PubMed Health⌕ Search

Biomedical subjects

R Solana

Publications and source records attributed to R Solana.

63 records · Page 4Linked to original sources
PubMed1980

Possible mechanism of stimulation of gastrin secretion by exogenous serotonin in rats.

The effect of 6-hydroxydopamine, propranolol, phentolamine, alpha-methyl-tyrosine and alpha-methyl-tyrosine plus propranolol on serotonin-stimulated gastrin secretion in rats has been examined. Gastrin secretion in response to administration of serotonin alone (10 mg/kg i.p.) was significantly reduced in rats pretreated with 6-hydroxydopamine or with propranolol. These results suggest that the effect of exogenous serotonin on gastrin secretion can be described as sympathomimetic and indirect. The serotonin-stimulated gastrin secretion was significantly enhanced by previous administration of phentolamine. Pretreatment with alpha-methyl-tyrosine also elevated serotonin-stimulated gastrin secretion, indicating that in the presence of diminished concentrations of the catecholamines, the influence of exogenous serotonin on secretion by G cells is increased. This enhancement in the serum gastrin levels was also reduced to a significant extent by simultaneous administration of propranolol, which suggested the activation of G-cell beta-adrenergic receptors after serotonin administration.

Animals↗
PubMed1980

Possible central antisecretory action of exogenous serotonin in rats.

The effect of exogenous serotonin (10 mg/kg i. p.) in rats pretreated and unpretreated with 6-hydroxydopamine, propranolol or with alpha-methyltyrosine on intragastric pH was studied. It was observed that after serotonin administration, the intragastric pH increased by approximately five units. The chemical sympathectomy by administration of 6-hydroxydopamine did not alter significantly either basal intragastric pH or the serotonin-induced increase of intragastric pH. The administration of propranolol did not alter significantly the basal intragastric pH, whilst the pretreatment with propranolol abolished the antisecretory effect of serotonin. Repeated dosages with alpha-methyl tyrosine did not alter the basal intragastric pH, but inhibited the effect of serotonin or intragastric pH. These results seem to indicate that the antisecretory effect of exogenous serotonin on gastric acid output, is caused by the inhibition of the vegetative brain centres responsible for the secretory activity of the parietal cells. Furthermore, it is suggested that the antisecretory effect of serotonin is mediated by a release of noradrenaline from the brain adrenergic neurones.

Animals↗
PubMed1979

Effect of exogenous serotonin on intragastric pH and its influence on serum gastrin levels in rats.

The effect of various doses of serotonin on the serum gastrin levels and intragastric pH in rats, was studied. After serotonin administration of 10 mg/kg i.p., a significant increase in serum gastrin levels was noted, as well as a strong increase in the intragastric pH. It was also observed that a lower dose, 5 mg/kg i.p., significantly increased serum gastrin levels, while intragastric pH was not affected, remaining at baseline values throughout the study. These results suggest that the increase observed in serum gastrin levels after administration of exogenous serotonin is not mediated by increase in intragastric pH.

Animals↗
PubMedDate not supplied

Expression of HLA molecules on cells from fresh explants of human digestive tract cancer.

It has been recently established that there is a correlation between the lack of MHC class I gene expression on murine tumour cells and their ability to grow and metastasize. We have studied the expression of HLA-ABC and HLA-DR products on human malignant tumours from the digestive tract using monoclonal antibodies, by indirect immunofluorescence on the cell suspensions obtained from 29 freshly explanted digestive tumours. Our results show that digestive tract cancers have an heterogeneous expression of HLA class I molecules on their surface. Whereas 50% have high levels of expression of these molecules (more than 60% positive cells), 25% have a moderate level of expression (20-60% positive cells) and 25% have weak expression (less than 20% positive cells). It has been found that there is a correlation between the level of HLA class I molecule expression and the degree of histological differentiation of a tumour. The absence of MHC class I antigens on human tumour cells, detected in this study, may play a relevant role in oncogenesis, as has been established in experimental models.

Cell Differentiation↗
PubMedDate not supplied

Modulation of the expression of HLA class II antigens by gamma interferon and phorbol ester TPA on myeloid leukaemic cell lines.

We investigated the effect of gamma interferon and phorbol ester (TPA), on the expression of HLA class II molecules of myeloid leukaemic cell lines K562, U937, KG-1, HL-60 and ML-2. Gamma interferon induced the expression of HLA-DR but not HLA-DQ on HL-60 and ML-2, increased the expression of HLA-DR and DQ on U937 and induced the expression of HLA-DQ on KG-1. TPA treatment did not affect the expression of HLA class II antigens on U937 and KG-1 and induced the expression of HLA-DR and HLA-DQ on HL-60 and ML-2. TPA treatment did not affect the HLA phenotype of K562 but gamma interferon did induce HLA class I molecules. Thus, gamma interferon cannot only increase the expression of HLA products already expressed on the cells but can also induce the de novo synthesis of these molecules on myeloid leukaemic cell lines.

Cell Line↗
PubMedDate not supplied

MHC class I expression on human tumour cells and their susceptibility to NK lysis.

Although natural killer (NK) activity is not restricted by the major histocompatibility complex (MHC), it has been suggested that the level of expression of MHC antigens by target cells may influence their lysis by NK cells. We have studied the NK susceptibility of 20 cell lines obtained from primitive and metastatic human tumours and the K562 cell line treated with gamma-interferon, phorbol ester TPA and tumour factor NK-RIF. When the levels of MHC class I antigen expression on the human tumour cell lines and their NK susceptibility were compared, no relationship between these two parameters was observed. Furthermore the treatment of K562 with either gamma-interferon, TPA or NK-RIF decreased its NK susceptibility independently of MHC class I expression. These results indicate that the MHC class I antigen is not the only factor directly involved in NK susceptibility and suggest that other membrane structures modulated by gamma-interferon, TPA or NK-RIF may also influence NK susceptibility.

Cytotoxicity, Immunologic↗
PubMedDate not supplied

Changes in the expression of HLA-class II antigens on peripheral blood monocytes from aged humans.

Increased incidence of infections, cancer, monoclonal gammopathies and rheumatic diseases in aged humans has been described. Histocompatibility antigens are involved in the regulation of immune response and it has been suggested that age-related alterations in the murine immune system may be due to changes in the expression of these antigens on the immunocompetent cells. In this paper we study the expression of HLA-DR/DP and HLA-DQ antigens on monocytes from healthy human elderly donors. Results show that peripheral blood monocytes from elderly subjects express decreased levels of HLA-DR/DP antigens (61.5 + 16.3) when compared to young controls (82.5 + 8.5) and increased levels of HLA-DQ antigens (40.4 + 16.8 and 23.6 + 7.1, respectively). The abnormal levels of expression of HLA-class II molecules could be related to the altered immune functions observed in elderly people.

Aged↗
PubMedDate not supplied

PHA reactivity of spontaneous AKR lymphomas: absolute macrophage requirement.

The study of patients with T cell lymphoproliferative disorders often demonstrates a reduced response to mitogens. The T cell lymphoma in AKR mice has been considered a classic experimental model of T cell leukaemias. In this paper ten spontaneous lymphomas from AKR mice were characterized individually in vitro for PHA reactivity. After 60 h. of culture, spontaneous 3H-Thymidine uptake by nylon wool purified spleen cells from individual lymphomas oscillated between 4.724 and 81.125 cpm. These nylon wool purified leukemic cells were not responsive to PHA (S.I. less than 2.5). When these cells were cocultured with an adequate macrophage concentration in the presence of PHA, all could be considered responsive to the mitogen (S.I. greater than 2.5). Results indicate that AKR leukemic cells are responsive to PHA in an absolutely macrophage dependent way.

AKR murine leukemia virus↗