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1.
J Perinatol ; 36(11): 1001-1007, 2016 11.
Artigo em Inglês | MEDLINE | ID: mdl-27583386

RESUMO

OBJECTIVE: Nurses provide parental support and education in the neonatal intensive care unit (NICU), but it is unknown if satisfaction and expectations about nursing care differ between racial groups. STUDY DESIGN: A prospective cohort was constructed of families with a premature infant presenting to primary care between 1 January 2010 and 1 January 2013 (N=249, 52% white, 42% black). Responses to questions about satisfaction with the NICU were analyzed in ATLAS.ti using the standard qualitative methodology. RESULTS: One hundred and twenty (48%) parents commented on nursing. Fifty-seven percent of the comments were positive, with black parents more negative (58%) compared with white parents (33%). Black parents were most dissatisfied with how nurses supported them, wanting compassionate and respectful communication. White parents were most dissatisfied with inconsistent nursing care and lack of education about their child. CONCLUSIONS: Racial differences were found in satisfaction and expectations with neonatal nursing care. Accounting for these differences will improve parental engagement during the NICU stay.


Assuntos
Enfermagem Neonatal/organização & administração , Relações Enfermeiro-Paciente , Cuidados de Enfermagem/psicologia , Pais/psicologia , Satisfação do Paciente , Adolescente , Adulto , Negro ou Afro-Americano/psicologia , Assistência à Saúde Culturalmente Competente , Empatia , Feminino , Humanos , Recém-Nascido , Recém-Nascido Prematuro , Unidades de Terapia Intensiva Neonatal/organização & administração , Masculino , Estudos Prospectivos , Inquéritos e Questionários , População Branca/psicologia , Adulto Jovem
2.
Int J Tuberc Lung Dis ; 19(9): 1027-32, 2015 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-26260819

RESUMO

SETTING: South Granada Health Area (SGHA), Spain. OBJECTIVE: To describe the characteristics of concomitant tuberculosis (TB) and lung cancer cases. DESIGN: A total of 319 TB cases diagnosed between January 2003 and December 2010 were evaluated and identified using a prospective database. During this period, samples of bronchial secretions were obtained from all patients who underwent fibreoptic bronchoscopy (FBS) as part of a TB screening programme. A descriptive study was conducted. RESULTS: Concomitant TB and lung cancer were diagnosed in 15 cases (4.7% of total TB cases). The most common radiographic finding was atelectasis (53.3%), and the most common histological type was epidermoid carcinoma (60%). Lung cancer stage was advanced (III-IV) in 60% of the cases. CONCLUSION: The association between TB and lung cancer found in the SGHA after implementing a TB screening programme was higher than in other studies. This suggests that it would be advisable to perform acid-fast bacilli smear and mycobacterial culture of bronchial aspirates in all patients with presumed lung cancer, particularly in high TB prevalence areas.


Assuntos
Carcinoma de Células Escamosas/diagnóstico , Neoplasias Pulmonares/diagnóstico , Pulmão/patologia , Mycobacterium tuberculosis/isolamento & purificação , Tuberculose/complicações , Idoso , Biópsia , Broncoscopia , Carcinoma de Células Escamosas/microbiologia , Comorbidade , Feminino , Humanos , Neoplasias Pulmonares/microbiologia , Masculino , Pessoa de Meia-Idade , Estadiamento de Neoplasias , Estudos Prospectivos , Espanha
3.
Pediatr Transplant ; 18(2): E57-63, 2014 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24438382

RESUMO

The most common identifiable causes of acute liver failure in pediatric patients are infection, drug toxicity, metabolic disease, and autoimmune processes. In many cases, the etiology of acute liver failure cannot be determined. Acute leukemia is an extremely rare cause of acute liver failure, and liver transplantation has traditionally been contraindicated in this setting. We report a case of acute liver failure in a previously healthy 15-yr-old male from pre-B-cell acute lymphoblastic leukemia. He underwent liver transplantation before the diagnosis was established, and has subsequently received chemotherapy for pre-B-cell acute lymphoblastic leukemia. He is currently alive 31 months post-transplantation. The published literature describing acute lymphoblastic leukemia as a cause of acute liver failure is reviewed.


Assuntos
Leucemia de Células B/complicações , Leucemia de Células B/terapia , Falência Hepática Aguda/complicações , Falência Hepática Aguda/cirurgia , Transplante de Fígado , Leucemia-Linfoma Linfoblástico de Células Precursoras/complicações , Leucemia-Linfoma Linfoblástico de Células Precursoras/terapia , Adolescente , Biópsia , Humanos , Imunossupressores/uso terapêutico , Fígado/patologia , Testes de Função Hepática , Masculino , Doadores de Tecidos , Resultado do Tratamento
4.
Acta Psychol (Amst) ; 144(1): 83-96, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23770570

RESUMO

In psycholinguistic studies using error rates as a response measure, response times (RT) are most often analyzed independently of the error rate, although it is widely recognized that they are related. In this paper we present a mixed effects logistic regression model for the error rate that uses RT as a trial-level fixed- and random-effect regression input. Production data from a translation-recall experiment are analyzed as an example. Several model comparisons reveal that RT improves the fit of the regression model for the error rate. Two simulation studies then show how the mixed effects regression model can identify individual participants for whom (a) faster responses are more accurate, (b) faster responses are less accurate, or (c) there is no relation between speed and accuracy. These results show that this type of model can serve as a useful adjunct to traditional techniques, allowing psycholinguistic researchers to examine more closely the relationship between RT and accuracy in individual subjects and better account for the variability which may be present, as well as a preliminary step to more advanced RT-accuracy modeling.


Assuntos
Percepção Auditiva , Idioma , Modelos Psicológicos , Tempo de Reação , Fala , Adulto , Feminino , Humanos , Modelos Lineares , Modelos Logísticos , Masculino , Projetos de Pesquisa , Espanha
5.
Am J Transplant ; 13(3): 808-10, 2013 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-23331705

RESUMO

Posterior reversible encephalopathy syndrome (PRES) is a small vessel microangiopathy of the cerebral vasculature that occurs in 0.5-5% of solid organ transplant recipients, most commonly associated with tacrolimus (Tac). Clinical manifestations include hypertension and neurologic symptoms. We report an adult multivisceral transplant recipient who experienced recurrent PRES initially associated with Tac and subsequently with sirolimus. A 49-year-old woman with short bowel syndrome underwent multivisceral transplantation due to total parenteral nutrition-related liver disease. She was initially maintained on Tac, mycophenalate mofetil (MMF) and prednisone. Three months after transplantation, she developed renal dysfunction, leading to a reduction in Tac and the addition of sirolimus. Eight months after transplantation, she developed PRES. Tac was discontinued and PRES resolved. Sirolimus was increased to maintain trough levels of 12-15 ng/mL. Fourteen months after transplant, she experienced recurrent PRES which resolved after discontinuing sirolimus. Currently 3 years posttransplant, she is maintained on cyclosporine, MMF and prednisone with no PRES recurrence. In addition to calcineurin inhibitors, sirolimus may also be associated with PRES after solid organ transplantation. Ours is the first report of sirolimus-associated PRES in the setting of multivisceral transplantation. Identifying a safe alternative immunosuppression regimen was challenging but ultimately successful.


Assuntos
Rejeição de Enxerto/tratamento farmacológico , Hepatopatias/cirurgia , Transplante de Fígado/efeitos adversos , Síndrome da Leucoencefalopatia Posterior/induzido quimicamente , Complicações Pós-Operatórias/prevenção & controle , Sirolimo/efeitos adversos , Tacrolimo/efeitos adversos , Feminino , Rejeição de Enxerto/induzido quimicamente , Humanos , Imunossupressores/efeitos adversos , Pessoa de Meia-Idade , Síndrome da Leucoencefalopatia Posterior/tratamento farmacológico , Prognóstico , Recidiva
6.
Am J Transplant ; 12(8): 2242-6, 2012 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22594310

RESUMO

Restoring abdominal wall cover and contour in children undergoing bowel and multivisceral transplantation is often challenging due to discrepancy in size between donor and recipient, poor musculature related to birth defects and loss of abdominal wall integrity from multiple surgeries. A recent innovation is the use of vascularized posterior rectus sheath to enable closure of abdomen. We describe the application of this technique in two pediatric multivisceral transplant recipients--one to buttress a lax abdominal wall in a 22-month-old child with megacystis microcolon intestinal hypoperistalsis syndrome and another to accommodate transplanted viscera in a 10-month child with short bowel secondary to gastoschisis and loss of domain. This is the first successful report of this procedure with long-term survival. The procedure has potential application to facilitate difficult abdominal closure in both adults and pediatric liver and multivisceral transplantation.


Assuntos
Anormalidades Múltiplas/cirurgia , Pseudo-Obstrução Intestinal/cirurgia , Transplante de Órgãos , Colo/anormalidades , Colo/cirurgia , Feminino , Humanos , Lactente , Masculino , Transplante Homólogo , Bexiga Urinária/anormalidades , Bexiga Urinária/cirurgia
7.
J Bone Joint Surg Br ; 93(12): 1617-20, 2011 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-22161923

RESUMO

Symptomatic and asymptomatic deep-vein thrombosis (DVT) is a common complication of knee replacement, with an incidence of up to 85% in the absence of prophylaxis. National guidelines for thromboprophylaxis in knee replacement are derived from total knee replacement (TKR) data. No guidelines exist specific to unicompartmental knee replacement (UKR). We investigated whether the type of knee arthroplasty (TKR or UKR) was related to the incidence of DVT and discuss the applicability of existing national guidelines for prophylaxis following UKR. Data were collected prospectively on 3449 knee replacements, including procedure type, tourniquet time, surgeon, patient age, use of drains and gender. These variables were related to the incidence of symptomatic DVT. The overall DVT rate was 1.6%. The only variable that had an association with DVT was operation type, with TKR having a higher incidence than UKR (2.2% versus 0.3%, p < 0.001). These data show that the incidence of DVT after UKR is both clinically and statistically significantly lower than that after TKR. TKR and UKR patients have different risk profiles for symptomatic DVT. The risk-benefit ratio for TKR that has been used to produce national guidelines may not be applicable to UKR. Further research is required to establish the most appropriate form of prophylaxis for UKR.


Assuntos
Artroplastia do Joelho/métodos , Complicações Pós-Operatórias/epidemiologia , Guias de Prática Clínica como Assunto , Trombose Venosa/epidemiologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Artroplastia do Joelho/efeitos adversos , Feminino , Humanos , Incidência , Masculino , Pessoa de Meia-Idade , Complicações Pós-Operatórias/etiologia , Estudos Prospectivos , Fatores de Risco , Resultado do Tratamento , Trombose Venosa/etiologia , Trombose Venosa/prevenção & controle
8.
J Environ Manage ; 80(3): 191-7, 2006 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-16338057

RESUMO

Assessment methods for determining the presence and number of fecal bacteria and Escherichia coli (E. coli) in waters, foodstuffs, sewage effluent, and soils have evolved from multiple tube fermentations (MTF's) to membrane filtrations (MF's) to, most recently, defined substrate technologies (DST's). Mounting evidence indicates Colilert DST (IDEXX, Westbrook, ME) to be a versatile assessment technique for detecting and enumerating E. coli over a range of applications. This study compared the performance of Colilert DST with a confirmed standard MF technique using m-FC broth (Millipore, Bedford, MA) in assessing E. coli in ten different environmental water samples obtained monthly over a 3-year period from the upper Appomattox River, VA. For the duration of the study, E. coli counts measured by Colilert DST were positively correlated (Pearson's correlation coefficient=0.956; slope=0.979; p<0.0001) with E. coli counts measured by confirmed MF procedures. The results of a two-factor ANOVA revealed that Colilert DST counts compared equally to confirmed MF counts by year (p=0.974), by stream sampled (p=1.0), and by season (p=0.696). E. coli counts were significantly lower during cold season months (Dec/Jan/Feb) than during warm season months (Jun/Jul/Aug) for each year contributing to marked variation in sample quality. Counts obtained by Colilert DST compared equally to those obtained by MF across all samples and dates for the three years. Colilert DST presents a laboratory protocol that is simpler to manage, quicker to process, and easier to quantify results than MF. These factors, plus the enhanced precision and versatility of Colilert DST over the span of this three-year study attests to its suitability for testing ambient surface waters.


Assuntos
Enterobacteriaceae/isolamento & purificação , Escherichia coli/isolamento & purificação , Microbiologia da Água , Purificação da Água/métodos , Análise de Variância , Contagem de Colônia Microbiana , Fezes/microbiologia , Filtração
9.
Brain Behav Immun ; 19(5): 423-35, 2005 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-15935613

RESUMO

Prolonged, exhaustive exercise has been associated with impaired immune responsiveness and increased susceptibility to infection. We have shown that one bout of exercise to fatigue followed by viral challenge increases mortality. Stress hormones such as corticosteroids and catecholamines have been suggested as potential mediators of exhaustive exercise-induced immunosuppression. The purpose of this study was to determine whether the administration of pharmacological agents to block the effect of catecholamines or corticosteroids would minimize the immunosuppression associated with this type of exercise. Mice either exercised to fatigue or were exposed to control conditions, and mice received an i.p. injection of either nadolol (beta-adrenergic receptor antagonist), RU486 (glucocorticoid type II receptor antagonist), or vehicle. Fifteen minutes post-exercise, mice were exposed to viral infection (Herpes simplex virus; HSV) via an intranasal route, and cells were collected 3 days post-infection. The results showed that exercise suppressed HSV-specific cell proliferation, HSV-specific IL-2, and IFN-gamma, but did not alter these same immune parameters when the mitogen ConA was used to stimulate cells. In addition, exercise reduced NK cell cytotoxicity, alveolar cell TNFalpha, and peritoneal IL-1beta, but did not affect IL-10. The pharmacological blockade did not attenuate the exercise-associated immunosuppression. In fact, RU486 treatment exacerbated the exercise-induced decline in HSV-induced IL-2 production and cell proliferation. RU486 and nadolol treatment also tended to decrease IL-10, IFN-gamma, TNFalpha (nadolol only), and IL-1beta (RU486 only) in both exercise and control mice, suggesting that stress hormones may be necessary during infection for optimal responsiveness. These findings suggest that suppression of immune defenses during viral infection persists for at least 3 days post-exercise, and stress hormones may be essential for optimal immune defense to viral challenge, rather than detrimental.


Assuntos
Catecolaminas/fisiologia , Proliferação de Células , Glucocorticoides/metabolismo , Glucocorticoides/fisiologia , Interleucina-2/biossíntese , Esforço Físico/fisiologia , Viroses/imunologia , Viroses/metabolismo , Animais , Antígenos Virais/imunologia , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Concanavalina A/farmacologia , Citocinas/análise , Citocinas/biossíntese , Herpes Simples/imunologia , Herpes Simples/metabolismo , Herpesvirus Humano 1/imunologia , Células Matadoras Naturais/imunologia , Macrófagos Peritoneais/imunologia , Macrófagos Peritoneais/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Mitógenos/farmacologia , Alvéolos Pulmonares/citologia , Alvéolos Pulmonares/efeitos dos fármacos , Células Th1/imunologia , Células Th2/imunologia
10.
J Pharmacol Exp Ther ; 308(2): 644-50, 2004 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-14600252

RESUMO

In this study, we assessed the effects of chronic prenatal ethanol exposure (CPEE) on spatial navigation in the water maze, conditioned responding using food-reinforced lever pressing, and amino acid neurotransmitter release from the hippocampus of the adult guinea pig. Pregnant guinea pigs were treated with ethanol (3 g/kg of maternal body weight/day), isocaloric-sucrose/pair-feeding, or water throughout gestation. Adult offspring were trained in two-lever operant chambers to respond for sucrose pellets, with one lever designated as the reward lever. There were no group differences in response acquisition or lever discrimination on a fixed-ratio 1 (FR-1) schedule. During extinction sessions, CPEE offspring maintained higher levels of responding on the previously reinforced lever, suggesting that CPEE increases perseveration and/or impairs response inhibition but does not affect operant responding for an appetitive reinforcer or the ability to discriminate rewarding from nonrewarding stimuli. In contrast, there was no effect of CPEE on performance in the water maze in the maternal ethanol regimen used in this study. CPEE did not alter electrically evoked glutamate or GABA release from hippocampal brain slices. However, when slices were tested after delivery of a tetanizing stimulation (five 5-s trains at 100 Hz), post-tetanic potentiation of electrically stimulated GABA release was greater in hippocampal slices obtained from CPEE offspring, whereas post-tetanic potentiation of electrically stimulated glutamate release was unaffected. These data suggest that conditioned learning is a sensitive behavioral measure of CPEE-induced brain injury. Increased activity-dependent potentiation of GABA release in the hippocampus may contribute to alterations in synaptic plasticity observed in CPEE offspring.


Assuntos
Etanol/farmacologia , Hipocampo/efeitos dos fármacos , Aprendizagem em Labirinto/efeitos dos fármacos , Efeitos Tardios da Exposição Pré-Natal , Ácido gama-Aminobutírico/metabolismo , Animais , Transporte Biológico , Depressores do Sistema Nervoso Central/farmacologia , Condicionamento Psicológico/efeitos dos fármacos , Feminino , Cobaias , Hipocampo/metabolismo , Neurotransmissores/metabolismo , Gravidez , Resultado da Gravidez
13.
Am J Health Syst Pharm ; 53(19): 2277-90; quiz 2336-7, 1996 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-8893066

RESUMO

The chemistry, pharmacology, pharmacokinetics, and clinical efficacy of acarbose, a new antidiabetic agent, are reviewed. Acarbose reversibly inhibits intestinal alpha-glucosidases, enzymes responsible for the metabolism of complex carbohydrates into absorbable monosaccharide units. This action results in a diminished and delayed rise in blood glucose following a meal, resulting in a reduction in post-prandial hyperglycemia, area under the glucose concentration-time curve, and glycosylated hemoglobin. Other effects include a reduction in postprandial insulin and variable changes in plasma lipid concentrations. In placebo-controlled trials, acarbose caused significant improvements in glycemic control indicators, including glycosylated hemoglobin. Acarbose has demonstrated additional glycemic control when added to other antidiabetic therapies, including sulfonylureas and insulin. Efficacy of acarbose appears to be comparable to or slightly less than that of sulfonylureas or metformin, although it has not been compared with maximal dose of these agents. The most commonly reported adverse drug reactions with acarbose are abdominal pain, diarrhea, and flatulence, which tend to lessen with time. Acarbose may affect the bioavailability of metformin and may be less effective when used in conjunction with intestinal adsorbents and digestive enzyme preparations. Concurrent use with hypoglycemic agents (sulfonylureas and insulin) may cause an increased frequency of hypoglycemia. Acarbose should not be used in individuals with certain intestinal disorders, including inflammatory bowel disease. The dosage should start at 25 mg one to three times daily given with the first bite of each main meal and should be adjusted to a maximum of 50 mg three times daily for patients weighing up to 60 kg or 100 mg three times daily for heavier patients. Acarbose may be considered for first-line antidiabetic therapy in certain patients and may be useful as combination therapy in selected instances. Acarbose is efficacious in improving metabolic control in non-insulin-dependent diabetes mellitus. Further evaluation of its effects on the long-term complications of diabetes is needed.


Assuntos
Diabetes Mellitus Tipo 2/tratamento farmacológico , Inibidores de Glicosídeo Hidrolases , Hipoglicemiantes/uso terapêutico , Trissacarídeos/uso terapêutico , Acarbose , Ensaios Clínicos como Assunto , Diabetes Mellitus Tipo 2/fisiopatologia , Interações Medicamentosas , Humanos , Hipoglicemiantes/efeitos adversos , Trissacarídeos/efeitos adversos
14.
Clin Genet ; 49(6): 318-20, 1996 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-8884084

RESUMO

We report on a patient with monosomy 18 mosaicism, a previously undescribed chromosome abnormality. The phenotype is reminiscent of chromosome 18 ring mosaicism. The reason that the patient survived may be attributed to low level mosaicism for the monosomy.


Assuntos
Cromossomos Humanos Par 18 , Mosaicismo , Fácies , Insuficiência de Crescimento/genética , Feminino , Humanos , Hibridização in Situ Fluorescente , Recém-Nascido , Nistagmo Patológico/genética , Atrofia Óptica/genética
15.
Afr J Med Med Sci ; 21(1): 85-9, 1992 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-1288249

RESUMO

Adi agbon, an oily extract of the endosperm of the coconut fruit (Cocoa nucifera, L.) was investigated as a clearing agent for embryonic soft tissues. Paraffin sections stained with haematoxylin an eosin revealed normal tissue architecture and light microscopic details were easily identified. However, some tissue shrinkage was observed, particularly in the brain. As prepared for this study, this locally available compound is useful for routine work but appears unsuitable for quantitative histological studies.


Assuntos
Cocos , Técnicas Citológicas/normas , Embrião de Mamíferos/citologia , Parafina , Extratos Vegetais/normas , Animais , Estudos de Avaliação como Assunto , Hematoxilina/normas , Camundongos
16.
J Parasitol ; 78(3): 441-6, 1992 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-1597786

RESUMO

In areas endemic for schistosomiasis, the population dynamics of the snail intermediate hosts have a direct effect on parasite transmission. The present study focused on the potential for neonatal Biomphalaria glabrata snails to become infected with Schistosoma mansoni and to produce cercariae under various conditions. It was found that snails as small as 0.74 mm in shell diameter could survive miracidial penetration and could release cercariae when as small as 1.6 mm in diameter. Cercariae produced by small snails were equally infectious for mice when compared with those shed by larger snails. Likewise, histological examination of neonatally exposed snails revealed normally developing parasites at all stages of infection. It was found that in 2 snail populations expressing either high or low susceptibility to the parasite, peak susceptibility occurred at 25 days of age in both groups. Daily cercarial production for neonatally exposed snails was initially low but increased dramatically as the snails grew, eventually reaching values as high as 2,100 cercariae/snail/day. A moderate to high percentage of snails infected as neonates was eventually capable of simultaneously producing both eggs and cercariae. These studies emphasize the potential importance of neonatal and preadult snails in helping to maintain foci of S. mansoni infection in endemic areas.


Assuntos
Biomphalaria/parasitologia , Vetores de Doenças , Schistosoma mansoni/fisiologia , Esquistossomose mansoni/transmissão , Animais , Biomphalaria/crescimento & desenvolvimento , Camundongos , Fatores de Tempo
17.
Biochemistry ; 30(13): 3200-9, 1991 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-2009261

RESUMO

Room temperature circular dichroism (CD) and low temperature magnetic circular dichroism (MCD) spectra of air-oxidized and dithionite-reduced Azotobacter vinelandii ferredoxin I (FdI), a [( 4Fe-4S]2+/1+, [3Fe-4S]1+/0) protein, are reported. Unlike the CD of oxidized FdI, the CD of dithionite-reduced FdI exhibits significant pH dependence, consistent with protonation-deprotonation at or near the cluster reduced: the [3Fe-4S] cluster. The MCD of reduced FdI, which originates in the paramagnetic reduced [3Fe-4S]0 cluster, is also pH-dependent. Detailed studies of the field dependence and temperature dependence of the MCD of oxidized and reduced FdI, in the latter case at pH 6.0 and 8.3, are reported. The low-field temperature dependence of the MCD of oxidized FdI, which originates in the paramagnetic oxidized [3Fe-4S]1+ cluster, establishes the absence of a significant population of excited electronic states of this cluster up to 60 K. The low-field temperature dependence of the MCD of reduced FdI establishes that the ground-state manifold of the reduced [3Fe-4S]0 cluster possesses S greater than or equal to 2 at both pH 6.0 and 8.3. Analysis, assuming S = 2 and an axial zero-field splitting Hamiltonian, leads to D = -2.0 and -3.5 cm-1 at pH 6.0 and 8.3, respectively. The site of the (de)protonation affecting the spectroscopic properties of the [3Fe-4S] cluster remains unknown.


Assuntos
Azotobacter/metabolismo , Ferredoxinas/química , Dicroísmo Circular , Ferredoxinas/isolamento & purificação , Matemática , Conformação Proteica , Espectrofotometria , Termodinâmica
19.
Proc Natl Acad Sci U S A ; 87(2): 598-602, 1990 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-2153958

RESUMO

Azotobacter vinelandii ferredoxin I is a small protein that contains one [4Fe-4S] cluster and one [3Fe-4S] cluster. Recently the x-ray crystal structure has been redetermined and the fdxA gene, which encodes the protein, has been cloned and sequenced. Here we report the site-directed mutation of Cys-20, which is a ligand of the [4Fe-4S] cluster in the native protein, to alanine and the characterization of the protein product by x-ray crystallographic and spectroscopic methods. The data show that the mutant protein again contains one [4Fe-4S] cluster and one [3Fe-4S] cluster. The new [4Fe-4S] cluster obtains its fourth ligand from Cys-24, a free cysteine in the native structure. The formation of this [4Fe-4S] cluster drives rearrangement of the protein structure.


Assuntos
Azotobacter/genética , Ferredoxinas/genética , Genes Bacterianos , Mutação , Azotobacter/metabolismo , Espectroscopia de Ressonância de Spin Eletrônica , Ferro/análise , Modelos Moleculares , Dados de Sequência Molecular , Fixação de Nitrogênio/genética , Conformação Proteica , Espectrofotometria , Enxofre/análise , Difração de Raios X
20.
J Bacteriol ; 171(6): 3162-7, 1989 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-2722744

RESUMO

Flavodoxin and ferredoxin I have both been implicated as components of the electron transport chain to nitrogenase in the aerobic bacterium Azotobacter vinelandii. Recently, the genes encoding flavodoxin (nifF) and ferredoxin I (fdxA) were cloned and sequenced and mutants were constructed which are unable to synthesize either flavodoxin (DJ130) or ferredoxin I (LM100). Both single mutants grow at wild-type rates under N2-fixing conditions. Here we report the construction of a double mutant (DJ138) which does not synthesize either flavodoxin or ferredoxin I. When plated on ammonium-containing medium, this mutant had a very small colony size when compared with the wild type, and in liquid culture with ammonium, this double mutant grew three times slower than the wild type or single mutant strains. This demonstrated that there is an important metabolic function unrelated to nitrogen fixation that is normally carried out by either flavodoxin or ferredoxin. If either one of these proteins is missing, the other can substitute for it. The double mutant phenotype can now be used to screen site-directed mutant versions of ferredoxin I for functionality in vivo even though the specific function of ferredoxin I is still unknown. The double mutant grew at the same slow rate under N2-fixing conditions. Thus, A. vinelandii continues to fix N2 even when both flavodoxin and ferredoxin I are missing, which suggests that a third as yet unidentified protein also serves as an electron donor to nitrogenase.


Assuntos
Azotobacter/genética , Ferredoxinas/genética , Flavodoxina/genética , Flavoproteínas/genética , Genes Bacterianos , Fixação de Nitrogênio/genética , Azotobacter/crescimento & desenvolvimento , Proteínas de Bactérias/genética , Cromossomos Bacterianos/ultraestrutura , Clonagem Molecular , Eletroforese em Gel Bidimensional
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