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Biomedical subjects

C Fernandez

Publications and source records attributed to C Fernandez.

At least 199 records · Page 11Linked to original sources
PubMed1982

Specific cells of human amnion selectively localize prolactin.

The presence of PRL in high concentration in human amniotic fluid has been related to changes in water transport across amnion but not chorion leave. The cellular composition of human amniotic epithelium has been reported to include at least two structurally distinct cell types, known as light cells and dark cells, that differ in their ability to transport large molecules. In the present study, human amnion obtained from term cesarean section was evaluated through the use of autoradiography as to its ability to localize hormones of similar and variant molecular sizes. Amniotic epithelium exposed to [125I]human PRL, [125I]human Gh, [125I]human beta-endorphin, [125I]bovine FSH, and sodium 125I alone was found to display a selectivity in its ability to localize [125I]human PRL only. Furthermore, the selective localization of [125I]human PRL was found to be specific to the light cells, because dark cells failed to localize any of the other tracers used. These data provide additional evidence in support of the recently proposed concept that term human amniotic epithelium consists of at least two functionally distinct cell types. Furthermore, the high levels of PRL in amniotic fluid may have a specific physiologic role in the amniotic membrane during human gestation.

Amnion↗
PubMed1982

Dextran-sulfate: a mitogen for human T lymphocytes.

Dextran-sulfate (DxS) induced proliferation of human peripheral blood T lymphocytes but not of adult or neonatal B lymphocytes. The mitogenic activity on T cells by DxS required the presence of accessory cells because DxS was unable to trigger T cells to DNA synthesis in the absence of accessory cells. In addition, DxS stimulated OKT4+8- T cells to produce interleukin 2, a process that also occurred only in the presence of accessory cells. Cyclosporin-A strongly suppressed T cell proliferation induced by DxS by rendering T cells unresponsive to interleukin 2 and by inhibiting the synthesis of this T cell growth factor by OKT4+ T cells. These results indicate that DxS is a mitogen for human T lymphocytes but not for adult or neonatal B lymphocytes. The mechanism by which DxS triggers T cells is discussed.

Antibodies, Monoclonal↗
PubMed1982

Limited life span of extensively proliferating B cells: no evidence for a continuous class or subclass switch.

The polyclonal B cell activators (PBA) dextran sulphate (DxS) and lipopolysaccharide (LPS) induce a marked synergistic response in mouse splenic B cells. Such activated B cell blasts could be maintained in culture for a total period of 15 to 20 days, provided the cells were subcultured repeatedly in fresh medium containing the PBA. After this time period activation could no longer be achieved. The B cell blasts responded at all times better to LPS plus DxS than to either PBA added alone. Furthermore, LPS-induced B cell blasts also responded better to LPS plus DxS than to LPS alone. Activated cells secreted IgM and switched to IgG3 and IgG2b secretion. At the end of the culture period, approximately one cell out of four secreted IgG. The kinetics of IgG3 and IgG2b production were similar, and the fraction of cells secreting these subclasses increased at similar rates throughout the culture period. We conclude that high-rate secreting and proliferating B cells have a limited life span. Furthermore, most activated B cells do not seem to go through a continuous subclass switch but keep on secreting the subclass they originally switched to.

Animals↗
PubMed1981

A synergistic polyclonal response to dextran sulphate and lipopolysaccharide: immunoglobulin secretion and cell requirements.

The effects of the simultaneous addition of lipopolysaccharide (LPS) and dextran sulphate (DxS) were studied in a low-cell density culture system, which enables extensive cell proliferation and high immunoglobulin secretion. Using these two mitogens, a synergistic response was observed, with regard to both cell division and IgM secretion. However, only a very low IgG production could be detected. This was caused by the extensive cell proliferation, leading to suboptimal culture conditions. Thus, when the blasts were recultured at a lower density or when a lower initial cell concentration was used, a high IgG response was obtained. The synergistic response induced by LPS plus DxS was independent of T cells. Furthermore, no apparent need for phagocytic cells was found. Both the LPS- and the LPS plus DxS-induced activation led to a switch, preferentially to IgG2b and IgG3 secretion. This subclass pattern was not changed when the cultures were lacking functional T cells.

Animals↗
PubMed1981

Visualization of nucleolar substructure in cultured human fibroblasts by magnesium-activated adenosine triphosphatase reaction.

Discrete sites of adenosine triphosphatase (ATPase) activity were demonstrated within the nucleoli of unfixed cultured human fibroblasts (IMR90, VA13, and AG2804 cells) by an adaptation, for electron microscopic cyto-chemistry, of Wachstein and Meisel's lead nitrate method. The majority of nucleoli contained more than one ATPase-positive region, but the total ATPase-positive material appeared to occupy only a minor portion of the nucleolar volume. These regions were roughly spherical with an irregular contour, and at times appeared to be components of perinucleolar chromatin or to be located adjacent to nucleolar interstices. The distribution of these regions within the nucleolus and their segregation by actinomycin D suggested that the ATPase-positive regions correspond to the fibrillar centers, which represent nucleolar organizer regions. The cytochemically demonstrable nucleolar ATPase was strictly dependent on the presence of divalent cations. Optimal reactions was seen at 5 mM Mg2+, but near optimal activity was obtained with lower concentrations of Mg2+ in the presence of Ca2+. Calcium alone and Mn2+ alone produced suboptimal reaction. Studies with different nucleoside phosphates as reaction substrates showed that the enzyme is specific for adenosine derivatives, ATP and dATP being equally good substrates. Guanosine triphosphate, cytidine triphosphate, uridine triphosphate, and d-thymidine triphosphate were ineffective as substrates, as were nucleoside mono- and diphosphates and other phosphate esters tested. It is suggested that the cytochemical ATPase reaction visualized the regions of the nucleolus in which ribosomal DNA of intranucleolar chromatin is undergoing conformational alterations.

Adenosine Triphosphatases↗
PubMed1981

Induction of ovulation in a true hermaphrodite with male phenotype.

Ovulation was induced in a 16-yr-old 46 XX/47 XXY true hermaphrodite with a male phenotype. The presence of testicular tissue was assessed by a normal androgen response to hCG. Administration of FSH and LH for 8 consecutive days, followed by a single dose of hCG, induced a biphasic serum profile of 17 beta-estradiol and progesterone similar to that observed in normal menstrual cycles. In addition, a significant rise in serum testosterone was noticed during the luteal phase. Laparotomy revealed the presence of a uterus, with evidence of endometrial bleeding and absence of a vagina. These results demonstrated that gonadotropins were able to induce follicular maturation, ovulation, and endometrial bleeding in a true hermaphrodite resembling a normal ovulatory cycle. Gonadotropin administration can be used as a diagnostic tool for establishing the presence of ovarian tissue in this gonadal development abnormality.

Adolescent↗
PubMed1980

A primary immune response to dextran B512 is followed by a period of antigen-specific immunosuppression caused by autoanti-idiotypic antibodies.

After a primary immune response to the alpha 1-6 epitope of dextran B512, dextran high responder strains exhibit a specific inability to produce IgM and IgG antibodies against this epitope, although they gave an expected secondary response to horse erythrocytes. Spleen cells from dextran-primed and-suppressed mice responded well to dextran after transfer to lethally irradiated previously untreated mice, indicating that tolerance or exhaustive proliferation of dextran reactive B cells is not responsible. Thymus-dependent dextran-protein conjugates also induced specific suppression. Suppression to both dextran and horse erythrocytes could be passively transferred into untreated recipients with immune serum. However, after absorption with horse erythrocytes and dextran, passive serum transfer only suppressed the response to dextran. It is suggested that the specific immunosuppression was caused by the appearance of autoanti-idiotypic antibodies directed against the immunoglobulin receptors of dextran-reactive B cells.

Animals↗
PubMed1979

Stereotaxic electrode placement in the neonatal rat.

A head holder for stereotaxic electrode placement in the neonatal rat is described. The neonatal head is held in a fixed and reproducible position by means of a mouth bar and a recurved needle hooked into the foramen magnum. With the aid of this instrument, a stereotaxic atlas for the 3-day-old rat has been prepared. The head holder has been used for rats up to 10 days of age and permits electrode placement in the neonatal rat in a manner essentially analogous in ease and precision to that of stereotaxic methods for the adult animal.

Animals↗
PubMed1979

Antigen-induced strain-specific autoantiidiotypic antibodies modulate the immune response to dextran B 512.

Sera from CBA and C57BL mice immunized against dextran B 512 eight or more days earlier contain mainly IgG antibodies that specifically suppress the development of plaque-forming cells against dextran in vitro. Suppression was not caused by antibodies against the alpha 1-6 epitope of dextran to any major extent. Sera from CBA mice (IgCH allotype j) suppressed plaque-forming cells from CBA mice, whereas sera from C57BL mice (allotype b) inhibited plaques from C57BL and CBA/Ig-1b mice. Sera from dextran-tolerant mice or from mice that are genetic unresponders to dextran did not suppress plaque-forming cells. Both thymus-independent and thymus-dependent forms of dextran induced the appearance of these autoantiidiotypic antibodies that can distinguish between anti-alpha 1-6 antibodies produced in mouse strains having different IgCH-locus-determined allotypes.

Animals↗
PubMed1979

The immune response to the alpha 1-6 epitope of dextran is determined by a gene linked to the IgCH locus.

There is a marked strain variability in the immune response against the alpha 1-6 epitope of dextran B512. Responsiveness was independent of the H-2 genotype of the strains but completely determined by the IgCH allotypes of the strains. Thus, IgCHb and IgCHj allotypes characteristic of C57BL and CBA strains, respectively, determined high responsiveness, whereas strains possessing all other allotypes studied were low responders. Backcross analysis indicated that a gene(s) determined responsiveness and that this gene was linked to allotypes of the IgCH locus. F1 hybrids between high and low responder strains always gave a response, but the number of plaque-forming cells was approximately half of that obtained in the high responder strains.

Animals↗
PubMed1979

A thymus-independent IgG response against dextran B512 can be induced in C57BL but not in CBA mice, even though both strains possess a VHdex gene.

CBA and C57BL mice both possess a VHdex gene coding for antibodies against the alpha 1-6 epitope of dextran B512. After immunization with dextran, CBA mice produce IgM plaque-forming cells (PFC) only, which show regular cyclical fluctuations. The second PFC peak disappeared after injection of dextranase, indicating that it is antigen-dependent. The anti-dextran response in C57BL mice is characterized by only one IgM peak, followed 1 day later by an IgG peak that may exceed the IgM response by a factor of 10. The IgG anti-dextran response in C57BL mice was thymus-independent. CBA mice gave an IgG response to the hapten fluorescein isothiocyanate (FITC) after immunization with FITC-dextran, indicating that dextran can function as a carrier for an IgG response in this strain. Attempts to induce IgG PFC against dextran by immunizing CBA mice with thymus-dependent dextran-protein conjugates consistently failed, althouth the conjugates induced IgG fc in C57BL mice. Spleen cells from CBA mice failed to produce IgG antibodies against dextran after transfer into lethally irradiated C57BL mice, whereas the C57BL spleen cells produced IgG PFC after transfer into CBA mice. The lack of IgG synthesis against the alpha 1-6 epitope of dextran in CBA mice appears to be regulated exclusively at the B cell level and is restricted specifically to the VHdex gene product.

Animals↗