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1.
Br J Surg ; 106(9): 1147-1155, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31233220

RESUMO

BACKGROUND: Colonic J pouch reconstruction has been found to be associated with a lower incidence of anastomotic leakage than straight anastomosis. However, studies on this topic are underpowered and retrospective. This randomized trial evaluated whether the incidence of anastomotic leakage was reduced after colonic J pouch reconstruction compared with straight colorectal anastomosis following anterior resection for rectal cancer. METHODS: This multicentre RCT included patients with rectal carcinoma who underwent low anterior resection followed by colorectal anastomosis. Patients were assigned randomly to receive a colonic J pouch or straight colorectal anastomosis. The main outcome measure was the occurrence of major anastomotic leakage. The incidence of global (major plus minor) anastomotic leakage and general complications were secondary outcomes. Risk factors for anastomotic leakage were identified by regression analysis. RESULTS: Of 457 patients enrolled, 379 were evaluable (colonic J pouch arm 190, straight colorectal arm 189). The incidence of major and global anastomotic leakage, and general complications was 14·2, 19·5 and 34·2 per cent respectively in the colonic J pouch group, and 12·2, 19·0 and 27·0 per cent in the straight colorectal anastomosis group. No statistically significant differences were observed between the two arms. In multivariable logistic regression analysis, male sex (odds ratio 1·79, 95 per cent c.i. 1·02 to 3·15; P = 0·042) and high ASA fitness grade (odds ratio 2·06, 1·15 to 3·71; P = 0·015) were independently associated with the occurrence of anastomotic leakage. CONCLUSION: Colonic J pouch reconstruction does not reduce the incidence of anastomotic leakage and postoperative complications compared with conventional straight colorectal anastomosis. Registration number NCT01110798 (http://www.clinicaltrials.gov).


Assuntos
Colo/cirurgia , Bolsas Cólicas , Procedimentos de Cirurgia Plástica , Neoplasias Retais/cirurgia , Reto/cirurgia , Grampeamento Cirúrgico , Idoso , Anastomose Cirúrgica/efeitos adversos , Anastomose Cirúrgica/métodos , Fístula Anastomótica/epidemiologia , Fístula Anastomótica/etiologia , Bolsas Cólicas/efeitos adversos , Feminino , Humanos , Incidência , Masculino , Pessoa de Meia-Idade , Procedimentos de Cirurgia Plástica/efeitos adversos , Procedimentos de Cirurgia Plástica/métodos , Grampeamento Cirúrgico/métodos
2.
G Chir ; 40(1): 20-25, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30771794

RESUMO

BACKGROUND: Anastomotic leakage (AL) is a dreaded major complication after colorectal surgery. There is no uniform definition of anastomotic dehiscence and leak. Over the years many risk factors have been identified (distance of anastomosis from anal verge, gender, BMI, ASA score) but none of these allows an early diagnosis of AL. The DUtch LeaKage (DULK) score, C reactive protein (CRP) and procalcitonin (PCT) have been identified as early predictors for anastomotic leakage starting from postoperative day (POD) 2-3. The study was designed to prospectively evaluate AL rates after colorectal resections, in order to give a definite answer to the need for clear risk factors, and testing the diagnostic yeld of DULK score and of laboratory markers. Methods and analysis. A prospective enrollment for all patients undergoing elective colorectal surgery with anastomosis carried out from September 2017 to September 2018 in 19 Italian surgical centers. OUTCOME MEASURES: preoperative risk factors of anastomotic leakage; operative parameters; leukocyte count, serum CRP, serum PCT and DULK score assessment on POD 2 and 3. Primary endpoint is AL; secondary endpoints are minor and major complications according to Clavien-Dindo classification; morbidity and mortality rates; readmission and reoperation rates, length of postoperative hospital stay (Retrospectively registered at ClinicalTrials.gov Identifier: NCT03560180, on June 18, 2018). Ethics. The ethics committee of the "Comitato Etico Regionale delle Marche - C.E.R.M." reviewed and approved this study protocol on September 7, 2017 (protocol no. 2017-0244-AS). All the participating centers submitted the protocol and obtained authorization from the local Institutional Review Board.


Assuntos
Fístula Anastomótica/diagnóstico , Proteína C-Reativa/análise , Colo/cirurgia , Pró-Calcitonina/sangue , Reto/cirurgia , Fístula Anastomótica/sangue , Biomarcadores/sangue , Diagnóstico Precoce , Procedimentos Cirúrgicos Eletivos/efeitos adversos , Humanos , Contagem de Leucócitos , Avaliação de Resultados em Cuidados de Saúde , Estudos Prospectivos , Fatores de Risco , Tamanho da Amostra , Deiscência da Ferida Operatória/complicações
3.
G Chir ; 40(4Supp.): 1-40, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-32003714

RESUMO

Enhanced Recovery After Surgery (ERAS) pathway is a multi-disciplinary, patient-centered protocol relying on the implementation of the best evidence-based perioperative practice. In the field of colorectal surgery, the application of ERAS programs is associated with up to 50% reduction of morbidity rates and up to 2.5 days reduction of postoperative hospital stay. However, widespread adoption of ERAS pathways is still yet to come, mainly because of the lack of proper information and communication. Purpose of this paper is to support the diffusion of ERAS pathways through a critical review of the existing evidence by members of the two national societies dealing with ERAS pathways in Italy, the PeriOperative Italian Society (POIS) and the Associazione Italiana Chirurghi Ospedalieri (ACOI), showing the results of a consensus development conference held at Matera, Italy, during the national ACOI Congress on June 10, 2019.


Assuntos
Cirurgia Colorretal , Consenso , Recuperação Pós-Cirúrgica Melhorada/normas , Sociedades Médicas , Comorbidade , Aconselhamento , Humanos , Itália , Cuidados Pré-Operatórios/métodos
4.
Tech Coloproctol ; 21(8): 633-640, 2017 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28755256

RESUMO

BACKGROUND: Rectum-sparing approaches appear to be appropriate in rectal cancer patients with a major (mCR) or complete clinical response (cCR) after neoadjuvant therapy. The aim of the present study is to evaluate the effectiveness of rectum-sparing approaches at 2 years after the completion of neoadjuvant treatment. STUDY DESIGN: Patients with rectal adenocarcinoma eligible to receive neoadjuvant therapy will be prospectively enrolled. Patients will be restaged 7-8 weeks after the completion of neoadjuvant therapy and those with mCR (defined as absence of mass, small mucosal irregularity no more than 2 cm in diameter at endoscopy and no metastatic nodes at MRI) or cCR will be enrolled in the trial. Patients with mCR will undergo local excision, while patients with cCR will either undergo local excision or watch and wait policy. The main end point of the study is to determine the percentage of rectum preservation at 2 years in the enrolled patients. CONCLUSION: This protocol is the first prospective trial that investigates the role of both local excision and watch and wait approaches in patients treated with neoadjuvant therapy for rectal cancer. The trial is registered at clinicaltrials.gov (NCT02710812).


Assuntos
Adenocarcinoma/terapia , Neoplasias Retais/terapia , Conduta Expectante , Adenocarcinoma/cirurgia , Quimiorradioterapia Adjuvante , Quimioterapia Adjuvante , Humanos , Terapia Neoadjuvante , Tratamentos com Preservação do Órgão , Período Pré-Operatório , Radioterapia Adjuvante , Neoplasias Retais/cirurgia , Reto , Projetos de Pesquisa
6.
Acta Chir Iugosl ; 57(3): 73-5, 2010.
Artigo em Inglês | MEDLINE | ID: mdl-21066988

RESUMO

In the last years a wide range of new technique offers the possibility to have R0 resection in colorectal cancer. We report our experience about Single Port Laparoscopic Surgery (SPL) for not advanced right colon cancer and about pelvectomy with cilindric Abdominal Perineal Resection (APR) for advanced rectal cancer. SPL offer mainly cosmetic advantages but also quicker recovery. No touch technique with adequate surgical margin and lymphectomy were respected. Operative time of SPL was 85-115 minutes, the incision was 5 cm long. There were no complications. Length of hospital stay was 4-6 days. With advanced pelvic cancer, pelvic exenteration with en-bloc resection is indicated. Then we propose a case of a 55 years old woman with a pelvic recurrence from a metastatic rectal cancer involving the right obturator fossa, the vaginal stump, the right ureter. Modern surgical technique give us the chance to offer the most appropriate oncologic surgical treatment.


Assuntos
Neoplasias Colorretais/cirurgia , Neoplasias Colorretais/patologia , Feminino , Humanos , Laparoscopia , Pessoa de Meia-Idade , Procedimentos Cirúrgicos Minimamente Invasivos , Exenteração Pélvica , Períneo/cirurgia
7.
Crit Rev Oncol Hematol ; 72(1): 65-75, 2009 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-19147371

RESUMO

Colorectal cancer (CRC) caused nearly 204,000 deaths in Europe in 2004. Despite recent advances in the treatment of advanced disease, which include the incorporation of two new cytotoxic agents irinotecan and oxaliplatin into first-line regimens, the concept of planned sequential therapy involving three active agents during the course of a patient's treatment and the integrated use of targeted monoclonal antibodies, the 5-year survival rates for patients with advanced CRC remain unacceptably low. For patients with colorectal liver metastases, liver resection offers the only potential for cure. This review, based on the outcomes of a meeting of European experts (surgeons and medical oncologists), considers the current treatment strategies available to patients with CRC liver metastases, the criteria for the selection of those patients most likely to benefit and suggests where future progress may occur.


Assuntos
Neoplasias Colorretais/patologia , Hepatectomia , Neoplasias Hepáticas/secundário , Neoplasias Hepáticas/cirurgia , Antineoplásicos/uso terapêutico , Ensaios Clínicos como Assunto , Neoplasias Colorretais/mortalidade , Terapia Combinada , Humanos , Terapia Neoadjuvante , Guias de Prática Clínica como Assunto
8.
Ann Oncol ; 20(5): 935-40, 2009 May.
Artigo em Inglês | MEDLINE | ID: mdl-19179550

RESUMO

BACKGROUND: Central venous access is extensively used in oncology, though practical information from randomized trials on the most convenient insertion modality and site is unavailable. METHODS: Four hundred and three patients eligible for receiving i.v. chemotherapy for solid tumors were randomly assigned to implantation of a single type of port (Bard Port, Bard Inc., Salt Lake City, UT), through a percutaneous landmark access to the internal jugular, a ultrasound (US)-guided access to the subclavian or a surgical cut-down access through the cephalic vein at the deltoid-pectoralis groove. Early and late complications were prospectively recorded until removal of the device, patient's death or ending of the study. RESULTS: Four hundred and one patients (99.9%) were assessable: 132 with the internal jugular, 136 with the subclavian and 133 with the cephalic vein access. The median follow-up was 356.5 days (range 0-1087). No differences were found for early complication rate in the three groups {internal jugular: 0% [95% confidence interval (CI) 0.0% to 2.7%], subclavian: 0% (95% CI 0.0% to 2.7%), cephalic: 1.5% (95% CI 0.1% to 5.3%)}. US-guided subclavian insertion site had significantly lower failures (e.g. failed attempts to place the catheter in agreement with the original arm of randomization, P = 0.001). Infections occurred in one, three and one patients (internal jugular, subclavian and cephalic access, respectively, P = 0.464), whereas venous thrombosis was observed in 15, 8 and 11 patients (P = 0.272). CONCLUSIONS: Central venous insertion modality and sites had no impact on either early or late complication rates, but US-guided subclavian insertion showed the lowest proportion of failures.


Assuntos
Antineoplásicos/administração & dosagem , Veias Braquiocefálicas , Cateterismo Venoso Central/métodos , Cateteres de Demora/efeitos adversos , Veias Jugulares , Neoplasias/tratamento farmacológico , Veia Subclávia , Idoso , Infecções Relacionadas a Cateter/etiologia , Infecções Relacionadas a Cateter/prevenção & controle , Cateterismo Venoso Central/efeitos adversos , Cateterismo Venoso Central/instrumentação , Falha de Equipamento , Feminino , Hemorragia/etiologia , Hemorragia/prevenção & controle , Humanos , Masculino , Pessoa de Meia-Idade , Pneumotórax/etiologia , Pneumotórax/prevenção & controle , Estudos Prospectivos , Veia Subclávia/diagnóstico por imagem , Fatores de Tempo , Falha de Tratamento , Ultrassonografia de Intervenção , Trombose Venosa/etiologia , Trombose Venosa/prevenção & controle
9.
Artigo em Inglês | MEDLINE | ID: mdl-22275967

RESUMO

Damage control is a surgical strategy for severely compromised trauma patients based on speed control of life-threatening injuries that aims to rapidly resuscitate patients in an intensive care unit (ICU). We report on the use of such therapeutic strategy in a patient affected by a retroperitoneal sarcoma concomitant to a horseshoe kidney, a relatively rare anatomical malformation.

10.
Artigo em Inglês | MEDLINE | ID: mdl-22275956

RESUMO

BACKGROUND/AIMS: Hepatic resection in metastatic disease from colorectal cancer offers the best chance in selected cases for long-term survival. Neoadjuvant chemotherapy (NACT) has been advocated in some cases initially deemed irresectable, with few reports of the efficacy of such a strategy and the influence of the response to chemotherapy on the outcome of radical hepatic resection. METHODOLOGY: Between December 1995 and May 2005, 27 patients with colorectal liver metastases (seven males, 20 females, mean age: 58 ± 8 years; range: 40-75) were treated with neoadjuvant chemotherapy. A seven-year survival analysis was performed. Chemotherapy included mainly 5-fluorouracil, leucovorin and either oxaliplatin or irinotecan for a median of eight courses. RESULTS: A total of 16 patients (59%) had synchronous and 11 (41%) metachronous metastases. During pre-operative chemotherapy, tumour regression occurred in ten cases (37%), stable disease in a further ten patients (37%) and progressive disease developed in seven cases (26%). The five-year overall survival for NACT responders was 64% and only 15% for non-responders (p=0.044). CONCLUSIONS: The response to chemotherapy is likely to be a significant prognostic factor affecting survival after liver resection for cure.

11.
Ann Oncol ; 15(2): 296-300, 2004 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-14760125

RESUMO

BACKGROUND: The complication rate of central venous totally implantable access ports (TIAP), used for high-dose chemotherapy with autologous stem cell transplantation support, has not been fully investigated to date, due to the almost exclusive use of externalised, tunnelled devices in this clinical setting. PATIENTS AND METHODS: During a 66-month period (from 1 January 1997 to 30 June 2002), 376 patients suffering from breast cancer, ovarian cancer, lymphoma or multiple myeloma were treated with high-dose chemotherapy and autologous stem cell transplantation at the European Institute of Oncology (Milan, Italy). A single type of port was used, constructed from titanium and silicone rubber, connected to a 7.8 F polyurethane catheter (Port-A-Cath; SIMS Deltec, Inc., St Paul, MN, USA) inserted into the subclavian vein. They were followed prospectively for device-related complications until the device was removed, the patient died or the study was closed (30 June 2002). RESULTS: No TIAP-related deaths were observed in this series. Seven pneumothoraxes (1.8%) occurred as a complication of TIAP placement, one patient only (0.2%) requiring a tube thoracostomy. Port pocket infection occurred twice in this series (0.53%, 0.01 episodes/1000 days of use), whereas three patients suffered from port-related bacteraemia (0.8%, 0.016/1000 days of use). Infections were successfully treated with antibiotics; all three cases had the ports removed at programme completion. Four cases of deep vein thrombosis were detected (1.06%, 0.022/1000 days of use); low molecular weight heparin was given, followed by oral anticoagulants. Finally, one case of extravasation occurred (0.26%, 0.005/1000 days of use), requiring port removal and local medical therapy. CONCLUSIONS: The use of TIAPs has resulted in a safe and effective option for high-dose chemotherapy deliverance and stem cell transplantation, in spite of inducing severe neutropenia and increasing the risk of sepsis in this category of oncology patient.


Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/efeitos adversos , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Cateterismo Venoso Central/efeitos adversos , Transplante de Células-Tronco de Sangue Periférico , Pneumotórax/etiologia , Adulto , Neoplasias da Mama/tratamento farmacológico , Feminino , Humanos , Infecções/etiologia , Linfoma/tratamento farmacológico , Masculino , Pessoa de Meia-Idade , Mieloma Múltiplo/tratamento farmacológico , Neoplasias Ovarianas/tratamento farmacológico , Estudos Prospectivos , Fatores de Risco
13.
Antisense Nucleic Acid Drug Dev ; 8(5): 415-26, 1998 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-9826268

RESUMO

External guide sequences (EGSs) are short oligoribonucleotides, which are designed to bind to a given RNA target and form a precursor tRNA-like complex. This complex can be recognized by ribonuclease P (RNase P), resulting in specific cleavage of the RNA target. To explore the potential of this class of compounds as therapeutic agents and valuable tools for gene function analysis, various chemical modifications were introduced into an all-RNA EGS molecule to confer nuclease resistance. In particular, 2'-O-methyl substitutions were incorporated into the entire sequence (i.e., A-stem, D-stem, and T-stem) except the T-loop region without loss of cleavage-inducing activity. Replacement of rU (position 54) and rC (position 56) in the T-loop with their 2'-O-methyl counterparts caused pronounced decrease in activity. Moreover, phosphorothioate backbone modification of the T-loop did not provide sufficient protection against endonucleolytic attack at the ribopyrimidine residues. Systematic modification of the T-loop with a variety of modified nucleosides and the addition of a 3'-3' inverted T at the 3'-end have generated several lead EGS prototypes, which not only exhibit wild-type activity in inducing RNase P-mediated target cleavage as compared with the all-RNA control but also remain intact in human serum for more than 24 hours. These results should provide useful insights into the design and development of oligonucleotide-based EGSs as potential regulators of gene expression.


Assuntos
Endorribonucleases/fisiologia , RNA Catalítico/fisiologia , RNA/metabolismo , Sequências Reguladoras de Ácido Nucleico/fisiologia , Sequência de Bases , Endorribonucleases/metabolismo , Humanos , Cinética , Dados de Sequência Molecular , Conformação de Ácido Nucleico/efeitos dos fármacos , Oligorribonucleotídeos/farmacologia , RNA Catalítico/metabolismo , Ribonuclease P
14.
Oncogene ; 17(14): 1759-68, 1998 Oct 08.
Artigo em Inglês | MEDLINE | ID: mdl-9778041

RESUMO

The t(15;17) rearrangement found in acute promyelocytic leukemia (APL) yields a fusion transcript, PML/RAR alpha. PML/RAR alpha expression is linked to leukemogenesis and to clinical sensitivity to all-trans retinoic acid (RA). Paradoxically, RA treatment causes transient complete remissions in most t(15;17) APL cases. The precise roles of PML/RAR alpha in triggering leukemia or in causing a maturation block are not yet known. This study explores directly these PML/RAR alpha functions in the growth and differentiation of APL cells using a hammerhead ribozyme to target PML/RAR alpha mRNA in the NB4 APL cell line. When the PML/RAR alpha cleaving but not the non-catalytic control ribozyme is introduced into the NB4 APL cell line, PML/RAR alpha protein expression is reduced. This catalysis signals growth suppression, cytotoxicity, and apoptosis without overcoming the maturation block found in these leukemic cells. These biologic effects depend on the selective pressure used to express the ribozyme from an episomal vector. Introduction of a non-catalytic, control ribozyme into NB4 cells caused no observed phenotype due to anti-sense activities. Expression of the catalytic or non-catalytic ribozymes in control cells lacking PML/RAR alpha mRNA yielded no apparent growth or differentiation effects. Thus, use of a hammerhead ribozyme that targets PML/RAR alpha expression in APL cells reveals the anti-apoptotic function of this translocation product and demonstrates that PML/RAR alpha cleavage is insufficient to overcome the differentiation block observed in these leukemic cells. Taken together, these findings indicate that persistent PML/RAR alpha expression is required to maintain basal leukemic cell growth and point to the therapeutic potential of targeting PML/RAR alpha in APL.


Assuntos
Apoptose , Leucemia Promielocítica Aguda , Proteínas de Neoplasias/metabolismo , Proteínas de Fusão Oncogênica/metabolismo , Transporte Biológico , Catálise , Divisão Celular , Sobrevivência Celular , Expressão Gênica , Humanos , Proteínas de Neoplasias/genética , Proteínas de Fusão Oncogênica/genética , RNA Catalítico/genética , RNA Catalítico/metabolismo , Transfecção , Células Tumorais Cultivadas
15.
Cancer Res ; 54(24): 6365-9, 1994 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-7987829

RESUMO

Acute promyelocytic leukemia (FAB M3) is distinguished by the presence of the t(15;17) and clinical response to all-trans retinoic acid (RA) treatment. Acute promyelocytic leukemia is associated with a chromosomal translocation which results in the fusion of genes encoding a putative transcription factor (PML) and the retinoic acid receptor alpha (RAR alpha). It is suggested that the PML/RAR alpha fusion protein functions as an inhibitor of myeloid differentiation. The potential use of ribozymes as therapeutic agents has been investigated in the present study. Hammerhead ribozymes, which by hybridizing to both PML and RAR alpha sequences discriminate between the fusion transcript and the normal transcripts from the nonrearranged alleles, were designed and synthesized. Two hammerhead cleavage sites were targeted: site 1, an AUU located 4 nucleotides 3' to the fusion junction; and site 2, a UUC located 26 nucleotides 3' to the junction. Both sites are located in the RAR alpha portion of the fusion transcript. Using a full-length PML/RAR alpha RNA or an RNA corresponding to 788 nucleotides of the PML/RAR alpha mRNA and a full-length RAR alpha RNA or an RNA corresponding to 960 nucleotides of the RAR alpha mRNA as model substrates, the catalytic behavior of several ribozymes was studied. A modified hammerhead directed against site 2 displayed the highest degree of selectivity for PML/RAR alpha. It is hypothesized that ribozyme-mediated inactivation of PML/RAR alpha provides a new approach to study the role of PML/RAR alpha in the deregulated growth and RA response of acute promyelocytic leukemia.


Assuntos
Leucemia Promielocítica Aguda/metabolismo , RNA Catalítico/metabolismo , RNA Mensageiro/metabolismo , Receptores do Ácido Retinoico/metabolismo , Fatores de Transcrição/metabolismo , Sequência de Bases , Cromossomos Humanos Par 15/genética , Cromossomos Humanos Par 17/genética , Humanos , Leucemia Promielocítica Aguda/genética , Dados de Sequência Molecular , Estrutura Secundária de Proteína , RNA Catalítico/química , RNA Catalítico/genética , Translocação Genética/genética
16.
Nucleic Acids Res ; 20(24): 6681-6, 1992 Dec 25.
Artigo em Inglês | MEDLINE | ID: mdl-1282703

RESUMO

We identified conditions for heating and quick cooling viroid RNAs in the presence of salt which lead to the production of conformational isomers stable to incubation for at least 45 minutes at 30 degrees in the presence of magnesium ions. Elution in 0.3 M NaCl allowed the purification of an electrophoretically slow form of an in vitro transcript carrying a complete copy of the potato spindle tuber viroid RNA sequence. Slow forms of this transcript and of kinase-labeled linear viroid RNA persisted for longer than 20 minutes when incubated with a protein-rich extract prepared from the nuclei of uninfected tomato plants, although both were slowly cleaved by a nuclease present in this extract. The fast form of the transcript was highly resistant to this tomato ribonuclease. The slow form of the transcript was much more susceptible to cleavage by RNase T1 than the fast form of this RNA, suggesting that the reduced gel mobility of the slow forms results from their relatively open structure. The ability to purify viroid conformational isomers from polyacrylamide gels will facilitate biochemical studies aimed at identifying host components interacting with RNAs of the viroid replication complex, which may not all be present in the most thermodynamically favored rodlike structure of mature viroids.


Assuntos
Magnésio/farmacologia , Conformação de Ácido Nucleico , Vírus de Plantas/genética , Plantas/microbiologia , RNA Viral/isolamento & purificação , RNA/isolamento & purificação , Viroides/genética , Núcleo Celular/metabolismo , Núcleo Celular/microbiologia , Enzimas de Restrição do DNA , Isomerismo , Vírus de Plantas/isolamento & purificação , RNA/química , RNA/genética , RNA Circular , RNA Viral/química , RNA Viral/genética , Ribonuclease T1 , Transcrição Gênica , Viroides/isolamento & purificação
17.
FEBS Lett ; 280(1): 171-4, 1991 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-2009960

RESUMO

The A-rich bulge in paired region P5a of the Tetrahymena intron is a structural feature that is conserved in the sub-group Ib self-splicing introns. We have constructed a series of substitution and deletion mutations in this region of the intron. Kinetic analysis has shown that some of the mutants have a reduced maximal extent of splicing, while others have a reduced Vmax. These mutations could be reactivated to a great extent by spermidine and high Mg2+ concentrations. These data are consistent with the hypothesis that the A-rich bulge of P5a has a role in stabilizing the higher-level structure of the ribozyme.


Assuntos
Íntrons , Splicing de RNA , RNA Catalítico/química , Tetrahymena/genética , Animais , Sequência de Bases , Cinética , Magnésio/metabolismo , Dados de Sequência Molecular , Mutagênese , Conformação de Ácido Nucleico , Espermidina/farmacologia , Tetrahymena/efeitos dos fármacos
18.
J Mol Biol ; 215(3): 345-58, 1990 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-1700131

RESUMO

We have constructed all single base substitutions in almost all of the highly conserved residues of the Tetrahymena self-splicing intron. Mutation of highly conserved residues almost invariably leads to loss of enzymatic activity. In many cases, activity could be regained by making additional mutations that restored predicted base-pairings; these second site suppressors in general confirm the secondary structure derived from phylogenetic data. At several positions, our suppression data can be most readily explained by assuming non-Watson-Crick base-pairings. In addition to the requirements imposed by the secondary structure, the sequence of the intron is constrained by "negative interactions", the exclusion of particular nucleotide sequences that would form undesirable secondary structures. A comparison of genetic and phylogenetic data suggests sites that may be involved in tertiary structural interactions.


Assuntos
Análise Mutacional de DNA , Íntrons , Splicing de RNA , Tetrahymena/genética , Animais , Sequência de Bases , Dados de Sequência Molecular , Testes de Mutagenicidade , Conformação de Ácido Nucleico , Filogenia , RNA/química , RNA Catalítico
19.
Biochem J ; 260(1): 121-6, 1989 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-2505747

RESUMO

Sucrose and other saccharides, which produce an appealing taste in rats, were found to significantly stimulate the activity of adenylate cyclase in membranes derived from the anterior-dorsal region of rat tongue. In control membranes derived from either tongue muscle or tongue non-sensory epithelium, the effect of sugars on adenylate cyclase activity was either much smaller or absent. Sucrose enhanced adenylate cyclase activity in a dose-related manner, and this activation was dependent on the presence of guanine nucleotides, suggesting the involvement of a GTP-binding protein ('G-protein'). The activation of adenylate cyclase by various mono- and di-saccharides correlated with their electrophysiological potency. Among non-sugar sweeteners, sodium saccharin activated the enzyme, whereas aspartame and neohesperidin dihydrochalcone did not, in correlation with their sweet-taste effectiveness in the rat. Sucrose activation of the enzyme was partly inhibited by Cu2+ and Zn2+, in agreement with their effect on electrophysiological sweet-taste responses. Our results are consistent with a sweet-taste transduction mechanism involving specific receptors, a guanine-nucleotide-binding protein and the cyclic AMP-generating enzyme adenylate cyclase.


Assuntos
Adenilil Ciclases/metabolismo , Dissacarídeos/farmacologia , Proteínas de Ligação ao GTP/fisiologia , Monossacarídeos/farmacologia , Papilas Gustativas/enzimologia , Animais , Ativação Enzimática/efeitos dos fármacos , Feminino , Masculino , Ratos , Ratos Endogâmicos , Transdução de Sinais , Sacarose/farmacologia , Edulcorantes/farmacologia , Papilas Gustativas/efeitos dos fármacos
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