.

Gastric Mucosa↗

PubMed1992

Functional analysis of a recombinant glycoprotein Ib alpha polypeptide which inhibits von Willebrand factor binding to the platelet glycoprotein Ib-IX complex and to collagen.

By deletion mutagenesis and transient expression in COS cells, a 96-amino acid hydrophilic sequence in the glycoprotein Ib alpha polypeptide located between L220 and L318 was identified which appeared to contain its von Willebrand factor- (vWF) binding site. The cDNA encoding this fragment was then expressed in Escherichia coli and purified from the bacterial cell lysate. The recombinant polypeptide, rGpIb alpha Q221-L318, was monomeric and had an apparent molecular weight of 14,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It inhibited both ristocetin-induced binding of 125I-vWF to fixed washed platelets and ristocetin-induced platelet agglutination. The recombinant polypeptide also inhibited the binding of 125I-vWF to immobilized type I and III collagen. Inhibition of 125I-vWF binding to platelets and collagen was dose-dependent, with IC50 values of 500 and 200 nM rGpIb alpha Q221-L318, respectively. Fifty % inhibition of ristocetin-induced platelet agglutination required 500 nM rGpIb alpha Q221-L318. Although rGpIb alpha Q221-L318 inhibited vWF binding to collagen it did not, itself, bind to collagen-coated surfaces. Reduction of the disulfide bond between C248 and C264 abolished activity. 125I-rGpIb alpha Q221-L318 bound directly to GpIb/IX sites on multimeric vWF. These studies document that a portion of the sequence between Q221 and L318 is needed for recognition and binding to vWF and that binding requires an intact disulfide bond between C248 and C264. The binding of this recombinant polypeptide to vWF multimers inhibits vWF interaction with two important substrates, platelet GpIb/IX and collagen.

Adenosine Diphosphate↗

PubMed1992

Nicotine stimulates adrenergic terminals and inhibits contractions of mouse uterine horns.

1. Nicotine (1-100 microM) stimulated both basal and electrically evoked release of 3H-norepinephrine and also caused a transient inhibition of contractions in an in vitro preparation of mouse uterine horns. 2. The inhibitory effect of nicotine on electrically evoked contractions was potentiated by aminophylline (89 micrograms/ml), and overcome by both propranolol (1 microM) and by omitting magnesium from the physiological solution. Acetylcholine (10 microM), in the presence of atropine (10 microM) was able to reproduce the inhibitory effect of nicotine. 3. These pharmacological findings suggest that the inhibitory action of nicotine on electrically evoked contractions in mouse uterus could be indirect, i.e. mediated through the action of this compound on presynaptic nicotine receptors located on adrenergic terminals.

Acetylcholine↗

PubMed1992

Mast cells mediators evoke contractility and potentiate each other in mouse uterine horns.

1. The ability of prostaglandin F2 alpha (PGF2 alpha), histamine and serotonin to induce and/or potentiate contractions in mouse uterine horns was studied in an attempt to analyze whether uterine mast cells degranulation could favor contractions during labor. 2. PGF2 alpha was the most potent of the three compounds (EC50 = 0.7 microM), being followed by serotonin (EC50 = 1.2 microM) and histamine. Between 10 and 100 microM histamine only evoked weak contractions, not higher than 50% of maximal amplitude of contractions. 3. Serotonin (0.1 microM) potentiated the contractile effect of both histamine and PGF2 alpha when added simultaneously with the corresponding compound to the isolated organ bath. Also, histamine at threshold contractile concentration (3 microM) was able to potentiate the contractile effect of both serotonin and PGF2 alpha. 4. The potentiating effect of PGF2 alpha on both histamine and serotonin evoked contractions was recorded after treating the preparation with 10 microM of the compound for at least 10 min before the corresponding concentration-effect curves were performed. 5. It is postulated that the simultaneous presence of these mast cells mediators in myometrium could be an important stimulus for both to trigger and/or to maintain contractions during labor.

Animals↗

PubMed1991

Vasoconstrictive effect of bile acids on isolated human placental chorionic veins.

Intrahepatic cholestasis of pregnancy (ICP) is a rare complication of late pregnancy associated with a high rate of premature delivery, antepartum fetal death and fetal hypoxia. Since the principal biochemical feature of ICP is a marked elevation of maternal serum bile acid levels, a role of these substances in the pathophysiology of fetal complications has been suggested. In this study, the effect of bile acids on isolated human placental chorionic veins is described. High concentrations of bile acids, especially cholic acid, have a dose-dependent vasoconstrictive effect, which suggests that these substances could exert a detrimental effect on the fetus by increasing the resistance in chorionic veins through a vasospasm of the placental chorionic surface. An abrupt reduction of the oxygenated blood flow at the level of the placental chorionic plate may cause an acute impairment of the fetal perfusion and oxygenation, leading to fetal asphyxia. This is the first report that provides experimental evidence of the possible role of bile acids in those mechanisms that trigger fetal asphyxia in pregnancies complicated by ICP.

Bile Acids and Salts↗

PubMed1991

Effect of progesterone on norepinephrine release from mouse adrenergic terminals in vitro.

1. The in vitro effect of progesterone on norepinephrine (NE) release and contractile activity was analyzed in uterine horns from estrogen-primed and progesterone-primed mice. 2. Progesterone (6-10 nmol/ml) evoked the release of [3H]NE above basal levels from uterine horns in both experimental conditions, the effect of progesterone on estrogen-primed being more important than on progesterone-primed mice uterus. 3. Progesterone also increased electrically evoked [3H]NE release in estrogen-primed uterine tissue, nevertheless no effect was observed in progesterone-primed ones. 4. Progesterone (0.6-10 nmol/ml) inhibited uterine horn isometric contractions only in estradiol-primed mice. This effect was partially blocked in uterine horns from reserpine-treated mice and when propanolol (1 microM) was added to the preparation of estradiol-primed mice uterus.

Adrenergic Fibers↗

PubMed1991

Magnesium and potassium ions on tone and reactivity of human placental chorionic veins.

1. In vitro studies were undertaken to investigate the effects of external potassium [K+]0 2.4-7.1 mM and magnesium [Mg2+]0 0-4.8 mM concentration on human chorionic veins basal tone and on serotonin (5-HT)-induced contractions. 2. The higher the [Mg2+]0, the less the basal tension developed in isolated chorionic veins, irrespective of the [K+]0. 3. The EC50 value to 5-HT was enhanced by increases in [Mg2+]0, whereas the ability of 5-HT to induce a maximal contraction was attenuated. 4. The rightward shift of the concentration-response curves and reduced Emax response, observed when the concentration of [Mg2+]0 was raised, indicate a non-competitive antagonism of [Mg2+]0 with 5-HT. 5. The lack of an effect of [K+]0 on the EC50 and Emax values for 5-HT suggest that in this tissue the affinity of 5-HT for 5-HT receptors does not involve potassium. 6. These results suggest that basal tone and 5-HT-induced contractions of human chorionic vascular smooth muscle cells appear to be highly sensitive to alterations in extracellular Mg2+.

Chorionic Villi↗

PubMed1991

Effect of histamine on human placental chorionic veins: interaction with serotonin.

The vasomotor effects of histamine and its interaction with serotonin were studied in isolated human placental chorionic veins. Histamine induced concentration-dependent contractions with an EC50 of 8.7 +/- 1.2 x 10(-6) mol/l. The H1 antagonist, pyrilamine (10(-9) to 10(-7) mol/l), inhibited histamine-induced contractions, with a pA2 of 8.33 +/- 0.32 at a slope of 0.635. Cimetidine (H2 antagonist) had no effect on histamine-induced contractions. Serotonin (10(-9) to 10(-8) mol/l) significantly potentiated the contractile effect of histamine. The possible implications of the interaction between both amines in the regulation of placental blood flow is discussed.

Chorion↗

PubMed1990

[Low-grade B cell gastric lymphoma originated in mucosa-associated lymphoid tissue. Relationship of tumor cells with the marginal zone and monocytoid B lymphocytes. An immunohistochemical and ultrastructural study].

Seven cases of gastric B-cell low-grade lymphomas were characterized by morphology, immunohistology and electron microscopy. All them were immunophenotyped with a panel of monoclonal antibodies against immunoglobulins and other B-cell determinants. Histologic study of gastric B-cell low-grade lymphomas showed germinal centers of lobated shape and polyclonal nature, mainly polyclonal subepithelial plasma cell (except in one case) and neoplastic interfollicular B-cells of monoclonal character. Light-chain restriction supports the neoplastic nature of gastric lymphoma of low-grade malignancy, a distinctive tumour of extranodal B-cell origin. Interfollicular B-cells share with marginal zone cells a perifollicular localization, morphology and phenotype, suggesting a possible relation between these two cellular subtypes. In two cases, the tumour appears constituted by monocytoid B-lymphocytes (MBL), which suggests a relation of tumoral interfollicular B-cells with this subpopulation.

Adult↗

PubMed1990

Changes in the response to adrenergic drugs on mouse uterine contractions during pregnancy.

The effect of isoproterenol (ISO), norepinephrine (NE) and phenylephrine (PHE) on electrically-induced contractions of mice uterine horns was studied during pregnancy. At the different times of gestation adrenergic agonists always inhibited uterine contractions in the following rank order of potency: ISO greater than NE greater than PHE. Cumulative dose-response curves constructed for the effect of these amines during diestrous, and at days 3-7, 10-15, 17-21 of gestation, showed that EC50 values increased gradually as term approached, which could imply a lower capacity of the uterus to respond to adrenergic drugs. Some likely explanations for this phenomenon are proposed. It is suggested that this lower response to catecholamines at the end of pregnancy could be a cause for the reduced success of beta 2-adrenergic drugs to stop premature labor.

Adrenergic Agonists↗

PubMed1990

Cytotoxic/suppressor (CD8+, CD4-) cutaneous T-cell lymphoma with aggressive course.

A case of cutaneous cytotoxic/suppressor T-cell (CD8+, CD4-) lymphoma is reported. The tumor was characterized by its rapid growth and no response to polychemotherapy. This unusual immunophenotype seems to be associated, in this and other cases reported previously, with a more aggressive course than the classic indolent course of cutaneous T-cell lymphoma.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1990

Effects of serotonin on vascular tone of isolated human placental chorionic veins.

Vasomotor effects of serotonin (5-hydroxytryptamine; 5-HT) were studied in isolated human placental chorionic veins in vitro. 5-HT produced marked contraction with a maximum of 89 +/- 5.05% of the K(+)-induced contractions. This response was specifically and competitively antagonized by ketanserin at doses of 10(-9) and 10(-8) M (pA2 = 9.65). Ketanserin, at concentrations up to 10(-7) M, induced noncompetitive inhibition of the contractions. These findings show a marked vasoconstrictor effect of 5-HT on the capacitance vessels of the human placenta, which suggests that this amine could play an important role as a mediator of fetal circulation. The possible therapeutic effect of ketanserin as a vasodilator to improve blood flow in the uteroplacental unit, is also discussed, based on the ability of this drug to block competitively 5-HT effects on chorionic veins.

Chorion↗

PubMed1989

Effects of histamine and serotonin on the contractility of isolated pregnant and nonpregnant human myometrium.

The effects of histamine and serotonin and their antagonists on contractile activity of pregnant and nonpregnant human uterine strips were studied. Both histamine and serotonin (5-HT) increased contractions, pregnant preparations were more responsive than nonpregnant ones. The effects of histamine and 5-HT were blocked by pyrilamine and methysergide, respectively. Pyrilamine (10(-7)-10(-6) M) acted as a competitive antagonist of the effect of histamine, whereas methysergide (10(-7)-10(-6) M) inhibited the response to 5-HT in a noncompetitive manner. Cimetidine and ketanserine were completely ineffective at the doses tested. It is suggested that the increase of contractile activity observed at the end of pregnancy could be partly mediated by the effect of histamine and 5-HT on smooth muscle of the human myometrium.

Cimetidine↗

PubMed1988

Monocytoid B-cell lymphoma, a tumour related to the marginal zone.

Monocytoid B-lymphocytes are a B-cell subset present in subcapsular sinuses in some cases of lymphadenitis. We describe a case of lymphoma of this cell type. The tumour shows a distinctive morphology characterized by concentric strands of tumour cells around lymphoid follicles with hyperplastic germinal centres and conserved mantle zones. Electron microscopy of these cells shows short cellular processes as well as moderate development of endoplasmic reticulum. The phenotype of the tumour was monoclonal IgM-kappa, distinct from other node-based B-cell subpopulations and suggesting a possible relationship to the lymphocytes of the marginal zone present peripheral to lymphoid follicles of the spleen. Morphological features that suggest a relationship with hairy cell leukaemia are contrasted by phenotypic differences and the ultrastructural absence of ribosomic lamellar complexes.

Aged↗