Exposición a plaguicidas persistentes y no persistentes en población no expuesta laboralmente de la isla de Tenerife / Exposure to persistent and non-persistent pesticides in a non-occupationally exposed population in Tenerife Island (Spain)

Objetivo: La exposición crónica a plaguicidas no persistentes se ha relacionado con diversas patologías crónicas; sin embargo, pocos estudios han evaluado la exposición a plaguicidas no persistentes en población española. Métodos: En 2007 se determinó la presencia de 24 plaguicidas mediante cromatografía de gases/espectometría de masas en 363 muestras de suero de adultos no laboralmente expuestos de Tenerife. Resultados: El 99,45% presentaron residuos (6 ± 2 plaguicidas/muestra). Los plaguicidas más frecuentes fueron piretroides (96,1%), organofosforados (93,9%) y organoclorados (92,3%). En el 81% de los sujetos se detectaron bifentrina y malatión, considerados neurotóxicos, y en el 50% hexaclorobenceno, DDT y buprofezina. El malatión, un "obesógeno ambiental", se detectó en el 82%, y plaguicidas considerados "disruptores endocrinos" en el 97,2% de las muestras. Conclusiones: Existe una exposición inadvertida a plaguicidas no persistentes que puede afectar a la salud de nuestra población, por lo que se hace necesario incluirlos en los estudios de monitorización (AU)

Objective: Chronic exposure to non-persistent pesticides (NPPs) is of concern because these substances have been associated with chronic diseases. However, few studies have addressed chronic exposure to NPPs in Spanish populations. Methods: We determined the presence of 24 pesticide residues by gas chromatography/mass spectrometry in 363 serum samples obtained from non-occupationally exposed adults from Tenerife island in 2007. Results: Most of the samples (99.45%) showed detectable residues (6 ± 2 pesticides per sample). The most frequently detected pesticides were pyrethrins (96.1%), organophosphates (93.9%) and organochlorines (92.3%). The neurotoxicants bifenthrin and malathion were detected in 81% of the samples and hexachlorobenzene DDT and buprofezin in more than 50%. Malation, an "environmental obesogen", was detected in 82%, and "endocrine disrupter" pesticides were present in 97.2% of the samples. Conclusions: Because there is clear, continuous and inadvertent exposure to NPPs that may be inducing adverse effects on human health, NPPs should be included in biomonitoring studies (AU)

[Exposure to persistent and non-persistent pesticides in a non-occupationally exposed population in Tenerife Island (Spain)]. / Exposición a plaguicidas persistentes y no persistentes en población no expuesta laboralmente de la isla de Tenerife.

OBJECTIVE: Chronic exposure to non-persistent pesticides (NPPs) is of concern because these substances have been associated with chronic diseases. However, few studies have addressed chronic exposure to NPPs in Spanish populations. METHODS: We determined the presence of 24 pesticide residues by gas chromatography/mass spectrometry in 363 serum samples obtained from non-occupationally exposed adults from Tenerife island in 2007. RESULTS: Most of the samples (99.45%) showed detectable residues (6 ± 2 pesticides per sample). The most frequently detected pesticides were pyrethrins (96.1%), organophosphates (93.9%) and organochlorines (92.3%). The neurotoxicants bifenthrin and malathion were detected in 81% of the samples and hexachlorobenzene DDT and buprofezin in more than 50%. Malation, an "environmental obesogen", was detected in 82%, and "endocrine disrupter" pesticides were present in 97.2% of the samples. CONCLUSIONS: Because there is clear, continuous and inadvertent exposure to NPPs that may be inducing adverse effects on human health, NPPs should be included in biomonitoring studies.

Regrowth of transected retinal ganglion cell axons despite persistent astrogliosis in the lizard (Gallotia galloti).

We analysed the astroglia response that is concurrent with spontaneous axonal regrowth after optic nerve (ON) transection in the lizard Gallotia galloti. At different post-lesional time points (0.5, 1, 3, 6, 9 and 12 months) we used conventional electron microscopy and specific markers for astrocytes [glial fibrillary acidic protein (GFAP), vimentin (Vim), sex-determining region Y-box-9 (Sox9), paired box-2 (Pax2)¸ cluster differentiation-44 (CD44)] and for proliferating cells (PCNA). The experimental retina showed a limited glial response since the increase of gliofilaments was not significant when compared with controls, and proliferating cells were undetectable. Conversely, PCNA(+) cells populated the regenerating ON, optic tract (OTr) and ventricular wall of both the hypothalamus and optic tectum (OT). Subpopulations of these PCNA(+) cells were identified as GFAP(+) and Vim(+) reactive astrocytes and radial glia. Reactive astrocytes up-regulated Vim at 1 month post-lesion, and both Vim and GFAP at 12 months post-lesion in the ON-OTr, indicating long-term astrogliosis. They also expressed Pax2, Sox9 and CD44 in the ON, and Sox9 in the OTr. Concomitantly, persistent tissue cavities and disorganised regrowing fibre bundles reaching the OT were observed. Our ultrastructural data confirm abundant gliofilaments in reactive astrocytes joined by desmosomes. Remarkably, they also accumulated myelin debris and lipid droplets until late stages, indicating their participation in myelin removal. These data suggest that persistent mammalian-like astrogliosis in the adult lizard ON contributes to a permissive structural scaffold for long-term axonal regeneration and provides a useful model to study the molecular mechanisms involved in these beneficial neuron-glia interactions.

Development of astroglia heterogeneously expressing Pax2, vimentin and GFAP during the ontogeny of the optic pathway of the lizard (Gallotia galloti): an immunohistochemical and ultrastructural study.

The successful regrowth of retinal ganglion cell (RGC) axons after optic nerve (ON) axotomy in Gallotia galloti indicates a permissive role of the glial environment. We have characterised the astroglial lineage of the lizard optic pathway throughout its ontogeny (embryonic stage 30 [E30] to adults) by using electron microscopy and immunohistochemistry to detect the proliferation marker PCNA (proliferating cell nuclear antigen), the transcription factor Pax2 and the gliofilament proteins vimentin (Vim) and GFAP (glial fibrillary acidic protein). PCNA(+) cells were abundant until E39, with GFAP(+)/PCNA(+) astrocytes being observed between E37 and hatching. Proliferation diminished markedly afterwards, being undetectable in the adult optic pathway. Müller glia of the central retina expressed Pax2 from E37 and their endfeet accumulated Vim from E33 and GFAP from E37 onwards. Astrocytes were absent in the avascular lizard retina, whereas abundant Pax2(+) astrocytes were observed in the ON from E30. A major subpopulation of these astrocytes coexpressed Vim from E35 and also GFAP from E37 onwards; thus the majority of mature astrocytes coexpressed Pax2/Vim/GFAP. The astrocytes were ultrastructurally identified by their gliofilaments, microtubules, dense bodies, desmosomes and glycogen granules, which preferentially accumulated in cell processes. Astrocytes in the adult ON coexpressed both gliofilaments and presented desmosomes indicating a reinforcement of the ON structure; this is physiologically necessary for local adaptation to mechanical forces linked to eye movement. We suggest that astrocytes forming this structural scaffold facilitate the regrowth of RGCs after ON transection.

Leptin receptor activation increases Sam68 tyrosine phosphorylation and expression in human trophoblastic cells.

Leptin is produced in placenta where it has been found to be an important autocrine signal for trophoblastic growth during pregnancy, promoting antiapoptotic and trophic effects. Leptin receptor is present in trophoblastic cells and leptin may fully activate signaling. We have previously implicated the RNA-binding protein Sam68 in leptin signal transduction in immune cells. In the present work, we have studied the possible role of Sam68 in leptin receptor signaling in trophoblastic cells (JEG-3 cells). Leptin dose-dependently stimulated Sam68 phosphorylation in JEG-3 cells, as assessed by immunoprecipitation and immunoblot with anti-phosphotyrosine antibodies. As previously observed in other systems, tyrosine phosphorylation of Sam68 in response to leptin inhibits its RNA binding capacity. Besides, leptin stimulation dose-dependently increases Sam68 expression in JEG-3 cells, as assessed by quantitative PCR. Consistently, the amount of Sam68 protein is increased after 24h of leptin stimulation of trophoblastic cells. In order to study the possible role of Sam68 on leptin receptor synthesis, we employed antisense strategy to knockdown the expression of Sam68. We have found that a decrease in Sam68 expression leads to a decrease in leptin receptor amount in JEG-3 cells, as assessed both by quantitative PCR and immunoblot. These results strongly suggest the participation of Sam68 in leptin receptor signaling in human trophoblastic cells, and therefore, Sam68 may mediate some of the leptin effects in placenta.

Reprint of: Metabolic effects and mechanism of action of the chromogranin A-derived peptide pancreastatin.

Pancreastatin is one of the regulatory peptides derived from intracellular and/or extracellular processing of chromogranin A, the soluble acidic protein present in the secretory granules of the neuroendocrine system. While the intracellular functions of chromogranin A include formation and maturation of the secretory granule, the major extracellular functions are generation of biologically active peptides with demonstrated autocrine, paracrine or endocrine activities. In this review, we will focus on the metabolic function of one of these peptides, pancreastatin, and the mechanisms underlying its effects. Many different reported effects have implicated PST in the modulation of energy metabolism, with a general counterregulatory effect to that of insulin. Pancreastatin induces glycogenolysis in liver and lipolysis in adipocytes. Metabolic effects have been confirmed in humans. Moreover, naturally occurring human variants have been found, one of which (Gly297Ser) occurs in the functionally important carboxy-terminus of the peptide, and substantially increases the peptide's potency to inhibit cellular glucose uptake. Thus, qualitative hereditary alterations in pancreastatin's primary structure may give rise to interindividual differences in glucose and lipid metabolism. Pancreastatin activates a receptor signaling system that belongs to the seven-spanning transmembrane receptor coupled to a Gq-PLCß-calcium-PKC signaling pathway. Increased pancreastatin plasma levels, correlating with catecholamines levels, have been found in insulin resistance states, such as gestational diabetes or essential hypertension. Pancreastatin plays important physiological role in potentiating the metabolic effects of catecholamines, and may also play a pathophysiological role in insulin resistance states with increased sympathetic activity.

Role of leptin in the activation of immune cells.

Adipose tissue is an active endocrine organ that secretes various humoral factors (adipokines), and its shift to production of proinflammatory cytokines in obesity likely contributes to the low-level systemic inflammation that may be present in metabolic syndrome-associated chronic pathologies such as atherosclerosis. Leptin is one of the most important hormones secreted by adipocytes, with a variety of physiological roles related to the control of metabolism and energy homeostasis. One of these functions is the connection between nutritional status and immune competence. The adipocyte-derived hormone leptin has been shown to regulate the immune response, innate and adaptive response, both in normal and pathological conditions. The role of leptin in regulating immune response has been assessed in vitro as well as in clinical studies. It has been shown that conditions of reduced leptin production are associated with increased infection susceptibility. Conversely, immune-mediated disorders such as autoimmune diseases are associated with increased secretion of leptin and production of proinflammatory pathogenic cytokines. Thus, leptin is a mediator of the inflammatory response.

Metabolic effects and mechanism of action of the chromogranin A-derived peptide pancreastatin.

Pancreastatin is one of the regulatory peptides derived from intracellular and/or extracellular processing of chromogranin A, the soluble acidic protein present in the secretory granules of the neuroendocrine system. While the intracellular functions of chromogranin A include formation and maturation of the secretory granule, the major extracellular functions are generation of biologically active peptides with demonstrated autocrine, paracrine or endocrine activities. In this review, we will focus on the metabolic function of one of these peptides, pancreastatin, and the mechanisms underlying its effects. Many different reported effects have implicated PST in the modulation of energy metabolism, with a general counterregulatory effect to that of insulin. Pancreastatin induces glycogenolysis in liver and lipolysis in adipocytes. Metabolic effects have been confirmed in humans. Moreover, naturally occurring human variants have been found, one of which (Gly297Ser) occurs in the functionally important carboxy-terminus of the peptide, and substantially increases the peptide's potency to inhibit cellular glucose uptake. Thus, qualitative hereditary alterations in pancreastatin's primary structure may give rise to interindividual differences in glucose and lipid metabolism. Pancreastatin activates a receptor signaling system that belongs to the seven-spanning transmembrane receptor coupled to a Gq-PLCbeta-calcium-PKC signaling pathway. Increased pancreastatin plasma levels, correlating with catecholamines levels, have been found in insulin resistance states, such as gestational diabetes or essential hypertension. Pancreastatin plays important physiological role in potentiating the metabolic effects of catecholamines, and may also play a pathophysiological role in insulin resistance states with increased sympathetic activity.

Oleoylethanolamide, a natural ligand for PPAR-alpha, inhibits insulin receptor signalling in HTC rat hepatoma cells.

Oleoylethanolamide (OEA) is a lipid mediator belonging to the fatty acid ethanolamides family. It is produced by intestine and adipose tissue. It inhibits food intake and body weight gain, and has hypolipemiant action in vivo, as well as a lipolytic effect in vitro. OEA is a PPAR-alpha agonist, and recently it has been found that OEA is an endogenous ligand of an orphan receptor. Previously, we have shown that OEA inhibits insulin-stimulated glucose uptake in isolated adipocytes, and produces glucose intolerance in rats. In the present work, we have studied another insulin target cell, the hepatocyte using a rat hepatoma cell line (HTC), and we have studied the cross-talk of OEA signalling with metabolic and mitotic signal transduction of insulin receptor. OEA dose-dependently activates JNK and p38 MAPK, and inhibits insulin receptor phosphorylation. OEA inhibits insulin receptor activation, blunting insulin signalling in the downstream PI3K pathway, decreasing phosphorylation of PKB and its target GSK-3. OEA also inhibits insulin-dependent MAPK pathway, as assessed by immunoblot of phosphorylated MEK and MAPK. These effects were reversed by blocking JNK or p38 MAPK using pharmacological inhibitors (SP 600125, and SB 203580). Since OEA is an endogenous PPAR-alpha agonist, we investigated whether a pharmacologic agonist (WY 14643) may mimic the OEA effect on insulin receptor signalling. Activation of PPAR-alpha by the pharmacological agonist WY14643 in HTC hepatoma cells is sufficient to inhibit insulin signalling and this effect is also dependent on p38 MAPK but not JNK kinase. In summary, OEA inhibits insulin metabolic and mitogenic signalling by activation of JNK and p38 MAPK via PPAR-alpha.

Tenascin-R and axon growth-promoting molecules are up-regulated in the regenerating visual pathway of the lizard (Gallotia galloti).

It is currently unclear whether retinal ganglion cell (RGC) axon regeneration depends on down-regulation of axon growth-inhibitory proteins, and to what extent outgrowth-promoting substrates contribute to RGC axon regeneration in reptiles. We performed an immunohistochemical study of the regulation of the axon growth-inhibiting extracellular matrix molecules tenascin-R and chondroitin sulphate proteoglycan (CSPG), the axon outgrowth-promoting extracellular matrix proteins fibronectin and laminin, and the axonal tenascin-R receptor protein F3/contactin during RGC axon regeneration in the lizard, Gallotia galloti. Tenascin-R and CSPG were expressed in an extracellular matrix-, oligodendrocyte/myelin- and neuron-associated pattern and up-regulated in the regenerating optic pathway. The expression pattern of tenascin-R was not indicative of a role in channeling or restriction of re-growing RGC axons. Up-regulation of fibronectin, laminin, and F3/contactin occurred in spatiotemporal patterns corresponding to tenascin-R expression. Moreover, we analyzed the influence of substrates containing tenascin-R, fibronectin, and laminin on outgrowth of regenerating lizard RGC axons. In vitro regeneration of RGC axons was not inhibited by tenascin-R, and further improved on mixed substrates containing tenascin-R together with fibronectin or laminin. These results indicate that RGC axon regeneration in Gallotia galloti does not require down-regulation of tenascin-R or CSPG. Presence of tenascin-R is insufficient to prevent RGC axon growth, and concomitant up-regulation of axon growth-promoting molecules like fibronectin and laminin may override the effects of neurite growth inhibitors on RGC axon regeneration. Up-regulation of contactin in RGCs suggests that tenascin-R may have an instructive function during axon regeneration in the lizard optic pathway.

The use of bioluminescence resonance energy transfer for the study of therapeutic targets: application to tyrosine kinase receptors.

During recent years, the bioluminescence resonance energy transfer (BRET) methodology has emerged as a powerful technique for the study of protein-protein interactions. This review focuses on recent work demonstrating the power of BRET for the study of tyrosine kinase receptors, using insulin and IGF-1 receptors as models. The authors show that BRET can be used to monitor ligand-induced conformational changes within homodimeric insulin and IGF-1 receptors, as well as heterodimeric insulin/IGF-1 hybrid receptors. BRET can also be used to study, in real time and in living cells, the interaction of tyrosine kinase receptors with cellular partners negatively or positively involved in the regulation of intracellular signalling (protein tyrosine phosphatases, molecular adaptors). In addition, BRET can be used to develop high-throughput screening assays for the search of molecules with therapeutic interest and could, therefore, constitute a valuable tool for laboratories involved in drug discovery.

Monitoring the activation state of insulin/insulin-like growth factor-1 hybrid receptors using bioluminescence resonance energy transfer.

In cells expressing both the insulin receptor isoform A (IRA) and the insulin-like growth factor-1 receptor (IGF1R), the presence of hybrid receptors, made up of an alphabeta-IRA chain associated with an alphabeta-IGF1R chain, has been demonstrated. These heterodimers are found in normal cells, and they also seem to play crucial roles in a number of cancers. However, they remain difficult to study, due to the concomitant presence of IRA and IGF1R homodimers. Using bioluminescence resonance energy transfer (BRET), we have developed assays to specifically monitor the activation state of IRA/IGF1R hybrids, both in vitro and in living cells. The first assay allowed the study of ligand-induced conformational changes within hybrid receptors purified from cells cotransfected with one type of receptor fused to Renilla reniformis luciferase (Rluc), and the other type of receptor fused to yellow fluorescent protein (YFP). In these conditions, only hybrid receptors were BRET-competent. In the second assay, the activation state of IRA/IGF1R hybrids was monitored in real time, in living cells, by cotransfection of kinase-dead versions of IRA-Rluc or IGF1R-Rluc, wild-type untagged IRA or IGF1R, and a YFP-tagged soluble version of the substrate-trapping mutant of protein tyrosine phosphatase 1B (YFP-PTP1B-D181A-Cter). In hybrid receptors, trans-phosphorylation of the kinase-dead alphabeta-Rluc moiety by the wild-type alphabeta moiety induced the recruitment of YFP-PTP1B-D181A-Cter, resulting in a hybrid-specific ligand-induced BRET signal. Therefore, both methods allow monitoring of the activity of IRA/IGF1R hybrid receptor and could be used to detect molecules of therapeutic interest for the treatment of cancer.

Peculiar and typical oligodendrocytes are involved in an uneven myelination pattern during the ontogeny of the lizard visual pathway.

We studied the myelination of the visual pathway during the ontogeny of the lizard Gallotia galloti using immunohistochemical methods to stain the myelin basic protein (MBP) and proteolipid protein (PLP/DM20), and electron microscopy. The staining pattern for the PLP/DM20 and MBP overlapped during the lizard ontogeny and was first observed at E39 in cell bodies and fibers located in the temporal optic nerve, optic chiasm, middle optic tract, and in the stratum album centrale of the optic tectum (OT). The expression of these proteins extended to the nerve fiber layer (NFL) of the temporal retina and to the outer strata of the OT at E40. From hatching onwards, the labeling became stronger and extended to the entire visual pathway. Our ultrastructural data in postnatal and adult animals revealed the presence of both myelinated and unmyelinated retinal ganglion cell axons in all visual areas, with a tendency for the larger axons to show the thicker myelin sheaths. Moreover, two kinds of oligodendrocytes were described: peculiar oligodendrocytes displaying loose myelin sheaths were only observed in the NFL, whereas typical medium electron-dense oligodendrocytes displaying compact myelin sheaths were observed in the rest of the visual areas. The weakest expression of the PLP/DM20 in the NFL of the retina appears to be linked to the loose appearance of its myelin sheaths. We conclude that typical and peculiar oligodendrocytes are involved in an uneven myelination process, which follows a temporo-nasal and rostro-caudal gradient in the retina and ON, and a ventro-dorsal gradient in the OT.

Pancreastatin: multiple actions on human intermediary metabolism in vivo, variation in disease, and naturally occurring functional genetic polymorphism.

RATIONALE: The chromogranin A (CHGA) fragment pancreastatin (human CHGA250-301) impairs glucose metabolism, but the role of human pancreastatin in vivo remains unexplored. METHODS: We studied brachial arterial infusion of pancreastatin (CHGA273-301-amide at approximately 200 nm) on forearm metabolism of glucose, free fatty acids, and amino acids. Plasma pancreastatin was measured in obesity or type 2 diabetes. Systematic discovery of amino acid variation was performed, and the potency of one variant in the active carboxyl terminus (Gly297Ser) was tested. RESULTS: Pancreastatin decreased glucose uptake by approximately 48-50%; the lack of change in forearm plasma flow indicated a metabolic, rather than hemodynamic, mechanism. A control CHGA peptide (catestatin, CHGA352-372) did not affect glucose. Insulin increased glucose uptake, but pancreastatin did not antagonize this action. Pancreastatin increased spillover of free fatty acids by about 4.5- to 6.4-fold, but not spillover of amino acids. Insulin diminished spillover of both free fatty acids and amino acids, but these actions were not reversed by pancreastatin. Plasma pancreastatin was elevated approximately 3.7-fold in diabetes, but was unchanged during weight loss. Proteolytic cleavage sites for pancreastatin in vivo were documented by matrix-assisted laser desorption ionization/time of flight mass spectrometry. Three pancreastatin variants were discovered: Arg253Trp, Ala256Gly, and Gly297Ser. The Gly297Ser variant had unexpectedly increased potency to inhibit glucose uptake. CONCLUSIONS: The dysglycemic peptide pancreastatin is specifically and potently active in humans on multiple facets of intermediary metabolism, although it did not antagonize insulin. Pancreastatin is elevated in diabetes, and the variant Gly297Ser had increased potency to inhibit glucose uptake. The importance of human pancreastatin in vivo as well as its natural variants is established.

Oleylethanolamide impairs glucose tolerance and inhibits insulin-stimulated glucose uptake in rat adipocytes through p38 and JNK MAPK pathways.

Oleylethanolamide (OEA) is a lipid mediator that inhibits food intake and body weight gain and also exhibits hypolipemiant actions. OEA exerts its anorectic effects peripherally through the stimulation of C-fibers. OEA is synthesized in the intestine in response to feeding, increasing its levels in portal blood after the meal. Moreover, OEA is produced by adipose tissue, and a lipolytic effect has been found. In this work, we have examined the effect of OEA on glucose metabolism in rats in vivo and in isolated adipocytes. In vivo studies showed that acute administration (30 min and 6 h) of OEA produced glucose intolerance without decreasing insulin levels. Ex vivo, we found that 10 min of preincubation with OEA inhibited 30% insulin-stimulated glucose uptake in isolated adipocytes. Maximal effect was achieved at 1 microM OEA. The related compounds palmitylethanolamide and oleic acid had no effect, suggesting a specific mechanism. Insulin-stimulated GLUT4 translocation was not affected, but OEA promoted Ser/Thr phosphorylation of GLUT4, which may impair transport activity. This phosphorylation may be partly mediated by p38 and JNK kinases, since specific inhibitors (SB-203580 and SP-600125) partly reverted the inhibitory effect of OEA on insulin-stimulated glucose uptake. These results suggest that the lipid mediator OEA inhibits insulin action in the adipocyte, impairing glucose uptake via p38 and JNK kinases, and these effects may at least in part explain the glucose intolerance produced in rats in vivo. These effects of OEA may contribute to the anorectic effects induced by this mediator, and they might be also relevant for insulin resistance in adipose tissue.

S100 immunoreactive glial cells in the forebrain and midbrain of the lizard Gallotia galloti during ontogeny.

We identified S100 immunoreactive cells in the brain of the lizard Gallotia galloti during ontogeny using immunohistochemical techniques for light and electron microscopy. In double labeling experiments with antibodies specific for S100A1 and S100B (anti-S100) and proliferative cell nuclear antigen (anti-PCNA), myelin basic protein (anti-MBP), phosphorylated neurofilaments (SMI-31), glial fibrillary acidic protein (anti-GFAP), or glutamine synthetase (anti-GS), we detected S100-like immunoreactivity in glial cells but never in neurons. Restricted areas of the ventricular zone were stained in the hypothalamus from E32 to postnatal stages, and in the telencephalon at E35, E36, and in adults. S100 immunoreactivity was observed predominantly in scattered PCNA-negative cells that increased in number from E35 to the adult stage in the myelinated tracts of the brain and had the appearance of oligodendrocytes. Quantitative analysis revealed that all of the S100-positive glial cells were GFAP-negative, whereas most of the S100-positive glial cells were GS-positive. Ultrastructurally, most of these S100-positive/GS-positive glial cells resembled oligodendrocytes of light and medium electron density. In adult lizards, a small subpopulation of astrocyte-like cells was also stained in the pretectum. We conclude that in the lizard S100 can be considered a marker of a subpopulation of oligodendrocytes rather than of astrocytes, as is the case in mammals. The S100-positive subpopulation of oligodendrocytes in the lizard could represent cells actively involved in the process of myelination during development and in the maintenance of myelin sheaths in the adult.

Neuronal differentiation patterns in the optic tectum of the lizard Gallotia galloti.

This study examines in detail the sequences of morphological differentiation and deduces mode of migration into specific layers of all types of neurons present in the optic tectum of the lizard Gallotia galloti. It complements previous similar work on tectal histogenesis in the chick. It was found that the neuronal population diversity in the lizard tectum can be reduced by developmental analysis to three neuroblast classes, called Types I, II and III. These classes correspond closely to those present in the developing avian tectum. Neurons belonging to each developmental class were characterized by their initial polarity, mode of translocation into the mantle layer and pattern of sprouting of primary axonal and dendritic processes. Each class produced along time a subset of the cell types distinguished in the mature tectum. Some aspects of sauropsidian tectal histogenesis are also common of other vertebrates, suggesting that fundamental mechanisms of tectal neuronal differentiation are conserved in tetrapods. Analysis of evolutive differences of tectal structure points to changes affecting the layering and perhaps the population size of specific cell types. Whereas tectal cell-type homology can be easily fundamented on embryological evidence and seems to be consistent with hodological and, to some extent, functional homology, the periventricular, central and superficial strata of the tectum are heterogeneous in cellular composition in different species and therefore represent analogous, rather than homologous entities.

Pancreastatin, a chromogranin A-derived peptide, activates protein synthesis signaling cascade in rat adipocytes.

Pancreastatin (PST), a chromogranin A-derived peptide, has been found to modulate glucose, lipid, and protein metabolism in rat adipocytes. PST has an overall counterregulatory effect on insulin action by activating a specific receptor-effector system (Galpha(q/11) protein-PLC-beta-PKC(classical)). However, PST stimulates both basal and insulin-mediated protein synthesis in rat adipocytes. In order to further investigate the mechanisms underlying the effect of PST stimulating protein synthesis, we sought to study the regulation of different components of the core translational machinery by the signaling triggered by PST. Thus, we studied ribosomal p70 S6 kinase, phosphorylation of the cap-binding protein (initiation factor) eIF4E, and phosphorylation of the eIF4E-binding protein 4E-BP1 (PHAS-I). We have found that PST stimulates the S6 kinase activity, as assessed by kinase assay using specific immunoprecipitates and substrate. This effect was checked by Western blot with specific antibodies against the phosphorylated S6 kinase. Thus, PST dose-dependently stimulates Thr421/Ser424 phosphorylation of S6 kinase. Moreover, PST promotes phosphorylation of regulatory sites in 4E-BP1 (PHAS-I) (Thr37, Thr46). The initiation factor eIF4E itself, whose activity is also increased upon phosphorylation, is phosphorylated in Ser209 by PST stimulation. Finally, we have found that these effects of PST on S6 kinase and the translation machinery can be blocked by preventing the activation of PKC. These results indicate that PST stimulates protein synthesis machinery by activating PKC and provides some evidence of the molecular mechanisms involved, i.e., the activation of S6K and the phosphorylation of 4E-BP1 (PHAS-I) and the initiation factor eIF4E.

Development of astroglial cells in the encephalon of Gallotia galloti: A Golgi technique study.

Some variants of the Golgi techniques have been used to study the possible origin and developmental sequence of astroglial cells in the lizard Gallotia galloti. the developmental sequence consists of progressive transformations of astroglial cells originating either from radial glia or from glioblasts. The so-called displaced radial glia, an intermediate cellular type between radial glia and astrocytes, indicate the radial glia/astrocytes transformation. Apparently, glioblasts also evolve into astroblasts that, in turn could develop into immature protoplasmic or fibrous astrocytes, precursors of mature protoplasmic and fibrous astrocytes, respectively. The present study confirms our previous ultrastructural and immunohistochemical studies on the same animal. © 1995 Wiley-Liss, Inc.