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1.
Ticks Tick Borne Dis ; 15(4): 102346, 2024 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-38643720

RESUMEN

Bovine anaplasmosis is a tick-borne disease caused by Anaplasma marginale in the United States. The objective of this study was to use a survey tool to generate information for beef operations in California on anaplasmosis prevention and control management, including to what extent management activities were informed by perceived herd-level exposure to A. marginale infection or occurrence of clinical anaplasmosis cases. We mailed 2,621 questionnaires with questions on Anaplasma status, herd demographics, anaplasmosis control and prevention measures, and environmental factors to beef ranchers in California in October 2020. Survey-weighted chi-square tests were used to compare management differences according to perceived Anaplasma infection status. Generalized estimating equations (GEEs) were used to analyze whether region of California, management practices, or environmental factors were associated with reported clinical cases of anaplasmosis in the previous five years. A total of 466 questionnaires describing 749 herds were obtained and used in this study. Use of management measures, including deliberate exposure of calves to ticks, vaccination for Anaplasma, infection control through antibiotics in feed, maintaining a completely closed herd, blood testing for Anaplasma on all herd additions, and taking no anaplasmosis control and prevention measures, were significantly different between herds with or without perceived A. marginale infection based on producers' self-declared status. The overall perceived prevalence for Anaplasma infection and reported clinical cases of anaplasmosis at the herd level was 26.0 % (95 % CI: 24.3-27.7 %) and 17.1 % (95 % CI: 15.6-18.6 %) respectively, with the highest perceived infection and case numbers reported in the Central Coast region. In the GEE model, higher odds of reporting clinical cases of anaplasmosis in the previous five years were observed in cattle located in the Central Coast region, cattle within a large herd, cattle that are treated with tick/fly control, cattle in a completely closed herd, and cattle receiving Anaplasma vaccine. Anaplasma infection and bovine anaplasmosis status may be underestimated in beef herds in California based on previous study results. Changing needles between cattle after injections and conducting blood testing for Anaplasma on herd additions are important Anaplasma management measures that are infrequently implemented in beef herds in California. The results show a need for producer education to improve producers' awareness of bovine anaplasmosis and implement proper measures for disease control and prevention.


Asunto(s)
Anaplasma marginale , Anaplasmosis , Enfermedades de los Bovinos , Animales , Bovinos , Anaplasmosis/epidemiología , Anaplasmosis/microbiología , California/epidemiología , Enfermedades de los Bovinos/epidemiología , Enfermedades de los Bovinos/microbiología , Enfermedades de los Bovinos/prevención & control , Masculino , Femenino , Encuestas y Cuestionarios
2.
Phys Rev Lett ; 125(3): 032701, 2020 Jul 17.
Artículo en Inglés | MEDLINE | ID: mdl-32745397

RESUMEN

We report a high-statistics measurement of the L/K orbital electron capture ratio in ^{7}Be embedded in cryogenic Ta. The thin Ta film formed part of a high-resolution superconducting tunnel junction radiation detector that was used to identify the signals from different decay channels. The measured L/K capture ratio of 0.070(7) is significantly larger than the only previous measurement of this quantity and the theoretical predictions that include in-medium effects. This value is a uniquely sensitive probe of the 1s and 2s orbital overlaps with the nucleus and is of relevance to nuclear and atomic physics, as well as Li production in novae and other astrophysical scenarios. This is the first experiment that uses superconducting tunnel junctions for nuclear-recoil detection, opening a new experimental avenue for low-energy precision measurements with rare isotopes.

3.
Lett Appl Microbiol ; 69(1): 23-29, 2019 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-30932223

RESUMEN

The occurrence of Escherichia coli O157 and Salmonella spp. in solid bovine manure was investigated through a multi-county survey in California. Solid bovine manure samples (n = 91) were collected from 13 dairy farms located in multiple counties in California between June 2016 and August 2017. To quantify pathogens, DNA was extracted from bacteria in manure samples. Afterwards, the prevalence and levels of E. coli O157 and Salmonella spp. in solid bovine manure were determined by real-time quantitative PCR (qPCR). The prevalence of E. coli O157 and Salmonella spp. in solid bovine manure was 15·4 and 6·6% respectively. Escherichia coli O157 and Salmonella spp. levels in positive samples ranged from 3·1 to 5·3 log CFU per g and from positive (the population was <3 log CFU per g) to 5·2 log CFU per g respectively. Surface samples of manure piles had higher prevalence and levels of E. coli O157 and Salmonella spp. than subsurface samples, while no seasonal effects on pathogen occurrence were observed. Our results indicated that solid bovine manure is a source of E. coli O157 and Salmonella spp. and the application of untreated manure as biological soil amendments may pose potential risks to public health. SIGNIFICANCE AND IMPACT OF THE STUDY: Our findings suggested that the presence of Escherichia coli O157 and Salmonella spp. in solid bovine manure may pose potential risks if untreated manure is applied as biological soil amendments. Considering the large-scale sampling used in this study, the observations provide a holistic assessment in terms of pathogen prevalence in solid bovine manure.


Asunto(s)
Infecciones por Escherichia coli/epidemiología , Infecciones por Escherichia coli/veterinaria , Escherichia coli O157/aislamiento & purificación , Estiércol/microbiología , Salmonelosis Animal/epidemiología , Salmonella/aislamiento & purificación , Animales , California/epidemiología , Bovinos , Recuento de Colonia Microbiana , Reacción en Cadena de la Polimerasa , Prevalencia , Suelo , Microbiología del Suelo
4.
Transl Anim Sci ; 1(3): 250-254, 2017 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-32704649

RESUMEN

Beef Tracker is a web-based mapping platform that provides beef cattle ranchers a tool to demonstrate that cattle production fits within sustainable ecosystems and to provide regional data to update beef sustainability lifecycle analysis. After digitizing pastures, herd data (class and number of animals) are input on a mobile device in a graphical pasture interface, stored in the cloud, and linked via the web to a personal computer for inventory tracking and analysis. Pasture use calculated on an animal basis provides quantifiable data regarding carrying capacity and beef production. This data is sought by the National Beef Cattle Association to provide more accurate inputs for beef sustainability lifecycle analyses. This application is a useful way for large, complex ranching operations to have all employees remain informed as to cattle movements and ranch wide improvement projects. Better yet, as users make changes to their operation in BeefTracker, histories are automatically recorded and stored in the cloud. After initial testing by university range scientists and ranchers, we have enhanced the BeefTracker application to improve automation for increased ease of use. The following have been added: ability to access and edit the BeefTracker livestock inventory while disconnected from WiFi and cell service, ability to represent portions of a pasture in BeefTracker as irrigated and nonirrigated, and ability to report animal unit harvest (by pasture) calculated on an annual basis. This will provide quantifiable data regarding carrying capacity and subsequent beef production to provide more accurate data inputs for the beef sustainability lifecycle analysis, enhanced map synchronization, and improved security to allow a single individual to access multiple livestock operations without needing multiple user IDs and passwords.

5.
Ophthalmic Plast Reconstr Surg ; 25(6): 493-4, 2009.
Artículo en Inglés | MEDLINE | ID: mdl-19935260

RESUMEN

This case reports 4-year-old monozygotic twins incompletely concordant for simple congenital ptosis. Pedigree analysis demonstrates 4 generations of autosomal dominant transmission. The case and pedigree are reviewed in light of a number of recent advances in the understanding of genetic influences on simple congenital ptosis.


Asunto(s)
Blefaroptosis/genética , Enfermedades en Gemelos/genética , Gemelos Monocigóticos , Blefaroptosis/congénito , Blefaroptosis/cirugía , Preescolar , Femenino , Humanos , Músculos Oculomotores/cirugía , Procedimientos Quirúrgicos Oftalmológicos , Linaje
6.
Eur J Biochem ; 260(1): 176-82, 1999 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-10091597

RESUMEN

A variant of bovine pancreatic ribonuclease A has been prepared with seven amino acid substitutions (Q55K, N62K, A64T, Y76K, S80R, E111G, N113K). These substitutions recreate in RNase A the basic surface found in bovine seminal RNase, a homologue of pancreatic RNase that diverged some 35 million years ago. Substitution of a portion of this basic surface (positions 55, 62, 64, 111 and 113) enhances the immunosuppressive activity of the RNase variant, activity found in native seminal RNase, while substitution of another portion (positions 76 and 80) attenuates the activity. Further, introduction of Gly at position 111 has been shown to increase the catalytic activity of RNase against double-stranded RNA. The variant and the wild-type (recombinant) protein were crystallized and their structures determined to a resolution of 2.0 A. Each of the mutated amino acids is seen in the electron density map. The main change observed in the mutant structure compared with the wild-type is the region encompassing residues 16-22, where the structure is more disordered. This loop is the region where the polypeptide chain of RNase A is cleaved by subtilisin to form RNase S, and undergoes conformational change to allow residues 1-20 of the RNase to swap between subunits in the covalent seminal RNase dimer.


Asunto(s)
Endorribonucleasas/química , Proteínas Recombinantes de Fusión/química , Ribonucleasa Pancreática/química , Enlace de Hidrógeno , Modelos Moleculares , Mutación/genética , Conformación Proteica , Proteínas Recombinantes de Fusión/genética , Difracción de Rayos X
7.
Pure Appl Chem ; 70(2): 263-6, 1998 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-11542721

RESUMEN

A research program has applied the tools of synthetic organic chemistry to systematically modify the structure of DNA and RNA oligonucleotides to learn more about the chemical principles underlying their ability to store and transmit genetic information. Oligonucleotides (as opposed to nucleosides) have long been overlooked by synthetic organic chemists as targets for structural modification. Synthetic chemistry has now yielded oligonucleotides with 12 replicatable letters, modified backbones, and new insight into why Nature chose the oligonucleotide structures that she did.


Asunto(s)
ADN/química , Biología Molecular/tendencias , Ácidos Nucleicos/química , Oligonucleótidos/síntesis química , Catálisis , Codón , Estructura Molecular , Ácidos Nucleicos/síntesis química , Oligonucleótidos/química , Fosfatos/química , Sulfonas/química
8.
Int J Lang Commun Disord ; 33 Suppl: 457-62, 1998.
Artículo en Inglés | MEDLINE | ID: mdl-10343737

RESUMEN

This paper reports on the speech processing skills of a group of four year old children with specific speech difficulties and examines the impact of an additional language impairment on these skills. Forty seven children with speech difficulties were tested on two speech output measures and one speech input measure to assess the accuracy of their phonological representations. Their performance was compared to a matched control group n = 47 and analysed according to the presence/absence of an additional language impairment. It was found that children with both speech and language difficulties had poorer speech processing abilities compared to both the normal controls and the children with speech-only difficulties. The clinical implications of these findings are outlined.


Asunto(s)
Trastornos del Lenguaje/fisiopatología , Fonética , Trastornos del Habla/fisiopatología , Análisis de Varianza , Preescolar , Humanos , Trastornos del Lenguaje/complicaciones , Trastornos del Lenguaje/psicología , Pruebas del Lenguaje , Pruebas de Articulación del Habla , Trastornos del Habla/complicaciones , Trastornos del Habla/psicología
9.
Int J Lang Commun Disord ; 33 Suppl: 481-6, 1998.
Artículo en Inglés | MEDLINE | ID: mdl-10343741

RESUMEN

Although diadochokinetic (DDK) tasks are a popular assessment tool in clinical practice, the interpretation of their results is often limited and obscure. This paper examines the development of DDK skills in normally developing children (age range 3-5 years) for comparison with three case studies of children with specific speech difficulties. The results are presented in terms of accuracy, rate and consistency of response. The normally-developing children increased the accuracy and consistency but not the rate of their responses between the ages of 3 and 5 years. The three case study children (matched on severity of speech difficulty) not only performed differently from control children on some of the measures but also performed differently from each other. The diagnostic value of a developmental DDK profile is discussed.


Asunto(s)
Trastornos del Habla/fisiopatología , Habla/fisiología , Niño , Preescolar , Estudios de Evaluación como Asunto , Femenino , Humanos , Pruebas de Articulación del Habla
10.
Acta Chem Scand (Cph) ; 50(3): 243-8, 1996 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-8901176

RESUMEN

Paleomolecular biochemistry is a new field of science that seeks to understand how life emerged and developed in interaction with its geophysical surroundings. It is an experimental science, involving reconstruction of extinct biomolecules in the laboratory, studying their properties in the laboratory, and inferring details of their behavior and function in the context of geological data. An outline is provided of some tools of this field, together with its application to the study of two specific systems, ribonuclease and alcohol dehydrogenase.


Asunto(s)
Evolución Biológica , Catálisis , Enzimas/metabolismo , Secuencia de Aminoácidos , Animales , Humanos , Datos de Secuencia Molecular
11.
Biochemistry ; 34(35): 11026-36, 1995 Sep 05.
Artículo en Inglés | MEDLINE | ID: mdl-7669760

RESUMEN

Despite the high degree of sequence similarity in their basic-helix-loop-helix (BHLH) domains, MASH-1 and MyoD are involved in different biological processes. In order to define possible differences between the DNA binding specificities of these two proteins, we investigated the DNA binding properties of MASH-1 by circular dichroism spectroscopy and by electrophoretic mobility shift assays (EMSA). Upon binding to DNA, the BHLH domain of MASH-1 underwent a conformational change from a mainly unfolded to a largely alpha-helical form, and surprisingly, this change was independent of the specific DNA sequence. The same conformational transition could be induced by the addition of 20% 2,2,2-trifluoroethanol. The apparent dissociation constants (KD) of the complexes of full-length MASH-1 with various oligonucleotides were determined from half-saturation points in EMSAs. MASH-1 bound as a dimer to DNA sequences containing an E-box with high affinity KD = 1.4-4.1 x 10(-14) M2). However, the specificity of DNA binding was low. The dissociation constant for the complex between MASH-1 and the highest affinity E-box sequence (KD = 1.4 x 10(-14) M2) was only a factor of 10 smaller than for completely unrelated DNA sequences (KD = approximately 1 x 10(-13) M2). The DNA binding specificity of MASH-1 was not significantly increased by the formation of an heterodimer with the ubiquitous E12 protein. MASH-1 and MyoD displayed similar binding site preferences, suggesting that their different target gene specificities cannot be explained solely by differential DNA binding. An explanation for these findings is provided on the basis of the known crystal structure of the BHLH domain of MyoD.


Asunto(s)
Proteínas de Unión al ADN/metabolismo , ADN/metabolismo , Secuencias Hélice-Asa-Hélice/fisiología , Factores de Transcripción/metabolismo , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico , Sitios de Unión , Dicroismo Circular , ADN/genética , Proteínas de Unión al ADN/química , Proteínas de Unión al ADN/genética , Escherichia coli/genética , Secuencias Hélice-Asa-Hélice/genética , Técnicas In Vitro , Cinética , Modelos Moleculares , Datos de Secuencia Molecular , Proteína MioD/química , Proteína MioD/genética , Proteína MioD/metabolismo , Unión Proteica , Conformación Proteica , Ratas , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Homología de Secuencia de Aminoácido , Factores de Transcripción/química , Factores de Transcripción/genética
12.
Nature ; 374(6517): 57-9, 1995 Mar 02.
Artículo en Inglés | MEDLINE | ID: mdl-7532788

RESUMEN

The sequences of proteins from ancient organisms can be reconstructed from the sequences of their descendants by a procedure that assumes that the descendant proteins arose from the extinct ancestor by the smallest number of independent evolutionary events ('parsimony'). The reconstructed sequences can then be prepared in the laboratory and studied. Thirteen ancient ribonucleases (RNases) have been reconstructed as intermediates in the evolution of the RNase protein family in artiodactyls (the mammal order that includes pig, camel, deer, sheep and ox). The properties of the reconstructed proteins suggest that parsimony yields plausible ancient sequences. Going back in time, a significant change in behaviour, namely a fivefold increase in catalytic activity against double-stranded RNA, appears in the RNase reconstructed for the founding ancestor of the artiodactyl lineage, which lived about 40 million years ago. This corresponds to the period when ruminant digestion arose in the artiodactyls, suggests that contemporary artiodactyl digestive RNases arose from a non-digestive ancestor, and illustrates how evolutionary reconstructions can help in the understanding of physiological function within a protein family.


Asunto(s)
Artiodáctilos , Evolución Biológica , Ribonucleasas/metabolismo , Secuencia de Aminoácidos , Animales , Artiodáctilos/clasificación , Artiodáctilos/genética , Artiodáctilos/metabolismo , Catálisis , Digestión , Estabilidad de Enzimas , Datos de Secuencia Molecular , Mutagénesis Sitio-Dirigida , ARN/metabolismo , ARN Bicatenario/metabolismo , Proteínas Recombinantes , Ribonucleasas/genética
13.
J Prosthet Dent ; 71(2): 209-14, 1994 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-8126680

RESUMEN

Described in this pilot study is the genesis, development, and use of a system for measuring impression and die material accuracy with low-fusing bismuth alloy counterdies. The method followed the same sequence used in dental laboratory technology with the assumption that the errors associated with the wax pattern, investing, and casting had been largely eliminated. Determination of the alloy shrinkage was the first step, followed by a comparison of two impression and two die materials used in conjunction with master dies of full crown and MOD configurations. Misfit measurements revealed marginal openings of 12 to 219 microns depending on die configuration, the impression, or the die material. A 2 x 2 factorial statistical model with interaction revealed main and interactive effects. This procedure could be useful in future investigations.


Asunto(s)
Técnica de Colado Dental/normas , Materiales de Impresión Dental , Modelos Dentales/normas , Análisis de Varianza , Bismuto , Coronas , Aleaciones Dentales , Humanos , Incrustaciones , Análisis de los Mínimos Cuadrados , Proyectos Piloto , Reproducibilidad de los Resultados
14.
Eur J Disord Commun ; 28(4): 331-48, 1993.
Artículo en Inglés | MEDLINE | ID: mdl-8312650

RESUMEN

Although various psycholinguistic models of speech and language processing have been developed to account for levels of breakdown in developmental speech disorders, it is not obvious how they are to be applied in clinical practice. At the same time, speech and language therapists have routinely been using a wide range of procedures, including published tests, that tap different levels of phonological processing in the child. When analysed and classified appropriately, these procedures can form the basis for a comprehensive psycholinguistic investigation of developmental speech disorders. The aim of this paper is to present a clinically usable, needs-driven but theoretically motivated framework for investigation. The framework is organised in terms of a series of questions that the clinician can pose about the levels of deficit in processing that may be giving rise to the child's speech problems. It is illustrated by means of a case study of a child with a severe developmental speech disorder, which reveals a complex pattern of deficits within the speech processing chain. As the main purpose of the framework is to provide a useful clinical tool to facilitate the planning of appropriate therapy for the individual child, some therapy objectives deriving from the assessment are outlined.


Asunto(s)
Psicolingüística/métodos , Trastornos del Habla/diagnóstico , Preescolar , Femenino , Humanos , Trastornos del Desarrollo del Lenguaje/diagnóstico , Fonética , Logopedia
15.
Eur J Disord Commun ; 27(1): 19-34, 1992.
Artículo en Inglés | MEDLINE | ID: mdl-1446093

RESUMEN

Developmental verbal dyspraxia is examined from four perspectives: clinical, phonetic, linguistic and cognitive. The paper critically discusses the problems encountered when criteria for identifying acquired speech disorders in the adult population are applied to children's speech difficulties without modifications. It is argued that studies of verbal dyspraxia in children have ignored the unfolding nature of this condition and that a developmental perspective has been lacking in the literature. A need for the inclusion of appropriate control groups and longitudinal case studies is identified. The issue and process of differential diagnosis are addressed and a checklist of criteria for identifying developmental verbal dyspraxia is included. It is noted that this process will inevitably be lengthy with data needed from different aspects of a child's development. Phonetic characteristics alone may not be sufficient to recognise this medical condition with its complex psycholinguistic and educational consequences.


Asunto(s)
Trastornos de la Articulación/etiología , Conducta Verbal , Trastornos de la Articulación/diagnóstico , Trastornos de la Articulación/psicología , Cognición , Femenino , Humanos , Masculino , Destreza Motora , Factores Sexuales
16.
Eur J Disord Commun ; 27(1): 35-54, 1992.
Artículo en Inglés | MEDLINE | ID: mdl-1446094

RESUMEN

A longitudinal study of the speech errors of two school-age children with what was described as developmental verbal dyspraxia is presented. By comparing them with a group of normally developing children matched on articulation age, it was possible to identify speech errors not typical of earlier speech development, involving problems with syllable structure planning and vocal tract coordination. The speech-disordered children could produce more words correctly than the controls, but, when they did make speech errors, these were more serious than those found in the younger children. The speech-disordered children were followed up 4 years later. Although their speech had improved, they presented with the same profile of error types. They had increased intelligibility by adding more word-specific articulations but still had difficulties with novel and complex material. The adoption of a developmental framework in this study allowed the identification of different levels of breakdown within the speech production process. The case-study method is recommended to investigate how these levels may interact and the clinical implications of the findings are outlined.


Asunto(s)
Trastornos de la Articulación/fisiopatología , Conducta Verbal/fisiología , Envejecimiento/fisiología , Niño , Femenino , Humanos , Estudios Longitudinales , Masculino
17.
J Med Syst ; 15(5-6): 345-58, 1991 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-1812187

RESUMEN

This study examines the decision-making process that a medium-sized hospital took to develop a management information system. Since system developers in this particular hospital were all users without system expertise, a substantial amount of time was devoted to their search for relevant information. Outside consulting, literature review, and a market survey were conducted for the developers to understand the characteristics of systems products on the market. Developers also invited extended user participation in vendor evaluation. The authors analyzed the reasoning process behind the successful selection of a vendor-supported information system. The findings provide hospitals of similar characteristics a decision model to follow in their search for a vendor-supported information system.


Asunto(s)
Toma de Decisiones en la Organización , Sistemas de Información en Hospital/normas , Sistemas de Información Administrativa/normas , Departamento de Compras en Hospital/organización & administración , Alabama , Comercio/normas , Consultores , Hospitales con 100 a 299 Camas , Sistemas de Información en Hospital/estadística & datos numéricos , Hospitales Religiosos/organización & administración , Equipos de Administración Institucional , Sistemas de Información Administrativa/estadística & datos numéricos , Técnicas de Planificación , Encuestas y Cuestionarios , Análisis de Sistemas
18.
FEBS Lett ; 281(1-2): 275-7, 1991 Apr 09.
Artículo en Inglés | MEDLINE | ID: mdl-1901803

RESUMEN

Chemical modification studies suggest that two residues of bovine pancreatic ribonuclease A (RNase A), Lys-41 and Asp-121, are important for catalysis. Three mutants of RNase A have been prepared, two point mutants with Lys-41 altered to Arg-41 and Asp-121 altered to Glu-121, and a double mutant where both residues are altered. The Lys-41 Arg mutant has ca. 2% the catalytic activity (kcat/Km) of the native protein, while the Asp-121Glu mutant has ca. 17% the catalytic activity of the native protein. The double mutant has catalytic activity comparable to the Lys-41Arg mutant.


Asunto(s)
Ácido Aspártico , Lisina , Mutagénesis Sitio-Dirigida , Ribonucleasa Pancreática/genética , Secuencia de Aminoácidos , Animales , Bovinos , Genes Sintéticos , Ribonucleasa Pancreática/metabolismo
19.
FEBS Lett ; 262(1): 104-6, 1990 Mar 12.
Artículo en Inglés | MEDLINE | ID: mdl-2318301

RESUMEN

The sequence of the ribonuclease from the ancestor of swamp buffalo, river buffalo, and ox, corresponding approximately to Pachyportax latidens, an extinct ruminant known from the fossil record, has been reconstructed using the rule of 'maximum parsimony'. This protein and two sequences that may have been intermediates in the evolution of modern ribonuclease have been constructed in the laboratory by site-directed mutagenesis, and their properties examined.


Asunto(s)
Ribonucleasas/análisis , Rumiantes/metabolismo , Secuencia de Aminoácidos , Animales , Evolución Biológica , Fósiles , Cinética , Datos de Secuencia Molecular
20.
J Biomed Mater Res ; 23(1): 81-90, 1989 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-2540206

RESUMEN

One aim of this in vitro investigation was to determine the effect of substituting four phenols and two methacrylates with vinyl functions on the dentin bond strengths of several new experimental dentin bonding agents. Another objective was to determine the effect of postextraction age and dentin level within the tooth on tensile bond strengths of these toluene diisocyanate-derived adhesives. Extracted third molars were divided into postextraction age groups and sectioned into three slices approximately 400 microns thick. The four substituted phenols were: eugenol, o-methoxyphenol, o-chlorophenol, and p-cresol. Substituted methacrylates with vinyl ligands were 2-hydroxyethyl methacrylate (HEMA) and 6-hydroxyhexyl methacrylate (HHMA). Results showed that adhesives made with o-chlorophenol, p-cresol, and methoxyphenol with HEMA were the best, while those made with eugenol and HHMA were the worst. The post extraction age of the tooth and the dentin depth had no consistent effect on most adhesive bond strengths which were generally around 10.3 MPa (1500 psi).


Asunto(s)
Acrilatos , Cianatos , Cementos Dentales , Dentina , Metacrilatos , Fenoles , 2,4-Diisocianato de Tolueno , Humanos , Ligandos , Diente Molar , Relación Estructura-Actividad
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