Stereotypes concerning normal and handicapped children.

Individuals' attitudes were assessed toward various groups of children. In study 1 the respondents were 65 male and female teachers from across the state of Kansas. In study 2 the respondents were 89 men and women in attendance at the 1978 International Conference of the Association for Children with Learning Disabilities. In both studies the evaluations of the labels "gifted children," "normal children," and "physically handicapped children" were found to be significantly more positive than the evaluations of the labels "mentally retarded children," "learning disabled children," and "emotionally disturbed children." These results seem to indicate that definite negative stereotypes are held toward the latter three groups of children. In study 1 these findings were found to occur generally regardless of the respondents' sex, age, educational level attained, and amount of previous mainstreaming experience.

Mast cell heterogeneity in man. I. Histologic studies of the intestine.

We have studied the distribution and abundance of histochemically distinct mast cell subpopulations in the normal small and large intestine of man. One subpopulation has histochemical properties similar to the functionally distinct intestinal mucosal mast cell (MMC) of the rat and the other has properties similar to the widely distributed mast cell found in connective tissues and the peritoneal cavity of many animals. Both subpopulations are present in intestinal epithelium, lamina propria, submucosa and muscularis mucosa, and muscle. However, the subpopulation histochemically similar to the rodent MMC is significantly more abundant than the other in all sites in the large intestine and also in the lamina propria and muscle of the small intestine. It is important to determine whether these histochemically distinct mast cell subpopulations in man differ in their responses to various secretagogues and antiallergic compounds as in the rat.

Mast cells from the human intestinal lamina propria. Isolation, histochemical subtypes, and functional characterization.

With the use of a collagenase dispersion technique, cells were isolated from the lamina propria of the human small and large intestine. The cell suspensions contained 8% mast cells, which on average contained 1 to 2 pg of histamine/cell. With the use of histochemical procedures based upon fixative sensitivity and dye binding, which identify functionally distinct mast cell subtypes in the rat, dispersed human intestinal mast cells contained approximately equal proportions of two histochemical subtypes analogous to those in the rat. Whether these are functionally distinct as in the rat remains to be determined. The histochemically mixed mast cell populations from the human intestinal mucosa secreted histamine in a dose- and energy-dependent manner in response to anti-IgE and A23187, but not 48/80. Theophylline, doxantrazole, quercetin, and salbutamol all significantly inhibited anti-IgE-induced histamine secretion by human intestinal mast cells, but cromolyn sodium and the experimental antisecretory drugs, nedocromil sodium and FPL 52694, did not inhibit histamine secretion by the mast cell mixture to a statistically significant extent. Cromolyn sodium inhibited histamine secretion by 15 to 30%, and whether this reflected inhibition of one of the two histochemical mast cell subtypes to a greater extent than the other or all the cells to a minimal degree remains to be established. Control investigations of the intestinal cell isolation procedure indicated that these qualities did not reflect effects of the cell dispersal procedure. Further characterization and analysis of intestinal mast cells is essential to determine if functionally distinct mast cell subtypes exist in human tissues.

Role of nonspecific cytotoxic cells in intestinal epithelial cell injury in Nippostrongylus brasiliensis infection.

We have employed a cultured crypt-like intestinal epithelial rat cell line (IEC-18) to assess whether killing by nonspecific cytotoxic cells contributes to epithelial cell destruction in Nippostrongylus brasiliensis (N.b.) infection. Spleen cells from N.b.-infected Sprague-Dawley rats, 11-13 days postinfection when villus atrophy and crypt hyperplasia were evident, killed IEC-18 in a 4-hr 51Cr-release assay. In contrast, intraepithelial leukocytes (IEL) from N.b.-infected rats showed decreased killing of IEC-18 compared to controls in a 16-hr assay. Spleen NK activity was increased in N.b.-infected rats whereas IEL NK activity was decreased. We conclude that direct cytotoxicity of crypt-like intestinal epithelial cells by nonspecific cytotoxic cells appears to play no significant role in intestinal injury in N.b. infection.

Human lung mast cells: distribution and abundance of histochemically distinct subpopulations.

Methods originally employed to demonstrate the heterogeneity of mast cells in the rat and more recently in the human intestine were used to study mast cell heterogeneity in the human bronchial mucosa and lung parenchyma. Thus, a quantitative survey of pulmonary mast cells using different fixation and staining procedures indicated that two distinct mast cell subpopulations (formalin-sensitive and formalin-resistant) are present and have distinct patterns of distribution and abundance. The findings are of potential clinical importance because histochemical heterogeneity may be a marker of functional mast cell differences in humans including differences in responsiveness to antiallergic drugs, as occurs in rats. The findings also indicate that conventional methods of fixation are likely to lead to a gross underestimation of total mast cell numbers.