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Biomedical subjects

L Lopez

Publications and source records attributed to L Lopez.

At least 19 recordsLinked to original sources
PubMed2003

Isolation and characterization of a novel insect defensin from Rhodnius prolixus, a vector of Chagas disease.

An antimicrobial peptide belonging to the defensin family of small cationic peptides associated with innate immunity in insects was isolated from the hemolymph of Rhodnius prolixus, a vector of Chagas disease. This peptide, designated R. prolixus defensin A, was purified and sequenced. The active peptide contains 43 residues and aligns well with other insect defensins. However the pre-pro region of the sequence has little shared identity with other insect defensins. We have identified 3 isoforms of R. prolixus defensin from cDNA clones obtained from RNA isolated from the whole bodies of immune activated insects. Northern analysis and Real-Time Quantitative PCR indicate that there is a very low baseline transcription of this peptide in naïve insects, and that transcription increases significantly in the fat body of immune activated insects. In addition there is a delayed induction of transcription of this peptide in the intestine 24 h post activation suggesting that the midgut/intestine of this species is active in the immune response against pathogens.

Amino Acid Sequence↗
PubMed2003

Phase-locked oscillatory approximately 15- to 30-Hz response to transient visual contrast stimulation: neuromagnetic evidence for cortical origin in humans.

We present neuromagnetic evidence that the human oscillatory (-15-30 Hz; "gamma band") mass response to transient visual (contrast) stimulation originates from cortical areas also generating the conventional pattern-evoked response (VERs). The oscillatory response has shorter latency from stimulus and earlier temporal evolution than the VERs, with different orientation of the source currents. These results suggest the activation of (partly) distinct generating neuronal assemblies with contributions to the development of the VER response. A functional role in stimulus-related cortical synchronization during early visual processing is further suggested and appears consistent with the results of single-unit/multiunit animal research.

Adult↗
PubMed2003

MCP-1 (CCL2) protects human neurons and astrocytes from NMDA or HIV-tat-induced apoptosis.

Acquired immunodeficiency syndrome (AIDS)-associated dementia is often characterized by chronic inflammation, with infected macrophage infiltration of the CNS resulting in the production of human immunodeficiency virus type 1 (HIV-1) products, including tat, and neurotoxins that contribute to neuronal loss. In addition to their established role in leukocyte recruitment and activation, we identified an additional role for chemokines in the CNS. Monocyte chemoattractant protein-1 (MCP-1 or CCL2) and regulated upon activation normal T cell expressed and secreted (RANTES) were found to protect mixed cultures of human neurons and astrocytes from tat or NMDA-induced apoptosis. Neuronal and astrocytic apoptosis in these cultures was significantly inhibited by co-treatment with MCP-1 or RANTES but not IP-10. The protective effect of RANTES was blocked by antibodies to MCP-1, indicating that RANTES protection is mediated by the induction of MCP-1. The NMDA blocker, MK801, also abolished the toxic effects of both tat and NMDA. Tat or NMDA treatment of mixed cultures for 24 h resulted in increased extracellular glutamate ([Glu]e) and NMDA receptor 1 (NMDAR1) expression, potential contributors to apoptosis. Co-treatment with MCP-1 inhibited tat and NMDA-induced increases in [Glu]e and NMDAR1, and also reduced the levels and number of neurons containing intracellular tat. These data indicate that MCP-1 may play a novel role as a protective agent against the toxic effects of glutamate and tat.

AIDS Dementia Complex↗
PubMed2002

Intrinsic changes on automatism, conduction, and refractoriness by exercise in isolated rabbit heart.

We have studied the intrinsic modifications on myocardial automatism, conduction, and refractoriness produced by chronic exercise. Experiments were performed on isolated rabbit hearts. Trained animals were submitted to exercise on a treadmill. The parameters investigated were 1) R-R interval, noncorrected and corrected sinus node recovery time (SNRT) as automatism index; 2) sinoatrial conduction time; 3) Wenckebach cycle length (WCL) and retrograde WCL, as atrioventricular (A-V) and ventriculoatrial conduction index; and 4) effective and functional refractory periods of left ventricle, A-V node, and ventriculoatrial retrograde conduction system. Measurements were also performed on coronary flow, weight of the hearts, and thiobarbituric acid reagent substances and glutathione in myocardium, quadriceps femoris muscle, liver, and kidney, to analyze whether these substances related to oxidative stress were modified by training. The following parameters were larger (P < 0.05) in trained vs. untrained animals: R-R interval (365 +/- 49 vs. 286 +/- 60 ms), WCL (177 +/- 20 vs. 146 +/- 32 ms), and functional refractory period of the left ventricle (172 +/- 27 vs. 141 +/- 5 ms). Corrected SNRT was not different between groups despite the larger noncorrected SNRT obtained in trained animals. Thus training depresses sinus chronotropism, A-V nodal conduction, and increases ventricular refractoriness by intrinsic mechanisms, which do not involve changes in myocardial mass and/or coronary flow.

Animals↗
PubMed2001

Ecological meltdown in predator-free forest fragments.

The manner in which terrestrial ecosystems are regulated is controversial. The "top-down" school holds that predators limit herbivores and thereby prevent them from overexploiting vegetation. "Bottom-up" proponents stress the role of plant chemical defenses in limiting plant depredation by herbivores. A set of predator-free islands created by a hydroelectric impoundment in Venezuela allows a test of these competing world views. Limited area restricts the fauna of small (0.25 to 0.9 hectare) islands to predators of invertebrates (birds, lizards, anurans, and spiders), seed predators (rodents), and herbivores (howler monkeys, iguanas, and leaf-cutter ants). Predators of vertebrates are absent, and densities of rodents, howler monkeys, iguanas, and leaf-cutter ants are 10 to 100 times greater than on the nearby mainland, suggesting that predators normally limit their populations. The densities of seedlings and saplings of canopy trees are severely reduced on herbivore-affected islands, providing evidence of a trophic cascade unleashed in the absence of top-down regulation.

Animals↗
PubMed2001

Secretion pattern, ultrastructural localization and function of extracellular matrix molecules involved in eggshell formation.

The chicken eggshell is a composite bioceramic containing organic and inorganic phases. The organic phase contains, among other constituents, type X collagen and proteoglycans (mammillan, a keratan sulfate proteoglycan, and ovoglycan, a dermatan sulfate proteoglycan), whose localization depends on a topographically defined and temporally regulated deposition. Although the distribution of these macromolecules in the eggshell has been well established, little is known about their precise localization within eggshell substructures and oviduct cells or their pattern of production and function during eggshell formation. By using immunofluorescent and immuno-ultrastructural analyses, we examined the distribution of these macromolecules in oviduct cells at different post-oviposition times. To understand the role of proteoglycan sulfation on eggshell formation, we studied the effects of inhibition of proteoglycan sulfation by treatment with sodium chlorate. We showed that these macromolecules are produced by particular oviduct cell populations and at precise post-oviposition times. Based on the precise ultrastructural localization of these macromolecules in eggshell substructures, the timing of the secretion of these macromolecules by oviduct cells and the effects on eggshell formation caused by the inhibition of proteoglycan sulfation, the putative role of mammillan is in the nucleation of the first calcite crystals, while that of ovoglycan is to regulate the growth and orientation of the later forming crystals of the chicken eggshell.

Animals↗
PubMed2001

Cutaneous hyperpigmentation following venous sclerotherapy treated with deferoxamine mesylate.

BACKGROUND: Cutaneous hyperpigmentation after venous sclerotherapy is an adverse sequelae of difficult management. OBJECTIVE: To evaluate the degree of depigmentation with the use of deferoxamine mesylate (DM) in patients with postsclerotherapy hyperpigmentation treated with polydocanol (POL) for telangiectasias and reticular veins (0.2-5 mm diameter) and varicose veins (5-8 mm diameter). METHODS: The experimental group of 36 female patients (mean age 37 years) was divided in two groups. Group I consisted of 30 patients who were treated with POL at 0.25-0.50% concentration for telangiectasias and reticular veins. Group II consisted of six patients with prolonged postsclerotherapy hyperpigmentation (more than 6 months after treatment) in varicose veins that had been treated with POL at 1.5% concentration each week. Groups I and II were injected with DM 500 mg subcutaneously once a week until 81-100% depigmentation was reached. In group I, DM was injected at the time of sclerotherapy. These groups were compared to their respective control groups with similar conditions but allowing spontaneous depigmentation without DM. Evaluation was undertaken clinically and photographically, and the number of days required to reach the desired depigmentation of 81-100% was determined. RESULTS: When DM was used, depigmentation of 81-100% was observed in group I at 27 days, and for group II in 46 days. In each control group, similar depigmentation was seen at 150 +/- 19 and 255 +/- 11 days, respectively. Comparing results, there was a reduction in the time to depigmentation of 82% for each group (P <.0001). CONCLUSION: The weekly subcutaneous administration of DM 500 mg reduces the time to depigmentation by 82% in patients with postsclerotherapy cutaneous hyperpigmentation treated for telangiectasias and reticular veins and prolonged postsclerotherapy hyperpigmentation in varicose veins. In this study we could not explain why such variability exists in the length of time to spontaneous depigmentation.

Adult↗
PubMed2001

RNA editing of the ribosomal protein S13 transcripts in magnolia and sunflower mitochondria.

To obtain information on ribosomal protein gene content and RNA editing in plant mitochondria, we investigated the conservation of the gene for ribosomal protein S13 (rps13) in the mitochondrial genomes of Magnolia spp. and Helianthus annuus. A complete rps13 open reading frame was identified in the mitochondrial genome of Magnolia and Helianthus. Comparison of genomic and cDNA sequences revealed that transcripts from the mitochondrial rps13 locus in both Magnolia and Helianthus undergo RNA editing suggesting the functionality of the related gene. Six and four editing events in the rps13 transcript population of Magnolia and Helianthus mitochondria, respectively, cause critical changes of codons and, consequently, induce 5 and 3.4% amino acid modifications in the respective genomically-encoded S13 polypeptides. Both editing pattern and efficiency of RNA editing differ in the reverse transcription (RT)-PCR-derived cDNA populations from the rps13 locus from the analyzed plant species with only the Magnolia rps13 being fully edited.

Amino Acid Sequence↗
PubMed2001

Latino AIDS immigrants in the Western Gulf states: a different population and the need for innovative prevention strategies.

Immigrant HIV infected Latinos, and those at highest risk for infection, demonstrate strikingly different patterns of risk behaviors and origins. This complicates the already complex acculturation process impacting their lives. By weaving together immigration and AIDS epidemiological patterns, the impact of tightening immigration policy, and masked sexual behaviors, the authors express concern for a lack of communication with, and lack of health care access for, Latinos in the Western Gulf Coast. To combat this deficit, health care and social workers need to be aware of different social, cultural, and behavioral contexts in Latino populations. Policy makers should support efforts to provide health care workers with skills through appropriate language and cultural sensitivity workshops. HIV prevention strategies specific to Latinos are also discussed.

Acculturation↗
PubMed2001

Effects of serotonin and fluoxetine on blood glucose regulation in two decapod species.

One of the best known crustacean hormones is the crustacean hyperglycemic hormone (CHH). However, the mechanisms involved in hormone release in these animals are poorly understood, and thus constitute the central objective of the present study. Different groups of crustaceans belonging to diverse taxa (Chasmagnathus granulata, a grapsid crab and Orconectes limosus, an astacid) were injected with serotonin, fluoxetine, or a mixture of both, and glycemic values (C. granulata and O. limosus) and CHH levels (O. limosus) were determined after 2 h in either submerged animals or animals exposed to atmospheric air. Both serotonin and fluoxetine caused significant hyperglycemia (P<0.05) after injection into the blood sinus of the two species, an effect enhanced after exposure to atmospheric air. In C. granulata blood glucose increased from 6.1 to 43.3 and 11.4 mg/100 ml in submerged animals and from 5.7 to 55.2 and 22.5 mg/100 ml in air-exposed animals after treatment with serotonin and fluoxetine, respectively. In O. limosus the increases were from 1.2 to 59.7 and 135.2 mg/100 ml in submerged animals and from 2.5 to 200.3 and 193.6 mg/100 ml in air-exposed animals after treatment with serotonin and fluoxetine, respectively. Serotonin and fluoxetine also caused a significant increase in the circulating levels of CHH in O. limosus, from 11.9 to 43 and 45.7 fmol/ml in submerged animals and from 13.2 to 32.6 and 45.7 fmol/ml in air-exposed animals, respectively, thus confirming their action as neuroregulators in these invertebrates.

Animals↗
PubMed2001

Listeriosis: an emerging food-borne disease.

Listeriosis is a serious disease acquired by ingestion of foods contaminated with Listeria monocytogenes. Special populations at risk are individuals who are immunocompromised to some extent. The most common clinical findings include meningitis, septicemia, encephalitis, and intrauterine/cervical infections. Food related listeriosis is an unusual occurrence but it is now being thought of as a new, and emergent illness. Numerous types of food products have been implicated in listeriosis infections, but of particular concern are ready to eat products such as lunchmeats, hotdogs, ham/chicken salad, sausages, and roast beef. However, to ensure food safety, there are several methods employed to detect L. monocytogenes in food products and the severity of listeriosis warrants stringent guidelines in food processing facilities. Nevertheless, proper food preparation and handling must be emphasized and individuals who are at an increased risk for the disease must be apprised on how to prevent the occurrence of infection.

Food Microbiology↗
PubMed2000

Reduction of high-risk behaviors among incarcerated youths: a challenge in prevention.

The adolescent population in America is at increasing risk for acquiring the human immunodeficiency virus (HIV) that causes AIDS (CDC, 1998; 1996; 1994; 1993). Although the total number of reported AIDS cases among adolescents 12 to 19 years of age is, thus far, fairly small, the identified caseload in this age group has increased by over 40% during one year alone. In fact, one-fifth of all reported AIDS cases occur among persons 20 to 29 years of age. Many of these young adults contracted HIV infections as teenagers (CDC, 1996). But the trend is changing. In fact, among younger youths, especially those of African heritage, the infection rates are rapidly increasing (CDC, 1999; CDC, 1998). These increases will require focused attention by all health professionals, and public policy officials (Lai, Tsai, Hardy, 1997; Porter, Oakley, Guthrie & Killion, 1999). The purpose of this current study was to describe risk-related behaviors of incarcerated youths that are significant factors when planning community-based programs for HIV/AIDS prevention. Several research questions were generated in this regard and tested. Several significant findings emerged from the data that indicate that African-American youths incarcerated are at greater risk for development of HIV/AIDS than their other ethnic counterparts.

Adolescent↗
PubMed1999

Synchronized approximately 15.0-35.0 Hz oscillatory response to spatially modulated visual patterns in man.

When suitably stimulated, neurons in the striate visual cortex of cats fire in bursts at 20-60 Hz and the membrane potential oscillates rhythmically in the same frequency range and in phase. These oscillations reflect intrinsic properties of mammalian neurons, occur in coherent spatial patterns that depend on the segregation and stimulus selectivity of stimulated cells, and mediate in long-range synchronization across columns and over large cortical areas of cells responding to the same stimulus property/properties. The pool of activated neurons may be adequate in size to drive cellular oscillations into local fields and mass responses. Accordingly, stimulus-dependent oscillatory activity in the same frequency range was described in man after contrast stimulation. Our results describe oscillatory potentials at approximately 15.0-35.0 Hz that in man are (partly) independent from, and anticipate the occurrence of, the conventional low-frequency visual response evoked by transient, foveal stimulation with spatially-modulated patterns.

Adult↗