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Biomedical subjects

R Hernandez

Publications and source records attributed to R Hernandez.

At least 55 records · Page 3Linked to original sources
PubMed1998

Enhanced Heavy Metal Tolerance in Two Strains of Photosynthetic Euglena gracilis by Preexposure to Mercury or Cadmium

The effects of different concentrations of Hg, Cd, and Pb on cell growth, oxygen consumption, and production and contents of chlorophyll a and b of Z and B strains of Euglena gracilis was studied. Cell uptake of Cd and Pb was also determined. A greater cell density reached in the presence of Cd2+ correlated with a lower metal uptake capacity in B-strain cells. Cells of Z strain, preexposed to low concentrations of either Hg2+ (1.5 μM) or Cd2+ (50 μM) for several generations showed improved heavy metal tolerance (greater cell density and viability) together with similar metal uptake capacity. Because Cd2+ preadaptation but not Hg2+ pretreatment induced a significant increase in the content of acid-soluble thiols, the data suggest the existence of different mechanisms of heavy metal detoxification in Euglena. The fact that Z-strain cells showed a greater Cd2+ uptake under all the conditions assayed suggests that Z strain would be more suitable for bioremediation of polluted waters.

Journal Article↗
PubMed1998

Biological characterization and genetic diversity of Mexican isolates of Trypanosoma cruzi.

The present work reports the in vitro biological characterization of 17 Trypanosoma cruzi isolates from southern and central México, and compares these results to those of four South American strains and one clone from Brazil. The parameters evaluated were growth rates, percentage of parasites undergoing transformation from epimastigotes to trypomastigotes, infectivity to, and in vitro killing of cultured Vero and P388 cells. Isoenzyme patterns of 11 enzymatic systems and 16 loci were also determined for the Mexican isolates. The parasites showed differences in growth, depending if they were cultured in LIT with hemin or in Grace's media. Transformation was obtained only in Grace's medium and differences were observed between the stocks. Stocks Z10 and Z21 showed the highest percentage of transformation within the Mexican isolates (39 and 41%, respectively). A second group showed percentages of transformation between 15 and 28%. In contrast, the South American strains showed higher rates of transformation (36-65%). Infection of cultured cells by isolates Z10 and H5 was evaluated in both Vero and P388 cells. Differences were observed both in the percentage of infected cells as well as in the number of amastigotes per cell. Differences in the ability to cause in vitro killing of P388 cells were also observed among the isolates. Isoenzyme analysis revealed genetic variation between the isolates, each of them with an unique zymodeme. This genetic analysis revealed, in general, a clustering based on the geographical origin of the isolates. Finally, correlation with clinical symptoms is discussed.

Animals↗
PubMed1998

Advantage of stents in the most proximal left anterior descending coronary artery.

OBJECTIVES: Balloon angioplasty of the proximal left anterior descending artery is associated with a high rate of restenosis. We hypothesized that the significant reduction in restenosis rates demonstrated by stent implantation in the coronary arteries in general would be especially prominent in the most proximal left anterior descending coronary artery. METHODS: We reviewed 65 consecutive patients in whom stents were placed in the most proximal left anterior descending artery between March 1990 and July 1995 and compared them with 56 consecutive patients with angioplasty. Minimum luminal diameter was measured angiographically before, after, and 6 months after the intervention. We compared the change in minimum luminal diameter and restenosis rate between the patients with stents and the patients with angioplasty to clarify the response of this important artery to these different procedures. RESULTS: There was 6-month angiographic follow-up of the treated lesion in 99% of the patients. The postprocedure minimum luminal diameter, acute gain, and minimum luminal diameter at follow-up were greater in arteries treated with stents than in those treated with balloons. Of importance, late loss was not significantly different between the two groups after treatment at this site. Thus the restenosis rate after angioplasty was 52% compared with 20% after stent implantation (p < 0.001). CONCLUSIONS: Stent implantation in the most proximal left anterior descending artery is associated with an even greater reduction in restenosis rate than implantations elsewhere in the coronary arteries. This enhanced reduction in restenosis appears to be due to an unusually large amount of late loss after angioplasty at this site.

Angioplasty, Balloon↗
PubMed1998

Combined trabeculectomy and phacoemulsification: a one-site vs a two-site approach.

PURPOSE: To compare the results of combined trabeculectomy and phacoemulsification surgery with intraocular lens implant by means of a one-site vs a two-site approach. METHODS: Glaucomatous patients with a coexisting cataract were randomly assigned to undergo either a one-site or two-site combined procedure. One-site surgery was performed with a limbus-based conjunctival flap and scleral tunnel at the 12-o'clock position. Two-site surgery was performed with a limbus-based conjunctival flap for the trabeculectomy in the superior nasal quadrant and a temporal clear cornea incision for phacoemulsification. Mitomycin C (0.4 mg/ml for 2 minutes) was applied to the scleral surface at the trabeculectomy site for both approaches. All patients received intraocular lens implants at the time of combined surgery. RESULTS: Thirty-three eyes of 33 patients were included in this study. Preoperative intraocular pressure and number of glaucoma medications were similar in the two groups. Corrected visual acuity improved similarly in both groups. Intraocular pressure decreased in both groups at last follow-up but was not significantly different (P = .129) between the one-site and two-site groups. At last follow-up, the one-site group required significantly more (P = .030) medications than did the two-site group. CONCLUSIONS: Combined trabeculectomy and phacoemulsification surgery in which one-site and two-site techniques were used yielded similar improvements in corrected visual acuity and intraocular pressure reduction. However, the one-site group required more medication to maintain intraocular pressure control than did the two-site group.

Aged↗
PubMed1998

The role of ultrasonography in the diagnosis of pyloric stenosis: a decision analysis.

BACKGROUND/PURPOSE: The appropriate role for ultrasonography (US) as a replacement for the upper gastrointestinal series (UGI) in vomiting infants remains undefined. The authors have used decision analysis techniques to determine whether the use of ultrasonography as an initial screen in vomiting infants is cost effective when compared with the UGI as the only study. METHODS: Two diagnostic strategies were compared: 1) UGI alone and 2) ultrasonography followed by an UGI series in 50% of cases when ultrasonography scan was negative for pyloric stenosis. The test sensitivity (US, 0.9; UGI, 1.0) and test specificity (US, 1.0; UGI, 1.0) and the incidence of pyloric stenosis among vomiting infants presenting to the community pediatrician (0.30) or after a negative examination by an experienced examiner (0.02 to 0.18) were obtained from a review of the literature. The relative charges for ultrasonography and UGI were obtained from a national survey from which the cost ratio of US to UGI was estimated to range from 0.67 to 1.81 with a median of 1.06. RESULTS: Under these baseline assumptions, UGI only was the preferred strategy. The results of the decision analysis were sensitive to, or dependent on, assumptions made regarding the incidence of pyloric stenosis, the US to UGI cost ratio, the sensitivity of the US, and the proportion of patients that proceed to UGI when the US scan was negative for pyloric stenosis. When at least 50% of patients whose US scan was negative for pyloric stenosis proceeded to a UGI, UGI remained the preferred strategy for all cost ratios examined (0.6 to 1.7). Even when no patients proceeded to UGI, the cost ratio of US to UGI had to be less than 0.7 under the typical incidence (0.30) of pyloric stenosis among vomiting infants presenting to the community pediatrician for US to be cost effective. Finally, only UGI was indicated when an olive was not appreciated by an experienced examiner. CONCLUSION: Under assumptions that fit most clinically relevant circumstances, the UGI as the initial study is the most cost-effective radiological diagnostic test in the evaluation of the vomiting infant.

Contrast Media↗
PubMed1998

Actions implemented to improve hypertension control in Spain.

Hypertension prevalence is estimated at approximately 30% of the adult population in Spain, using the 140/90 mm Hg cutoff. This represents a heavy public health burden when compared with other European countries, although the direct cost per person is one of the lowest in Europe. The programs implemented regionally since 1985 are presented here. As a result of them, a decade later the number of hypertensives with controlled blood pressure has increased from 10% in 1986 to 13% in 1995, and cerebrovascular mortality has steadily decreased.

Adolescent↗
PubMed1998

Comparison of genomic DNA in various strains of Boophilus microplus (Acari: Ixodidae).

The conventional method of identifying acaricide resistance in a suspect tick population by the United Nations Food and Agriculture Organization packet assay is a laborious and time-consuming process. DNA probes have been demonstrated as rapid and accurate tools for detecting pesticide resistance in insect species. Random-amplified polymorphic DNA (RAPD) has been used by other groups to differentiate species of mosquitoes and populations within a mosquito species. By using different arbitrary oligonucleotides as primers with RAPD, we have demonstrated that various strains of Boophilus microplus (Canestrini) show different patterns of DNA fragments on agarose gel electrophoresis. The unique DNA fragments may be useful for developing probes that can detect acaricide resistance in field pest populations.

Animals↗
PubMed1997

DNA demethylation and pericentromeric rearrangements of chromosome 1.

Rearrangements in the vicinity of the centromere of chromosome 1 are over-represented in many types of human cancer and are a characteristic feature of a rare genetic disease called ICF (immunodeficiency, centromeric heterochromatin instability, and facial anomalies). Evidence is presented that implicates DNA hypomethylation in the formation of these pericentromeric chromosomal anomalies. The DNA methylation inhibitors 5-azadeoxycytidine and 5-azacytidine, but not other tested genotoxins, induced the preferential formation of pericentromeric rearrangements of chromosome 1 at a very high frequency in a pro-B-cell line (FLEB14) and at a lower frequency in a mature B-cell line (AHH-1). These abnormal chromosomes appear identical to the diagnostic chromosomal aberrations in the ICF syndrome. A major component of the pericentromeric DNA in chromosome 1, satellite 2, was shown to be hypomethylated in an ICF B-cell line, although DNA from this cell line did not display detectable overall hypomethylation. It is hypothesized that demethylation in certain DNA regions, including in pericentromeric satellite DNA, helps lead to pericentromeric chromosomal rearrangements in lymphocytes from ICF patients and in normal lymphoblastoid cells incubated in vitro with DNA demethylating agents.

Adult↗
PubMed1997

Effects of Palmaz-Schatz stents on angled coronary arteries.

This review of consecutive, single Palmaz-Schatz stent implantations reveals that coronary lesion angulation does not result in suboptimal results or increased restenosis after stenting. The implantation of a rigid stent at an arterial hinge point is associated with an increased restenosis rate.

Coronary Angiography↗
PubMed1997

Risk of incontinence with transurethral resection of the prostate after radiation therapy for prostate cancer.

BACKGROUND: It has been reported that transurethral resection of the prostate (TURP) after definitive radiation therapy for prostate cancer is associated with a significant risk of incontinence. The presumed reason for incontinence is external sphincter damage from TURP or pre-existing damage from either extension of prostate cancer or radiation therapy. METHODS: We reviewed seven recent cases of TURP for bladder outlet obstruction in patients who had undergone radiation therapy for clinical stage T(3-4)M(0)N(0) adenocarcinoma of the prostate. All seven men progressed to either chronic retention or debilitating obstructive symptoms with weak peak flows from 3.4 to 5.1 cc/s (mean 4 cc/s). Each of them subsequently underwent a limited TURP. RESULTS: Voiding symptoms were reduced in all patients and peak flows were improved to 6.3 to 20 cc/s (mean 14.8 cc/s) with mean follow-up 35 m. No patient developed stress urinary incontinence postoperatively. CONCLUSION: These results suggest that TURP can be performed successfully after radiation therapy with minimal risk of stress incontinence.

Adenocarcinoma↗
PubMed1997

Intracoronary ultrasound before coronary interventions: a prospective comparison of two different catheters.

Intravascular ultrasound (IVUS) provides unique information about the coronary arterial wall that can be used to guide transcatheter therapy. In this prospective study, two different IVUS systems were compared with respect to feasibility of imaging before intervention and angiographic changes induced by the simple advancement of the catheter across the lesion. Eighty-five patients (mean age 59 +/- 10 yr, 11 female) were studied with IVUS before intervention. In 34 patients, a 4.8 F (1.6-mm) IVUS catheter was used (Group I), whereas in the remaining 51 patients, a 3.5 F (1.2-mm) IVUS catheter was used (Group II). Quantitative angiography was performed before and after the IVUS study to determine potential changes in lumen diameter. Clinical and angiographic characteristics were similar in the two groups. A successful IVUS interrogation of the target lesion was obtained more frequently in Group II (45/51 (88%) vs. 19/34 (56%) patients, P < 0.01). After the IVUS study, a change in minimal lumen diameter was seen in Group I (baseline 0.84 +/- 0.2 vs. final 1.17 +/- 0.2 mm, P < 0.001) and Group II patients (baseline 0.80 +/- 0.3 vs. final 1.03 +/- 0.4 mm, P < 0.01). In the 64 lesions successfully crossed, the absolute gain in lumen diameter was significantly higher in Group I (0.40 +/- 0.2 vs. 0.23 +/- 0.2 mm, P < 0.05). In addition, an inverse correlation was found between baseline minimal lumen diameter and the absolute lumen gain induced by the IVUS study in Group I (r = -0.47, P < 0.05) but not in Group II patients (r = -0.16, NS). Neither angiographic nor echogenic lesion characteristics were associated with the change in lumen diameter. When multivariate analysis was applied, catheter size was the only independent predictor of lumen gain induced by IVUS after adjustment. Thus, the advancement of IVUS catheters across severe coronary lesions induces significant angiographic changes consistent with plaque remodeling and a Dotter effect. The use of smaller catheters not only allows a higher number of lesions to be studied before intervention, but also lessens the mechanical disruption of the plaque, yielding a more accurate and veracious picture of baseline plaque characteristics.

Aged↗
PubMed1997

Feasibility of intravascular ultrasound studies: predictors of imaging success before coronary interventions.

BACKGROUND: Intravascular ultrasound (IVUS) is currently used to study lesions during transcatheter coronary therapy. However, before dilation some lesions cannot be reached or crossed with the imaging catheter. HYPOTHESIS: This study seeks to elucidate which factors determine the feasibility of IVUS examination before coronary interventions. METHODS: Accordingly, 100 consecutive patients undergoing IVUS examination before coronary angioplasty were prospectively studied. The clinical and angiographic characteristics of 77 patients with a successful IVUS study (Group A) were compared with those of 23 patients in whom IVUS was attempted but the target lesion could not be interrogated (Group B). The echogenic characteristics of the target lesion [before (n = 77) or after intervention (in 18 patients in Group B)] were also studied. RESULTS: Patients in Group B were significantly older (62 +/- 7 vs. 57 +/- 10 years, p < 0.05) and more frequently had stable angina [8 (35%) vs. 9 (11%), p < 0.05]. The distribution of lesions within the coronary tree and angiographic lesion characteristics including length, eccentricity, calcification, bend location, and the American College of Cardiology/American Heart Association classification were similar in both groups. However, proximal tortuosities (> 45 degrees at end diastole) were more frequently found in Group B [20 (87%) vs. 47 (61%), p < 0.05]. In addition, by quantitative angiography, patients in Group B had smaller arteries (reference diameter 2.8 +/- 0.4 vs. 3.1 +/- 0.4 mm, p < 0.05) and more severe lesions (minimal lumen diameter 0.46 +/- 0.24 vs. 0.65 +/- 0.34 mm, p < 0.05). On IVUS, calcified lesions were more frequently visualized in Group B (61 vs. 38%, p < 0.05). On multivariate analysis, catheter size, baseline minimal lumen diameter, angiographic proximal tortuosities, and lesion calcification on imaging were independent predictors of the feasibility of IVUS studies. CONCLUSIONS: Unsuccessful IVUS studies before intervention occur more frequently (1) in vessels with proximal tortuosities or severe lumen narrowing, (2) in lesions that are calcified on IVUS, and (3) when large imaging catheters are used.

Angina Pectoris↗
PubMed1997

The spatial distribution of human immunoglobulin genes within the nucleus: evidence for gene topography independent of cell type and transcriptional activity.

The three-dimensional positioning of immunoglobulin (Ig) genes within the nucleus of human cells was investigated using in situ hybridization and confocal microscopy. The visualization of heavy and light chain genes in B-lymphoid cells showed that the three Ig genes are differentially and nonrandomly distributed in different nuclear subvolumes: the kappa genes were found to be preferentially confined to an outer nuclear volume, whereas the gamma and lambda genes consistently occupied more central positions within the nucleus, the lambda genes being more interior when compared with the gamma genes. The data further show that these overall topographical distributions are independent of gene transcriptional activity and are conserved in different cell types. Although subtle gene movements within those defined topographical regions cannot be excluded by this study, the results indicate that tissue specificity of gene expression is not accompanied by drastic changes in gene nuclear topography, rather suggesting that gene organization within the nucleus may be primarily dependent on structural constraints imposed on the respective chromosomes.

B-Lymphocytes↗
PubMed1997

Angioscopic evaluation of angiographically complex coronary lesions.

Coronary angioscopy (CA) provides direct visualization of the endoluminal surface of coronary vessels. The usefulness of CA during coronary angioplasty of angiographically complex lesions remains to be established. This study was designed to determine the value of CA to elucidate the underlying substrate of angiographically complex lesions. Forty-seven consecutive patients with angiographically complex lesions were studied with CA before coronary intervention. Mean age of the group was 59 +/- 9 years; six patients were women. Forty (85%) patients had unstable angina. Complex angiographic lesions included coronary occlusions (n = 23) (14 with Thrombolysis in Myocardial Infarction coronary flow grade 0 and nine with flow grade 1), lesions with intraluminal filling defects suggestive of thrombus or ulceration (n = 8), and lesions that were highly eccentric (n = 16). Items analyzed with CA included red thrombus (lining or protruding) and plaque color (yellow, white, or mixed). In all patients, CA visualized the protruding material causing the angiographic appearance. At this site CA detected red thrombus in 34 (72%) patients (14 protruding, 20 lining) and atherosclerotic plaque in 45 (96%) patients. At the site of the angiographically complex lesion, plaque was classified as predominantly yellow in 24 patients, mixed in 12, and white in nine. The incidence of thrombus on CA was higher for occluded vessels (91%) or lesions with intraluminal filling defects or ulceration (87%) than in eccentric lesions (37%) (p < 0.05). However, plaque coloration was not significantly different among these three angiographic subgroups. Initial procedural success (without stent requirement) was lower in lesions showing protruding thrombus on CA (64% vs 91 %, p < 0.05). Thus most angiographically complex lesions contain thrombus. On CA red thrombus was more frequently identified on occluded vessels and lesions with filling defects or ulceration than in eccentric lesions. Yellow or mixed plaques are common in these patients, suggesting lipid-laden plaques as the underlying pathologic substrate of angiographically complex lesions.

Aged↗
PubMed1997

Results at 43 months' follow-up of a double-blind, randomized, prospective clinical trial using intravesical interferon alpha-2b in the prophylaxis of stage pT1 transitional cell carcinoma of the bladder.

OBJECTIVES: To assess the intravesical efficacy of 60 million units of interferon (IFN) alpha-2b in preventing recurrences of Stage pT1 transitional cell carcinoma of the bladder, as well as to assess its local and systemic toxicity. METHODS: A total of 90 patients were included in a double-blind, randomized, prospective clinical trial and divided into two groups of 45 patients. After complete transurethral resection, 60 million units IFN alpha-2b was instilled in one group; in the other, double-distilled water was used. The therapeutic regimen consisted of weekly instillation for 12 weeks, followed by once-monthly instillation until patients had completed 1 year of treatment. RESULTS: Only 78 patients were evaluable. After 12 months of follow-up, the relapse rate was 28.2% (11 of 39) for the IFN group and 35.8% (14 of 39) for the control group (P = NS). After 43 months (range 9 to 67), relapse rates were 53.8% (21 of 39) and 51.2% (20 of 39), respectively (P = NS). Progression, mortality, and local or systemic toxicity were similar in both groups. Flu-like syndrome was not reported. CONCLUSIONS: At the dose used in this study, IFN alpha-2b proved ineffective in the prophylaxis of Stage pT1 transitional cell carcinoma of the bladder compared with a control group. Toxicity was virtually absent.

Administration, Intravesical↗
PubMed1997

Heritable genetic alterations in a xeroderma pigmentosum group G/Cockayne syndrome pedigree.

A search for genetic alterations within the XPG gene has been conducted on skin and blood cells cultured from a newly characterized xeroderma pigmentosum (XP) patient (XP20BE). This patient is the ninth known case that falls into the extremely rare XP complementation group G. Four genetic markers within the XPG gene (including two polymorphisms) demonstrated the Mendelian distribution of this gene from the parents to the patient and to an unaffected sibling. The patient (XP20BE) inherited a G to T transversion from his father in exon 1 of the XPG gene that resulted in the conversion of a glutamic acid at codon 11 to a termination codon. The patient also inherited an XP-G allele from his mother that produces an unstable or poorly expressed message. The cause of the latter defect is still uncertain. In addition to these alterations, XP20BE cDNA contained an mRNA species with a large splicing defect that encompassed a deletion from exon 1 to exon 14. This splicing defect, however, appears to be a naturally occurring low-frequency event that results from abnormal splicing that occurs between certain conserved non-consensus splicing signals within the human XPG gene.

Cells, Cultured↗