RESUMO
BACKGROUND: There is to date no convincing literature that has assessed the association between traumatic spinal cord injury (SCI) and the later development of urinary bladder cancer. The aim of this work is to present medical experts as well as the national accident insurance and the social courts decision-making aids based on the latest medical scientific knowledge, for assessment of this causal association. MATERIALS AND METHODS: A study conducted between April 1998 and March 2017 in the BG Trauma Hospital Hamburg forms the basis for the decision-making aids. Urinary bladder cancer was diagnosed in 32 out of 6432 treated outpatient and inpatient SCI patients. Furthermore, relevant published literature was taken into consideration for the decision-making aids. RESULTS: It was found that urinary bladder cancer in SCI patients occurs at a considerably younger age as compared to the general population, more frequently shows muscle invasive carcinoma with a higher grade at first diagnosis and a higher proportion of the more aggressive squamous cell carcinoma than that of the general population. Correspondingly, the survival time is extremely unfavorable. For medical experts a matrix was compiled where the various influencing factors, either for or against the recognition of an association between SCI and urinary bladder cancer, were weighted according to their relevance. CONCLUSION: The results showed that urinary bladder cancer in SCI patients differs considerably from that of able-bodied patients. These differences drastically shorten the survival time. A study on patients with spina bifida, i.e., a congenital spinal cord disorder, corroborates these observations. They indicate histopathological differences that have so far been intangible.
Assuntos
Carcinoma de Células Escamosas/etiologia , Técnicas de Apoio para a Decisão , Traumatismos da Medula Espinal/complicações , Neoplasias da Bexiga Urinária/etiologia , Bexiga Urinária/patologia , Carcinoma de Células Escamosas/patologia , Progressão da Doença , Humanos , Neoplasias da Bexiga Urinária/patologiaRESUMO
Salmonellosis is an important disease in childhood. Increasing infections caused by meat and raw egg consumption starts in the second year of life. The transmission from reptiles to infants is an alternative route. Reptile-associated salmonellosis is becoming more significant for pediatricians and microbiologists due to the increasing numbers of household exotic pets. Investigations of routes of infections in connection with the local health authorities including microbiological, serological and molecular biological tests is possible in case of atypical salmonellosis. During recent years (2006-2008) an increasing number of salmonellosis cases caused by reptiles. Most of the 26 patients were infants of less than one year of age. Also Salmonella strains of subspecies II, IIIa, IIIb and IV play an important role. The US Centers for Disease Control and Prevention (CDC) has published recommendations which includes washing hands with soap and water after handling reptiles or the cages and keeping reptiles out of food preparation areas. The CDC has also adviced that children less than five years should not have reptiles as pets.
Assuntos
Animais Domésticos/microbiologia , Gastroenterite/microbiologia , Répteis/microbiologia , Infecções por Salmonella/transmissão , Salmonella enterica , Animais , Pré-Escolar , Estudos Transversais , Gastroenterite/epidemiologia , Gastroenterite/prevenção & controle , Alemanha , Humanos , Lactente , Lagartos/microbiologia , Infecções por Salmonella/epidemiologia , Infecções por Salmonella/prevenção & controle , Salmonella enterica/classificação , SorotipagemRESUMO
BACKGROUND: Although salmonellosis is one of the most common childhood illnesses associated with enteric bacteria, breastfed babies do not often get infected with Salmonella. In such cases it is therefore necessary to look carefully for the source of infection. PATIENT: It is reported an 8-week-old female infant with acute haemorrhagic diarrhoea and fever. With symptomatic therapy and breast-feeding her condition improved without antibiotic therapy. Microbiological diagnosis and subtyping identified infection with Salmonella enterica serovar Pomona. The source of the infection was a bearded dragon ( Pogona SPP.) living in a neighborhood household. Monitoring of the child showed shedding of the bacterium over a nine month period. CONCLUSION: In all cases of salmonellosis in breastfed babies, the source of infection should be carefully determined. Small numbers of bacteria can cause a symptomatic infection in this age group. Therefore an intensive search of the transmission route is indicated to develop prevention strategies.
Assuntos
Animais Domésticos/microbiologia , Aleitamento Materno , Gastroenterite/microbiologia , Répteis/microbiologia , Infecções por Salmonella/transmissão , Salmonella enterica , Animais , Escherichia coli , Fezes/microbiologia , Gastroenterite/terapia , Humanos , Lactente , Lagartos/microbiologia , Probióticos , Infecções por Salmonella/microbiologia , Infecções por Salmonella/terapia , Salmonella enterica/classificação , SorotipagemRESUMO
Gunshot injuries to the testicles are rare and usually result in testicular atrophy. In the case of severe bilateral testicular injuries, this could cause not only infertility but also the need for lifetime testosterone-substitution. We report an 18-year-old patient with bilateral testicular gunshot injury. During the surgical exploration an orchiectomy of the complete ruptured left testicle was necessary. Debridement of the damaged tissue and a partial orchiectomy was performed on the right side. After the operation, the patient developed an incretory hypogonadism and oligozoospermia. During follow-up, an improvement in the sperm count and of the hormonal status occurred. These finally reached normal levels. After genital traumata, immediate surgical exploration should be performed. Based on the above results, the patient benefits from conservative debridement and primary repair of the injured testicle, if possible. An improvement in hormonal status and sperm parameters after testicular injury and consecutive testicular malfunction can occur. Regeneration of the testicular tissue seems possible.
Assuntos
Orquiectomia/métodos , Testículo/lesões , Ferimentos por Arma de Fogo/cirurgia , Adolescente , Seguimentos , Humanos , Masculino , Complicações Pós-Operatórias/diagnóstico por imagem , Complicações Pós-Operatórias/etiologia , Regeneração/fisiologia , Contagem de Espermatozoides , Motilidade dos Espermatozoides/fisiologia , Testículo/diagnóstico por imagem , Testículo/fisiopatologia , Testosterona/sangue , Ultrassonografia , Ferimentos por Arma de Fogo/diagnóstico por imagemRESUMO
Usage of hydrogen breath tests has become one of the standard procedures in diagnosing chronic unspecific abdominal pain. These tests are said to be of sufficient specificity and sensitivity, are easily done, non-invasive and are more often practiced in outpatients. A 13-year-old boy is reported with chronic unspecific abdominal pain and growth retardation and so far misdiagnosed hereditary fructose intolerance (HFI), who developed life-threatening adverse effects during the fructose breath hydrogen test. It is concluded that the possibility of HFI should be excluded first by a carefully explored dietary history before the fructose breath test is performed under medical supervision. If there is any suspicion of HFI, a molecular genetic analysis should be preferred.
Assuntos
Dor Abdominal/diagnóstico , Testes Respiratórios , Intolerância à Frutose/diagnóstico , Frutose/efeitos adversos , Dor Abdominal/etiologia , Adolescente , Diagnóstico Diferencial , Frutose/metabolismo , Intolerância à Frutose/genética , Transtornos do Crescimento/etiologia , Transtornos do Crescimento/genética , Humanos , Masculino , Sensibilidade e EspecificidadeRESUMO
Two preliminary tests were conducted with piglets and chicken to study the influence of feeding ergot, which was specified concerning alkaloid content and pattern, on growth performance and health parameters. Treatments were 5 ergot concentrations in the diets (0; 0.05; 0.1; 0.2; 0.4%) which were fed to 5×16 piglets for 35 days and 5×28 chicken for 21 days. A content of 0.4% ergot in the diet decreased feed intake and growth performance of piglets significantly. Contents of 0.1% and 0.2% ergot in the diet showed a tendency towards improved weight gain as compared to controls. Feed to gain ratio was found to be the lowest in the group with 0.2% ergot in the diet. In the study conducted with chicken significant effects of ergot feeding on growth performance were not detected. With increased ergot concentrations in the diet the weight of hearts decreased, which proved to be significant only at a level of 0.2 % ergot in the diet. Moderate to severe inflammations were found in the proximal duodenum of the ergot fed groups, which, however, were not dosedependent. Further studies with ergot from other sources differing in alkaloid content and pattern are necessary to evaluate toxic alkaloid levels for the various animal species or categories.
RESUMO
The recent oral immunisation trials in wild boar against classical swine fever (CSF) in Germany are described and evaluated in summary. After the first field study in Lower Saxony from 1993-1995 further immunisation trials started in Mecklenburg-Western Pomerania, Brandenburg, Lower Saxony, Baden-Württemberg and Saxony-Anhalt. The immunisation strategies and the size of the vaccination zones were different in the individual federal states. In principle, the bait vaccine based on the CSF virus strain "C" were laid out by hand. Later also the aerial distribution was carried out in selected areas of Mecklenburg-Western Pomerania. The application of baits by plane was introduced at the beginning of the immunisation measures in Saxony-Anhalt apart from the manual distribution. Up to now, the field trials show that the oral immunisation can be an additional tool for CSF control by increasing of herd immunity and reduction of the CSFV prevalence. However, the immunisation was not sufficient enough for young boars in the most field studies. Based on the evaluation of the immunisation experiments an improved immunisation procedure is recommended.
Assuntos
Vírus da Febre Suína Clássica/imunologia , Peste Suína Clássica/prevenção & controle , Vacinação/veterinária , Vacinas Virais/administração & dosagem , Administração Oral , Animais , Animais Selvagens , Anticorpos Antivirais/sangue , Peste Suína Clássica/epidemiologia , Alemanha/epidemiologia , Estudos Soroepidemiológicos , SuínosRESUMO
HISTORY AND ADMISSION FINDINGS: A 27-year-old woman presented with increased bleeding tendency and known oculocutaneous albinism. In addition to frequent nasal and gingival bleedings she had since childhood spontaneous extensive cutaneous bleedings. In addition she was extreme sensitive to UV light with visual disturbances. Bone-marrow biopsy when aged 9 years had revealed abnormal pigment-storing cells. Physical examination showed a very fair skin and hair, spontaneous nystagmus and extensive rash in the face. INVESTIGATIONS: Prothrombin, partial thromboplastin and thrombin times as well as fibrinogen level were normal. On re- admission bleeding time varied greatly, while platelet count was normal. Mean platelet volume was slightly reduced. Von Willebrand antigen, factor VIII:C, factor IX:C, factor XIII and alpha (2)-antiplasmin were all normal. Aggregometry indicated abnormal platelet function; there was reduced platelet aggregation after stimulation with adenosine diphosphate. Flow cytometry of whole blood demonstrated abnormal storage function of thrombocytic delta-granules. The underlying cause of the described symptoms was shown to be a gene defect in typical location on the long arm of chromosome 10. DIAGNOSIS AND TREATMENT: The triad of tyrosinase-positive oculocutaneous albinism, abnormal thrombocytic delta-granules and ceroid deposition in the cells of the reticuloendothelial system or the bone-marrow is called Hermansky-Pudlak syndrome (after those who first reported it). There is as yet no causal treatment. But the patient was advised to use a nasal spray of desmopressin for spontaneous or difficult to stop bleedings after minor injuries. Desmopressin i. v. should be given prophylactically before any operation.
Assuntos
Síndrome de Hermanski-Pudlak/diagnóstico , Adulto , Testes de Coagulação Sanguínea , Feminino , Citometria de Fluxo , Síndrome de Hermanski-Pudlak/sangue , Humanos , Agregação PlaquetáriaRESUMO
BACKGROUND: : There is an increasing interest concerning the treatment of patients with personality disorders (PD) in data on the efficacy of psychotherapeutic strategies especially when combined with medication. METHODS: The efficacy of an inpatient client-centered treatment program (CCT) was studied prospectively in 142 patients with PD and additional depressive, anxiety or eating disorders (ICD-10). RESULTS: Significant improvements in depression, self-esteem and social adjustment were achieved up to discharge, which remained stable at the 1-year follow-up. The efficacy with regard to individual variables or the total result could not be further enhanced by a combination with psychopharmacological treatment (CCT + MED), consisting mainly of antidepressants. Within the subgroups of patients with socially deviant (F60.0-2), emotionally unstable/borderline (F60.3) and histrionic/narcissistic PD (F60.4, F60.8), CCT was significantly superior to CCT + MED in the reduction of depression (Bech-Rafaelsen Melancholia Scale ratings), whereas the response was enhanced by medication in the subgroup of patients with socially dependent 'cluster C' PD (F60.5-7). CONCLUSIONS: The results are discussed with regard to client-centered therapeutic concepts and to the further development of differential combination strategies.
Assuntos
Transtornos da Personalidade/terapia , Psicoterapia/métodos , Adulto , Análise de Variância , Ansiolíticos/uso terapêutico , Antidepressivos/uso terapêutico , Terapia Combinada , Feminino , Seguimentos , Humanos , Masculino , Transtornos da Personalidade/tratamento farmacológico , Transtornos da Personalidade/psicologia , Escalas de Graduação Psiquiátrica , Resultado do TratamentoRESUMO
The serum concentrations of beta-hydroxybutyrate and acetoacetate as well as the beta-hydroxybutyrate/acetoacetate ratio are important parameters for the differential diagnosis of certain inborn errors of metabolism. Acetoacetate, however, is an unstable compound which becomes rapidly decarboxylated. At a storage temperature of -20 degrees C about 40% of the acetoacetate is lost within 7 days and after 40 days storage at this temperature virtually all of the acetoacetate has become degraded. At -80 degrees C the decomposition of acetoacetate occurs with a much slower rate and only 15% of the initial acetoacetate is lost after 40 days storage. The rate constants for the decarboxylation reaction were found to be (6.4 +/- 2.9) * 10(-5) [min(-1)] at -20 degrees C and (0.4 +/- 0.3) * 10(-5) [min(-1)] at -80 degrees C. In contrast, beta-hydroxybutyrate is very stable during storage and hence should be used as main parameter for the evaluation of ketonemia. If determination of acetoacetate and/or of the beta-hydroxybutyrate/acetoacetate ratio is necessary, an assay immediately after collecting the serum samples is recommended. Otherwise, the serum samples should be frozen as soon as possible and stored at -80 degrees C during transport and storage.
Assuntos
Preservação de Sangue , Corpos Cetônicos/sangue , Ácido 3-Hidroxibutírico/sangue , Acetoacetatos/sangue , Criança , Criopreservação , Feminino , Humanos , Cetose/sangue , Cetose/diagnóstico , Cinética , Masculino , Kit de Reagentes para Diagnóstico/normas , Temperatura , Fatores de TempoRESUMO
This experiment aimed to investigate the influence of folic acid supplements on the carry-over of folates from the sow to the fetus during late gestation and to the suckling piglet. Two groups of sixteen German Landrace sows received, during gestation and lactation, a diet supplemented with either 0 or 10 mg folic acid/kg. Increased folic acid concentrations in the serum of sows were detected only at the end of gestation (day 100) and at the end of lactation (day 28). The supplementation with folic acid to the sows' diet improved the folic acid supply of the fetus compared with unsupplemented controls; values were respectively 92.6 v. 56.2 nmol folates/l serum in newborn piglets and 171.9 v. 76.3 micromol folates/g fresh liver in stillborn piglets (P < 0.05). Folate concentrations in colostrum and milk (day 28) were 3.6- and 5.0-times higher in supplemented than unsupplemented sows. This treatment effect was also reflected in the serum of piglets until weaning. Therefore, the folic acid supply for the suckling piglet is dependent mainly upon the carry-over of maternal folates via colostrum and milk.
Assuntos
Suplementos Nutricionais , Ácido Fólico/metabolismo , Troca Materno-Fetal/fisiologia , Suínos/fisiologia , Animais , Animais Recém-Nascidos/sangue , Animais Lactentes/sangue , Colostro/química , Feminino , Modelos Lineares , Masculino , Leite/química , GravidezRESUMO
Ferredoxins are small iron sulfur proteins necessary for electron donation. FdxH1 and FdxH2 are associated with two different nif gene clusters where they transfer electrons for the reduction of nitrogenase complex. FdxH1 was observed to be stable towards oxygen, whereas, FdxH2 was relatively unstable. We had identified the amino acid involved in oxygen sensitivity of ferredoxin protein using protein modeling. The exchange of valine to leucine at position 77 was critical for ferredoxin proteins in relation to its oxygen sensitivity. This exchange leads to a longer side chain, which inhibits the accessibility of oxygen to the iron sulfur cluster. Site directed mutagenesis and in vitro experiments confirms that valine indeed is involved in the oxygen sensitivity. The exchange of leucine to valine in FdxH1 makes it oxygen unstable. Thus, from the above results we can conclude that the position of leucine at position 77 is critical for oxygen sensitivity of ferredoxin and protein modeling can be used to identify specific amino acids in other oxygen-sensitive proteins.
Assuntos
Anabaena/química , Ferredoxinas/química , Oxigênio/farmacologia , Valina/química , Substituição de Aminoácidos , Simulação por Computador , Grupo dos Citocromos c/metabolismo , Elétrons , Ferredoxinas/metabolismo , Leucina/química , Modelos Moleculares , Mutagênese Sítio-Dirigida , NADP/metabolismo , Oxirredução , Conformação Proteica , Engenharia de ProteínasRESUMO
The mechanisms of change due to different psychotherapeutic treatments of anxiety disorders are the subject of the present study. Sixty-eight patients with agoraphobia and panic (DSM III R No. 300.21, ICD 10 No. F 40.01) were included, exclusively treated with client-centered treatment (n = 28) or with additional behavioral exposure treatment (n = 40) in an inpatient setting. The patients were examined on admission, at discharge, and at 6 and 12 months follow-ups with the Structured Clinical Interview for DSM III R (SKID), the Freiburg Personality Inventory (FPI R), and the Giessen Test (GIESS). Both treatment modalities significantly reduced panic and avoidance. Differences were found in personality scales. The support of autonomy was superior by client-centered treatment alone: client-centered treated (CCT) patients felt less dependent on the expectations of others, less under stress, and had fewer psychosomatic complaints. Patients with additional exposure treatment feel accepted by their social environment earlier. The results are discussed with regard to open questions of therapy integration and different mechanisms of change.
Assuntos
Agorafobia/terapia , Dessensibilização Psicológica , Transtorno de Pânico/terapia , Psicoterapia Centrada na Pessoa , Adulto , Agorafobia/diagnóstico , Agorafobia/psicologia , Terapia Combinada , Feminino , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Transtorno de Pânico/diagnóstico , Transtorno de Pânico/psicologia , Estudos Prospectivos , Escalas de Graduação Psiquiátrica , Resultado do TratamentoRESUMO
During the last few years, animal nutrition has been confronted with genetically modified organisms (GMO), and their significance will increase in the future. The study presents investigations on the substantial equivalence of the transgenic Bt (Bacillus thuringiensis) corn and the corresponding nontransgenic hybrid Cesar and parameters of nutrition physiology such as digestibility and energy content for poultry, pigs and ruminants. The results of the analysed corn samples as well as of the silage samples illustrated substantial equivalence in all investigated ingredients, such as crude nutrients, amino acids, fatty acids, minerals and non-starch polysaccharides. The results of the experiments using poultry, pigs, wethers and fattening bulls were not influenced by the genetic modification of corn. The determined values for the digestibilities and the energy contents for poultry, pigs and wethers were not affected by the used corn variety. Neither the examined parameters of the fattening experiments with bulls nor the slaughter results showed any significant differences between the bulls fed on silages made from the nontransgenic or transgenic corn.
Assuntos
Ração Animal/análise , Bacillus thuringiensis/genética , Galinhas/metabolismo , Plantas Geneticamente Modificadas/metabolismo , Ruminantes/metabolismo , Suínos/metabolismo , Zea mays/genética , Fenômenos Fisiológicos da Nutrição Animal , Animais , Bovinos/metabolismo , Digestão , Metabolismo Energético , Feminino , Masculino , Controle Biológico de Vetores , Ovinos/metabolismoRESUMO
To analyse substantial equivalence of genetically modified sugar-beets and maize, in which the glufosinate-tolerant (Pat) gene is inserted, crude nutrients, the amino acid and the fatty acid profiles as well as the composition of the NDF-fraction of maize grains were determined and compared with those of the corresponding non-transgenic cultivars. Due to the genetic manipulation differences in crude nutrient contents including sugar and starch were not detected. The amino acid profile of maize grains was analysed to be the same. Fatty acid profile and composition of cell wall constituents did not show any influences as well. Digestibility of Pat-sugar-beets and maize grains for pigs did not demonstrate meaningful differences as compared to the corresponding non-transgenic cultivars. Digestibility of sugar-beet roots and sugar-beet top silage for ruminants proved to be also in the scope of natural variance. As the digestibility of the macro nutrients remained unaffected, the Pat-gene introduction into both crops did not show an influence on the energetic feeding value. For pigs the ME-content of Pat-sugar-beets was determined to be 14.1 MJ/kg DM versus 13.7 MJ of the non-transgenic cultivars. ME-content of Pat-maize grains was 16.0 MJ/kg DM versus 15.8 MJ for controls. For ruminants the feeding value of Pat-sugar-beets was found to be 8.5 MJ NEL/kg DM or 13.2 MJ ME/kg DM, regardless of whether the Pat-gene was inserted or not. The corresponding energy values of sugar-beet top silage ranged between 5.2 and 5.5 MJ NEL/kg DM or 8.6 and 9.1 MJ ME/kg DM, with differences considered in the biological range.
Assuntos
Aminobutiratos/farmacologia , Ração Animal/análise , Herbicidas/farmacologia , Plantas Geneticamente Modificadas/efeitos dos fármacos , Ovinos/metabolismo , Suínos/metabolismo , Aminoácidos/análise , Fenômenos Fisiológicos da Nutrição Animal , Animais , Beta vulgaris/genética , Detergentes , Fibras na Dieta/análise , Digestão , Metabolismo Energético , Ácidos Graxos/análise , Zea mays/genéticaRESUMO
The nitrite reductase gene (nirA) from the filamentous, heterocyst-forming cyanobacterium Anabaena sp. PCC 7120 (A. PCC 7120) was expressed in Escherichia coli using the pET-system. Co-expression of the cysG gene encoding siroheme synthase of Salmonella typhimurium increased the amount of soluble, active nitrite reductase four fold. Nitrite reductase was purified to homogeneity. In order to identify amino acid residues involved in ferredoxin (PetF)-nitrite reductase electron transfer in A. PCC 7120, we performed a sequence comparison between ferredoxin-dependent nitrite reductases from various species. The alignment revealed a number of conserved residues possibly involved in ferredoxin nitrite reductase interaction. The position of these residues relative to the [4Fe4S]-cluster as the primary electron acceptor was tentatively localized in a three dimensional structure of the sulfite reductase from E. coli, which is closest related to nitrite reductase among the proteins with known tertiary structure. The exchange of certain positively charged amino acid residues of the nitrite reductase with uncharged residues revealed the influence of these residues on the interaction of nitrite reductase with reduced ferredoxin. We identified at least two separate regions of nitrite reductase that contribute to the binding of ferredoxin.
Assuntos
Aminoácidos/análise , Anabaena/enzimologia , Proteínas de Bactérias/metabolismo , Proteínas de Transporte , Ferredoxinas/metabolismo , Nitrito Redutases/metabolismo , Sequência de Aminoácidos , Substituição de Aminoácidos , Anabaena/genética , Proteínas de Bactérias/química , Sequência de Bases , Sítios de Ligação , Transporte de Elétrons , Ferredoxinas/química , Mutagênese Sítio-Dirigida , Mutação , Nitrito Redutases/química , Nitrito Redutases/isolamento & purificaçãoRESUMO
The method using transvers retubularized segment of ileum as an efferent conduit in Hautmann's neobladder is easy to perform and it can be repeated in revision procedures. We performed the procedure in nine patients who underwent radical cystectomy. At 8-16 months after operation, the resulting stomas were easy to catheterize. Of the nine patients, eight were continent. We find the procedure to be a good alternative when the appendix is absent and a cutaneous stoma is needed. It could be the preferred method in ileal neobladders with cutaneous outlet.
Assuntos
Neoplasias da Bexiga Urinária/cirurgia , Derivação Urinária/métodos , Feminino , Humanos , Íleo/cirurgia , Masculino , Reoperação , Técnicas de Sutura , Cateterismo UrinárioRESUMO
A 10-kb DNA region of the cyanobacterium Anabaena variabilis ATCC 29413 containing the structural genes of the uptake hydrogenase (hupSL) was cloned and sequenced. In contrast to the hupL gene of Anabaena sp. strain PCC 7120, which is interrupted by a 10.5-kb DNA fragment in vegetative cells, there is no programmed rearrangement within the hupL gene during the heterocyst differentiation of A. variabilis. The hupSL genes were transcribed as a 2.7-kb operon and were induced only under nitrogen-fixing conditions, as shown by Northern blot experiments and reverse transcriptase PCR. Primer extension experiments with a fluorescence-labeled oligonucleotide primer confirmed these results and identified the 5' start of the mRNA transcript 103 bp upstream of the ATG initiation codon. A consensus sequence in the promoter that is recognized by the fumarate nitrate reductase regulator (Fnr) could be detected. The hupSL operon in A. variabilis was interrupted by an interposon deletion (mutant strain AVM13). Under N(2)-fixing conditions, the mutant strain exhibited significantly increased rates in H(2) accumulation and produced three times more hydrogen than the wild type. These results indicate that the uptake hydrogenase is catalytically active in the wild type and that the enzyme reoxidizes the H(2) developed by the nitrogenase. The Nif phenotype of the mutant strain showed a slight decrease of acetylene reduction compared to that of the wild type.
Assuntos
Anabaena/enzimologia , Análise Mutacional de DNA , Oxirredutases/genética , Oxirredutases/metabolismo , Transcrição Gênica , Sequência de Aminoácidos , Anabaena/genética , Anabaena/crescimento & desenvolvimento , Sequência de Bases , Southern Blotting , Clonagem Molecular , Regulação Bacteriana da Expressão Gênica , Genes Bacterianos/genética , Hidrogênio/metabolismo , Dados de Sequência Molecular , Nitrogenase/metabolismo , Regiões Promotoras GenéticasRESUMO
The filamentous cyanobacterium Anabaena variabilis (ATCC 29413) possesses two molybdenum dependent nitrogenase systems, nif1 and nif2. The nif1 system is regulated by a developmental program involving heterocyst differentiation; the nif2 system is expressed in all cells only under anaerobic conditions and the expression is controlled environmentally. The genes fdxH1 and fdxH2, encoding two [2Fe-2S] ferredoxins, are part of the these two distinct and differently regulated nif gene clusters. The sensitivity of both ferredoxins to oxygen was different; the half-life of FdxH2 in air was only approximately 1.5 h, while FdxH1 retained 80% of its nitrogenase activity after 24 h. We used site-directed mutagenesis to identify the role of individual amino acid residues responsible for oxygen sensitivity and found out that the FdxH2 double mutant I76A/V77L was much more resistant to oxygen than the wild-type ferredoxin (FdxH2) and similar to FdxH1. By modelling it was shown that the accessibility of the cavity around the iron-sulfur cluster was responsible for that.