Convergence of neural systems processing stimulus associations and coordinating motor responses

A sensory-sensory learning paradigm was used to measure neural changes in humans during acquisition of an association between an auditory and visual stimulus. Three multivariate partial least-squares (PLS) analyses of positron emission tomography data identified distributed neural systems related to (i) processing the significance of the auditory stimulus, (ii) mediating the acquisition of the behavioral response, and (iii) the spatial overlap between these two systems. The system that processed the significance of the tone engaged primarily right hemisphere regions and included dorsolateral prefrontal cortex, putamen, and inferior parietal and temporal cortices. Activity changes in left occipital cortex were also identified, most likely reflecting the learned expectancy of the upcoming visual event. The system related to behavior was similar to that which coded the significance of the tone, including dorsal occipital cortex. The PLS analysis of the concordance between these two systems showed substantial regional overlap, and included occipital, dorsolateral prefrontal, and limbic cortices. However, activity in dorsomedial prefrontal cortex was strictly related to processing the auditory stimulus and not to behavior. Taken together, the PLS analyses identified a system that contained a sensory-motor component (comprised of occipital, temporal association and sensorimotor cortices) and a medial prefrontallimbic component, that as a group simultaneously embodied the learning-related response to the stimuli and the subsequent change in behavior.      

The role of pararenal collaterals in assessing renal artery stenosis before and after percutaneous transluminal angioplasty

For the past several years, observation of flow direction in non-parenchymal renal artery branches, particularly during pharmacoangiography, has proved to be extremely reliable in the preoperative evaluation of the hemodynamic significance of renal artery stenoses. The advent of percutaneous transluminal angioplasty (PTA) has expanded the applications for these methods. Their value in PTA is demonstrated through five illustrative cases. In four stenoses shown to be significant before PTA, clinical responses were favorable. In one case undergoing PTA of an anatomically severe, but hemodynamically insignificant stenosis, blood pressure was unchanged after PTA. After PTA, observation of orthograde flow in the pararenal arteries confirms the adequacy of the procedure, and predicates a favorable clinical response.     

The mandible in mandibulofacial dysostosis: a cephalometric study

The lower border of the mandible in mandibulofacial dysostosis is characteristic of the syndrome. Evaluation of the cephalograms by means of the medial axis analysis and inflectional tangents captures the shape deformity. Morphometric data from lateral cephalograms on seven patients, ages 3 through 20 years, are reported: a total of 22 observations on three males and four females. These forms were compared to normal mandibular forms from the University of Michigan University School Study. The curvature of the gonial angle in the study population is not distinguishable from the normal curvature. Relative to this apparently normal region, there is a marked downward displacement of the symphysis that results in the curvature typical of the lower mandibular border in this syndrome. These findings are not consistent with earlier reports.     

The inappropriateness of conventional cephalometrics.

1. Cephalometric conventions today may have little basis in either biology or biometrics. 2. There is no theory of cephalometrics, only conventions which involve landmarks and straight lines only. These fail to capture the curving of form and its changes, exclude proper measures of size for bent structures, and misrepresent growth, portraying it as vector displacement rather than a generalized distortion. 3. Conventional cephalometric procedures misinform by fabrication of misleading geometric quantities, by camouflage, particularly of remodeling, by confusion about what is happening (analysis of rotations, treating shape separately from size, and registering angles on landmarks as vertices), and by subtraction as a representation of growth. 4. We suggest that the present systems offer little real hope of improvement sufficient to meet our needs in craniofacial growth research. We call attention to three possible techniques to be included in future cephalometric conventions: (1) tangents and curvatures, (2) Blum's medial axis ("skeleton"), and (3) biorthogonal grids.     

Angiographic aspects of experimental nonocclusive intestinal ischemic injury.

An experiment was designed to fulfill the following aims: (1) to develop a model of nonocclusive intestinal ischemic injury compatible with survival for several days; (2) to determine the accuracy of angiography in diagnosing the presence and extent of intestinal ischemic injury; and (3) to determine the therapeutic and diagnostic value of intraarterial papaverine infusion. Experimental shock models were developed in the dog, and efficacy of the hypovolemic and normovolemic models was confirmed by gross and histologic evidence of intestinal injury in surviving dogs. No reliable angiographic signs of intestinal mucosal injury could be elicited. Angiographic abnormalities associated with the experiment were attributable to the shock itself and disappeared with the relief of shock. Infusion of papaverine into the superior mesenteric artery within 2 hr of the onset of shock prevented or ameliorated intestinal injury.     

Accelerated thrombolysis and angioplasty for hand ischemia in Buerger's disease

A patient with severe hand ischemia due to Buerger's disease was treated by a rapidly effective modification of percutaneous catheterization. Accelerated mechanical and pharmacologic thrombolysis of an occluded palmar arch with 200,000 U urokinase and subsequent small vessel angioplasty abolished pain and restored digital perfusion within 40 min.     

Hyperfunctioning and nonhyperfunctioning benign adrenal cortical lesions: characterization and comparison with MR imaging

The authors evaluated the potential of magnetic resonance (MR) imaging at 0.35 T to permit differentiation of nine hyperfunctioning adrenal cortical lesions from 21 nonhyperfunctioning adrenal cortical adenomas. Both qualitative data (visual assessment) and quantitative data (signal intensity ratios, T1, and T2) were used for tissue characterization. With a 2,000/56-100 sequence (repetition time msec/echo time msec), the majority of lesions were visually isointense to liver. Of 34 quantitative measures, only lesion-liver and lesion-kidney intensity ratios at 2,000/150 showed statistically significant differences among nonhyperfunctioning adenomas, aldosterone-producing lesions, and corticosteroid-producing lesions; however, the authors question the significance of these differences because of the abundant noise associated with the 2,000/150 sequence. The results suggest that nonhyperfunctioning adrenal cortical adenomas cannot be distinguished from benign hyperfunctioning cortical lesions with use of MR imaging at 0.35 T.