Long-term antigen challenge results in progressively diminished mucosal mast cell degranulation in rats

BACKGROUND & AIMS: The effects of short-term antigenic activation of mast cells on the gastrointestinal tract have been well characterized, but little is known about the effects of long-term exposure to antigen on mucosal mast cell reactivity. The aim of this study was to determine the effects of long-term antigen exposure on mucosal mast cell reactivity in the gastrointestinal mucosa. METHODS: Rats sensitized to chicken ovalbumin were orally challenged (short-term or long-term) with antigen. Rat mast cell protease II (RMCP-II) content was measured in serum as an index of mucosal mast cell degranulation. RESULTS: Short- term oral antigen challenge caused a 30-fold increase in serum RMCP-II levels. RMCP-II release was markedly diminished in long term-challenged rats (P < 0.001), despite increased tissue RMCP-II levels in stomach and jejunum. Although short-term antigen challenge significantly increased gastric acid secretion, no such response was observed after the long-term antigen challenge. In rats undergoing long-term challenge, a significant release of RMCP-II in response to intravenous antigen was not observed; however, mucosal mast cells remained responsive to intravenous anti-immunoglobulin E. CONCLUSIONS: Repeated activation of mucosal mast cells results in a progressive diminution of RMCP-II release not attributable to depletion of this mediator. This may represent an adaptive response aimed at minimizing the potentially deleterious effects of repeated exposure to an antigen. (Gastroenterology 1996 Dec;111(6):1516-23)     

Late recovery in cerebral fat embolism

Fat embolism syndrome presenting primarily with cerebral manifestations is rarely reported. We report here two such patients who showed complete recovery following initial deterioration. The aim of these reports is to highlight that prolonged intensive care and good rehabilitation can lead to normal neurologic recovery despite poor clinical picture initially. The importance of adequate oxygenation to prevent secondary brain damage is emphasized during prolonged recovery.     

A carcinogenesis reversibility study of the effects of butylated hydroxyanisole on the forestomach and urinary bladder in male Fischer 344 rats

A reversibility study was initiated to determine if the length of feeding with 2% butylated hydroxyanisole (BHA) altered the incidence of forestomach lesions observed after a 24-month observation period. Groups of male Fischer 344 rats were fed 2% BHA for 0, 3, 6, 12, and 24 months and then the basal diet for the completion of the 24-month experimental period. Subgroups were serially sacrificed for histopathological examination and [methyl-3H]thymidine radioautography at the time when each group of animals was transferred to the basal diet and also at 15 months. The results showed that except for carcinomas and some epithelial downgrowths, cellular proliferation, measured by radioautography in the epithelium lining the greater and the lesser curvature of the forestomach, remained dependent on the continuous presence of 2% BHA for, at least, 12 months. Superficial hyperplasias, inflammatory lesions and many of the papillomas regressed after cessation of treatment at 12 months. The epithelial downgrowths did not appear to enlarge after the BHA was withdrawn. The squamous cell carcinomas occurred in almost identical yields whether the rats were fed 2% BHA for 12 months and then returned to the basal diet for 12 months or received 2% BHA continuously for 24 months. It is shown here that at several times, 2% BHA stimulated the [methyl-3H]thymidine labelling index of the transitional epithelium of the urinary bladder and that at 3 months the no observed effect level was greater than 0.5% BHA. The significance of the studies on the forestomach and bladder epithelia are discussed. It is concluded that the lesions induced by BHA are most unlikely to be relevant to humans exposed to much lower levels of BHA.     

In vivo and in vitro MR imaging of renal tumors: histopathologic correlation and pulse sequence optimization

Magnetic resonance (MR) imaging has given mixed results in the detection of renal masses. To identify the reasons for this and to determine the optimal pulse sequences for evaluating renal tumors, the authors imaged 12 primary renal tumors in vivo and 17 in vitro at 0.35 T. Histopathologic findings for each specimen were closely correlated with the MR images. Four of seven solid tumors imaged in vivo were isointense with surrounding normal renal parenchyma at all pulse sequences. The other three tumors were hyperintense in vivo at T2-weighted sequences. At heavily T2-weighted sequences eight solid tumors were hyperintense in vitro and four were hypointense. There was no correlation between signal intensity and specific tissue type or histologic pattern for solid tumors. The five cystic tumors were well seen both in vivo and in vitro on T2-weighted images. However, the signal intensity of the cyst fluid was an unreliable indicator of benignancy. SE MR imaging at 0.35 T has significant limitations in the detection of solid renal masses.