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Biomedical subjects

R Armenta

Publications and source records attributed to R Armenta.

7 recordsLinked to original sources
PubMed2003

Impact of a nucleopolyhedrovirus bioinsecticide and selected synthetic insecticides on the abundance of insect natural enemies on maize in southern Mexico.

The impact of commonly used organophosphate (chlorpyrifos, methamidophos), carbamate (carbaryl), and pyrethroid (cypermethrin) insecticides on insect natural enemies was compared with that of a nucleopolyhedrovirus (Baculoviridae) of Spodoptera frugiperda (J. E. Smith) (Lepidoptera Noctuidae) in maize grown in southern Mexico. Analyses of the SELECTV and Koppert Side Effects (IOBC) databases on the impact of synthetic insecticides on arthropod natural enemies were used to predict approximately 75-90% natural enemy mortality after application, whereas the bioinsecticide was predicted to have no effect. Three field trails were performed in mid- and late-whorl stage maize planted during the growing season in Chiapas State, Mexico. Synthetic insecticides were applied at product label recommended rates using a manual knapsack sprayer fitted with a cone nozzle. The biological pesticide was applied at a rate of 3 x 10(12) occlusion bodies (OBs)/ha using identical equipment. Pesticide impacts on arthropods on maize plants were quantified at intervals between 1 and 22 d postapplication. The biological insecticide based on S. frugiperda nucleopolyhedrovirus had no adverse effect on insect natural enemies or other nontarget insect populations. Applications of the carbamate, pyrethroid, and organophosphate insecticides all resulted in reduced abundance of insect natural enemies, but for a relatively short period (8-15 d). Pesticide applications made to late-whorl stage maize resulted in lesser reductions in natural enemy populations than applications made at the mid-whorl stage, probably because of a greater abundance of physical refuges and reduced spray penetration of late-whorl maize.

Animals↗
PubMed1990

A silicon sensor-based filtration immunoassay using biotin-mediated capture.

A sensitive sandwich immunoassay for human chorionic gonadotropin (hCG) was developed with biotin-mediated filtration capture and silicon sensor detection. A high density of biotin on the membrane assured efficient capture of complexes containing streptavidin and analyte. Capture efficiency was not affected over a wide range of filtration flow rates or biotin concentrations. The assay utilized the pH sensing ability of the light addressable potentiometric sensor (LAPS) for the detection of urease-antibody conjugates. A LAPS reader was constructed which allowed the enzyme conjugate to be detected in approximately 1 microliter volumes. Effects from variations in detection volume were studied. 10 pg of hCG could be detected in an assay time of 20 min with four standard deviations separation from background. Comparison to a commercial RIA was made.

Antibodies, Monoclonal↗
PubMed1986

Sugiura procedure outside Japan. The Mexican experience.

In the last 10 years, we operated on 231 patients with hemorrhagic portal hypertension. Most of these patients had some form of liver disease. We performed various surgical procedures: 47 conventional shunts with H grafts and terminolateral portacaval shunts with arterialization of the portal stump, 139 selective Warren shunts, and in those patients in whom a selective portasystemic shunt could not be performed for technical reasons, esophagogastric devascularization in the form of the Sugiura procedure. Forty-five patients were treated with the Sugiura procedure as a one stage or two stage procedure. A total of 68 emergency and elective operations were performed. The operative mortality rate for the emergency thoracic operation was 41 percent and for the abdominal operation, 42 percent. The overall operative mortality rate in the emergency group was 41 percent. The incidence of recurrent variceal bleeding and encephalopathy was 0 in the surviving patients. The survival rate at 3 year follow-up was 40 percent. The elective group was made up of 24 patients. Eighteen patients had a two stage procedure and 6 patients had a one stage procedure. The operative mortality rate for the abdominal operation was 11 percent, whereas that for the thoracic operation was 7 percent. The operative mortality rate for the one stage procedure was 16 percent. The overall operative mortality rate in the elective group was 10.8 percent. None of these patients had recurrent variceal bleeding and encephalopathy developed in only one (5 percent). The encephalopathy was easily controlled with medical treatment. The 3 year survival rate was 83 percent. We conclude that the Sugiura procedure is an effective procedure to treat hemorrhagic portal hypertension when a selective shunt cannot be performed.

Adolescent↗
PubMed1985

Improved sensitivity in homogeneous enzyme immunoassays using a fluorogenic macromolecular substrate: an assay for serum ferritin.

A new highly sensitive nonseparation enzyme immunoassay for human serum ferritin is described. Reagents include a beta-galactosidase-ferritin conjugate, sheep anti-ferritin, anti-sheep IgG, and dextran-linked beta-galactosylumbelliferone as enzyme substrate. The method is based on inhibition of enzyme activity when anti-ferritin binds to the enzyme-ferritin conjugate. Ferritin in the sample and enzyme-labeled ferritin compete for a limited quantity of anti-ferritin. The enzyme activity of the reaction mixture is directly related to the ferritin content of the sample. Some patients' samples caused strong interference in the assay due to the presence of antibody to beta-galactosidase. Several ways of eliminating the interference are presented. When measures were adopted to suppress sample interference, the assay results correlated well with those of other immunoassay methods.

Antibody Affinity↗