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Biomedical subjects

A Fernandez

Publications and source records attributed to A Fernandez.

At least 181 records · Page 10Linked to original sources
PubMed1992

Peritoneal dialysis efficiency in CAPD patients in treatment with rHuEPO.

Possible modifications in peritoneal behaviour that can be caused by erythropoietin (EPO) treatment and/or correction of anemia in the ultrafiltration and peritoneal diffusion were studied in 24 CAPD patients. The evolution of the patients on the medium run was also studied. The dialysate to plasma ratio, the peritoneal clearance and the mass transfer coefficient of urea and creatinine and the ultrafiltration volume were studied, baseline, after reaching the hemoglobin target, and after eight months of treatment. The group of patients developed a decrease in the dialysate to plasma ratio and in the peritoneal clearance of creatinine. After evaluating the effects of the hemoglobin and the hematocrit, we found a decrease in the dialysate to plasma ratio of urea and creatinine, and in the peritoneal clearance of creatinine. A decrease was also found in the mass transfer coefficients of urea and creatinine. An increase in the ultrafiltration was also found in the patients with hemoglobin levels higher or equal to 11 g/dl. Those changes are reversible after turning the hemoglobin levels back to levels lower than 11 g/dl.

Adult↗
PubMed1992

Role of fos-AP-1 binding sequence (FAP) in the induction of c-fos expression by purified C-kinase and in c-fos down-regulation following serum induction.

Microinjection of purified calcium phospholipid-dependent protein kinase (C-kinase) resulted in the rapid and transient induction of c-fos in quiescent rat embryo fibroblats. This C-kinase-induced expression of c-fos was prevented by in vivo competition using co-injection of oligonucleotides corresponding to the sequence of either the serum response element (SRE) or the fos AP-1 binding sequence (FAP) adjacent to SRE. This indicates that both these sequences must be involved in the binding/activation of protein factors required for the induction of c-fos by C-kinase. In contrast, the induction of c-fos by serum or by casein kinase II microinjection, which is also inhibited by injection of SRE oligonucleotides, is only delayed and then markedly prolonged by injecting TRE/FAP sequence, demonstrating that the FAP site plays a prominent role in vivo in the down-regulation of the endogenous c-fos gene expression.

Animals↗
PubMed1992

Resistance of Ha-ras oncogene-induced progressor tumor variants to tumor necrosis factor and interferon-gamma.

To elucidate the mechanisms by which tumor cells escape the immune defenses of the normal host, we have isolated progressor tumor variants from a regressor tumor cell line by transfection with an activated Ha-ras oncogene. We previously found that the progressor phenotype of Ha-ras-induced variants was not due to loss of tumor-specific or major histocompatibility complex antigens. In this study, we investigated whether there is any correlation between in vivo tumor growth and in vitro sensitivity of regressor and progressor tumor cells to tumor necrosis factor (TNF). The regressor UV-2240 tumor cells, which do not grow in normal syngeneic mice, were sensitive to killing by TNF, whereas the Ha-ras oncogene-induced progressor tumor variants of UV-2240, which produce tumors in normal syngeneic hosts, were resistant to killing by TNF. Interferon-gamma (IFN-gamma) enhanced TNF-induced cytotoxicity of the regressor tumor cells, but it had no effect on Ha-ras-induced progressor tumor variants. The resistance of the Ha-ras-induced progressor variants to TNF and IFN-gamma could be attributed to a decrease in the number of TNF receptors on their cell surface. However, there was no correlation between TNF and IFN-gamma sensitivity of tumor cells and sensitivity to killing by activated macrophages, NK or NC cells. These results indicate that in some murine tumor cells, there may be a relationship between in vivo tumor growth and in vitro resistance to cytolysis by TNF and IFN-gamma. Although the response of the Ha-ras-induced progressor variants to TNF and IFN-gamma produced endogenously in immunocompetent mice is unknown, one can infer that some tumors escape the immune defenses of the normal host by becoming resistant to certain cytokines produced by the immune system.

Animals↗
PubMed1991

Cyclin A is required for the onset of DNA replication in mammalian fibroblasts.

Cyclin A protein is synthesized and localized into the nucleus at the onset of S phase in nontransformed mammalian fibroblasts. Inhibition of cyclin A synthesis or activity through microinjection of plasmids encoding antisense cyclin A cDNA or affinity-purified anti-cyclin A antibodies during G1 phase was shown to abolish the nuclear staining for cyclin A in plasmid-injected cells, and both procedures led to inhibition of DNA synthesis. No similar effect was observed with injection of other antisense vectors including antisense cyclin B, and reinjection of purified human cyclin A protein into cyclin A antisense-injected cells effectively relieved this inhibition of DNA synthesis. Taken together, these data suggest that cyclin A plays a major role in the control of DNA replication in mammalian cells.

Animals↗
PubMed1991

Inhibition of cAMP-dependent protein kinase plays a key role in the induction of mitosis and nuclear envelope breakdown in mammalian cells.

Inhibiting cAMP-dependent protein kinase (A-kinase) in mammalian fibroblasts through microinjection of a modified specific inhibitor peptide, PKi(m) or the purified inhibitor protein, PKI, resulted in rapid and pronounced chromatin condensation at all phases of the cell cycle. Together with these changes in chromatin, a marked reorganization of microtubule network occurred, accompanied in G2 cells by extensive alterations in cell shape which have many similarities to the premitotic phenotype previously observed after activation of p34cdc2 kinase, including the lack of spindle formation and the persistence of a nuclear envelope. In order to examine whether A-kinase inhibition and p34cdc2 kinase form part of the same or different inductive pathways, PKI and p34cdc2 kinase were injected together. Co-injection of both components resulted in nuclear envelope disassembly, an event not observed with injection of either component alone. This result implies that p34cdc2 and A-kinase inhibition have complementary and additive effects on the process of nuclear envelope breakdown in living fibroblasts, a conclusion further supported by our observation of a pronounced dephosphorylation of lamins A and C in cells after injection of PKi(m). Taken together, these data suggest that down-regulation of A-kinase is a distinct and essential event in the induction of mammalian cell mitosis which co-operates with the p34cdc2 pathway.

Animals↗
PubMed1991

Casein kinase II induces c-fos expression via the serum response element pathway and p67SRF phosphorylation in living fibroblasts.

Elevation of intracellular casein kinase II (CKII) levels through microinjection of purified CKII results in the rapid and transient induction of c-fos in quiescent rat embryo fibroblasts, and activation of quiescent cells by serum is accompanied by the nuclear relocation of endogenous CKII. The induction of c-fos by CKII is inhibited by coinjection of oligonucleotides corresponding to the sequence of the serum response element (SRE) present in the c-fos promoter, indicating that competitive displacement of positive factors from the endogenous c-fos SRE prevents c-fos induction by CKII. Furthermore, the expression of c-fos induced by either CKII injection or serum activation is also inhibited by microinjection of antibodies against the 67 kDa serum response factor (p67SRF) indicating the absolute requirement of p67SRF in this process. Finally, we show the specific phosphorylation of p67SRF in vivo following microinjection of CKII into quiescent cells. Together, these data strongly support that CKII induces c-fos expression through binding/activation of the phosphorylated p67SRF at the SRE sequence.

Animals↗
PubMed1991

Effective intracellular inhibition of the cAMP-dependent protein kinase by microinjection of a modified form of the specific inhibitor peptide PKi in living fibroblasts.

In order to obtain a peptide retaining its biological activity following microinjection into living cells, we have modified a synthetic peptide [PKi(m)(6-24)], derived from the specific inhibitor protein of the cAMP-dependent protein kinase (A-kinase) in two ways: (1) substitution of the arginine at position 18 for a D-arginine; (2) blockade of the side chain on the C-terminal aspartic acid by a cyclohexyl ester group. In an in vitro assay, PKi(m) has retained a specific inhibitory activity against A-kinase as assessed against six other kinases, with similar efficiency to that of the unmodified PKi(5-24) peptide. Microinjection of PKi(m) into living fibroblasts reveals its capacity to prevent the changes in cell morphology and cytoskeleton induced by drugs which activate endogenous A-kinase, whereas the original PKi peptide failed to do so. This inhibition of A-kinase in vivo by PKi(m) lasts between 4 and 6 h after injection. In light of its effective half-life, this modified peptide opens a route for the use of biologically active peptides in vivo, an approach which has been hampered until now by the exceedingly short half-life of peptides inside living cells. By providing a direct means of inhibiting A-kinase activity for sufficiently long periods to observe effects on cellular functions in living cells, PKi(m) represents a powerful tool in studying the potential role of cAMP-dependent phosphorylation in vivo.

Amino Acid Sequence↗
PubMed1991

Effect of homotaurine in experimental analgesia tests.

1. The possible antinociceptive action of GABA A receptor agonist homotaurine, has been studied through a battery of chemical (acetic acid) and thermal (hot plate, tail flick and tail immersion) tests in rats and mice. 2. The aminoacid was used at the following doses 22.25; 55.62 and 111.24 mg/kg i.p. and 50-100 micrograms i.c.v.; and measurements were made at the time of and at 5, 15 and 30 min after drug administration. 3. Homotaurine exhibited a significantly antinociceptive effect in all the above mentioned test except hot plate and when administered i.c.v. in the tail flick test. 4. The antinociceptive effect in the chemical test was dose and time dependent. 5. In the tail immersion test, latency time for withdrawal of the tail was significantly increased with the dose of 55.62 mg/kg at 15 min and 111.24 mg/kg at 30 min. 6. In the tail flick test the antinociceptive effect was dose dependent at 15 and 30 min. 7. From the above results the implication of peripheral and spinal mechanisms in the antinociceptive effect of homotaurine may be concluded.

Analgesics↗
PubMed1991

p67SRF is a constitutive nuclear protein implicated in the modulation of genes required throughout the G1 period.

Indirect immunofluorescence analysis, using antibodies directed against peptide sequences outside the DNA-binding domain of the 67-kDa serum response factor (p67SRF), revealed a punctuated nuclear staining, constant throughout the cell cycle and in all different cell lines tested. p67SRF was also tightly associated with chromatin through all stages of mitosis. Inhibition of p67SRF activity in vivo, through microinjection of anti-p67SRF antibodies, specifically suppressed DNA synthesis induced after serum addition or ras microinjection, suggesting that these antibodies were effective in preventing expression of serum response element (SRE)-regulated genes. A similar inhibition was also obtained in cells injected with oligonucleotides corresponding to the DNA binding sequence for p67SRF protein, SRE. Moreover, this inhibition of DNA synthesis by anti-p67SRF or SRE injection was still observed in cells injected during late G1, well after c-fos induction. These data imply that genes regulated by p67SRF are continuously involved in the proliferation pathway throughout G1 and that p67SRF forms an integral component of mammalian cell transcriptional control.

Amino Acid Sequence↗
PubMed1991

Immunohistological diagnosis of rabbit haemorrhagic disease in experimentally infected rabbits in Spain.

The immunoreactivity of routinely processed liver and lung tissue samples obtained from rabbits inoculated with tissue explants from naturally infected animals when antisera directed against parvovirus from different species (canine, feline and porcine) as well as a RHD virus antiserum were employed has been tested by different immunoperoxidase methods. Cross-reactivity between RHD-virus antigens and parvovirus antigens was present. Best results were obtained with RHD and canine parvovirus antisera with the ABC method. The immunoreactivity in the liver was found in hepatocytes, Kupffer and bile duct cells. In the lung, it was exclusively observed in intravascular macrophages.

Animals↗
PubMed1991

Effects of some inhibitors of arachidonic acid metabolism in rat uterus in vitro.

The effect of four eicosanoid synthesis inhibitors (ESIs): mepacrine (6 x 10(-6) to 10(-4) M), nordihydroguaiaretic acid (NDHGA, 10(-6) to 10(-5) M), indomethacin (2 x 10(-6) and 2 x 10(-5) M) and imidazole (10(-5) and 10(-4) M), were studied on contractions induced by cumulative doses (4 and 20 mU/ml) of oxytocin (OT) on the uterus of rats both in natural estrus and ovariectomized. ESIs were also assayed on contractions induced by carbachol (10(-4) M) and KCl (60 mM) in rat uterus under natural estrus, and OT (10 mU/ml)-induced contractions in rat uterus incubated in calcium-free EDTA treated medium. Mepacrine, NDHGA and indomethacin, but not imidazol, inhibited in a dose-dependent way contractions induced by OT in the uterus. The effect was higher in ovariectomized than in natural estrus rats. Mepacrine and NDHGA, but not indomethacin or imidazole, inhibited contractions induced by carbachol and relaxed tonic contractions to KCl (60 mM). Mepacrine, NDHG and indomethacin also inhibited tonic contractions by OT in calcium-free EDTA treated medium. Our results suggest that mepacrine, NDHGA and indomethacin, independently of inhibition of eicosanoids synthesis, reduce the entry of extracellular calcium and/or the release of intracellular calcium.

Animals↗
PubMed1991

Exchange transfusions in neonatal sepsis.

Between October, 1987 and October, 1988, 53 neonates with severe or unresponsive sepsis were subjected to therapeutic exchange transfusions (ET) using 170 ml/kg of citrated blood less than 24 hours old. The procedure was repeated up to a maximum of 4 times. The success of therapy was adjudged by resolution of sclerema and/or improvement in clinical features. There were 32 low birth-weight (LBW) and 21 non-LBW infants and 51/53 subjects had sclerema. The mean time for recovery following ET was 19.6 +/- 12.4 h (range: 1-48 h). The overall survival was 77.4% and the survival rates for LBW and non-LBW infants were 73.6 and 68.2%, respectively, however, the difference was not statistically significant. No significant or fatal complications occurred during ET. The effects of other associated problems on outcome studied by multiple regression analysis showed that neurologic problems were associated with a poor chance for survival despite ET. Exchange transfusion may thus be an effective and safe therapeutic modality for severe neonatal sepsis.

Birth Weight↗
PubMed1990

Nuclear localization of c-Fos, but not v-Fos proteins, is controlled by extracellular signals.

We report here that transport of the protein product of the c-fos proto-oncogene from the cytoplasm, where it is synthesized, into the nucleus, where it operates as part of the AP-1 transcription complex, is not spontaneous but depends on the continuous stimulation of cells by serum factors. A labile protein inhibitor of transport, the effect of which is reversed by cAMP, is responsible for retention of c-Fos protein within the cytoplasm of serum-starved fibroblasts. In contrast, v-Fos proteins transduced by the murine retroviruses FBJ and FBR, which remain nuclear in the absence of serum, evade the translocation control, which therefore appears to contribute to their tumorigenic potential.

Animals↗
PubMed1990

Demonstration in living cells of an intragenic negative regulatory element within the rodent c-fos gene.

We studied c-fos gene expression in rat fibroblasts by microinjection of regulatory DNA sequences, such as the serum response element (SRE) present in c-fos promotor, in order to compete directly with such sequences for binding of putative regulatory factors. We show that an additional fos intragenic regulatory element (FIRE) is located at the end of exon 1. When coinjected with an SRE oligonucleotide, it induced c-fos expression in quiescent cells, whereas injection of SRE sequence alone failed to do so. Moreover, injection in quiescent cells of an SRE oligonucleotide together with a p-fos-lacZ construct containing the c-fos SRE as well as an in-frame insertion of FIRE resulted in a block to beta-galactosidase expression that can be relieved by coinjection of the FIRE sequence.

Animals↗