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Biomedical subjects

J Rivera

Publications and source records attributed to J Rivera.

At least 127 records · Page 7Linked to original sources
PubMed1997

Assessment of polychlorinated naphthalenes in aquifer samples for drinking water purposes.

Polychlorinated naphthalenes (PCNs) were identified and quantified in water samples collected from the aquifer of the Llobregat river near Barcelona (NE Spain) in order to establish the source and extent of spreading of the contamination. Many of the identified PCNs were well resolved as single peaks on the chromatograms recorded using high resolution gas chromatography combined with electron ionization high resolution mass spectrometry and single-ion monitoring. The profile and pattern of PCNs found in groundwater samples are similar to those of Halowax 1099. The levels of the sum of mono- to octachloronaphthalenes in the water samples ranged from 0.003 microgram/L to 72.9 micrograms/L.

Gas Chromatography-Mass Spectrometry↗
PubMed1997

SUR1 (CSG1/BCL21), a gene necessary for growth of Saccharomyces cerevisiae in the presence of high Ca2+ concentrations at 37 degrees C, is required for mannosylation of inositolphosphorylceramide.

Saccharomyces cerevisiae cells require two genes, CSG1/SUR1 and CSG2, for growth in 50 mM Ca2+, but not 50 mM Sr2+. CSG2 was previously shown to be required for the mannosylation of inositolphosphorylceramide (IPC) to form mannosylinositolphosphorylceramide (MIPC). Here we demonstrate that SUR1/CSG1 is both genetically and biochemically related to CSG2. Like CSG2, SUR1/CSG1 is required for IPC mannosylation. A 93-amino acid stretch of Csg1p shows 29% identity with the alpha-1, 6-mannosyltransferase encoded by OCH1. The SUR1/CSG1 gene is a dose-dependent suppressor of the Ca(2+)-sensitive phenotype of the csg2 mutant, but overexpression of CSG2 does not suppress the Ca2+ sensitivity of the csg1 mutant. The csg1 and csg2 mutants display normal growth in YPD, indicating that mannosylation of sphingolipids is not essential. Increased osmolarity of the growth medium increases the Ca2+ tolerance of csg1 and csg2 mutant cells, suggesting that altered cell wall synthesis causes Ca(2+)-induced death. Hydroxylation of IPC-C to form IPC-D requires CCC2, a gene encoding an intracellular Cu2+ transporter. Increased expression of CCC2 or increased Cu2+ concentration in the growth medium enhances the Ca2+ tolerance of csg1 mutants, suggesting that accumulation of IPC-C renders csg1 cells Ca2+ sensitive.

Amino Acid Sequence↗
PubMed1997

Calcium supplementation and the risk of preeclampsia in Ecuadorian pregnant teenagers.

OBJECTIVE: To determine whether increased calcium intake (2 g/day) in pregnancy is effective in reducing the risk of preeclampsia in pregnant teenagers. METHODS: The present study was a prospective, randomized, double-blind, controlled clinical trial. Two hundred sixty teenaged pregnant girls attending the Hospital Gíneco-Obstétrico Isidro Ayora in Quito, Ecuador, were included. Selection criteria were age less than 17.5 years, nulliparity, first prenatal visit before 20 weeks' gestation, and residency in Quito (2800-m altitude). We used a table of random numbers to assign 125 girls to receive 2000 mg of elemental calcium daily, beginning at 20 weeks of gestation and continuing until delivery; 135 women in the control group received a placebo. Blood pressure (BP) was measured twice every 4 weeks until delivery and at 48 hours after delivery. The diagnosis of preeclampsia was defined as BP greater than 140/90 mmHg on at least two occasions more than 6 hours apart and proteinuria greater than 30 mg/dL (over one cross by dipstick on two occasions 4-24 hours apart). RESULTS: The average daily calcium intake in this population was approximately 51% of the Recommended Dietary Allowance. Calcium supplementation was associated with a significantly decreased risk of preeclampsia (risk reduction 12.35%; P < .001), with 3.2% (n = 4) developing preeclampsia in the treatment group versus 15.5% (n = 21) in the placebo group. Moreover, calcium supplementation led to a reduction in systolic BP of 9.1 mmHg and in diastolic BP of 6.0 mmHg. CONCLUSION: These results suggest that calcium supplementation during pregnancy in populations with low calcium intake is a safe, effective, and inexpensive preventive measure that significantly reduces the risk of preeclampsia.

Adolescent↗
PubMed1997

Differing roles of nitric oxide in the pathogenesis of acute edematous versus necrotizing pancreatitis.

BACKGROUND: Microcirculatory changes and leukocyte-endothelial interaction are both central to the pathogenesis of acute pancreatitis. We studied the effects of nitric oxide (NO) donors (intravenous or inhaled) and NO inhibitors, which affect each of these processes, on markers of experimental mild (edematous) and severe (necrotizing) pancreatitis in rats. METHODS: Mild pancreatitis was induced with intravenous cerulein (n = 100) and severe pancreatitis with intravenous cerulein and intraductal glycodeoxycholic acid (n = 100). Each group was randomly divided into five equal treatment subgroups: control, NO-synthase substrate L-arginine, NO donor sodium nitroprusside, NO-synthase inhibitor N-nitro-L-arginine methyl ester (L-NAME), and NO-inhalation. After 6 hours edema was measured by a wet/dry weight ratio, and pancreatic injury was quantified by tissue levels of trypsinogen activation peptides (TAPs) and by histologic analysis of inflammation and necrosis. RESULTS: In mild pancreatitis (1) both NO donors reduced edema formation (p < 0.001) and also reduced intrapancreatic TAPs (p < 0.03); (2) L-NAME significantly increased tissue TAPs (p < 0.03); and (3) inhaled NO had no effect. In severe pancreatitis (1) both intravenous NO donors reduced edema formation (p < 0.005) and both markedly reduced intrapancreatic TAPs (p < 0.001); (2) L-NAME did not further increase the already high tissue TAPs; and (3) inhaled NO decreased tissue TAPs (p = 0.01). Evaluation of inflammation and necrosis by histologic scoring confirmed the reduction of pancreatic injury by NO donors and worsening with NO-synthase inhibitor. CONCLUSIONS: NO donors have a beneficial effect on edema formation in acute pancreatitis but confer more important protection against ectopic trypsinogen activation, which correlates with mortality, inflammation, and necrosis. Although direct microcirculatory action is likely, the salutary effect of inhaled NO in severe pancreatitis may suggest indirect action on circulating leukocytes, which are thought to potentiate tissue injury.

Amylases↗
PubMed1997

PCDD/PCDF from emission sources and ambient air in northeast Spain.

PCDD/PCDF were detected and quantified in emissions from municipal and industrial waste incinerators. Levels of PCDD/PCDF in ambient air were measured in order to evaluate the possible influence. Identification and quantification were carried out by HRGC/HRMS with isotopic dilution as a quantification method using two different GC columns: J&W DB-5 and J&W DB-DIOXIN.

Air Pollutants↗
PubMed1997

Levels of PCDDs and PCDFs in farm cow's milk located near potential contaminant sources in Asturias (Spain). Comparison with levels found in control, rural farms and commercial pasteurized cow's milks.

Cows milk samples from 12 dairy farms in Spain and 23 samples of pasteurised cows milk were analysed for PCDD/F. Farms located in rural areas without specific dioxin sources (background levels) ranged from 1.3 to 2.47 pg TEQ/g fat basis. These values were slightly lower than those found in milk from the vicinity of potential dioxin emission sources (waste incinerator, chemical and metallurgical industry) and similar to milk near paper industry. The waste incinerator seems to be the emission source with the highest influence on the cows milk gathered in its vicinity. Thus, milk near the waste incinerator exhibited the highest PCDD/F levels, the highest PCDF/PCDD ratio and its congener PCDD pattern showed the highest difference respect to its control point. The PCDD/F average concentrations found in pasteurised commercial milk were lower than those found in raw milk and were comparable to those found in retail milk from other countries.

Animals↗
PubMed1997

Growth retardation starts in the first three months of life among rural Guatemalan children.

OBJECTIVE: We tested the hypothesis that growth faltering in rural Guatemala starts earlier than between 3-6 months of life, as generally assumed. METHODS: The sample included children from the INCAP longitudinal trial (1969-1977), who had adequate birth weight (> -1 s.d.) (n = 79). Two groups were formed according to weight-for-age (WAZ) at 3 y: Group A: WAZ < -2 s.d. (growth-retarded), and Group B: WAZ > or = -2 s.d. Weight increments were computed and sex- and gender-specific deficits in weight increments from 0-36 months were calculated by comparing values of the WHO/CDC reference data. For the period between 0-12 months, weight increments were also compared to velocity standards: (1) the Fels data and (2) the WHO growth curves for breast fed infants. RESULTS: At 3 y of age, growth-retarded children were 3.6 kg smaller than the WHO/CDC median. Depending on the reference data used, between 19 and 34% of the deficit at 3 y of age was due to failure to thrive during the first 3 months of life, an additional 12-19% occurred between 3 and 6 months and 12-25% between 6 and 9 months. By 12 months of age, infants had accumulated 45-80% of their total deficit in weight at 3 y of age. Compared to group B, children from group A had greater morbidity during their first 9 months of life, and their mothers had poorer nutritional status at 3 months postpartum. There were indications that children from group A came from more deprived families. CONCLUSIONS: Growth faltering starts soon after birth in rural Guatemala and thus, effective interventions should be targeted to mothers and their infant as early as possible during the first year.

Aging↗
PubMed1997

The venous thrombosis risk factor 20210 A allele of the prothrombin gene is not a major risk factor for arterial thrombotic disease.

A nucleotide change (G to A transition) at position 20210 has recently been demonstrated to be a risk factor for venous thrombosis. The relevance of this polymorphism to thrombotic disease was investigated by genotypic identification in three prospective case-control studies: 101 case patients with acute coronary heart disease (CHD), 104 patients with acute cerebrovascular disease (CVD), 82 patients with a confirmed diagnosis of deep venous thrombosis (DVT), and one control age- and sex-matched for each patient. The prevalence of the genetic variation was significantly associated with the occurrence of DVT, but did not differ in patients with CHD or CVD from that in controls, suggesting that this allele should not be considered a major risk factor for arterial thrombotic disease.

Adult↗
PubMed1997

Loss of high-affinity thrombin receptors during platelet concentrate storage impairs the reactivity of platelets to thrombin.

BACKGROUND: The storage of platelet concentrates (PCs) induces a reduction in the platelet surface expression of glycoprotein (GP) Ib alpha. The location of the platelets' high-affinity binding site for thrombin has been postulated as being located on GPIb alpha. This study attempts to determine whether loss or alteration of GPIb alpha during storage of PCs is related to impairment in the reactivity of platelets to thrombin. STUDY DESIGN AND METHODS: In this study, platelet surface expression of GPIb alpha was monitored by means of flow cytometry, throughout standard storage of PCs for up to 10 days. Two thrombin-induced platelet responses, the binding of radiolabeled fibrinogen and the platelet surface expression of P-selectin, were evaluated. Thrombin-binding assays were also performed to assess the number of thrombin receptors in platelets. RESULTS: The surface expression of the GPIb/IX complex declines during storage of PCs. The thrombin-induced maximal binding of fibrinogen in platelets stored for 3, 7, and 10 days was 77 +/- 7 percent, 60 +/- 20 percent, and 34 +/- 25 percent, respectively, of that found in fresh platelets. Moreover, the concentration of thrombin needed for 50 percent of platelets to express the CD62 antigen P-selectin at the surface increased from 0.05 U per mL in fresh platelets to 0.11, 0.56, and 1.2 U per mL in platelets stored for 3, 7, and 10 days, respectively. Thrombin-binding experiments demonstrated a significant reduction in the number of high-affinity binding sites throughout storage of PCs (55 +/- 21 sites/platelet in 10-day-stored platelets vs. 73 +/- 25 in fresh platelets). A significant correlation was also observed between the number of high-affinity thrombin-binding sites and surface expression of GPIb alpha. Selective blockage of the thrombin-binding site on GPIb alpha with monoclonal antibody LJ-Ib10 also inhibited the response of fresh platelets to thrombin, up to a level equivalent to that found in 3-day-stored platelets. CONCLUSION: The loss of the GPIb alpha-located high-affinity thrombin-binding site may impair the ability of platelets to become activated by thrombin as storage time increases.

Antibodies, Monoclonal↗
PubMed1997

Fibromyalgia-associated hepatitis C virus infection.

The objective was to determine whether there might be an association between hepatitis C virus (HCV) chronic infection and fibromyalgia (FM). We determined the prevalence of HCV infection in 112 FM patients, in comparison with matched rheumatoid arthritis (RA) patients from the out-patient clinic of a teaching tertiary care general hospital. Furthermore, we looked for evidence of FM in 58 patients diagnosed with chronic hepatitis due to HCV, compared with matched surgery clinic patients, HCV antibodies were determined by enzyme-linked immunosorbent assay (ELISA) and recombinant immunoblot assay (RIBA). Serum RNA of HCV (HCV-RNA) was determined by polymerase chain reaction. In the group of FM patients, HCV antibodies were found by ELISA in 17 (15.2%) patients and in six (5.3%) of the RA controls (P < 0.05). RIBA was positive in 16 and indeterminate in one of the FM patients. Serum HCV-RNA was found in 13 of these FM patients. In eight (47%) FM patients, alanine aminotransferase (ALT) was normal, although HCV-RNA was detected in four (50%) of them. In the group of patients with chronic hepatitis due to HCV, all patients had HCV antibodies and the presence of HCV-RNA in serum. Within these patients, 31 (53%) had diffuse musculoskeletal pain, while six (10%) fulfilled FM diagnostic criteria. In the control group, 13/58 (22%) had diffuse musculoskeletal pain (P < 0.001), whereas only one female patient (1.7%) fulfilled FM criteria (P < 0.05). Serum ALT was 51.7 +/- 38.4 in FM patients, whereas it was 122 +/- 76.3 in patients with HCV chronic hepatitis but without FM (P < 0.001). There were no statistical differences in autoimmune markers between patients with and without FM. These data suggest that there exists an association between FM and active HCV infection in some of our patients. FM is not associated with liver damage or autoimmune markers in these patients. HCV infection should be considered in FM patients even though ALT elevations were absent.

Adult↗
PubMed1997

HPA-1 genotype in arterial thrombosis--role of HPA-1b polymorphism in platelet function.

Recently, the HPA-1b (PlA2) polymorphism of the platelet glycoprotein IIIa has been suggested as a genetic risk factor for coronary artery disease. We conducted two case-control studies of 103 patients with ischaemic cerebrovascular disease (CVD) and 101 patients with ischaemic heart disease (IHD). The groups were matched for age, race and sex. No significant differences regarding selected risk factors (hypertension, diabetes mellitus, hypercholesterolaemia and smoking) were found between case patients and controls. Moreover, we investigated 286 normal individuals from the Mediterranean area. Genotyping of HPA-1 was performed by PCR-allelic specific restriction and single-strand conformation polymorphism analysis. The prevalence of HPA-1b was similar among case patients and controls (29.2% vs. 25.3% and 26.7% vs. 34.6% for CVD and IHD case-control studies, respectively). The HPA-1b allele was found in 36.4% of the normal population. Finally, the analysis of platelet function in nine controls with the three possible HPA-1 genotypes (three a/a, three a/b and three b/b) indicates that HPA-1b genotype does not modify either the in vitro platelet aggregation and activation profile, nor the GP IIb/IIIa interaction with fibrinogen or von Willebrand factor. Our results do not support the role of HPA-1b polymorphism as an inherited risk factor for arterial thrombotic disease.

Adult↗
PubMed1997

Phenomenological study of nurses caring for dying patients.

Little is known about how nurses experience caring for dying patients. Yet, entering the patient's world often involves dealing with death and dying and is a major challenge to oncology nurses. The purpose of this article is to describe the shared practices of oncology nurses caring for dying patients. Stories from staff nurses on an oncology unit were analyzed using a hermeneutic method to identify and describe four themes: knowing the patient, preserving hope, easing the struggle, and providing for privacy. The four themes contribute to knowledge development about how nurses enter into and experience caring for dying patients. The growing body of knowledge previously reported has included descriptions of critical behaviors in caring for dying patients, coping strategies nurses used when caring for dying patients and their families, and the meaning of oncology nursing practice. The four themes described in this article expand our understanding of the nurses' experience in caring for dying patients.

Adaptation, Psychological↗
PubMed1997

[Obstetric hysterectomy. Review of 675 cases at the Instituto Nacional de Perinatología].

A retrospective study of 675 patients subject to obstetric hysterectomy from January 1st, 1985 to December 31st, 1995 at the Instituto Nacional de Perinatología was carried out. The incidence of this procedure reached its highest level in patients from 26 to 40 years, which represented 60.5% (409 cases) of the studied population. Patients with one previous cesarean section comprised 34.8% of total obstetric hysterectomies, followed by women with two to three previous cesarean sections (24.5% and 22.2%, respectively). As for gestational age, it reached term in 51.1% (345 cases), pre-term in 38% (257), post-term in 1.4% (10), and less than 20 weeks in 9.3% (63 cases). Main indications for obstetric hysterectomy included placenta accreta in 34.07% (230 cases), uterine atony in 32.4% (219), deciduomyometritis in 6.3% (43 cases), and uterine rupture in 4.5% (31). Most frequent complications included hypovolemia (12.1%), bladder injury (5.4%), and ureteral injury (0.7%). Postoperative complications included anemia (61.6%), febrile syndrome (7.5%), mechanic ileum (7.5%), wall abscess (3.4%), and vesicovaginal fistula (1.6%). A total of eight maternal deaths (1.1%) was reported.

Adolescent↗
PubMed1997

Rheumatologic and autoimmune manifestations in patients with chronic hepatitis C virus infection.

Hepatitis C virus (HCV) has been associated with several autoimmune and rheumatologic disorders. The aim of this study was to determine the incidence of these abnormalities in patients with chronic HCV. We studied 56 patients, 29 of whom (52%) had biochemical abnormalities that suggested immunological disorders. Cryoglobulinemia was detected in nine patients (22%), antinuclear antibodies in eleven (20%), rheumatoid factor in seven (19.27%) and hypocomplementemia in fourteen (29.16%). The most common clinical manifestations were: arthralgias (52%), myalgias (16%), xerostomia (28.5%) and xerophthalmia (14%). These results indicate the existence of a relationship between HCV and rheumatologic disorders. We conclude that HCV may play a role in the pathogenesis of these autoimmune phenomena, but more studies are required to define the extent of this role.

Adult↗
PubMed1996

Association of a p95 Vav-containing signaling complex with the FcepsilonRI gamma chain in the RBL-2H3 mast cell line. Evidence for a constitutive in vivo association of Vav with Grb2, Raf-1, and ERK2 in an active complex.

Aggregation of the high affinity receptor for IgE (FcepsilonRI) on the mucosal mast cell line, RBL-2H3, results in the rapid and persistent tyrosine phosphorylation of Vav. Immunoprecipitation of Vav from activated cells revealed co-immunoprecipitated phosphoproteins of molecular weights identical to the FcepsilonRI beta and gamma chains, and the former was reactive with antibody to the FcepsilonRI beta chain. Conversely, Western blots revealed the presence of p95 Vav in FcepsilonRI immunoprecipitates. The association of Vav and of Grb2 with the receptor was found to be regulated by aggregation of the receptor, and the interaction of Vav with the FcepsilonRI was localized to the gamma chain. To gain insight on the signaling pathway in which Vav participates, we investigated the in vivo associations of Vav with other molecules. A reducible chemical cross-linking agent was used to covalently maintain protein interactions under nonreducing conditions. A fraction of Vav increased in mass to form a complex of >300 kDa in molecular mass. Under reducing conditions the cross-linked Vav immunoprecipitates showed the presence of Grb2, Raf-1, and p42(mapk) (ERK2). In vitro kinase assays of Raf-1 activity associated with Vav revealed that this complex had an activity greater than that of Raf-1 derived from nonactivated cells, and aggregation of the FcepsilonRI did not modulate this activity. In contrast, aggregation of the FcepsilonRI increased the total Raf-1 activity by 2-5-fold. These results demonstrate that Vav associates constitutively with components of the mitogen-activated protein kinase pathway to form an active multimeric signaling complex whose in vivo activity and associations may be directed by aggregation of the FcepsilonRI. The findings of this study may also be relevant to other members of the immune recognition receptor family that share the T-cell antigen receptor zeta/gamma chains.

Adaptor Proteins, Signal Transducing↗