Regional myocardial oxygen tension: 19F MRI of sequestered perfluorocarbon

A novel noninvasive method of measuring local myocardial oxygen tension (pO₂) In the perfused rat heart using ¹⁹F MRI is demonstrated. Tissue pO₂ was determined on the basis of the ¹⁹F spin-lattice relaxation rate (R1) of perflubron (perfluorooctyl bromide) sequestered in the heart after IV infusion of an emulsion. Spectroscopic measurement of R1 was previously used to measure a global weighted average of oxygen status. ¹⁹F MRI now provides 3D spatial resolution indicating local cardiac pO₂ under normally perfused, globally ischemic, and regionally ischemic conditions.     

Retroperitoneal soft-tissue sarcoma: analysis of 500 patients treated and followed at a single institution.

OBJECTIVE: To analyze treatment and survival of a large cohort of patients with retroperitoneal soft-tissue sarcomas (STS) treated and prospectively followed at a single institution. SUMMARY BACKGROUND DATA: Retroperitoneal STS are relatively uncommon and constitute a difficult management problem. Although surgical resection is often difficult or impossible, current chemotherapy is not effective and radiation is limited by toxicity to adjacent structures. Thus, complete surgical resection remains the most effective modality for selected primary and recurrent disease. METHODS: Five hundred patients with retroperitoneal STS were admitted and treated between July 1, 1982, and September 30, 1997, and prospectively followed. Patient, tumor, and treatment variables were analyzed for disease-specific and disease-free survival. Survival was determined with the Kaplan-Meier method. Statistical significance was evaluated using the logrank test for univariate influence and Cox model stepwise regression for multivariate influence. RESULTS: Two hundred seventy-eight patients (56%) had primary disease and 222 (44%) recurrent disease. Median follow-up was 28 months (range 1 to 172 months), 40 months for survivors. Median survival was 72 months for patients with primary disease, 28 months for those with local recurrence, and 10 months for those with metastasis. For patients with primary or locally recurrent tumors, unresectable disease, incomplete resection, and high-grade tumors significantly reduced survival time. CONCLUSIONS: In this study of patients with retroperitoneal STS, stage at presentation, high histologic grade, unresectable primary tumor, and positive gross margin are strongly associated with the tumor mortality rate. Patients approached with curative intent should undergo aggressive attempts at complete surgical resection. Incomplete resection should be undertaken only for symptom relief.     

Automated quantification of thyrotropin by radial partition immunoassay

We describe a radial partition enzyme immunoassay in which fully automated quantification of human thyrotropin (hTSH) takes less than 11 min. This "sandwich"-type assay involves two monoclonal antibodies, both specific for the intact hTSH molecule. The solid phase consists of tabs of glass-fiber filter paper containing a pre-immobilized monoclonal anti-hTSH antibody complexed with a goat antibody specific for the Fc region of mouse IgG. The patient's sample is first applied to the central "reaction zone" of the tab, wherein hTSH binds to the immobilized antibody. Application of a buffered solution containing enzyme-labeled Fab' fragments of the second monoclonal anti-hTSH antibody initiates "sandwich" formation. A wash buffer containing a fluorogenic substrate elutes unbound conjugate to the tab periphery. The bound enzyme conjugate is quantified by measuring the rate of increase in fluorescence in the reaction zone of the tab, then converting the rate to clinical units by comparison with a stored calibration curve. The clinical utility and performance of the present assay compare favorably with those of other sensitive assays for hTSH.     

Cytology and neuron-glial apposition of migrating cerebellar granule cells in vitro

In developing mammalian brain, many neurons migrate to their final position by moving in direct apposition to radially oriented glial cells. Glial-guided migration can be visualized in microcultures of mouse cerebellar cells by the combined use of cellular antigen markers and high resolution time-lapse video microscopy (Hatten et al., 1984; Edmondson and Hatten, 1987). Such studies have demonstrated the behavior of migrating cells and revealed a motile leading process on the migrating neuron that resembles an axonal growth cone and grows along extended glial fibers. To study the fine structural details of the migrating neuron and its neuron-glial apposition, we identified and monitored neurons in microcultures with video microscopy and examined the cytology and cellular contacts of the same cells with transmission electron microscopy. The cytology of the soma and leading process of migrating cells closely matches that described for granule cells in intact brain (Rakic, 1971). Newly observed structures include the presence of longitudinally oriented microtubules extending from a basal body in the soma into the leading process, and microfilament-rich filopodia arising from the soma and leading process. The most striking feature of actively migrating neurons is a specialized junction between the neuronal cell soma and apposing glial fibers. At this junction, here termed "interstitial density," the extracellular space is dilated to 20 nm and filamentous material in the intracellular cleft either spans the cleft or runs parallel to the cell membranes. Some interstitial fibrils are contiguous with, or are transmembranous extensions of, submembranous cytoskeletal elements that attach to microtubules. Interstitial junctions were not found between neurons that did not translocate in the observation period before fixation. Instead, stationary cells formed desmosomes (puncta and macula adhaerentia) at appositions with glial processes.     

Superior mesenteric artery is more important than inferior mesenteric artery in maintaining colonic mucosal perfusion and integrity in rats

Mucosal hemodynamics (by reflectance spectrophotometry) and mucosal damage (by histologic examination) following acute colonic ischemia were evaluated in different anatomic locations in the colon of anesthetized rats. The reflectance spectrophotometer provides an index of mucosal hemoglobin concentration (IHB) and an index of oxygen saturation of hemoglobin (ISO₂). The patterns of ischemia without congestion (IHB, ISO₂) during superior mesenteric artery occlusion, and ischemia with congestion (IHB, ISO₂) during portal vein occlusion, previously demonstrated in the stomach and duodenum, are also applicable to the colon. The significant linear correlations between changes (as percent of baseline) in IHB, ISO₂, and hydrogen gas clearance suggest that changes in these indices are adequate indicators of changes in colonic mucosal perfusion. Superior mesenteric artery ligation produced significant reductions in both indices, and an increase in damage in the mucosa of the cecum, transverse colon, splenic flexure, and left colon, but not the rectum. Inferior mesenteric artery ligation produced only slight reduction in these indices and minimal damage only in the mucosa of the splenic flexure. These results support the hypothesis that the superior mesenteric artery is more important than the inferior mesenteric artery in maintaining colonic perfusion and colonic mucosal integrity in the rat.Supported by the American Society for Gastrointestinal Endoscopy Career Development Award (H850208, H870212), Veterans Administration Medical Research Funds; and in part by research grants (0162-01, 0162-02; 0291-01) from the Smokeless Tobacco Research Council, Inc.; and by funds provided by the Cigarette and Tobacco Surtax Fund of the State of California through the Tobacco Related Disease Research Program of the University of California.     

Cerebellar target neurons provide a stop signal for afferent neurite extension in vitro.

The contributions of cell-cell interactions to the establishment of specific patterns of innervation within target brain regions are not known. To provide an experimental analysis of the regulation of afferent axonal growth, we have developed an in vitro assay system, based on the developing mouse cerebellum, in which afferent axons from a brainstem source of mossy fiber afferents, the basilar pontine nuclei, were cocultured with astroglia or granule neurons purified from the cerebellum. In the absence of cells from the cerebellum, pontine explants produced axons that fasciculated and extended rapidly on a culture surface treated with poly-lysine or laminin. When pontine neurites grew onto cerebellar astroglial cells, outgrowth was more abundant than on substrates alone, suggesting that glial cells provide a positive signal for axon extension. Time-lapse video microscopy indicated that the rate of neurite extension increased from less than 50 microns/hr to more than 100 microns/hr when axonal growth cones moved from the culture substratum onto an astroglial-cell surface. Acceleration of neurite extension was also observed as pontine neurites grew onto other pontine neurites. By contrast, when pontine neurites grew on granule neurons, the appropriate targets of mossy fibers, the length of pontine neurites was greatly reduced. As growing axons terminated on granule neurons, the target cells appeared to provide a "stop-growing signal" for axon extension. The length of pontine neurites decreased with increasing granule neuron density. Two lines of evidence suggested that the stop signal was contact mediated. First, video microscopy showed that pontine growth cones stopped extending after contacting a granule neuron. Second, the length of afferent axons was not reduced when pontine neurites grew at a distance from granule neurons. Competition experiments where both astroglia and granule neurons were plated together suggested that the growth arrest signal provided by granule neurons could override the growth-promoting signal provided by astroglial cells. These results suggest that specific cell-cell interactions regulate the growth of pontine afferent axons within their cerebellar target, with axoaxonal and axoglial interactions promoting axon extension and axon-target cell interactions interrupting axon extension.     

Nonlinear muscle recruitment during intramuscular and nerve stimulation

Future progress in neuromuscular prostheses will depend on developing techniques for stimulating paralyzed muscle, especially utilizing neuromuscular stimulation. We have found nonlinear force versus stimulus amplitude characteristic (recruitment) curves in the gastrocnemius-soleus-plantaris muscle group of the cat in response to stimulation of the tibial nerve near the muscle entry point. Such response characteristics are undesirable in neuromuscular control systems. Nonlinear recruitment curves usually consisted of two regions in which force increased linearly with stimulus amplitude, separated by a "plateau" region in which force was relatively constant. The two linear regions were associated with activation of separate neuromuscular compartments (lateral or medial gastrocnemius, plantaris, soleus, or subdivisions of those muscles). When the stimulated myoelectric responses from these compartments were plotted versus stimulus amplitude, the region of recruitment between threshold and saturation often did not appreciably overlap for different compartments, suggesting that the axons innervating those compartments were physically segregated within the nerve from axons innervating other compartments. Correlation coefficients between force and stimulated myoelectric response were very high (up to R2 = 0.99) when using a composite curve produced by averaging myoelectric response curves recorded from each of the active compartments. By dividing the tibial nerve into its component bundles or fascicles and stimulating each in turn, it was possible to show that individual bundles innervate non-overlapping groups of muscle compartments, and that recruitment of the nerve bundles over different threshold ranges could account for the nonlinear force/stimulus response curves initially observed. The presence of separate innervation of muscles or compartments by fascicles should be an important factor in designing functional neuromuscular stimulation (FNS) systems.     

Sensory recovery in transplanted toes

This study reports the results of 30 patients who entered a program of sensory reeducation following toe-to-thumb transfer. Results were analyzed after subdividing the patients into those whose injury had produced severe scarring (fibrotic group, N = 15) and those with clean, more distal amputations (non-fibrotic group, N = 15). Patients who were unable to complete sensory reeducation were considered as "drop-out" controls. Although the follow-up time was less than 1 year, the group receiving sensory reeducation did improve to a greater degree and more quickly than the controls, with the level of two-point discrimination recovered being better than that originally present in the toe.     

Serodiagnosis of Trichomonas vaginalis infection by the indirect fluorescent antibody test.

The indirect fluorescent antibody test was used to detect antibodies to Trichomonas vaginalis in 200 antenatal patients. A total of 104 (52%) gave a positive reaction with antigen prepared from cultures of trichomonas isolated from seven of the patients. Antitrichomonal antibody was detected at a 1/4 dilution in 90% of patients with proven trichomoniasis, while the highest dilution at which antibody was detected was 1/32. IgG rather than IgM appeared to be the antibody class involved. Of those patients with no demonstrable trichomonal infection, 17% gave positive reactions at 1/4 dilution, while 64% had no demonstrable antibody. One of 30 children under 11 years of age gave a positive reaction.