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Biomedical subjects

H Folch

Publications and source records attributed to H Folch.

At least 19 recordsLinked to original sources
PubMed2004

Ultraviolet exposure of thymocytes: selective inhibition of apoptosis.

PURPOSE: To evaluate selective effects of ultraviolet (UV) irradiation on spontaneous and induced apoptosis in freshly extracted mice thymocytes. MATERIALS AND METHODS: Cells were exposed to UV radiation with emission peaks of 365 nm (UVA) exposures of 1620-10200 J m(-2), of 312 nm (UVB) exposures of 34-1620 J m(-2) or of 254 nm (UVC) exposures of 1.5-1620 J m(-2), and incubated for 5.5 h with or without hydrocortisone, phorbol-12-myristate-13-acetate or anti-Fas antibody. Additionally, cells were irradiated with gamma-rays (5 Gy) before UVB exposure (408 J m(-2)) at different times. Apoptosis was quantified by DNA fragmentation. RESULTS: Up to an irradiation of 5000 J m(-2), UVA exposure did not show any effect on thymocyte apoptosis, while at 10200 J m(-2) irradiation, considerable DNA fragmentation was observed. In contrast, UVB and UVC irradiation clearly inhibited natural and cortisone-induced apoptosis. Moreover, UVB inhibited apoptosis triggered by phorbol-12-myristate-13-acetate and gamma-irradiation, but not by anti-Fas antibody. CONCLUSIONS: The response of mouse thymocytes in culture to UV irradiation strongly depends on the wavelength used. It is suggested that either a survival or an apoptotic pathway occurs depending on the physiological state of the cell, spectral composition of the UV light and cell type. The possible involvement of extracellular signal-regulated kinase and stress-activated protein kinase/c-Jun N-terminal kinase in the apoptotic pathway is discussed.

Animals↗
PubMed2000

Frequent exposure of mice to crude Brucella abortus proteins down-regulates immune response.

Mice repeatedly immunized via the intraperitoneal route with a Brucella abortus antigen lost their ability to develop a strong in vitro lymphoproliferative response. This result correlates with a decreased tendency of the lymphoid population to produce interferon-gamma when stimulated in culture with the immunizing antigen. With respect to the humoral response, as the number of immunizations increased, the animals produced more specific immunoglobulin M and immunoglobulin G1 antibodies. It is postulated that the long-term exposure of an animal to Brucella antigen changes the nature of the immune response from a T-cell-mediated response to a humoral response favouring the establishment of the disease.

Animals↗
PubMed1999

Vaccination with live Escherichia coli expressing Brucella abortus Cu/Zn superoxide dismutase protects mice against virulent B. abortus.

Vaccination of mice with Escherichia coli expressing Brucella Cu/Zn superoxide dismutase (SOD) [E. coli(pBSSOD)] induced a significant level of protection against virulent Brucella abortus challenge, although this level was not as high as the one reached with B. abortus vaccine strain RB51. In addition, vaccination with E. coli(pBSSOD) induced antibodies to Cu/Zn SOD and a strong proliferative response of splenocytes when stimulated in vitro with a thioredoxin-Cu/Zn SOD fusion protein.

Animals↗
PubMed1998

Production and characterization of monoclonal antibodies to the major protein of boar outer dense fibers.

Outer dense fibers (ODF) are structural elements in the mammalian sperm tail which surround the axoneme in the midpiece and principal piece and probably may help to maintain the elastic structures and elastic recoil of the sperm tail. In the present study, we have generated and characterized and describe a series of monoclonal antibodies (mAbs) against the 30 kDa major protein from boar ODF. For antibody screening an ELISA was developed using a newly developed method to fix the ODF proteins to the solid phase. A total of seven mAbs were selected and characterized by ELISA, Western blot and immunofluorescence. The mAbs recognize the major protein component of boar ODF on preparative Western blot and mark the mid- and principal piece of demembranated flagella. These mAbs also recognize the mid- and principal piece of demembranated human spermatozoa from normozoospermic patients, but not from those with asthenozoospermia. For the first time, we succeeded in obtaining hybridoma cell lines that secrete mAbs of class IgM, which react with the 30 kDa protein of boar ODF.

Animals↗
PubMed1996

[Intervention of Campylobacter jejuni subsp. jejuni flagella in the adhesion to cellular cultures: bacteriological and immunological evidence].

The participation of the flagella of a virulent strain (O52) of Campylobacter jejuni subsp. jejuni in the adhesion to HEp-2 cells and their inhibition by means of homologous polyclonal antibodies, monoclonal anti-flagella antibodies and colostral natural antibodies (IgA) was studied. An aflagellated strain (T1) was used as negative control. Adhesion was observed in higher rates with O52 strain (72%) than with T1 strain (27.5%). Polyclonal, monoclonal and colostral antibodies inhibited O52 strain adhesion in more than 70% (p < 0.001). T1 strain adhesion was inhibited only by polyclonal and colostral natural antibodies. Our results suggest that the flagella of C. jejuni subsp. jejuni could participate effectively in the adhesion process. However, the inhibition of T1 strain by polyclonal and colostral antibodies suggests the existence of other binds of adhesins in the bacterial surface.

Bacterial Adhesion↗
PubMed1996

[Participation of Campylobacter jejuni flagellar epitopes in cellular adhesion].

Using a flagellated (052) and an aflagellated (T-1) strains we studied the participation of flagellar epitopes of C. jejuni in the adhesion to HEp-2 cells in vitro. Strain 052 was significantly more adherent than strain T-1. When adhesion assays were carried out with antiflagella monoclonal antibodies, strain 052 showed inhibition of their adhesive capacity that varied between 64.3 and 92.9%. With an ELISA test it was demonstrated that those monoclonal antibodies were specific and directed exclusively against flagellar epitopes of strain 052 being unreactive with strain T-1. Our results show that flagellar epitopes could participate in the adhesion process suggesting that flagella could be involved in the installation of the infectious process.

Antibodies, Monoclonal↗
PubMed1995

Induction of apoptosis in thymocytes: new evidence for an interaction of PKC and PKA pathways.

The second messenger cascades connected to PKC and PKA are involved in the induction of apoptosis. Here we study the interaction of those two second messenger pathways with respect to the induction of apoptosis by stimulation or inhibition. The stimulators used were phorbol dibutyrate for PKC and one of the cAMP agonists Sp-5,6 DCl-cBIMPS or Sp-cAMP for PKA. The inhibitors used were staurosporin for PKC and the cAMP antagonist Rp-cAMPS for PKA. We found a synergism between both second messenger systems with regard to the induction of apoptosis in thymus lymphocytes.

Animals↗
PubMed1994

Radiation induced membrane changes and programmed cell death: possible interrelationships.

A short review of the evidence that lymphocyte membranes are a target for the initiation of irradiation induced programmed cell death (PCD) is given. It is assumed that for lymphocytes PCD represents an essential physiological mechanism in order to prevent degeneration of the biological system involved. Initiation of PCD can be obtained by a pharmacological activation as well as with irradiation. In both cases, protein kinase-C (PKC) is involved in the signal transduction from the cellular membrane to the nucleus where, by means of a metabolically active process, DNA fragmentation is induced. It is hypothesized that processes connected to lipid peroxidation in the cell membrane constitute a primary effect of irradiation induced PCD, where membrane fluidization or a compensatory process aimed to the maintenance of membrane fluidity (membrane homeoviscosity hypothesis) are likely to be involved.

Animals↗
PubMed1992

A flow-cytometric method to study DNA fragmentation in lymphocytes.

A method to measure DNA fragmentation cell by cell in a cell population was implemented based on acridine orange procedure to determine DNA content of single cells by flow cytometry. Using this method it can be observed that the fragmentation process induced by irradiation in thymic cells occurs in a fraction of the population, thus indicating that this process is not evenly distributed over the total population, and that it corresponds to a fast phenomenon in which the cells suddenly lose DNA material.

Acridine Orange↗
PubMed1992

Role of protein kinase-C in thymocyte apoptosis induced by irradiation.

The role of protein kinase C in radiation-induced death of thymocytes was studied. For this purpose murine thymocytes were irradiated and incubated for 6 h at 37 degrees C and afterwards the fraction of fragmented DNA was measured. Results indicate that radiation-induced DNA fragmentation can be prevented by adding the protein kinase C inhibitor H-7 or staurosporine to the thymocytes during incubation time. Incubation of irradiated cells with HA-1004, an inhibitor of cAMP-dependent protein kinase, with a minor effect on protein kinase C did not affect the DNA fragmentation induced by irradiation. Incubation of cells with phorboldibutyrate gave a dose-dependent induction of DNA fragmentation. This effect can be inhibited by staurosporine. These results suggest that radiation-induced DNA fragmentation is an active cellular process in which protein kinase C plays an important role.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1992

Age-related capacity of neuroendocrine factors to differentiate T cells in vitro.

The present report shows the capacity of hypothalamic extract (HE) to differentiate bone marrow cells to Thy-1+ cells in vitro. A two-step short-term culture was used. In the first step thymus and pituitary were co-cultured in the presence of HE. Supernatant was then transferred to a bone marrow cell suspension and following a period of culture, the percentage of Thy-1+ cells was determined by a microcytotoxicity assay. Results indicated that: (a) HE from young mice show a very efficient differentiating capacity; (b) HE from young mice is equally efficient when old pituitary, thymus and marrow are used; (c) HE from old donors has no capacity to differentiate T cells; (d) there is a progressive age-related decline of this capacity; and (e) there is a feed-back mechanism involved in this process. It is concluded that hypothalamic factors can regulate the differentiation of T cells and that this effect operates through a mechanism involving pituitary and thymus.

Aging↗
PubMed1991

Rise in thymocyte number and thymulin serum level induced by noise.

A high level of noise is known to induce important changes in the immune system. In this work, the effect of sound stress on the circulating level of thymulin and on the cellularity of the thymus gland was studied. The experiments were done in RK mice exposed to a noise level of 100 dB for a period of 1 h. Following the noise exposure, the animals were bled at different times for thymulin titration, or killed in order to evaluate the number of cells and the weight of each thymus. The results indicate that young mice exposed to the stressor stimulus show an increase in serum thymulin titre, and at the same time they show an increment in thymus weight and in thymocyte number compared to control. These results support a new argument in favour of the theory of a central nervous system control on the thymus function.

Age Factors↗
PubMed1991

Radiation-induced surface IgG modulation: protein kinase C involvement.

Although radiation-induced loss of surface IgG (s-IgG) expression on murine B cells is known to be dependent on intact energy metabolism and integrity of the cytoskeleton, the exact mechanism of this radiation effect is not known. Evidence reported here shows that inhibition of protein kinase C (PKC) by H-7 impairs the radiation-induced s-IgG modulation, whereas addition of HA-1004, which preferently inhibits c-AMP-dependent protein kinase, shows only minor effects. On the other hand PMA, a PKC activator, mimics the radiation effect, and H-7 but not HA-1004 inhibits the PMA-induced loss of s-IgG expression. Therefore it is suggested that PKC is involved in the modulation of s-IgG induced by irradiation on B cells. The possibility of membrane participation in this event is discussed.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1991

Experimental autoimmune thyroiditis. II. An immunocytochemical and ultrastructural study of the lesion.

The early steps of thyroid damage in experimentally induced autoimmune thyroiditis in mice were studied. Mice were immunized with 150 micrograms of rat thyroglobulin followed by 20 micrograms of bacterial LPS 3 h later on day 0 and 7. Thyroid glands were obtained on days 14, 21 and 28 in order to be studied by light microscopy, electron microscopy and immunocytochemical techniques. The initial lesion was a focal inflammatory infiltrate composed of lymphocytes and lymphoblasts, and plasma cells as the damage progressed. In some cases an increase in neutrophils, macrophages and eosinophils was also seen. The infiltrate became multifocal and eventually diffuse and in few cases germinal center-like structures were seen. The cellular infiltrate corresponded to IgG, IgM and IgA bearing B cells and to a lesser degree Thy 1.2, Lyt 1 and Lyt 2 bearing T cells. Follicular alterations corresponded to different degenerative states of the follicular cells that in some cases was seen without the participation of lymphoid cells. Another mechanism observed was the migration of small lymphoid cells and plasma cells between the follicular cells.

Animals↗
PubMed1990

Protein kinase-C involvement in thymocyte apoptosis induced by hydrocortisone.

The involvement of protein kinase-C in thymocytes death induced by hydrocortisone was studied. Thymus cells were incubated 6 hr or in the presence of hydrocortisone, labeled with Acridine orange, and the DNA content of each nuclei was estimated by cytofluorimetry. The results indicate that hydrocortisone-induced DNA fragmentation can be prevented by adding the protein kinase-C inhibitor H-7 to the cell suspension. Incubation of the H-A 1004, an inhibitor of c-AMP-dependent protein kinase, with low effect on on protein kinase-C, did not interfere with the cortisone-mediated DNA fragmentation. Therefore, it can be concluded that protein kinase-C plays an important role in the process of lympholysis mediated by corticoids.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1989

Comparison of protein components of different species and strains of Brucella.

The proteins constituents of Brucella abortus, Brucella melitensis and Brucella ovis were analyzed SDS-PAGE. From the comparison appears that the three species of Brucella studied shows a different electrophoretic pattern specially at the level of small peptides. On the contrary when two strains of B. abortus are analyzed no differences can be noticed.

Bacterial Proteins↗
PubMed1989

Experimental autoimmune thyroiditis. I. Participation of IgA, IgM and IgG in the development of the disease.

Many factors have been shown to be important in the pathogenesis of experimentally induced autoimmune thyroiditis (EAT) in mice. However, the role of thyroid antibodies has not been clearly established. EAT was induced with rat Tg + LPS in RK mice. Two injections were given i.v. on days 0 and 7 and the antibody titre against rat and syngeneic Tg was determined in the weeks thereafter. Determination of the cellular infiltration of the thyroid, the presence of IgA, IgG and IgM in thyroid sections and electron microscope analysis of electro-dense deposits were also undertaken. Results show that (1) RTg + LPS is a potent inducer of autoimmunity with high antibody titer to RTg and MTg and 100% of the mice showed some degree of thyroid infiltrate on days 21 and 28; (2) immunofluorescence staining revealed that initially IgM is the main immunoglobulin and is later replaced by IgG. IgA is constantly present throughout the experimental period; (3) electro-dense deposits were found almost exclusively between the capillary basement membrane and the follicular basement membrane.

Animals↗