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Biomedical subjects

C Torres

Publications and source records attributed to C Torres.

At least 55 records · Page 3Linked to original sources
PubMed2000

The spatial distribution of behavior under varying frequencies of temporally scheduled water delivery.

Two studies evaluated the effects of response-independent water deliveries on the location (on the floor of the experimental chamber) and position (height) of rats' behavior. In both experiments, fixed-time schedules delivered water in two dispensers that were located at opposite ends of the chamber. In Experiment 1, the two schedules provided complementary frequencies of water deliveries while the overall number of deliveries stayed constant. In Experiment 2, one of the schedules delivered water twice as frequently as the other; this proportion was kept constant while the overall density of water deliveries changed systematically. In both experiments, a single position (height) of behavior was dominant. Also, the percentage of time allocated to each dispenser was roughly proportional to the percentage of water deliveries associated with the dispensers. These data and additional considerations support the importance of examining the spatial properties and patterning of behavior.

Animals↗
PubMed2000

The role of peritoneal dialysis catheter configuration in preventing catheter tip migration.

Migration of the peritoneal dialysis (PD) catheter from the pelvis to the upper abdomen frequently results in peritoneal dialysis failure and removal of the catheter. Previous studies compared PD catheter survival in various catheter configurations. These studies included single-cuff and double-cuff, straight-end and curled-end catheters, and showed an incidence of catheter migration ranging from 5%-35% depending on the catheter type. Recent studies demonstrated that the double-cuff, Swan-neck, curled-end configuration is associated with a considerably lower incidence of migration. Most of these studies, however, had a small patient sample or no control group, or they compared nonequivalent catheters (for example, Swan-neck, curled-end versus straight, non-curled-end). Over a six-year period, we examined two similar double-cuff, curled-end catheters: Group I catheters had a straight segment between the two cuffs, and Group II catheters had a 60 degrees Swan-neck bend between the two cuffs (Quinton Instrument Co., Bothell, WA, U.S.A.). The two catheters were identical, except for the presence or absence of the Swan-neck bend. All catheters were placed by the closed laparoscopic technique. In the two groups of patients in whom the catheters were implanted, no statistically significant difference was observed in primary disease, age, sex, race, weight, prior abdominal surgery, or duration of dialysis before catheter migration. In group I, 33 of the 219 patients developed catheter migration (15%); in group II, 2 patients of 243 patients developed catheter migration (less than 1%, p = 0.002). In conclusion, the Swan-neck configuration presents an independent factor in preventing PD catheter migration. Review of previous studies and the data from our study, show that double-cuff, curled-end, Swan-neck PD catheters are superior to other catheters in regard to prevention of catheter migration and should be the catheter of choice in PD patients.

Adolescent↗
PubMed2000

Preoperative vancomycin prophylaxis for newly placed peritoneal dialysis catheters prevents postoperative peritonitis.

The role of vancomycin and other antibiotics in treatment of acute peritonitis in peritoneal dialysis patients is well established. However, the role of preoperative vancomycin or cephalosporins in preventing early infection in newly placed peritoneal dialysis catheters remains controversial. We performed a prospective randomized study to examine the role of vancomycin or cefazolin prophylaxis in decreasing the incidence of postoperative peritonitis. Over 8-year period, 265 patients undergoing 305 permanent peritoneal catheter placement procedures were randomized into three groups. Group I (103 procedures) received a single intravenous (i.v.) dose of 1000 mg vancomycin 12 hours before the peritoneal catheter placement procedure. Group II (102 procedures) received a single i.v. dose of 1000 mg of Ancef (cefazolin) 3 hours before the procedure. Group III (100 procedures) received no antibiotics preoperatively for a least one week before the procedure. Patients were monitored for peritonitis during the following 14 days. Peritonitis developed in 1 patient (1%) in Group I (vancomycin group) compared to 12 patients (12%) in Group III (control group), p = 0.002, and in 9 patients (9%) in Group II (cefazolin group) compared to Group III, p = 0.68. We conclude that the use of preoperative single-dose i.v. vancomycin prophylaxis for permanent peritoneal dialysis catheter placement reduces the risk of postoperative peritonitis. Cefazolin did not achieve a statistically significant difference from the control group and may not provide adequate prophylaxis.

Adolescent↗
PubMed2000

Pulse oral versus pulse intraperitoneal calcitriol: a comparison of efficacy in the treatment of hyperparathyroidism and renal osteodystrophy in peritoneal dialysis patients.

Controversy exists among various studies in regard to the efficacy of oral (p.o.) versus parenteral calcitriol. Some studies suggest that intravenous (i.v.) calcitriol is superior to p.o. calcitriol for treating renal osteodystrophy in hemodialysis patients; others suggest that these routes of administration are equivalent. To our knowledge, no large, prospective, randomized study compares intraperitoneal (i.p.) to p.o. calcitriol in adult peritoneal dialysis patients. We conducted a prospective randomized study in 76 patients (38 on i.p. calcitriol and 38 on p.o. calcitriol), whom we followed for 48 months. Of the 76 patients, 34 (18 in the i.p. group and 16 in the p.o. group) completed the 48-month study period. Calcitriol dosing was similar in both groups (3-6 micrograms per week in three divided doses). Dose adjustments were made depending on levels of parathyroid hormone (PTH), serum calcium, phosphorus, and calcitriol. No significant difference was seen between the groups in regard to age, sex, race, body mass index, dialysis duration, or cause of ESRD. Neither was any difference in the incidence of peritonitis seen between the groups. In the first 3-6 months, PTH decreased equivalently in both groups. The PTH level remained suppressed in the i.p. group throughout the remainder of the study, but, in the p.o. group, PTH returned to its pretreatment level after 3-6 months. Mean serum calcium was not different in the two groups. In the p.o. group, a considerably higher mean follow-up phosphorus level (6.8 +/- 2.3 mg/dL versus 4.7 +/- 1.4 mg/dL, p = 0.008), PTH level (384 +/- 146 pg/mL versus 162 +/- 64 pg/mL; p = 0.005), and alkaline phosphatase level (178 +/- 37 IU/L versus 72 +/- 21 IU/L, p = 0.02) were seen as compared to the i.p. group. In the i.p. group, resolution of osteodystrophy occurred in all patients at the end of the study; in the p.o. group, 5 patients maintained or developed osteodystrophy by the end of the study (p = 0.016). We conclude that i.p. calcitriol is more effective than pulse p.o. calcitriol in lowering PTH and alkaline phosphatase levels and in resolving renal osteodystrophy, and that i.p. calcitriol is associated with a lower incidence of hyperphosphatemia and elevated Ca x PO4 byproduct.

Administration, Oral↗
PubMed1999

Characterization of a new ATP-binding cassette transporter in Trypanosoma cruzi associated to a L1Tc retrotransposon.

We have characterized the tcpgp1-like gene of Trypanosoma cruzi, a new ATP-binding cassette (ABC) transporter. tcpgp1 codes for a 1035 amino acid protein with a considerable homology to LtpgpA of Leishmania. Tcpgp1 lacks the conserved sequences corresponding to the second nucleotide-binding domain of other ABC transporters due to the insertion of the L1Tc non-LTR retrotransposon.

ATP-Binding Cassette Transporters↗
PubMed1999

Interferon-gamma induces proliferation but not apoptosis in murine astrocytes through the differential expression of the myc proto-oncogene family.

Interferon-gamma (IFN-gamma) is a cytokine mainly secreted by activated T-lymphocytes. Treatment of mouse astrocytes in vitro with IFN-gamma augmented the basal expression of the primary response proto-oncogenes c-myc and L-myc as detected by Northern blotting. Such inductions were maximal at doses of 10 U/ml and after 60 min of treatment. Astrocytes fully differentiated in vitro do not express N-myc mRNA nor are induced to express it by exposure to IFN-gamma. As demonstrated by flow cytometry, the common protein product of the myc family was present in the nucleus of the cells. The specificity of IFN-gamma induction was demonstrated when antibodies against IFN-gamma completely suppressed the overinduction of these mRNAs. No apoptotic death can be detected in astrocytes treated with IFN-gamma at doses that induce c-myc expression. Conversely, treatment with a dose of 10 U/ml induced cells proliferation in astrocytic cells as measured by (3)H-thymidine incorporation.

Animals↗
PubMed1999

Flow stimulates nitric oxide release in guinea pig heart: role of stretch-activated ion channels.

Blood flow regulates vessel tone triggering the release of nitric oxide; however, the mechanism involved in this phenomenon is unknown. We investigated whether coronary flow induces nitric oxide release in the isolated perfused guinea pig heart and the role of the stretch-activated ion channels in the effect of flow. We used gadolinium (3 microM) in order to block these channels, and estimated nitric oxide release by an oxyhemoglobin method. The results have shown a flow-dependent stimulation of nitric oxide release (fivefold increase at perfusion flow of 25 ml/min). Gadolinium inhibited this effect in a dose-dependent fashion. Acetylcholine was able to stimulate nitric oxide release in presence of gadolinium. We concluded that coronary flow stimulates nitric oxide release in the guinea pig heart. Stretch-activated ion channels mediate this effect. Acetylcholine and flow stimulate nitric oxide release by different mechanisms of action.

Acetylcholine↗
PubMed1999

[Retrospective study of the incidence of hepatitis G virus infection in transfused patients].

BACKGROUND: Recently the parenteral transmission of hepatitis G virus (HGV) has been shown. The aim of the study was to investigate the incidence of post-transfusion HGV. PATIENTS AND METHODS: HGV (RNA-HGV and anti-HGVE2) were retrospectively studied in 140 transfused patients. RESULTS: 12 (8.6%) were infected after transfusion: 9 of 12 (75%) the RNA-HGV remained detectable after 6 months and 3 (25%) seroconverted to anti-HGVE2. No patient had post-transfusional hepatitis criteria. In 5 (42%) the transaminases levels were slightly increased. The clinical evolution was favourable. No significant differences were found between patients with or without HGV infection. CONCLUSIONS: HGV is an agent associated with transfusion but it carries a low pathogenic capability.

Adolescent↗
PubMed1999

The prognostic significance of lymph node micrometastasis in patients with esophageal carcinoma.

BACKGROUND: Lymph node metastasis is a well known feature of poor prognosis in patients with esophageal adenocarcinoma and squamous cell carcinoma. However, a significant proportion of apparently lymph node negative patients die early of metastatic disease. The aim of this study was to determine the prevalence and prognostic significance of occult lymph node metastasis in patients with esophageal adenocarcinoma and squamous cell carcinoma. METHODS: Lymph node sections from esophagectomy specimens of 78 patients with lymph node negative esophageal carcinoma (49 patients with adenocarcinoma and 29 with squamous cell carcinoma) were cut serially, it toto, and immunostained with the cytokeratin antibody AE1/AE3 and evaluated for occult lymph node metastasis. The results were correlated with the clinical and pathologic features and with patient survival. RESULTS: Fifteen of 49 patients (31%) with adenocarcinoma and 5 of 29 patients (17%) with squamous cell carcinoma had occult lymph node metastasis detected by cytokeratin staining. In the adenocarcinoma patients, the presence of occult lymph node metastasis showed a significant correlation with increasing depth of invasion, but was not associated significantly with any other clinical or pathologic feature. In the squamous cell carcinoma patients, the presence of occult lymph node metastasis did not correlate significantly with any clinical or pathologic parameter, except that patients with occult lymph node metastasis were more likely to have received preoperative chemotherapy or radiation therapy. Occult lymph node metastasis did not correlate with poorer survival rates in patients with either adenocarcinoma (Cox proportional hazards ratio: 1.42; P - 0.46) or squamous cell carcinoma (Cox proportional hazards ratio: 0.86; P = 0.90). CONCLUSIONS: Occult lymph node metastasis is not an independent poor prognostic feature in esophageal adenocarcinoma or squamous cell carcinoma. Therefore, the authors do not recommend extensive lymph node sectioning with keratin immunostaining for prognostication of patients with these malignancies.

Adenocarcinoma↗
PubMed1999

Pathologic prognostic factors in Barrett's associated adenocarcinoma: a follow-up study of 96 patients.

BACKGROUND: The objective of this study was to evaluate a variety of histologic features, some of which to our knowledge have never been evaluated in Barrett's-associated adenocarcinoma (BAd) (such as Crohn's-like lymphoid reaction and peritumoral lymphoid response) in patients with and without preoperative neoadjuvant chemotherapy combined with radiotherapy (chemrad) to determine their prognostic significance in these two groups of patients. METHODS: Tumor sections from 96 patients (83 males and 13 females; mean age, 62 years) with resected BAd (61 with chemrad and 35 without chemrad) were evaluated for numerous histologic features such as pathologic stage according to the American Joint Committee on Cancer TNM staging system, peritumoral lymphoid infiltrate, Crohn's-like lymphoid reaction, and degree of post chemrad residual tumor and correlated with the preoperative chemrad status and with survival (mean follow-up, 23 months). RESULTS: By univariate analysis, older patient age (P = 0.02), higher pathologic stage (P = 0.02) (including depth of invasion and lymph node status), infiltrative growth pattern (P = 0.05), perineural invasion (P = 0.05), vascular invasion (P = 0.04), and the absence of a peritumoral lymphoid infiltrate (P = 0.04) were associated with shortened survival in the entire cohort and in patients without chemrad, with the exception of infiltrative growth pattern (P = 0.1 in the nonchemrad group only). Higher stage was the only feature associated with decreased survival in the chemrad group. Subcategorization of lymph nodes according to the number involved with metastases (fewer than four, four to seven, and greater than seven) had no further effect on prognosis. However, subcategorization of T1 tumors into Tla and T1b did influence prognosis in a negative manner. Using multivariate analysis, only older patient age (P = 0.005) and the absence of a peritumoral lymphoid infiltrate (P = 0.05) were statistically associated with poor survival independent of stage. In addition, perineural invasion (P = 0.07) showed a trend toward shortened survival in patients with this feature. Preoperative chemrad had no effect on survival in this retrospective nonrandomized cohort of patients. CONCLUSIONS: This study confirms the strong prognostic usefulness of the TNM staging system in patients with resected BAd, even in those patients who received preoperative chemrad. In addition, older patient age, the absence of a peritumoral lymphoid infiltrate, and possibly perineural invasion correlate with poor survival independent of pathologic stage in patients with these tumors.

Adenocarcinoma↗
PubMed1999

Genetic analysis of prostatic atypical adenomatous hyperplasia (adenosis).

Atypical adenomatous hyperplasia (AAH) of the prostate, a small glandular proliferation, is a putative precursor lesion to prostate cancer, in particular to the subset of well-differentiated carcinomas that arise in the transition zone, the same region where AAH lesions most often occur. Several morphological characteristics of AAH suggest a relationship to cancer; however, no definitive evidence has been reported. In this study, we analyzed DNA from 25 microdissected AAH lesions for allelic imbalance as compared to matched normal DNA, using one marker each from chromosome arms 1q, 6q, 7q, 10q, 13q, 16q, 17p, 17q, and 18q, and 19 markers from chromosome 8p. We observed 12% allelic imbalance, with loss only within chromosome 8p11-12. These results suggest that genetic alterations in transition zone AAH lesions may be infrequent. This genotypic profile of AAH will allow for comparisons with well-differentiated carcinomas in the transition zone of the prostate.

Alleles↗
PubMed1999

Prognostic significance and effect of chemoradiotherapy on microvessel density (angiogenesis) in esophageal Barrett's esophagus-associated adenocarcinoma and squamous cell carcinoma.

Previous studies have shown that intratumoral microvessel density (IMD) correlates with clinical outcome in a variety of human neoplasms, such as those that arise in the breast, colon, and stomach, suggesting that angiogenesis is important in cancer progression. The aims of this study were to evaluate the prognostic utility of IMD in esophageal Barrett's-associated adenocarcinoma (AdCa) and squamous cell carcinoma (SCC), and to determine the effect of preoperative chemoradiotherapy (chemrad) on this process. Tissue sections of tumor from 67 patients with esophageal carcinoma (45 with Barrett's-associated AdCa, 22 with SCC) were stained with the vascular marker CD31. The IMD was calculated by evaluating at least 5 different 200 x fields of tumor hot spot areas to obtain the mean microvessel count (MVC). The data then were correlated with the clinical and pathological features, chemrad status, and patient survival. The MVC was significantly higher in AdCa (143 +/- 63.2) compared with SCC (77.2 +/- 38.6, P = 0.0001). In AdCa, no correlation was noted between the MVC and any of the clinical or pathological features, including chemrad status. In contrast, in SCC, a statistically significant higher MVC was detected in patients who did not receive chemrad (97.2 +/- 37.3) compared with those who did (48.3 +/- 15.9, P = .002) and in tumors that were larger in size (P = .02). However, the MVC did not correlate with survival in either AdCa or SCC (P > .05). The degree of angiogenesis is not a significant prognostic indicator in either esophageal AdCa or SCC. Preoperative chemrad has a positive effect on reducing the degree of angiogenesis in esophageal carcinoma, particularly SCC.

Adenocarcinoma↗
PubMed1999

Macrolide resistance phenotypes and mechanisms of resistance in Streptococcus pyogenes in La Rioja, Spain.

One hundred and thirty seven consecutive clinical Streptococcus pyogenes isolates were evaluated for macrolide-lincosamide-streptogramin resistance (MLS). Forty of these isolates were resistant to erythromycin (29.2%), 36 of them showed the new M resistance phenotype (erythromycin resistant and clindamycin susceptible) and four isolates had the MLS(B) resistance phenotype (erythromycin and clindamycin resistant). In all 36 isolates with the M resistance phenotype, the mef gene was identified by polymerase chain reaction (PCR). In two of the four S. pyogenes isolates with the MLS(B) phenotype, both ermB and ermTR genes were found; negative results were obtained with the other two isolates which might possess a new mechanism of high level resistance against erythromycin not previously described. In summary, a high rate of erythromycin resistance was found in S. pyogenes isolates and the active efflux pump mediated by the mef gene was the mechanism most frequently involved.

Anti-Bacterial Agents↗
PubMed1999

Bioactivity of prolactin isoforms: lactation and recovery of menses in nursing women.

To assess whether plasma prolactin (PRL) characteristics relate to lactogenesis and absence or presence of menstrual cycles, we measured bioactive PRL (BIO-PRL) using the Nb2 assay, immunoreactive PRL (IR-PRL) by radio-immunoassay, calculated equations describing the BIO-PRL-IR-PRL relationship and separated charged PRL isoforms (by chromatofocusing) in five amenorrhoeic and five cycling nursing women at 6 months postpartum and in 10 cycling non-nursing women. Plasma samples were drawn before and 30 min after a suckling episode at 0800, 1600 and 2400 h in nursing women and at the same hours in non-nursing women. BIO-PRL and IR-PRL concentrations were highest in amenorrhoeic nursing women, intermediate in cycling nursing women and lowest in cycling non-nursing women. The BIO-PRL-IR-PRL relationship shows that a given amount of IR-PRL corresponds to equivalent amounts of BIO-PRL in cycling nursing and cycling non-nursing women, and to a larger extent in amenorrhoeic nursing women. IR-PRL was present in plasma as several charge isoforms. Bioactive isoforms eluting at pH 6.0-5.1 were found in amenorrhoeic and cycling nursing women, reaching similar concentrations after suckling. Bioactive isoforms eluting at pH 7.0-6.1 were found only in amenorrhoeic nursing women. We speculate that isoforms eluting at pH 6.0-5.1 may play a role in lactation and isoforms eluting at pH 7.0-6.1, in lactational amenorrhoea.

Adult↗
PubMed1999

Interferon versus ribavirin plus interferon in chronic hepatitis C previously resistant to interferon: a randomized trial.

BACKGROUND: More than 70% of patients with chronic hepatitis C are resistant to interferon therapy. Ribavirin, in association with interferon, has been demonstrated as effective, at a dose of 800-1200 mg/day, but the efficacy of a lower dose has not been established. METHODS: We assessed the effectiveness of the combination of 600 mg/day of ribavirin plus 3 MU of interferon over a period of 6 months, in a group of patients previously resistant to interferon. Sixty-two patients with chronic hepatitis C with serum and hepatic HCV RNA relapsers or non-responders to interferon, were randomly divided into two groups: group A received 3 MU of interferon alpha-2b, three times a week for 6 months; group B was given the same dose plus 600 mg per day of ribavirin for 6 months. Two patients from each group dropped from therapy. One patient from group A and two from group B withdrew from treatment because of adverse effects. RESULTS: Mean alanine aminotransferase levels were similar in both groups throughout the study. A sustained response was observed in 7% and 7.4% of groups A and B with short-term response in 39% and 59%, and no response in 54% and 34% from both groups respectively (non-significant). At 12 months, 4 and 7 patients from groups A and B respectively, cleared serum HCV RNA however, only one sustained responder from each group cleared HCV RNA from peripheral blood mononuclear cells. At 18 months, 3 patients remained serum HCV RNA negative. Adverse effects were similar. Only haemoglobin values were lower in group B in the first month of therapy (p<0.05). CONCLUSION: In conclusion, the combination of 3 MU of interferon plus 600 mg of ribavirin is not effective in chronic hepatitis C resistant to interferon.

Adult↗
PubMed1999

In vitro activities of ketolide HMR3647, macrolides, and other antibiotics against Lactobacillus, Leuconostoc, and Pediococcus isolates.

Testing of susceptibility to 13 antibiotics was performed with 90 isolates of Lactobacillus, Leuconostoc, and Pediococcus. MICs at which 90% of the isolates tested were inhibited by HMR3647, erythromycin, and ciprofloxacin were 0.015, 0.125 and 32 microg/ml, respectively. The penicillin MIC was > or = 16 microg/ml against 26.2% of the studied Lactobacillus sp. isolates and 50% of Lactobacillus plantarum. HMR3647 showed excellent activity against these genera.

Anti-Bacterial Agents↗
PubMed1999

Efficacy of ampicillin plus ceftriaxone in treatment of experimental endocarditis due to Enterococcus faecalis strains highly resistant to aminoglycosides.

The purpose of this work was to evaluate the in vitro possibilities of ampicillin-ceftriaxone combinations for 10 Enterococcus faecalis strains with high-level resistance to aminoglycosides (HLRAg) and to assess the efficacy of ampicillin plus ceftriaxone, both administered with humanlike pharmacokinetics, for the treatment of experimental endocarditis due to HLRAg E. faecalis. A reduction of 1 to 4 dilutions in MICs of ampicillin was obtained when ampicillin was combined with a fixed subinhibitory ceftriaxone concentration of 4 micrograms/ml. This potentiating effect was also observed by the double disk method with all 10 strains. Time-kill studies performed with 1 and 2 micrograms of ampicillin alone per ml or in combination with 5, 10, 20, 40, and 60 micrograms of ceftriaxone per ml showed a > or = 2 log10 reduction in CFU per milliliter with respect to ampicillin alone and to the initial inoculum for all 10 E. faecalis strains studied. This effect was obtained for seven strains with the combination of 2 micrograms of ampicillin per ml plus 10 micrograms of ceftriaxone per ml and for six strains with 5 micrograms of ceftriaxone per ml. Animals with catheter-induced endocarditis were infected intravenously with 10(8) CFU of E. faecalis V48 or 10(5) CFU of E. faecalis V45 and were treated for 3 days with humanlike pharmacokinetics of 2 g of ampicillin every 4 h, alone or combined with 2 g of ceftriaxone every 12 h. The levels in serum and the pharmacokinetic parameters of the humanlike pharmacokinetics of ampicillin or ceftriaxone in rabbits were similar to those found in humans treated with 2 g of ampicillin or ceftriaxone intravenously. Results of the therapy for experimental endocarditis caused by E. faecalis V48 or V45 showed that the residual bacterial titers in aortic valve vegetations were significantly lower in the animals treated with the combinations of ampicillin plus ceftriaxone than in those treated with ampicillin alone (P < 0.001). The combination of ampicillin and ceftriaxone showed in vitro and in vivo synergism against HLRAg E. faecalis.

Algorithms↗