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1.
AJNR Am J Neuroradiol ; 44(4): 467-473, 2023 04.
Artigo em Inglês | MEDLINE | ID: mdl-36997284

RESUMO

BACKGROUND AND PURPOSE: This retrospective, 2-center study investigated the feasibility, safety, and efficacy at 12-month follow-up of the treatment of ruptured, unruptured, and recurrent intracranial aneurysms using the latest generation of the Woven EndoBridge (WEB) device, the WEB-17 system. MATERIALS AND METHODS: Aneurysms treated with WEB-17 were extracted from the databases of 2 neurovascular centers. Patients, aneurysm characteristics, complications, and clinical and anatomic results were analyzed. RESULTS: From February 2017 to May 2021, two hundred twelve patients with 233 aneurysms (181/233, 77.7%, unruptured-recurrent, and 52/233, 22.3%, ruptured) were included. High treatment feasibility (95.3%) was reported and was similar in ruptured aneurysms (94.2%) and unruptured-recurrent aneurysms (95.6%) (P = .71) and in typical (95.4%) and atypical (94.7%) locations (P = .70), but it was lower in aneurysms with an angle between the parent artery and main aneurysm axis of ≥45° (90.2%) compared with those with an angle of <45° (97.1%) (P = .03). Global mortality and morbidity were 1.9% and 3.8% at 1 month, respectively, and 4.4% and 1.9% at 12 months, respectively. One-month morbidity (P = .02) and mortality (P = .003) were higher in the ruptured group (10.0% and 8.0%, respectively) compared with unruptured-recurrent group (1.9% and 0.0%, respectively). Overall adequate occlusion (complete occlusion and neck remnant) was 86.3%. The percentage of adequate occlusion was higher (P = .05) in the unruptured-recurrent group (88.5%) compared with the ruptured group (77.5%). CONCLUSIONS: The WEB-17 system showed high feasibility for ruptured and unruptured aneurysms, typical and atypical locations, and some aneurysms with an angle of ≥45°. As the most recent generation device, the WEB-17 also demonstrates high safety and good efficacy.


Assuntos
Aneurisma Roto , Embolização Terapêutica , Procedimentos Endovasculares , Aneurisma Intracraniano , Humanos , Resultado do Tratamento , Estudos Retrospectivos , Embolização Terapêutica/métodos , Procedimentos Endovasculares/métodos , Aneurisma Intracraniano/diagnóstico por imagem , Aneurisma Intracraniano/terapia , Aneurisma Roto/diagnóstico por imagem , Aneurisma Roto/terapia
2.
AJNR Am J Neuroradiol ; 44(3): 291-296, 2023 03.
Artigo em Inglês | MEDLINE | ID: mdl-36759143

RESUMO

BACKGROUND AND PURPOSE: Some Woven EndoBridge devices present a persistent intradevice opacification at imaging follow-up, described as the Bicêtre Occlusion Scale Score 1 (BOSS 1) phenomenon. The clinical implications remain unknown. We aimed here to analyze the factors influencing this occurrence and to precisely describe the evolution of BOSS 1 with time using conebeam CT. MATERIALS AND METHODS: We retrospectively analyzed a prospectively maintained Woven EndoBridge database at our tertiary center and included all patients with isolated BOSS 1 and BOSS 1 associated with small neck remnant (BOSS 1 + 2). RESULTS: Two hundred sixty-seven aneurysms were treated with a Woven EndoBridge device between July 2012 and December 2021. Follow-up with DSA was available for 220 aneurysms (median, 5 months), among which BOSS 1 and 1 + 2 were found in 9.1% (20/220) (95% CI, 5.5%-12.7%). A second DSA follow-up (median, 17 months) was performed in 15 of these 20 aneurysms, which revealed that 40% had evolved to complete Woven EndoBridge occlusion, 33% showed a decreased persistent opacification, and 27% remained stable. BOSS 1 was significantly associated with postoperative antiplatelet medication, a lower aneurysm aspect ratio, and the use of the Woven EndoBridge 17 (P < .05). The average Woven EndoBridge shape modification was less pronounced in the BOSS 1 population (P < .02). None of the BOSS 1 or 1 + 2 aneurysms required retreatment or were associated with hemorrhage occurrence. CONCLUSIONS: Isolated persistent flow inside the Woven EndoBridge device at follow-up is rare and notably associated with antiplatelet prescription. It seems to present a benign course in most cases.


Assuntos
Embolização Terapêutica , Procedimentos Endovasculares , Aneurisma Intracraniano , Humanos , Resultado do Tratamento , Estudos Retrospectivos , Aneurisma Intracraniano/terapia , Procedimentos Endovasculares/métodos , Embolização Terapêutica/métodos , Tomografia Computadorizada por Raios X
3.
AJNR Am J Neuroradiol ; 42(12): 2194-2198, 2021 12.
Artigo em Inglês | MEDLINE | ID: mdl-34711551

RESUMO

BACKGROUND AND PURPOSE: Venous pulsatile tinnitus is a disabling condition mainly caused by a stenosis of the lateral sinus. Here, we aimed to report a novel cause of venous pulsatile tinnitus, stenosis of the marginal sinus. MATERIALS AND METHODS: We retrospectively analyzed patients with isolated venous pulsatile tinnitus for which the suspected cause was a stenosis of the marginal sinus, treated or not, between January 2017 and December 2020. Patient charts and imaging were systematically reviewed. All patients underwent noncontrast temporal bone CT and MR imaging. RESULTS: Eight patients (7 women; median age, 36 years) were included. Six patients (75%) were overweight, and 1 patient had idiopathic intracranial hypertension. All patients presented with a typical venous pulsatile tinnitus. The stenosis of the marginal sinus was detected using oblique reconstructions on postcontrast 3D MR imaging. There was no other pathologic finding except ipsilateral stenosis of the lateral sinus in 3 patients. Four patients underwent endovascular therapy with placement of a stent in the marginal sinus, leading to complete resolution of the pulsatile tinnitus for all of them. No complication occurred. Of note, the symptoms of intracranial hypertension also regressed after stent placement in that patient. CONCLUSIONS: Marginal sinus stenosis is a novel cause of venous pulsatile tinnitus, which can be easily detected on MR imaging. Marginal sinus stent placement is safe and efficient. We hypothesized that the marginal sinus stenosis pathophysiology is similar to that of lateral sinus stenosis, which is a common and well-known cause of venous pulsatile tinnitus, explaining the similar clinical presentation and endovascular management.


Assuntos
Pseudotumor Cerebral , Zumbido , Adulto , Constrição Patológica/complicações , Constrição Patológica/diagnóstico , Constrição Patológica/patologia , Cavidades Cranianas/diagnóstico por imagem , Cavidades Cranianas/patologia , Cavidades Cranianas/cirurgia , Feminino , Humanos , Pseudotumor Cerebral/patologia , Estudos Retrospectivos , Stents/efeitos adversos , Zumbido/complicações , Zumbido/etiologia
4.
AJNR Am J Neuroradiol ; 42(8): 1479-1485, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-34117022

RESUMO

BACKGROUND AND PURPOSE: Woven EndoBridge (WEB) devices are increasingly used to treat intracranial aneurysms. A1 asymmetry contributes to anterior communicating artery aneurysm formation and to treatment instability after coiling. We sought to evaluate whether A1 asymmetry had an impact on angiographic outcome in anterior communicating artery aneurysms treated with the WEB. MATERIALS AND METHODS: Anterior communicating artery aneurysms treated between July 2012 and July 2020 with the WEB from an institutional review board-approved database were reviewed. A1 asymmetry was categorized as the following: absence of the A1 segment on 1 side (unilateral A1) versus bilateral A1. Univariate and multivariable analyses assessed independent predictors of adequate (WEB Occlusion Scale A, B, and C) and complete occlusion (WEB Occlusion Scale A and B). RESULTS: Forty-eight individual aneurysms (47 patients) were included in the final analysis, of which 16 (33%) were acutely ruptured. The mean size was 6.5 (SD, 2.2) mm. Adequate and complete occlusion was achieved in 33 (69%) and 30 (63%) cases, respectively. Unilateral A1 was associated with significantly higher rates of adequate (92% versus 60% for bilateral A1; P = .03) and complete occlusion (92% versus 50% for bilateral A1; P < .01). Multivariable logistic regression confirmed unilateral A1 as an independent predictor of both adequate (OR = 10.6; 95% CI, 1.6-220.7; P = .04) and complete occlusion (OR = 9.5, 95% CI, 1.5-190.2; P = .04. A sensitivity analysis comparing unilateral "functional" A1 with bilateral "functional" A1 showed similar results. WEB shape modification was not influenced by the unilateral A1 configuration (P = .70). CONCLUSIONS: Anterior communicating artery aneurysms with a unilateral A1 configuration treated with WEB devices are associated with better angiographic outcome than those with bilateral A1. This finding supports the hypothesis that WEB devices are resistant to unilateral flow in the aneurysm as opposed to coils.


Assuntos
Embolização Terapêutica , Procedimentos Endovasculares , Aneurisma Intracraniano , Humanos , Aneurisma Intracraniano/diagnóstico por imagem , Aneurisma Intracraniano/terapia , Estudos Retrospectivos , Resultado do Tratamento
5.
AJNR Am J Neuroradiol ; 42(7): 1276-1281, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-33926902

RESUMO

BACKGROUND AND PURPOSE: The Woven EndoBridge has proved to be a safe and effective treatment, especially for wide-neck intracranial aneurysms. The recent fifth-generation Woven EndoBridge came with smaller devices. The purpose of this study was to assess the safety and efficiency of Woven EndoBridge treatment of small and very small aneurysms. MATERIALS AND METHODS: Between September 2017 and March 2020, all consecutive patients treated with a 3- or 3.5 mm-width Woven EndoBridge device were included in this retrospective intention-to-treat study. Clinical and radiologic findings were evaluated at immediate and last-available follow-up. Angiographic outcome was assessed by an external expert reader. RESULTS: One hundred twenty-eight aneurysms were treated with a fifth-generation Woven EndoBridge device including 29 with a width of ≤3.5 mm. Ten aneurysms were ruptured (34%). In 3 cases (10%), Woven EndoBridge treatment could not be performed because the aneurysm was still too small for the smallest available Woven EndoBridge device and another endovascular strategy was chosen. The median follow-up time was 11.2 months. Complete and adequate occlusion was obtained in 71% and 90% of the treated aneurysms, respectively. Retreatment was needed in 2 cases (10%). Symptomatic ischemic complications leading to transient neurologic deficits occurred in 2 cases (7%) (1 procedure-related and 1 device-related) but with full spontaneous recovery at discharge. CONCLUSIONS: The fifth-generation Woven EndoBridge device seems to be a safe and technically feasible treatment for both ruptured and unruptured small and very small intracranial aneurysms, with satisfactory occlusion rates on midterm follow-up. However, further study is needed to evaluate longer-term efficiency.


Assuntos
Aneurisma Intracraniano , Prótese Vascular , Embolização Terapêutica , Procedimentos Endovasculares , Feminino , Humanos , Aneurisma Intracraniano/diagnóstico por imagem , Aneurisma Intracraniano/cirurgia , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Resultado do Tratamento
6.
Lancet ; 358(9287): 1066-7, 2001 Sep 29.
Artigo em Inglês | MEDLINE | ID: mdl-11589941

RESUMO

Trimethoprim-sulfamethoxazole has been recommended as part of the standard package of care for people with HIV and AIDS in Africa. A similar antifolate combination, sulfadoxine-pyrimethamine, is now the first-line antimalarial drug in several of the African countries with the highest rates of HIV infection. We present evidence of Plasmodium falciparum cross-resistance between trimethoprim and pyrimethamine at the molecular level. The impact of trimethoprim-sulfamethoxazole on the efficacy of sulfadoxine-pyrimethamine needs to be assessed urgently, and alternative antimalarial treatment should be considered for people on trimethoprim-sulfamethoxazole prophylaxis.


Assuntos
Antimaláricos/uso terapêutico , Malária Falciparum/prevenção & controle , Plasmodium falciparum/genética , Pirimetamina/uso terapêutico , Tetra-Hidrofolato Desidrogenase/genética , Trimetoprima/uso terapêutico , África , Alelos , Animais , Criança , Resistência a Medicamentos/genética , Genótipo , Humanos , Plasmodium falciparum/efeitos dos fármacos , Mutação Puntual
7.
Mol Biochem Parasitol ; 112(2): 239-52, 2001 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-11223131

RESUMO

Folate metabolism in the human malaria parasite Plasmodium falciparum is an essential activity for cell growth and replication, and the target of an important class of therapeutic agents in widespread use. However, resistance to antifolate drugs is a major health problem in the developing world. To date, only two activities in this complex pathway have been targeted by antimalarials. To more fully understand the mechanisms of antifolate resistance and to identify promising targets for new chemotherapies, we have cloned genes encoding as yet uncharacterised enzymes in this pathway. By means of complementation experiments using 1-carbon metabolism mutants of both Escherichia coli and Saccharomyces cerevisiae, we demonstrate here that one of these parasite genes encodes both dihydrofolate synthetase (DHFS) and folylpolyglutamate synthetase (FPGS) activities, which catalyse the synthesis and polyglutamation of folate derivatives, respectively. The malaria parasite is the first known example of a eukaryote encoding both DHFS and FPGS activities in a single gene. DNA sequencing of this gene in antifolate-resistant strains of P. falciparum, as well as drug-inhibition assays performed on yeast and bacteria expressing PfDHFS--FPGS, indicate that current antifolate regimes do not target this enzyme. As PfDHFS--FPGS harbours two activities critical to folate metabolism, one of which has no human counterpart, this gene product offers a novel chemotherapeutic target with the potential to deliver a powerful blockage to parasite growth.


Assuntos
Escherichia coli/genética , Complexos Multienzimáticos/metabolismo , Peptídeo Sintases/metabolismo , Plasmodium falciparum/enzimologia , Saccharomyces cerevisiae/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Clonagem Molecular , Escherichia coli/enzimologia , Escherichia coli/metabolismo , Antagonistas do Ácido Fólico/farmacologia , Deleção de Genes , Genes de Protozoários/genética , Teste de Complementação Genética , Glicina/metabolismo , Metionina/metabolismo , Dados de Sequência Molecular , Complexos Multienzimáticos/química , Complexos Multienzimáticos/genética , Peptídeo Sintases/química , Peptídeo Sintases/genética , Plasmodium falciparum/genética , RNA Fúngico/análise , RNA Fúngico/genética , Saccharomyces cerevisiae/enzimologia , Saccharomyces cerevisiae/metabolismo , Alinhamento de Sequência , Transformação Genética
8.
N Engl J Med ; 344(4): 257-63, 2001 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-11172152

RESUMO

BACKGROUND: Chloroquine-resistant Plasmodium falciparum malaria is a major health problem, particularly in sub-Saharan Africa. Chloroquine resistance has been associated in vitro with point mutations in two genes, pfcrt and pfmdr 1, which encode the P. falciparum digestive-vacuole transmembrane proteins PfCRT and Pgh1, respectively. METHODS: To assess the value of these mutations as markers for clinical chloroquine resistance, we measured the association between the mutations and the response to chloroquine treatment in patients with uncomplicated falciparum malaria in Mali. The frequencies of the mutations in patients before and after treatment were compared for evidence of selection of resistance factors as a result of exposure to chloroquine. RESULTS: The pfcrt mutation resulting in the substitution of threonine (T76) for lysine at position 76 was present in all 60 samples from patients with chloroquine-resistant infections (those that persisted or recurred after treatment), as compared with a base-line prevalence of 41 percent in samples obtained before treatment from 116 randomly selected patients (P<0.001), indicating absolute selection for this mutation. The pfmdr 1 mutation resulting in the substitution of tyrosine for asparagine at position 86 was also selected for, since it was present in 48 of 56 post-treatment samples from patients with chloroquine-resistant infections (86 percent), as compared with a base-line prevalence of 50 percent in 115 samples obtained before treatment (P<0.001). The presence of pfcrt T76 was more strongly associated with the development of chloroquine resistance (odds ratio, 18.8; 95 percent confidence interval, 6.5 to 58.3) than was the presence of pfmdr 1 Y86 (odds ratio, 3.2; 95 percent confidence interval, 1.5 to 6.8) or the presence of both mutations (odds ratio, 9.8; 95 percent confidence interval, 4.4 to 22.1). CONCLUSIONS: This study shows an association between the pfcrt T76 mutation in P. falciparum and the development of chloroquine resistance during the treatment of malaria. This mutation can be used as a marker in surveillance for chloroquine-resistant falciparum malaria.


Assuntos
Cloroquina/uso terapêutico , Malária Falciparum/tratamento farmacológico , Plasmodium falciparum/genética , Mutação Puntual , Adulto , Fatores Etários , Animais , Criança , Cloroquina/farmacologia , Análise Mutacional de DNA , Resistência a Medicamentos/genética , Marcadores Genéticos , Humanos , Modelos Logísticos , Malária Falciparum/parasitologia , Plasmodium falciparum/efeitos dos fármacos , Valor Preditivo dos Testes , Prevalência , Seleção Genética , Resultado do Tratamento
9.
J Infect Dis ; 182(3): 993-6, 2000 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-10950805

RESUMO

A prospective study was conducted to measure the selective effect of pyrimethamine prophylaxis on point mutations in Plasmodium falciparum dihydrofolate reductase (DHFR). A total of 109 Malian children were given pyrimethamine weekly for 5 weeks. P. falciparum infections were analyzed by polymerase chain reaction for DHFR mutations, which were dramatically more frequent among prophylaxis-breakthrough infections than at baseline: the prevalence of Asn-108 rose from 13% to 100%, Ile-51 from 4% to 50%, and Arg-59 from 11% to 90%. Eight persistent infections lacking detectable DHFR mutations at baseline developed multiple mutations within 1 week of the patients' starting pyrimethamine prophylaxis. Microsatellite analysis found no evidence of clonal identity among baseline and breakthrough infections. Analysis of these data demonstrates that under prophylaxis conditions, pyrimethamine is strongly selective for DHFR mutations, which arise extremely rapidly under drug pressure, even when undetectable in the initial infection. These findings have implications for prophylaxis regimens with other antifolate drugs.


Assuntos
Antimaláricos/farmacologia , Mutação , Plasmodium falciparum/enzimologia , Pirimetamina/farmacologia , Tetra-Hidrofolato Desidrogenase/genética , Animais , Criança , Pré-Escolar , Feminino , Genótipo , Humanos , Masculino , Mali , Repetições de Microssatélites , Plasmodium falciparum/efeitos dos fármacos , Estudos Prospectivos
10.
Am J Trop Med Hyg ; 60(3): 475-8, 1999 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-10466980

RESUMO

To assess pyrimethamine-sulfadoxine (PS) efficacy in Mali, and the role of mutations in Plasmodium falciparum dihydrofolate reductase (DHFR) and dihydropteroate synthase (DHPS) in in vivo PS resistance, 190 patients with uncomplicated P. falciparum malaria were treated with PS and monitored for 56 days. Mutation-specific polymerase chain reactions and digestion with restriction endonucleases were used to detect DHFR and DHPS mutations on filter paper blood samples from pretreatment and post-treatment infections. Only one case each of RI and RII level resistance and no cases of RIII resistance or therapeutic failure were observed. Post-PS treatment infections had significantly higher rates of DHFR mutations at codons 108 and 59. No significant selection for DHPS mutations was seen. Pyrimethamine-sulfadoxine is highly efficacious in Mali, and while the low level of resistance precludes assessing the utility of molecular assays for in vivo PS resistance, rapid selection of DHFR mutations supports their role in PS failure.


Assuntos
Antimaláricos/normas , Malária Falciparum/tratamento farmacológico , Plasmodium falciparum/genética , Pirimetamina/normas , Sulfadoxina/normas , Animais , Antimaláricos/uso terapêutico , Sangue/parasitologia , Criança , Enzimas de Restrição do DNA/química , DNA de Protozoário/química , Di-Hidropteroato Sintase/genética , Feminino , Humanos , Masculino , Mali , Parasitemia , Plasmodium falciparum/efeitos dos fármacos , Reação em Cadeia da Polimerase , Estudos Prospectivos , Pirimetamina/uso terapêutico , Sulfadoxina/uso terapêutico , Tetra-Hidrofolato Desidrogenase/genética , Resultado do Tratamento
11.
Am J Physiol ; 276(3): C611-20, 1999 03.
Artigo em Inglês | MEDLINE | ID: mdl-10069988

RESUMO

The variety of mitochondrial morphology in healthy and diseased cells can be explained by regulated mitochondrial fusion. Previously, a mitochondrial outer membrane fraction containing fusogenic, aluminum fluoride (AlF4)-sensitive GTP-binding proteins (mtg) was separated from rat liver (J. D. Cortese, Exp. Cell Res. 240: 122-133, 1998). Quantitative confocal microscopy now reveals that mtg transiently increases mitochondrial membrane potential (DeltaPsi) when added to permeabilized rat hepatocytes (15%), rat fibroblasts (19%), and rabbit myocytes (10%). This large mtg-induced DeltaPsi increment is blocked by fusogenic GTPase-specific modulators such as guanosine 5'-O-(3-thiotriphosphate), excess GTP (>100 microM), and AlF4, suggesting a linkage between DeltaPsi and mitochondrial fusion. Accordingly, stereometric analysis shows that decreasing DeltaPsi or ATP synthesis with respiratory inhibitors limits mtg- and AlF4-induced mitochondrial fusion. Also, a specific G protein inhibitor (Bordetella pertussis toxin) hyperpolarizes mitochondria and leads to a loss of AlF4-dependent mitochondrial fusion. These results place mtg-induced DeltaPsi changes upstream of AlF4-induced mitochondrial fusion, suggesting that GTPases exert DeltaPsi-dependent control of the fusion process. Mammalian mitochondrial morphology thus can be modulated by cellular energetics.


Assuntos
Proteínas de Ligação ao GTP/fisiologia , Fígado/fisiologia , Mitocôndrias Cardíacas/fisiologia , Mitocôndrias Hepáticas/fisiologia , Organelas/fisiologia , Animais , Membrana Celular/metabolismo , Fígado/citologia , Fígado/metabolismo , Masculino , Fusão de Membrana , Potenciais da Membrana/fisiologia , Coelhos , Ratos , Ratos Sprague-Dawley
12.
Mol Biochem Parasitol ; 94(2): 205-14, 1998 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-9747971

RESUMO

Two new dihydrofolate reductase (DHFR) mutations were recently discovered in Plasmodium falciparum samples from an area of Bolivia with high rates of in vivo resistance to pyrimethamine-sulfadoxine: a Cys-->Arg point mutation in codon 50 and a five amino acid insertion after codon 30, termed the Bolivia repeat. We used a yeast expression system to screen these new DHFR mutants, as well as all of the other known DHFR mutant genotypes, against four antifolates: pyrimethamine, cycloguanil, chlorcycloguanil, and WR99210. The prodrug proguanil was also evaluated. The primary 108-Asn mutation, the known secondary mutations 51-Ile, 59-Arg and 164-Leu, as well as the 50-Arg mutation, all progressively enhanced pyrimethamine resistance in naturally observed combinations with one another, with the presence of 164-Leu most significantly increasing resistance. Cycloguanil and chlorcycloguanil resistance were most impacted by 164-Leu and the paired 16-Val/108-Thr. Proguanil had no effect on malaria DHFR. All DHFRs analyzed were sensitive to WR99210. The Bolivia repeat did not markedly affect drug sensitivity. We conclude that malaria DHFR can be reliably, rapidly and inexpensively analyzed in yeast for activity against a broad spectrum of antifolates. This system may be useful for initially characterizing newly discovered genotypes before proceeding to P. falciparum transfection; for large-scale geographic surveys of drug resistance; and for screening new antifolates or new antifolate combinations for their effectiveness against a large panel of DHFR mutants.


Assuntos
Antimaláricos/farmacologia , Antagonistas do Ácido Fólico/farmacologia , Plasmodium falciparum/enzimologia , Tetra-Hidrofolato Desidrogenase/genética , Animais , Bolívia , DNA de Protozoário , Resistência a Medicamentos/genética , Antagonistas do Ácido Fólico/uso terapêutico , Malária Falciparum/tratamento farmacológico , Mutação , Plasmodium falciparum/efeitos dos fármacos , Plasmodium falciparum/genética , Proguanil/farmacologia , Proteínas Recombinantes/metabolismo , Saccharomyces cerevisiae/efeitos dos fármacos , Saccharomyces cerevisiae/enzimologia , Saccharomyces cerevisiae/genética , Tetra-Hidrofolato Desidrogenase/metabolismo , Transformação Genética
14.
Biochemistry ; 37(18): 6402-9, 1998 May 05.
Artigo em Inglês | MEDLINE | ID: mdl-9572857

RESUMO

One-tenth of cytochrome c (cyt c) remains bound to the inner mitochondrial membrane (IMM) at physiological ionic strength (I; i.e. , I approximately 150 mM), exhibiting decreased electron transport (ET) activity. We now show that this form of membrane-bound cyt c (MB-cyt c) can be obtained in vitro and that binding to membranes at low I generates an additional conformation with higher ET activity. This low I bound form of MB-cyt c (MBL-cyt c) exhibited intrinsic ET rates similar to those of electrostatically bound cyt c (EB-cyt c). The ET activity of IMM-bound MB-cyt c approached slowly that of MBL-cyt c or EB-cyt c, suggesting that MB-cyt c converts to MBL-cyt c while bound to IMM. When maintained at physiological I, both forms of MB-cyt c were released from the membrane, indicating that they convert to an EB-cyt c-like form. This process may be very dynamic in cellular mitochondria, as binding and release for both MB-cyt c forms increased considerably with temperature. I-Dependent binding of MB-cyt c does not require IMM, and it can be reproduced using large or small unilamellar vesicles (SUV). Using SUV-cyt c complexes, we characterized the secondary structure of MB-cyt c and MBL-cyt c by circular dichroism. Conformational analysis revealed that cyt c binding as MB-cyt c decreases its alpha-helical content (70-79%) and increases its beta-sheet up to 135%. The secondary structure of MBL-cyt c was similar to that of EB-cyt c and soluble cyt c, with a modest increase in beta-sheet. Taken together, our experiments suggest that physiological cyt c exists in soluble and membrane-bound conformations with similar ET activity, which may exchange very rapidly, and that soluble hydrophilic proteins can bind transiently to biomembranes.


Assuntos
Grupo dos Citocromos c/química , Grupo dos Citocromos c/fisiologia , Animais , Membrana Celular/enzimologia , Dicroísmo Circular , Transporte de Elétrons , Conformação Proteica , Estrutura Secundária de Proteína , Ovinos , Solubilidade , Temperatura
15.
Biochim Biophys Acta ; 1371(2): 185-98, 1998 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-9630622

RESUMO

We have shown that fusion of small unilamellar vesicles (SUV) with outer mitochondrial membranes occurs at physiological pH [Cortese et al., 1991, J. Cell Biol., Vol. 113, 1331-1340]. The proteins driving this process could be involved in mitochondrial membrane fusion, which is presently poorly understood. In this study, we release from rat liver mitochondria a soluble protein fraction (SF) that increases fusion at neutral pH measured by membrane fusion assays (MFAs). Since this fusogenic activity was specifically enhanced by GTP, we separate SF by GTP affinity chromatography into: i) a flow-through subfraction (G1) containing numerous proteins with low GTP affinity; and ii) a subfraction (G2) which may contain GTP-binding proteins. A novel array of MFAs is developed to study the fusogenic properties of these fractions, measuring the merging of membranes (membrane-mixing) or the mixing of intravesicular aqueous contents (content-mixing). The MFAs use: a) SUV/large unilamellar vesicles, lacking mitochondrial membranes; b) SUV/mitochondria, reconstituting membrane-mitochondrial interactions; and c) mitochondria/mitochondria, mimicking mitochondrial fusion. The results indicate that: i) G1 contains GTP-independent, in vitro fusogenic proteins that are not sufficient to induce mitochondrial fusion; and ii) G2 contains GTP-dependent proteins that stimulate mitochondrial fusion at neutral pH. The MFAs described here could be used to monitor the isolation of active proteins from these subfractions and to define the mechanism of intermitochondrial membrane fusion.


Assuntos
Guanosina Trifosfato/farmacologia , Membranas Intracelulares/química , Fusão de Membrana , Proteínas de Membrana/química , Mitocôndrias Hepáticas/química , Mitocôndrias/química , Animais , Transferência de Energia , Polarização de Fluorescência , Masculino , Fusão de Membrana/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Espectrometria de Fluorescência
16.
Exp Cell Res ; 240(1): 122-33, 1998 Apr 10.
Artigo em Inglês | MEDLINE | ID: mdl-9570927

RESUMO

In normal livers, hepatocytes contain a large number of spheroidal mitochondria. Mitochondrial morphology changes drastically in liver disease, but the underlying fusion-fission mechanisms are not known. We detected GTP- and aluminum fluoride-dependent membrane fusion events between rat liver mitochondria. Separation of outer mitochondrial membrane-derived proteins led to a subfraction containing a 60-kDa protein band that is detected by specific antibodies directed to common amino acid sequences of the GTP-binding site or carboxyl-terminus of eukaryotic heterotrimeric G-protein alpha subunits. Addition of this subfraction and aluminum fluoride to permeabilized rat hepatocytes triggered a substantial morphological change in hepatic mitochondria, giving them the three-dimensional appearance of a tubulovesicular network. Comparative stereology using electron and confocal microscopy showed that these morphological changes represent true mitochondrial fusion. Addition of aluminum fluoride alone induces a more limited change in mitochondrial morphology, from spheroidal organelles to short rods. Mitochondria maintained their normal membrane potential and overall membrane ultrastructure after all these morphological changes. Our results reveal that mammalian liver mitochondria contain proteins that stimulate mitochondrial fusion and suggest that members of the GTPase superfamily control the normalcy of mitochondrial morphology, which is closely linked to physiological cellular energetics.


Assuntos
Compostos de Alumínio/farmacologia , Fluoretos/farmacologia , Membranas Intracelulares/efeitos dos fármacos , Fígado/metabolismo , Fusão de Membrana/efeitos dos fármacos , Mitocôndrias/efeitos dos fármacos , Animais , Compartimento Celular/fisiologia , Proteínas de Ligação ao GTP/fisiologia , Guanosina Trifosfato/metabolismo , Microscopia Confocal , Ratos , Transdução de Sinais/fisiologia
17.
J Infect Dis ; 176(6): 1590-6, 1997 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-9395372

RESUMO

To assess the relationship between mutations in Plasmodium falciparum dihydrofolate reductase (DHFR) and dihydropteroate synthase (DHPS) and clinical pyrimethamine-sulfadoxine resistance, polymerase chain reaction surveys and analyses for new mutations were conducted in four countries with increasing levels of pyrimethamine-sulfadoxine resistance: Mali, Kenya, Malawi, and Bolivia. Prevalence of mutations at DHFR codon 108 and a new mutation at DHPS 540 correlated with increased pyrimethamine-sulfadoxine resistance (P < .05). Mutations at DHFR 51, DHFR 59, and DHPS 437 correlated with resistance without achieving statistical significance. Mutations at DHFR 164 and DHPS 581 were common in Bolivia, where pyrimethamine-sulfadoxine resistance is widespread, but absent in African sites. Two new DHFR mutations, a point mutation at codon 50 and an insert at codon 30, were found only in Bolivia. DHFR and DHPS mutations occur in a progressive, stepwise fashion. Identification of specific sets of mutations causing in vivo drug failure may lead to the development of molecular surveillance methods for pyrimethamine-sulfadoxine resistance.


Assuntos
Antimaláricos/uso terapêutico , Di-Hidropteroato Sintase/genética , Malária Falciparum/parasitologia , Plasmodium falciparum/genética , Pirimetamina/uso terapêutico , Sulfadoxina/uso terapêutico , Tetra-Hidrofolato Desidrogenase/genética , África/epidemiologia , Sequência de Aminoácidos , Animais , Antimaláricos/farmacologia , Sequência de Bases , Bolívia/epidemiologia , Clonagem Molecular , DNA de Protozoário/análise , DNA de Protozoário/genética , Di-Hidropteroato Sintase/metabolismo , Combinação de Medicamentos , Resistência a Medicamentos , Humanos , Malária Falciparum/tratamento farmacológico , Malária Falciparum/epidemiologia , Malária Falciparum/genética , Epidemiologia Molecular , Dados de Sequência Molecular , Estrutura Molecular , Mutagênese Insercional , Plasmodium falciparum/efeitos dos fármacos , Plasmodium falciparum/enzimologia , Mutação Puntual , Reação em Cadeia da Polimerase , Prevalência , Pirimetamina/farmacologia , Sulfadoxina/farmacologia , Tetra-Hidrofolato Desidrogenase/química , Tetra-Hidrofolato Desidrogenase/metabolismo
18.
Med Phys ; 24(9): 1499-506, 1997 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-9304579

RESUMO

Protons have long been recognized as low LET radiation in radiotherapy. However, a detailed account of LET (linear energy transfer) and RBE (relative biological effectiveness) changes with incident beam energy and depth in tissue is still unresolved. This issue is particularly important for treatment planning, where the physical dose prescription is calculated from a RBE using cobalt as the reference radiation. Any significant RBE changes with energy or depth will be important to incorporate in treatment planning. In this paper we present microdosimetry spectra for the proton beam at various energies and depths and compare the results to cell survival studies performed at Loma Linda. An empirically determined biological weighting function that depends on lineal energy is used to correlate the microdosimetry spectra with cell survival data. We conclude that the variations in measured RBE with beam energy and depth are small until the distal edge of the beam is reached. On the distal edge, protons achieve stopping powers as high as 100 keV/micron, which is reflected in the lineal energy spectra taken there. Lineal energy spectra 5 cm beyond the distal edge of the Bragg peak also show a high LET component but at a dose rate 600 times smaller than observed inside the proton field.


Assuntos
Terapia com Prótons , Planejamento da Radioterapia Assistida por Computador/instrumentação , Planejamento da Radioterapia Assistida por Computador/métodos , Animais , Fenômenos Biofísicos , Biofísica , Linhagem Celular , Sobrevivência Celular/efeitos da radiação , Cricetinae , Humanos , Transferência Linear de Energia , Modelos Biológicos , Planejamento da Radioterapia Assistida por Computador/estatística & dados numéricos , Radioterapia de Alta Energia/instrumentação , Radioterapia de Alta Energia/métodos , Radioterapia de Alta Energia/estatística & dados numéricos , Eficiência Biológica Relativa , Tecnologia Radiológica/instrumentação , Tecnologia Radiológica/métodos , Tecnologia Radiológica/estatística & dados numéricos
19.
Am J Physiol ; 272(3 Pt 1): C957-65, 1997 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-9124532

RESUMO

Expression of the human gene A4 is enriched in the colonic epithelium and is transcriptionally activated on differentiation of colonic epithelial cells in vitro (M. M. Oliva, T. C. Wu, and V. W. Yang. Arch. Biochem. Biophys. 302: 183-192, 1993). A4 cDNA contains an open reading frame that predicts a polypeptide of 17 kDa. To determine the function of the A4 protein, we characterized its biochemical and physiological properties. Hydropathy analysis of deduced A4 amino acid sequence revealed four putative membrane-spanning alpha-helices. The hydrophobic nature of A4 was confirmed by its being extractable with organic solvents. Immunocytochemical studies of cells expressing A4 localized it to the endoplasmic reticulum. Moreover, A4 multimerized in vivo as determined by coimmunoprecipitation experiments. The four-transmembrane topology and biophysical characteristics of A4 suggest that it belongs to a family of integral membrane proteins called proteolipids, some of which multimerize to form ion channels. Subsequent electrophysiological studies of nuclei isolated from microinjected Xenopus laevis oocytes transiently expressing A4 showed the appearance of a 28-pS channel. Thus our studies indicate that A4 is a colonic epithelium-enriched protein localized to the endoplasmic reticulum and that, similar to other proteolipids, A4 multimerizes and exhibits characteristics of an ion channel.


Assuntos
Mucosa Intestinal/fisiologia , Canais Iônicos/fisiologia , Proteínas de Membrana/fisiologia , Proteolipídeos/fisiologia , Sequência de Aminoácidos , Animais , Western Blotting , Compartimento Celular , Retículo Endoplasmático/metabolismo , Epitélio/fisiologia , Humanos , Membranas Intracelulares/metabolismo , Proteínas com Domínio MARVEL , Substâncias Macromoleculares , Potenciais da Membrana , Proteínas de Membrana/química , Dados de Sequência Molecular , Testes de Precipitina , Proteínas Recombinantes , Solubilidade , Células Tumorais Cultivadas , Xenopus laevis
20.
J Exp Psychol Hum Percept Perform ; 22(1): 133-43, 1996 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-8742257

RESUMO

A metric representation of shape is preserved by a Fourier analysis of the cumulative angular bend of a shape's contour. Three experiments examined the relationship between variation in Fourier descriptors and judgments of perceptual shape similarity. Multidimensional scaling of similarity judgments resulted in highly ordered solutions for matrices of shapes generated by a Fourier synthesis of a few frequencies. Multiple regression analyses indicated that particular Fourier components best accounted for the recovered dimensions. In addition, variations in the amplitude and the phase of a given frequency, as well as the amplitudes of 2 different frequencies, produced independent effects on perceptual similarity. These results suggest that a Fourier representation is consistent with the perceptual similarity of shapes, at least for the relatively low-dimensional Fourier shapes considered.


Assuntos
Percepção de Forma , Análise de Fourier , Humanos
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