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J L Herrera

Publications and source records attributed to J L Herrera.

At least 19 recordsLinked to original sources
PubMed2006

Local versus global interactions in nonequilibrium transitions: A model of social dynamics.

A nonequilibrium system of locally interacting elements in a lattice with an absorbing order-disorder phase transition is studied under the effect of additional interacting fields. These fields are shown to produce interesting effects in the collective behavior of this system. Both for autonomous and external fields, disorder grows in the system when the probability of the elements to interact with the field is increased. There exists a threshold value of this probability beyond which the system is always disordered. The domain of parameters of the ordered regime is larger for nonuniform local fields than for spatially uniform fields. However, the zero field limit is discontinous. In the limit of vanishingly small probability of interaction with the field, autonomous or external fields are able to order a system that would fall in a disordered phase under local interactions of the elements alone. We consider different types of fields which are interpreted as forms of mass media acting on a social system in the context of Axelrod's model for cultural dissemination.

Journal Article↗
PubMed2005

Influence of the oceanographic conditions during spring 2003 on the transport of the Prestige tanker fuel oil to the Galician coast.

Hydrographic data collected during the cruise HIDROPRESTIGE were combined with meteorological and dynamic data provided by remote sensors and drifting/moored buoys, to describe the surface circulation of the Northern Iberian basin in March-April 2003. Sea surface winds transported the floating Prestige oil slicks from the sinking area to the continental slope off the Rías Baixas in 1/2 month: the surface current intensity was 2% of the wind intensity and it was rotated clockwise 5 degrees from the wind direction. Mesoscale cyclonic and anticyclonic structures west of 10 degrees W increased the residence time of oil patches in the Northern Iberian basin, as compared with the expected southwards flow of the Iberian current (IC). On the other hand, the Iberian poleward current (IPC) formed a marked surface front with coastal waters, preventing the entry of fuel oil into the rías. PAHs in the surface layer during the cruise were <0.5 microgL(-1), except in the Galicia bank (approximately 1 microg L(-1); where the Prestige tanker was still leaking) and the vicinity of Cape Fisterra (approximately 1.5 microg L(-1); where the convergence front between the IPC and coastal waters vanished).

Atlantic Ocean↗
PubMed2001

Analysis of sweet diterpene glycosides from Stevia rebaudiana: improved HPLC method.

An improved analytical method was developed which may be applied to quality control of stevioside and rebaudioside A contents in dried leaves of Stevia rebaudiana before processing; in a selective sampling program searching for plants of higher yield in diterpene glycosides content; or when a large number of samples are sent to the laboratory for analysis. The procedure developed involves two steps: solvent extraction followed by an isocratic HPLC analysis. The sample, 1 g of dried leaves of S. rebaudiana, is ground and solvent-extracted with EtOH 70% (w/w) in Erlenmeyer flasks by shaking for 30 min in a 70 degrees C water bath. After the extract was cooled, it was filtered and analyzed by HPLC using an NH(2) column (250 x 4.6 mm) and a mixture of acetonitrile/water (80:20, v/v) as mobile phase, pH 5 adjusted with acetic acid. The detection was in the UV range at 210 nm (0.04 AUFS). Quantitation was performed by means of an external standard calibration curve for each analyte which had been obtained from standard solutions of pure stevioside and rebaudioside A. Working under these conditions there were no observed interference effects. The method saves time in sample preparation, and reduces sample handling and chromatographic analysis time, while having little loss of precision [coefficient of variation (CV%) between 1.8% and 3.0%] and recovery [between 98.5% and 100.5%]. The method was applied to 30 samples of S. rebaudiana from Misiones (Northeastern Argentina), and the stevioside content found ranged between 3.78 and 9.75% (weight) whereas Rebaudioside A content ranged between 1.62 and 7.27% (weight).

Chromatography, High Pressure Liquid↗
PubMed2001

Chronic hepatitis C: implications for the primary care clinician.

The seeds of an epidemic were sown 2 decades ago, and PAs need to be alert for those at risk for developing chronic hepatitis C before cirrhosis, liver failure, or liver cancer develops. Identifying the patient at risk is as uncomplicated as asking the right questions in the right setting.

Hepatitis C, Chronic↗
PubMed2000

Biliary cystadenoma: rare variant of intrahepatic cystic disease.

Intrahepatic nonparasitic cystic disease is rare and may be of congenital or neoplastic origin. The most frequent symptoms and signs are nonspecific and include pain, nausea, fullness, increased girth, and palpable mass. Interventional therapy is reserved for symptomatic patients, which usually corresponds to cysts >5 cm in diameter. Retrospective analysis revealed 26 cases of intrahepatic cystic disease over 15 years at our institution. We discuss the case of a patient who had bilobular biliary cystadenomatous disease, a rare, benign variant of intrahepatic nonparasitic cystic disease.

Abdominal Pain↗
PubMed1999

Iron depletion is not effective in inducing a virologic response in patients with chronic hepatitis C who failed to respond to interferon therapy.

OBJECTIVE: Some studies have suggested that increased iron stores may impact negatively on the response to interferon in patients with chronic hepatitis C infection. We performed this prospective trial to determine the effects of iron depletion on ALT and HCV-RNA levels in patients with chronic hepatitis C infection and to assess whether the response to interferon in patients who had previously failed to respond to interferon was enhanced by iron depletion. METHODS: Patients with chronic hepatitis C resistant to interferon therapy and no evidence of iron overload underwent weekly phlebotomies until the serum ferritin level was below lower limits of normal for the subject's age and sex. Patients were then started on interferon-alpha2b, 3 million units subcutaneously three times per week for a period of 24 weeks. Iron studies, ALT, and HCV-RNA levels were monitored at baseline, after phlebotomy and at 12 and 24 weeks of interferon therapy. RESULTS: Thirty-three patients were enrolled, 28 completed the study. A mean of 7.2 units of blood were removed to achieve iron depletion. ALT levels decreased significantly with phlebotomy (142 IU/L before phlebotomy vs 82 IU/L after phlebotomy; p < 0.001), but log HCV-RNA levels remained unchanged (6.49 before phlebotomy vs 6.51 after phlebotomy). Interferon therapy did not improve ALT levels further. HCV-RNA levels were minimally reduced during interferon therapy (log HCV-RNA 6.49 before interferon vs 6.00 after 24 weeks of interferon therapy). Two patients achieved a virologic end of treatment response, both relapsed within 3 months after discontinuation of interferon. No patient achieved a sustained virologic response. CONCLUSIONS: In patients who previously failed treatment with interferon, iron depletion induced by phlebotomy improves ALT levels but is ineffective in achieving viral eradication in patients retreated with interferon 3 million units three times per week.

Adult↗
PubMed1998

Immune globulin and vaccine therapy to prevent hepatitis A infection.

The hepatitis A virus is usually transmitted person-to-person due to fecal-oral exchange of virus. Approximately 30,000 infections are reported each year in the United States, with the actual incidence being much greater. Prophylaxis with immune globulin has had a minimal impact on the overall incidence of hepatitis A. The recent availability and proven efficacy of a hepatitis A vaccine offers the hope that the incidence of infection may be substantially reduced. Pre- and postexposure prophylaxis should be targeted to individuals at increased risk of either acquiring infection, transmitting infection, or developing fulminant hepatitis, or to help control epidemics. This article reviews the current literature and discusses recommendations for pre- and postexposure prophylaxis against hepatitis A virus.

Adult↗
PubMed1997

Vibrio vulnificus infection: an important cause of septicemia in patients with cirrhosis.

Vibrio vulnificus, a virulent gram-negative organism, is a normal inhabitant of coastal waters, including the Gulf of Mexico. Vibrio vulnificus infection has been recognized as a cause of fatal septicemia in chronically ill patients, particularly those with chronic liver disease. We report the case of a patient with chronic liver disease who had V vulnificus septicemia 2 days after eating raw oysters harvested in the Gulf Coast. Vibrio vulnificus septicemia should be suspected in all patients with underlying medical illnesses, particularly cirrhosis, who present with a febrile illness days after eating seafood or being exposed to saltwater. Physicians should advise their patients with cirrhosis and other chronic debilitating illnesses not to eat raw or undercooked seafood.

Adult↗
PubMed1997

Management of ascites. Paracentesis as a guide.

All patients with new-onset ascites or with known ascites and any change in their condition, such as the appearance of fever, abdominal pain, renal insufficiency, or encephalopathy, should undergo diagnostic paracentesis to characterize the ascitic fluid, detect infection, and aid differential diagnosis. A serum-ascites albumin gradient greater than 1.1 g/dL indicates portal hypertension. Spontaneous bacterial peritonitis is a common and serious complication of ascites and is best diagnosed by the number of neutrophils in the ascitic fluid. Patients with the condition should be treated with parenteral antibiotics, and response to therapy should be assessed with repeated paracentesis. Hospitalized patients with low-protein ascites should receive antibiotic prophylaxis. Sodium restriction and diuretics are the cornerstones of therapy for ascites. In refractory cases, alternative forms of therapy, such as large-volume paracentesis, peritoneovenous shunting, or transjugular intrahepatic portosystemic shunting, may be of benefit. Patients with refractory ascites should be considered for liver transplantation.

Anti-Infective Agents↗
PubMed1995

Effect of radiation and radioprotection on small intestinal function in canines.

Radiation with doses > 7.5 Gy damages the canine intestinal mucosa, and pretreatment with WR2721 reduces this damage. However, the effects of radiation and of WR2721 on in vivo intestinal transport are unclear. Therefore, we determined canine survival, intestinal transport, and mucosal histology following unilateral abdominal irradiation. Isoperistaltic ileostomies were prepared in 23 dogs under general anesthesia and aseptic conditions. After a three-week recovery period, animals were given either placebo or WR2721, 150 mg/kg intravenously, 30 min prior to 10 Gy cobalt-60 abdominal irradiation. Ileal transport and histology were determined in both groups before exposure and one, four, and seven days after irradiation. Seven-day survival was significantly improved by pretreatment with WR2721 (91% vs 33%, P < 0.02). On day 4, both mucosal integrity and net intestinal absorption were significantly better (P < 0.05) after WR2721 than after placebo. Thus, radiation-induced damage to the ileal mucosa is accompanied by a reduction in net ileal absorption of water and electrolytes in vivo. In addition, pretreatment with WR2721 improves animal survival while reducing ileal damage and improving intestinal absorption.

Amifostine↗
PubMed1995

Alfentanil for conscious sedation during colonoscopy.

This investigation was designed to determine whether the narcotic alfentanil, a relatively new fentanyl derivative with rapid onset of action and offset of activity, alone or in combination with midazolam has advantages over the traditional meperidine and midazolam regimen for conscious sedation. Thirty-five subjects were randomized to receive an initial dose of narcotic and sedative with additional narcotics or sedatives administered as needed. Subjects receiving no midazolam sedative (alfentanil and placebo group, n = 13) had less desaturation and had the need for supplemental oxygen less often than those receiving alfentanil and midazolam (n = 11) or meperidine and midazolam (n = 11). There were no differences as assessed by patient and colonoscopist for tolerance and discomfort, procedure ease, recovery time, complications, electrocardiogram, and blood pressure. Baseline evaluation did not predict the need for supplemental oxygen. We concluded that alfentanil, with or without a sedative, has no advantage over the commonly used meperidine and midazolam regimen.

Adult↗