RESUMEN
Uterine and placental infections are the leading cause of abortion, stillbirth, and preterm delivery in the mare. Whereas uterine and placental infections in women have been studied extensively, a comprehensive examination of the pathogenic processes leading to this unsatisfactory pregnancy outcome in the mare has yet to be completed. Most information in the literature relating to late-term pregnancy loss in mares is based on retrospective studies of clinical cases submitted for necropsy. Here we report the development and application of a novel approach, whereby transgenically modified bacteria transformed with lux genes of Xenorhabdus luminescens or Photorhabdus luminescens origin and biophotonic imaging are utilized to better understand pathogen-induced preterm birth in late-term pregnant mares. This technology uses highly sensitive bioluminescence imaging camera systems to localize and monitor pathogen progression during tissue invasion by measuring the bioluminescent signatures emitted by the lux-modified pathogens. This method has an important advantage in that it allows for the potential tracking of pathogens in vivo in real time and over time, which was hitherto impossible. Although the application of this technology in domestic animals is in its infancy, investigators were successful in identifying the fetal lungs, sinuses, nares, urinary, and gastrointestinal systems as primary tissues for pathogen invasion after experimental infection of pregnant mares with lux-modified Escherichia coli. It is important that pathogens were not detected in other vital organs, such as the liver, brain, and cardiac system. Such precision in localizing sites of pathogen invasion provides potential application for this novel approach in the development of more targeted therapeutic interventions for pathogen-related diseases in the equine and other domestic species.
Asunto(s)
Infecciones por Escherichia coli/veterinaria , Escherichia coli/aislamiento & purificación , Enfermedades de los Caballos/microbiología , Enfermedades Uterinas/veterinaria , Animales , Infecciones por Escherichia coli/diagnóstico , Infecciones por Escherichia coli/microbiología , Femenino , Enfermedades de los Caballos/diagnóstico , Caballos , Mediciones Luminiscentes , Photorhabdus/genética , Embarazo , Nacimiento Prematuro/prevención & control , Nacimiento Prematuro/veterinaria , Enfermedades Uterinas/diagnóstico , Enfermedades Uterinas/microbiologíaRESUMEN
Consumption of wild-type (toxic) endophyte-infected tall fescue (E+) by horses during late gestation is known to adversely affect pregnancy outcome; however, little is known of the potential disruptive consequences of E+ consumption by mares during the critical phases of placentation and fetal development in early pregnancy. The objective of this study was to evaluate the detrimental effects of feeding E+ to mares during early gestation. Mares (n = 12) paired by stage of gestation (d 65 to 100) were assigned to diets (six per diet) consisting of endophyte-free (E-) or E+ tall fescue seed (50% E- or E+ tall fescue seed, 45% sweet feed, and 10% molasses fed at 1.0% of BW/d). Mares also had ad libitum access to E+ or E- annual ryegrass hay, and were fed diets for 10 d. Following removal from the tall fescue diet on d 11, mares were placed on common bermudagrass pasture and monitored until d 21. Morning and evening rectal temperatures were recorded and daily blood samples were collected for progesterone and prolactin (PRL) analyses, whereas samples for 3,4-dihydroxyphenyl acetic acid (a catecholamine metabolite) analysis were collected on alternate days. For clinical chemistry analysis, blood samples were collected on d 0, 5, 10 and 21. Daily urine samples were collected for ergot alkaloid analysis, and ultrasonography was performed for presence of echogenic material in fetal fluids. Rectal temperatures (E+ 37.76+/-0.03; E- 37.84+/-0.03 degrees C) and serum PRL concentrations (E+ 14.06< or =0.76; E- 12.11+/-0.76 ng/mL) did not differ (P = 0.96) between treatments. Measuring the change in basal serum concentration from d 0 over time, progesterone concentrations did not differ (-0.64 +/-1.49 and -0.55+/-1.47 ng/mL for E+ and E- mares, respectively). There was no negative pregnancy outcome, and ultrasonography indicated no increase in echogenic material in fetal fluids. Plasma 3,4-dihydroxyphenyl acetic acid concentrations decreased (P < 0.05) in E+ compared with E- mares (2.1+/-0.14 and 4.4+/0.43 ng/mL, respectively). Urinary ergot alkaloid concentration was greater (P < 0.01) in mares consuming E+ compared with E- (532.12+/- 52.51 and 13.36+/-2.67 ng/mg of creatinine, respectively). Although no fetal loss was observed during the current study, elevated concentrations of urinary ergot alkaloid were consistent with depressed endogenous catecholamine activity, suggestive of an endocrine disruptive effect of hypothalamic origin.
Asunto(s)
Ácido 3,4-Dihidroxifenilacético/sangre , Acremonium/crecimiento & desarrollo , Alcaloides de Claviceps/efectos adversos , Desarrollo Fetal , Caballos/fisiología , Lolium/microbiología , Alimentación Animal , Animales , Alcaloides de Claviceps/farmacocinética , Alcaloides de Claviceps/orina , Femenino , Desarrollo Fetal/efectos de los fármacos , Contaminación de Alimentos , Caballos/sangre , Caballos/embriología , Caballos/orina , Embarazo , Resultado del Embarazo/veterinaria , Progesterona/sangre , Prolactina/sangre , Distribución AleatoriaRESUMEN
Structural stability of the extracellular matrix is primarily a consequence of fibrillar collagen and the extent of cross-linking. The relationship between collagen self-assembly, consequent fibrillar shape and mechanical properties remains unclear. Our laboratory developed a model system for the preparation of self-assembled type I collagen fibers with fibrillar substructure mimicking the hierarchical structures of tendon. The present study evaluates the effects of pH and temperature during self-assembly on fibrillar structure, and relates the structural effects of these treatments on the uniaxial tensile mechanical properties of self-assembled collagen fibers. Results of the analysis of fibril diameter distributions and mechanical properties of the fibers formed under the different incubation conditions indicate that fibril diameters grow via the lateral fusion of discrete approximately 4 nm subunits, and that fibril diameter correlates positively with the low strain modulus. Fibril diameter did not correlate with either the ultimate tensile strength or the high strain elastic modulus, which suggests that lateral aggregation and consequently fibril diameter influences mechanical properties during small strain mechanical deformation. We hypothesize that self-assembly is mediated by the formation of fibrillar subunits that laterally and linearly fuse resulting in fibrillar growth. Lateral fusion appears important in generating resistance to deformation at low strain, while linear fusion leading to longer fibrils appears important in the ultimate mechanical properties at high strain.
Asunto(s)
Colágeno/química , Colágeno/fisiología , Animales , Fenómenos Biomecánicos , Colágeno/ultraestructura , Matriz Extracelular/química , Matriz Extracelular/fisiología , Glicina , Concentración de Iones de Hidrógeno , Técnicas In Vitro , Sustancias Macromoleculares , Microscopía Electrónica , Ratas , Cloruro de Sodio , Temperatura , Tendones/química , Tendones/fisiologíaRESUMEN
Fibrous collagen networks are the major elements that provide mechanical integrity to tissues; they are composed of fiber forming collagens in combination with proteoglycans (PGs). Using uniaxial tensile tests we have studied the viscoelastic mechanical properties of rat tail tendon (RTT) fibers and self-assembled collagen fibers that were stored at 22 degrees C and 1 atm of pressure. Our results indicate that storage of RTT and self-assembled type I collagen fibers results in increased elastic and viscous components of the stress-strain behavior consistent with the hypothesis that storage causes the introduction of crosslinks. Analysis of the elastic and viscous mechanical data suggests that the elastic constant of the collagen molecule in RTT is about 7.7 GPa. Measurement of the viscous component of the stress-strain curves for RTTs and self-assembled collagen fibers suggests that PGs may increase the viscous component and effectively increase the collagen fibril length.
Asunto(s)
Colágeno/fisiología , Tendones/fisiología , Animales , Presión Atmosférica , Fenómenos Biomecánicos , Colágeno/química , Elasticidad , Femenino , Ratas , Ratas Sprague-Dawley , Estrés Mecánico , Cola (estructura animal) , Temperatura , Resistencia a la Tracción , Conservación de Tejido , ViscosidadRESUMEN
Collagen is the primary structural element in extracellular matrices. In the form of fibers it acts to transmit forces, dissipate energy, and prevent premature mechanical failure in normal tissues. Deformation of collagen fibers involves molecular stretching and slippage, fibrillar slippage, and, ultimately, defibrillation. Our laboratory has developed a process for self-assembly of macroscopic collagen fibers that have structures and mechanical properties similar to rat tail tendon fibers. The purpose of this study is to determine the effects of subfibrillar orientation and decorin incorporation on the mechanical properties of collagen fibers. Self-assembled collagen fibers were stretched 0-50% before cross-linking and then characterized by microscopy and mechanical testing. Results of these studies indicate that fibrillar orientation, packing, and ultimate tensile strength can be increased by stretching. In addition, it is shown that decorin incorporation increases ultimate tensile strength of uncross-linked fibers. Based on the observed results it is hypothesized that decorin facilitates fibrillar slippage during deformation and thereby improves the tensile properties of collagen fibers.
Asunto(s)
Colágeno/química , Colágeno/fisiología , Proteoglicanos/química , Proteoglicanos/fisiología , Animales , Fenómenos Biomecánicos , Fenómenos Biofísicos , Biofisica , Colágeno/ultraestructura , Reactivos de Enlaces Cruzados , Decorina , Proteínas de la Matriz Extracelular , Técnicas In Vitro , Sustancias Macromoleculares , Microscopía Electrónica , Conformación Proteica , Proteoglicanos/ultraestructura , Ratas , Ratas Sprague-Dawley , Tendones/química , Resistencia a la Tracción , Ácidos UrónicosRESUMEN
Mineralizing biological tissues are complex bioceramic-biopolymer composites engineered for a variety of functions. The organic and inorganic constituents, morphology, location, orientation, crystallinity and interactions exhibit materials or extremely fine microstructure, unique mechanical and physical properties with high strength and fracture toughness compared to the individual constituents. An understanding of mineralization, ultrastructural organization and interfacial bonding forces in mineralizing biological composite tissues, such as bone, may provide new strategies and techniques for the production of a novel class of man-made organic-ceramic composites. The present study explores the use of the organic matrix remaining after removal of the mineral phase by chelation with EDTA or solubilizing in HCl as a template for mineral deposition and the production of mineral-organic composites. Different pH conditions are employed to alter the inorganic phase which is deposited within the organic matrix. Mechanical testing and ultrastructural evaluations are carried out for characterization.
Asunto(s)
Matriz Ósea/metabolismo , Animales , Fenómenos Biomecánicos , Biopolímeros , Matriz Ósea/fisiología , Calcificación Fisiológica/fisiología , Bovinos , Quelantes , Resinas Compuestas/normas , Ácido Edético , Microanálisis por Sonda Electrónica , Fracturas del Fémur/patología , Fémur/metabolismo , Ácido Clorhídrico , Concentración de Iones de Hidrógeno , Microscopía Electrónica de Rastreo , Espectroscopía Infrarroja por Transformada de FourierRESUMEN
Increased vascular collagen content is a major feature of pulmonary vascular remodeling. The functional role of excess collagen in decreasing pulmonary vascular compliance has not been established. We determined whether there was a correlation between hydroxyproline content of rat pulmonary artery segments and elastance (EPA) of the pulmonary artery bed during development of hypoxic pulmonary hypertension (10% O2, 10 d) and normoxic recovery. EPA was measured by air-filled pressure-volume curves. After 10 d of hypoxia, hydroxyproline content increased approximately 2-fold in large segments (1,200-250 microns in diameter) but not significantly in small segments (> 250 microns). Elastance increased from 87 +/- 6 (SEM) to 145 +/- 8 mm Hg/ml (p < 0.05) within 5 d of hypoxia and returned to control value 3 wk after recovery. There was a correlation between collagen content and EPA in large segments during development of hypertension; no correlation was found during recovery from hypoxia. The ratio of hydroxyproline to total protein was unchanged in large segments after recovery from hypoxia but was increased in small segments after recovery. We conclude that increased collagen in large pulmonary arteries directly influences EPA during the development of hypoxic pulmonary hypertension.
Asunto(s)
Colágeno/metabolismo , Hipertensión Pulmonar/fisiopatología , Arteria Pulmonar/fisiopatología , Animales , Elasticidad , Hidroxiprolina/análisis , Hipertensión Pulmonar/diagnóstico por imagen , Hipertensión Pulmonar/metabolismo , Hipertensión Pulmonar/patología , Técnicas In Vitro , Masculino , Proteínas/análisis , Arteria Pulmonar/diagnóstico por imagen , Arteria Pulmonar/metabolismo , Arteria Pulmonar/patología , Radiografía , Ratas , Ratas Sprague-DawleyRESUMEN
This study involves comparison of the mechanical properties of reconstituted collagen fibres with those of collagen fibres obtained from rat tail tendons. Reconstituted collagen fibres were cross-linked in the presence of glutaraldehyde vapour for 2 and 4 d or using a combination of severe dehydration and carbodiimide treatment. Ultimate tensile strengths for reconstituted fibres cross-linked with glutaraldehyde ranged from 50 to 66 MPa while those cross-linked by severe dehydration and carbodiimide treatment had ultimate tensile strengths between 24 and 31 MPa. Rat tail tendon fibres had tensile strengths that ranged from 33 to 39 MPa. These results indicate that high-strength collagen fibres can be reconstituted in vitro and that these fibres may be useful in repair of dermal, dental, cardiovascular and orthopaedic defects.
Asunto(s)
Colágeno/fisiología , Tendones/fisiología , Animales , Técnicas In Vitro , Ratas , Ratas Endogámicas , Estrés Mecánico , Cola (estructura animal)/fisiología , Resistencia a la TracciónRESUMEN
Measurement and calculation of the mechanical properties of the aorta depend on a number of factors, including the degree of surgical invasion, vasomotor tone, tissue hydration, physical contact (i.e., the presence of a strain gauge), and the use of inside or outside diameter. Measurements on the aorta using angiography, transit-time determination, and echocardiographic techniques yield the most consistent values for parameters, including PVD, Ep, and Eo. Values of these parameters are listed in Table 7 and range from about 8 to 12.0% (PVD), 337 to 741 g/cm2 (Ep), and 0.33 to 3.6 x 10(6) dyn/cm2 (Eo) for human ascending aorta. Measurements made with invasive techniques tend to result in lower values of PVD and higher values of elastic moduli. Modeling studies focus on predicting the mechanical properties of a viscoelastic, anisotropic tube. Difficulty arises in modeling aorta because of hysteresis and the large deformations that are associated with physiologic loading patterns. Various forms of the strain-energy density function have been used to model relationships between stress and strain in three dimensions; however, they have limited value in understanding the mechanism of time-dependent stress transfer between fibrous and nonfibrous components found in aortic tissue. The ultimate utility of these models will include improved understanding of the physical basis of deformation of this important tissue and the mechanisms of premature failure associated with different disease processes.