Comparative toxicity of ethylene dichloride in F344/N, Sprague-Dawley and Osborne-Mendel rats

Studies were conducted to compare the toxicity of ethylene dichloride (EDC) in F344/N rats, Sprague-Dawley rats, and Osborne-Mendel rats. Ten rats/sex/group were exposed to EDC in drinking-water at 0, 500, 1000, 2000, 4000 and 8000 ppm for 13 wk. The highest concentration was limited by the maximum solubility of EDC in water (about 9000 ppm). In addition, F344/N rats (10/sex/group) were administered EDC in corn oil by gavage to compare toxicity resulting from bolus administration with that of continuous exposure in drinking-water. Gavage doses of EDC were within the range of total daily doses (in mg/kg body weight/day) resulting from exposure in drinking-water. EDC administered by gavage resulted in greater toxicity to F344/N rats than did administration of similar doses in drinking-water. All males receiving 240 and 480 mg/kg body weight and 9/10 females receiving 300 mg/kg body weight by gavage died before the end of the study. Necrosis of the cerebellum was observed in the brains of 3 males receiving 240 mg/kg body weight and 3 females receiving 300 mg/kg body weight. Hyperplasia and inflammation of the forestomach mucosa were observed in 8 male and 3 female rats that died or were killed in moribund condition. EDC caused minimal toxicity to F344/N, Sprague-Dawley and Osborne-Mendel rats at the drinking-water concentrations used in these studies; only female F344/N rats had EDC-related renal lesions. Based on mortality and EDC-related lesions, the no-effect levels for EDC administered by gavage to F344/N rats were 120 mg/kg body weight for males and 150 mg/kg body weight for females.     

Long-term effects of Terminalia chebula Retz. on hyperglycemia and associated hyperlipidemia, tissue glycogen content and in vitro release of insulin in streptozotocin induced diabetic rats.

The aqueous extract of the fruits of Terminalia chebula Retz. has been evaluated for its antidiabetic activity in streptozotocin (STZ) induced mild diabetic rats and compared with a known drug, tolbutamide. The oral effective dose (ED) of the extract was observed to be 200 mg/kg body weight, which produced a fall of 55.6% (p<0.01) in the oral glucose tolerance test. Oral administration of ED of aqueous extract of T.chebula (AETC) daily once for two months reduced the elevated blood glucose by 43.2% (p<0.01) and significantly reduced the increase in glycosylated hemoglobin (HbA1c) (p<0.01). The same dose also showed a marked improvement in controlling the elevated blood lipids as well as decreased serum insulin levels in contrast to the untreated diabetic animals. Hepatic and skeletal muscle glycogen content decreased by 75% and 62.9% respectively in diabetic controls, these alterations were partly prevented (34.9% and 21.17%) in AETC treated group when compared to the healthy controls. The in vitro studies with pancreatic islets showed that the insulin release was nearly two times more than that in untreated diabetic animals. The treatment did not have any unfavorable effect on other blood parameters of liver and kidney function tests. LD 50 was found to be above 3 g/kg bw i.e. 15 times of ED, because there were no deaths of animals even at this dose indicating high margin of safety. These findings suggest further investigations for the possible use of the aqueous extract of fruits of T.chebula for the treatment of diabetes.     

Management of tuberculosis of the spine with neurological complications.

Tuberculosis is still a major cause of spinal compression in the developing countries. In this study 200 patients presenting with neurological lesions secondary to tuberculosis of the spine have been classified according to the Frankel classification and the results evaluated. A combination of surgical decompression and chemotherapy is advocated. The dangers of non-operative treatment are discussed.     

Coexistence of contractile and relaxant 5-hydroxytryptamine receptors coupled to distinct signaling pathways in intestinal muscle cells: convergence of the pathways on Ca2+ mobilization.

Muscle cells were dispersed separately from circular and longitudinal muscle layers of guinea pig intestine, and 5-hydroxytryptamine (5-HT) receptors were characterized in naive cells and in cells in which one receptor type was preserved by selective receptor protection. In naive cells from both regions, 5-HT caused contraction and stimulated increases in cytosolic free calcium concentration ([Ca2+]i) (3-fold; p < 0.01) and cAMP levels (40-60%; p < 0.01) that were inhibited, respectively, by the 5-HT2 antagonist ketanserin and the 5-HT1p antagonist N-acetyl-5-hydroxytryptophyl 5-hydroxytryptophan amide (5-HTP-DP). In circular muscle cells, where agonist-induced increase in [Ca2+]i is mediated by Ca2+ release from inositol (1,4,5)trisphosphate-sensitive stores, 5-HT caused an increase in inositol (1,4,5)trisphosphate levels that was inhibited by ketanserin. In cells maximally contracted with a non-5-HT agonist (cholecystokinin octapeptide), 5-HT caused relaxation when the contractile effect mediated by 5-HT2 receptors was blocked with ketanserin; relaxation and the concomitant increase in cAMP were inhibited by 5-HTP-DP. The singular contributions of the Ca2+ and cAMP signaling pathways were identified in cells where only one receptor type was preserved. In cells with only 5-HT2 receptors, 5-HT caused contraction and an increase in [Ca2+]i but not in cAMP levels; contraction and the increase in [Ca2+]i were inhibited by ketanserin. Conversely, in cells with only 5-HT1p receptors, 5-HT caused relaxation and an increase in cAMP levels but not in [Ca2+]i; relaxation and the increase in cAMP levels were inhibited by 5-HTP-DP. The two signaling pathways were functionally linked, converging to regulate the level of [Ca2+]i. Thus, the increase in [Ca2+]i was augmented 1) when cAMP production was inhibited by 5-HTP-DP in naive cells or 2) when cAMP production was suppressed in cells where 5-HT1p receptors were inactivated and only 5-HT2 receptors were preserved. The results imply that the increase in cAMP levels mediated by 5-HT1p receptors acted to attenuate the increase in [Ca2+]i mediated by 5-HT2 receptors. We conclude that the response to 5-HT in muscle cells is a compound effect involving activation of two receptor types coupled to distinct signaling pathways that converge on [Ca2+]i as the determinant of mechanical activity.     

Airway obstruction after extubation following use of transesophageal echocardiography for posterior fossa surgery in the sitting position.

We report respiratory obstruction following surgery in the sitting position with tracheal intubation and placement of a transesophageal echocardiography probe. Obstruction was due to pharyngeal oedema, which resolved with 24 hours. The mechanisms of this complication are discussed.     

Tacrolimus metabolite cross-reactivity in different tacrolimus assays

Objectives: Tacrolimus (FK506) is an immunosuppressive drug with great clinical promise. There is a controversy regarding the role of tacrolimus metabolites in immunosuppression and toxicity, and immunoassays and immunophilin binding assays have not been adequately tested for metabolite cross-reactivity. Methods are limited to HPLC and HPLC-MS for quantifying the parent drug. Mixed lymphocyte culture assay (MLC) is the preferred functional bioassay for the measurement of parent drug and active metabolites but it is not practical for routine laboratory use. Due to differences in assay methods and reagent specificity, the concentration of tacrolimus in a given specimen may vary among different assay kit manufacturers. The objective of this study was to evaluate the degree of cross-reactivity or interference of the three first-generation tacrolimus metabolites [13-O-demethyl (M-I), 31-O-demethyl (M-II) and 15-O-demethyl (M-III)] among two different tacrolimus immunoassays (Immunoassay: PRO-Trac II FK506, Abbott IMx tacrolimus-II); and the radioreceptor assays (RRA) using minor immunophilins (14, 37, and 52 kDa immunophilins) and tacrolimus binding protein (FKBP12).

Methods: First-generation tacrolimus metabolites (M-I, M-II, and M-III) spiked in drug-free whole blood were assayed with RRA using three minor immunophilins (14, 37, and 52 kDa) and two commercial immunoassay procedures (Incstar PRO-Trac II tacrolimus, Abbott IMx tacrolimus II). The results were compared to previously published FKBP-12 RRA data and their immunosuppressive potency.

Results and conclusion: The first generation tacrolimus metabolites (M-I, M-II, and M-III) were tested using concentrations of 10 and 20 ng/mL. The significance of the metabolite interference (% of the total interference) was calculated based on the relative concentration of each metabolite present at steady-state trough concentrations in renal transplant recipients [22]. Metabolite I, which has no functional immunosuppressive activity showed minimal interference compared to M-II and M-III in all assays except the 14 kDa RRA. The Incstar PRO-Trac II tacrolimus assay showed the least M-I interference. Metabolite-II, which has a pharmacologic potency similar to the parent drug, showed a significant interference in the immunoassays and significant interference in radioreceptor assays. Metabolite III, which is pharmacologically inactive, produces 3–10% interference in the different assays if its presence in the blood is 6% of the parent drug. The total interference from these three metabolites was greater in the immunoassays than in the receptor assays. Receptor assays for tacrolimus provide results closer to the target value than do immunoassays.     

Acute inflammatory demyelinating polyradiculoneuropathy following varicella

Four cases of acute inflammatory demyelinating polyradiculoneuropathy following varicella are described. The role of immunosuppression as a contributing factor in triggering an autoimmune disease of the peripheral nervous system following viral infection is discussed.