gamma-Aminobutyric acid localization and function as modulator of cholinergic neurotransmission in rat antral mucosal/submucosal fragments.

gamma-Aminobutyric acid, a neurotransmitter in the central nervous system, has been shown to be present in and synthesized and secreted by rodent and feline myenteric plexus neurons. The aims of the present studies were to measure gamma-aminobutyric acid concentrations and synthesis and to establish cellular localization and uptake of gamma-aminobutyric acid by immunocytochemistry and autoradiography, respectively, within mucosal and submucosal tissues of the rat antrum. Direct demonstration of [3H]gamma-aminobutyric acid release and the effects of exogenous gamma-aminobutyric acid and muscimol, a GABA alpha agonist, on [3H]acetylcholine release from antral mucosal/submucosal fragments were examined in perifusion experiments. gamma-Aminobutyric acid content and synthesis, as reflected by glutamic acid decarboxylase activity, were present within antral mucosa at levels two to three times that of the body and muscular layers of both the gastric body and antrum. gamma-Aminobutyric acid was identified immunocytochemically, principally in mucosal epithelial cells of the antrum. Exogenous gamma-aminobutyric acid and muscimol were capable of stimulating acetylcholine release through a GABA alpha receptor-mediated mechanism that was abolished by tetrodotoxin. These results indicate that gamma-aminobutyric acid is present in and taken up by epithelial cells of the gastric antrum and that gamma-aminobutyric acid is capable of being synthesized by antral mucosal/submucosal tissues. Furthermore, these studies suggest that a peripheral gamma-aminobutyric acid mechanism that may modulate cholinergic neurotransmission and endocrine cell function exists within the antrum.

Nuclear morphology and morphometry of B-lymphocyte transformation. Implications for follicular center cell lymphomas.

One of the major tenets of current non-Hodgkin's lymphoma classifications is the relationship of morphologic subtypes to stages in the sequence of normal B-lymphocyte transformation occurring in the germinal follicle. To test this hypothesis, quantitative morphometric image analysis was carried out on in vivo and in vitro samples of mouse splenic lymphocytes in which transformation was induced by bacterial lipopolysaccharide (LPS), a specific B-cell mitogen. The results were compared with a similar analysis of germinal center lymphocyte populations of normal human spleen. In the in vivo mouse model, initial stages of B-cell transformation were detectable as early as 4 hours after LPS injection, and the process was essentially fully developed by 48-72 hours. Quantitative evaluation revealed that the majority of nuclear profiles were nearly spherical or only slightly eccentric and that no major alteration in nuclear contour occurred during any phase of the progressive increase in nuclear size following mitogen-induced lymphocyte transformation. In fact, in this system, B lymphocytes with a nuclear profile cleft of greater than or equal to 0.4 mu accounted for only 3% of the combined unstimulated and LPS-activated population assessed (N = 9936). This compared with normal human spleen, in which 16% of germinal center lymphocyte populations had similarly cleft nuclear profiles. Sequential alterations in the organization of condensed chromatin occurred concomitant with gradual nuclear enlargement during mitogen-induced mouse spleen lymphocyte transformation. A comparative morphologic and morphometric assessment of nuclear profiles of lymphocyte populations in germinal centers of normal human spleen provides indirect evidence for a similar pattern of nuclear alterations in human B lymphocytes. Autoradiographic data obtained from LPS-activated mouse splenic lymphocytes indicate that nuclear morphologic aspects of the transformation process can occur entirely within the G1 phase of the cell cycle. The results of this study suggest that subtypes of non-Hodgkin's lymphoma largely composed of neoplastic lymphocytes with extensively convoluted or cleft nuclei do not reflect a morphologic stage in the transformation of normal lymphocytes. In addition, the heterogeneous nuclear forms of follicular center cell lymphocytes would appear to result from parallel transformation processes involving cleaved and noncleaved nucleated lymphocytes and not the sequential pathway proposed by Lukes and Collins.

Three-dimensional kinematics of the taped ankle before and after exercise.

The practice of prophylactic ankle taping or wrapping to reduce the incidence of inversion ankle sprains in athletes has come under attack. The purpose of this study was to measure objectively one ankle taping technique's ability to withstand the stresses placed upon it by a standardized exercise routine. Electrogoniometers were used to measure the three-dimensional ankle motion of 20 subjects walking on a level surface and a 10 degrees sideslope. The evaluations were carried out under these three conditions: (1) both ankles untaped, (2) both ankles taped before exercises, and (3) both ankles taped after exercise. The results from this study indicate that the tape does indeed restrict those motions associated with inversion ankle sprain. Methods similar to those described in this study could be used in the evaluation of many current training room practices and thereby provide an objective rationale for their application.