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1.
Front Neurol ; 15: 1384551, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38751886

RESUMO

Introduction and objective: Autologous hematopoietic stem cell transplantation (aHSCT) is a promising treatment option for persons with multiple sclerosis (pwMS). Patients undergoing aHSCT face unique challenges in all aspects of life. In this study, we explored the lived experiences of pwMS undergoing aHSCT. Methods: Semi-structured interviews of 12 pwMS treated with aHSCT were conducted using a maximum variation sampling strategy. Interviews were transcribed verbatim and analyzed thematically using inductive and deductive categories. Results: Three major themes were identified: (1) preparing for aHSCT, (2) experiencing the procedure, and (3) post-treatment time. A difficult decision-making process, organizational effort, and funding difficulties characterized the preparation for transplantation. AHSCT was seen as a life-changing event accompanied by both psychological and physical stress, with an associated feeling of regaining control. The transplantation had a lasting positive effect on the lives of the interviewed pwMS. However, the early post-treatment time was characterized by successes and failures alike. Particularly the independently organized medical aftercare was perceived as challenging. Retrospective revaluation has led most pwMS to wish for earlier information provision about the treatment option of aHSCT during their treatment history. Conclusion: AHSCT had a clear impact on patients' physical and psycho-social health, influencing their perception of life and its quality. Assessing and attending to unmet needs of patients before, during, and after transplantation may positively influence their experience of aHSCT.

2.
Vaccines (Basel) ; 12(4)2024 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-38675764

RESUMO

Vaccine development against group A Streptococcus (GAS) has gained traction in the last decade, fuelled by recognition of the significant worldwide burden of the disease. Several vaccine candidates are currently being evaluated in preclinical and early clinical studies. Here, we investigate two conjugate vaccine candidates that have shown promise in mouse models of infection. Two antigens, the J8 peptide from the conserved C-terminal end of the M protein, and the group A carbohydrate lacking N-acetylglucosamine side chain (ΔGAC) were each conjugated to arginine deiminase (ADI), an anchorless surface protein from GAS. Both conjugate vaccine candidates combined with alum adjuvant were tested in a non-human primate (NHP) model of pharyngeal infection. High antibody titres were detected against J8 and ADI antigens, while high background antibody titres in NHP sera hindered accurate quantification of ΔGAC-specific antibodies. The severity of pharyngitis and tonsillitis signs, as well as the level of GAS colonisation, showed no significant differences in NHPs immunised with either conjugate vaccine candidate compared to NHPs in the negative control group.

3.
Med ; 2024 Mar 22.
Artigo em Inglês | MEDLINE | ID: mdl-38554710

RESUMO

BACKGROUND: Progressive multiple sclerosis (MS) is characterized by compartmentalized smoldering neuroinflammation caused by the proliferation of immune cells residing in the central nervous system (CNS), including B cells. Although inflammatory activity can be prevented by immunomodulatory therapies during early disease, such therapies typically fail to halt disease progression. CD19 chimeric antigen receptor (CAR)-T cell therapies have revolutionized the field of hematologic malignancies. Although generally considered efficacious, serious adverse events associated with CAR-T cell therapies such as immune effector cell-associated neurotoxicity syndrome (ICANS) have been observed. Successful use of CD19 CAR-T cells in rheumatic diseases like systemic lupus erythematosus and neuroimmunological diseases like myasthenia gravis have recently been observed, suggesting possible application in other autoimmune diseases. METHODS: Here, we report the first individual treatment with a fully human CD19 CAR-T cell therapy (KYV-101) in two patients with progressive MS. FINDINGS: CD19 CAR-T cell administration resulted in acceptable safety profiles for both patients. No ICANS was observed despite detection of CD19 CAR-T cells in the cerebrospinal fluid. In case 1, intrathecal antibody production in the cerebrospinal fluid decreased notably after CAR-T cell infusion and was sustained through day 64. CONCLUSIONS: CD19 CAR-T cell administration in progressive MS resulted in an acceptable safety profile. CAR-T cell presence and expansion were observed in the cerebrospinal fluid without clinical signs of neurotoxicity, which, along with intrathecal antibody reduction, indicates expansion-dependent effects of CAR-T cells on CD19+ target cells in the CNS. Larger clinical studies assessing CD19 CAR-T cells in MS are warranted. FUNDING: Both individual treatments as well the generated data were not based on external funding.

4.
Bone Marrow Transplant ; 59(4): 550-557, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38321269

RESUMO

Allogeneic hematopoietic stem cell transplantation (alloHSCT) remains the only curative treatment for myelofibrosis (MF). Relapse occurs in 10-30% and remains a major factor for dismal outcomes. Previous work suggested that graft-versus-host disease (GVHD) might be associated with risk of relapse. This study included 341 patients undergoing their first (n = 308) or second (n = 33) alloHSCT. Anti-T-lymphocyte or antithymocyte globulin was used for GVHD prophylaxis in almost all patients. Median time to neutrophile and platelet engraftment was 13 days and 19 days, respectively. The cumulative incidence of acute GVHD grade II-IV was 41% (median, 31 days; range, 7-112). Grade III-IV acute GVHD was observed in 22%. The cumulative incidence of chronic GVHD was 61%. Liver was affected in 23% of acute GVHD cases and 46% of chronic GVHD cases. Severe acute GVHD was associated with high non-relapse mortality. The development of acute GVHD grade II and moderate GVHD was an independent factor for reduced risk for relapse after transplantation without increased risk for non-relapse mortality, while especially acute GVHD grade IV was associated with high non-relapse mortality. Last, we identified that ongoing response to ruxolitinib, accelerated-phase MF at time of transplantation and splenectomy prior to transplantation were independent predictors for relapse.


Assuntos
Doença Enxerto-Hospedeiro , Transplante de Células-Tronco Hematopoéticas , Mielofibrose Primária , Humanos , Mielofibrose Primária/complicações , Recidiva Local de Neoplasia/tratamento farmacológico , Transplante de Células-Tronco Hematopoéticas/efeitos adversos , Doença Enxerto-Hospedeiro/etiologia , Soro Antilinfocitário/uso terapêutico
5.
Mult Scler Relat Disord ; 82: 105414, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38176284

RESUMO

BACKGROUND: Autologous hematopoietic stem cell transplantation (aHSCT) exhibits promising results for multiple sclerosis (MS) in the short term. We investigated the long-term outcome differences in disease progression and cognitive impairment after aHSCT and alemtuzumab treatment. METHODS: 20 patients receiving aHSCT and 21 patients treated with alemtuzumab between 2007 and 2020 were included in this monocentric observational cohort study. The primary objective was to compare the outcome of both groups with regards to achieving No Evidence of Disease Activity (NEDA-3), defined by the absence of relapses, EDSS progression, and MRI activity. Secondary endpoints in the study included the assessment of neurocognitive functioning, quality of life (QoL), Multiple Sclerosis Functional Composite (MSFC), and EDSS improvement. RESULTS: Baseline characteristics between both groups were comparable, except for a longer disease duration in the alemtuzumab group of 11.3 years compared to 5.4 years in aHSCT-treated patients (p = 0.002) and a longer mean follow-up time in the aHSCT cohort of 9.0 (range 2.8-15.7) years compared to 5.9 years (range 0.9-9.2) in alemtuzumab patients. NEDA-3 was more frequently observed in the aHSCT group with 75.0 % and 55.0 % at five and 10 years, respectively, than in the alemtuzumab group with only 40.0 % at five years (p = 0.012). Relapse free survival was higher in the aHSCT group (p < 0.001). None of the aHSCT-treated patients showed new T2-lesions six months after therapy initiation until the end of the observational period in contrast to 35.0 % of the alemtuzumab-treated patients showing new T2-lesions (95 %CI 14.2-98.9, p = 0.002). aHSCT-treated patients showed significantly improved cognitive performance in five out of 12 cognitive tests whereas alemtuzumab treated patients deteriorated in four out of 12 tests. Quality of life remained on a constant level for up to 10 years in patients receiving aHSCT with improved scores for the subscale fatigue (p = 0.013). CONCLUSION: aHSCT seems to be superior to alemtuzumab in maintaining long-term NEDA-3 status, improving cognition and stabilizing quality of life for up to 10 years.


Assuntos
Transplante de Células-Tronco Hematopoéticas , Esclerose Múltipla Recidivante-Remitente , Esclerose Múltipla , Humanos , Esclerose Múltipla/tratamento farmacológico , Alemtuzumab/efeitos adversos , Qualidade de Vida , Resultado do Tratamento , Transplante de Células-Tronco Hematopoéticas/métodos , Cognição , Esclerose Múltipla Recidivante-Remitente/tratamento farmacológico
6.
Nano Lett ; 23(20): 9212-9218, 2023 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-37788809

RESUMO

Optically dark excitons determine a wide range of properties of photoexcited semiconductors yet are hard to access via conventional time-resolved spectroscopies. Here, we develop a time-resolved ultrafast photocurrent technique (trPC) to probe the formation dynamics of optically dark excitons. The nonlinear nature of the trPC makes it particularly sensitive to the formation of excitons occurring at the femtosecond time scale after the excitation. As a proof of principle, we extract the interlayer exciton formation time of 0.4 ps at 160 µJ/cm2 fluence in a MoS2/MoSe2 heterostructure and show that this time decreases with fluence. In addition, our approach provides access to the dynamics of carriers and their interlayer transport. Overall, our work establishes trPC as a technique to study dark excitons in various systems that are hard to probe by other approaches.

7.
J Clin Med ; 12(2)2023 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-36675496

RESUMO

Motion capture analysis (MCA) has the advantage of providing a static and dynamic leg axis analysis without radiation. Nevertheless, there is a lack of evidence regarding the accuracy of this technique. To test whether mechanical femorotibial axis angle (MAA) measurement recorded with a non-invasive MCA system is equal to the gold standard static long-standing full-leg radiographs (LSX) and if the degree of malalignment or other parameters (BMI, body mass, height, age) influence the accuracy, a total of 102 consecutive patients were examined using LSX and MCA. Static as well as all gait motion phases at 3 km/h were analyzed regarding the difference between the two angles. There was no statistical difference for MAA between LSX (MAArad) and MCA (MAAstat) (p = 0.091). There was a strong correlation (rs = 0.858, p < 0.001) between the two methods. The highest accuracy was detected for values of standing MCA. Also, the gait MCA values showed strong correlation with LSX but weaker correlation compared to standing MCA (initial swing rs = 0.549; terminal stance rs = 0.815; p < 0.001). BMI, body mass, and height did not influence the accuracy of MCA. MCA enables frontal alignment analysis with high accuracy and without the side effect of radiation.

8.
Immunol Cell Biol ; 99(10): 1040-1052, 2021 11.
Artigo em Inglês | MEDLINE | ID: mdl-34462965

RESUMO

Group A Streptococcus (GAS) is a Gram-positive bacterial pathogen that causes an array of infectious diseases in humans. Accumulating clinical evidence suggests that proinflammatory interleukin (IL)-1ß signaling plays an important role in GAS disease progression. The host regulates the production and secretion of IL-1ß via the cytosolic inflammasome pathway. Activation of the NLR family pyrin domain-containing 3 (NLRP3) inflammasome complex requires two signals: a priming signal that stimulates increased transcription of genes encoding the components of the inflammasome pathway, and an activating signal that induces assembly of the inflammasome complex. Here we show that GAS-derived lipoteichoic acid can provide a priming signal for NLRP3 inflammasome activation. As only few GAS-derived proteins have been associated with inflammasome-dependent IL-1ß signaling, we investigated novel candidates that might play a role in activating the inflammasome pathway by infecting mouse bone marrow-derived macrophages and human THP-1 macrophage-like cells with a panel of isogenic GAS mutant strains. We found that the cytolysins streptolysin O (SLO) and streptolysin S are the main drivers of IL-1ß release in proliferating logarithmic phase GAS. Using a mutant form of recombinant SLO, we confirmed that bacterial pore formation on host cell membranes is a key mechanism required for inflammasome activation. Our results suggest that streptolysins are major determinants of GAS-induced inflammation and present an attractive target for therapeutic intervention.


Assuntos
Inflamassomos , Infecções Estreptocócicas , Animais , Interleucina-1beta , Macrófagos , Camundongos , Proteína 3 que Contém Domínio de Pirina da Família NLR , Streptococcus pyogenes , Estreptolisinas
9.
Cell Microbiol ; 23(9): e13373, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34155776

RESUMO

Group A Streptococcus (GAS) is a Gram-positive bacterial pathogen that causes significant morbidity and mortality worldwide. Recent clinical evidence suggests that the inflammatory marker interleukin-1ß (IL-1ß) plays an important role in GAS disease progression, and presents a potential target for therapeutic intervention. Interaction with GAS activates the host inflammasome pathway to stimulate production and secretion of IL-1ß, but GAS can also stimulate IL-1ß production in an inflammasome-independent manner. This review highlights progress that has been made in understanding the importance of host cell inflammasomes and IL-1 signalling in GAS disease, and explores challenges and unsolved problems in this host-pathogen interaction. TAKE AWAY: Inflammasome signalling during GAS infection is an emerging field of research. GAS modulates the NLRP3 inflammasome pathway through multiple mechanisms. SpeB contributes to IL-1ß production independently of the inflammasome pathway. IL-1ß signalling can be host-protective, but also drive severe GAS disease.


Assuntos
Inflamassomos , Interleucina-1beta , Infecções Estreptocócicas , Humanos , Proteína 3 que Contém Domínio de Pirina da Família NLR , Transdução de Sinais , Streptococcus pyogenes
11.
Nat Commun ; 11(1): 5018, 2020 10 06.
Artigo em Inglês | MEDLINE | ID: mdl-33024089

RESUMO

The re-emergence of scarlet fever poses a new global public health threat. The capacity of North-East Asian serotype M12 (emm12) Streptococcus pyogenes (group A Streptococcus, GAS) to cause scarlet fever has been linked epidemiologically to the presence of novel prophages, including prophage ΦHKU.vir encoding the secreted superantigens SSA and SpeC and the DNase Spd1. Here, we report the molecular characterization of ΦHKU.vir-encoded exotoxins. We demonstrate that streptolysin O (SLO)-induced glutathione efflux from host cellular stores is a previously unappreciated GAS virulence mechanism that promotes SSA release and activity, representing the first description of a thiol-activated bacterial superantigen. Spd1 is required for resistance to neutrophil killing. Investigating single, double and triple isogenic knockout mutants of the ΦHKU.vir-encoded exotoxins, we find that SpeC and Spd1 act synergistically to facilitate nasopharyngeal colonization in a mouse model. These results offer insight into the pathogenesis of scarlet fever-causing GAS mediated by prophage ΦHKU.vir exotoxins.


Assuntos
Exotoxinas/metabolismo , Prófagos/genética , Streptococcus pyogenes/patogenicidade , Streptococcus pyogenes/virologia , Animais , Proteínas de Bactérias/farmacologia , Linhagem Celular , Eritrócitos/efeitos dos fármacos , Exotoxinas/genética , Feminino , Glutationa/metabolismo , Humanos , Masculino , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Mutação , Faringe/citologia , Escarlatina/epidemiologia , Escarlatina/microbiologia , Streptococcus pyogenes/genética , Estreptolisinas/farmacologia , Superantígenos/genética , Superantígenos/metabolismo
13.
mBio ; 11(2)2020 03 10.
Artigo em Inglês | MEDLINE | ID: mdl-32156809

RESUMO

Recent global advocacy efforts have highlighted the importance of development of a vaccine against group A Streptococcus (GAS). Combo5 is a non-M protein-based vaccine that provides protection against GAS skin infection in mice and reduces the severity of pharyngitis in nonhuman primates. However, Combo5 with the addition of aluminum hydroxide (alum) as an adjuvant failed to protect against invasive GAS infection of mice. Here, we show that formulation of Combo5 with adjuvants containing saponin QS21 significantly improves protective efficacy, even though all 7 adjuvants tested generated high antigen-specific IgG antibody titers, including alum. Detailed characterization of Combo5 formulated with SMQ adjuvant, a squalene-in-water emulsion containing a TLR4 agonist and QS21, showed significant differences from the results obtained with alum in IgG subclasses generated following immunization, with an absence of GAS opsonizing antibodies. SMQ, but not alum, generated strong interleukin-6 (IL-6), gamma interferon (IFN-γ), and tumor necrosis alpha (TNF-α) responses. This work highlights the importance of adjuvant selection for non-M protein-based GAS vaccines to optimize immune responses and protective efficacy.IMPORTANCE Availability of a group A Streptococcus vaccine remains an unmet public health need. Here, we tested different adjuvant formulations to improve the protective efficacy of non-M protein vaccine Combo5 in an invasive disease model. We show that novel adjuvants can dramatically shape the type of immune response developed following immunization with Combo5 and significantly improve protection. In addition, protection afforded by Combo5 is not mediated by opsonizing antibodies, believed to be the main correlate of protection against GAS infections. Overall, this report highlights the importance of adjuvant selection in raising protective immune responses against GAS invasive infection. Adjuvants that can provide a more balanced Th1/Th2-type response may be required to optimize protection of GAS vaccines, particularly those based on non-M protein antigens.


Assuntos
Imunidade Celular , Infecções Estreptocócicas/imunologia , Infecções Estreptocócicas/prevenção & controle , Vacinas Estreptocócicas/imunologia , Células Th1/imunologia , Adjuvantes Imunológicos/administração & dosagem , Hidróxido de Alumínio/administração & dosagem , Animais , Anticorpos Antibacterianos/imunologia , Citocinas/imunologia , Feminino , Imunização , Imunoglobulina G/imunologia , Interferon gama/imunologia , Masculino , Camundongos , Proteínas Opsonizantes/imunologia , Vacinas Estreptocócicas/administração & dosagem
14.
Clin Cancer Res ; 26(7): 1700-1711, 2020 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-31831562

RESUMO

PURPOSE: PI3K signaling is a common feature of B-cell neoplasms, including chronic lymphocytic leukemia (CLL) and diffuse large B-cell lymphoma (DLBCL), and PI3K inhibitors have been introduced into the clinic. However, there remains a clear need to develop new strategies to target PI3K signaling. PI3K activity is countered by Src homology domain 2-containing inositol-5'-phosphatase 1 (SHIP1) and, here, we have characterized the activity of a novel SHIP1 activator, AQX-435, in preclinical models of B-cell malignancies. EXPERIMENTAL DESIGN: In vitro activity of AQX-435 was evaluated using primary CLL cells and DLBCL-derived cell lines. In vivo activity of AQX-435, alone or in combination with the Bruton's tyrosine kinase (BTK) inhibitor ibrutinib, was assessed using DLBCL cell line and patient-derived xenograft models. RESULTS: Pharmacologic activation of SHIP1 using AQX-435 was sufficient to inhibit anti-IgM-induced PI3K-mediated signaling, including induction of AKT phosphorylation and MYC expression, without effects on upstream SYK phosphorylation. AQX-435 also cooperated with the BTK inhibitor ibrutinib to enhance inhibition of anti-IgM-induced AKT phosphorylation. AQX-435 induced caspase-dependent apoptosis of CLL cells preferentially as compared with normal B cells, and overcame in vitro survival-promoting effects of microenvironmental stimuli. Finally, AQX-435 reduced AKT phosphorylation and growth of DLBCL in vivo and cooperated with ibrutinib for tumor growth inhibition. CONCLUSIONS: Our results using AQX-435 demonstrate that SHIP1 activation may be an effective novel therapeutic strategy for treatment of B-cell neoplasms, alone or in combination with ibrutinib.


Assuntos
Antineoplásicos/farmacologia , Ativadores de Enzimas/farmacologia , Leucemia Linfocítica Crônica de Células B/tratamento farmacológico , Linfoma Difuso de Grandes Células B/tratamento farmacológico , Fosfatidilinositol 3-Quinases/metabolismo , Fosfatidilinositol-3,4,5-Trifosfato 5-Fosfatases/metabolismo , Sesquiterpenos/farmacologia , Animais , Apoptose/efeitos dos fármacos , Linhagem Celular Tumoral , Feminino , Humanos , Leucemia Linfocítica Crônica de Células B/metabolismo , Leucemia Linfocítica Crônica de Células B/patologia , Linfoma Difuso de Grandes Células B/metabolismo , Linfoma Difuso de Grandes Células B/patologia , Camundongos , Camundongos Endogâmicos NOD , Fosfatidilinositol 3-Quinases/química , Fosfatidilinositol-3,4,5-Trifosfato 5-Fosfatases/genética , Transdução de Sinais , Ensaios Antitumorais Modelo de Xenoenxerto
15.
Clin Infect Dis ; 69(7): 1232-1234, 2019 09 13.
Artigo em Inglês | MEDLINE | ID: mdl-30721938

RESUMO

Sentinel hospital surveillance was instituted in Australia to detect the presence of pandemic group A Streptococcus strains causing scarlet fever. Genomic and phylogenetic analyses indicated the presence of an Australian GAS emm12 scarlet fever isolate related to United Kingdom outbreak strains. National surveillance to monitor this pandemic is recommended.


Assuntos
Escarlatina/epidemiologia , Escarlatina/microbiologia , Streptococcus pyogenes/classificação , Streptococcus pyogenes/genética , Austrália/epidemiologia , Biologia Computacional/métodos , Surtos de Doenças , Genoma Bacteriano , Genômica/métodos , Humanos , Filogenia , Vigilância da População , Escarlatina/diagnóstico
16.
Nat Commun ; 9(1): 5375, 2018 12 18.
Artigo em Inglês | MEDLINE | ID: mdl-30560907

RESUMO

During development, it is unclear if lineage-fated cells derive from multilineage-primed progenitors and whether active mechanisms operate to restrict cell fate. Here we investigate how mesoderm specifies into blood-fated cells. We document temporally restricted co-expression of blood (Scl/Tal1), cardiac (Mesp1) and paraxial (Tbx6) lineage-affiliated transcription factors in single cells, at the onset of blood specification, supporting the existence of common progenitors. At the same time-restricted stage, absence of SCL results in expansion of cardiac/paraxial cell populations and increased cardiac/paraxial gene expression, suggesting active suppression of alternative fates. Indeed, SCL normally activates expression of co-repressor ETO2 and Polycomb-PRC1 subunits (RYBP, PCGF5) and maintains levels of Polycomb-associated histone marks (H2AK119ub/H3K27me3). Genome-wide analyses reveal ETO2 and RYBP co-occupy most SCL target genes, including cardiac/paraxial loci. Reduction of Eto2 or Rybp expression mimics Scl-null cardiac phenotype. Therefore, SCL-mediated transcriptional repression prevents mis-specification of blood-fated cells, establishing active repression as central to fate determination processes.


Assuntos
Linhagem da Célula/fisiologia , Regulação da Expressão Gênica no Desenvolvimento/fisiologia , Proteínas Nucleares/metabolismo , Proteínas Repressoras/metabolismo , Proteína 1 de Leucemia Linfocítica Aguda de Células T/metabolismo , Fatores de Transcrição/metabolismo , Animais , Diferenciação Celular/fisiologia , Linhagem Celular , Separação Celular/métodos , Embrião de Mamíferos , Citometria de Fluxo/métodos , Código das Histonas/fisiologia , Mesoderma/citologia , Mesoderma/fisiologia , Camundongos , Células-Tronco Embrionárias Murinas , Proteínas Nucleares/genética , Complexo Repressor Polycomb 1/metabolismo , Proteínas do Grupo Polycomb/metabolismo , RNA Interferente Pequeno/metabolismo , Proteínas Repressoras/genética , Proteína 1 de Leucemia Linfocítica Aguda de Células T/genética , Fatores de Transcrição/genética
17.
Ecol Evol ; 8(13): 6779-6787, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30038774

RESUMO

The characteristic vegetation structure of arid savannas with a dominant layer of perennial grass is maintained by the putative competitive superiority of the C4 grasses. When this competitive balance is disturbed by weakening the grasses or favoring the recruitment of other species, trees, shrubs, single grass, or forb species can increase and initiate sudden dominance shifts. Such shifts involving woody species, often termed "shrub encroachment", or the mass spreading of so-called increaser species have been extensively researched, but studies on similar processes without obvious preceding disturbance are rare. In Namibia, the native herbaceous legume Crotalaria podocarpa has recently encroached parts of the escarpment region, seriously affecting the productivity of local fodder grasses. Here, we studied the interaction between seedlings of the legume and the dominant local fodder grass (Stipagrostis ciliata). We used a pot experiment to test seedling survival and to investigate the growth of Crotalaria in competition with Stipagrostis. Additional field observations were conducted to quantify the interactive effect. We found germination and growth of the legume seedlings to be facilitated by inactive (dead or dormant) grass tussocks and unhindered by active ones. Seedling survival was three times higher in inactive tussocks and Crotalaria grew taller. In the field, high densities of the legume had a clear negative effect on productivity of the grass. The C4 grass was unable to limit the recruitment and spread of the legume, and Crotalaria did outcompete the putative more competitive grass. Hence, the legume is able to spread and establish itself in large numbers and initiate a dominance shift in savannas, similar to shrub encroachment.

18.
J Clin Endocrinol Metab ; 91(5): 1950-5, 2006 May.
Artigo em Inglês | MEDLINE | ID: mdl-16478818

RESUMO

CONTEXT: ATP-sensitive potassium (K(ATP)) channels couple the metabolic state with the membrane potential in several cell types, and recently evidence for K(ATP) channels was given in rat corpus luteum, a fast-growing and metabolically highly active tissue. OBJECTIVE: We studied whether K(ATP) channels are present in the human ovary and luteinized granulosa cells (GCs). Human GCs were examined regarding functionality and physiological role of the channel. PATIENTS AND INTERVENTION: Human GCs were obtained from in vitro fertilization patients. RESULTS: K(ATP) channels are involved in membrane potential generation in human GCs because application of the K(ATP) blocker glibenclamide resulted in depolarization as monitored by fluorescence microscopy. Furthermore, glibenclamide significantly attenuated human chorionic gonadotropin-induced progesterone production. The channel pore is composed of K(ir)6.1, but not K(ir)6.2, as indicated by RT-PCR. K(ir)6.1 subunit protein was detected in human follicular and luteal cells by immunohistochemistry and localized to the plasma membrane of human GCs by immunogold staining. RT-PCR experiments revealed the sulfonylurea receptor subunit SUR2B as part of the K(ATP) channel. In addition, mRNAs encoding SUR1 and SUR2A were detected in some preparations. There is no evidence for mitochondrial K(ATP) channels in human GCs because we detected neither K(ir)6.1 protein in mitochondrial membranes nor alterations of mitochondrial membrane potential by glibenclamide or the K(ATP) opener diazoxide. CONCLUSIONS: Endocrine cells of the human ovary possess functional K(ATP) channels, which are linked to both plasma membrane potential generation and progesterone production. Our results may provide new insights into human ovarian physiology and raise the possibility of pharmacological targeting.


Assuntos
Transportadores de Cassetes de Ligação de ATP/fisiologia , Ovário/metabolismo , Canais de Potássio Corretores do Fluxo de Internalização/fisiologia , Esteroides/biossíntese , Transportadores de Cassetes de Ligação de ATP/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Primers do DNA , Feminino , Humanos , Imuno-Histoquímica , Canais KATP , Potenciais da Membrana/efeitos dos fármacos , Potenciais da Membrana/fisiologia , Microscopia Imunoeletrônica , Mitocôndrias/fisiologia , Ovário/efeitos dos fármacos , Técnicas de Patch-Clamp , Bloqueadores dos Canais de Potássio/farmacologia , Canais de Potássio Corretores do Fluxo de Internalização/efeitos dos fármacos , Progesterona/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Frações Subcelulares/metabolismo
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