Failure of an Actinomyces pyogenes vaccine to protect sheep against an intravenous challenge

The immunity conferred by an A. pyogenes bacterin-toxoid was evaluated in sheep, using an intravenous challenge system. Three sheep were vaccinated and 3 served as controls. The vaccinated sheep were not protected against pyogenic conditions. High antitoxin levels were induced by vaccination but could not be associated with protection against infection. Antibacterial antibody levels elicited with initial vaccination dropped progressively with the 2nd and 3rd vaccinations. Nevertheless, these antibodies did not seem to be necessary for protection against A. pyogenes conditions.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.mn201

Model-based cap thickness and peak cap stress prediction for carotid MRI

A rupture-prone carotid plaque can potentially be identified by calculating the peak cap stress (PCS). For these calculations, plaque geometry from MRI is often used. Unfortunately, MRI is hampered by a low resolution, leading to an overestimation of cap thickness and an underestimation of PCS. We developed a model to reconstruct the cap based on plaque geometry to better predict cap thickness and PCS. We used histological stained plaques from 34 patients. These plaques were segmented and served as the ground truth. Sections of these plaques contained 93 necrotic cores with a cap thickness <0.62 mm which were used to generate a geometry-based model. The histological data was used to simulate in vivo MRI images, which were manually delineated by three experienced MRI readers. Caps below the MRI resolution (n = 31) were (digitally removed and) reconstructed according to the geometry-based model. Cap thickness and PCS were determined for the ground truth, readers, and reconstructed geometries. Cap thickness was 0.07 mm for the ground truth, 0.23 mm for the readers, and 0.12 mm for the reconstructed geometries. The model predicts cap thickness significantly better than the readers. PCS was 464 kPa for the ground truth, 262 kPa for the readers and 384 kPa for the reconstructed geometries. The model did not predict the PCS significantly better than the readers. The geometry-based model provided a significant improvement for cap thickness estimation and can potentially help in rupture-risk prediction, solely based on cap thickness. Estimation of PCS estimation did not improve, probably due to the complex shape of the plaques

High shear stress relates to intraplaque haemorrhage in asymptomatic carotid plaques

Background and aims Carotid artery plaques with vulnerable plaque components are related to a higher risk of cerebrovascular accidents. It is unknown which factors drive vulnerable plaque development. Shear stress, the frictional force of blood at the vessel wall, is known to influence plaque formation. We evaluated the association between shear stress and plaque components (intraplaque haemorrhage (IPH), lipid rich necrotic core (LRNC) and/or calcifications) in relatively small carotid artery plaques in asymptomatic persons. Methods Participants (n = 74) from the population-based

An MRI-based method to register patient specific wall shear stress data to histology

Wall shear stress (WSS), the frictional force exerted on endothelial cells by blood flow, is hypothesised to influence atherosclerotic plaque growth and composition. We developed a methodology for image registration of MR and histology images of advanced human carotid plaques and corresponding WSS data, obtained by MRI and computational fluid dynamics. The image registration method requires four types of input images, in vivo MRI, ex vivo MRI, photographs of transversally sectioned plaque tissue and histology images. These images are transformed to a shared 3D image domain by applying a combination of rigid and non-rigid registration algorithms. Transformation matrices obtained from registration of these images are used to transform subject-specific WSS data to the shared 3D image domain as well. WSS values originating from the 3D WSS map are visualised in 2D on the corresponding lumen locations in the histological sections and divided into eight radial segments. In each radial segment, the correlation between WSS values and plaque composition based on histological parameters can be assessed. The registration method was successfully applied to two carotid endarterectomy specimens. The resulting matched contours from the imaging modalities had Hausdorff distances between 0.57 and 0.70 mm, which is in the order of magnitude of the in vivo MRI resolution. We simulated the effect of a mismatch in the rigid registration of imaging modalities on WSS results by relocating the WSS data with respect to the stack of histology images. A 0.6 mm relocation altered the mean WSS values projected on radial bins on average by 0.59 Pa, compared to the output of original registration. This mismatch of one image slice did not change the correlation between WSS and plaque thickness. In conclusion, we created a method to inves

Association between Intraplaque Hemorrhage and Vascular Remodeling in Carotid Arteries: The Plaque at RISK (PARISK) Study

Introduction: Vascular remodeling is a compensatory enlargement of the vessel wall in response to atherosclerotic plaque growth. We aimed to investigate the association between intraplaque hemorrhage (IPH), vascular remodeling, and luminal dimensions in recently symptomatic patients with mild to moderate carotid artery stenosis in which the differences in plaque size were taken into account. Materials and Methods: We assessed vessel dimensions on MRI of the symptomatic carotid artery in 164 patients from the Plaque At RISK study. This stud

Plaque composition as a predictor of plaque ulceration in carotid artery atherosclerosis: The plaque at RISK study

BACKGROUND AND PURPOSE: Plaque ulceration is a marker of previous plaque rupture. We studied the association between atherosclerotic plaque composition at baseline and plaque ulceration at baseline and follow-up. MATERIALS AND METHODS: We included symptomatic patients with a carotid stenosis of ,70% who underwent MDCTA and MR imaging at baseline (n=180). MDCTA was repeated at 2 years (n=73). We assessed the presence of ulceration using MDCTA. Baseline MR imaging was used to assess the vessel wall volume and the presence and volume of plaque components (intraplaque hemorrhage, lipid-rich necrotic core, and calcifications) and the fibrous cap status. Associations at baseline were evaluated with binary logistic regression and reported with an OR and its 95% CI. Simple statistical testing was performed in the follow-up analysis. RESULTS: At baseline, the prevalence of plaque ulceration was 27% (49/180). Increased wall volume (OR = 12.1; 95% CI, 3.5-42.0), higher relative lipid-rich necrotic core (OR= 1.7; 95% CI, 1.3-2.2), higher relative intraplaque hemorrhage volume (OR= 1.7; 95% CI, 1.3-2.2), and a thin-or-ruptured fibrous cap (OR = 3.4; 95% CI, 1.7-6.7) were associated with the presence of ulcerations at baseline. In 8% (6/73) of the patients, a new ulcer developed. Plaques with a new ulceration at follow-up had at baseline a larger wall volume (1.04 cm3 [IQR, 0.97-1.16 cm3] versus 0.86 cm3 [IQR, 0.73-1.00 cm3]; P=.029), a larger relative lipid-rich necrotic core volume (23% [IQR, 13-31%] versus 2% [IQR, 0-14%]; P=.002), and a larger relative intraplaque hemorrhage volume (14% [IQR, 8-24%] versus 0% [IQR, 0-5%]; P<.001). CONCLUSIONS: Large atherosclerotic plaques and plaques with intraplaque hemorrhage and lipid-rich necrotic cores were associated with plaque ulcerations at baseline and follow-up

Aborto em bovinos devido à intoxicação por Tetrapterys acutifolia (Malpighiaceae)

Esse estudo teve por objetivo demonstrar experimentalmente que Tetrapterys acutifolia Cav. (fam. Malpighiaceae) é capaz de provocar aborto em bovinos e caracterizar as alterações clínico-patológicas nas vacas e nos fetos. Estas plantas são responsáveis por significativo número de mortes em bovinos com mais de um ano de idade, especialmente nos Estados de Rio de Janeiro e São Paulo, mas até agora não havia sido comprovado experimentalmente seu efeito abortivo em bovinos. Os experimentos foram realizados no município de Barra do Piraí, RJ. Quatro vacas de descarte receberam brotos e folhas novas frescas de T. acutifolia, coletadas em propriedades vizinhas, nas doses de 2,5g/kg/dia, 5,0g/kg/dia (2 vacas) e 10g/kg/dia, até ocorrer o abortamento. O quadro clínico nas vacas caracterizou-se por arritmia cardíaca, tremores musculares, anorexia, ascite, jugular ingurgitada, edema de peito e barbela e aborto (23-76 dias após o início da ingestão da planta); todas as vacas abortaram. Das quatro vacas apenas uma (a que recebeu 10g/kg/dia) morreu 36 dias após o abortamento, com sintomas de insuficiência cardíaca. O exame necroscópico dos fetos/natimortos revelou hidrotórax, hidropericárdio, hidroperitônio e congestão hepática; ao corte do miocárdio, verificaram-se áreas pálidas. No exame histológico havia edema intersticial com fibrose incipiente. Na vaca que recebeu a maior dose e foi a óbito, bem como em outra intoxicada naturalmente, os achados de necropsia foram similares aos observados nos fetos, exceto pela dilatação dos vasos da base do coração e mais acentuada palidez do miocárdio. Observaram-se ainda edema subcutâneo nas regiões cervical e esternal, bem como veias jugulares ingurgitadas. Os achados histopatológicos foram necrose e edema intersticial com acentuada fibrose no miocárdio, espongiose da substância branca do encéfalo e, no fígado, congestão e leve fibrose. Adicionalmente, observou-se na vaca intoxicada espontaneamente, 17 dias após o aborto, arritmia cardíaca, jugular ingurgitada, edema de peito e barbela, anorexia com morte 43 dias após o aborto. Este estudo demonstra que Tetrapterys acutifolia é capaz de induzir aborto e, dependendo da dose, ainda causar a morte das vacas que abortarem