Presynaptic regulation of dopaminergic transmission in the striatum

1. In vitro studies have indicated that several transmitters present in the striatum can regulate presynaptically the release of dopamine (DA) from nerve terminals of the nigrostriatal DA neurons. 2. The receptors involved in these local regulatory processes are located or not located on DA nerve terminals. 3. Recent in vivo investigations have demonstrated that the corticostriatal glutamatergic neurons facilitate presynaptically the release of DA and have allowed the analysis of the respective roles of presynaptic events and nerve activity in the control of DA transmission.     

Processing of SP1 precursor in a cell-free system from poly(A+) mRNA of human placenta

Cell-free translation of polyadenylated mRNA from human term placenta in a wheat germ extract, after immunoprecipitation with antibodies directed against purified pregnant serum SP₁, yielded a single polypeptide of 31 kDa. Addition of dog pancreatic microsomal vesicles to the translation system resulted in the appearance of two polypeptides, one of them of 46 kDa and the other of 28 kDa. Both polypeptides were protected from limited proteolysis and when the assay was performed with lytic detergent concentrations in addition to proteases, this protection was abolished indicating that the polypeptides were segregated into the microsomal vesicles. The cleavage of a signal peptide of 3 kDa from the 31 kDa primary translation product gives rise to 28 kDa and accounts for the slight increase in electrophoretic mobility. The treatment of the immunoprecipitated products with Endoglycosidase H and -mannosidase, suggested that only the 46 kDa polypeptide is a glycoprotein.From the results obtained we conclude that SP₁ is synthesized and processed to a glycoprotein of 46 kDa which would be a protomeric form of the oligomers reported in pregnant serum by other authors.Abbreviations PMSF phenylmethyl sulfonylfluoride - TCA trichloroacetic acid - DTT dithiotreitol     

Long-term influence of adjuvant therapy on natural killer cell activity in breast cancer

Summary Unstimulated IFN- and IL2-stimulated (NK) cell activities were investigated in patients with breast cancer who had received either local radiotherapy alone or adjuvant chemotherapeutic treatment with CMF combined with radiotherapy 12 to 18 months previously. When tested against the primarily NK-sensitive K562 cell line, patients who had received adjuvant chemotherapeutic treatment with CMF were shown to have a significantly decreased unstimulated and IFN-stimulated NK cell activity, as compared to both patients after radiotherapy only (P<0.002) and P<0.005, respectively) and healthy control persons (P<0.05). The former group of patients also had a significantly decreased IFN-stimulated NK cell activity, when tested against the primarily NK-insensitive Chang hepatoma cell line, as compared to patients after radiotherapy only (P<0.005) and healthy controls (P<0.05). Moreover, patients after radiotherapy only proved to have a significantly increased unstimulated (P<0.01) and IFN-stimulated NK cell activity (K562: P<0.05; Chang hepatoma cell line: P<0.05), as compared to healthy control individuals. In contrast, no difference in IL2-stimulated NK cell activity was detected. The investigation for the expression of CD3 and/or Leu 19 antigens as phenotypic markers of cells with non-MHC restricted cytotoxicity showed a significantly lower percentage of cells with the CD3+ phenotype in patients with breast cancer, irrespective of the chosen post-operative treatment, as compared to healthy controls (P<0.01). Finally, patients with breast cancer who had received radiotherapy only had a significant trend towards an increased percentage of CD³+/Leu 19+ PMNC, as compared to both patients after CMF treatment (P<0.05) and healthy controls (P<0.025). We conclude that patients with breast cancer vary on a long-term basis in their NK activity and in the phenotype of their PMNC depending on their post-operative adjuvant management.Abbreviations NK natural killer cells - IFN interferon - IL 2 interleukin 2 - CMF cyclophosphamide, methotrexate, fluorouracil - ER oestrogen receptor - PMNC peripheral blood mononuclear cells - MHC major histocompatibility complex - CTL cytotoxic T lymphocytes     

Pyruvate decarboxylation in astrocytes and in neurons in primary cultures in the presence and the absence of ammonia

Oxidative decarboxylation of [1-¹⁴C]pyruvate was studied in primary cultures of neurons and of astrocytes. The rate of this process, which is a measure of carbon flow into the tricarboxylic acid (TCA) cycle and which is inhibited by its end product, acetyl CoA, was determined under conditions which would either elevate or reduce the components of the malate-aspartate shuttle (MAS). Addition of aspartate (1 mM) was found to stimulate pyruvate decarboxylation in astrocytes whereas addition of glutamate (or glutamine) had no effect. Since aspartate is a precursor for extramitochondrial malate, and thus intramitochondrial oxaloacetate, whereas glutamate and glutamine are not, this suggests that an increase in oxaloacetate level stimulates TCA cycle activity. Conversely, a reduction of the glutamate content by 3 mM ammonia, which might reduce exchange between glutamate and aspartate across the mitochondrial membrane, suppressed pyruvate decarboxylation. This effect was abolished by addition of glutamate or glutamine or exposure to methionine sulfoximine (MSO). These findings suggest that impairment of MAS activity by removal of MAS constituents decreases TCA cycle activity whereas replenishment of these compounds restores the activity of the TCA cycle. No corresponding effects were observed in neurons.     

Electrical stability of erythrocytes in the presence of divalent cations

Erythrocytes suspended in a medium of low ionic strength lyse under the effect of an exponential electrical pulse. The percentage of haemolysed cells decreases several-fold in the presence of divalent cations. The protective action of the ions studied increases in the following order: Ca⁺⁺, Mg⁺⁺, Zn⁺⁺. It is assumed that divalent ions bind to the negative charges of the lipid and protein molecules and reduce their electrostatic repulsion, which results in stabilization of the membranes.     

Citrate utilization by free and immobilized Streptococcus lactis subsp. diacetylactis in continuous culture

Summary The effects of pH, temperature and concentration of citrate were investigated to achieve an optimal production of diacetyl, acetoin and C₂ compounds such as acetaldehyde, acetate and ethanol for free and immobilized cells. The critical conditions of culture, 22°C, pH 4.8, increased the production of C₄ compounds (diacetyl, acetoin, 2, 3 butylene glycol), C₂ compounds (acetaldehyde, ethanol, acetate) and formate. A higher yield of C₂ and C₄ compounds was observed for the immobilized cells than for the free cells in continuous culture. At 75 mMol/l of citrate, the citrate bioconversion yield was 42.8% and 80% for free and immobilized cells, respectively. This paper discusses citrate and lactose utilization and NADH₂ part on diacetyl reduction.     

Microspectrofluorimetric analysis of the formaldehyde-induced fluorophores of 5-hydroxytryptamine and dopamine in intrapulmonary neuroepithelial bodies after administration ofl-hydroxytryptophan andl-DOPA

Summary To demonstrate the intracellular store of 5-hydroxytryptamine and dopamine in pulmonary neuroepithelial bodies of the neonatal rabbit after treatment with the corresponding amino-acid precursorsl-5-hydroxytryptophan orl-3,4-dihydroxyphenylalanine, formaldehyde-induced flourescence in combination with microspectrofluorimetric analysis has been used. Emission spectra and excitation spectra in an extended wavelength range from 240 to 460 nm, the displacement of excitation peaks after exposure to hydrochloric acid vapour, and calculation of peak ratio values 410/260, 380/320, 320/260 for phenylethylamine fluorophores and 385/315 for indolylethylamine fluorphores were performed. Thus, the presence of 5-hydroxytryptamine without occurrence of 5-hydroxytryptophan was demonstrated in pulmonary neuroepithelial bodies after administration of the corresponding biological precursor, while dopamine combined with 5-hydroxytryptamine were clearly revealed after administration ofl-3,4-dihydroxyphenylalanine. The rate of photodecomposition always corroborated these findings.Dedicated to Prefessor Dr. T.H. Schiebler on the occasion of his 65th birthdaySupported by grant nr. 3.0059.81 (to D.W.S.) from the Fund for Medical Scientific Research (Belgium)     

Autoradiographic studies on glucose utilization in individual zone of the rat thymus

Summary Wistar rats were injected intraperitoneally with 2-(¹⁴C)deoxyglucose and their thymuses were processed for thaw-mount autoradiography after 5, 10 or 35 min. Highest levels of radioactivity were demonstrated in the thymic medulla (5-fold higher than in the cortex). Scanning of autoradiograms for regional differences in grain densities indicated particularly intense glucose utilization in the cortico-medullary zone. Differences in glucose utilization between individual thymic zones seem to reflect differences in cellular composition, i. e., ratio of stroma cells to thymocytes.Dedicated to Professor Dr. T.H. Schiebler on the occasion of his 65th birthday     

Fluorescence studies on aged and young erythrocyte populations

Structural changes in red blood cell (RBC) membrane are investigated by fluorescence techniques. Results obtained with three probes (DPH, 3-PM and fluorescamine) indicate a significant increase in membrane rigidity associated with aging of RBCs. Discrepancies between our observations and published data could arise from utilization of experimental conditions closer to physiological conditions in our study. Use of intact RBCs continuously manipulated in a 37 degrees C environment could represent experimental conditions favourable to the identification of rheologic membrane changes in senescent RBCs.