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Pantazis LJ, García RA. Detection of atypical response trajectories in biomedical longitudinal databases. Int J Biostat 2023; 19:389-415. [PMID: 36279154 DOI: 10.1515/ijb-2020-0076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 10/03/2022] [Indexed: 11/15/2023]
Abstract
Many health care professionals and institutions manage longitudinal databases, involving follow-ups for different patients over time. Longitudinal data frequently manifest additional complexities such as high variability, correlated measurements and missing data. Mixed effects models have been widely used to overcome these difficulties. This work proposes the use of linear mixed effects models as a tool that allows to search conceptually different types of anomalies in the data simultaneously.
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Affiliation(s)
- Lucio José Pantazis
- ITBA, Buenos Aires, Lavardén 315, CP 1437, Argentina
- CESyC, Department of Mathematics, Instituto Tecnológico de Buenos Aires, Lavardén 315, Buenos Aires, 1437, Argentina
| | - Rafael Antonio García
- ITBA, Buenos Aires, Lavardén 315, CP 1437, Argentina
- CESyC, Department of Mathematics, Instituto Tecnológico de Buenos Aires, Lavardén 315, Buenos Aires, 1437, Argentina
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Castro-Montoya JM, García RA, Ramos RA, Flores JM, Alas EA, Corea EE. Dairy cows fed on tropical legume forages: effects on milk yield, nutrients use efficiency and profitability. Trop Anim Health Prod 2018; 50:837-843. [PMID: 29297107 DOI: 10.1007/s11250-017-1505-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2017] [Accepted: 12/17/2017] [Indexed: 10/18/2022]
Abstract
Two trials with multiparous dairy cows were conducted. Experiment 1 tested the effects of increasing forage proportion in the diet (500, 600, and 700 g/kg DM) when a mixed sorghum (Sorghum bicolor) and jackbean (Cannavalia ensiformis) silage was used as forage. Experiment 2 studied the substitution of sorghum silage and soybean meal by jackbean silage or fresh cowpea (Vigna unguiculata) forage in the diet. All diets were iso-energetic and iso-proteic. In each experiment, 30 cows were used and separated into three groups. In experiment 1, there were no differences in dry matter intake (DMI), milk yield (MY), or apparent total tract digestibility (aTTd) among the three diets, but milk fat content increased with increasing forage proportion, even though the similar neutral detergent fiber of all diets. Nitrogen use efficiency was highest in the diet containing 600 g forage/kg DM, and some evidence was observed for a better profitability with this forage proportion. In experiment 2, feeding legumes increased DMI despite no effects on aTTd. Milk yield increased in line with DMI, with a larger increase for the fresh cowpea. Nitrogen use efficiency and milk composition were not affected by the diets. The increased MY and lower feed costs increased the economic benefits when feeding legumes, particularly when feeding fresh cowpea. Feeding fresh cowpea or jackbean silage to dairy cows appears to be an alternative to soybean as protein source, ideally at a forage proportions of 600 g/kg DM, without altering milk yield and quality and increasing the farm profitability.
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Affiliation(s)
- J M Castro-Montoya
- Institute of Agricultural Sciences in the Tropics, Animal Nutrition and Rangeland Management in the Tropics and the Subtropics, Hohenheim University, Fruwirthstrasse 31, Stuttgart, Germany
| | - R A García
- Faculty of Agricultural Sciences, University of El Salvador, Final 25 av N, San Salvador, El Salvador
| | - R A Ramos
- Faculty of Agricultural Sciences, University of El Salvador, Final 25 av N, San Salvador, El Salvador
| | - J M Flores
- Faculty of Agricultural Sciences, University of El Salvador, Final 25 av N, San Salvador, El Salvador
| | - E A Alas
- Faculty of Agricultural Sciences, University of El Salvador, Final 25 av N, San Salvador, El Salvador
| | - E E Corea
- Faculty of Agricultural Sciences, University of El Salvador, Final 25 av N, San Salvador, El Salvador.
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Figueredo AJ, Cabeza de Baca T, Fernandes HBF, Black CJ, Peñaherrera M, Hertler S, García RA, Meisenberg G, Woodley of Menie MA. A Sequential Canonical Cascade Model of Social Biogeography: Plants, Parasites, and People. Evolutionary Psychological Science 2016. [DOI: 10.1007/s40806-016-0073-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Figueredo AJ, de Baca TC, Black CJ, García RA, Fernandes HBF, Wolf PSA, Anthony M. Methodologically Sound: Evaluating the Psychometric Approach to the Assessment of Human Life History [Reply to ]. Evol Psychol 2015. [DOI: 10.1177/147470491501300202] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Copping, Campbell, and Muncer (2014) have recently published an article critical of the psychometric approach to the assessment of life history (LH) strategy. Their purported goal was testing for the convergent validation and examining the psychometric structure of the High-K Strategy Scale (HKSS). As much of the literature on the psychometrics of human LH during the past decade or so has emanated from our research laboratory and those of close collaborators, we have prepared this detailed response. Our response is organized into four main sections: (1) A review of psychometric methods for the assessment of human LH strategy, expounding upon the essence of our approach; (2) our theoretical/conceptual concerns regarding the critique, addressing the broader issues raised by the critique regarding the latent and hierarchical structure of LH strategy; (3) our statistical/methodological concerns regarding the critique, examining the validity and persuasiveness of the empirical case made specifically against the HKSS; and (4) our recommendations for future research that we think might be helpful in closing the gap between the psychometric and biometric approaches to measurement in this area. Clearly stating our theoretical positions, describing our existing body of work, and acknowledging their limitations should assist future researchers in planning and implementing more informed and prudent empirical research that will synthesize the psychometric approach to the assessment of LH strategy with complementary methods.
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Affiliation(s)
- Aurelio José Figueredo
- Department of Psychology, School of Mind, Brain and Behavior, College of Science, University of Arizona, Tucson, AZ, USA
| | - Tomás Cabeza de Baca
- Health Psychology, Department of Psychiatry, University of California, San Francisco, CA, USA
| | - Candace Jasmine Black
- Department of Psychology, School of Mind, Brain and Behavior, College of Science, University of Arizona, Tucson, AZ, USA
| | - Rafael Antonio García
- Department of Psychology, School of Mind, Brain and Behavior, College of Science, University of Arizona, Tucson, Arizona, USA
| | | | - Pedro Sofio Abril Wolf
- Department of Psychology and Centre for Social Science Research, University of Cape Town, Cape Town, Western Cape, South Africa
| | - Michael Anthony
- Woodley of Menie, Center Leo Apostel for Interdisciplinary Studies, Vrije Universiteit Brussel, Brussels, Belgium
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Figueredo AJ, de Baca TC, Black CJ, García RA, Fernandes HBF, Wolf PSA, Anthony M. Methodologically sound: Evaluating the psychometric approach to the assessment of human life history [reply to Copping, Campbell, and Muncer, 2014]. Evol Psychol 2015; 13:299-338. [PMID: 25844774 PMCID: PMC4845720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Accepted: 01/04/2014] [Indexed: 06/04/2023] Open
Abstract
Copping, Campbell, and Muncer (2014) have recently published an article critical of the psychometric approach to the assessment of life history (LH) strategy. Their purported goal was testing for the convergent validation and examining the psychometric structure of the High-K Strategy Scale (HKSS). As much of the literature on the psychometrics of human LH during the past decade or so has emanated from our research laboratory and those of close collaborators, we have prepared this detailed response. Our response is organized into four main sections: (1) A review of psychometric methods for the assessment of human LH strategy, expounding upon the essence of our approach; (2) our theoretical/conceptual concerns regarding the critique, addressing the broader issues raised by the critique regarding the latent and hierarchical structure of LH strategy; (3) our statistical/methodological concerns regarding the critique, examining the validity and persuasiveness of the empirical case made specifically against the HKSS; and (4) our recommendations for future research that we think might be helpful in closing the gap between the psychometric and biometric approaches to measurement in this area. Clearly stating our theoretical positions, describing our existing body of work, and acknowledging their limitations should assist future researchers in planning and implementing more informed and prudent empirical research that will synthesize the psychometric approach to the assessment of LH strategy with complementary methods.
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Affiliation(s)
- Aurelio José Figueredo
- Department of Psychology, School of Mind, Brain and Behavior, College of Science, University of Arizona, Tucson, AZ, USA
| | - Tomás Cabeza de Baca
- Health Psychology, Department of Psychiatry, University of California, San Francisco, CA, USA
| | - Candace Jasmine Black
- Department of Psychology, School of Mind, Brain and Behavior, College of Science, University of Arizona, Tucson, AZ, USA
| | - Rafael Antonio García
- Department of Psychology, School of Mind, Brain and Behavior, College of Science, University of Arizona, Tucson, Arizona, USA
| | | | - Pedro Sofio Abril Wolf
- Department of Psychology and Centre for Social Science Research, University of Cape Town, Cape Town, Western Cape, South Africa
| | - Michael Anthony
- Woodley of Menie, Center Leo Apostel for Interdisciplinary Studies, Vrije Universiteit Brussel, Brussels, Belgium
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Arévalo JF, Fernández CF, Mendoza AJ, García RA, Arévalo FA. [Intravitreal triamcinolone combined with grid laser photocoagulation for patients with cystoid macular edema and advanced diabetic retinopathy: pilot study]. ACTA ACUST UNITED AC 2013; 88:373-9. [PMID: 24060300 DOI: 10.1016/j.oftal.2013.01.020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2010] [Revised: 12/21/2012] [Accepted: 01/25/2013] [Indexed: 11/15/2022]
Abstract
BACKGROUND To determine if primary intravitreal injection of triamcinolone acetonide (TA) plus grid laser photocoagulation (GLP) is effective in treating cystoid diabetic macular edema (DME). METHODS Prospective comparative non-randomized clinical trial. Fourteen eyes (14 patients) diagnosed with cystoid DME were treated with GLP according to the Early Treatment Diabetic Retinopathy Study (ETDRS) guidelines, plus an intravitreal injection of 4 mg of TA. A matched control group (16 eyes [16 patients]) treated with GLP was selected retrospectively from our medical records. Best-corrected visual acuity (BCVA), and quantitative change in optical coherence tomography (OCT) macular thickness were assessed. RESULTS Mean follow up was 14.9 months (12 to 19 months). In 3 (21.4%) eyes BCVA increased > 2 ETDRS lines, in 5 (35.7%) eyes BCVA remained the same, and BCVA decreased >2 ETDRS lines in 6 (42.8%) eyes. Central macular thickness, as measured by OCT, decreased a mean of 106.2 μm (30.2%). The difference with the control group was not statistically significant (P = .2). Four (28.5%) eyes developed an increased in intraocular pressure in our study group. CONCLUSIONS Although all of our patients showed an improvement of cystoid DME by means of OCT and fluorescein angiography, 42.8% (6 eyes) lost 2 or more lines in BCVA with primary intravitreal injection of TA plus GLP. Primary intravitreal injection of TA plus GLP may not be effective for cystoid DME at 12-months.
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Affiliation(s)
- J F Arévalo
- División de Retina, Wilmer Eye Institute, Escuela de Medicina de la Universidad de Johns Hopkins, Baltimore, MD, EE. UU.; King Khaled Eye Specialist Hospital, Riad, Arabia Saudí.
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Ramió HV, Mathur S, Régulo C, García RA. Effect of line-of-sight inclinations on the observation of solar activity cycle: Lessons for CoRoT & Kepler. ACTA ACUST UNITED AC 2011. [DOI: 10.1088/1742-6596/271/1/012056] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Fernández F, Rodríguez-Sanjuán JC, Mayorga M, Llorca J, García RA, Trugeda S, de la Torre F, Gómez-Fleitas M. Prognostic value of flow cytometry in surgically treated primary gastric lymphoma. Rev Esp Enferm Dig 2007; 98:817-27. [PMID: 17198474 DOI: 10.4321/s1130-01082006001100003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
AIM To investigate whether flow cytometry could help to define the optimal therapeutic strategy of primary gastric lymphomas. MATERIAL AND METHOD Retrospective study of 46 patients having primary gastric lymphoma--according to Dawson criteria--in Ann Arbor stage IE and IIE, who were surgically treated. From selected paraffin-embedded tissue blocks of the tumor, DNA content was studied by flow cytometry (FC). Other pathological tumor features were analysed by hematoxiline-eosine and Giemsa stains as well as immunohistochemical study; any possible influence on postoperative survival was investigated through statistical analysis. RESULTS The DNA ploidy pattern was diploid in 40 cases (87%) and aneuploid (hyperdiploid) in 6 (13%). Postoperative survival probability (PSP) was 62.7% at 5 years. Statistical analysis showed significant prognostic value for Ann Arbor classification--with higher PSP for stage IE (p = 0.009)--and FC parameters: diploid tumors had higher PSP than aneuploid tumors. Also tumors having S-phase (p = 0.044) or G2-M phase values (p = 0.023) under the respective mean values had higher PSP. No influence on PSP was found for wall invasion, Helicobacter pylori infection, Isaacson's histologic type or resection margin involvement. No significant relationship was appreciated between Isaacson's histologic type and DNA ploidy patterns. CONCLUSION FC could be useful in assessing gastric lymphoma prognosis.
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Affiliation(s)
- F Fernández
- Department of Pathology, University Hospital Marqués de Valdecilla, University of Cantabria, Santander, Spain
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Rodríguez-Bonfante C, Amaro A, García M, Mejías Wohlert LE, Guillen P, Antonio García R, Alvarez N, Díaz M, Cárdenas E, Castillo S, Bonfante-Garrido R, Bonfante-Cabarcas R. Epidemiología de la enfermedad de Chagas en el municipio Andrés Eloy Blanco, Lara, Venezuela: infestación triatomínica y seroprevalencia en humanos. CAD SAUDE PUBLICA 2007; 23:1133-40. [PMID: 17486235 DOI: 10.1590/s0102-311x2007000500015] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2005] [Accepted: 07/26/2006] [Indexed: 11/21/2022] Open
Abstract
Se realizó un despistaje serológico y recolección de vectores en cuatro comunidades rurales del municipio Andrés Eloy Blanco, Estado Lara, Venezuela. La muestra fue escogida en forma sistemática y aleatoria basada en conglomerados familiares. Se muestrearon 869 habitantes para determinar anticuerpos anti-Trypanosoma cruzi y anti-Leishmania sp. por inmunofluorescencia indirecta, aceptando como positivo diluciones > a 1:32 para anticuerpos anti-T. cruzi no reactivos para antígenos de Leishmania sp., obteniendo una frecuencia de anticuerpos en la muestra de 6,9% (n = 60); de los cuales 46,66% son femeninos, 53,33% masculinos y 60% mayores de 40 años. Se observó que 5 (8,33%) de los seropositivos eran menores de 10 años y 10 (16,66%) menores de 20 años. Rhodnius prolixus y Panstrongylus geniculatus fueron los triatominos capturados, con índice de infestación de 1,9 y 10,54%, índice de colonización, del 0 y 18,18% en las viviendas infestadas e índice de infección a T. cruzi del 20 y 5,07%, respectivamente. Los resultados sugieren que existe una transmisión activa de la enfermedad de Chagas en el Municipio Andrés Eloy Blanco en las últimas dos décadas y que P. geniculatus está substituyendo a R. prolixus como vector de la enfermedad de Chagas.
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Deogracias ML, Rodríguez-Sanjuán JC, de la Torre F, García RA, Trugeda MS, Domínguez A, Gómez-Fleitas M. Absence of port-site metastases following staging laparoscopy for gastric carcinoma. Rev Esp Enferm Dig 2007; 98:755-9. [PMID: 17094724 DOI: 10.4321/s1130-01082006001000005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
BACKGROUND port-site metastases (PSM) have been reported following oncological laparoscopic surgery. However, their frequency after laparoscopic examination in gastric cancer has not been well established. MATERIAL AND METHODS prospective follow-up of 41 patients having had a staging laparoscopy and a follow-up longer than 12 months. Mean age was 65 years (29-89). After staging, an open gastrectomy was performed in 33 cases. Mean follow-up was 21.4 (12-66) months. PSM was defined as a node in the former port-site wound with adenocarcinoma histology at biopsy. RESULTS no patient showed clinical signs of PSM or port-site recurrence, even in advanced stages. We had no morbidity or postoperative mortality attributable to laparoscopic manoeuvres, and no need for laparotomy in cases without a gastrectomy indication. CONCLUSIONS our results suggest that staging laparoscopy is a safe procedure in gastric carcinoma, as it is not associated with PSM after even considerable follow-up, and has a very low complication rate.
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Affiliation(s)
- M L Deogracias
- General and Gastrointestinal Unit II, Hospital Universitario Marqués de Valdecilla, Santander, Spain.
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Rodríguez-Sanjuán JC, García RA, Trugeda S, de la Torre F, Llorca J, Gómez-Fleitas M. Do current indications for surgery of primary gastric lymphoma exist? Rev Esp Enferm Dig 2006; 98:180-8. [PMID: 16737417 DOI: 10.4321/s1130-01082006000300004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE To analyze the results of our series in order to assess whether surgical excision is still a valid therapeutic option in case the patient needs surgery. Secondarily, to analyze Helicobacter pylori infection rate. PATIENTS AND METHOD A retrospective study of 69 consecutive patients having stage IE-IIE primary gastric lymphoma; of these, 65 were treated by gastrectomy between 1974 and 1999. Mean age: 62.6 years (28-85). New staining of paraffin-embedded samples from the surgical specimen were carried out (hematoxiline-eosine, Giemsa, immunohistochemistry) and reviewed. The histological classification was performed according to Isaacson's criteria. The statistical analysis was done by Chi-squared and Fisher's exact tests, as well as Kaplan-Meier and Log-Rank tests. RESULTS Mortality was 9.2%. There were non-fatal complications in 10.8%. Helicobacter pylori was identified in 62.7%. Seven patients (11.9%) suffered a relapse. The 5-year survival probability was 87%. The statistical analysis did not show any influences of Ann Arbor stage, gastric wall invasion, Helicobacter pylori infection, histological type, or margin resection involvement on survival. CONCLUSIONS Surgical excision provides a high rate of complete remissions and excellent long-term survival with acceptable mortality. Therefore it appears to be a valid treatment in case of emergency surgery, incidental finding, or lack of histological diagnosis.
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Affiliation(s)
- J C Rodríguez-Sanjuán
- Department of General Surgery II, Hospital Universitario Marqués de Valdecilla, Santander, Spain.
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Turck-Chièze S, Couvidat S, Piau L, Ferguson J, Lambert P, Ballot J, García RA, Nghiem P. Surprising sun: a new step towards a complete picture? Phys Rev Lett 2004; 93:211102. [PMID: 15600989 DOI: 10.1103/physrevlett.93.211102] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2004] [Indexed: 05/24/2023]
Abstract
Important revisions of the solar model ingredients have appeared recently. We first show that the updated CNO composition suppresses the anomalous position of the Sun in the known galactic enrichment. The following law, He/H = 0.075 + 44.6 O/H in number fraction, is now compatible with all the indicators. We then suggest some directions of investigation to solve the discrepancies between the standard model and solar seismic observations. We finally update our predicted neutrino fluxes using a seismic model and all the recent progress. We get 5.31 +/- 0.6 x 10(6)/cm2/s for the total 8B neutrinos, 66.5 +/- 4.4 SNU and 2.76 +/- 0.4 SNU for the gallium and chlorine detectors, all in remarkable agreement with the detected values including neutrino oscillations for the last two. So, the acoustic modes and detected neutrinos see the same Sun, but the standard model fails to reproduce them.
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Abstract
Cholesterol was found to inhibit full fusion of oppositely charged phospholipid bilayer vesicles by stabilizing the contacting membranes at the stage of the hemifused intermediate. Vesicles of opposite charge containing different amounts of cholesterol were prepared using cationic (1,2-dioleoyl-sn-glycero-3-ethylphosphocholine) and anionic (dioleoylphosphatidylglycerol) phospholipids. Pairwise interactions between such vesicles were observed by fluorescence video microscopy in real time after electrophoretically maneuvering the vesicles into contact. Hemifusion accounted for more than 80% of the observed events when the vesicles contained 33-50 mole% cholesterol. In contrast, vesicles containing only a small proportion of cholesterol (</=10 mole%), underwent full fusion in approx. 70% of the interactions monitored. The role of cholesterol is explained both as favoring the formation of the hemifused intermediate according to the adhesion-condensation mechanism of bilayer fusion and as disfavoring the transition from hemifusion to full fusion on the basis of reduced tension in the vesicle bilayers.
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Affiliation(s)
- R A García
- Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, 2153 North Campus Drive, 60208-3500, Evanston, IL, USA
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Abstract
Synaptotagmin I is a critical component of the synaptic machinery that senses calcium influx and triggers synaptic vesicle fusion and neurotransmitter release. Fluorescence resonance energy transfer studies conducted on synaptotagmin demonstrate that calcium concentrations required for fusion induce a conformational change (EC(50) approximately 3 mM) that brings the two calcium-binding C2 domains in synaptotagmin closer together. Analytical ultracentrifugation studies reveal that synaptotagmin is monomeric under these conditions, indicating that this calcium-triggered association between the C2 domains is intramolecular, rather than intermolecular. These results suggest a mechanism for synaptotagmin function at the presynaptic plasma membrane that involves the self-association of C2 domains.
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Affiliation(s)
- R A García
- Department of Biochemistry, Molecular Biology, and Cell Biology, 2153 North Campus Drive, Northwestern University, Evanston, IL 60208-3300, USA
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Abstract
The extrasynaptic region of the squid giant nerve fiber exhibits neuron-Schwann cell interactions that appear to involve glutamate as a mediator. In an earlier work, it was demonstrated that the periaxonal sheaths of such nerves (where the Schwann cells are located) possess the capacity to transport glutamate. However there was no information available about the possible fate of the glutamate incorporated into the sheaths. In this study, it is demonstrated that the periaxonal sheaths of the extrasynaptic region of squid giant nerves are capable of metabolizing glutamate. Sheaths incubated with 10 microM [1-14C] glutamate produced [14C] O2 in a manner proportional to time and estimated cell water volume. At least 45% of this CO2 production was determined to be independent of transaminase catalyzed isotopic exchange, thus reflecting real degradation (decarboxylation) of glutamate. It was also demonstrated that the sheaths were capable of glutamine synthesis. Taken together, the findings of our laboratory indicate not only that the Schwann cells of the sheaths fulfil the requirements for a site for the uptake and metabolism of transmitter glutamate in the squid giant nerve but also that certain metabolic characteristics associated with the neuro-glial unit around synapses are also found in non-synaptic areas of nerve fibers.
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Affiliation(s)
- R A García
- Unidad de Neurociencias, Instituto Internacional de Estudios Avanzados (I.D.E.A.), Caracas, Venezuela.
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Abstract
The substructure and responses of individual 100-nm synaptic vesicles to osmotic stress have been probed with an atomic force microscope (AFM) operating in tapping mode. Cholinergic synaptic vesicles from the electric organ of Torpedo californica were imaged continuously as the osmolarity of the buffer was decreased. Vesicles in hyposmotic buffer lysed to form flat circular structures on the mica surface with a diameter about two times that of intact vesicles and a thickness of 7.2 +/- 1.7 nm, which can accommodate the lipid bilayer plus the internal proteoglycan. Images of intact vesicles in air reveal creases in the membrane surface. Phase mode AFM images of lysed vesicles in air show the presence of a material not seen on intact vesicles that might be intravesicular proteoglycan released from the membrane at very low osmotic and ionic strength.
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Affiliation(s)
- R A García
- Department of Chemistry, Neuroscience Research Institute, University of California, Santa Barbara 93106, USA
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Abstract
The squid giant nerve exhibits neuron-Schwann cell interactions that appear to involve glutamate as a mediator; however, there is no information available about the possible fate of the released glutamate. In this study, it is demonstrated that the periaxonal sheaths of the extrasynaptic regions of squid giant nerves (where the glial cells are located) possess the capacity to transport glutamate. In whole intact nerves incubated with low-glutamate concentrations for long periods of time, the majority of the glutamate incorporated into the tissue was found in the sheaths. Axoplasm-free sheaths incubated for long periods of time with low concentrations of glutamate were able to accumulate this amino acid against a large apparent concentration gradient. Sheath glutamate uptake occurred in a sodium-dependent fashion over a wide concentration range and displayed both high- and low-affinity components. Glutamate uptake at concentrations below the Km of the high affinity component was independent of homoexchange and displayed a specificity that is similar to that described for high-affinity glutamate transport in mammalian brain. It is proposed that the sheath transport systems may be involved in the regulation of glutamate levels in the intercellular clefts of the nerve fiber, as part of the glutamatergic neuron-glial signaling mechanisms in the squid giant nerve fiber.
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Affiliation(s)
- R A García
- Unidad de Neurociencias, Instituto Internacional de Estudios Avanzados (I.D.E.A.), Caracas, Venezuela
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Abstract
The present study sought to investigate the presence and distribution of some enzymatic activities involved in the metabolism of glutamate in the giant nerve fiber of the tropical squid Sepioteuthis sepioidea. Specific activities of aspartate aminotransferase and glutamate dehydrogenase were evaluated in homogenates of the isolated giant fiber, extruded axoplasm, and axoplasm-free giant nerve fiber sheaths. The activities of both enzymes were present in the tissue. The specific activity of aspartate aminotransferase was similar in axoplasm and sheaths. However, the specific activity of glutamate dehydrogenase was an order of magnitude higher in the sheaths. This finding is discussed in the framework of the hypothesis that proposes that a differential distribution of the enzymes of the glutamatergic system between the axonal and neuroglial compartments forms part of a system of communication between these cells whose neuronal signal may be glutamate.
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Affiliation(s)
- R A García
- Unidad de Neurociencias, Instituto Internacional de Estudios Avanzados (IDEA), Caracas, Venezuela
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Muñoz A, García RA, Pérez-Aranda A. Potentiation by levamisole, methisoprinol, and adenine or adenosine of the inhibitory activity of human interferon against encephalomyocarditis virus. Antimicrob Agents Chemother 1986; 30:192-5. [PMID: 2428301 PMCID: PMC176466 DOI: 10.1128/aac.30.1.192] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The antiviral action of different human interferons against encephalomyocarditis virus in HeLa cell cultures was analyzed. Cell treatment with levamisole (200 micrograms/ml), methisoprinol (1 mg/ml), or adenine or adenosine (33 or 100 micrograms/ml, respectively) potentiated the anti-encephalomyocarditis virus activity of human interferon by 8- to 32-fold. A higher level of potentiation (256-fold) was achieved either by combined treatments with levamisole plus methisoprinol or by treatment with one of these compounds plus adenine or adenosine.
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