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A promising method for identifying hemodynamic impairment that may serve as a biomarker for stroke risk in patients with intracranial stenosis is cerebrovascular reactivity (CVR) mapping using noninvasive MRI. Here, abilities to measure CVR safely in the clinic using hypercarbic hyperoxic (carbogen) gas challenges, which increase oxygen delivery to tissue, are investigated.

Changes in cerebral hemodynamics underlie a broad spectrum of ischemic cerebrovascular disorders. An ability to accurately and quantitatively measure hemodynamic (cerebral blood flow and cerebral blood volume) and related metabolic (cerebral metabolic rate of oxygen) parameters is important for understanding healthy brain function and comparative dysfunction in ischemia. Although positron emission tomography, single-photon emission tomography, and gadolinium-MRI approaches are common, more recently MRI approaches that do not require exogenous contrast have been introduced with variable sensitivity for hemodynamic parameters. The ability to obtain hemodynamic measurements with these new approaches is particularly appealing in clinical and research scenarios in which follow-up and longitudinal studies are necessary. The purpose of this review is to outline current state-of-the-art MRI methods for measuring cerebral blood flow, cerebral blood volume, and cerebral metabolic rate of oxygen and provide practical tips to avoid imaging pitfalls. MRI studies of cerebrovascular disease performed without exogenous contrast are synopsized in the context of clinical relevance and methodological strengths and limitations.

ABSTRACTA liquid culture followed by molecular confirmation was evaluated for potential to improve sensitivity and reduce time to diagnosis of Mycobacterium aviumsubsp. paratuberculosisinfection. Fecal samples from 240 animals from Ohio farms were assessed for presence of M. aviumsubsp. paratuberculosisusing four different protocols: (i) sedimentation processing followed by inoculation on Herrold's Egg Yolk media (HEYM) slants (monitored biweekly up to 16 weeks), (ii) double centrifugation processing followed by inoculation on HEYM slants (monitored biweekly up to 16 weeks), (iii) liquid-solid double culture method using modified 7H9 broth (8 weeks) followed by subculture on HEYM slants (monitored up to 8 weeks), and (iv) liquid culture using modified 7H9 broth (8 weeks) followed by molecular assays for the presence of two M. aviumsubsp. paratuberculosis-specific targets. The number of positive samples detected by each protocol was 37, 53, 65, and 76, respectively. Twenty-seven samples were positive by all four methods. Based on samples positive by at least one method (n= 81), the sensitivities for sedimentation processing, double centrifugation processing, liquid-solid double culture, and liquid culture followed by molecular confirmation were 46%, 65%, 80%, and 94%, respectively. Fingerprinting of the positive samples using two polymorphic (G and GGT) short sequence repeat regions identified varying levels of within-farm and between-farm diversity. Our data indicate that liquid culture followed by molecular confirmation can significantly improve sensitivity and reduce time-to-diagnosis (from 16 to 8 weeks) of M. aviumsubsp. paratuberculosisinfection and can also be efficiently employed for the systematic differentiation of M. aviumsubsp. paratuberculosisstrains to understand the epidemiology of Johne's disease.

ABSTRACTAnalysis of short sequence repeats of Mycobacterium aviumsubsp. paratuberculosisisolated from Crohn's disease patients identified two alleles, both of which clustered with strains derived from animals with Johne's disease. Identification of a limited number of genotypes among human strains implies the existence of human disease-associated genotypes and strain sharing with animals.

ABSTRACTMycobacterial isolates were obtained by radiometric culture from 33 different species of captive or free-ranging animals (n= 106) and environmental sources (n= 3) from six geographic zones within the United States. The identities of all 109 isolates were confirmed by using mycobactin J dependence and characterization of five well-defined molecular markers, including two integration loci of IS900(loci L1 and L9), one Mycobacterium aviumsubsp. paratuberculosis(M. paratuberculosis)-specific sequence (locus 251), and one M. aviumsubsp. avium-specific marker (IS1245), as well as hsp65and IS1311restriction endonuclease analyses. Seventy-six acid-fast isolates were identified as M. paratuberculosis, 15 were identified as belonging to the M. avium-M. intracellularecomplex (but not M. paratuberculosis), and the remaining 18 were identified as mycobacteria outside the M. avium-M. intracellularecomplex. Fingerprinting by multiplex PCR for IS900integration loci clustered 67 of the 76 M. paratuberculosisstrains into a single clade (designated clade A18) and had a Simpson's diversity index (D) of 0.53. In contrast, sequence-based characterization of a recently identified M. paratuberculosisshort sequence repeat (SSR) region enabled the differentiation of the M. paratuberculosisisolates in clade A18 into seven distinct alleles (D= 0.75). The analysis revealed eight subtypes among the 33 species of animals, suggesting the interspecies transmission of specific strains. Taken together, the results of our analyses demonstrate that SSR analysis enables the genetic characterization of M. paratuberculosisisolates from different host species and provide evidence for the host specificity of some M. paratuberculosisstrains as well as sharing of strains between wild and domesticated animal species.

ABSTRACTThe objectives of this study were to understand the molecular diversity of animal and human strains of Mycobacterium aviumsubsp. paratuberculosisisolated in the United States and to identify M. aviumsubsp. paratuberculosis-specific diagnostic molecular markers to aid in disease detection, prevention, and control. Multiplex PCR of IS900integration loci (MPIL) and amplified fragment length polymorphism (AFLP) analyses were used to fingerprint M. aviumsubsp. paratuberculosisisolates recovered from animals (n= 203) and patients with Crohn's disease (n= 7) from diverse geographic localities. Six hundred bacterial cultures, including M. aviumsubsp. paratuberculosis(n= 303), non-M. aviumsubsp. paratuberculosismycobacteria (n= 129), and other nonmycobacterial species (n= 168), were analyzed to evaluate the specificity of two IS900integration loci and a newly described M. aviumsubsp. paratuberculosis-specific sequence (locus 251) as potential targets for the diagnosis of M. aviumsubsp. paratuberculosis. MPIL fingerprint analysis revealed that 78% of bovine origin M. aviumsubsp. paratuberculosisisolates clustered together into a major node, whereas isolates from human and ovine sources showed greater genetic diversity. MPIL analysis also showed that the M. aviumsubsp. paratuberculosisisolates from ovine and bovine sources from the same state were more closely associated than were isolates from different geographic regions, suggesting that some of the strains are shared between these ruminant species. AFLP fingerprinting revealed a similar pattern, with most isolates from bovine sources clustering into two major nodes, while those recovered from sheep or humans were clustered on distinct branches. Overall, this study identified a high degree of genetic similarity between M. aviumsubsp. paratuberculosisstrains recovered from cows regardless of geographic origin. Further, the results of our analyses reveal a relatively higher degree of genetic heterogeneity among M. aviumsubsp. paratuberculosisisolates recovered from human and ovine sources.

As cross-sectional imaging with CT and MRI expands, the role and limitations of abdominal plain radiography in the evaluation of bowel obstruction must be re-evaluated. This article reviews the plain radiographic findings of the most frequent causes of bowel obstruction and outlines strategies for further imaging when plain radiographic findings are problematic.