RESUMO
In the early 2000s, a new component of the cost of reproduction was proposed: oxidative stress. Since then the oxidative cost of reproduction hypothesis has, however, received mixed support. Different arguments have been provided to explain this. Among them, the lack of a life-history perspective on most experimental tests was suggested. We manipulated the levels of a key intracellular antioxidant (glutathione) in captive zebra finches (Taeniopygia guttata) during a short period of early life and subsequently tested the oxidative cost of reproduction. Birds were allowed to mate freely in an outdoor aviary for several months. We repeatedly enlarged or reduced their broods to increase or reduce, respectively, breeding effort. Birds whose glutathione levels were reduced during growth showed higher erythrocyte resistance to free radical-induced haemolysis when forced to rear enlarged broods. This supports the hypothesis predicting the occurrence of developing programmes matching early and adult environmental conditions to improve fitness. Moreover, adult males rearing enlarged broods endured higher plasma levels of lipid oxidative damage than control males, whereas adult females showed the opposite trend. As most previous studies reporting non-significant or opposite results used females only, we also discuss some sex-related particularities that may contribute to explain unexpected results.
Assuntos
Glutationa/análise , Estresse Oxidativo , Reprodução/fisiologia , Aves Canoras/fisiologia , Animais , Antioxidantes/análise , Feminino , MasculinoRESUMO
Interacting pathogens and hosts have evolved reciprocal adaptations whose function is to allow host exploitation (from the pathogen stand point) or minimize the cost of infection (from the host stand point). Once infected, two strategies are offered to the host: parasite clearing (resistance) and withstanding the infection while paying a low fitness cost (tolerance). In both cases, the immune system plays a central role. Interestingly, whatever the defence strategy adopted by the host, this is likely to have an effect on parasite evolution. Given their short generation time and large population size, parasites are expected to rapidly adapt to the environmental conditions provided by their hosts. The immune system can therefore represent a powerful engine of parasite evolution, with the direction of such evolutionary trajectory depending on, among other factors, (i) the type of mechanism involved (resistance or tolerance) and (ii) the damage induced by overreacting immune defences. In this article, I will discuss these different issues focusing on selected examples of recent work conducted on two bird pathogens, the protozoa responsible for avian malaria (Plasmodium sp.) and the bacterium Mycoplasma gallisepticum.
Assuntos
Doenças das Aves/imunologia , Malária Aviária/imunologia , Infecções por Mycoplasma/veterinária , Mycoplasma gallisepticum/fisiologia , Plasmodium/fisiologia , Animais , Evolução Biológica , Doenças das Aves/microbiologia , Aves/classificação , Aves/imunologia , Interações Hospedeiro-Parasita , Tolerância Imunológica , Malária Aviária/parasitologia , Infecções por Mycoplasma/imunologia , Infecções por Mycoplasma/microbiologiaRESUMO
Aging is commonly attributed to age-related changes in oxidative damage due to an increased production of reactive oxygen species (ROS) and a weakened efficacy of enzymatic antioxidants. These age-related changes might therefore modify the use of dietary antioxidants, including carotenoids. As carotenoids are closely associated with the expression of secondary sexual signals, the allocation of carotenoids to sexual signal versus antioxidant defences may vary with age. In this study, we explored how carotenoid-based ornament and antioxidant activity varied with age and how an inflammatory-induced oxidative burst affected ornament and antioxidant activity across a range of ages. Using zebra finches (Taeniopygia guttata) as a model species, we assessed circulating carotenoids, beak coloration and the plasma antioxidant status of birds of different ages before and after an inflammatory challenge. Our results show that old individuals display similar carotenoid-based sexual signals regardless of the availability of circulating carotenoids, suggesting a terminal investment of old individuals in their last reproductive event. Additionally, we found that an inflammatory insult induced a decrease in the total antioxidant activity and in the expression of a carotenoid-based sexual signal in the oldest individuals. These results suggest that old individuals pay an extra cost of immune activation possibly because the efficiency of antioxidant machinery varies with age.
Assuntos
Envelhecimento/fisiologia , Antioxidantes/fisiologia , Carotenoides/metabolismo , Tentilhões/metabolismo , Pigmentos Biológicos/fisiologia , Animais , Bico/fisiologia , Feminino , MasculinoRESUMO
S100B is a Ca2+ binding protein mainly secreted by astrocytes in the vertebrate brain that is considered a multifunctional cytokine and/or a damage-associated molecular pattern (DAMP) protein and a marker of brain injury and neurodegeneration when measured in different body fluids. It has been widely shown that this protein can exert diverse effects in neural cultures depending on its concentration, having detrimental effects at micromolar concentrations. The molecular mechanisms underlying this effect are still largely unknown. This study attempts to delineate the genome-wide gene expression analysis of the events associated with exposure to micromolar concentration of S100B in a human neuroblastoma cell line. In this experimental condition cells undergo a severe perturbation of lipid homeostasis along with cell cycle arrest. These mechanisms might reasonably mediate some aspects of the S100B-related detrimental effects of S100B, although obvious differences between mature neurons and neuroblastoma cells have to be considered.
Assuntos
Ciclo Celular , Colesterol/metabolismo , Fatores de Crescimento Neural/genética , Neuroblastoma/genética , Proteínas S100/genética , Transcrição Gênica , Perfilação da Expressão Gênica , Homeostase , Humanos , Fatores de Crescimento Neural/metabolismo , Neuroblastoma/metabolismo , Análise de Sequência com Séries de Oligonucleotídeos , Subunidade beta da Proteína Ligante de Cálcio S100 , Proteínas S100/metabolismo , Células Tumorais CultivadasRESUMO
Biological invasions expose parasites to new invasive hosts in addition to their local hosts. However, local parasites are often less successful in infecting and exploiting their new hosts. This may have major consequences for the competitive ability of hosts, and finally on the fate of the parasite-host community. In Burgundy (Eastern France), the acanthocephalan parasite, Pomphorhynchus laevis, infects 2 amphipod species living in sympatry: the native Gammarus pulex and the invasive Gammarus roeseli. While P. laevis affects the behaviour and the immunity of G. pulex, G. roeseli seems unaffected by the infection. In this study, we examined in detail the ability of the parasite to affect the immune system and resource storage of both gammarid species. We found that the infection was associated with a general decrease of the prophenoloxidase activity, haemocyte density, resistance to an artificial bacterial infection and level of sugar reserves in G. pulex, but not in G. roeseli. These results demonstrate a differential ability of P. laevis to exploit its local and its invasive gammarid hosts. Potential mechanisms of these differential physiological alterations and their potential consequences on the coexistence of both gammarid species in sympatry are discussed.
Assuntos
Acantocéfalos/fisiologia , Anfípodes/parasitologia , Interações Hospedeiro-Parasita/fisiologia , Adaptação Fisiológica , Anfípodes/classificação , Anfípodes/enzimologia , Anfípodes/imunologia , Animais , Comportamento Animal/fisiologia , Catecol Oxidase/metabolismo , Precursores Enzimáticos/metabolismo , Hemócitos/fisiologia , Comportamento Predatório/fisiologia , Especificidade da EspécieRESUMO
Sertoli cells are located in the testes where they control several key functions in spermatogenesis. Over the past 30 years, Sertoli cells have been upgraded from a simple scaffold-like structural system to a dynamic functional system of intercellular support that delivers potent immunomodulatory and trophic factors. Since the discovery of new Sertoli cell secretory products, these cells have been utilized in experimental cell transplantation and co-transplantation protocols aimed at treating both chronic inflammatory and degenerative disorders. For these reasons, this work reviews the application of both naked and microencapsulated Sertoli cells used in cell transplantation studies of several chronic or autoimmune diseases such as diabetes mellitus, Laron dwarfism, and Duchenne muscular dystrophy and in studies aimed at the prevention of skin allograft rejection.
Assuntos
Células de Sertoli/fisiologia , Células de Sertoli/transplante , Animais , Humanos , MasculinoRESUMO
Previous in vitro studies have shown that the Ca2+-regulated S100B protein modulates the assembly-disassembly of microtubules (MTs) and type III intermediate filaments (IFs). In the present report, by double immunofluorescence cytochemistry S 100B was localized to both GFAP/vimentin IFs and MTs as well as to centrosomes in U251 glial cells. In cells treated with the MT-depolymerizing agent, colchicine, S100B remained associated with the rearranged GFAP IFs throughout the cell and, at the cell periphery, vimentin IFs. In cells treated with the MT stabilizing agent, taxol, S100B followed partly the rearrangement of MTs and partly the rearrangement of IFs. Under the latter condition, bundles of MTs with their associated S100B appeared surrounded and/or flanked by rearranged IFs with their associated S100B. Colocalization of S100B with closely arranged IFs and MTs was best evident in cells manipulated with taxol and in triton-cytoskeletons. In these cases, MTs and their associated S100B appeared surrounded and/or flanked by and/or intermingled with IFs and their associated S100B. Also, a preferential association of S100B with GFAP vs. vimentin IFs could be observed near the nucleus where colocalization of S100B with MTs was also maximal. Condensation of IFs and alteration of the MT network caused by treatment of cells with the phosphatase inhibitor, okadaic acid, resulted in a concomitant condensation/alteration of the S100B immunoreactivity. The present results lend support to the possibility that S100B may be an important factor implicated in the regulation of the dynamics of MTs and IFs.
Assuntos
Proteínas de Ligação ao Cálcio/metabolismo , Filamentos Intermediários/metabolismo , Microtúbulos/metabolismo , Fatores de Crescimento Neural/metabolismo , Neuroglia/metabolismo , Proteínas S100 , Colchicina/farmacologia , Proteína Glial Fibrilar Ácida/metabolismo , Neuroglia/ultraestrutura , Ácido Okadáico/farmacologia , Paclitaxel/farmacologia , Subunidade beta da Proteína Ligante de Cálcio S100 , Células Tumorais Cultivadas , Vimentina/metabolismoRESUMO
BACKGROUND: CDH is a major birth defect, characterized by high mortality. How the initial defective mesenchymal substructures affects muscle malformation is unclear. Defects of genes involved in diaphragmatic development, such as friend-of-GATA2 (Fog2), may play an important role in its pathogenesis. We investigated the expression of Fog2 and proteins of myogenesis in a series of CDH and in diaphragms at different fetal ages, in order to clarify the role of muscular components during diaphragmatic development in cases with CDH. MATERIAL AND METHODS: Specimen were obtained from seven diaphragms of CDH cases undergoing surgery, 3 entire diaphragms from non repaired CDH, 5 control diaphragms at different gestational ages (16, 17, 22, 32, and 40g.w.), and 3 biopsy samples of normal voluntary muscle. The thickness of diaphragms at the edge of the defect in CDH and in developing diaphragms was measured. All samples were processed for HE staining and immunohistochemistry. Immunohistochemical expression of MyoD, Myf4, Pax7, Mib1 and Fog2 was evaluated. RESULTS: Mean thickness at the edge of the defect was 4.14mm. Contralateral hemi-diaphragm in 3 autopsies and in controls at 32 and 40weeks measured 2.25mm; histology showed a higher density of desmin-positive muscular cells at the edge of defect. CDH displayed scattered Myf4-positive cells (range 0%-10%, mean 2.4%), numerous Pax7-positive cells (range 0%-24%, mean 12.1%) and less than 1% Mib1-positive cells. Controls showed a reduction of positive cell with the progression of gestational age for Myf4 (30% at 16 weeks, 20% at 17 weeks, 5% at 22 weeks, 1% at 32 and 40 weeks), Pax7 (85% at 16 weeks and 17 weeks, 35% at 22 weeks, 11% at 32 weeks) and Mib1 (20% at 16 weeks, 8% at 17 weeks, 7% at 22weeks, 2% at 32 weeks). Fog-2 was diffusely positive in mesenchymal, mesothelial and muscular cells, in diaphragms from 16 to 22 weeks, decreasing to 20% of positive muscular cells in 32-week diaphragm. In CDH only mesothelial and mesenchymal cells were positive. Stem cell markers were negative in cases and controls. COMMENT: CDH shows a thick muscular border, with high number of mature muscle cells and significant increase of quiescent satellite cells (PAX7+, Mib1-). Abnormal architecture may affect the normal process of myogenesis and thus signaling and cell-cell interactions of myocytes. The expression of Fog2 in mesothelial and mesenchymal cells in CDH demonstrates the absence of a genetic defect involving Fog2 in our cases. Being Fog2 expressed in muscle cells at early stage supports the hypothesis that the altered diaphragmatic genesis may undermine also the muscular component instead of the only mesenchymal one.
Assuntos
Diafragma/anormalidades , Hérnias Diafragmáticas Congênitas/diagnóstico , Desenvolvimento Muscular , Feminino , Humanos , Imuno-Histoquímica , Recém-Nascido , Masculino , Estudos ProspectivosRESUMO
We investigated the expression and the subcellular localization of S100A1 and S100B, two Ca(2+)-binding proteins of the EF-hand type, in replicating myoblasts and fused myotubes. Northern blot and reverse transcriptase-polymerase chain reaction analyses revealed the presence of S100A1 mRNA and S100B mRNA respectively, in myoblasts. Immunofluorescence and immunogold electron microscopy were used to localize individual proteins in myoblasts and myotubes. In the present report we document that: (1) in replicating myoblasts S100B is localized to intracellular membranes, including Golgi membranes, vimentin intermediate filaments (IFs) and microtubule (MT) structures; (2) in the same cells S100A1 is found associated with intracellular membranes; (3) following treatment of replicating myoblasts with colchicine, a fraction of S100B remains colocalized with bundled and collapsed vimentin IFs, whereas another fraction follows the destiny of endoplasmic membranes; (4) under the same conditions S100A1, like a fraction of S100B, follows the collapse of the endoplasmic reticulum around the nucleus; and (5) in fused myotubes S100A1 is found diffusely in the cytoplasm, whereas S100B is mostly found associated with vimentin IFs. These data suggest that in the skeletal myogenic cell line used in the present study S100A1 and S100B might share binding sites on or close to intracellular membranes, but display a significant degree of target specificity with respect of IFs and MTs. The results of these analyses suggest that expression of S100B in skeletal muscle cells may be developmentally regulated and lend support to the possibility that S100B might regulate the MT and IF dynamics.
Assuntos
Proteínas de Ligação ao Cálcio/metabolismo , Cálcio/farmacologia , Filamentos Intermediários/metabolismo , Microtúbulos/metabolismo , Músculo Esquelético/metabolismo , Fatores de Crescimento Neural/metabolismo , Proteínas S100 , Sequência de Aminoácidos , Animais , Antineoplásicos Fitogênicos/farmacologia , Sequência de Bases , Northern Blotting , Proteínas de Ligação ao Cálcio/imunologia , Linhagem Celular , Citoplasma/metabolismo , Imunofluorescência , Complexo de Golgi/metabolismo , Membranas Intracelulares/metabolismo , Dados de Sequência Molecular , Músculo Esquelético/ultraestrutura , Fatores de Crescimento Neural/imunologia , Paclitaxel/farmacologia , Ratos , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Subunidade beta da Proteína Ligante de Cálcio S100 , Vimentina/metabolismoRESUMO
Protein gene product 9.5 (PGP 9.5), which in the normal nervous system is restricted to certain neurons, has been detected in two glioma cell lines, rat C6 and human GL15, by immunoblotting and immunocytochemistry. Its expression in these cells depends on the cellular growth state, being maximal between the first and second post-plating day. Only a faint PGP 9.5 immunoreactivity can be observed in glioma cells after the eleventh post-plating day, i.e. about one week after confluency has been reached. The present results suggest that PGP 9.5 in cultured glial cells is maximally expressed during the growth phase and that the protein could play a role during brain development in glial cells, in reactive gliosis, or in tumorigenesis of the glial lineage.
Assuntos
Glioma/metabolismo , Neuropeptídeos/metabolismo , Sequência de Aminoácidos , Animais , Western Blotting , Divisão Celular , Humanos , Técnicas In Vitro , Dados de Sequência Molecular , Ratos , Células Tumorais Cultivadas , Ubiquitina TiolesteraseRESUMO
The subcellular distribution of annexin V, a calcium-dependent phospholipid- and membrane-binding protein, in a human-derived cell line, GL15, was investigated by immunocytochemistry at light and electron microscope levels. Annexin V was found diffusely in the cytoplasm and associated with plasma membranes, membranes delimiting cytoplasmic vacuoles, membranes of the endoplasmic reticulum, and filamentous structures the identity of which remains to be established. By immunocytochemistry at the light microscope level and immunochemistry, the expression of annexin V in these cells was found to depend on cellular growth stage, being maximal soon after plating and progressively declining thereafter. However, re-expression of annexin V was observed whenever cell proliferation slowed down or arrested. These findings suggest that annexin V in glioma cells is mostly expressed in connection with cell differentiation. Also, the present ultrastructural data suggest that plasma membranes, membranes of the endoplasmic reticulum and the cytoskeleton are prominent sites of action of annexin V in vivo, thus lending support to the possibility that this protein might have a role in the regulation of cytoskeleton elements and/or of the structural organization of membranes.
Assuntos
Anexina A5/análise , Neuroglia/química , Animais , Bovinos , Diferenciação Celular , Citoesqueleto/química , Glioma , Humanos , Imuno-Histoquímica , Proteínas de Membrana/análise , Neuroglia/citologia , Suínos , Células Tumorais CultivadasRESUMO
S100A1 and S100B are members of a multigenic family of Ca(2+)-binding proteins of the EF-hand type highly abundant in astrocyte and striated muscle cells that have been implicated in the Ca(2+)-dependent regulation of several intracellular activities including the assembly and disassembly of microtubules and type III intermediate filaments. In the present work we tested S100A1 and S100B for their ability to cause microtubule and/or intermediate filament disassembly in situ using triton-cytoskeletons obtained from U251 glioma cells and rat L6 myoblasts. Our results indicate that: (i) both proteins cause a Ca(2+)-dependent disassembly of cytoplasmic microtubules in a dose-dependent manner; (ii) the S100A1- and S100B-inhibitory peptide, TRTK-12, blocks the S100A1 and S100B effects on microtubules; (iii) S100A1Delta88-93, an S100A1 mutant lacking the C-terminal extension, does not affect microtubule stability; and (iv) no obvious S100A1- or S100B-dependent intermediate filament disassembly could be observed under the experimental conditions used in the present study, but S100A1- and S100B-dependent microtubule disassembly results in a tendency of vimentin intermediate filaments to aggregate into bundles and/or to condense. Together, these results suggest that S100A1 and S100B probably cause microtubule disassembly by interacting with the microtubule wall, and that the two proteins do not affect intermediate filament stability via interaction with preformed intermediate filaments, in agreement with previous biochemical investigation. Our present data lend support to the possibility that S100A1 and S100B might have a role in the in vivo regulation of the state of assembly of microtubules in a Ca(2+)-regulated manner and, potentially, on microtubule-based activities in astrocytes and myoblasts. Also, these data suggest that the both S100 proteins use their C-terminal extension for interacting with microtubules.
Assuntos
Astrócitos/ultraestrutura , Proteínas de Ligação ao Cálcio/farmacologia , Microtúbulos/efeitos dos fármacos , Microtúbulos/metabolismo , Fatores de Crescimento Neural/farmacologia , Proteínas S100 , Animais , Astrócitos/metabolismo , Western Blotting , Cálcio/metabolismo , Proteínas de Ligação ao Cálcio/genética , Proteínas de Ligação ao Cálcio/metabolismo , Bovinos , Citoplasma/metabolismo , Detergentes , Glioma , Técnicas In Vitro , Filamentos Intermediários/metabolismo , Células LLC-PK1 , Fibras Musculares Esqueléticas/metabolismo , Fibras Musculares Esqueléticas/ultraestrutura , Mutagênese , Fatores de Crescimento Neural/metabolismo , Octoxinol , Ratos , Subunidade beta da Proteína Ligante de Cálcio S100 , Suínos , Células Tumorais Cultivadas , Vimentina/metabolismoRESUMO
The environmental factors that drive the evolution of parasite life histories are mostly unknown. Given that hosts provide the principal environmental features parasites have to deal with, and given that these features (such as resource availability and immune responses) are well characterized by the life history of the host, we may expect natural selection to result in covariation between parasite and host life histories. Moreover, some parasites show a high degree of host specificity, and cladistic analyses have shown that host and parasite phylogenies can be highly congruent. These considerations suggest that parasite and host life histories may covary. The central argument in the theory of life history evolution concerns the existence of trade-offs between traits. For parasitic nematodes it has been shown that larger body sizes induce higher fecundity, but this is achieved at the expense of delayed maturity. As high adult mortality would select for reduced age at maturity, the selective benefit of increased fecundity is expressed only if adult mortality is low. Parasite adult mortality may depend on a number of factors, including host longevity. Here we tested the hypothesis concerning the positive covariation between parasite body size (which reflects parasite longevity) and host longevity. To achieve this goal, we used the association between the pinworms (Oxyuridae, Nematoda) and their primate hosts. Oxyurids are highly host specific and are supposed to be involved in a coevolutionary process with their hosts. We found that female parasite body length was positively correlated with host longevity after correcting for phylogeny and host body mass. Conversely, male parasite body length and host longevity were not correlated. These results confirm that host longevity may represent a constraint on the evolution of body size in oxyurids, at least in females. The discrepancy between female and male oxyurids is likely to depend on the particular mode of reproduction of this taxon (haplodiploidy), which should result in weak (or even null) selection pressures to an increase of body size in males.
Assuntos
Interações Hospedeiro-Parasita , Nematoides , Primatas/parasitologia , Animais , Evolução Biológica , Feminino , MasculinoRESUMO
We studied the activity and the ultracytochemical localization of membrane-bound guanylate cyclase (GC) after stimulation with rat atrial natriuretic peptide (rANP), porcine brain natriuretic peptide (pBNP), rat brain natriuretic peptide (rBNP), or porcine C-type natriuretic peptide (CNP) in rat C6 glioma cells during proliferation or following exposure of confluent cells to dibutyryl cyclic AMP (db-cAMP) or retinoic acid (RA). Under our experimental conditions all peptides were activators of GC as demonstrated by the accumulation of cGMP within cells. During proliferation of C6 cells, the amounts of cGMP remained approximately constant. However, at subconfluency, confluency and postconfluency, the GC reaction product was located at different sites in C6 cells. At subconfluency, GC reaction product was on membranes of protoplasmic extensions, at postconfluency, GC reaction product was in association with membranes of cell bodies, and at confluency, both localizations of GC reaction product were detected. Incubation of confluent cells in culture medium containing db-cAMP or RA induced the appearance of long and slender protoplasmic extensions. Under these conditions, the GC reaction product was localized exclusively to these processes. These data suggest that GC is differentially located depending on the state of growth of glial cells, and that in differentiating glial cells GC is preferentially located in cell processes.
Assuntos
Fator Natriurético Atrial/farmacologia , Glioma/enzimologia , Guanilato Ciclase/metabolismo , Proteínas do Tecido Nervoso/farmacologia , Proteínas/farmacologia , Animais , Bucladesina/farmacologia , Divisão Celular/efeitos dos fármacos , Meios de Cultura , GMP Cíclico/metabolismo , Glioma/ultraestrutura , Guanilil Imidodifosfato/farmacologia , Peptídeo Natriurético Encefálico , Peptídeo Natriurético Tipo C , Ratos , Suínos , Tretinoína/farmacologia , Células Tumorais CultivadasRESUMO
An insect preference for floral symmetry may be maintained because plants with symmetrical flowers, which are able to control developmental processes under given environmental conditions, also are able to provide more pollinator rewards than plants with asymmetrical flowers. Alternatively, insects may have an inherent preference for symmetrical structures and thereby impose selection for the maintenance of symmetry in flowers even in the absence of any pollinator rewards. We tested for an insect preference for radially symmetrical flowers by using horizontally placed units of four circular coloured flower models varying in size and symmetry. The shape and colour of the model flowers did not resemble any naturally occurring flowers in the environment. Insects and Hymenoptera, respectively (five species of Diptera and one species of Coleoptera) that visited the flower models clearly preferred symmetrical models over asymmetrical ones, and the ranking of visits to the models reflected a preference for large, symmetrical flowers. These results provide evidence for a preference for symmetrical flower models, even in the absence of pollinator rewards.
RESUMO
The Ca2+-modulated, dimeric proteins of the EF-hand (helix-loop-helix) type, S100A1 and S100B, that have been shown to inhibit microtubule (MT) protein assembly and to promote MT disassembly, interact with the type III intermediate filament (IF) subunits, desmin and glial fibrillary acidic protein (GFAP), with a stoichiometry of 2 mol of IF subunit/mol of S100A1 or S100B dimer and an affinity of 0.5-1.0 microM in the presence of a few micromolar concentrations of Ca2+. Binding of S100A1 and S100B results in inhibition of desmin and GFAP assemblies into IFs and stimulation of the disassembly of preformed desmin and GFAP IFs. S100A1 and S100B interact with a stretch of residues in the N-terminal (head) domain of desmin and GFAP, thereby blocking the head-to-tail process of IF elongation. The C-terminal extension of S100A1 (and, likely, S100B) represents a critical part of the site that recognizes desmin and GFAP. S100B is localized to IFs within cells, suggesting that it might have a role in remodeling IFs upon elevation of cytosolic Ca2+ concentration by avoiding excess IF assembly and/or promoting IF disassembly in vivo. S100A1, that is not localized to IFs, might also play a role in the regulation of IF dynamics by binding to and sequestering unassembled IF subunits. Together, these observations suggest that S100A1 and S100B may be regarded as Ca2+-dependent regulators of the state of assembly of two important elements of the cytoskeleton, IFs and MTs, and, potentially, of MT- and IF-based activities.
Assuntos
Proteínas de Ligação ao Cálcio/fisiologia , Cálcio/metabolismo , Proteína Glial Fibrilar Ácida/metabolismo , Filamentos Intermediários/metabolismo , Fatores de Crescimento Neural/fisiologia , Proteínas S100 , Humanos , Microtúbulos/metabolismo , Subunidade beta da Proteína Ligante de Cálcio S100RESUMO
I investigated longitudinal measures of haemogregarine load in the host lizard Lacerta vivipara over 2 yr (1992-1993). Lizards with heavy parasite infections in 1992 were still suffering from heavy parasite infections in 1993. Such data show that lizards have limited ability to recover from high levels of haemogregarine infection. Modifications of host behavior and of life-history traits may represent a more effective and less costly response to haemogregarine infection in this species.
Assuntos
Apicomplexa/fisiologia , Lagartos/parasitologia , Infecções Protozoárias em Animais , Animais , Células Sanguíneas/parasitologia , Feminino , Interações Hospedeiro-Parasita , Infecções por Protozoários/parasitologiaRESUMO
Patterns of haemogregarine load, aggregation, and prevalence as a function of host age in the lizard Lacerta vivipara were investigated. These parameters may provide evidence for the potential effect of parasites on host survival. The predictions of theoretical models concerning the shape of parasite load, parasite aggregation, and parasite prevalence across host age were used to test if parasites are a significant source of host mortality. Both age-intensity and age-aggregation curves were found to be peaked, whereas the age-prevalence curve increased with host age, reaching high levels (> 80% of infected hosts). These findings of humped age-aggregation and age-intensity curves are in good agreement with the predictions of the Anderson and Gordon (1982) model and suggest that haemogregarines may influence age-dependent host mortality in this population of L. vivipara.
Assuntos
Envelhecimento/fisiologia , Coccídios/fisiologia , Coccidiose/veterinária , Lagartos/parasitologia , Animais , Coccídios/crescimento & desenvolvimento , Coccidiose/epidemiologia , Coccidiose/parasitologia , Dinâmica Populacional , PrevalênciaRESUMO
The S100 protein family consists of 24 members functionally distributed into three main subgroups: those that only exert intracellular regulatory effects, those with intracellular and extracellular functions and those which mainly exert extracellular regulatory effects. S100 proteins are only expressed in vertebrates and show cell-specific expression patterns. In some instances, a particular S100 protein can be induced in pathological circumstances in a cell type that does not express it in normal physiological conditions. Within cells, S100 proteins are involved in aspects of regulation of proliferation, differentiation, apoptosis, Ca2+ homeostasis, energy metabolism, inflammation and migration/invasion through interactions with a variety of target proteins including enzymes, cytoskeletal subunits, receptors, transcription factors and nucleic acids. Some S100 proteins are secreted or released and regulate cell functions in an autocrine and paracrine manner via activation of surface receptors (e.g. the receptor for advanced glycation end-products and toll-like receptor 4), G-protein-coupled receptors, scavenger receptors, or heparan sulfate proteoglycans and N-glycans. Extracellular S100A4 and S100B also interact with epidermal growth factor and basic fibroblast growth factor, respectively, thereby enhancing the activity of the corresponding receptors. Thus, extracellular S100 proteins exert regulatory activities on monocytes/macrophages/microglia, neutrophils, lymphocytes, mast cells, articular chondrocytes, endothelial and vascular smooth muscle cells, neurons, astrocytes, Schwann cells, epithelial cells, myoblasts and cardiomyocytes, thereby participating in innate and adaptive immune responses, cell migration and chemotaxis, tissue development and repair, and leukocyte and tumor cell invasion.