Effects of neuroactive steroids on myelin of peripheral nervous system

Peripheral nervous system (PNS) possess both classical (e.g. progesterone receptor, PR, androgen receptor, AR) and non-classical (e.g. GABA_A receptor) steroid receptors and consequently may represent a target for the action of neuroactive steroids. Our data have indicated that neuroactive steroids, like for instance, progesterone, dihydroprogesterone, tetrahydroprogesterone, dihydrotestosterone and 3-diol, stimulate both in vivo and in vitro (Schwann cell cultures), the expression of two important proteins of the myelin of peripheral nerves, the glycoprotein Po (Po) and the peripheral myelin protein 22 (PMP22). It is important to highlight that the mechanisms by which neuroactive steroids exert their effects on the expression of Po and PMP22 involve different kind of receptors depending on the steroid and on the myelin protein considered. In particular, at least in culture of Schwann cells, the expression of Po seems to be under the control of PR, while that of PMP22 needs the GABA_A receptor.

Because Po and PMP22 play an important physiological role for the maintenance of the multilamellar structure of the myelin of the PNS, the present observations might suggest the utilization of neuroactive steroids as new therapeutically approaches for the rebuilding of the peripheral myelin.     

Control of the expression of human neuropeptide Y by leptin: in vitro studies

Neuropeptide Y (NPY) participates in the regulation of reproduction and food intake. The adipose-secreted hormone, leptin, has also been involved in these processes, and has been shown to exert its effects in part by controlling NPY synthesis and release at the hypothalamic level. In the present study, we utilized the SH-SY5Y human neuroblastoma cell line, to study the leptin-NPY interrelationships. SH-SY5Y cells were found to express leptin receptors (RT-PCR and Western blot analyses). A 24-h treatment with leptin at different concentrations did not affect NPY gene expression, but resulted in a stimulation of NPY release. This stimulated secretion was blocked by the combined treatment with leptin and the muscarinic agonist carbachol or the phorbol ester TPA. Leptin and carbachol also caused an increased intracellular content of NPY. In conclusion, the SH-SY5Y human neuroblastoma cell line appears to be a suitable in vitro model for studying the pharmacological effects of leptin on the biosynthesis and secretion of NPY.     

Glucose effects on lung surfactant kinetics in conscious pigs

The primary goal of this study was to investigate the effects of glucose infusion on surfactant phosphatidylcholine (PC) metabolic kinetics in the lungs. A new stable isotope tracer model was used in which [1,2-(13)C(2)]acetate and uniformly labeled [U-(13)C(16)]palmitate were infused in 12 normal overnight-fasted pigs to quantify lung surfactant kinetics with or without glucose infusion (24 mg. kg(-1). min(-1)). With glucose infusion, the rate of surfactant PC incorporation from de novo synthesized palmitate increased from the control value of 2.1 +/- 0.2 to 15.5 +/- 1.9 nmol PC-bound palmitate. h(-1). g wet lung(-1) (P < 0.05), whereas the incorporation rate from plasma preformed palmitate decreased from the control value of 20.9 +/- 1.9 to 11.6 +/- 1.1 nmol palmitate. h(-1). g wet lung(-1) (P < 0.05). The palmitate composition in lamellar body surfactant PC increased from the control value of 61.7 +/- 2.1% to 75.9 +/- 0.6% (P < 0.05). The surfactant PC secretion rate decreased from the control value of 239.0 +/- 26.1 to 81.9 +/- 5.3 nmol PC-bound palmitate. h(-1). g wet lung(-1) (P < 0.05). We conclude that, whereas surfactant secretion was inhibited by glucose infusion, neither total surfactant PC synthesis nor the surfactant PC pool size was significantly affected due to an increased reliance on de novo synthesized fatty acids.     

A study of Choughs'' vocal repertoire: variability related to individuals, sexes and ages

Summary The calls uttered by Choughs (Pyrrhocorax pyrrhocorax) on Islay (S-W Scotland) were recorded during the breeding season. We analysed the vocal repertoire and the degree of call variation, among and within individuals. Eight structurally different calls were identified in Choughs' vocal repertoire. Significant differences in temporal and frequency variables of calls were found between fledglings and adults, whereas females' and males' calls turned out to differ only in two parameters of the commonest call type (chwee-ow). Despite sex-related differences in this call, partners appeared to utter similar versions of it, which suggests that mate vocal mimicry might occur. A certain degree of individuality, i.e. a greater among than within individuals variability, was found in three call types, but the reverse was found in the commonest call of the species. Accordingly, we hypothesise that this call might promote effective species recognition, whereas the other call types would be involved in individual recognition.

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Das stimmliche Repertoire der Alpenkrähe: individuelle, geschlechtliche und altersabhängige Variabilität

Zusammenfassung Während der Brutzeit 1996 wurde das Rufinventar von Alpenkrähen (Pyrrhocorax pyrrhocorax) auf der Insel Islay (SW Schottland) aufgenommen und hinsichtlich individueller Variation und Unterschieden zwischen verschiedenen Individuen analysiert. Acht grundsätzlich verschiedene Rufe wurden unterschieden. Signifikante Unterschiede bestanden zwischen flüggen Jungvögeln und Altvögeln in der Ruffrequenz und der zeitlichen Abfolge der Rufe. Männchen und Weibchen unterschieden sich dagegen nur geringfügig in dem am häufigsten vorgetragenen Ruf. Ungeachtet dieser geringen sexuellen Unterschiede riefen Paarpartner sehr ähnlich, was als Hinweise auf eine Stimmenmimikrie angesehen wird. In drei Ruftypen fand sich eine gewisse Individualität mit größerer Variablität zwischen verschiedenen als innerhalb eines Rufers, wogegen der häufigste Ruf von allen Individuen sehr ähnlich vorgetragen wurde. Es wird geschlossen, daß dieser Ruf der Arterkennung dient, die anderen dagegen mehr der individuellen Erkennung.

     

Association between GM3 and CD4-Ick complex in human peripheral blood lymphocytes

The aim of this study was to further elucidate our previous observation on molecular interaction of GM3, CD4 and p56^lck in microdomains of human peripheral blood lymphocytes (PBL). We analyzed GM3 distribution by immunoelectron microscopy and the association between GM3 and CD4-p56^lck complex by scanning confocal microscopy and co-immunoprecipitation experiments. Scanning confocal microscopy analysis showed an uneven signal distribution of GM3 molecules over the surface of human lymphocytes. Nearly complete colocalization areas indicated that CD4 molecules were distributed in GM3-enriched plasma membrane domains. Co-immunoprecipitation experiments revealed that CD4 and p56^lck were immunoprecipitated by IgG anti-GM3, demonstrating that GM3 tightly binds to the CD4-p56^lck complex in human PBL. In order to verify whether GM3 association with CD4 molecules may depend on the presence of p56^lck, we analyzed this association in U937, a CD4+and p56^lck negative cell line. The immunoprecipitation with anti-GM3 revealed the presence of a 58[emsp4 ]kDa band immunostained with anti-CD4 Ab, suggesting that the GM3-CD4 interaction does not require its association with p56^lck. These findings support the view that GM3 enriched-domains may represent a functional multimolecular complex involved in signal transduction and cell activation.     

New approaches to the study of sphingolipid enriched membrane domains: The use of microscopic autoradiography to reveal metabolically tritium labeled sphingolipids in cell cultures

This paper is the first report on the use of the electron microscopy autoradiography technique to detect metabolically tritium labeled sphingolipids in intact cells in culture.To label cell sphingolipids, human fibroblasts in culture were fed by a 24 hours pulse, repeated 5 times, of 3×10^–7 M [1-³H]sphingosine. [1-³H]sphingosine was efficently taken up by the cells and very rapidly used for the biosynthesis of complex sphingolipids, including neutral glycolipids, gangliosides, ceramide and sphingomyelin. The treatment with [1-³H]sphingosine did not induce any morphological alteration of cell structures, and well preserved cells, plasma membranes, and intracellular organelles could be observed by microscopy.Ultrathin sections from metabolic radiolabeled cells were coated with autoradiographic emulsion. One to four weeks of exposition resulted in pictures where the location of radioactive sphingolipids was evidenced by the characteristic appearance of silver grains as irregular coiled ribbons of metallic silver. Radioactive sphingolipids were found at the level of the plasma membranes, on the endoplasmic reticulum and inside of cytoplasmic vesicles. Thus, electron microscopy autoradiography is a very useful technique to study sphingolipid-enriched membrane domain organization and biosynthesis.