In the present study, we compare the capacity of two different embryonic stem (ES) cell lines to secrete neurotrophins in response to cerebral tissue extract derived from healthy or injured rat brains. The intrinsic capacity of the embryonic cell lines BAC7 (feeder cell-dependent cultivation) to release brain-derived neurotrophic factor (BDNF) or neurotrophin-3 (NT-3) exceeded the release of these factors by CGR8 cells (feeder cell-free growth) by factors of 10 and 4, respectively. Nerve growth factor (NGF) was secreted only by BAC7 cells. Conditioning of cell lines with cerebral tissue extract derived from healthy or fluid percussion-injured rat brains resulted in a significant time-dependent increase in BDNF release in both cell lines. The increase in BDNF release by BAC7 cells was more pronounced when cells were incubated with brain extract derived from injured brain. However, differences in neurotrophin release associated with the origin of brain extract were at no time statistically significant. Neutrophin-3 and NGF release was inhibited when cell lines were exposed to cerebral tissue extract. The magnitude of the response to cerebral tissue extract was dependent on the intrinsic capacity of the cell lines to release neurotrophins. Our results clearly demonstrate significant variations in the intrinsic capability of different stem cell lines to produce neurotrophic factors. Furthermore, a significant modulation of neurotrophic factor release was observed following conditioning of cell lines with tissue extract derived from rat brains. A significant modulation of neurotrophin release dependent on the source of cerebral tissue extract used was not observed.

We conclude that the antibodies generated against the extra-cellular domain of the H2 receptor are specific and can be utilized to detect and quantify H2 receptor expression. Furthermore, the significant differences in H2 receptor expression in different vascular cell types might play a critical role in defining histamine induced cellular responses during physiological or pathophysiological processes.

We have suggested previously that the histamine-diamine oxidase system is involved in cell proliferation. Therefore, the diamine oxidase activity and the histamine content were studied during mucosal proliferation induced by 70% resection of the small intestine of the rat with and without aminoguanidine (AG), a specific inhibitor of diamine oxidase (DAO). The DAO activity underwent a marked alteration during the period of mucosal proliferation, probably as an expression of an antiproliferative regulation mechanism. The histamine content decreased in the proliferating mucosa. No influence of AG on mucosal proliferation could be found, which might be due to a compensatory activity of the interconversion pathway.

The image of alpha2-macroglobulin is based on a paradigm evolved in the 1970s. During this decade alpha2-macroglobulin was shown to irreversibly entrap and thereby inhibit a maximum of two proteases. Additional binding of nonproteolytic proteins, i.e., inflammatory mediators and growth factors, is dependent on the conformational status of alpha2-macroglobulin. It was our aim to clarify whether the interaction of nonproteolytic proteins with alpha2-macroglobulin during inflammatory conditions might also modulate the capacity of alpha2-macroglobulin to inhibit proteases. To explore this possibility, bromelain, an exogenous protease, was titrated against plasma of critically ill or septic patients, whose pathophysiological conditions are defined by a massive release of inflammatory mediators. The stoichiometry of bromelain inhibition by alpha2-macroglobulin was quantified by caseolytic activity assays. The maximal alpha2-macroglobulin/bromelain inhibition ratios were significantly increased (1:6 and 1:8 in the two patient groups, P < 0.01) as compared with control groups (1:2 with purified alpha2-macroglobulin and 1:4 in healthy volunteers). The increase of alpha2-macroglobulin inhibition capacity in patients was paralleled by the appearance of a large signal on Western blots, suggesting the formation of additional complexes. Our results demonstrate alpha2-macroglobulin to have more flexibility than had been thought, and it may thereby contribute to a shift in a 30-year-old paradigm.

In the intestinal mucosa, diamine oxidase (DAO) seems to be involved in a feed-back regulation mechanism for the termination of proliferation. Therefore, we studied the DAO activity in large bowel tumors and in the non-affected mucosa of these patients in comparison with patients having a normal large mucosa. The DAO activity in the tumor tissue itself was diminished by 85% as compared to the surrounding mucosa. Comparing the colonic mucosa of normal and tumor bearing individuals, the DAO activity in cancer patients was diminished by 22%, while it was elevated by 64% in patients with polyps (biphasic response of the DAO activity). Histologically proven hyperproliferative mucosal alterations were indicated by a reduced DAO activity with 75% sensitivity and 42% specificity. It remains open whether this limited specificity may indicate a more sensitive reaction of the DAO activity to proliferative mucosal alterations than the histological examinations.