Search PubMed⌕ Search

Biomedical subjects

F Montiel

Publications and source records attributed to F Montiel.

At least 19 recordsLinked to original sources
PubMed1995

Expression of a 2.8-kb PDGF-B/c-sis transcript and synthesis of PDGF-like protein by human lung fibroblasts.

The replication of fibroblasts is thought to be controlled by exogenous growth factors mainly secreted by macrophages and epithelial cells. However, under standard culture conditions, lung fibroblasts are able to produce several growth factors, suggesting an autocrine pathway of proliferation. In this work, we examined the expression of platelet-derived growth factor (PDGF-A) and PDGF-B-messenger RNA (mRNAs) by fibroblasts derived from four human adult normal lungs and from two fibrotic lungs. Northern blot analysis showed that both normal and idiopathic pulmonary fibrosis (IPF)-derived fibroblasts expressed a 2.8 PDGF-B/c-sis mRNA. This transcript was also observed as a minor form in human osteosarcoma cell line, used as control, which predominantly expressed a 4.0-kb PDGF-B mRNA. In two fibroblast cell lines, one fibrotic and one normal, the 4.0-kb transcript was also observed but was always weaker than the 2.8-kb mRNA. PDGF-A mRNA was not detected. By immunofluorescence, lung fibroblasts exhibited intracytoplasmic PDGF-like protein. Likewise, conditioned media from normal and IPF lung fibroblasts stimulated 3H-thymidine incorporation in BALB/c-3T3 cells that was significantly inhibited by anti-PDGF antibody. These results show that in vitro, some human lung fibroblasts express PDGF-B/c-sis mRNA, mainly an alternate 2.8-kb transcript, and produce PDGF-like protein.

Blotting, Northern↗
PubMed1995

[Molecular study of 6 episodes of nosocomial infections produced by methicillin resistant Staphylococcus aureus].

A critical step in any epidemiologic research concerning nosocomial infections is the precise identification of the responsible pathogen. The present work utilized a molecular approach -plasmids identification, restriction length polymorphism DNA analysis, and random amplified polymorphic DNA- for the characterization of 6 nosocomial outbreaks due to 52 strains of methicillin-resistant Staphylococcus aureus (MRSA). In these episodes, the clinic-epidemiologic and phenotypic analysis (antibiotype) pointed to a nosocomial infection. Through molecular analysis it was possible to establish, in a very precise way, clonality due to MRSA strains in 2 of the studied outbreaks; the same type of analysis allowed to eliminate a MRSA clonal origin in the remainder 4 episodes. The antibiogram was not an useful analytic tool due to its poor discriminatory power. Also, through a PCR procedure, it was possible to identify the presence of the gen mecA in every of the 52 MRSA strains studied.

Base Sequence↗
PubMed1995

[Infection and reactive arthritis: clinico-bacteriological correlation in seronegative arthropathies].

The aim of this study was to search infections that trigger reactive arthritis. Eighty-six patients with seronegative arthritis (SNA) were studied; 32 had reactive arthritis, 21 ankylosing spondylitis, 7 psoriatic arthritis and 26 undifferentiated seronegative oligoarthritis. As controls, 70 patients with connective tissue diseases (CTD) and 55 healthy volunteers (HV) were studied. Serological evidence for infection with Chlamydia trachomatis was studied with micro immunofluorescence, looking for L2 and BED serotypes and serological evidence for Yersinia infection, using a commercial kit. Stool cultures were done in seven patients with recent diarrhea, and endourethral or endocervical cultures in 35 individuals. Serotypes L2 or BED were positive in 23 of 83 patients with SNA, 3 of 39 patients with CTD and 4 of 55 HV (p < 0.03). IgG class antibodies against L2 were detected in 17% of SNA patients, 2.6% of CTD patients and 5.4% of HV (p < 0.05). IgM class antibodies were detected in 6 SNA patients, 0 CTD patients and 2 HV (NS). Twelve of 35 cultures were positive for Chlamydia. As a whole 30% of SNA patients has serological or bacteriological evidence for Chlamydia infection. Serology for Yersinia was positive in 39 of 81 SNA patients, 1 of 54 CTD patients and 3 of 51 HV (p < 0.01). Rates of infections were similar among male, female, HLA B27 positive and HLA negative subjects. It is concluded that SNA patients have a high prevalence of infections by Chlamydia trachomatis or Yersinia enterocolitica.

Adolescent↗
PubMed1993

Enzymatic DNA amplification (PCR) in the diagnosis of extrapulmonary Mycobacterium tuberculosis infection.

A polymerase chain reaction able to amplify Mycobacterium tuberculosis DNA from clinical samples of extra-pulmonary origin is described. The PCR amplified a 294 base pair DNA fragment spanning positions 5'-782 to 3'-1075 of the 65 kDa M. tuberculosis antigen gene. The procedure enables amplification of target DNA at quantities as low as 1 pg of purified material and less than 1000 mycobacteria present in clinical samples. The reaction amplifies M. tuberculosis DNA as well as Mycobacterium bovis BCG DNA. In 34 extra-pulmonary clinical samples studied, 18 rendered positive results and two false-negative results; compared to classical diagnostic procedures, the sensitivity was 90% and specificity 100%. The PCR approach to diagnosis of tuberculosis of extra-pulmonary origin is a valid diagnostic alternative to classical procedures.

Base Sequence↗
PubMed1993

[Amplification of 2 different gene segments of Mycobacterium tuberculosis and its usefulness in the diagnosis of tuberculosis].

The infection caused by Mycobacterium tuberculosis is highly prevalent in our country and is considered an emergent pathology in developed countries. The amplification of specific gene segments with diagnostics purposes is an alternative to identify fastidious and slow growing infective agents, being Mycobacterium tuberculosis one of them. Two polymerase chain reactions (PCR) directed to the amplification of a 294bp gene segment encoding a portion of a 65KD heat shock protein and 317 bp gene segment of a repetitive DNA segment (IS 6110) of Mycobacterium tuberculosis, have a sensibility of 80 to 91.3% and a specificity of 83.9 to 100% when used in the identification of Mycobacterium tuberculosis in 2 group of clinical samples, both compared to Koch's culture and or Ziehl-Neelsen stain. The diagnostic procedure is particularly useful in diagnosis of tuberculosis of extrapulmonary origin.

Base Sequence↗
PubMed1993

Microbial invasion of the amniotic cavity during term labor. Prevalence and clinical significance.

The purpose of this study was to determine the prevalence and clinical significance of microbial invasion of the amniotic cavity during spontaneous parturition at term. Amniotic fluid was retrieved by transabdominal amniocentesis from 90 women in spontaneous term labor with intact membranes. Fluid was cultured for aerobic and anaerobic bacteria, including Mycoplasma. The prevalence of positive amniotic fluid cultures was 18.8% (17/90). The most common microbial isolates were Ureaplasma urealyticum, Streptococcus agalactiae, Lactobacillus species and Mycoplasma hominis. Clinical signs of chorioamnionitis were present in three patients, and only one of them had a positive amniotic fluid culture. Five patients (5.5%) had puerperal endometritis; three of them had an amniotic fluid culture positive for microorganisms. All neonates were free of clinical signs of infection. The data indicate that microbial invasion of the amniotic cavity occurs frequently during spontaneous labor at term, and it may be both the cause and the consequence of labor.

Adolescent↗
PubMed1992

Infection and labor. VII. Microbial invasion of the amniotic cavity in spontaneous rupture of membranes at term.

OBJECTIVE: The purpose of this study was to determine the frequency, microbiologic characteristics, and clinical significance of microbial invasion of the amniotic cavity in women with premature rupture of membranes at term. STUDY DESIGN: Amniocentesis was performed in 32 women with term premature rupture of membranes and amniotic fluid cultured for aerobic and anaerobic bacteria and Mycoplasmas. RESULTS: The prevalence of positive amniotic fluid cultures was 34.3% (11/32). The most common isolates were Ureaplasma urealyticum, Peptostreptococcus sp., Lactobacillus sp., Bacteroides fragilis, and Fusobacterium sp. Clinical chorioamnionitis occurred only in one patient with a positive amniotic fluid culture. Her neonate had ophthalmitis. Three patients (9.4%) had endometritis. Among women who were delivered vaginally, those with a positive amniotic fluid culture had a significantly higher rate of endometritis than those with a negative culture (33% [3/9] vs 0% [0/20], respectively, p = 0.023). CONCLUSIONS: These data indicate that microbial invasion of the amniotic cavity occurs in approximately one third of patients with preterm premature rupture of membranes. Microbial invasion of the amniotic cavity is a risk factor for endometritis in women with term premature rupture of membranes.

Amnion↗
PubMed1992

[Cervical and abdominal microbiology in infertile patients].

The microbiology of twenty-nine asymptomatic infertile women was evaluated prospectively. Samples were taken from the cervix and the endosalpinx during laparoscopy. Cultures for aerobes, anaerobes, Neisseria gonorrhoeae, Mycoplasma, Ureaplasma urealyticum and Chlamydia trachomatis were performed. No association was found between the presence of germs in the abdomen or cervix and tubal abnormalities. History of previous IUD use was associated with tubal disease.

Abdomen↗
PubMed1989

Presence of insulin receptors in cultured glial C6 cells. Regulation by butyrate.

The presence of insulin receptor and its regulation by butyrate and other short-chain fatty acids was studied in C6 cells, a rat glioma cell line. Intact C6 cells bind 125I-insulin in a rapid, reversible and specific manner. Scatchard analysis of the binding data gives typical curvilinear plots with apparent affinities of approx. 6 nM and 70 nM for the low-affinity (approx. 90% of total) and high-affinity (approx. 10% of total) sites respectively. Incubation with butyrate results in a time- and dose-dependent decrease of insulin binding to C6 cells. A maximal effect was found with 2 mM-butyrate that decreased the receptor by 40-70% after 48 h. Butyrate decreased numbers of receptors of both classes, but did not significantly alter receptor affinity. Other short-chain fatty acids, as well as keto acids, had a similar effect, but with a lower potency. Cycloheximide caused an accumulation of insulin receptors at the cell surface, since insulin binding increased and receptor affinity did not change after incubation with the inhibitor. Simultaneous addition of butyrate and cycloheximide abolished the loss of receptors produced by the fatty acid. In cells preincubated with butyrate, cycloheximide also produced a large increase in receptor numbers, showing that in the absence of new receptor synthesis a large pool of receptors re-appears at the surface of butyrate-treated cells.

Animals↗
PubMed1989

Effects of cyclic AMP elevation on the levels of insulin receptors in glial C6 cells.

The regulation of the insulin receptor by cAMP has been examined in glial C6 cells. Incubation for 48 h with dibutyryl cyclic AMP produced a dose-dependent inhibition of 125I-insulin binding to the cells. Other agents that elevate intracellular cAMP levels such as forskolin and cholera toxin mimicked the effect of this cyclic AMP analog. With all compounds the maximal decrease of binding was found between 24 and 48 h and normally varied between 40 and 60%. Forskolin, cholera toxin and dibutyryl cyclic AMP also affected C6 cell proliferation, and the dose-response for decreasing the receptor was very similar to that observed for the inhibition of cell growth, suggesting a relationship between both phenomena. Scatchard analysis showed that cAMP did not produce major changes in the affinity of the receptor for insulin, but rather decreased receptor number. An accumulation of receptors at the cell surface was observed in the absence of de novo protein synthesis, since cycloheximide caused a significant increase in insulin binding to the cells. This inhibitor almost totally blocked the cAMP effect both when added simultaneously to the cells with the agents which increase cAMP and when added to cells pre-treated for 48 h with the same compounds.

Animals↗
PubMed1988

In vitro susceptibility to 10 antibiotics of methicillin-resistant (MRSA) Staphylococcus aureus in Chile.

The in vitro activity of 10 antibiotics was determined for 231 strains of methicillin resistant (MRSA) Staphylococcus aureus. Oxacillin was a very good antibiotic to determine methicillin-resistance. Its agreement with methicillin-resistance was in all the strains tested. On the contrary, the correlation with nafcillin was established only in 95% of the strains tested. Cloxacillin and flucloxacillin are not good methicillin-resistance indicators. The strains tested against macrolides, such as erythromycin, and lincosamides, such as lincomycin and clindamycin presented a susceptibility of 68, 78, and 80%, respectively. All tested strains were susceptible to vancomycin.

Anti-Bacterial Agents↗
PubMed1988

Short chain fatty acids modulate nuclear receptor and extranuclear L-triiodothyronine levels in glial C6 cells by different mechanisms.

After incubation with [125]T3, the amount of radioactivity associated with the nuclear receptor and extranuclear compartment increases in glial C6 cells previously exposed to millimolar concentrations of butyrate. These actions of the fatty acid are accompanied by an inhibition of cell division, as shown by the decrease in [3H]thymidine incorporation or total DNA content per culture. Isobutyrate produced a similar effect at concentrations higher than 2 mM, whereas between 0.5-2 mM it increased the receptor content without affecting either extra-nuclear hormone or DNA. For both fatty acids there was a close parallelism between the dose-response curve for the inhibition of turnover of [3H]acetate from the histones and the increase in receptor levels. In contrast, a different dose dependence was found for the increase in extranuclear T3 levels, which suggests that the latter is caused by a mechanism other than histone acetylation. The increase in extranuclear T3 levels correlated better with the decrease in DNA and the accumulation of the chromosomal protein H10, which is thought to be related to the inhibition of cell proliferation. This suggests a relationship between the increase in extranuclear T3 and the inhibition of DNA synthesis. However, other agents, such as glucocorticoids or cAMP, which also inhibit C6 cell proliferation, were ineffective in increasing not only the receptor but also the extranuclear hormone. These findings show that the effect of short chain fatty acids on the receptor is not a consequence of the inhibition of cell replication, and that this inhibition could be related to, but is not sufficient per se for causing the increase in extranuclear T3.

Acetates↗
PubMed1987

Down-regulation of thyroid hormone nuclear receptor levels by L-triiodothyronine in cultured glial C6 cells.

L-Triiodothyronine (T3) produced a time- and dose-dependent depletion of nuclear thyroid hormone receptor levels in C6 cells, a rat glioma cell line. Receptor number diminished by 30-40% after a 48 h incubation with concentrations of T3 that saturate the nuclear receptor. The nuclear binding curve obtained in cells incubated for 48 h with T3 was shifted leftward of the curve obtained after a 3 h incubation, which indicates an apparent increase in receptor affinity after long-term incubation with T3. However, this change probably represents a further equilibration of the hormone, since the dissociation rate from the nuclei was similar in C6 cells after long- and short-term incubation with T3. The effect of T3 was further demonstrated in C6 cells incubated with short-chain fatty acids. Butyrate and isobutyrate increased receptor levels, and T3 partially decreased the response to these compounds. These findings suggest the existence of a desensitization process by which C6 glial cells would be protected against an excess of thyroid hormone.

Animals↗
PubMed1987

Effects of iopanoic acid on thyroid hormone receptor, growth hormone production, and triiodothyronine generation from thyroxine in pituitary GH1 cells.

We have studied the effect of iopanoic acid (IOP), a radiographic contrast agent which inhibits T4 to T3 conversion, on thyroid hormone nuclear receptors, GH response to T4 and T3, and T4 5'-monodeiodination in GH1 cells, a rat pituitary cell line. IOP at concentrations higher than 10 microM inhibits iodothyronine binding to the nuclear receptor without changing the dissociation constant (Kd) (0.1 nM for T3 and 1 nM for T4), and reduces the GH response to 50 nM T4, 5 nM T3, or the combined effect of T4 and glucocorticoids. These results could be explained by an inhibition of protein synthesis which was reduced by more than 50% by 50 microM IOP. By contrast, nontoxic concentrations of IOP did not change the GH response to different doses of T4 ranging from 1 nM to 50 nM. We also examined T3 generation from T4 and found that the intracellular T3 levels of cells incubated with 50 nM T4 were almost as high as those of cells incubated with 5 nM T3 which induces a full GH response. Intracellular T3 levels were markedly reduced in the cells incubated with T4 and IOP, but GH production was not reduced despite these differences in T3 levels. Additionally, more than 40% of the nuclear receptor was occupied by T3 in cells incubated with T4, whereas more than 90% was occupied by T4 in cells receiving the same amount of T4 with 5 microM IOP. Our results suggest that the effect of T4 on GH production by GH1 cells could be attributed to an important extent to the T3 generated from it, whereas when T4 monodeiodination is strongly inhibited, most of the biological activity is a result of intrinsic T4 activity.

Animals↗