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Biomedical subjects

H Vargas

Publications and source records attributed to H Vargas.

At least 19 recordsLinked to original sources
PubMed2004

Oil spills debris clean up by thermal desorption.

Oil spills represent a significant environmental issue in Brazil. This paper presents the latest results of a comprehensive experimental programme aimed at understanding how the presence of spilled oil affects the properties of sands and at studying alternatives to remediate the affected shores. Results indicate that oil causes a slight increase in grain size and uniformity, and oiled debris presents a smaller void ratio but a larger unit weight. It was also observed that effective strength parameters for both the natural and oiled debris were the same although the undrained strength of a natural sand is much higher than that of the contaminated sand. At ambient temperature, oiled debris emits methane and ammonia, and these emissions tend to increase with rising temperatures. On the other hand, the oil and grease content from oiled debris decreases with rising temperature and prolonged exposure. Finally, in situ thermal desorption seems to be a promising method for cleaning debris from oil spills. It is simple, fast and avoids all the difficulties associated with digging up the soil for disposal or cleanup.

Brazil↗
PubMed2001

Changes in hepatitis C virus population in serum and peripheral blood mononuclear cells in chronically infected patients receiving liver graft from infected donors.

BACKGROUND: We have previously studied hepatitis C (HCV)-infected recipients of livers from HCV-infected donors and found that either the donor's strain or the recipient's strain predominate in serum. The current study was undertaken to determine whether these changes are complete and whether they are reflected in the population of virus associated with peripheral blood mononuclear cells (PBMCs). METHODS: We analyzed HCV ribonucleic acid from sequential serum and PBMC samples from 11 and 8 patients, respectively. The relatively stable NS5 region was chosen for analysis because it allowed for dependable identification of donor and recipient strains. Viral sequences were analyzed by direct sequencing and by sensitive strain-specific polymerase chain reaction assays. These assays were capable of detecting the minor sequence present at a concentration 1:104-10-7 below that of the major sequence. RESULTS: Five patients retained their original infecting strain; the donor strain was detected only transiently. In the remaining six patients, recipient strain was detected for the first few weeks, after which only the donor strain was consistently present. However, in one patient the second nondominant strain was detected from the background of the major strain on a single occasion 8 months after transplantation. All changes in serum were closely paralleled by those occurring in PBMCs. CONCLUSIONS: Viral population changes in the setting of liver transplantation from HCV-infected donors to HCV-infected recipients occur simultaneously in PBMCs and serum. The takeover of one strain by another in PBMC- and serum-derived viral populations seemed to be complete and long lasting.

Base Sequence↗
PubMed2001

Initial nonoperative management for periappendiceal abscess.

PURPOSE: Our goal was to compare initial operative and nonoperative management for periappendiceal abscess complicating appendicitis. METHODS: This study is a retrospective review of 155 consecutive patients with appendicitis complicated by periappendiceal abscess treated between 1992 and 1998. Eighty-eight patients were treated initially nonoperatively, and 67 patients were treated operatively. All patients had localized abdominal tenderness and either computed tomography or intraoperative documentation of an abscess. RESULTS: Our patient population consisted of 107 males and 48 females, with an average age of 33 (range, 16-75) years. Age, gender, comorbidity, white blood cell count, temperature, and heart rate did not differ significantly between groups. For the initial nonoperative management group, the failure rate was 5.8 percent and the appendicitis recurrence rate was 8 percent after a mean follow-up of 36 weeks. The response to treatment of the initial nonoperative group and the initial operative group was compared by length of stay (9 +/- 5 days vs. 9 +/- 3 days; P = not significant), days until white blood cell count normalized (3.8 +/- 4 days vs. 3.1 +/- 3 days; P = not significant), days until temperature normalized (3.2 +/- 3 days vs. 3.1 +/- 2 days; P = not significant), and days until a regular diet was tolerated (4.7 +/- 4 days vs. 4.6 +/- 3 days; P = not significant). Complication rate was significantly lower in the nonoperative group (17 vs. 36 percent; P = 0.008). CONCLUSIONS: Initial nonoperative management of appendicitis complicated by periappendiceal abscess is safe and effective. Patients undergoing initial nonoperative management have a lower rate of complications, but they are at risk for recurrent appendicitis.

Abscess↗
PubMed2001

Exposure of hepatitis C virus (HCV) RNA-positive recipients to HCV RNA-positive blood donors results in rapid predominance of a single donor strain and exclusion and/or suppression of the recipient strain.

We have analyzed three cases of hepatitis C virus (HCV)-infected recipients who received blood from HCV-infected donors. Two recipients were exposed to two different HCV RNA-positive donors, and one was exposed to a single donor. All parental genomes from the actual infecting units of blood and the recipients were defined, and their presence in the follow-up serum samples was determined using sensitive strain-specific assays. The strain from one of the donors was found to predominate in all recipients' serum samples collected throughout the follow-up period of 10 to 30 months. In two recipients exposed to two infected donors, the strain from the second donor was occasionally found at very low level. However, the original recipients' strains were not detected. Our observations show that HCV-infected individuals can be superinfected with different strains, and this event may lead to eradication or suppression of the original infecting strain. Furthermore, our findings demonstrate that simultaneous exposure to multiple HCV strains may result in concomitant infection by more than one strain, although a single strain could rapidly establish its dominance. The results of the present study suggest the existence of competition among infecting HCV strains which determines the ultimate outcome of multiple HCV exposure.

Adult↗
PubMed2001

Unusual paranasal sinus tumors in two patients with common nasal complaints.

Common nasal complaints are managed by both the otolaryngologist and the primary care physician. We describe the cases of two patients with nasal obstruction who were referred to us for evaluation--one with severe headache and the other with profuse epistaxis. Their histories prior to referral included long-term, common rhinologic complaints of low-grade headache and mild epistaxis. Neither patient had been referred to us until their symptoms had become severe. Our examination revealed that both patients had rare paranasal sinus pathology. One patient had a fibroxanthoma of the frontal sinus, and the other had extramedullary hematopoiesis of the maxillary sinus. Fibroxanthoma of the frontal sinus is rare, and extramedullary hematopoiesis of the maxillary sinus has not been previously reported. These two unique cases serve as a reminder that long-term common rhinologic complaints can occasionally be a sign of life-threatening pathology and require a full evaluation by an otolaryngologist.

Adult↗
PubMed2000

Late-onset renal failure after liver transplantation: role of posttransplant alcohol use.

BACKGROUND: Late-onset renal failure is being increasingly recognized as a complication in patients undergoing liver transplantation for hepatitis C virus (HCV). However, its precise incidence, predisposing risk factors, and impact on outcome after liver transplantation, have not been defined. METHODS: The development of late-onset renal failure (defined as serum creatinine persistently >2.0 mg/dl, occurring more than 6 months posttransplant) was assessed in 120 consecutive liver transplant recipients who survived at least 6 months after transplantation. Fifty-seven percent (68/120) of the patients had undergone transplantation for liver disease due to HCV. The median follow-up was 5 years. RESULTS: Late-onset renal failure developed in 28% (33/120)of the patients. Posttransplant alcohol use (P=0.0001), posttransplant diabetes (P=0.0042), and recurrent HCV hepatitis (P=0.019) were significantly associated with late onset renal failure. In multivariate analysis, alcohol use (O.R. 10.7, 95%; CI 2.4-35.9, P=0.001) and diabetes (O.R. 2.1, 95%; CI 1.1-9.9, P=.03) were independently significant predictors of late onset renal failure. When only patients transplanted for HCV were analyzed, posttransplant alcohol use (P=0.004) was the only significant independent predictor of late-onset renal failure. HCV genotype 1b, as compared with other HCV genotypes, was associated with a higher rate of late-onset renal failure in patients with HCV; 70% of the patients with genotype 1b versus 32% of those with 1a and 33% of those with 2b, developed late onset renal failure (P=0.03). At a median follow up of 5 years, mortality in patients with HCV with late-onset renal failure was 52% as compared with 2% in those without renal failure (P=.0001). CONCLUSION: Late-onset renal failure in patients with HCV portended a grave outcome. Alcohol use was an independent predictor of late-onset renal failure in patients with HCV and represents a potentially modifiable risk factor for late-onset renal failure in these patients.

Adult↗
PubMed2000

A pilot study evaluating the treatment of postparotidectomy sialoceles with botulinum toxin type A.

OBJECTIVE: To report our experience in treating 4 cases of recurrent siacloceles with botulinum toxin type A after partoid surgery. DESIGN: This is a prospective, nonrandomized, nonblinded pilot study describing a new use for botulinum toxin type A. SETTING: Tertiary academic medical center. PATIENTS: Four patients (2 men and 2 women) with persistent postparotidectomy sialoceles who had undergone various treatment failures were included. The diagnosis was made by fine-needle aspiration of the mass based on well-recognized cytologic features of the entity, as well as an elevated amylase level and no evidence of tumor or infection. INTERVENTIONS: Sialoceles were aspirated before local injection of botulinum toxin type A (30-50 U) subcutaneously. MAIN OUTCOME MEASURES: The patients were followed up 1 week after receiving botulinum toxin type A injection and then at monthly intervals. They were extensively questioned and examined for any evidence of side effects or recurrence. RESULTS: All patients had total resolution of sialocele or external salivary fistula within 1 month of treatment. None of the patients to date have demonstrated recurrences at 7 through 13 months, and there were no complications, particularly facial nerve weakness. CONCLUSION: Our findings suggested that botulinum toxin type A offers a highly effective, safe, and noninvasive method of treatment in postparotidectomy sialocele.

Adult↗
PubMed2000

Nonoperative management of perforated appendicitis without periappendiceal mass.

BACKGROUND: Initial nonoperative treatment for patients with periappendiceal mass has been shown to be safe and effective. Our goal was to evaluate the safety and efficacy of initial nonoperative management for perforated appendicitis not accompanied by a palpable mass. METHODS: The study population consisted of 77 patients with appendicitis treated initially nonoperatively between 1992 and 1998. All had localized abdominal tenderness and computed tomography findings of abscess or phlegmon. None had a palpable abdominal mass. Outcome parameters evaluated were rate of failure, complication, and recurrence. RESULTS: There were 49 males and 28 females with a mean age of 35 years (range 16 to 75). Initial nonoperative management was successful in 95% of patients. Complications occurred in 12% of patients. Recurrent appendicitis developed in 6.5% of patients after an average follow-up of 30 weeks. CONCLUSIONS: Perforated appendicitis patients with localized abdominal tenderness and abscess or phlegmon can safely and effectively be treated in an initial nonoperative fashion.

Abdominal Abscess↗
PubMed2000

Quality of life in long-term survivors after liver transplantation: impact of recurrent viral hepatitis C virus hepatitis.

Post liver transplant recurrence of infection with hepatitis C virus (HCV) occurs in approximately 50% of patients transplanted because of HCV-related liver disease. The aim of this study was to assess long-term quality of life, psychologic distress, and coping in patients with recurrent HCV after liver transplantation in comparison to patients transplanted for other etiologies of underlying liver disease. All liver transplant recipients transplanted at a University affiliated Veterans Affairs Medical Center who had greater than 6 months follow-up were sent a questionnaire investigating quality of life (assessed by Medical Outcomes study health survey SF-36), depression (assessed by Beck Depression Inventory), total mood disturbance (assessed by Profile of Mood States scale), coping (assessed by Billing and Moos Inventory of coping with illnesses), and employment status. Lower Beck Depression Inventory score (p = 0.001), lower mood disturbance score (p = 0.0001), overall satisfaction with present work (p = 0.0001), and lesser use of avoidant coping (p = 0.06) were predictors of better quality of life in long-term survivors of liver transplantation. At a mean follow-up of 4 yr after liver transplantation, patients with histopathologically diagnosed recurrent viral HCV hepatitis had significantly lower global quality of life score (mean score of 76.4 versus 86.2, p = 0.011) and physical functioning score (mean score 20 versus 25, p = 0.015), as compared to all other patients. In summary, quality of life and physical functioning were significantly impaired in liver transplant recipients with histopathologically diagnosed recurrent HCV hepatitis, as compared to those whose HCV hepatitis had not recurred or those transplanted for other reasons.

Adaptation, Psychological↗
PubMed2000

More aggressive behavior of squamous cell carcinoma of the anterior tongue in young women.

OBJECTIVE: To review the combined experience from two large medical centers in treating young female patients with anterior tongue cancer to determine the clinical course of this unique subset of patients. STUDY DESIGN: Retrospective study. METHODS: Seventeen female patients less than 40 years of age (group A) and 17 older patients, both male and female, greater than 40 years of age (group B) who had treatment for invasive squamous cell carcinoma of the anterior tongue were studied. The charts were reviewed for the clinical staging, treatment, and outcome of each patient. The disease-free survival and recurrence rates were compared between the two cohorts. RESULTS: The mean disease stage between the groups was II. The survival analysis showed a significant difference between the two groups in recurrences (group A = 65%, group B = 41%; P = .02). Further, of the patients who had recurrence, the young women did so significantly earlier in their disease course than the older patients (group A = 14 mo, group B = 40 mo; P < .05). Although the survival differences did not reach statistical significance (P = .15), the power of the study was low (power = 0.26) resulting in a high-level type II error. CONCLUSION: These data suggest that young women with squamous cell carcinoma of the anterior tongue have significantly higher rates of recurrent disease and the interval to recurrence is significantly shorter than in older patients. Further investigation is warranted until a statistically significant cohort is accrued; until that time, these patients warrant an aggressive initial treatment and close surveillance for recurrence.

Adolescent↗
PubMed2000

Cellular origin of gastrointestinal stromal tumors: a study of 27 cases.

CONTEXT: Interstitial cells of Cajal (ICCs), also known as pacemaker cells, are cells in the gastrointestinal tract that play a role in the control of gut motility. The ICCs express the c-kit proto-oncogene encoding a type III tyrosine kinase (KIT) receptor, a ligand that is known as stem cell factor (SCF). The maturation of ICCs is dependent on SCF-KIT interaction. The cellular origin, differentiation, nomenclature, and prognosis of gastrointestinal stromal tumors (GISTs) are controversial. OBJECTIVE: To test the hypothesis that GISTs originate from CD34-positive stem cells and differentiate toward an ICC phenotype. MATERIALS AND METHODS: We studied 27 cases of smooth muscle differentiated GISTs collected for 14 years (1985-1999), including 8 benign (leiomyoma), 15 malignant primary (leiomyosarcoma), and 4 metastatic to the liver. Immunohistochemical studies of selected lineage-directed monoclonal antibodies of c-kit (CD117), CD34, vimentin, desmin, alpha-actin, S100, and MIB-1 were performed on both normal and tumor tissues. RESULTS: Immunoperoxidase stains of normal gastrointestinal tract showed both c-kit and CD34-positive cells surrounding the Auerbach ganglia plexus in the gastrointestinal tract. Twenty-seven of 27 tumors strongly expressed c-kit. Fourteen of 27 tumors were positive for CD34. Of the malignant GISTs, 14 of 19 were positive for CD34; of the benign tumors, 0 of 8 were positive for CD34. Thus, CD34 was the best indicator of malignant phenotype. CONCLUSION: This is the first description of benign smooth muscle GISTs negative for CD34. The results of this study suggest that GISTs originate from CD34-positive stem cells and differentiate toward pacemaker cell phenotype. The lack of expression of CD34 in the benign GIST may indicate that benign GISTs are composed of more mature ICCs, whereas malignant GISTs are composed of dedifferentiated ICCs that express CD34-positive stem cells.

Adult↗
PubMed2000

A case-control study of laparoscopic versus open sigmoid colectomy for diverticulitis.

Laparoscopic sigmoid colectomy (LSC) for diverticular disease accounts for a limited number of laparoscopic colon cases performed nationally because of the technical challenge it presents. Our objective was to determine the feasibility and impact of the laparoscopic approach in elective sigmoid colectomy for diverticular disease and to compare these results with those of the open approach. Twenty elective laparoscopic sigmoid colectomies (LSCs) were performed for diverticulitis between April 1992 and July 1999 at a university-affiliated urban hospital. A case-control study was performed comparing LCS with a matched control group of conventional open sigmoidectomies. Fourteen of 20 sigmoidectomies were successfully completed laparoscopically. The mean operative time for LSC was similar to that for open sigmoid colectomy (251 vs 243 minutes). There was earlier return to oral intake in the LSC group (1 vs 5 days; P < 0.001). The mean length of stay was significantly shorter (P = 0.029) in LSC (4.8 days) versus open sigmoid colectomy (7.8 days). Conversion to open sigmoidectomy extended hospital stay to 8.16 days. The overall complication rate was 10 per cent in both groups. We conclude that LSC can be performed effectively and with a low complication rate for diverticular disease. LSC provides the benefit of quicker return of bowel function and shorter hospitalization.

Adult↗
PubMed1999

Hepatitis C virus in peripheral blood mononuclear cells from a chronically infected patient receiving liver graft from infected donor.

BACKGROUND: In hepatitis C virus (HCV)-positive patients receiving HCV-positive liver allografts either the donor or recipient strain overtakes the other strain. Whether these changes are reflected in peripheral blood mononuclear cell (PBMC)-associated virus is unknown. METHODS: We analyzed by single-strand conformation polymorphism and sequencing HCV RNA from serum and PBMCs from a liver transplant recipient whose indigenous strain was replaced by the donor strain. RESULTS: Only the recipient strain was detectable in serum and PBMCs 3 and 5 days after transplantation; at day 7 and 8, a mixture of both was present in the PBMCs, but only recipient strain was detectable in serum. This coincided with the peak presence of donor DNA in recipient PBMCs. From day 14 on, HCV sequences in serum and PBMCs were indistinguishable. CONCLUSIONS: Overtake phenomenon in the setting of liver transplantation from infected donors to infected recipients is manifested in PBMCs. Cells released from infected graft carry donor HCV strain.

Aged↗
PubMed1998

Hepatitis C virus quasispecies in patients infected with HIV-1: correlation with extrahepatic viral replication.

Hepatitis C virus (HCV) sequences recovered from serum, peripheral blood mononuclear cells (PBMCs), and various tissues from human immunodeficiency virus type 1 (HIV-1) positive patients were compared by single strand conformational polymorphism (SSCP) and sequencing. In five patients, paired serum and PBMCs samples were analyzed while in two other patients multiple autopsy tissues were studied. Sequences amplified from the NS5 and E2 regions were consistently identical in the same patient; however, three PBMCs samples and three different tissue samples (pancreas and adrenal gland in one patient and lymph node in the other patient) contained 5' untranslated region (5'UTR) sequences that were different from circulating sequences. The presence of 5' UTR sequences differing from circulating sequences correlated with the presence of HCV RNA negative strand, as the latter was detected by a Tth-based strand-specific assay in all but one of these samples. These two independent lines of evidence: viral sequence differences and the presence of RNA negative strand in the same tissues strongly argue for the genuine presence of extrahepatic HCV replication, at least in the setting of HIV-1 infection.

Base Sequence↗
PubMed1998

Association between hepatitis B virus core promoter rearrangements and hepatocellular carcinoma.

Hepatitis B virus (HBV) is the major etiological agent of hepatocellular carcinoma (HCC). Whether any particular viral variants are associated with HCC is unknown. We studied 53 Gambian patients with HCC and 33 HBsAg positive controls. A functional part of HBV core promoter and whole precore region were sequenced directly and/or after cloning. HBV DNA was amplified from sera from 27 HCC patients and in all controls. Fourteen (52%) patients and 12 (36%) controls (NS) were found to harbor an HBV strain with G to A transition mutation at position 1896 leading to HBeAg negative phenotype. Nine (33%) HCC patients and 2 (6%) controls (p < 0.01) harbored a mixture of wild type and HBV strains with deletions/insertions; strong consensus sequences for topoisomerase I breakage were located in the vicinity of these changes. In Africa, HCC is associated with HBV strains that have deletions/insertions in the HBV core promoter region.

Base Sequence↗
PubMed1998

Search for hepatitis C virus extrahepatic replication sites in patients with acquired immunodeficiency syndrome: specific detection of negative-strand viral RNA in various tissues.

The existence of extrahepatic reservoirs of hepatitis C virus (HCV) replication remains highly controversial. We searched for the presence of HCV-RNA negative strand in various tissues from eight HCV-infected patients who died of acquired immunodeficiency syndrome (AIDS)-related complications. Negative-strand RNA was detected by a Tth-based reverse-transcriptase polymerase chain reaction (RT-PCR), which was optimized for sensitivity and strand specificity on synthetic RNA templates. This assay was capable of detecting about 10(2) genomic Eq molecules of the correct strand while unspecifically detecting >/=10(8) genomic Eq molecules of the incorrect strand. Negative-strand viral RNA was detected in all but one liver, in lymph nodes (5 cases), in pancreas (5 cases), in adrenal gland (2 cases), in thyroid (2 cases), in bone marrow (1 case), and in spleen (1 case). These data suggest a possible presence of HCV replication sites outside the liver, at least in AIDS patients. Whether these findings relate to various extrahepatic manifestations of HCV infection remains to be determined.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Lack of evidence for GB virus C/hepatitis G virus replication in peripheral blood mononuclear cells.

BACKGROUND/AIMS: The recently identified hepatitis G virus (HGV) has been found to be common in patients with various forms of chronic liver disease, particularly chronic hepatitis C. However, replication sites of this new viral agent have not been studied. METHODS: We searched for the presence of HGV RNA in peripheral blood mononuclear cells and serum samples from nine chronic hepatitis C patients coinfected with hepatitis G virus. The presence of negative viral RNA strands was determined by strand-specific Tth-based assay which was optimized on synthetic template. RESULTS: All peripheral blood mononuclear cell samples were negative for the presence of the HGV RNA minus strand and only five were positive for the presence of the positive strand, albeit at a low level of 10-10(2) genomic equivalents/10(6) cells. CONCLUSIONS: These findings imply that hepatitis G virus does not replicate in peripheral blood mononuclear cells, at least in the population of HCV/HGV coinfected patients.

Flaviviridae↗