RESUMO
Ultra-processed plant-based foods, such as plant-based burgers, have gained in popularity. Particularly in the out-of-home (OOH) environment, evidence regarding their nutritional profile and environmental sustainability is still evolving. Plant-based burgers available at selected OOH sites were randomly sampled in Amsterdam, Copenhagen, Lisbon and London. Plant-based burgers (patty, bread and condiment) (n 41) were lab analysed for their energy, macronutrients, amino acids and minerals content per 100 g and serving and were compared with reference values. For the plant-based burgers, the median values per 100 g were 234 kcal, 20·8 g carbohydrates, 3·5 g dietary fibre and 12·0 g fat, including 0·08 g TFS and 2·2 g SFA. Protein content was 8·9 g/100 g, with low protein quality according to amino acid composition. Median Na content was 389 mg/100 g, equivalent to 1 g salt. Compared with references, the median serving provided 31% of energy intake based on a 2000 kcal per day and contributed to carbohydrates (17-28%), dietary fibre (42%), protein (40%), total fat (48%), SFA (26%) and Na (54%). One serving provided 15-23% of the reference values for Ca, K and Mg, while higher contributions were found for Zn, Mn, P and Fe (30-67%). The ultra-processed plant-based burgers provide protein, dietary fibre and essential minerals and contain relatively high levels of energy, Na and total fats. The amino acid composition indicated low protein quality. The multifaceted nutritional profile of plant-based burgers highlights the need for manufacturers to implement improvements to better support healthy dietary habits, including reducing energy, Na and total fats.
Assuntos
Fibras na Dieta , Ingestão de Energia , Valor Nutritivo , Fibras na Dieta/análise , Humanos , Aminoácidos/análise , Proteínas Alimentares/análise , Nutrientes/análise , Manipulação de Alimentos/métodos , Minerais/análise , Gorduras na Dieta/análise , Carboidratos da Dieta/análise , Fast Foods/análise , Pão/análiseRESUMO
Through critical analysis of the law's traditional response to mental disorders in mental health and mental capacity law, it will be argued that a medicalised model of disability has been predominant, and still permeates jurisprudence in this area. It will be suggested that insights from the social model and relational understandings of rights can highlight the ways in which wider contextual and structural relations can impact upon the lived experience of mental impairment. Moreover, an understanding of the various dimensions of mental illness can help elucidate how the law can respond effectively to structural, institutional, and contextual factors in order to facilitate the enjoyment of purported rights and values. In light of this, it will further be argued that the lingering precedence given to a narrow, medical view of cognitive impairment is outmoded given the more richly textured understanding of cognitive impairments which has recently emerged. The United Nations Convention on the Rights of Persons with Disabilities (UNCRPD) has harnessed the insights from the social model of disability and the capabilities approach to justice, and will be presented as the legal articulation of such understandings. This article seeks to build upon these understandings of disability and social justice and argue for the need for a more responsive state and judiciary in addressing the concerns highlighted by the UNCRPD and embedding these into judicial discourse.
Assuntos
Pessoas com Deficiência/legislação & jurisprudência , Competência Mental/legislação & jurisprudência , Transtornos Mentais/psicologia , Direitos Humanos/legislação & jurisprudência , Humanos , Reino Unido , Nações UnidasRESUMO
Hereditary ovalocytes from a Mauritian subject are extremely rigid, with a shear elastic modulus about three times that of normal cells, and have increased resistance to invasion by the malaria parasite Plasmodium falciparum in vitro. The genetic anomaly resides in band 3; the protein gives rise to chymotryptic fragments with reduced mobility in SDS/polyacrylamide gel electrophoresis, but this is a result of anomalous binding of SDS and not a higher molecular weight. Analysis of the band 3 gene reveals (1) a point mutation (Lys56----Glu), which also occurs in a common asymptomatic band 3 (Memphis) variant and governs the electrophoretic properties, and (2) a deletion of nine amino acid residues, including a proline residue, encompassing the interface between the membrane-associated and the N-terminal cytoplasmic domains. The interaction of the mutant band 3 with ankyrin appears unperturbed. The fraction of band 3 capable of undergoing translation diffusion in the membrane is greatly reduced in the ovalocytes. Cells containing the asymptomatic band 3 variant were normal with respect to all the properties that we have studied. Possible mechanisms by which a structural change in band 3 at the membrane interface could regulate rigidity are examined.
Assuntos
Proteína 1 de Troca de Ânion do Eritrócito/fisiologia , Eliptocitose Hereditária/fisiopatologia , Membrana Eritrocítica/fisiologia , Adulto , Animais , Proteína 1 de Troca de Ânion do Eritrócito/química , Sequência de Bases , Elasticidade , Deformação Eritrocítica , Eritrócitos Anormais/parasitologia , Humanos , Masculino , Fluidez de Membrana , Dados de Sequência Molecular , Plasmodium falciparum/crescimento & desenvolvimentoRESUMO
Malarial parasites are primarily parasites of red cells and during infection ingest most of the haemoglobin within these cells, leaving the membrane as the only vestige of the original host cell. The red cell membrane thus plays a key role at all stages of infection with malarial parasites, and is modified in many ways during parasitisation, so that at least functionally it has little resemblance to the membrane from which it was originally derived. The highly specific and ordered process of parasite invasion of red cells is regulated at least in part by the uninfected red cell membrane. The red cell sialoglycoproteins or glycophorins of this membrane have been shown to play an important role in invasion by Plasmodium falciparum, the species of most importance to man because of it's high morbidity and mortality. Structurally, dynamic changes occur within the membrane during parasitisation, and a number of parasite proteins have been found to be associated within it, but changes on the surface of the infected cell have been more difficult to demonstrate. The membrane of the infected cell is important in the many metabolic processes of the parasite, as well as the critical cell-cell interactions that occur when cells containing mature parasites bind to endothelial cells (cytoadherence), bind to uninfected cells (rosetting), or interact with macrophages and other leucocytes. The recognition molecules on the red cell membrane involved in invasion, cytoadherence and rosetting appear to be quite distinct. Structural and functional changes have also been shown to occur in the membranes of uninfected red cells, both in infected patients, and in the presence of parasites in vitro. Interactions of the parasite P. falciparum with the red cell membrane hold the key to our understanding of the pathogenesis of severe falciparum infection in man.
Assuntos
Membrana Eritrocítica/fisiologia , Malária Falciparum/sangue , Plasmodium falciparum/crescimento & desenvolvimento , Animais , Transporte Biológico , Proteínas Sanguíneas/fisiologia , Adesão Celular , Humanos , Malária Falciparum/parasitologia , Lipídeos de Membrana/metabolismo , Proteínas de Membrana/fisiologia , Formação de RosetaRESUMO
Binding of the thiazolyl peptide antibiotic thiostrepton to the GTPase domain of 23S rRNA involves a few crucial nucleotides, notably A1067 (E. coli). Small RNA transcripts were prepared corresponding to the GTPase domain of the plastid 23S rRNA and the two forms of cytosolic 28S rRNAs found in the human malaria parasite Plasmodium falciparum, as well as the plastid form of rRNA of the AIDS-related pathogen Toxoplasma gondii. Binding affinities of the wild type and mutated RNA sequences were as predicted; the malarial plastid sequence had by far the highest affinity, whereas that from toxoplasma did not bind thiostrepton.
Assuntos
Plasmodium falciparum/genética , Plastídeos/metabolismo , RNA Ribossômico 23S/metabolismo , Tioestreptona/metabolismo , Animais , Sequência de Bases , Hipoxantina/metabolismo , Isoleucina/metabolismo , Testes de Sensibilidade Microbiana , Dados de Sequência Molecular , Conformação de Ácido Nucleico , Plasmodium falciparum/metabolismo , Plasmodium falciparum/ultraestrutura , Ligação Proteica , RNA Ribossômico 23S/químicaRESUMO
The shape and mechanical properties of human red cells were modified in several ways and the consequences for the efficiency of invasion by Plasmodium falciparum in culture were investigated. Inhibition of invasion by depletion of ATP was shown to be unrelated to cell shape or deformability changes. Treatment of cells with N-ethylmaleimide (NEM), which dissociates some 70% of the native spectrin tetramers into the dimer, grossly reduced deformation of the cells under shear and increased by a factor of two or more the shear elastic modulus, as measured by the micropipette aspiration technique. Cells thus treated were efficiently invaded by P. falciparum (ca. 75% of control). In a population of cells pretreated with chlorpromazine, parasites were found in stomatocytic cells which were highly undeformable under shear. There was also considerable invasion into cells from subjects with hereditary pyropoikilocytosis, and two types of elliptocytosis. Cells treated with wheat germ agglutinin showed a dose-dependent increase in rigidity; a fivefold increase in elastic modulus (with total loss of deformation under shear in our conditions) still permitted invasion at a level of 50% of the control. The results suggest that gross mechanical properties of the membrane per se, at least within any physiologically relevant range, are unlikely to be the primary determinant of malarial invasion; this may instead be linked to the freedom of membrane proteins to migrate in the course of entry of the parasite.
Assuntos
Membrana Eritrocítica/fisiologia , Eritrócitos/parasitologia , Plasmodium falciparum/fisiologia , 2,3-Difosfoglicerato , Trifosfato de Adenosina/metabolismo , Animais , Células Cultivadas , Clorpromazina/farmacologia , Ácidos Difosfoglicéricos/metabolismo , Deformação Eritrocítica/efeitos dos fármacos , Membrana Eritrocítica/efeitos dos fármacos , Membrana Eritrocítica/metabolismo , Eritrócitos/efeitos dos fármacos , Etilmaleimida/farmacologia , Humanos , Aglutininas do Germe de Trigo/farmacologiaRESUMO
Invasion of red cells by Plasmodium falciparum in vitro was inhibited by a range of extracellular ligands, none of which block the major receptors for merozoites. Most effective, in terms of dose response, were two monoclonal antibodies against the Wrb antigen on glycophorin A; wheat germ agglutinin which also binds to glycophorin, and an anti-band 3 monoclonal antibody, caused inhibition of invasion at higher levels of saturation, while concanavalin A, which binds to band 3, was without effect. All the ligands except concanavalin A, increased the rigidity of the host cell membrane. The anti-Wrb antibodies generated the highest dose response effect, but no correlation between invasion and shear elastic modulus of the membrane could be established. All ligands, with the exception of concanavalin A, caused a reduction in the translationally mobile fractions of band 3 and glycophorin, as revealed by fluorescence recovery after photobleaching (FRAP). Invasion diminished with loss of mobile band 3, engendered by bound wheat germ agglutinin or anti-band 3, falling precipitately when the mobile fraction fell below 40% of that in unperturbed membranes. Both anti-Wrb antibodies suppressed invasion completely at concentrations insufficient to affect significantly either membrane rigidity or intramembrane protein diffusion. A univalent anti-glycophorin A (Fab) fragment, the parent antibody of which was previously shown to inhibit invasion strongly, had only a modest effect on invasion and induced a correspondingly small change in the mobile fraction of band 3.(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
Eritrócitos/parasitologia , Plasmodium falciparum/patogenicidade , Animais , Reações Antígeno-Anticorpo , Membrana Eritrocítica/fisiologia , Glicoforinas/imunologia , Humanos , Técnicas In Vitro , Malária Falciparum/sangue , Fluidez de MembranaRESUMO
Elongation factor Tu (EF-Tu) is encoded by the tuf gene of the plastid organelle of the malaria parasite Plasmodium falciparum. A range of structurally unrelated inhibitors of this GTP-dependent translation factor was shown to have antimalarial activity in blood cultures. The most active was the cyclic thiazolyl peptide amythiamicin A with an IC50 = 0.01 microM. Demonstrable complexes were formed in vitro between a recombinant version of P. falciparum EF-Tu(pl) and inhibitors that bind to different sites on EF-Tu; these included the antibiotics kirromycin, GE2270A and enacyloxin IIa.
Assuntos
Antibacterianos/farmacologia , Plasmodium falciparum/efeitos dos fármacos , Plasmodium falciparum/metabolismo , Proteínas de Protozoários/biossíntese , Animais , Antibacterianos/metabolismo , Sítios de Ligação , Genes de Protozoários , Compostos Macrocíclicos , Fator Tu de Elongação de Peptídeos/antagonistas & inibidores , Fator Tu de Elongação de Peptídeos/metabolismo , Peptídeos Cíclicos/metabolismo , Peptídeos Cíclicos/farmacologia , Plasmodium falciparum/genética , Plastídeos/efeitos dos fármacos , Plastídeos/genética , Plastídeos/metabolismo , Polienos/metabolismo , Polienos/farmacologia , Piridonas/metabolismo , Piridonas/farmacologia , Proteínas Recombinantes/antagonistas & inibidores , Proteínas Recombinantes/metabolismo , Tiazóis/metabolismo , Tiazóis/farmacologiaRESUMO
Measurements were made of the photosynthetic gas exchange properties and water use efficiency of 19 species of mangrove in 9 estuaries with different salinity and climatic regimes in north eastern Australia and Papua New Guinea. Stomatal conductance and CO2 assimilation rates differed significantly between species at the same locality, with the salt-secreting species, Avicennia marina, consistently having the highest CO2 assimilation rates and stomatal conductances. Proportional changes in stomatal conductance and CO2 assimilation rate resulted in constant and similar intercellular CO2 concentrations for leaves exposed to photon flux densities above 800 µmol·m-2·s-1 in all species at a particular locality. In consequence, all species at the same locality had similar water use efficiencies. There were, however, significant differences in gas exchange properties between different localities. Stomatal conductance and CO2 assimilation rate both decreased with increasing salinity and with increasing leaf to air vapour pressure deficit (VPD). Furthermore, the slope of the relationship between assimilation rate and stomatal conductance increased, while intercellular CO2 concentration decreased, with increasing salinity and with decreasing ambient relative humidity. It is concluded from these results that the water use efficiency of mangroves increases with increasing environmental stress, in this case aridity, thereby maximising photosynthetic carbon fixation while minimising water loss.
RESUMO
Although animals in the genus Aplysia are solitary during most of the year, they form breeding aggregations during the reproductive season. The aggregations contain both mating and egg-laying animals and are associated with masses of egg cordons. The egg cordons are a source of pheromones that establish and maintain the aggregation, but none of the pheromonal factors have been chemically characterized. In these studies, specimens of Aplysia were induced to lay eggs, the egg cordons collected and eluted, and the eluates fractionated by C18 reversed-phase HPLC. Four peak fractions were bioassayed in a T-maze. All four increased the number of animals attracted to a nonlaying conspecific and were thus subjected to compositional and microsequence analysis. Each contained the same NH2-terminal peptide sequence. The full-length peptide ("attractin") was isolated from the albumen gland, a large exocrine organ that packages the eggs into a cordon. The complete 58-residue sequence was obtained, and it matched that predicted by an albumen gland cDNA. Mass spectrometry showed that attractin is 21 wt.% carbohydrate as the result of N-linked glycosylation. T-maze bioassays confirmed that the full-length peptide is attractive. Attractin is the first water-borne peptide pheromone characterized in molluscs, and the first in invertebrates.
Assuntos
Aplysia/fisiologia , Glicoproteínas/química , Glicoproteínas/fisiologia , Feromônios/química , Feromônios/fisiologia , Reprodução/fisiologia , Sequência de Aminoácidos , Animais , Feminino , Glicoproteínas/isolamento & purificação , Masculino , Dados de Sequência Molecular , Oviposição , Óvulo/fisiologia , Feromônios/isolamento & purificação , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos , Comportamento Sexual Animal , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por MatrizRESUMO
It is widely accepted that canonical Wnt (cWnt) signaling is required for the differentiation of osteoprogenitors into osteoblasts. Furthermore, tumor-derived secretion of the cWnt-antagonist Dickkopf-1 (Dkk-1) is known to cause bone destruction, inhibition of repair and metastasis in many bone malignancies, but its role in osteosarcoma (OS) is still under debate. In this study, we examined the role of Dkk-1in OS by engineering its overexpression in the osteochondral sarcoma line MOS-J. Consistent with the known role of Dkk-1 in osteoblast differentiation, Dkk-1 inhibited osteogenesis by the MOSJ cells themselves and also in surrounding tissue when implanted in vivo. Surprisingly, Dkk-1 also had unexpected effects on MOSJ cells in that it increased proliferation and resistance to metabolic stress in vitro and caused the formation of larger and more destructive tumors than controls upon orthotopic implantation. These effects were attributed in part to upregulation of the stress response enzyme and cancer stem cell marker aldehyde-dehydrogenase-1 (ALDH1). Direct inhibition of ALDH1 reduced viability under stressful culture conditions, whereas pharmacological inhibition of cWnt or overexpression of ALDH1 had a protective effect. Furthermore, we observed that ALDH1 was transcriptionally activated in a c-Jun-dependent manner through a pathway consisting of RhoA, MAP-kinase-kinase-4 and Jun N-terminal Kinase (JNK), indicating that noncanonical planar cell polarity-like Wnt signaling was the mechanism responsible. Together, our results therefore demonstrate that Dkk-1 enhances resistance of OS cells to stress by tipping the balance of Wnt signaling in favor of the non-canonical Jun-mediated Wnt pathways. In turn, this results in transcriptional activation of ALDH1 through Jun-responsive promoter elements. This is the first report linking Dkk-1 to tumor stress resistance, further supporting the targeting of Dkk-1 not only to prevent and treat osteolytic bone lesions but also to reduce numbers of stress-resistant tumor cells.
Assuntos
Neoplasias Ósseas/enzimologia , Peptídeos e Proteínas de Sinalização Intercelular/metabolismo , Isoenzimas/metabolismo , Osteossarcoma/enzimologia , Retinal Desidrogenase/metabolismo , Via de Sinalização Wnt , Família Aldeído Desidrogenase 1 , Animais , Sítios de Ligação , Neoplasias Ósseas/genética , Neoplasias Ósseas/patologia , Diferenciação Celular , Linhagem Celular Tumoral , Proliferação de Células , Sobrevivência Celular , Feminino , Regulação Enzimológica da Expressão Gênica , Regulação Neoplásica da Expressão Gênica , Humanos , Peptídeos e Proteínas de Sinalização Intercelular/genética , Isoenzimas/genética , Proteínas Quinases JNK Ativadas por Mitógeno/metabolismo , MAP Quinase Quinase 4/metabolismo , Camundongos , Camundongos Nus , Osteogênese , Osteólise , Osteossarcoma/genética , Osteossarcoma/patologia , Regiões Promotoras Genéticas , Proteínas Proto-Oncogênicas c-jun/metabolismo , Retinal Desidrogenase/genética , Estresse Fisiológico , Fatores de Tempo , Transcrição Gênica , Ativação Transcricional , Transfecção , Proteínas rho de Ligação ao GTP/metabolismo , Proteína rhoA de Ligação ao GTPRESUMO
The red cell membrane with its bilipid layer, integral membrane proteins (especially the GPs and band 3), and the red cell skeleton pose a formidable barrier for the malarial parasite to overcome during invasion. Invasion is an ordered and sequential process, indicating a highly complex and specific process involving numerous molecular interactions. For P. vivax and P. knowlesi infections the Duffy glycoprotein seems to be a specific requirement in invasion. For P. falciparum the GPs, and especially the N-acetyl neuraminic acid linked in an alpha 2-3 configuration on them, appear to act as specific ligands although some strains of P. falciparum may use alternate ligands for invasion. The parasite enters the red cells within an invagination continuous with the red cell bilipid layer, the parasitophorous vacuole membrane, and recent evidence would indicate that this membrane is largely of parasite origin. The numerous occasions in which the red cell needs to deform during invasion indicates that membrane deformability could be an important factor in determining invasion, but the dissociation of invasion and deformability as induced by a number of reagents would not support this contention. Instead it is suggested that reagents which modify invasion may be acting via alterations in red cell or parasite protein phosphorylation or dephosphorylation.
Assuntos
Membrana Eritrocítica/parasitologia , Plasmodium/fisiologia , Sequência de Aminoácidos , Animais , Proteína 1 de Troca de Ânion do Eritrócito/metabolismo , Adesão Celular , Suscetibilidade a Doenças , Sistema do Grupo Sanguíneo Duffy , Membrana Eritrocítica/química , Membrana Eritrocítica/fisiologia , Glicoforinas/fisiologia , Humanos , Ligantes , Fluidez de Membrana , Dados de Sequência Molecular , Ácido N-Acetilneuramínico , Fosforilação , Plasmodium/química , Plasmodium/crescimento & desenvolvimento , Processamento de Proteína Pós-Traducional , Proteínas de Protozoários/metabolismo , Ácidos Siálicos/fisiologia , Vacúolos/parasitologiaRESUMO
Ultraviolet (UV)-absorbing phenolic compounds that have been shown to be protective against the damaging: effects of UV-B radiation (Tevini et al., 1991, Photochem. Photobiol. 53, 329-333) were found in the leaf epidermis of tropical mangrove tree species. These UV-absorbing phenolic compounds and leaf succulence function as selective filters, removing short and energetic wavelengths. A field survey showed that the concentration of UV-absorbing compounds varied between species, between sites that would be experiencing similar levels of UV radiation, and between sun and shade leaves. Sun leaves have greater contents of phenolic compounds than shade leaves, and more saline sites have plants with greater levels in their leaves than less saline sites. In addition, increases in leaf nitrogen contents and quantum yields did not correlate with increasing levels of UV-absorbing compounds. It was concluded from these results that although UV-absorbing compounds form a UV-screen in the epidermis of mangrove leaves, UV radiation may not be the only factor influencing the accumulation of phenolic compounds, thus an experiment which altered the level of UV radiation incident on mangrove species was done. Near ambient levels of UVA and UV-B radiation resulted in a greater content of UV-absorbing compounds in Bruguiera parviflora (Roxb.) Wight and Arn. ex Griff., but did not result in increases in B. gymnorrhiza (L.) Lamk or Rhizophora apiculata Blume. Total chlorophyll contents were lower in R. apiculata when it was grown under near-ambient levels of UV radiation than when it was grown under conditions of UV-A and UV-B depletion, but no differences were observed between the UV radiation treatments in the other two species. There was no difference in leaf morphology, carotenoid/chlorophyll ratios, or chlorophyll a/b ratios between UV treatments, although these varied among species; B. parviflora had the highest carotenoid/chlorophyll ratio and R. apiculata had the lowest. Thus it is proposed that differences in species response tu UV radiation may be influenced by their ability to dissipate excess visible solar radiation.
RESUMO
The effect of rosette formation on the multiplication in vitro of Plasmodium falciparum was studied in order to establish whether rosetting acts as a major virulence factor in the pathogenesis of severe malaria by facilitating invasion of uninfected red cells. Invasion rates for rosetting (R+) and non-rosetting (R-) parasites selected from the same clone, PA1, of P. falciparum were similar over a range of starting parasite concentrations when assayed in both static cultures and conditions of shear stress comparable with microvascular flow. However, incubation of both R+ and R- parasites under simulated conditions of flow led to decreased invasion and fewer multiply-infected red cells as we have previously observed. Studies using fluorescently labelled red cells or reticulocytes demonstrated that rosetting did not alter the rates of invasion or target merozoites into the uninfected cells comprising a rosette. Preferential invasion of reticulocytes occurred regardless of rosetting or conditions of flow. Although the role of rosetting in the pathogenesis of malaria might relate to microvascular obstruction or perhaps the restriction of phagocytosis, our data suggest that rosetting does not play a role in the invasion or targeting of parasites into uninfected cells, eliminating this mechanism to explain the association of virulence with the rosetting parasite phenotype.
Assuntos
Plasmodium falciparum/crescimento & desenvolvimento , Animais , Linhagem Celular , Plasmodium falciparum/imunologia , Plasmodium falciparum/patogenicidade , Reticulócitos/parasitologia , Formação de RosetaRESUMO
This review assembles data from three bodies of literature (bacterial genetics, plastid biogenesis and parasitology) that seldom have much direct cross-talk. After overcoming terminological complications to sort out microbial nifS from sufS genes, we connect a bacterial operon, recently found to be involved in iron metabolism, the formation of [Fe-S] clusters and oxidative stress to a potentially important gene (sufB) carried on the degenerate plastid genome of malaria and related parasites.
Assuntos
Proteínas de Bactérias/genética , Proteínas de Escherichia coli , Genes de Protozoários , Plasmodium/genética , Plastídeos/genética , Terminologia como Assunto , Sequência de Aminoácidos , Animais , Proteínas de Bactérias/metabolismo , Genes Bacterianos , Genes de Plantas , Dados de Sequência Molecular , Óperon , Plasmodium/metabolismo , Proteínas de Protozoários/genética , Proteínas de Protozoários/metabolismoRESUMO
In this report, we analyze the photosynthetic capacity and performance of leaves under field conditions with a case study based on the mangroves Bruguiera parviflora and B. gymnorrhiza. Using a tower through a closed canopy at a field sight in North Queensland and portable infra-red gas analyzers, a large data set was collected over a period of 11 days early in the growing season. The set was used to analyze the relationship between net photosynthesis (Pnet) and light, leaf temperature, stomatal conductance and intracellular CO2 (Ci).There are three objectives of this report: (1) to determine photosynthetic potential as indicated by the in situ responses of Pnet to light and stomatal conductance, (2) to determine the extent to which photosynthetic performance may be reduced from that potential, and (3) to explore the basis for and physiological significance of the reduction.The results indicate that even under harsh tropical conditions, the mangrove photosynthetic machinery is capable of operating efficiently at low light and with maximal rates of more than 15 µmol CO2 m(-2) s(-1). Though stomata were more often limiting than light, in any single measurement the average reduction of Pnet from the maximum value predicted by light or conductance responses was 35%. Analysis of single leaf light and CO2 responses indicated that photosynthetic performance was under direct photosynthetic, or non-stomatal, control at all light and conductance levels. Capacity was adjustable rapidly from a maximum value to essentially nil such that Ci varied inversely with Pnet from ca. 150 µL L(-1) at the highest rates of CO2 exchange to ambient at the lowest.
RESUMO
Merozoites of the human malaria parasite, Plasmodium falciparum, when treated with cytochalasin B, will attach irreversibly to red cells with formation of a vestigial internal (parasitophorous) vacuole, but they are inhibited from moving into the cell. The existence of an actin-based motile mechanism is implied. Immunoblotting, peptide mapping and the DNase inhibition assay have been used to show that the merozoite contains actin. It makes up an estimated 0.3% of the total parasite protein and is partitioned in the ratio of about 1:2 between the cytosolic and particulate protein fractions. In the former it is unpolymerised and in the latter filamentous. Most of the anti-actin-reactive protein in the soluble fraction and about 20% of that in the pellet has an apparent molecular weight of 55,000 and reacts with an anti-ubiquitin antibody; it is thus evidently ubiquitinyl actin, or arthrin, which has so far been detected only in insect flight muscle.
Assuntos
Actinas/análise , Plasmodium falciparum/química , Proteínas de Protozoários/análise , Actinas/química , Animais , Bioensaio , Desoxirribonuclease I/antagonistas & inibidores , Humanos , Peso Molecular , Plasmodium falciparum/crescimento & desenvolvimento , Ubiquitinas/análiseRESUMO
Sialic acid on the red cell surface plays a major role in invasion by the malaria parasite Plasmodium falciparum. The NeuAc(alpha 2,3) Gal motif on the O-linked tetrasaccharides of the red cell glycophorins is a recognition site for the parasite erythrocyte-binding antigen (EBA-175). Consequently, the interaction of P. falciparum and the red cell might share homology with that of the influenza virus. The cellular interactions of P. falciparum were examined for their sensitivity to 4-guanidino-2,3-didehydro-D-N-acetyl neuraminic acid (4-guanidino Neu5Ac2en), a potent inhibitor of influenza virus sialidase. Parasite invasion and subsequent development was unaffected by the sialidase inhibitor. The inhibitor did not affect rosette formation of parasite-infected erythrocytes with uninfected cells nor their cytoadherence to C32 melanoma cells. Furthermore, we were unable to confirm the presence of a previously reported parasite sialidase using sensitive fluorometric or haemagglutination assays, neither was any malarial trans-sialidase identified. We conclude that P. falciparum possesses neither sialidase nor trans-sialidase activity and that an inhibitor of influenza virus sialidase has no effect on important cellular interactions of this parasite.