Host cell death due to enteropathogenic Escherichia coli has features of apoptosis.

Enteropathogenic Escherichia coli (EPEC) is a cause of prolonged watery diarrhea in children in developing countries. The ability of EPEC to kill host cells was investigated in vitro in assays using two human cultured cell lines, HeLa (cervical) and T84 (colonic). EPEC killed epithelial cells as assessed by permeability to the vital dyes trypan blue and propidium iodide. In addition, EPEC triggered changes in the host cell, suggesting apoptosis as the mode of death; such changes included early expression of phosphatidylserine on the host cell surface and internucleosomal cleavage of host cell DNA. Genistein, an inhibitor of tyrosine kinases, and wortmannin, an inhibitor of host phosphatidylinositol 3-kinase, markedly increased EPEC-induced cell death and enhanced the features of apoptosis. EPEC-induced cell death was contact dependent and required adherence of live bacteria to the host cell. A quantitative assay for EPEC-induced cell death was developed by using the propidium iodide uptake method adapted to a fluorescence plate reader. With EPEC, the rate and extent of host cell death were less that what has been reported for Salmonella, Shigella, and Yersinia, three other genera of enteric bacteria known to cause apoptosis. However, rapid apoptosis of the host cell may not favor the pathogenic strategy of EPEC, a mucosa-adhering, noninvasive pathogen.

Development and characterization of monoclonal antibody to T-antigen: (gal beta1-3GalNAc-alpha-O).

The saccharide antigen, Gal beta1-3GalNAc or T antigen, is of biologic importance in many systems. It is a tumor-associated carbohydrate antigen, a temporally expressed antigen in germinal center B cells and cortical T cells, a parasite-associated antigen, a spermatozoa vitality marker and an antigen on aged red blood cells. It may play a role in normal cellular adhesion and in tumor cell metastasis. Well characterized monoclonal antibodies (MAb) to Gal beta1-3GalNAc will be useful for further studies in these areas. We developed an IgG3 MAb to Gal beta1-3GalNAc by immunizing the mice with a synthetic Gal beta1-3GalNAc-BSA conjugate. The MAb was analyzed using inhibition enzyme immunoassays with related synthetically prepared sugars to determine the restrictions involved in the antibody binding. Use of synthetic sugars as competitors enabled us to delineate the epitope restrictions on the binding activity of this monoclonal and will enable use of this MAb in studies concerning the biologic importance of this disaccharide.

Utility of thyroid function screening in adolescent psychiatric inpatients.

OBJECTIVE: Thyroid function abnormalities have been associated with psychiatric symptoms. This study examines the utility of thyroid screening among adolescent psychiatric inpatients. METHOD: A retrospective chart review of 196 first-time admissions to an adolescent psychiatric unit was conducted. Charts were screened for demographics, presence/absence of thyroid function testing, history of thyroid disease, medication/illicit substance use, and other factors of influence on thyroid testing. Thyroid test results were reviewed for abnormalities. RESULTS: Thyroid function testing was conducted in 150 of the 196 admissions. Fifty-two patients had abnormalities, most of which were isolated abnormalities of thyroxine (T4) or triiodothyronine uptake (T3U). Laboratory diagnosis of hyperthyroidism and mild hypothyroidism was met by two and eight patients, respectively; five had profiles that were normal upon subsequent testing 1 week later. None of the patients was symptomatic, and none required thyroid supplementation or antithyroid medications. Gender differences in T4 and T3U were noted, and age was positively correlated with T3U. CONCLUSIONS: Thyroid function tests may be spuriously abnormal in routine screening of newly admitted psychiatric patients. Routine thyroid screening among adolescent psychiatric inpatients is unwarranted except in patients who display physical signs or symptoms suggestive of thyroid disease.