Virtual real-time digital processing of hemodynamic data

At present, the majority of cardiac catheterization laboratories acquire and store hemo-dynamic data in analog form. To examine the possibility of performing complex analysis of digital data during the catheterization procedure, we examined whether virtual realtime digital (fast Fourier) analysis improves the accuracy of clinical data. We compared digital filtering of fluid manometry during right heart catheterization with 10-Hz and 250-Hz analog filters. Using the simultaneously acquired micromanometry as the “gold standard,” we found that analog filtering is associated with a greater error and time delay than digital filtering. This study demonstrates that digital hemodynamic data analysis performed during cardiac catheterization can improve the quality of data obtained during right heart catheterization, with the results available within seconds. More extensive use of computers in the cardiac catheterization laboratory may be useful for both clinical and research purposes. © 1992 Wiley-Liss, Inc.     

Bremsstrahlung imaging using the gamma camera: factors affecting attenuation.

Quantitative imaging of bremsstrahlung from pure beta emitters is proposed as a means for in vivo management of antibody therapy. The method involves the use of high-energy collimation, an empirically selected broad photon energy window to enhance detector sensitivity, and a Wiener restoration filter to compensate for system blur. The measured and filtered data were obtained for an idealized scattering medium and isolated spherical sources. An effective linear attenuation coefficient of about 0.13 cm-1 was determined from the raw image data of 32P. A coefficient of 0.14 cm-1 was determined after the images were restored using the Wiener filter. The measured attenuation was not significantly dependent on the size of the region of interest or the size of the source. Its variation was within the experimental error of measurement (+/- 5%). The measured sensitivity (6 x 10(-6) cps/Bq) was sufficient for imaging therapy doses of 32P or 90Y.     

Differential modulation of Purkinje cell activity by enkephalin and corticotropin releasing factor.

Several peptides have been localized within afferents to the opossum's cerebellum, including cholecystokinin (15), enkephalin (16, 17) and corticotropin releasing factor (7, 9). Each of these peptides has a heterogeneous laminar and lobular distribution. Two peptide, enkephalin (ENK) and corticotropin releasing factor (CRF) are present in specific populations of climbing fibers and mossy fibers, which have an overlapping distribution in several areas of the cerebellum, in particular the lateral aspect of vermal lobules VII and VIII. Within this location ENK and CRF are co-localized in individual climbing fibers and mossy fibers (7). In the present study, the physiological effects of these peptides on Purkinje cell activity were analyzed. The data indicate that ENK and CRF have opposite effects on Purkinje cell activity. ENK suppresses spontaneous activity as well as that induced by application of glutamate and aspartate, as described previously (5). In contrast, CRF enhances both spontaneous and amino acid-induced unit activity. Further, when applied simultaneously, CRF blocks the suppressive effect induced by ENK. Previous studies have shown that climbing fibers, as well as the mossy fiber-parallel fiber pathway, are excitatory to Purkinje cells (11). However, immunohistochemical data have shown that these afferents are heterogeneous with respect to their chemical content (7-9, 15-17, 25). As found in the current and previous studies (3, 5) peptides in climbing and mossy fibers modulate the responsiveness of Purkinje cells to primary excitatory neurotransmitters in selected areas of the cerebellar cortex. However, the firing rate of individual Purkinje cells is differentially altered depending on which neurochemical messenger(s) are released.(ABSTRACT TRUNCATED AT 250 WORDS)     

Association and linkage with quantitative traits

This paper examines two approaches for the analysis of quantitative traits: (1) association studies and (2) linkage studies. The trait studied was Q1 from simulated Problem 2 data set in Genetic Analysis Workshop 9. Our purpose was to evaluate associations present in the data, to identify nongenetic and genetic predictors of the trait, and to explore the simulated genome for linkage. Through the association study, we found evidence for the primary major gene associated with this trait. The linkage study found evidence of residual genetic effect acting through other traits. Adjustments of Q1 for Q2 and Q3 led to a failure to find significant effects of MG2 and MG3. This supports the suggestion that adjustment for genetically influenced traits for effects of other genetic traits can reduce the power to detect major gene effects. In summary, we detected the major gene directly associated with the trait of interest through association studies. Linkage analysis detected evidence for two other genes associated to a lesser degree with the trait. © 1995 Wiley-Liss, Inc.     

Biocompatibility studies of the Anaconda stent-graft and observations of nitinol corrosion resistance.

PURPOSE: To validate the deployment, in vivo performance, biostability, and healing capacity of the Anaconda self-expanding endoprosthesis in a canine aortic aneurysm model. METHODS: Aneurysms were surgically created in 12 dogs by sewing a woven polyester patch onto the anterior side of the thoracic or abdominal aorta. Anaconda prostheses were implanted transfemorally for prescheduled periods (1 or 3 months). Aneurysm exclusion and stent-graft patency were monitored angiographically. Healing was assessed with histological analysis and scanning electron microscopy (SEM). Textile analysis determined the physical and chemical stability of the woven polyester material, while the biostability of the nitinol wires was evaluated with SEM and spectroscopy. RESULTS: All prostheses were intact at explantation. After 1 month, endothelial-like cells were migrating in a discontinuous manner both proximally and distally over the internal collagenous pannus at the device-host boundary. After 3 months, endothelialization had reached the midsections of the devices, with a thicker collagenous internal capsule. Patches of endothelial-like cells were sharing the luminal surface with thrombotic deposits. However, the wall of the device at the level of the aneurysm was generally poorly healed, with multiple thrombi scattered irregularly over the luminal surface. The polyester fabric was intact except for some filaments that were ruptured adjacent to the sutures and some abrasion caused by the nitinol wires. No evidence of corrosion was found on the nitinol stents. CONCLUSIONS: This Anaconda stent-graft has demonstrated its ability to exclude arterial aneurysms. The device used in this study was an experimental prototype, and the manufacturer has incorporated new immobilization features into the model for clinical use. The constituent materials appear to be suitable in terms of biocompatibility, biofunctionality, and short-term durability.