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1.
J Natl Compr Canc Netw ; : 1-6, 2024 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-39079545

RESUMO

BACKGROUND: Mohs micrographic surgery (MMS) is a promising treatment modality for melanoma in situ (MIS). However, variations in surgical technique limit the generalizability of existing data and may impede future study of MMS in clinical trials. METHODS: A modified Delphi method was selected to establish consensus on optimal MMS techniques for treating MIS in future clinical trials. The Delphi method was selected due to the limited current data, the wide range of techniques used in the field, and the intention to establish a standardized technique for future clinical trials. A literature review and interviews with experienced MMS surgeons were performed to identify dimensions of the MMS technique for MIS that (1) likely impacted costs or outcomes of the procedure, and (2) showed significant variability between surgeons. A total of 8 dimensions of technical variation were selected. The Delphi process consisted of 2 rounds of voting and commentary, during which 44 expert Mohs surgeons across the United States rated their agreement with specific recommendations using a Likert scale. RESULTS: Five of eight recommendations achieved consensus in Round 1. All 3 of the remaining recommendations achieved consensus in Round 2. Techniques achieving consensus in Round 1 included the use of a starting peripheral margin of ≤5 mm, application of immunohistochemistry, frozen tissue processing, and resecting to the depth of subcutaneous fat. Consensus on the use of Wood's lamp, dermatoscope, and negative tissue controls was established in Round 2. CONCLUSIONS: This study generated 8 consensus recommendations intended to offer guidance for Mohs surgeons treating MIS. The adoption of these recommendations will promote standardization to facilitate comparisons of aggregate data in multicenter clinical trials.

2.
Ann Transl Med ; 12(3): 54, 2024 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-38911557

RESUMO

Background: Basal cell carcinoma (BCC) is the most common cancer type worldwide. Although there are several treatment options for the treatment of BCC, selecting the best treatment option for periorbital BCC is challenging and it varies case by case. More than half of periocular BCC cases initially occur on the inner angle and lower lid. The treatment options for BCC include radical surgical excision using Mohs micrographic technique, radiotherapy, neoadjuvant vismodegib, imiquimod, and combination therapy followed by reconstruction for functionality and aesthetic outcome. Selection of each treatment varies based on the severity and extension of BCC. Case Description: We report a case of periorbital BCC invading the left lower eyelid in a 50-year-old Caucasian male which was initially excised a few years ago, and, following recurrence, the patient underwent Mohs micrographic surgery. Due to a recurrence after Mohs micrographic surgery, treatment with oral vismodegib was started, which led to near-total tumor shrinkage. To determine the outcome of periorbital BCC treated with vismodegib, we reviewed the literature on the periorbital BCC treated with vismodegib, their follow-up period, outcome, and whether they were metastatic or had recurrence. Conclusions: Neoadjuvant vismodegib, followed by surgery excision, such as Mohs micrographic surgery, has shown a promising clinical and aesthetic outcome in the treatment of periorbital BCC.

3.
Sci Rep ; 13(1): 19044, 2023 11 03.
Artigo em Inglês | MEDLINE | ID: mdl-37923759

RESUMO

Approximately 9000 years ago at the Andean highland site of Wilamaya Patjxa, forager communities interred female and male individuals with projectile points, suggesting that large-mammal hunting may have been a gender neutral activity among that community. We report a lithic usewear analysis, which confirms that the ostensible projectile points were indeed used as projectile points. The data further reveal evidence of cutting and hide scraping consistent with animal processing activities. A new radiocarbon date shows that the female and male individuals were contemporaries, or nearly so, sometime between 9.0 and 8.7 cal. ka. These findings support a model of early subsistence practices in which both female and male individuals at Wilamaya Patjxa hunted large mammals.


Assuntos
Arqueologia , Mamíferos , Animais , Humanos , Masculino , Feminino , Fósseis
5.
Am J Surg ; 225(1): 168-179, 2023 01.
Artigo em Inglês | MEDLINE | ID: mdl-35927089

RESUMO

BACKGROUND: Appendectomy is a benchmark operation for trainee progression, but this should be weighed against patient safety and perioperative outcomes. METHODS: Systematic literature review and meta-analysis comparing outcomes of appendectomy performed by trainees versus trained surgeons. RESULTS: Of 2086 articles screened, 29 studies reporting on 135,358 participants were analyzed. There was no difference in mortality (Odds ratio [OR] 1.08, P = 0.830), overall complications (OR 0.93, P = 0.51), or major complications (OR 0.56, P = 0.16). There was no difference in conversion from laparoscopic to open surgery (OR 0.81, P = 0.12) and in intraoperative blood loss (Mean Difference [MD] 5.58 mL, P = 0.25). Trainees had longer operating time (MD 7.61 min, P < 0.0001). Appendectomy by trainees resulted in shorter duration of hospital stay (MD 0.16 days, P = 0.005) and decreased reoperation rate (OR 0.78, P = 0.05). CONCLUSIONS: Appendectomy performed by trainees does not compromise patient safety. Due to statistical heterogeneity, further randomized controlled trials, with standardized reported outcomes, are required.


Assuntos
Apendicite , Laparoscopia , Cirurgiões , Humanos , Apendicectomia/métodos , Tempo de Internação , Reoperação , Apendicite/cirurgia , Complicações Pós-Operatórias/epidemiologia , Complicações Pós-Operatórias/cirurgia
6.
Pediatr Surg Int ; 38(9): 1187-1196, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-35857086

RESUMO

Appendicectomy is a common pediatric surgical procedure performed by trainees and surgeons with varying reported outcomes. It is a benchmark procedure for trainee progression and training benefits should be weighed against patient safety and perioperative outcomes. This systematic review and meta-analysis investigated any differential perioperative outcomes dependent on the grade of the operating surgeon. A systematic literature review and meta-analysis were performed comparing outcomes of pediatric appendicectomy performed by trainees versus trained surgeons. Of 2,086 articles screened, 5 retrospective non-randomized comparative studies reporting on 10,019 participants were analyzed. There was no difference in overall complications (OR 0.92; 95% CI 0.76, 1.12; P = 0.42), major complications [Clavien-Dindo (CD) III/IV] (OR 1.18; 95% CI 0.71, 1.97; P = 0.52), minor complications (CD I/II) (OR 1.13; 95% CI 0.57, 2.27; P = 0.72), post-op ileus (OR 0.74; 95% CI 0.10, 5.26; P = 0.76), wound infections (OR 0.87; 95% CI 0.62, 1.21; P = 0.41), abscess formation (OR 0.58; 95% CI 0.28, 1.22; P = 0.15), operation times [Mean Difference (MD) 2.31 min; 95% CI - 4.94, 9.56; P = 0.53] and reoperation rate (OR 1.22; 95% CI 0.23, 6.42; P = 0.81). Trainees had fewer conversions to open appendicectomy (OR 0.14; 95% CI 0.02, 0.88; P = 0.04). Appendicectomy performed on pediatric patients by trainees did not compromise patient safety. LEVEL OF EVIDENCE: III.


Assuntos
Laparoscopia , Cirurgiões , Apendicectomia/métodos , Criança , Humanos , Laparoscopia/métodos , Duração da Cirurgia , Complicações Pós-Operatórias/epidemiologia , Estudos Retrospectivos
7.
Cureus ; 14(4): e24147, 2022 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-35573491

RESUMO

BACKGROUND: Dermatofibrosarcoma protuberans (DFSP) is an uncommon, locally aggressive malignancy with wide local excision (WLE) or Mohs micrographic surgery (MMS) representing the treatment of choice. This article illustrates the experience of a single academic institution in treating DFSP with MMS and adds two particularly large, difficult closures of the glabella/central forehead and sternum to the body of literature. OBJECTIVE: To report the results of 15 patients with DFSP treated with MMS over a five-year period by a single Mohs surgeon at the University of Arkansas for Medical Sciences (UAMS). METHODS: A total of 15 patients between the ages of 16 and 80 years were diagnosed with DFSP and treated with MMS and were contacted in October 2021 to assess for recurrence. RESULTS: None of the 15 patients had a recurrence of DFSP following MMS, with a mean follow-up interval of 22.4 months and an average of 1.93 Mohs layers required for tumor clearance. CONCLUSION: This experience reaffirms that MMS is an effective treatment for DFSP and adds additional examples of closure techniques of large, ovoid surgical defects on the glabella/central forehead and sternum to the literature.

8.
Dermatol Online J ; 28(1)2022 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-35499420

RESUMO

Basal cell carcinoma (BCC) development in the context of a piercing is a rare phenomenon, reported in the literature in only six instances. We present a 55-year-old woman with nodular BCC involving her auricular piercing and extending clinically onto the posteroinferior right ear lobule and right post-auricular crease. Histological analysis revealed spread of the BCC through the piercing onto the anterior lobule, with evidence that the cancer utilized the piercing as a low resistance pathway for this microscopic invasion. This case is, to our knowledge, the first report of microscopic BCC present within an auricular piercing itself. Chronic inflammation related to repeated trauma from the embedded jewelry may have played a role in its formation. A piercing may provide a path of least resistance for BCC tumor cells to invade, providing a nidus for recurrence. Careful histological examination with possible complete excision of the piercing is prudent to prevent cancer return.


Assuntos
Piercing Corporal , Carcinoma Basocelular , Técnicas Cosméticas , Neoplasias Cutâneas , Piercing Corporal/efeitos adversos , Carcinoma Basocelular/etiologia , Carcinoma Basocelular/patologia , Feminino , Humanos , Pessoa de Meia-Idade , Neoplasias Cutâneas/etiologia , Neoplasias Cutâneas/patologia
9.
Int J Colorectal Dis ; 37(1): 47-69, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34697662

RESUMO

PURPOSE: There is no consensus in the literature regarding the association between operative blood loss and postoperative outcomes in colorectal surgery, despite evidence suggesting a link. Therefore, this systematic review assesses the association between operative blood loss, perioperative and long-term outcomes after colorectal surgery. METHODS: A literature search of MEDLINE, EMBASE, Science Citation Index Expanded and Cochrane was performed to identify studies reporting on operative blood loss in colorectal surgery. RESULTS: The review included forty-nine studies reporting on 61,312 participants, with a mean age ranging from 53.4 to 78.1 years. The included studies demonstrated that major operative blood loss was found to be a risk factor for mortality, anastomotic leak, presacral abscess, and postoperative ileus, leading to an increased duration of hospital stay. In the long term, the studies suggest that significant blood loss was an independent risk factor for future small bowel obstruction due to colorectal cancer recurrence and adhesions. Studies found that survival was significantly reduced, whilst the risk of colorectal cancer recurrence was increased. Reoperation and cancer-specific survival were not associated with major blood loss. CONCLUSION: The results of this systematic review suggest that major operative blood loss increases the risk of perioperative adverse events and has short and long-term repercussions on postoperative outcomes. Laparoscopic and robotic surgery, vessel ligation technology and anaesthetic considerations are essential for reducing blood loss and improving outcomes. This review highlights the need for further high quality, prospective, multicentre trials with a greater number of participants, and accurate and standardised methods of measuring operative blood loss.


Assuntos
Cirurgia Colorretal , Procedimentos Cirúrgicos do Sistema Digestório , Laparoscopia , Idoso , Perda Sanguínea Cirúrgica , Cirurgia Colorretal/efeitos adversos , Humanos , Laparoscopia/efeitos adversos , Pessoa de Meia-Idade , Duração da Cirurgia , Complicações Pós-Operatórias/etiologia , Estudos Prospectivos
10.
J Vis Exp ; (161)2020 07 16.
Artigo em Inglês | MEDLINE | ID: mdl-32744527

RESUMO

Beachgoers in the United States face many different hazards, but rip currents are annually the deadliest for ocean swimmers. Despite the risk presented by rip currents, it is apparent that the public has a limited understanding of their danger and the proper mitigating actions to take when caught in one. A virtual reality (VR) video game placing participants in a simulated rip current was developed to help ameliorate this issue. The VR game was used to survey beachgoers on the Atlantic Coast of Long Island, New York during July and August 2019. The actions participants took when confronted with the rip current were recorded, along with whether they escaped it or drowned. An interview with each player was also conducted after they partook in the game to determine the realism of the rip current simulation and its effectiveness in demonstrating proper actions to take when impacted by one. Analysis of those results indicates that VR has potential to communicate rip current risk and ways to minimize it in a unique and engaging manner. However, further work is needed to improve ease of use of the VR simulation and better understand how factors such as demographics influence perceived rip current risk and behavioral response.


Assuntos
Jogos de Vídeo/psicologia , Realidade Virtual , Ciclo Hidrológico , Feminino , Humanos , Masculino
13.
J Am Acad Dermatol ; 82(3): 700-708, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31756403

RESUMO

BACKGROUND: Opioid overprescribing is a major contributor to the opioid crisis. The lack of procedure-specific guidelines contributes to the vast differences in prescribing practices. OBJECTIVE: To create opioid-prescribing consensus guidelines for common dermatologic procedures. METHODS: We used a 4-step modified Delphi method to conduct a systematic discussion among a panel of dermatologists in the fields of general dermatology, dermatologic surgery, and cosmetics/phlebology to develop opioid prescribing guidelines for some of the most common dermatologic procedural scenarios. Guidelines were developed for opioid-naive patients undergoing routine procedures. Opioid tablets were defined as oxycodone 5-mg oral equivalents. RESULTS: Postoperative pain after most uncomplicated procedures (76%) can be adequately managed with acetaminophen and/or ibuprofen. Group consensus identified no specific dermatologic scenario that routinely requires more than 15 oxycodone 5-mg oral equivalents to manage postoperative pain. Group consensus found that 23% of the procedural scenarios routinely require 1 to 10 opioid tablets, and only 1 routinely requires 1 to 15 opioid tablets. LIMITATIONS: These recommendations are based on expert consensus in lieu of quality evidence-based outcomes research. These recommendations must be individualized to accommodate patients' comorbidities. CONCLUSIONS: Procedure-specific opioid prescribing guidelines may serve as a foundation to produce effective and responsible postoperative pain management strategies after dermatologic interventions.


Assuntos
Analgésicos Opioides/uso terapêutico , Dermatologia , Prescrições de Medicamentos/normas , Dor Pós-Operatória/tratamento farmacológico , Padrões de Prática Médica , Procedimentos Cirúrgicos Dermatológicos , Feminino , Humanos , Masculino , Guias de Prática Clínica como Assunto
14.
J Cutan Pathol ; 45(6): 443-452, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29484694

RESUMO

Biphasic lesions comprised of melanocytic and epithelial components are rare entities believed to arise either as a collision of 2 histologically distinct lesions in the same anatomic location or as a singular progenitor tumor differentiating along 2 differing lineages. Regardless of mechanism of origin, these tumors present unique challenges in pathologic interpretation and in determining appropriate measurements, which assigns subsequent prognosis to the patient. We present 4 tumors of melanoma co-existing with basal cell carcinoma (BCC) and discuss relevant literature regarding these biphasic entities. Patients consisted of 3 males and 1 female, ranging in age from 62 to 93, with lesions located on the shoulder, frontal scalp, forearm and nose. Three of 4 lesions showed melanoma cells limited to BCC tumor lobules, without evidence of direct dermal invasion by melanoma cells, raising the question of whether or not these tumors should be classified as in situ or invasive melanoma. These cases highlight the complexity that such lesions pose to dermatopathologists, in terms of their uncertain origin and variable microscopic appearance. In the absence of data regarding outcomes for these tumors (given their rarity), it is important to utilize a case-by-case approach, with careful clinical correlation and appropriate use of ancillary techniques.


Assuntos
Carcinoma Basocelular/patologia , Melanoma/patologia , Neoplasias Primárias Múltiplas/patologia , Neoplasias Cutâneas/patologia , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade
15.
Dermatol Surg ; 43(11): 1367-1370, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-28930788

RESUMO

BACKGROUND: When an excision is performed by a method other than elliptical excision, direct primary wound closure can result in standing cones or "dog-ears." In 2008, Lee and colleagues noted that dog-ears of <8 mm in height have a statistically greater tendency to resolve without further surgical correction than larger dog-ears. OBJECTIVE: To stratify dog-ears by anatomic location and inform on the need for correction at the time of surgery. MATERIALS AND METHODS: After tumor extirpation, patients were counseled that primary closure of the surgical wound would result in dog-ears at the wound apices. Dog-ears were left uncorrected in participating patients. At 6 months, patients were assessed for resolution of the dog-ears and asked to rate the appearance of the scar. RESULTS: A total of 140 dog-ears were observed in the study period. Anatomical locations included the hand/foot, trunk, limb, and head/neck. Among these dog-ears, 114/140 (81%) showed complete resolution. Patient satisfaction with the scar appearance correlated well with the dog-ear resolution, with most patients rating the appearance of the scar as good to excellent. CONCLUSION: This study suggests that dog-ears on the hand and dog-ears ≤4 mm on the trunk may be observed without any final cosmetic penalty.


Assuntos
Cirurgia de Mohs , Complicações Pós-Operatórias/prevenção & controle , Neoplasias Cutâneas/cirurgia , Técnicas de Fechamento de Ferimentos , Adulto , Cicatriz/prevenção & controle , Feminino , Humanos , Masculino , Satisfação do Paciente , Resultado do Tratamento
16.
JAMA Dermatol ; 153(3): 296-303, 2017 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-28097368

RESUMO

Importance: Skin cancer is the most common malignancy occurring after organ transplantation. Although previous research has reported an increased risk of skin cancer in solid organ transplant recipients (OTRs), no study has estimated the posttransplant population-based incidence in the United States. Objective: To determine the incidence and evaluate the risk factors for posttransplant skin cancer, including squamous cell carcinoma (SCC), melanoma (MM), and Merkel cell carcinoma (MCC) in a cohort of US OTRs receiving a primary organ transplant in 2003 or 2008. Design, Setting, and Participants: This multicenter retrospective cohort study examined 10 649 adult recipients of a primary transplant performed at 26 centers across the United States in the Transplant Skin Cancer Network during 1 of 2 calendar years (either 2003 or 2008) identified through the Organ Procurement and Transplantation Network (OPTN) database. Recipients of all organs except intestine were included, and the follow-up periods were 5 and 10 years. Main Outcomes and Measures: Incident skin cancer was determined through detailed medical record review. Data on predictors were obtained from the OPTN database. The incidence rates for posttransplant skin cancer overall and for SCC, MM, and MCC were calculated per 100 000 person-years. Potential risk factors for posttransplant skin cancer were tested using multivariate Cox regression analysis to yield adjusted hazard ratios (HR). Results: Overall, 10 649 organ transplant recipients (mean [SD] age, 51 [12] years; 3873 women [36%] and 6776 men [64%]) contributed 59 923 years of follow-up. The incidence rates for posttransplant skin cancer was 1437 per 100 000 person-years. Specific subtype rates for SCC, MM, and MCC were 812, 75, and 2 per 100 000 person-years, respectively. Statistically significant risk factors for posttransplant skin cancer included pretransplant skin cancer (HR, 4.69; 95% CI, 3.26-6.73), male sex (HR, 1.56; 95% CI, 1.34-1.81), white race (HR, 9.04; 95% CI, 6.20-13.18), age at transplant 50 years or older (HR, 2.77; 95% CI, 2.20-3.48), and being transplanted in 2008 vs 2003 (HR, 1.53; 95% CI, 1.22-1.94). Conclusions and Relevance: Posttransplant skin cancer is common, with elevated risk imparted by increased age, white race, male sex, and thoracic organ transplantation. A temporal cohort effect was present. Understanding the risk factors and trends in posttransplant skin cancer is fundamental to targeted screening and prevention in this population.


Assuntos
Carcinoma de Célula de Merkel/epidemiologia , Carcinoma de Células Escamosas/epidemiologia , Melanoma/epidemiologia , Transplante de Órgãos/estatística & dados numéricos , Neoplasias Cutâneas/epidemiologia , Adolescente , Adulto , Fatores Etários , Idoso , Carcinoma de Célula de Merkel/etnologia , Carcinoma de Células Escamosas/etnologia , Feminino , Seguimentos , Humanos , Incidência , Masculino , Melanoma/etnologia , Pessoa de Meia-Idade , Estudos Retrospectivos , Fatores de Risco , Fatores Sexuais , Neoplasias Cutâneas/etnologia , Estados Unidos/epidemiologia , População Branca/estatística & dados numéricos , Adulto Jovem
17.
PLoS One ; 8(11): e78419, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24236017

RESUMO

Paleoindian unifacial stone tools frequently exhibit distinct, sharp projections, known as "spurs". During the last two decades, a theoretically and empirically informed interpretation-based on individual artifact analysis, use-wear, tool-production techniques, and studies of resharpening-suggested that spurs were sometimes created intentionally via retouch, and other times created incidentally via resharpening or knapping accidents. However, more recently Weedman strongly criticized the inference that Paleoindian spurs were ever intentionally produced or served a functional purpose, and asserted that ethnographic research "demonstrates that the presence of so called 'graver' spurs does not have a functional significance." While ethnographic data cannot serve as a direct test of the archaeological record, we used Weedman's ethnographic observations to create two quantitative predictions of the Paleoindian archaeological record in order to directly examine the hypothesis that Paleoindian spurs were predominantly accidents occurring incidentally via resharpening and reshaping. The first prediction is that the frequency of spurs should increase as tool reduction proceeds. The second prediction is that the frequency of spurs should increase as tool breakage increases. An examination of 563 unbroken tools and 629 tool fragments from the Clovis archaeological record of the North American Lower Great Lakes region showed that neither prediction was consistent with the notion that spurs were predominately accidents. Instead, our results support the prevailing viewpoint that spurs were sometimes created intentionally via retouch, and other times, created incidentally via resharpening or knapping accidents. Behaviorally, this result is consistent with the notion that unifacial stone tools were multifunctional implements that enhanced the mobile lifestyle of Pleistocene hunter-gatherers.


Assuntos
Indígenas Norte-Americanos , Comportamento de Utilização de Ferramentas , Great Lakes Region , Humanos
18.
Pediatr Dermatol ; 30(6): e246-7, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-22299662

RESUMO

A 7-year-old boy presented with an annular verrucous plaque on the chin of 5 weeks duration. The lesion occurred after a bicycle accident and was unresponsive to antibiotics. Fungal culture grew Sporothrix schenckii. Sporotrichosis should be considered and fungal culture obtained whenever a nodule or plaque fails to respond to initial treatment.


Assuntos
Ciclismo , Queixo/lesões , Sporothrix/isolamento & purificação , Esporotricose/etiologia , Ferimentos e Lesões/microbiologia , Acidentes , Criança , Queixo/microbiologia , Humanos , Masculino , Esporotricose/patologia , Esporotricose/terapia
19.
Science ; 331(6024): 1599-603, 2011 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-21436451

RESUMO

Compelling archaeological evidence of an occupation older than Clovis (~12.8 to 13.1 thousand years ago) in North America is present at only a few sites, and the stone tool assemblages from these sites are small and varied. The Debra L. Friedkin site, Texas, contains an assemblage of 15,528 artifacts that define the Buttermilk Creek Complex, which stratigraphically underlies a Clovis assemblage and dates between ~13.2 and 15.5 thousand years ago. The Buttermilk Creek Complex confirms the emerging view that people occupied the Americas before Clovis and provides a large artifact assemblage to explore Clovis origins.


Assuntos
Antropologia Cultural/história , Arqueologia , Sedimentos Geológicos , História Antiga , Humanos , Texas
20.
J Biol Chem ; 284(8): 4806-14, 2009 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-19088075

RESUMO

Hepatitis C virus NS3 helicase can unwind double-stranded DNA and RNA and has been proposed to form oligomeric structures. Here we examine the DNA unwinding activity of monomeric NS3. Oligomerization was measured by preparing a fluorescently labeled form of NS3, which was titrated with unlabeled NS3, resulting in a hyperbolic increase in fluorescence anisotropy and providing an apparent equilibrium dissociation constant of 236 nm. To evaluate the DNA binding activity of individual subunits within NS3 oligomers, two oligonucleotides were labeled with fluorescent donor or acceptor molecules and then titrated with NS3. Upon the addition of increasing concentrations of NS3, fluorescence energy transfer was observed, which reached a plateau at a 1:1 ratio of NS3 to oligonucleotides, indicating that each subunit within the oligomeric form of NS3 binds to DNA. DNA unwinding was measured under multiple turnover conditions with increasing concentrations of NS3; however, no increase in specific activity was observed, even at enzyme concentrations greater than the apparent dissociation constant for oligomerization. An ATPase-deficient form of NS3, NS3(D290A), was prepared to explore the functional consequences of oligomerization. Under single turnover conditions in the presence of excess concentration of NS3 relative to DNA, NS3(D290A) exhibited a dominant negative effect. However, under multiple turnover conditions in which DNA concentration was in excess to enzyme concentration, NS3(D290A) did not exhibit a dominant negative effect. Taken together, these data support a model in which monomeric forms of NS3 are active. Oligomerization of NS3 occurs, but subunits can function independently or cooperatively, dependent upon the relative concentration of the DNA.


Assuntos
DNA/química , Hepacivirus/enzimologia , Oligonucleotídeos/química , RNA Helicases/química , Proteínas não Estruturais Virais/química , Substituição de Aminoácidos , Hepacivirus/genética , Mutação de Sentido Incorreto , Estrutura Quaternária de Proteína/fisiologia , Estrutura Terciária de Proteína/fisiologia , RNA Helicases/metabolismo , RNA de Cadeia Dupla/química , Especificidade por Substrato/fisiologia , Proteínas não Estruturais Virais/genética
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