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S Calvo

Publications and source records attributed to S Calvo.

At least 19 recordsLinked to original sources
PubMed2006

Differential regulation of calcium channel coding genes by prolonged depolarization.

Calcium channels must be subjected to a very precise regulation in order to preserve cell function and viability. Voltage gated calcium channels (VGCC) represent the main pathway for calcium entry in excitable cells. This explains why depolarization induces a rapid-onset and short-term inactivation of calcium currents. Contrarily to this well-documented mechanism to maintain calcium below toxic levels, the regulatory pathways inducing longer-lasting changes and cell surface expression of functional calcium channels are largely unknown. Since calcium is a main player in the activity-dependent regulation of many genes, we hypothesize that calcium channel coding genes could be also subjected to activity-dependent regulation. We have used prolonged depolarization to analyze the effects of sustained intracellular calcium elevation on the mRNAs coding for the different alpha(1) pore-forming subunits of the calcium channels expressed in chromaffin cells. Our findings reveal that persistent depolarization is accompanied by a prolonged intracellular calcium elevation and reduction of calcium current. This calcium current inhibition could be mediated, at least partially, by the downregulation of the mRNAs coding for several alpha(1) subunits. Thus, we show here that depolarization inhibits the expression of Ca(V)1.1, Ca(V)1.2, Ca(V)1.3, Ca(V)2.2 and Ca(V)2.3 mRNAs, while the Ca(V)2.1 mRNA remains unmodified. Moreover, such downregulation of channels depends on calcium entry through the L-type calcium channel, as both mRNA and calcium current changes induced by depolarization are abrogated by L-type channel specific blockers.

Animals↗
PubMed2006

Pyruvate protects cerebellar granular cells from 6-hydroxydopamine-induced cytotoxicity by activating the Akt signaling pathway and increasing glutathione peroxidase expression.

Parkinson disease (PD) is the second-most common age-related neurodegenerative disease and is characterized by the selective destruction of dopaminergic neurons. Increasing evidence indicates that oxidative stress plays a crucial role in the pathogenesis of idiopathic PD. Anti-oxidant agents including catalase, manganese porphyrin and pyruvate confer cytoprotection to different cell cultures when challenged with 6-hydroxydopamine (6-OHDA). Herein we used rat cerebellar granular cell cultures to ascertain the plausible cellular pathways involved in pyruvate-induced cytoprotection against 0.1 mM 6-OHDA. Pyruvate provided cytoprotection in a concentration-dependent manner (2-10 mM). Consistent with its well-established anti-oxidant capacity, pyruvate (10 mM) prevented 6-OHDA-induced lipid peroxidation by blocking the rise in intracellular peroxides and maintaining the intracellular reduced glutathione (GSH) levels. Further experiments revealed that pyruvate increased Akt, but not extracellular signal-regulated kinase phosphorylation. Moreover, phosphatidylinositol 3-kinase (PI3K) inhibitors attenuated pyruvate-induced cytoprotection indicating that PI3K-mediated Akt activation is necessary for pyruvate to induce cytoprotection. On the other hand, pyruvate also up-regulated glutathione peroxidase mRNA levels, but not those of the anti-oxidant enzymes superoxide dismutase-1 and -2, catalase or the anti-apoptotic oncogenes Bcl-2 or Bcl-xL. In summary, our results strongly suggest that pyruvate, besides the anti-oxidant properties related to its structure, exerts cytoprotective actions by activating different anti-apoptotic routes that include gene regulation and Akt pathway activation.

Animals↗
PubMed2005

Chromosome complement of the fungal plant pathogen Fusarium graminearum based on genetic and physical mapping and cytological observations.

A genetic map of the filamentous fungus Fusarium graminearum (teleomorph: Gibberella zeae) was constructed to both validate and augment the draft whole-genome sequence assembly of strain PH-1. A mapping population was created from a cross between mutants of the sequenced strain (PH-1, NRRL 31084, originally isolated from Michigan) and a field strain from Minnesota (00-676, NRRL 34097). A total of 111 ascospore progeny were analyzed for segregation at 235 loci. Genetic markers consisted of sequence-tagged sites, primarily detected as dCAPS or CAPS (n = 131) and VNTRs (n = 31), in addition to AFLPs (n = 66) and 7 other markers. While most markers exhibited Mendelian inheritance, segregation distortion was observed for 25 predominantly clustered markers. A linkage map was generated using the Kosambi mapping function, using a LOD threshold value of 3.5. Nine linkage groups were detected, covering 1234 cM and anchoring 99.83% of the draft sequence assembly. The nine linkage groups and the 22 anchored scaffolds from the sequence assembly could be assembled into four chromosomes, leaving only five smaller scaffolds (59,630 bp total) of the nuclear DNA unanchored. A chromosome number of four was confirmed by cytological karyotyping. Further analysis of the genetic map data identified variation in recombination rate in different genomic regions that often spanned several hundred kilobases.

Chromosome Segregation↗
PubMed2005

Minocycline fails to protect cerebellar granular cell cultures against malonate-induced cell death.

Experimental and clinical studies support the view that the semisynthetic tetracycline minocycline exhibits neuroprotective roles in several models of neurodegenerative diseases, including ischemia, Huntington, Parkinson diseases, and amyotrophic lateral sclerosis. However, recent evidence indicates that minocycline does not always present beneficial actions. For instance, in an in vivo model of Huntington's disease, it fails to afford protection after malonate intrastriatal injection. Moreover, it reverses the neuroprotective effect of creatine in nigrostriatal dopaminergic neurons. This apparent contradiction prompted us to analyze the effect of this antibiotic on malonate-induced cell death. We show that, in rat cerebellar granular cells, the succinate dehydrogenase inhibitor malonate induces cell death in a concentration-dependent manner. By using DFCA, monochlorobimane and 10-N-nonyl-Acridin Orange to measure, respectively, H2O2-derived oxidant species and reduced forms of GSH and cardiolipin, we observed that malonate induced reactive oxygen species (ROS) production to an extent that surpasses the antioxidant defense capacity of the cells, resulting in GSH depletion and cardiolipin oxidation. The pre-treatment for 4 h with minocycline (10-100 microM) did not present cytoprotective actions. Moreover, minocycline failed to block ROS production and to abrogate malonate-induced oxidation of GSH and cardiolipin. Additional experiments revealed that minocycline was also unsuccessful to prevent the mitochondrial swelling induced by malonate. Furthermore, malonate did not induce the expression of the iNOS, caspase-3, -8, and -9 genes which have been shown to be up-regulated in several models where minocycline resulted cytoprotective. In addition, malonate-induced down-regulation of the antiapoptotic gene Bcl-2 was not prevented by minocycline, controversially the mechanism previously proposed to explain minocycline protective action. These results suggest that the minocycline protection observed in several neurodegenerative disease models is selective, since it is absent from cultured cerebellar granular cells challenged with malonate.

Animals↗
PubMed2004

Adrenal medulla calcium channel population is not conserved in bovine chromaffin cells in culture.

During the stress response adrenal medullary chromaffin cells release catecholamines to the bloodstream. Voltage-activated calcium channels present in the cell membrane play a crucial role in this process. Although the electrophysiological and pharmacological properties of chromaffin cell calcium channels have been studied in detail, the molecular composition of these channels has not been defined yet. Another aspect that needs to be explored is the extent to which chromaffin cells in culture reflect the adrenal medulla calcium channel characteristics. In this sense, it has been described that catecholamine release in the intact adrenal gland recruits different calcium channels than those recruited during secretion from cultured chromaffin cells. Additionally, recent electrophysiological studies show that chromaffin cells in culture differ from those located in the intact adrenal medulla in the contribution of several calcium channel types to the whole cell current. However there is not yet any study that compares the population of calcium channels in chromaffin cells with that one present in the adrenal medulla. In order to gain some insight into the roles that calcium channels might play in the adrenal medullary cells we have analyzed the alpha1 subunit mRNA expression profile. We demonstrate that the expression pattern of voltage-dependent calcium channels in cultured bovine chromaffin cells markedly differs from that found in the native adrenal medulla and that glucocorticoids are only partially involved in those differences. Additionally, we show, for the first time, that the cardiac isoform of L-type calcium channel is present in both bovine adrenal medulla and cultured chromaffin cells and that its levels of expression do not vary during culture.

Adrenal Medulla↗
PubMed2002

[Molecular characterization of variable tandem repeat sequence determined during RAPD analysis among Posidonia oceanica insular and coastline populations].

The seagrass Posidonia oceanica plays a multifunctional role in the coastal area as an important and productive component of ecosystems in the Mediterranean Sea. We detected by RAPD analysis with two arbitrary primers genetic differences in P. oceanica collected from several sites in the Southern Mediterranean. By AMOVA analysis we observed a level of about 20% genetic difference among individuals within a population and 80% among populations. A common band of 200 bp was found in all the amplified samples. Cloning and sequencing analysis of this band revealed the presence of a simple tandem repeat sequence (minisatellite) that we called PoTR (Posidonia oceanica tandem repeat). Finally, the ability of PoTR to detect genetic variability in P. oceanica genome was demonstrated by the presence of amplification products of different lengths utilizing primers internal to this sequence.

Base Sequence↗
PubMed2001

Control of Salmonella enteritidis phage type 4 experimental infection by fosfomycin in newly hatched chicks.

One hundred and twenty 1-day-old broiler chickens were divided into four groups: group I unmedicated and orally challenged with 1.5 x 10(8) cfu of Salmonella enteritidis phage type 4; group F infected and treated with 300 ppm of fosfomycin in their drinking water; group CF uninfected and treated, and group C maintained as a control group. Their performance, clinical signs, S. enteritidis PT4 reisolation and biochemistry variables were compared. Group F showed fewer symptoms and gross lesions than those from group 1. Fosfomycin treatment at 300 ppm improved body weight at 7 days of age by 42.3%. S. enteritidis PT4 reisolation in group I was higher than in the treated group, but total decontamination of challenged birds was not achieved. There was an increase in the levels of total protein and globulins in group I but not in the treated group. Fosfomycin caused no adverse effects on chickens from group CF, assessed by performance and biochemical variables. The results indicate that fosfomycin could be used in the treatment of S. enteritidis PT4 experimental infection.

Animals↗
PubMed2001

Molecular dissection of DNA sequences and factors involved in slow muscle-specific transcription.

Transcription is a major regulatory mechanism for the generation of slow- and fast-twitch myofibers. We previously identified an upstream region of the slow TnI gene (slow upstream regulatory element [SURE]) and an intronic region of the fast TnI gene (fast intronic regulatory element [FIRE]) that are sufficient to direct fiber type-specific transcription in transgenic mice. Here we demonstrate that the downstream half of TnI SURE, containing E box, NFAT, MEF-2, and CACC motifs, is sufficient to confer pan-skeletal muscle-specific expression in transgenic mice. However, upstream regions of SURE and FIRE are required for slow and fast fiber type specificity, respectively. By adding back upstream SURE sequences to the pan-muscle-specific enhancer, we delineated a 15-bp region necessary for slow muscle specificity. Using this sequence in a yeast one-hybrid screen, we isolated cDNAs for general transcription factor 3 (GTF3)/muscle TFII-I repeat domain-containing protein 1 (MusTRD1). GTF3 is a multidomain nuclear protein related to initiator element-binding transcription factor TF II-I; the genes for both proteins are deleted in persons with Williams-Beuren syndrome, who often manifest muscle weakness. Gel retardation assays revealed that full-length GTF3, as well as its carboxy-terminal half, specifically bind the bicoid-like motif of SURE (GTTAATCCG). GTF3 expression is neither muscle nor fiber type specific. Its levels are highest during a period of fetal development that coincides with the emergence of specific fiber types and transiently increases in regenerating muscles damaged by bupivacaine. We further show that transcription from TnI SURE is repressed by GTF3 when overexpressed in electroporated adult soleus muscles. These results suggest a role for GTF3 as a regulator of slow TnI expression during early stages of muscle development and suggest how it could contribute to Williams-Beuren syndrome.

Animals↗
PubMed2000

Denervation induces a rapid nuclear accumulation of MRF4 in mature myofibers.

Muscle regulatory factor 4 (MRF4) is a member of the family of myogenic transcription factors, including MyoD, myogenin, and myf-5, that are necessary for the commitment and differentiation of mesoderm to skeletal muscle. Although the function of these transcription factors during embryonic development has been demonstrated, their role in adult muscle has remained elusive. Regulation of the MRF4 gene differs from the genes encoding the other myogenic factors in that its transcripts accumulate in neonatal muscle during maturation and continue to be expressed at relatively high levels in the adult. On the basis of its mRNA expression pattern, MRF4 has been suggested to regulate genes encoding adult contractile proteins and acetylcholine receptor subunits. To test this hypothesis, a specific antiserum was developed to study MRF4 protein expression in adult innervated and denervated muscle, because MRF4 mRNA levels increase by approximately threefold 1 day after nerve resection. By using three different immunohistochemical methods that vary widely in sensitivity, we were unable to detect MRF4 immunoreactivity in adult innervated muscles. The same results were obtained with another MRF4 antiserum generated independently. In contrast, any of these three immunologic techniques readily detected MRF4 immunoreactivity in myofiber and satellite cell nuclei of muscles denervated for 24 hours. The highest proportion of immunopositive nuclei (80%) was found 2-3 days after denervation. Immunoreactivity was no longer detectable by 14 days. There was no differential accumulation of MRF4 protein in the nuclei of satellite cells nor in sole plate (synaptic) nuclei at any time after denervation. No differences were found in the temporal accumulation of MRF4 in nuclei of type I and type II denervated myofibers, consistent with the similar distribution of MRF4 mRNAs in slow- and fast-twitch muscles. Our results are consistent with the lack of phenotype observed in the adult muscles of MRF4-null mutant mice observed by others and suggest that MRF4 may have important roles in the gene programs activated after denervation and during muscle regeneration.

3T3 Cells↗
PubMed2000

Veratridine induces apoptotic death in bovine chromaffin cells through superoxide production.

The molecular mechanisms involved in veratridine-induced chromaffin cell death have been explored. We have found that exposure to veratridine (30 microM, 1 h) produces a delayed cellular death that reaches 55% of the cells 24 h after veratridine exposure. This death has the features of apoptosis as DNA fragmentation can be observed. Calcium ions play an important role in veratridine-induced chromaffin cell death because the cell permeant Ca(2+) chelator BAPTA-AM and extracellular Ca(2+) removal completely prevented veratridine-induced toxicity. Following veratridine treatment, there is a decrease in mitochondrial function and an increase in superoxide anion production. Veratridine-induced increase in superoxide production was blocked by tetrodotoxin (TTX; 10 microM), extracellular Ca(2+) removal and the mitochondrial permeability transition pore blocker cyclosporine A (10 microM). Veratridine-induced death was prevented by different antioxidant treatments including catalase (100 IU ml(-1)), N-acetyl cysteine (100 microM), allopurinol (100 microM) or vitamin E (50 microM). Veratridine-induced DNA fragmentation was prevented by TTX (10 microM). Veratridine produced a time-dependent increase in caspase activity that was prevented by Ca(2+) removal and TTX (10 microM). In addition, calpain and caspases inhibitors partially prevented veratridine-induced death. These results indicate that chromaffin cells share with neurons the molecular machinery involved in apoptotic death and might be considered a good model to study neuronal death during neurodegeneration.

Animals↗
PubMed1999

Expression of interleukin 6 (IL-6) correlates with oestrogen receptor in human breast carcinoma.

Multifunctional cytokines play important and only partially defined roles in mammary tumour development and progression. Normal human mammary epithelial cells constitutively produce interleukin 6 (IL-6), IL-8 and a non-secreted form of tumour necrosis factor. Transformation of mammary epithelial cells by different oncogenes is frequently associated with alterations of cytokine/growth factor production and responsiveness. In the present study we analysed the expression of IL-6 in 149 cases of invasive breast carcinoma and the data have been correlated with clinico-pathological variables including tumour size, histological grade, nodal status, and oestrogen and progesterone receptors, Ki67 and p53, protein expression. Though the majority of breast carcinomas expressed at least low levels of immunoreactive IL-6, we found that expression of this cytokine was inversely associated with histological tumour grade (P = 0.0017), but not with tumour size and nodal status. Ki67 positivity was inversely correlated with IL-6 expression (P = 0.027). Among biological parameters analysed, a direct association was found between the percentage of IL-6-positive cells and that of oestrogen (P = 0.00005) and progesterone (P = 0.025) receptor-positive cells. No correlation was observed between IL-6 and p53 protein expression. These data indicate that down-regulation of IL-6 is associated with highly malignant mammary carcinomas. It will be of interest to evaluate whether alterations of cytokines that are constitutively produced by mammary cells are also associated with high-grade tumours.

Breast Neoplasms↗
PubMed1999

Fiber-type-specific transcription of the troponin I slow gene is regulated by multiple elements.

The regulatory elements that restrict transcription of genes encoding contractile proteins specifically to either slow- or fast-twitch skeletal muscles are unknown. As an initial step towards understanding the mechanisms that generate muscle diversity during development, we have identified a 128-bp troponin I slow upstream element (SURE) and a 144-bp troponin I fast intronic element (FIRE) that confer fiber type specificity in transgenic mice (M. Nakayama et al., Mol. Cell. Biol. 16:2408-2417, 1996). SURE and FIRE have maintained the spatial organization of four conserved motifs (3' to 5'): an E box, an AT-rich site (A/T2) that binds MEF-2, a CACC site, and a novel CAGG motif. Troponin I slow (TnIs) constructs harboring mutations in these motifs were analyzed in transiently and stably transfected Sol8 myocytes and in transgenic mice to assess their function. Mutations of the E-box, A/T2, and CAGG motifs completely abolish transcription from the TnI SURE. In contrast, mutation of the CACC motif had no significant effect in transfected myocytes or on the slow-specific transcription of the TnI SURE in transgenic mice. To assess the role of E boxes in fiber type specificity, a chimeric enhancer was constructed in which the E box of SURE was replaced with the E box from FIRE. This TnI E box chimera, which lacks the SURE NFAT site, confers essentially the same levels of transcription in transgenic mice as those conferred by wild-type SURE and is specifically expressed in slow-twitch muscles, indicating that the E box on its own cannot determine the fiber-type-specific expression of the TnI promoter. The importance of the 5' half of SURE, which bears little homology to the TnI FIRE, in muscle-specific expression was analyzed by deletion and linker scanning analyses. Removal of the 5' half of SURE (-846 to -811) results in the loss of expression in stably transfected but not in transiently expressing myocytes. Linker scanning mutations identified sequences in this region that are necessary for the function of SURE when integrated into chromatin. One of these sites (GTTAATCCG), which is highly homologous to a bicoid consensus site, binds to nuclear proteins from several mesodermal cells. These results show that multiple elements are involved in the muscle-specific activity of the TnIs promoter and that interactions between upstream and downstream regions of SURE are important for transcription in the context of native chromatin.

Animals↗
PubMed1996

Expression of and response to interleukin 6 (IL6) in human mammary tumors.

Multifunctional cytokines play important and only partially defined roles in mammary tumor development and progression. Normal human mammary epithelia] cells (MECs) constitutively produce interleukin (IL) 6, IL8, and a nonsecreted form of tumor necrosis factor. MEC transformation by different oncogenes is frequently associated with alterations of cytokine/growth factor production and responsiveness. This seems particularly true in the case of IL6. Histochemical studies showed that expression of immunoreactive IL6, as compared to normal tissue and to in situ lesions, is significantly reduced in invasive ductal carcinoma. Conversely, the expression of IL6 in invasive lobular carcinoma was enhanced. Expression of TGF-beta1 in mammary neoplasia was in general less intense than that seen in the normal mammary gland. In vitro studies partially supported the in vivo findings: expression of IL6 and TGF-beta1 was significantly down-regulated in cultures derived from both ductal carcinoma and peritumoral tissue. Similarly, responsiveness to IL6 and TGF-beta1 was significantly reduced in neoplastic MECs. The data suggest that alterations of cytokine pathways are present not only in mammary neoplasia, but also in pathologically unaffected breast tissues.

Breast↗
PubMed1996

Transcriptional control of muscle plasticity: differential regulation of troponin I genes by electrical activity.

Plasticity of the skeletal muscle phenotype can result from the selective repression and activation of gene expression in response to innervation patterns. Motoneurons, eliciting different patterns of depolarization, regulate the contractile properties of the myofibers they innervate by selectively activating expression of genes encoding fiber-type-specific (fast vs. slow) contractile proteins. We have analyzed the regulation of the troponin I slow (TnIs) and fast (TnIf) genes as a model to study the molecular mechanisms regulating fiber-type plasticity. We found that expression of the two TnI isoforms is downregulated by denervation. Moreover, TnI expression is upregulated by specific patterns of electrical activity [10 Hz vs. 100 Hz] used to depolarize muscle. We previously isolated the rat TnIs gene and demonstrated that regulatory sequences reside in its upstream region and second intron [Banerjee-Basu S, Buonanno A (1993), Mol Cell Biol 12:5024-5032]. Using transgenic mice, we show that the upstream region of the TnIs gene extending from -949 to +50 is sufficient to confer transcription specifically in slowtwitch muscles. Serial deletions of the TnIs upstream and intronic regions were generated in a CAT reporter vector to delineate transcriptional regulatory elements in transiently transfected Sol8 myotubes. Sequences necessary to confer the highest levels of TnIs transcription mapped to the upstream region between -0.95 and -0.72 kb, and to a 56 bp sequence located in the second intron. Comparison of the at sequence between -0.95 and -0.72 to the human TnIs gene identified a highly homologous region of 128 bp that we named the TnI SURE (slow upstream regulatory element). Alignment of these two SURE sequences with the quail TnI fast intronic regulatory element identified common motifs, namely, two A/T-rich sequences (A/T1 and A/T2) with homology to homeotic protein and MEF2 binding sites, a CACC box, an E box, and a novel motif (GCAGGCA) that we denoted the CAGG box. Mutation of either the A/T2 site, E box, or CAGG box practically abolish the SURE function in transfected myotubes; mutation of the A/T1 and CACC sites has a lesser effect. Using competitive electrophoretic mobility shift assays with nuclear extracts derived from Sol8 myotubes, we demonstrate specific binding to these motifs. The A/T1 and A/T2 sites are shown to form different complexes. The A/T2 site, which bears extensive homology to a MEF2 site, forms complexes that are super shifted by MEF2A antisera and that are competed by a consensus MEF2 site present in the MCK enhancer. Our results demonstrate that the linear arrangement of DNA sequence motifs is conserved in the regulatory elements of the TnI slow and fast genes and suggest that the interaction of multiple protein-DNA complexes are necessary for enhancer function.

Animals↗
PubMed1996

Defective interleukin six expression and responsiveness in human mammary cells transformed by an adeno 5/SV40 hybrid virus.

Mammary epithelial cells (MECs) were isolated and cultured from mammary glands of healthy women undergoing reduction mammoplasty. Normal MECs were infected with the transforming hybrid virus adeno-5/SV40. Two transformed epithelial cell lines, M1 and M2, were obtained, characterised phenotypically and studied for the production of and the response to cytokines and growth regulators. In both cell lines, expression of the SV40 large T antigen was associated with loss of interleukin 6 (IL-6) production and responsiveness as well as with down-regulation of IL-8 and transforming growth factor (TGF)-alpha production. Both M1 and M2 cell lines were capable of forming colonies in semisolid media, but upon injection into severe combined immunodeficient (SCID) mice only M2 cells were tumorigenic. DNA synthesis in M1 cells was partially inhibited by serum or TNF-alpha and weakly stimulated by hydrocortisone (HC) and IL-8. In contrast, M2 cells were totally unresponsive to a variety of growth regulators. Both lines overexpressed the p53 protein at levels about 20-fold higher than those observed in primary MEC cultures, but no mutations of the p53 gene could be detected. The date confirm the view that the expression in human mammary cells of different oncogenes - including the SV40 T antigen - is frequently associated with alterations of cytokine production and responsiveness.

Adenocarcinoma↗
PubMed1996

Extracellular calcium has distinct effects on fast and slow components of the depolarization-induced secretory response from chromaffin cells.

An increase in extracellular Ca2+ concentration from 0.25 to 10 mM enhanced secretion of norepinephrine and epinephrine induced by a high extracellular K+ concentration (75 mM). The increment in extracellular Ca2+ concentration also increased the observed peak inward Ca2+ current in response to long (10-s) depolarizing pulses from a holding potential of -55 mV to +5 mV, from about -26 to -400 pA. However, the total amount of Ca2+ influx into the cell only increased when the extracellular Ca2+ concentration was raised from 0.25 to 1 mM and then remained constant up to 10 mM extracellular Ca2+. ATP is cosecreted with catecholamines following a depolarizing stimulus. Kinetic studies indicated that ATP secretion had two components with time constants, in the presence of 2.5 mM extracellular Ca2+, of approximately 4 and 41 s, being the fast component of secretion produced by the exocytosis of approximately 220 chromaffin granules. The results suggest that, for a given depolarizing stimulus, the size and rate of release for the fast and slow components of secretion are dependent on extracellular Ca2+ concentration.

Adenosine Triphosphate↗
PubMed1995

Characterization of a Stat-like DNA binding activity in Drosophila melanogaster.

The cytokine signaling pathways that activate the Janus family of tyrosine kinases (Jaks) and the "signal transducers and activators of transcription" (Stats) have been well characterized in mammalian systems. Work shown here provides evidence that an analogous signaling pathway exists in Drosophila melanogaster. Because many of the ligand-receptor pairs in Drosophila have not been fully characterized, it was necessary to bypass the receptor stimulation event that normally triggers intracellular Jak/Stat activation. This was done by treating Drosophila Schneider 2 cells with vanadate/peroxide, which has been shown to closely mimic some signaling events triggered by interferon gamma, including the activation of Jak1, Jak2, and the Stat1 alpha protein. Evidence presented here demonstrates that vanadate/peroxide can induce a gamma response region binding complex in Drosophila Schneider 2 cells. This complex contains two phosphoproteins of 100 and 150 kDa, respectively, and shares many features with the vanadate/peroxide-stimulated binding complex in the mammalian system. Southern blot analysis of genomic DNA using the src homology domain 2 (SH2) of Stat1 alpha confirms the presence of a related gene in the Drosophila genome.

Animals↗