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1.
Artículo en Alemán | MEDLINE | ID: mdl-24357167

RESUMEN

Despite having achieved nationwide registry coverage in addition to substantial improvements in data on the epidemiology of cancer in Germany, the Centre for Cancer Registry Data continues to estimate national statistics on incidence, survival, and prevalence instead of calculating these directly from available data. The methods used for evaluations are based initially on estimates of registration completeness or, for survival analyses, an assessment of the quality of follow-up data. The completeness of incident case registration is estimated on the basis of the mortality/incidence procedure, which assumes a largely constant relationship between the mortality and incidence of a cancer type among people of the same age and sex across federal states. Inclusion criteria for consideration of registry data in national survival analyses are less than 15% of death certificate only (DCO) cases and plausible survival for patients with pancreatic cancer or metastatic lung cancer. Of the 477,300 incident cancer cases estimated for 2010, 429,900 were reported by the cancer registries (90%), and ten federal states contributed data to national survival estimates.


Asunto(s)
Interpretación Estadística de Datos , Neoplasias/mortalidad , Modelos de Riesgos Proporcionales , Sistema de Registros/estadística & datos numéricos , Análisis de Supervivencia , Adolescente , Adulto , Distribución por Edad , Anciano , Anciano de 80 o más Años , Niño , Preescolar , Femenino , Alemania/epidemiología , Humanos , Incidencia , Lactante , Recién Nacido , Masculino , Persona de Mediana Edad , Pronóstico , Factores de Riesgo , Distribución por Sexo , Adulto Joven
2.
Artículo en Alemán | MEDLINE | ID: mdl-23703478

RESUMEN

The "German Health Interview and Examination Survey for Adults" (DEGS) is part of the health monitoring program of the Robert Koch Institute (RKI) and is designed as a combined cross-sectional and longitudinal survey. The first wave (DEGS1; 2008-2011) comprised interviews and physical examinations. The target population were 18- to 79-year olds living in Germany. The mixed design consisted of a new sample randomly chosen from local population registries which was supplemented by participants from the "German National Health Interview and Examination Survey 1998" (GNHIES98). In total, 8,152 persons took part, among them 4,193 newly invited (response 42%) and 3,959 who had previously taken part in GNHIES98 (response 62%). 7,238 participants visited one of the 180 local study centres, 914 took part in the interview-only programme. The comparison of the net sample with the group of non-participants and with the resident population of Germany suggests a high representativeness regarding various attributes. To account for certain aspects of the population structure cross-sectional, trend and longitudinal analyses are corrected by weighting factors. Furthermore, different participation probabilities of the former participants of GNHIES98 are compensated for. An English full-text version of this article is available at SpringerLink as supplemental.


Asunto(s)
Estado de Salud , Encuestas Epidemiológicas/normas , Entrevistas como Asunto/métodos , Entrevistas como Asunto/normas , Selección de Paciente , Factores Socioeconómicos , Gestión de la Calidad Total/organización & administración , Adulto , Alemania/epidemiología , Humanos
3.
Phytopathology ; 101(10): 1176-83, 2011 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-21679037

RESUMEN

In French and German vineyards, Botrytis cinerea isolates with multiple fungicide resistance phenotypes have been observed with increasing frequencies. Multidrug resistance (MDR) results from mutations that lead to constitutive overexpression of genes encoding drug efflux transporters. In MDR2 and MDR3 strains, overexpression of the major facilitator superfamily transporter gene mfsM2 has been found to result from a rearrangement in the mfsM2 promoter (type A), caused by insertion of a retroelement (RE)-derived sequence. Here, we report the discovery of another, similar RE-induced rearrangement of the mfsM2 promoter (type B) in a subpopulation of French MDR2 isolates. MDR2 isolates harboring either type A or type B mutations in mfsM2 show the same resistance phenotypes and similar levels of mfsM2 overexpression. RE sequences similar to those in mfsM2 were found in low copy numbers in other but not all B. cinerea strains analyzed, including non-MDR2 strains. Population genetic analyses support the hypothesis that the two rearrangement mutations have only occurred once, and are responsible for the appearance and subsequent spread of all known MDR2 and MDR3 strains in French and German wine-growing regions.


Asunto(s)
Subfamilia B de Transportador de Casetes de Unión a ATP/genética , Botrytis/efectos de los fármacos , Botrytis/genética , Farmacorresistencia Fúngica Múltiple/genética , Proteínas Fúngicas/genética , Vitis/microbiología , Subfamilia B de Transportador de Casetes de Unión a ATP/metabolismo , Secuencia de Bases , Francia , Proteínas Fúngicas/metabolismo , Fungicidas Industriales/farmacología , Reordenamiento Génico , Genética de Población , Alemania , Pruebas de Sensibilidad Microbiana , Datos de Secuencia Molecular , Mutación , Fenotipo , Filogenia , Regiones Promotoras Genéticas/genética , Retroelementos/genética , Análisis de Secuencia de ADN , Vino/microbiología , Miembro 4 de la Subfamilia B de Casete de Unión a ATP
4.
Gene ; 82(1): 31-41, 1989 Oct 15.
Artículo en Inglés | MEDLINE | ID: mdl-2684774

RESUMEN

Nine different hammerhead RNA self-cleaving domains consistent with the consensus secondary structure proposed by Keese and Symons (1987) were prepared and tested for cleavage. Each hammerhead was constructed from two oligoribonucleotides in two different configurations. Although cleavage was observed in all nine cases, the rates of cleavage varied by more than a thousand fold. The presence of RNA secondary structure incompatible with hammerhead formation in the individual oligos may be responsible for the large rate differences. We have also examined the degree of participation of a proposed dimer hammerhead intermediate in one case and conclude that, while such a four-stranded structure can form, it is not the preferred reaction intermediate.


Asunto(s)
Plantas/genética , Empalme del ARN , ARN Ribosómico/genética , Secuencia de Bases , Catálisis , Conformación de Ácido Nucleico , Desnaturalización de Ácido Nucleico , ARN Catalítico , ARN Ribosómico/síntesis química , Relación Estructura-Actividad
5.
Biochimie ; 72(11): 819-23, 1990 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-2085544

RESUMEN

Deoxynucleotides were introduced into a substrate fragment of the hammerhead RNA self-cleaving domain. A substrate lacking the 2' hydroxyl adjacent to the cleavage site showed no detectable cleavage under a variety of reaction conditions. Competition experiments indicate that this fragment binds to the ribozyme with an affinity similar to the all RNA fragment, suggesting that the attacking 2' hydroxyl does not substantially contribute to the binding of substrate to ribozyme. Similar competition experiments with the all DNA substrate indicate a much lower affinity for the ribozyme perhaps due to the lack of other 2' hydroxyls. A substrate containing all deoxy residues except for a ribonucleotide at the cleavage site was also shown to be active.


Asunto(s)
ARN Catalítico/metabolismo , Secuencia de Bases , ADN/síntesis química , Cinética , Datos de Secuencia Molecular , Oligodesoxirribonucleótidos/síntesis química , Oligorribonucleótidos/síntesis química , ARN Catalítico/síntesis química , Especificidad por Sustrato
6.
Am J Surg ; 163(2): 257-9, 1992 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-1739182

RESUMEN

The purpose of the current study was to review the safety of colonoscopy performed by nonfellowship-trained general surgeons. To address this issue, we reviewed more than 1,000 consecutive diagnostic and therapeutic colonoscopies and recorded the complications. This was a multi-institutional study involving seven general surgeons, none of whom had had formal fellowship endoscopic training. Perforation was confirmed by laparotomy, bleeding was defined as that requiring hospitalization and/or transfusion, and cardiopulmonary arrest was self-explanatory. There was one perforation in the diagnostic group and none in the therapeutic group, for a rate of 0.10% overall and 0.12% in diagnostic colonoscopy. There were no instances of bleeding or cardiac arrest. This complication rate of 1 per 1,025 colonoscopic procedures by general surgeons compares favorably with that previously reported by other specialties (p less than 0.001). We conclude that postgraduate endoscopy fellowship is not necessary for general surgeons to become safe colonoscopists.


Asunto(s)
Competencia Clínica , Colonoscopía , Cirugía General , Pólipos del Colon/cirugía , Colonoscopía/efectos adversos , Humanos
7.
J Laryngol Otol ; 106(12): 1072-5, 1992 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-1487663

RESUMEN

During a 25-year period 168 adults and 111 children in Copenhagen County were treated for acute epiglottitis. Four patients, two children and two adults died, of these the two children and one adult had a cardiac arrest on arriving at the hospital. Most children were treated by nasotracheal intubation while only some adults required nasotracheal intubation in order to secure the airway. Our data indicate that intubation of adults with epiglottitis is technically more difficult than in children. The fibrelaryngoscope, a new diagnostic tool, is advocated, and was in this study used to establish the diagnosis in 12 unclear cases of acute epiglottitis. The incidence of acute epiglottitis in children was calculated at 3.2/100,000 with a minor annual variation. As vaccination against Haemophilus influenzae type b becomes more common, the incidence will probably be markedly reduced, maybe even eradicated in children, but in adults the same reduction cannot be expected as the causative agent in this group is less frequently Haemophilus influenzae type b.


Asunto(s)
Epiglotitis/terapia , Intubación Intratraqueal/métodos , Enfermedad Aguda , Adolescente , Adulto , Niño , Preescolar , Epiglotitis/diagnóstico , Epiglotitis/microbiología , Femenino , Tecnología de Fibra Óptica , Predicción , Infecciones por Haemophilus/complicaciones , Humanos , Lactante , Laringoscopios , Masculino , Persona de Mediana Edad
8.
Ugeskr Laeger ; 156(16): 2420-3, 1994 Apr 18.
Artículo en Danés | MEDLINE | ID: mdl-8009704

RESUMEN

During a 27-year period 295 patients in Copenhagen County were treated for acute epiglottitis. One hundred and eight-two were adults and 113 were children. Most children were treated by nasotracheal intubation while only a few adults required nasotracheal intubation in order to secure the airway. The incidence of acute epiglottitis in children less than five years old was calculated to be 8.7/100,000 with minor annual variation. Since vaccination against Haemophilus influenzae type b has been implemented in Denmark from May 1993, this figure will probably be markedly reduced, and the disease even may be even eradicated in children, but in adults the same reduction cannot be expected as the causative agent in this group is less frequently Haemophilus influenzae type b. It is emphasized that this reduced incidence will make it even more important that each department engaged in the treatment of suspected acute epiglottitis have a departmental protocol for management of the condition, so that the future rarity of acute epiglottitis does not cause the mortality rate to rise.


Asunto(s)
Epiglotitis/terapia , Intubación Intratraqueal/métodos , Enfermedad Aguda , Adolescente , Adulto , Anciano , Niño , Preescolar , Epiglotitis/microbiología , Humanos , Intubación Intratraqueal/efectos adversos , Intubación Intratraqueal/tendencias , Persona de Mediana Edad , Nariz , Estudios Retrospectivos
9.
Int J Obes (Lond) ; 31(5): 829-41, 2007 May.
Artículo en Inglés | MEDLINE | ID: mdl-17060928

RESUMEN

OBJECTIVE: Cross-breeding experiments with different mouse strains have successfully been used by many groups to identify genetic loci that predispose for obesity. In order to provide a statistical assessment of these quantitative trait loci (QTL) as a basis for a systematic investigation of candidate genes, we have performed a meta-analysis of genome-wide linkage scans for body weight and body fat. DATA: From a total of 34 published mouse cross-breeding experiments, we compiled a list of 162 non-redundant QTL for body weight and 117 QTL for fat weight and body fat percentage. Collectively, these studies include data from 42 different parental mouse strains and >14,500 individual mice. METHODS: The results of the studies were analyzed using the truncated product method (TPM). RESULTS: The analysis revealed significant evidence (logarithm of odds (LOD) score >4.3) for linkage of body weight and adiposity to 49 different segments of the mouse genome. The most prominent regions with linkage for body weight and body fat (LOD scores 14.8-21.8) on chromosomes 1, 2, 7, 11, 15, and 17 contain a total of 58 QTL for body weight and body fat. At least 34 candidate genes and genetic loci, which have been implicated in regulation of body weight and body composition in rodents and/or humans, are found in these regions, including CCAAT/enhancer-binding protein alpha (C/EBPA), sterol regulatory element-binding transcription factor 1 (SREBP-1), peroxisome proliferator activator receptor delta (PPARD), and hydroxysteroid 11-beta dehydrogenase 1 (HSD11B1). Our results demonstrate the presence of numerous distinct consensus QTL regions with highly significant LOD scores that control body weight and body composition. An interactive physical map of the QTL is available online at (http://www.obesitygenes.org).


Asunto(s)
Peso Corporal/genética , Genoma/genética , Obesidad/genética , Sitios de Carácter Cuantitativo/genética , Tejido Adiposo , Animales , Humanos , Ratones , Especificidad de la Especie
10.
Diabetologia ; 50(7): 1418-22, 2007 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-17464498

RESUMEN

AIMS/HYPOTHESIS: The aim was to identify type 2 diabetes susceptibility regions in 250 German families. SUBJECTS AND METHODS: We conducted a genome-wide linkage scan using 439 short tandem repeat polymorphisms at an average resolution of 7.76 +/- 3.80 cM (Marshfield). In an affected-only-design (affected sib pairs), we performed nonparametric multipoint linkage analyses. Conditional analyses were applied where linkage signals were found in the baseline analyses. RESULTS: We identified two loci with nominal evidence for linkage on chromosomes 1p36.13 and 16p12.2 (D1S3669, 37.05 cM, logarithmic odds ratio [LOD] = 1.49, p = 0.004; D16S403, 43.89 cM, LOD = 1.85, p = 0.002). D16S403 crossed the empirically obtained threshold of genome-wide suggestive significance of LOD = 1.51. Positive findings in those regions have been reported by the following other linkage studies on: (1) symptomatic/clinical gall bladder disease with type 2 diabetes in Mexican Americans from the San Antonio Family Diabetes/Gallbladder Study (LOD = 3.7, D1S1597-D1S407, 29.93-33.75 cM); (2) body size-adiposity in another Mexican American population (D1S1597, LOD = 2.53, 29.93 cM); (3) lipid abnormalities (LOD = 3.1, D1S2826-D1S513, 41.92-60.01 cM); and (4) hypertension in Australian sib pairs (LOD = 3.1, D1S2834-D1S2728, 31.02-33.75 cM); as well as (5) a meta-analysis of four European type 2 diabetes-related genome scans (LOD = 1.09, D16S412, 42.81 cM). In linkage analyses conditional on evidence for linkage at D16S403 we identified a LOD increase (Delta LOD) of 1.55 (p = 0.0075) at D17S2180. Similar conditioning on D17S2180 revealed evidence for interaction with D1S3669 (Delta LOD = 1.67, p = 0.0055), D16S403 (Delta LOD = 1.48, p = 0.0091) and another locus on chromosome 1 where several genome scans have reported evidence for linkage ( approximately 200 cM, Delta LOD = 1.60, p = 0.0066). CONCLUSIONS/INTERPRETATION: Our results and the findings of other studies are consistent with the presence of a locus for a complex metabolic syndrome on chromosome 1p36.13.


Asunto(s)
Cromosomas Humanos Par 16 , Cromosomas Humanos Par 1 , Diabetes Mellitus Tipo 2/genética , Ligamiento Genético , Genómica , Síndrome Metabólico/genética , Mapeo Cromosómico , Femenino , Predisposición Genética a la Enfermedad , Genoma Humano , Alemania , Humanos , Masculino , Oportunidad Relativa , Polimorfismo Genético
11.
Fortschr Kieferorthop ; 55(6): 324-9, 1994 Dec.
Artículo en Alemán | MEDLINE | ID: mdl-7851829

RESUMEN

Ever increasing refinements in orthodontic treatment and the corresponding increase in technical demands are challenges to both the dentist in his/her practice and to the manufacturers of orthodontic materials. One interesting development has been the introduction of "super-elastic" arch wires, which have now been on the market for some years. Such arch wires are characterized by an excellent "shape memory", various levels of super-elasticity, a remarkable hysteresis, and temperature sensitivity. On the basis of findings from temperature controlled tests of arch wires in a "Lloyd 1000 R" testing machine, the following conclusions can be drawn. Shape memory can, from a clinical point of view, be regarded as being a positive feature. "Super-elasticity" is of lesser value, because conventional activation of edgewise arches rarely reaches the level of deformation necessary for super-elasticity to be called into play. Hysteresis and temperature sensitivity make a biomechanical control of the arch wires difficult. Reducing active forces by chilling the archwire brings relief to sore teeth. Whether this possibly leads to an improvement in blood circulation in the periodontal tissue, which would be biologically advantageous, should be made the subject of further research.


Asunto(s)
Diseño de Aparato Ortodóncico , Aparatos Ortodóncicos , Alambres para Ortodoncia , Elasticidad , Humanos , Ensayo de Materiales , Estrés Mecánico
12.
Calcif Tissue Int ; 65(6): 459-65, 1999 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-10594165

RESUMEN

The purpose of the present work was to investigate the infrared (IR) spectrum of shark enameloid, especially with regard to hydroxide and carbonate bands. With thin sections placed directly in the IR beam it was possible to get high concentrations of ions without interfering effects from a dispersion medium (e.g., alkali halides). For comparison, spectra of shark dentin and a geo-apatite were also recorded. In spectra of shark enameloid and geo-apatite medium strong hydroxide absorption bands were found around 3535 cm(-1), and in shark dentin and geo-apatite spectra weak shoulders were observed at about 3570 cm(-1). Hydroxide libration bands at about 740 cm(-1) were found in shark enameloid and geo-apatite spectra; in the latter, also a band at 680 cm(-1). Carbonate bands were found in shark enameloid spectra at 1480 (weak shoulder), 1453, 1423, and 868 cm(-1). In shark dentin spectra there were carbonate bands at 1452, 1417, and 875 cm(-1), and probably also a carbonate band at about 1530 cm(-1) overlapped by an amide II band. Weak carbonate bands were also found in the spectra of the geo-apatite at 1452 cm(-1), and at about 1425 and 880 cm(-1). The relative intensities of the bands at 1453 cm(-1) (contributed from A and B sites) and around 1420 cm(-1) (B sites) changed from shark enameloid to shark dentin, and also from shark enameloid to the geo-apatite. More A sites seem to be occupied by carbonate in shark dentin than in shark enameloid, supposedly owing to fluoride occupation of A sites in shark enameloid. In geo-apatite and shark enameloid there are hydroxide ions hydrogen bonded to fluoride. Both shark enameloid and the geo-apatite are fluoride rich, and geo-apatite seems to have the highest fluoride concentration. There are, however, indications that the hydroxide concentration is also higher in the geo-apatite than in shark enameloid. This can be explained by the much higher carbonate content, and partly also by the higher water content in shark enameloid. There are A sites in geo-apatite and probably also in shark enameloid which are occupied by carbonate, but the proportion of occupied A sites relative to occupied B sites is greater in geo-apatite than in shark enameloid. This difference can be explained by the preference of A sites when the carbonate concentration is very low. On the other hand, for greater amounts of carbonate such as we have in shark enameloid, B sites are preferred.


Asunto(s)
Apatitas/química , Carbonatos/análisis , Esmalte Dental/química , Dentina/química , Hidróxidos/análisis , Tiburones , Animales , Espectrofotometría Infrarroja , Análisis Espectral
13.
Calcif Tissue Res ; 21(2): 115-20, 1976 Oct 12.
Artículo en Inglés | MEDLINE | ID: mdl-791460

RESUMEN

Analysis of human dentine by infrared spectrophotometry suggests that ball-grinding may result in damage of the apatite crystallites. The present study includes further assessments of this effect by X-ray diffraction, infrared spectroscopy, and electron microscopy. Each of three coarse-ground dentine samples (Group I) was divided into three portions of 30 mg. One of these portions was ball-ground for approximately 1 min (Group II), the second portion for 6 min (Group III), and the third portion for 23 min (Group IV). The 002 reflection showed line broadening, most marked from Group II to III. Electron microscopy showed a gradual change in crystallite appearance with increased grinding, most pronounced from Group II to III. These observations indicate that by prolonged grinding a limit is approached where no further changes in the crystallites occur. Electron microscopy also indicated that fracture of the crystallites might have occurred. This was probably accompanied by strains in the lattice. The infrared spectra indicated that no breakdown of the apatite structure had occurred during the entire grinding.


Asunto(s)
Dentina , Apatitas , Dentina/análisis , Dentina/ultraestructura , Técnicas Histológicas , Humanos , Microscopía Electrónica , Espectrofotometría Infrarroja/métodos , Difracción de Rayos X/métodos
14.
Biochemistry ; 30(39): 9464-9, 1991 Oct 01.
Artículo en Inglés | MEDLINE | ID: mdl-1716459

RESUMEN

A hammerhead self-cleaving domain composed of two oligoribonucleotides was used to study the role of divalent metal ions in the cleavage reaction. Cleavage rates were measured as a function of MgCl2, MnCl2, and CaCl2 concentration in the absence or presence of spermine. In the presence of spermine, the rate vs metal ion concentration curves are broader, and lower concentrations of divalent ions are necessary for catalytic activity. This suggests that spermine can promote proper folding of the hammerhead and one or more divalent ions are required for the reaction. Six additional divalent ions were tested for their ability to support hammerhead cleavage. In the absence of spermine, rapid cleavage was observed with Co2+ while very slow cleavage occurred with Sr2+ and Ba2+. No detectable specific cleavage was observed with Cd2+, Zn2+, or Pb2+. However, in the presence of 0.5 mM spermine, rapid cleavage was observed with Zn2+ and Cd2+, and the rate with Sr2+ was increased, indicating that while these three ions could not promote proper folding of the hammerhead they were able to stimulate cleavage. These results suggest certain divalent ions either participate directly in the cleavage mechanism or are specifically involved in stabilizing the tertiary structure of the hammerhead. Additionally, an altered divalent metal ion specificity was observed when a unique phosphorothioate linkage was inserted at the cleavage site. The substitution of a sulfur for a nonbridging oxygen atom substantially reduced the affinity of an important Mg2+ ion necessary for efficient cleavage. In contrast, the reaction proceeds normally with Mn2+, presumably due to its ability to coordinate with both oxygen and sulfur.(ABSTRACT TRUNCATED AT 250 WORDS)


Asunto(s)
Metales/química , ARN Catalítico/química , ARN/química , Secuencia de Bases , Cationes Bivalentes , Hidrólisis , Cinética , Datos de Secuencia Molecular , Relación Estructura-Actividad , Azufre/química
15.
Am J Orthod Dentofacial Orthop ; 108(3): 256-61, 1995 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-7661141

RESUMEN

Titanium tetrafluoride (TiF4) was applied to acid-etched enamel surfaces to study the effect on surface structure and tensile bond strength of orthodontic brackets. Three groups of 20 premolars each were compared in debonding tests. Group I received a 1% and Group II received a 4% topical TiF4 treatment after acid etching. Group III served as control, that is, no fluoride solution was applied to the enamel after acid etching. Each treatment lasted 60 seconds followed by a thorough rinsing with water for 30 seconds. Brackets were bonded on all teeth with the same procedure. All premolars were then placed in a water bath at 37 degrees C. Ten teeth from each group were debonded after 24 hours, and the remaining teeth were debonded after 6 months. Results indicated that the application of 1% and 4% TiF4 solutions on etched enamel surfaces did not alter the tensile bond strength significantly after 24 hours and 6 months. The scanning electron microscope (SEM) examination of the surface structure demonstrated the presence of extensive reaction products, which covered enamel surfaces and appeared to interfere with etch patterns. It was concluded that the application of TiF4 solutions to etched enamel surfaces before bonding will not have an adverse effect on the tensile strength of orthodontic attachments.


Asunto(s)
Grabado Ácido Dental , Recubrimiento Dental Adhesivo , Esmalte Dental/efectos de los fármacos , Fluoruros/farmacología , Soportes Ortodóncicos , Titanio/farmacología , Adhesivos , Administración Tópica , Diente Premolar , Bisfenol A Glicidil Metacrilato , Desconsolidación Dental , Esmalte Dental/ultraestructura , Fluoruros/administración & dosificación , Humanos , Microscopía Electrónica de Rastreo , Tercer Molar , Porosidad , Propiedades de Superficie , Resistencia a la Tracción , Titanio/administración & dosificación
16.
Biochemistry ; 32(48): 13040-5, 1993 Dec 07.
Artículo en Inglés | MEDLINE | ID: mdl-8241158

RESUMEN

The log of the rate of the chemical step of hammerhead cleavage in Mg2+ increases linearly with pH between pH 5.7 and 8.9. A slope of approximately 1 indicates that a single deprotonation is required for cleavage. Hammerhead pH-rate profiles with Ca2+, Mn2+, Co2+, and Cd2+ correlate well with the pKa's of these ions in water. This relationship between the pKa's and the pH-rate profile suggests that a metal hydroxide bound to the hammerhead RNA acts as the base in the cleavage mechanism.


Asunto(s)
Metales/química , ARN Catalítico/química , Secuencia de Bases , Cationes Bivalentes/química , Concentración de Iones de Hidrógeno , Hidrólisis , Hidróxidos/química , Datos de Secuencia Molecular , ARN Viral/química , Solventes/química
17.
Am J Orthod Dentofacial Orthop ; 104(1): 48-50, 1993 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-8322723

RESUMEN

A light-curing, fluoride-releasing adhesive (VP 862, Vivadent, Liechtenstein) for bonding of brackets has been produced for inhibition of white spot lesions during orthodontic treatment. The tensile bond strength after 24 hours and 6 months was investigated and compared with two other light-curing adhesives (Transbond, 3M Corp., Monrovia, Calif., and Heliosit-Orthodontic, Vivadent, Liechtenstein) and two chemical-curing adhesives (Concise, 3M, Monrovia Calif., and Saga Bond, Saga Orthodontics, Kongsvinger, Norway). All adhesives produced adequate strength to be recommended for clinical use. The light-curing adhesives produced slightly lower bond strengths after 24 hours and 6 months, except Transbond, which showed an increase in bond strength in this period approaching the two chemical adhesives.


Asunto(s)
Adhesivos , Recubrimiento Dental Adhesivo , Cementos Dentales , Fluoruros Tópicos/administración & dosificación , Soportes Ortodóncicos , Cementos de Resina , Bisfenol A Glicidil Metacrilato , Cariostáticos , Resinas Compuestas , Caries Dental/prevención & control , Análisis del Estrés Dental , Humanos , Ensayo de Materiales , Compuestos Orgánicos , Ácidos Polimetacrílicos , Resistencia a la Tracción
18.
J Prosthet Dent ; 73(5): 486-91, 1995 May.
Artículo en Inglés | MEDLINE | ID: mdl-7658401

RESUMEN

An in vitro test is described that simulates the in vivo fate of a denture adhesive, namely destruction, dilution, and dissolution of the adhesive, by repeated measurement of tensile bond strength for the adhesive in isotonic saline over time. The bond strengths were measured under two different settings of the testing machine. The main compositions of three denture adhesive pastes, Fittydent, Fixodent, and Super Poli-Grip and one powder adhesive, Super Wernet's, were determined by infrared spectroscopy. The tensile bond strengths of these adhesives and those of pure tragacanth gum were subjected to a three-way analysis of variance. The Fittydent and Super Poli-Grip adhesives exhibited the best results over time. The most appropriate of the described methods for testing denture adhesives seem useful; however, when seen in relation to the results of a published clinical study where the patients were asked to evaluate the retention and the duration of some of these adhesives, there are indications that the clinical validity of the method might be improved if paste adhesives are tested at temperatures above 35 degrees C.


Asunto(s)
Adhesivos , Retención de Dentadura/métodos , Adhesivos/química , Análisis de Varianza , Carboximetilcelulosa de Sodio , Materiales Dentales , Análisis del Estrés Dental/instrumentación , Análisis del Estrés Dental/métodos , Humanos , Ensayo de Materiales/instrumentación , Ensayo de Materiales/métodos , Fosfatos , Polímeros , Polivinilos , Espectrofotometría Infrarroja , Resistencia a la Tracción , Tragacanto
19.
Acta Anaesthesiol Scand ; 38(2): 121-5, 1994 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-7909641

RESUMEN

Xenon is a more potent anesthetic than nitrous oxide, and give more profound analgesia. This investigation was performed to assess the potential of xenon for becoming an anesthetic inspite of its high manufacturing cost. Seven ASA I-II patients undergoing cholecystectomy (n = 4), hernia repair (n = 2), or mammoplasty (n = 1) were studied. Denitrogenation by 15-20 min of oxygen breathing under propofol anesthesia was followed by fentanyl-supplemented xenon anesthesia administered via an automatic minimal flow system which held the oxygen concentration at 30%. Xenon anesthesia lasted 76-228 min and 8-14 l of xenon (ATPD) was used, of which 5.6-8.1 l was expended during the first 15 min. Anesthesia appeared to be satisfactory, and the patients woke up rapidly after xenon was discontinued. The automatic system made minimal flow xenon anesthesia easy to administer, but nitrogen accumulation is still a problem. Assuming a xenon price of 10 US$ per litre, the average cost for xenon was about 65 US$ for the first 15 min and then about 25 US$ for each subsequent hour of anesthesia.


Asunto(s)
Anestesia por Inhalación , Xenón , Adulto , Anciano , Anestesia por Inhalación/instrumentación , Anestesia por Inhalación/métodos , Anestesia Intravenosa , Dióxido de Carbono/análisis , Cromatografía de Gases , Femenino , Fentanilo , Humanos , Masculino , Persona de Mediana Edad , Nitrógeno/análisis , Oxígeno/administración & dosificación , Oxígeno/análisis , Propofol , Bromuro de Vecuronio , Ventiladores Mecánicos , Xenón/administración & dosificación , Xenón/análisis , Xenón/metabolismo
20.
Eur J Anaesthesiol ; 15(2): 230-3, 1998 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-9587731

RESUMEN

The isoflurane-saving and CO2-retaining effects of a charcoal filter were compared with a Siemens standard heat and moisture (HME) exchanger and an emptied specimen (dummy). Isoflurane was delivered during the inspiratory phase and consumption investigated at 10, 15 and 25 cycles min-1. The investigation was performed by ventilation with humidified air with a constant end-tidal CO2 and temperature. For a comparison, isoflurane was delivered in a conventional manner via the ventilator. The arrangement with a charcoal filter reduced the isoflurane consumption by a factor of 2.0-2.6, depending on ventilatory rate. Most of the saving was a result of the method of isoflurane delivery (factor 1.4-2.0), while adding the reflector gave a further reduction (factor 1.3-1.5). One circumstance that reduced the net efficiency of the charcoal filter was that it also reflected CO2; consequently, total minute ventilation had to be increased to maintain constant end-tidal CO2.


Asunto(s)
Anestesiología/instrumentación , Anestésicos por Inhalación/química , Carbón Orgánico , Isoflurano/química , Adsorción , Dióxido de Carbono/análisis , Filtración/métodos
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