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Biomedical subjects

M C Rubio

Publications and source records attributed to M C Rubio.

At least 109 records · Page 6Linked to original sources
PubMed1983

Catecholamine metabolizing enzymes and synthesis of dopamine in normal and grafted pituitary partes distales.

The presence of enzymatic activity (tyrosine hydroxylase, dopa-decarboxylase, dopamine-beta-hydroxylase, monoamine oxydase and catechol-O-methyl transferase), as well as dopamine (DA) content and DA synthesis from tyrosine and dopa, were investigated in intact rats partes distales and in grafts (both estrogenized and nonestrogenized). Counts of prolactin cells showed the following regression in the number of these cells: estrogenized grafts greater than nonestrogenized grafts greater than intrasellar intact glands. Tyrosine hydroxylase activity was not found in intact glands, but this enzyme was detected in the two types of grafts. An approximate correlation could be established between the number of prolactin cells and the diverse enzyme activities. Dopamine was not synthesized from tyrosine in intact glands, but it occurred in the transplants. However, when dopa was used, both intact and grafted glands produced dopamine. Estrogen administration decreased dopamine content in all the glands investigated. The significance of these results in relation to the physiology of the pars distalis is discussed.

Animals↗
PubMed1983

Presence of 5-hydroxy-indolacetic acid in Diloboderus abderus larvae without monoamine-oxidase-like activity.

The authors confirmed the presence of monoamines and 5-hydroxy-indolacetic acid (5-HIAA) in the cephalic region of Diloboderus abderus larvae employing a high pressure liquid chromatography (HPLC) with electrochemical detector. An anticholinesterase insecticide produced an increase in the serotonin and 5-HIAA endogenous levels, and did not modify the catecholamines. Monoamine-oxidase activity was undetectable with a radioactive method using 3H-tyramine as substrate.

Animals↗
PubMed1982

Pharmacological effects of ionophore A-23187 on isolated guinea-pig atria and isolated cat nictitating membrane.

1. The present paper is concerned with some pharmacological actions of ionophore A-23187 on both isolated guinea-pig atria and cat's nictitating membrane. 2. The drug showed an agonist effect on both tissues. 3. There is an indirect effect by releasing catecholamines which is antagonized by reserpine and beta receptor blockers in atria and alfa receptor blockers in nictitating membrane. 4. The ionophore exhibited a direct positive chronotropic effect on the atria. This effect is blocked by Ca2+ flux antagonist such as verapamil and pentobarbital and not by reserpine. 5. Ionophore produced no direct effect on the activity of the isolated tyrosine hydroxylase but showed an inhibitory action in intact tissues, mediated by released of endogenous catecholamines, since this effect is antagonized by reserpine. 6. Monoamine oxidase activity was unaffected by ionophore.

Animals↗
PubMed1982

[Gastroenteritis caused by Campylobacter jejuni in childhood].

Fifteen patients with stool growth of "Campylobacter jejuni" are presented. In one case it was associated with growth of "Salmonella typhimurium". Fourteen cases presented as an acute gastroenteritis whereas the remainder case was considered to be an asymptomatic carrier. The incidence was 5.8%. The disease was more frequent in infancy (13 cases occurred in ages below one year). Diarrhea was the most frequent symptom (93.3%), with presence of macroscopic blood in the stool in 78.5% of these cases. In three cases the process was associated to cow's milk protein-sensitive enteropathy. Four patients were treated with erythromycin and the stool culture become negative at the end of therapy. In the untreated cases the stool culture become negative within a period from five to 15 days. In the asymptomatic carrier the stool culture become negative after a period of two months.

Animals↗
PubMed1981

Decreased 3H-L-quinuclidinyl benzilate binding and muscarine receptor subsensitivity after chronic gamma-butyrolactone treatment.

A significant decrease in the number of 3H-quinuclidinyl benzilate (3H-QNB) binding sites in striatal membranes was observed in rats exposed to gamma-butyrolactone (GBL) during 3 weeks. This decrease in 3H-QNB binding was not due to a direct effect of GBL on muscarine receptors since no alterations of binding were produced by high concentrations of GBL or of its active metabolite gammahydroxybutyric acid (GHB) when added in vitro. Challenge doses of pilocarpine were less effective in producing catalepsy and tremors in rats chronically treated with GBL. It is proposed that the partial inhibition of the nigro-striatal dopaminergic pathway produced by chronic GBL treatment leads to a persistent activation of the intrastriatal cholinergic interneurons, which are tonically inhibited by dopaminergic nigrostriatal neurons. The activation of striatal cholinergic interneurons results in a decreased number of muscarine receptors and in a lower sensitivity to cholinomimetic agents. Moreover, tolerance to the anesthetic effect of GBL was found to occur after chronic treatment with this drug. The brain levels of GHB at the time of regaining of the righting reflex were 50% higher in GBL pretreated animals then in controls. Indicating the tolerance to GBL-induced "sleep" is due to a decrease sensitivity of the effector to GHB rather than to a faster inactivation of elimination of the drug.

4-Butyrolactone↗
PubMed1981

Abnormal histamine metabolism in a transplantable syngeneic spontaneous murine mammary adenocarcinoma.

Histamine metabolism of a transplantable syngeneic spontaneous murine mammary adenocarcinoma with a high degree of undifferentiation was studied. The endogenous histamine content is significantly higher than in normal intestine and lung. This is not due to an increase of the histamine biosynthetic capacity, which is lower than in the lung. The administration of histamine, 0.1 mg per kg body, for 7 days, decreased significantly the biosynthesis of histamine in the tumor, but not its endogenous histamine content; in the intestine and in the lung no significant modification of histamine biosynthesis was observed. It has also be shown that the proportion of radioactivity in the purified nuclear fraction of the tumor is significantly higher than in the intestine, after incubating either tissue with 3H-histamine. Since the mast-cell content of the tumor has been found to be low, our results should be considered as a specific alteration of the function of histamine in these tumor cells.

Adenocarcinoma↗
PubMed1980

Quantification of plasminogen activator activity associated with herpesvirus-transformed cells.

Herpesvirus-transformed cell lines were examined for plasminogen activator (PA) activity using a quantitative assay. Previous results of cold fibrin overlay assays indicated that herpesvirus-transformed hamster cell lines produce fibrinolytic activity. Quantification of this activity involved the use of an 125I-fibrin lysis assay in which medium previously incubated with transformed or normal cells was tested for its ability to lyse 125I-fibrin polymers. This assay indicated an enhanced production of plasminogen-dependent fibrinolytic activity by transformed hamster cells compared to hamster embryo fibroblasts. The kinetics of secretion failed to reveal a significant difference in plasminogen activator activity in cells transformed by either herpes simplex virus types 1 or 2 (HSV-1 or HSV-2); however, transformed cells exhibited a significant increase in activity over non-transformed cells. Further characterization of PA activity associated with cells transformed by HSV-1 or HSV-2 has revealed that the protease is secreted and can function extracellularly. Extracellular PA activity produced by HSV-transformed cells is detected more efficiently than the cell-associated enzyme. Extracellular PA can be induced in two different species of cells by infection with partially inactivated HSV-2. Lytic infection of human embryo lung cells by HSV-2 strain 333 did not enhance activity, but infection of these cells with virus inactivated by u.v. irradiation resulted in increased PA levels from the cells. Increased enzyme levels were also detected in hamster embryo fibroblasts infected with partially inactivated virus. Further investigation of this enzyme function may determine whether increased levels of protease will indicate oncogenic transformation in vitro by herpesviruses.

Animals↗
PubMed1980

Effect of chronic alcohol feeding on adrenergic and cholinergic neurotransmission mechanism.

Experimental data is presented indicating that chronic alcohol consumption in rats has a direct CNS effect resulting in increased activity of the autonomic nervous outflow. Changes in neurohormonal transmitters have been demonstrated in four organs: salivary glands, spleen, adrenals and heart. These changes may account for the alterations in end organ sensitivity and secretory patterns which occur in alcoholic animals and man. They may, moreover, represent an initial pathogenetic mechanism whereby alcohol induces its various clinical syndromes.

Acetylcholinesterase↗
PubMed1979

Modulatory role of catecholamines on tyrosine hydroxylase induction.

The possible modulatory role of cytoplasmic catecholamines on tyrosine hydroxylase induction was studied. Rat superior cervical ganglia were kept in organ culture and after 48 h tyrosine hydroxylase activity was determined. Exposure to 10(-4) M carbachol during 4 h almost doubled the control activity. Incubation with 10(-5) M noradrenaline or 10(-5) M dopamine impaired the carbachol-mediated induction of the enzyme. This effect was not blocked by 10(-7) M propranolol, 2.4 X 10(-6) M haloperidol or 3.1 X 10(-6) M phentolamine. Inhibition of monoamine oxidase activity by 5.1 X 10(-4) M pargyline inhibited the effect of carbachol. When the pool of endogenous catecholamines was decreased by alpha-methyl-p-tyrosine, carbachol induced tyrosine hydroxylase to the same extent as in non-depleted ganglia. It is suggested that the long-term regulation of tyrosine hydroxylase is modulated by a strategic cytoplasmic pool of catecholamines.

Animals↗
PubMed1978

Acetylcholine-like activity in the fruit of the black nightshade (Solanaceae).

The presence of acetylcholine in aqueous extracts of the fruit of Solanum nigrum Linn. (black nightshade) has been established based upon the following pharmacological tests: a) isotonic contraction of the isolated toad rectus abdominis; b) negative chronotropic and inotropic action on the isolated toad heart; c) isotonic contraction of the isolated guinea pig's ileum; d) isotonic contraction of the rat's isolated jejunum; 3) decrease on the cat's arterial blood pressure; f) secretory effects on the rat's submaxillary gland. These actions were selectively blocked by curate or atropine and disappeared after incubation of the extract at 37 C with plasma. Further evidence showing that the fruit of the black nightshade contains acetylcholine was obtained by chromatographic separation of the aqueous extract. The average content of acetylcholine was found to be 250 micrograms/g of fruit.

Acetylcholine↗
PubMed1978

Biosynthesis and subcellular localization of histamine in H-110 lymphoma.

The histidine decarboxylase activity has been studied in the H-110 Lymphoma implanted in Balb-c mice. The enzymatic activity has been determined using DL-Histidine 1-14C by measuring the I--14CO2 liberated during the incubation. It has been found that the histidine decarboxylase activity in the tumor is the highest of the studied tissues. The pretreatment for 5 days with two cytostatic drugs, cyclophosphamide and 5-fluoruracile, determined a decrease of the enzymatic activity in the tumor of 33 and 54 per cent, respectively. This effect has not been observed in the lung. The pretreatment of the animals during 10 days with 0.1 mg per kg body of histamine, which in other experimental tumors induces an increase of the endogenous content of histamine, produces a decrease of the tumoral histidine decarboxylase activity. The histamine-14C uptake was not modified by this pretreatment. The subcellular localization of the radioactivity after pretreatment with histamine-14C evidenced that the nuclear fraction of the tumor contained between 2 and 10 times the radioactivity of other tissues of the same animal.

Animals↗