RESUMEN
High speed magnetic resonance imaging (MRI) and short diffusion times are used to investigate the appearance of restricted diffusion in three different models of cerebral infarction. The models are: the middle cerebral artery occlusion (MCAO) model in the rat, the carotid occlusion model in the gerbil, and the Rose Bengal microvascular occlusion model in the rat. All three were investigated for 16 b-values equally spaced between 10 and 1510 s/mm2 using two distinct experiments. In the ct (constant time) experiment, the diffusion time was held constant at 11.7 ms while the b-value was varied with the gradient strength. In the cg (constant gradient) experiment, the gradient strength was held constant and the b-value increased by varying the diffusion time from 4.4 to 11.7 ms. A monoexponential decay of the signal intensity with b-value in the ct experiment accompanied by nonmonoexponential (NME) decay in the cg experiment is indicative of restricted diffusion. As this phenomenon is detectable only at short diffusion times, it cannot be due to restriction by impermeable membranes, and we have thus termed this apparent restriction. For the MCAO model and the carotid occlusion model, apparent restriction was found both inside the infarct territory and in some regions outside it. No definite evidence for restriction was found for the Rose Bengal model, which was, however, only studied from 24 h post-insult.
Asunto(s)
Infarto Cerebral/diagnóstico , Imagen por Resonancia Magnética , Animales , Gerbillinae , Imagen por Resonancia Magnética/métodos , Masculino , Modelos Estructurales , Ratas , Ratas WistarRESUMEN
Arthrodesis of the proximal interphalangeal joint in horses, with 2 screws crisscrossing the joint, was compared with arthrodesis achieved by placement of 3 screws crossing the joint parallel to the long axis of the bone. The comparison was made by means of radiography, gross and histologic examinations, and motion evaluation. Additionally, the fused 1st and 2nd phalanges resulting from each method were subjected to breaking forces. Motion evaluation and direct examination of the fused area demonstrated that either procedure can be used to achieve arthrodesis consistently, and the breaking procedure indicated that the fused joints were as strong or stronger than areas penetrated by the cortical screws used in internal fixation. The fused area resulting from the parallel procedure was stronger than that from the crisscross procedure. The parallel procedure was easier, gave better alignment of 1st and 2nd phalanges, and was prone to less error in screw placement. It was concluded that arthrodesis by either procedure was satisfactory for treating osteoarthritis and related problems of the proximal interphalangeal joint in horses, but that the parallel procedure created a superior union between the 1st and 2nd phalanges during the first 120 postoperative days.
Asunto(s)
Artrodesis/veterinaria , Caballos/cirugía , Articulación del Dedo del Pie/cirugía , Animales , Artrodesis/métodos , Fenómenos Biomecánicos , Tornillos Óseos/veterinaria , Miembro Anterior , Masculino , Cicatrización de HeridasRESUMEN
The authors examined the mortality experience of employees whose work assignments involved development or production of styrene-based products. To investigate potential relationships between mortality and work exposure in the diverse chemical operations under study, a multiple agent approach to exposure categorization was adopted. Mortality was less than that of the corresponding U.S. white male population and was consistent with that of an industrial comparison group. Although deaths due to malignant neoplasms were fewer than expected for the total cohort, an increase in lymphatic leukemia was observed among a subgroup of employees who had exposure to polymer extrusion fumes, solvents, and colorants. However, no relationship was found with duration or intensity of exposures experiences by these employees, and the etiology of the lymphatic leukemias was not established. The approach used to characterize exposure in this study may have application in other epidemiologic investigations involving complex work environments.
Asunto(s)
Enfermedades Profesionales/mortalidad , Estirenos/efectos adversos , Benceno/efectos adversos , Industria Química , Colorantes/efectos adversos , Humanos , Leucemia/inducido químicamente , Masculino , Neoplasias/inducido químicamente , Enfermedades Profesionales/inducido químicamente , Estudios RetrospectivosAsunto(s)
Industria Química , Polvo , Enfermedades Profesionales/mortalidad , Hidróxido de Sodio , Anciano , Enfermedades Cardiovasculares/mortalidad , Exposición a Riesgos Ambientales , Humanos , Persona de Mediana Edad , Neoplasias/mortalidad , Enfermedades Profesionales/inducido químicamente , Factores de TiempoRESUMEN
Previous studies have reported on employee populations exposed coincidentally to vinylidene chloride in copolymer processes using vinyl chloride. The current study examines the mortality and health examination findings of 138 employees exposed to measured levels of vinylidene chloride where vinyl chloride was not used as a copolymer. There were no findings statistically related or individually attributable to vinylidene chloride exposure in this employee population. It is recommended that additional epidemiological studies be undertaken to develop data on chronic exposure to vinylidene chloride.