RESUMO
OBJECTIVE: The aim of the study was to illustrate the function of circRNA ZFR in aggravating the development of hepatocellular carcinoma (HCC) by upregulating MAP2K1. PATIENTS AND METHODS: CircRNA ZFR levels in 62 paired HCC and paracancerous species were detected. The influence of circRNA ZFR on clinical data of HCC patients was analyzed. After the overexpression or knockdown of circRNA ZFR, changes in viability and clonality of Bel-7402 and Hep3B cells were assessed, respectively. The involvement of circRNA ZFR/MAP2K1 axis in the development of HCC was explored through Luciferase assay and rescue experiments. RESULTS: CircRNA ZFR was highly expressed in HCC species than the paracancerous ones. Higher level of circRNA ZFR predicted more advanced tumor grading of HCC. The knockdown of circRNA ZFR attenuated the proliferative ability of HCC cells, while the overexpression of circRNA ZFR obtained opposite results. MAP2K1 level was positively correlated to that of circRNA ZFR. Luciferase assay uncovered that circRNA ZFR can be targeted by MAP2K1 through specific binding sites. In addition, the overexpression of MAP2K1 could reverse the influence of silenced circRNA ZFR on proliferative ability of HCC cells. CONCLUSIONS: CircRNA ZFR is upregulated in HCC and closely linked to tumor grading. It promotes proliferative ability in HCC by upregulating MAP2K1.
Assuntos
Carcinoma Hepatocelular/metabolismo , Neoplasias Hepáticas/metabolismo , MAP Quinase Quinase 1/metabolismo , RNA Circular/metabolismo , Regulação para Cima , Carcinoma Hepatocelular/patologia , Proliferação de Células , Células Cultivadas , Feminino , Humanos , Neoplasias Hepáticas/patologia , MAP Quinase Quinase 1/genética , Masculino , Pessoa de Meia-Idade , RNA Circular/genéticaRESUMO
Homer EVH1 (Ena/VASP Homology 1) domains interact with proline-rich motifs in the cytoplasmic regions of group 1 metabotropic glutamate receptors (mGluRs), inositol-1,4,5-trisphosphate receptors (IP3Rs), and Shank proteins. We have determined the crystal structure of the Homer EVH1 domain complexed with a peptide from mGluR (TPPSPF). In contrast to other EVH1 domains, the bound mGluR ligand assumes an unusual conformation in which the side chains of the Ser-Pro tandem are oriented away from the Homer surface, and the Phe forms a unique contact. This unusual binding mode rationalizes conserved features of both Homer and Homer ligands that are not shared by other EVH1 domains. Site-directed mutagenesis confirms the importance of specific Homer residues for ligand binding. These results establish a molecular basis for understanding the biological properties of Homer-ligand complexes.
Assuntos
Proteínas de Transporte/química , Proteínas do Citoesqueleto , Mutagênese Sítio-Dirigida/genética , Neuropeptídeos/química , Peptídeos/química , Animais , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Escherichia coli , Proteínas de Arcabouço Homer , Ligantes , Proteínas dos Microfilamentos , Dados de Sequência Molecular , Neuropeptídeos/genética , Neuropeptídeos/metabolismo , Peptídeos/genética , Ratos , Receptores de Glutamato Metabotrópico/metabolismoRESUMO
Homer is a neuronal immediate early gene (IEG) that is enriched at excitatory synapses and binds group 1 metabotropic glutamate receptors (mGluRs). Here, we characterize a family of Homer-related proteins derived from three distinct genes. Like Homer IEG (now termed Homer 1a), all new members bind group 1 mGluRs. In contrast to Homer 1a, new members are constitutively expressed and encode a C-terminal coiled-coil (CC) domain that mediates self-multimerization. CC-Homers form natural complexes that cross-link mGluRs and are enriched at the postsynaptic density. Homer 1a does not multimerize and blocks the association of mGluRs with CC-Homer complexes. These observations support a model in which the dynamic expression of Homer 1a competes with constitutively expressed CC-Homers to modify synaptic mGluR properties.
Assuntos
Proteínas de Transporte/fisiologia , Proteínas do Tecido Nervoso/metabolismo , Neuropeptídeos/fisiologia , Receptores de Glutamato Metabotrópico/metabolismo , Sinapses/metabolismo , Sequência de Aminoácidos , Animais , Encéfalo/metabolismo , Proteínas de Transporte/antagonistas & inibidores , Proteínas de Transporte/química , Proteínas de Transporte/genética , Proteínas de Arcabouço Homer , Camundongos , Dados de Sequência Molecular , Família Multigênica/genética , Neuropeptídeos/antagonistas & inibidores , Neuropeptídeos/química , Neuropeptídeos/genética , Ratos , Distribuição TecidualRESUMO
Group I metabotropic glutamate receptors (mGluRs) activate PI turnover and thereby trigger intracellular calcium release. Previously, we demonstrated that mGluRs form natural complexes with members of a family of Homer-related synaptic proteins. Here, we present evidence that Homer proteins form a physical tether linking mGluRs with the inositol trisphosphate receptors (IP3R). A novel proline-rich "Homer ligand" (PPXXFr) is identified in group 1 mGluRs and IP3R, and these receptors coimmunoprecipitate as a complex with Homer from brain. Expression of the IEG form of Homer, which lacks the ability to cross-link, modulates mGluR-induced intracellular calcium release. These studies identify a novel mechanism in calcium signaling and provide evidence that an IEG, whose expression is driven by synaptic activity, can directly modify a specific synaptic function.
Assuntos
Canais de Cálcio/metabolismo , Proteínas de Transporte/metabolismo , Neuropeptídeos/metabolismo , Prolina/genética , Receptores Citoplasmáticos e Nucleares/metabolismo , Receptores de Glutamato Metabotrópico/metabolismo , Sequência de Aminoácidos , Animais , Cálcio/metabolismo , Canais de Cálcio/genética , Proteínas de Transporte/genética , Proteínas de Transporte/fisiologia , Dinaminas , GTP Fosfo-Hidrolases/genética , Expressão Gênica , Genes Precoces , Ácido Glutâmico/farmacologia , Proteínas de Arcabouço Homer , Receptores de Inositol 1,4,5-Trifosfato , Membranas Intracelulares/metabolismo , Ligantes , Dados de Sequência Molecular , Neuropeptídeos/genética , Neuropeptídeos/fisiologia , Ratos , Receptores Citoplasmáticos e Nucleares/genética , Receptores de Glutamato Metabotrópico/antagonistas & inibidores , Fatores de TempoRESUMO
NMDA receptors are linked to intracellular cytoskeletal and signaling molecules via the PSD-95 protein complex. We report a novel family of postsynaptic density (PSD) proteins, termed Shank, that binds via its PDZ domain to the C terminus of PSD-95-associated protein GKAP. A ternary complex of Shank/GKAP/PSD-95 assembles in heterologous cells and can be coimmunoprecipitated from rat brain. Synaptic localization of Shank in neurons is inhibited by a GKAP splice variant that lacks the Shank-binding C terminus. In addition to its PDZ domain, Shank contains a proline-rich region that binds to cortactin and a SAM domain that mediates multimerization. Shank may function as a scaffold protein in the PSD, potentially cross-linking NMDA receptor/PSD-95 complexes and coupling them to regulators of the actin cytoskeleton.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Proteínas dos Microfilamentos/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Neurônios/química , Receptores de N-Metil-D-Aspartato/metabolismo , Actinas/metabolismo , Animais , Células COS , Proteínas de Transporte/análise , Proteínas de Transporte/química , Cortactina , Citoesqueleto/química , Citoesqueleto/ultraestrutura , Proteína 4 Homóloga a Disks-Large , Hipocampo/citologia , Peptídeos e Proteínas de Sinalização Intracelular , Proteínas de Membrana , Proteínas dos Microfilamentos/análise , Microscopia Imunoeletrônica , Dados de Sequência Molecular , Família Multigênica , Proteínas do Tecido Nervoso/análise , Neurônios/citologia , Neurônios/metabolismo , Estrutura Terciária de Proteína , Coelhos , Ratos , Receptores de N-Metil-D-Aspartato/análise , Proteínas Associadas SAP90-PSD95 , Homologia de Sequência de Aminoácidos , Sinapses/química , Sinapses/metabolismo , Sinapses/ultraestruturaRESUMO
Shank is a recently described family of postsynaptic proteins that function as part of the NMDA receptor-associated PSD-95 complex (Naisbitt et al., 1999 [this issue of Neuron]). Here, we report that Shank proteins also bind to Homer. Homer proteins form multivalent complexes that bind proline-rich motifs in group 1 metabotropic glutamate receptors and inositol trisphosphate receptors, thereby coupling these receptors in a signaling complex. A single Homer-binding site is identified in Shank, and Shank and Homer coimmunoprecipitate from brain and colocalize at postsynaptic densities. Moreover, Shank clusters mGluR5 in heterologous cells in the presence of Homer and mediates the coclustering of Homer with PSD-95/GKAP. Thus, Shank may cross-link Homer and PSD-95 complexes in the PSD and play a role in the signaling mechanisms of both mGluRs and NMDA receptors.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal , Proteínas de Transporte/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Neurônios/química , Neuropeptídeos/metabolismo , Receptores de Glutamato Metabotrópico/metabolismo , Animais , Sítios de Ligação/fisiologia , Células COS , Cálcio/metabolismo , Canais de Cálcio/metabolismo , Proteínas de Transporte/química , Proteínas de Transporte/genética , Proteína 4 Homóloga a Disks-Large , Proteínas de Arcabouço Homer , Humanos , Receptores de Inositol 1,4,5-Trifosfato , Peptídeos e Proteínas de Sinalização Intracelular , Rim/citologia , Proteínas de Membrana , Microscopia Imunoeletrônica , Mutagênese Sítio-Dirigida/fisiologia , Neurônios/metabolismo , Neuropeptídeos/química , Prolina/metabolismo , Estrutura Terciária de Proteína , Coelhos , Ratos , Receptores Citoplasmáticos e Nucleares/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Proteínas Associadas SAP90-PSD95 , Sinapses/química , Sinapses/metabolismo , Sinapses/ultraestrutura , TransfecçãoRESUMO
The proteins of the Homer family bind to proline-rich sequences in group I metabotropic glutamate receptors, inositol trisphosphate receptors, ryanodine receptors, and Shank family proteins. Homer proteins also self associate and function as adaptors to couple interacting proteins. Recent observations indicate a role for Homer complexes in signal transduction, synaptogenesis and receptor trafficking.
Assuntos
Proteínas de Transporte/fisiologia , Neurônios/fisiologia , Neuropeptídeos/fisiologia , Receptores de Glutamato/fisiologia , Transmissão Sináptica/fisiologia , Animais , Proteínas de Arcabouço Homer , HumanosRESUMO
Group I metabotropic glutamate receptors (mGluR1 and 5) couple to intracellular calcium pools by a family of proteins, termed Homer, that cross-link the receptor to inositol trisphosphate receptors. mGluRs also couple to membrane ion channels via G-proteins. The role of Homer proteins in channel modulation was investigated by expressing mGluRs and various forms of Homer in rat superior cervical ganglion (SCG) sympathetic neurons by intranuclear cDNA injection. Expression of cross-linking-capable forms of Homer (Homer 1b, 1c, 2, and 3, termed long forms) occluded group I mGluR-mediated N-type calcium and M-type potassium current modulation. This effect was specific for group I mGluRs. mGluR2 (group II)-mediated inhibition of N-channels was unaltered. Long forms of Homer decreased modulation of N- and M-type currents but did not selectively block distinct G-protein pathways. Short forms of Homer, which cannot self-multimerize (Homer 1a and a Homer 2 C-terminal deletion), did not alter mGluR-ion channel coupling. When coexpressed with long forms of Homer, short forms restored the mGluR1a-mediated calcium current modulation in an apparent dose-dependent manner. Homer 2b induced cell surface clusters of mGluR5 in SCG neurons. Conversely, a uniform distribution was observed when mGluR5 was expressed alone or with Homer short forms. These studies indicate that long and short forms of Homer compete for binding to mGluRs and regulate their coupling to ion channels. In vivo, the immediate early Homer 1a is anticipated to enhance ion channel modulation and to disrupt coupling to releasable intracellular calcium pools. Thus, Homer may regulate the magnitude and predominate signaling output of group I mGluRs.
Assuntos
Canais de Cálcio Tipo N/metabolismo , Proteínas de Transporte/metabolismo , Neuropeptídeos/metabolismo , Canais de Potássio/metabolismo , Receptores de Glutamato Metabotrópico/metabolismo , Animais , Cálcio/metabolismo , Proteínas de Transporte/genética , Proteínas de Transporte/farmacologia , Células Cultivadas , Proteínas de Ligação ao GTP/metabolismo , Proteínas de Arcabouço Homer , Neurônios/citologia , Neurônios/metabolismo , Neuropeptídeos/genética , Neuropeptídeos/farmacologia , Técnicas de Patch-Clamp , Potássio/metabolismo , Ratos , Agregação de Receptores/efeitos dos fármacos , Agregação de Receptores/genética , Receptor de Glutamato Metabotrópico 5 , Receptores de Glutamato Metabotrópico/genética , Proteínas Recombinantes de Fusão/biossíntese , Proteínas Recombinantes de Fusão/farmacologia , Transdução de Sinais/efeitos dos fármacos , Gânglio Cervical Superior/citologia , Gânglio Cervical Superior/metabolismoRESUMO
The physiological actions of neurotransmitter receptors are intimately linked to their proper neuronal compartment localization. Here we studied the effect of the metabotropic glutamate receptor (mGluR)-interacting proteins, Homer1a, b, and c, in the targeting of mGluR5 in neurons. We found that mGluR5 was exclusively localized in cell bodies when transfected alone in cultured cerebellar granule cells. In contrast, mGluR5 was found also in dendrites when coexpressed with Homer1b or Homer1c, and in both dendrites and axons when cotransfected with Homer1a. In dendrites, cotransfected mGluR5 and Homer1b/c formed clusters that colocalized with the synaptic marker synaptophysin. Interestingly when transfected alone, the Homer proteins were also translocated to neurites but did not form such clusters. Depolarization of the neurons with a mixture of ionotropic glutamate receptor agonists, NMDA and kainate, or potassium channel blockers, tetraethylammonium and 4-aminopyridine, induced transient expression of endogenous Homer1a and persistent neuritic localization of transfected mGluR5 even long after degradation of Homer1a. These results suggest that Homer1a/b/c proteins are involved in the targeting of mGluR5 to dendritic synaptic sites and/or axons and that this effect can be regulated by neuronal activity. Because the activity-dependent effect of endogenous Homer1a was also long-lasting, the axonal targeting of mGluR5 by this protein is likely to play an important role in synaptic plasticity.
Assuntos
Axônios/metabolismo , Proteínas de Transporte/metabolismo , Dendritos/metabolismo , Neurônios/metabolismo , Neuropeptídeos/metabolismo , Receptores de Glutamato Metabotrópico/metabolismo , Animais , Proteínas de Transporte/genética , Proteínas de Transporte/farmacologia , Células Cultivadas , Cerebelo/citologia , Cerebelo/metabolismo , Corpo Estriado/citologia , Corpo Estriado/metabolismo , Agonistas de Aminoácidos Excitatórios/farmacologia , Proteínas de Arcabouço Homer , Humanos , Ácido Caínico/metabolismo , Ácido Caínico/farmacologia , Camundongos , N-Metilaspartato/metabolismo , N-Metilaspartato/farmacologia , Neuritos/metabolismo , Plasticidade Neuronal/fisiologia , Neurônios/citologia , Neuropeptídeos/genética , Neuropeptídeos/farmacologia , Bloqueadores dos Canais de Potássio , Ligação Proteica/genética , Isoformas de Proteínas/metabolismo , Transporte Proteico/efeitos dos fármacos , Transporte Proteico/fisiologia , Receptor de Glutamato Metabotrópico 5 , Receptores de Glutamato Metabotrópico/genética , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Sinaptofisina/metabolismo , TransfecçãoRESUMO
Leaf tissues of two white bean (Phuscolus vulgaris L.) cultivars, one susceptible and one tolerant to white mould [Sclerotinia sclerotinrum (Lib.) de Bary], were treated for different times with oxalic acid. Tissues were prepared by both thin sectioning and freeze-fraeture techniques for electron microscopy. The plasma membrane of the resistant cultivar appeared more tolerant to damage induced by oxalic acid than that of the susceptible cultivar. At the same concentration of oxalic acid the plasma membrane and chloroplasts of the susceptible cultivar were affected more, and ruptured more quickly, than those of the tolerant one. In thin sections, the ruptured organelles were partially or completely disorganized. In replicas of freeze-fractured preparations of the plasma membrane, increased protrusions, wrinkles, breakages and ruptures were associated with increasing exposure to oxalic acid. Damage was more severe in the plasma membrane of the susceptible cultivar than in that of the tolerant one. Measurements of the conductivity of water bathing leaf discs of the two cultivars showed that the susceptible cultivar led to a higher conductivity than the resistant one, indicating that the injury and rupturing of the plasma membrane were closely related to membrane stability.
RESUMO
In 2001, soybean fields were surveyed to determine the incidence of viruses because soybean aphids (Aphis glycines Matsamura), known to transmit Soybean mosaic virus (SMV) (2), were found in Ontario. In addition, bean leaf beetle (Cerotoma trifurcata Forster) was found during 2000 to be contaminated with Bean pod mottle virus (BPMV), although soybean plants, on which the beetles were feeding, tested negative (3). In the current survey, young soybean leaves were selected at random in July and August from 20 plants per site at growth stages R4 to R5 (1) from 415 sites representing the entire soybean-producing area in Ontario. Samples were maintained under cool conditions until received at the laboratory, where they were promptly processed. A combined sub-sample was obtained from the 20 plants per site. The 415 sub-samples were tested for SMV, BPMV, Tobacco ringspot virus (TRSV), and Tobacco streak virus (TSV) using polyclonal antibody kits for double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) (Agdia Inc., Elkart, IN). The ELISA plates were read with a plate reader (MRX, Dynex Technologies Inc., Chantilly, VA), and results were analyzed using ELISA software (Leading Edge Research, Merrickville, Ontario) and compared positive and negative controls (Agdia). TRSV was detected in one sample from Essex County and another sample from Middlesex County. SMV, BPMV, and TSV were not found in commercial soybean fields. However, SMV and BPMV were found in samples originating from two soybean breeding nurseries, one in Essex County and one in Kent County. Seedlings of soybean cv. Williams 82 were inoculated in the greenhouse with sap from leaf samples that tested positive for BPMV. Leaves of plants that developed mosaic symptoms were retested using ELISA and confirmed to be positive for BPMV. SMV and TRSV have been found previously in commercial soybean fields in Ontario (4). To our knowledge, this is the first report of BPMV on soybean plants in Canada. References: (1) W. R. Fehr et al. Merr. Crop. Sci. 11:929, 1971. (2) J. H. Hill et al. Plant Dis. 85:561, 2001. (3) A. U. Tenuta. Crop Pest. 5 (11):8, 2000. (4) J. C. Tu. Can. J. Plant Sci. 66:491, 1986.
RESUMO
White and Scott (1973) described two forms of microsclerotia associated with corky root rot of tomato, one being formed in single cells of the outer root cortical cells and the other produced in culture from isolation of diseased roots and in degenerated root debris. By assuming that both forms were of fungal origin, they conducted an ultrastructural study using the microsclerotia produced in culture but not those formed in single cells. They demonstrated that the microsclerotia from culture consisted of hardened, interwoven hyphae of the fungus, Pyrenochaeta lycopersici. Since there have been doubts about the nature of the microsclerotia formed in single cells, an ultrastructural study was conducted. The results demonstrated clearly that the 'microsclerotia' formed in single cells of the root cortical cells were not composed of fungal mycelia, indeed these blackened cells or 'microsclerotia' were filled with numerous crystallines. There was no evidence of the presence of fungal hyphae in or around these cells. Both diseased and healthy, and young and old root cortex cells of many cultivars of tomato contained cells filled with crystallines. Therefore, it is clear that the 'microsclerotia' formed in single cells of the outer cortex described by White and Scott are not microsclerotia of the fungus, P. lycopersici.
Assuntos
Fungos/patogenicidade , Fungos/ultraestrutura , Raízes de Plantas/microbiologia , Solanum lycopersicum/microbiologia , Fungos/crescimento & desenvolvimento , Microscopia Eletrônica de Varredura , Doenças das Plantas/microbiologia , Raízes de Plantas/citologia , Raízes de Plantas/ultraestruturaRESUMO
Hydroponic culture has not replaced soil culture in greenhouse production of chrysanthemum (commonly known as 'mum'). This study examines cultural or pathological conditions that might have affected the conversion from soil to hydroponic production. Cultural factors investigated included hydroponic container size and shape and oxygenation of the nutrient solution. Disorders encountered during the studies included salt wicking during rooting of the cuttings and severe Pythium infection in the third and successive crops in a hydroponic system. Mums did not appear to respond to various shapes and sizes of containers and troughs in which they were grown. Also, increased oxygenation had little effect on pythium root rot and plant growth. Rooting of cuttings in a polyethylene covered hydroponic system reduced wilting, whereas salt wicking was severe without a plastic covering. Pythium disease was severe in the third and successive crops in the same hydroponic system. The disease could be overcome by raising the cuttings in a peat-based growing medium in perforated plastic cells and then transplanting the seedlings along with the peat moss cubes into a hydroponic system.
Assuntos
Chrysanthemum/crescimento & desenvolvimento , Hidroponia/métodos , Raízes de Plantas/microbiologia , Pythium/crescimento & desenvolvimento , Chrysanthemum/microbiologia , Ambiente Controlado , Oxigênio/metabolismo , Raízes de Plantas/crescimento & desenvolvimento , Sais/metabolismoRESUMO
The development of root rot and its severity were affected by numerous factors which through their interaction could distort results. In this study, a single factor, soil moisture was considered. Using Fusarium solani infested root rot soil we investigated the effect of three available soil moisture (ASM) levels (i.e. 100%, 70% and 25%) on seed rot, germination, plant growth and root rot severity of navy bean in the greenhouse. Percent germination differed strikingly averaging of 58.5, 89.5 and 87.0% respectively to ASM levels. Apparently, high soil moisture promoted seed rot and impeded seed germination. Root rot incidence and severity were examined two months later. Percent plant with root rot averaged 89.5, 89.0 and 69.8% while root rot severity was 3.01, 2.3 and 1.1 (on a 0-9 scale), respectively to ASM levels. Plant growth was moderate, good and poor with respect to ASM levels. It was apparent that the final plant growth was a sum of seed rot, root rot incidence, disease severity and soil moisture adequacy. However, seed rot appeared to be the largest contributing factor to final plant yield.
Assuntos
Fabaceae/microbiologia , Fabaceae/fisiologia , Fusarium/patogenicidade , Raízes de Plantas/microbiologia , Sementes/crescimento & desenvolvimento , Produtos Agrícolas , Fabaceae/crescimento & desenvolvimento , Fabaceae/metabolismo , Germinação , Doenças das Plantas/microbiologia , Sementes/microbiologia , Microbiologia do Solo , Água/metabolismoAssuntos
Adenilil Ciclases/análise , Fungos/enzimologia , Animais , Divisão Celular , Membrana Celular/enzimologia , Difosfatos , Fluoretos/farmacologia , Fungos/citologia , Fungos/efeitos dos fármacos , Histocitoquímica , Chumbo , Fígado/citologia , Fígado/enzimologia , Membranas/enzimologia , Camundongos , Mitocôndrias/enzimologia , Especificidade da Espécie , Esporos Fúngicos/enzimologia , Coloração e Rotulagem , Fatores de TempoAssuntos
Terapia por Acupuntura , Dermatopatias/terapia , Verrugas/terapia , Adolescente , Adulto , Idoso , Feminino , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Dermatopatias/imunologia , Verrugas/imunologiaRESUMO
By using adenyl cyclase as a marker enzyme, the relationship between the membrane envelope of the bacteroids of rhizobia and the plasma membrane of the host cell was demonstrated histochemically. Electron-dense deposits were found on the outer surface of the plasma membrane of the host cell and on the inner surface of the membrane envelopes of the bacteroids, but not in vacuole membranes, endoplasmic reticula, Golgi apparatus, and mitochondrial membranes. The results suggest that the membrane envelopes of the bacteroids are closely related to the host plasma membrane, and that entry of the bacteroids into the cytoplasm is in a manner similar to endocytosis.
Assuntos
Adenilil Ciclases/isolamento & purificação , Rhizobium/citologia , Membrana Celular/enzimologia , Parede Celular/enzimologia , Endocitose , Histocitoquímica , Microscopia Eletrônica , Modelos Biológicos , Organoides , Células Vegetais , Rhizobium/crescimento & desenvolvimentoRESUMO
PIP: This paper, published in Taiwan in June, 1986, studies the impact of demographic changes on social organization through stable population theory as applied to the USA. The stable population model indicates a constant age differential between death ratio and birth ratio maintained for a period of time in a given population. Since the 1950's, the population growth rate in the US has been 1.5%; social security tax revenue should increase 50% to maintain equilibrium. According to the US Census Bureau, in 1940, 11 people in 100 were age 65 or over; in 1980, 19 per 100; and 1 estimate places 32 in 100 over 65 in the year 2030. In 90 years the proportion of senior citizens will increase 3 times; social security taxes should consequently also increase 3 times. The stable population model would mean that social security tax should double its current rate to maintain equilibrium. However, based on the actual change in the population's age structure, social security tax should in fact increase at least 3 times. From 1940 to the present, social security tax revenue has already increased 3 times. Turning to education, in 1961, 4.39 million babies were born in the US. By the mid-1970's, births had slowed to an annual average of 3 million. The decrease in number of university students and posts available to Ph.Ds follows the birth rate change of 20 years earlier. Many graduate institutions will be influenced by this decrease in births. From another perspective, the birth rate decrease has also reduced the educational burden on society, and should provide more opportunities and resources. However, in the American educational system, research opportunities are determined by teaching positions which are dependent upon university enrollment figures. The US Census Bureau predicts that enrollment rates must double in order to compensate for the decrease in university age population.^ieng
Assuntos
Coeficiente de Natalidade , Demografia , Economia , Administração Financeira , Financiamento Governamental , Modelos Teóricos , Dinâmica Populacional , Crescimento Demográfico , População , Projetos de Pesquisa , Pesquisa , Mudança Social , Previdência Social , Seguridade Social , América , Países Desenvolvidos , Países em Desenvolvimento , Educação , Fertilidade , América do Norte , Ciências Sociais , Estatística como Assunto , Estudantes , Estados UnidosRESUMO
Pythium root rot caused by Pythium aphanidermatum is one of the most important diseases of greenhouse tomatoes. Hydroponic culture exacerbates the problem. Both nutrient film technique (NFT) and recirculating growing systems pose a challenge in the control of this disease, because the pathogen, especially the zoospores, can spread easily in the recirculating solution to the whole growing system. Fortunately, hydroponically grown plants are easier to manipulate than soil grown plants, proper manipulation of root environments can lead to excellent disease control. This paper reports the development of an effective integrated control measure for pythium root rot of tomato by integrating pH, bioagent, and ultra-violet irradiation in a specific manner. This integrated control consists of three operations: a) before transplanting, the UV system is connected to sterilize the recirculating solution using 100 mJcm-2; b) after transplanting, the nutrient solution is delivered at pH 5.0 regime for five weeks followed by adjusting pH to 5.8 to 6.2 regime for one week; and c) bacterial bioagent, such as Pseudomonas is introduced into the root zone at 100 mL per plant at 10(8) bacteria mL-1 or added to the nutrient solution to arrive at 10(6) bacteria mL-1 in the solution. This report also discusses the advantages and limitations of this measure in the control of pythium root rot.