Evidence that the atypical 5-HT3 receptor ligand, [3H]-BRL46470, labels additional 5-HT3 binding sites compared to [3H]-granisetron.

1. The radioligand binding characteristics of the 3H-derivative of the novel 5-HT3 receptor antagonist BRL46470 were investigated and directly compared to the well characterized 5-HT3 receptor radioligand [3H]-granisetron, in tissue homogenates prepared from rat cerebral cortex/hippocampus, rat ileum, NG108-15 cells, HEK-5-HT3As cells and human putamen. 2. In rat cerebral cortex/hippocampus, rat ileum, NG108-15 cell and HEK-5-HT3As cell homogenates, [3H]-BRL46470 bound with high affinity (Kd (nM): 1.57 +/- 0.18, 2.49 +/- 0.30, 1.84 +/- 0.27, 3.46 +/- 0.36, respectively; mean +/- s.e. mean, n = 3-4) to an apparently homogeneous saturable population of sites (Bmax (fmol mg-1 protein): 102 +/- 16, 44 +/- 4, 968 +/- 32 and 2055 +/- 105, respectively; mean +/- s.e. mean, n = 3-4) but failed to display specific binding in human putamen homogenates. 3. In the same homogenates of rat cerebral cortex/hippocampus, rat ileum, NG108-15 cells, HEK-5-HT3As cells and human putamen as used for the [3H]-BRL46470 studies, [3H]-granisetron also bound with high affinity (Kd (nM): 1.55 +/- 0.61, 2.31 +/- 0.44, 1.89 +/- 0.36, 2.03 +/- 0.42 and 6.46 +/- 2.58 respectively; mean +/- s.e. mean, n = 3-4) to an apparently homogeneous saturable population of sites (Bmax (fmol mg-1 protein): 39 +/- 4, 20 +/- 2, 521 +/- 47, 870 +/- 69 and 18 +/- 2, respectively; mean +/- s.e. mean, n = 3-4).(ABSTRACT TRUNCATED AT 250 WORDS)     

Locomotory characteristics of fibroblasts within a three-dimensional collagen lattice: modulation by a helium/neon soft laser.

It has been postulated that low energy (soft) lasers can enhance wound healing. Considering the importance of cell locomotion in the wound healing process, we have studied the effects of a helium/neon laser upon the locomotory behaviour of a population of fibroblasts migrating within a three-dimensional hydrated collagen lattice. Statistical methods were used to quantify cell three-dimensional trajectories obtained using a computer-assisted tracking system. A two-minute exposure of embryonic fibroblasts to soft laser light decreased the speed and increased the frequency and duration of stops compared to controls. The locomotory phenotype induced in embryonic fibroblasts by the laser light resembled that of the developmentally older c20 fibroblasts, which are known to express a more mature locomotory phenotype. The relevance of these results to wound healing is discussed.     

Structural superfamilies of the complement system

The complete primary structures of nearly all the components, regulatory proteins and membrane-associated receptors of the complement system have now been determined by a combination of protein and cDNA sequence analysis. Based on homologies at the amino acid sequence level, three distinct classes of protein domain are evident. They are the C3, C4, C5 family; the serine proteases, and the short consensus repeat family, which is characterized by the widespread occurrence of a novel 60 amino acid repeat structure. A particular feature of the repeat structures in this last family is that they form the structural and functional domains of a range of complement proteins of distinct function, all of which interact with C3b and/or C4b. Detailed analysis of the gene structures of some of these proteins has been carried out. The results have shown that the intron/exon organization of the serine protease domains of factor B and C2 are related to the classical serine proteases at the DNA level. Each short consensus repeat in factor B, C2, C4b-binding protein, murine factor H and also the functionally unrelated interleukin-2 receptor in all except one case is encoded exactly by a single exon, which defines this novel structural unit at the DNA level.     

Is the mdr 1 gene relevant in chronic lymphocytic leukemia?

Chronic lymphocytic leukemia (CLL) is a progressive disease in which chemotherapy may result in temporary suppression of the peripheral blood lymphocyte count, but cure is not usually possible. Drug resistance mechanisms and the multidrug resistant (MDR) phenotype may be relevant to the therapeutic response. We have studied 34 patients with CLL (seven untreated, 27 treated), screening both DNA and RNA with the mdr 1 gene probe. In pure lymphocyte populations from 10 normal subjects, low levels of mdr 1 RNA expression were found. Eighteen CLL patients (four untreated, 14 treated) had levels of mdr 1 RNA expression above the normal range. No evidence of mdr 1 gene amplification could be found in these patients. Sequential estimations of RNA levels in three patients suggest that malignant lymphocytes in CLL can increase mdr 1 expression in response to chemotherapy and return to basal levels on withdrawal of the treatment. Such data raise important questions about the type of timing of cytotoxic therapy in CLL.     

Peripheral serotoninergic receptor sensitivity in senile dementia of the Alzheimer type

Platelet aggregation induced by 5-hydroxytryptamine (5-HT) was used as a measure of the functional responsiveness of peripheral 5-HT receptors in controls and drug-free patients suffering from senile dementia of Alzheimer type (SDAT). No significantly different aggregatory response (5-HT/ADP ratio) was noted between the two groups of subjects. If the receptor mediating this response is a 5-HT2 receptor, there is no evidence to suggest that the functional activity of this system is abnormal in SDAT.