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1.
Urology ; 2024 Jun 13.
Artigo em Inglês | MEDLINE | ID: mdl-38878826

RESUMO

OBJECTIVE: To assess textbook outcomes by hospital teaching status following major surgery for urologic cancers. METHODS: We used 100% national Medicare Provider Analysis and Review files from 2017-2020 to assess rates of textbook outcomes in patients undergoing bladder (ie, radical cystectomy), kidney (ie, radical or partial nephrectomy), and prostate (ie, radical prostatectomy) surgery for genitourinary malignancies. The extent of integration of learners into each hospital's workforce-defined as major, minor, and non teaching hospitals-was the primary exposure. A textbook outcome, measured at the patient level, was defined as the absence of in-hospital mortality and mortality within 30days of surgery, no readmission 30days following discharge, no postoperative complication, and no prolonged length of stay. RESULTS: Textbook outcomes were achieved in 51% (8564/16,786) of patients after bladder cancer surgery, 70% (39,938/57,300) of patients after kidney cancer surgery, and 82% (50,408/61,385) of patients after prostate cancer surgery. After adjusting for patient- and hospital-level characteristics, teaching hospitals had higher rates of textbook outcomes in those undergoing bladder (50.7% vs 44.0%; P = .001), kidney (72.0% vs 69.7%; P = .02), and prostate (85.3% vs 81.0%; P <.001) surgery. This effect was attenuated, but not eliminated, by surgical volume in additional sensitivity analyses for bladder (OR: 1.20, 95% CI: 1.00-1.42; P = .04) and prostate (OR: 1.15, 95% CI: 1.00-1.32; P = .04) surgery. There were no significant differences in kidney cancer surgery outcomes after adjusting for hospital volume (OR: 1.03, 95% CI: 0.93-1.14; P = .6). CONCLUSION: Undergoing major cancer surgery at a teaching hospital was associated with an increased likelihood of achieving a textbook outcome. This effect was attenuated by volume but persisted for bladder and prostate surgery.

2.
Urol Oncol ; 42(5): 121-132, 2024 May.
Artigo em Inglês | MEDLINE | ID: mdl-38418269

RESUMO

Radical cystectomy (RC) is the gold standard treatment for patients with organ-confined bladder cancer. However, despite the success of this treatment, many men who undergo orthotopic neobladder substitution develop significant erectile dysfunction and urinary symptoms, including daytime and nighttime urinary incontinence. Prostate-capsule-sparing radical cystectomy (PCS-RC) with orthotopic neobladder (ONB) has been described in the literature as a surgical technique to improve functional outcomes in appropriately selected patients. We performed a systematic review and meta-analysis of manuscripts on PCS-RC with ONB published after 2000. We included retrospective and prospective studies with more than 25 patients and compared PCS-RC with nerve-sparing or conventional RC. Studies in which the entire prostate was spared (including the transitional zone) were excluded. Comparative studies were analyzed to assess rates of daytime continence, nighttime continence, and satisfactory erectile function in patients undergoing PCS-RC compared with those undergoing conventional RC. Fourteen reports were included in the final review. Our data identify high rates of daytime (83%-97%) and nighttime continence (60%-80%) in patients undergoing PCS-RC with ONB. In comparative studies, meta-analysis results demonstrate no difference in daytime continence (RR:1.12; 95% CI: 0.72-1.73) in those undergoing PCS-RC compared to those undergoing conventional RC. Similarly, nighttime continence was similar between the 2 groups (RR:1.85; 95% CI: 0.57-6.00. Erectile function was improved in those undergoing PCS-RC (RR 5.35; 95% CI: 1.82-15.74) in the PCS-RC series. Bladder cancer margin positivity and recurrence rates were similar to those reported in the literature with conventional RC with an average weighted follow-up of 52.2 months. While several studies utilized different prostate cancer (CaP) screening techniques, the rates of CaP were low (incidence 0.02; 95% CI:0.01-0.04), and oncologic outcomes were similar to standard RC. PCS-RC is associated with improved nighttime continence and erectile function compared to conventional RC techniques. Further work is needed to standardize CaP screening before surgery, but the data suggest low rates of CaP with similar oncologic outcomes when compared to RC.


Assuntos
Disfunção Erétil , Neoplasias da Bexiga Urinária , Masculino , Humanos , Cistectomia/métodos , Próstata/cirurgia , Disfunção Erétil/etiologia , Disfunção Erétil/cirurgia , Estudos Prospectivos , Estudos Retrospectivos , Resultado do Tratamento , Neoplasias da Bexiga Urinária/etiologia
3.
Urol Oncol ; 42(3): 67.e17-67.e24, 2024 03.
Artigo em Inglês | MEDLINE | ID: mdl-38212151

RESUMO

BACKGROUND: Prostatic fascia-sparing robotic-assisted radical prostatectomy (PFS-RARP) has improved short-term postoperative continence compared to standard prostatectomy (S-RARP) but long-term differences remain unclear. MATERIALS AND METHODS: One hundred two S-RARP followed by 239 PFS-RARPs were performed by a single surgeon. Univariate analyses were performed with t-test, χ2, Wilcoxon rank sum, Fisher exact, and analysis of variance (ANOVA). Regression models analyzed associates of EPIC-CP scores and oncologic outcomes. Cox proportional hazards modeling assessed postoperative continence. Primary outcomes included patient-reported urinary incontinence (UI) via EPIC-CP and continence rates. Secondary outcomes included EPIC-CP scores, positive surgical margins (PSM), and biochemical recurrence (BCR). Perioperative outcomes and time to continence were measured. RESULTS: Median follow-up for PFS-RARP vs. S-RARP was 26 vs. 65 months. PFS-RARP demonstrated improved EPIC-CP UI and total scores at 24 months. On multivariate analysis, PFS-RARP was associated with improved EPIC-CP UI and total scores through 18 months, but not with PSM or BCR. PFS-RARP had a 39% and 66% reduced risk of incontinence using 0 and 0 to 1 pad-use definitions (HR 0.61, 95% CI 0.39 - 0.95; HR:0.34, 95% CI 0.16 - 0.76). Continence returned faster with PFS-RARP (0 PPD: 91.0 days vs. 261 days, P < 0.001; 0-1 PPD: 32.7 days vs. 171 days, P < 0.001). There were no differences in PSM (35% vs. 25%, P = 0.064). There were more anterior PSM in PFS-RARP vs. S-RARP (47% vs. 26% P = 0.035), but no differences in BCR (16% vs. 22% P = 0.241). CONCLUSIONS: PFS-RARP improves continence and patient-reported QOL up to 24 months postoperatively without compromising oncologic outcomes.


Assuntos
Neoplasias da Próstata , Procedimentos Cirúrgicos Robóticos , Cirurgiões , Incontinência Urinária , Masculino , Humanos , Qualidade de Vida , Resultado do Tratamento , Neoplasias da Próstata/cirurgia , Prostatectomia/efeitos adversos , Incontinência Urinária/etiologia , Fáscia
4.
Can J Urol ; 29(6): 11394-11398, 2022 12.
Artigo em Inglês | MEDLINE | ID: mdl-36495583

RESUMO

Abnormal inferior vena cava (IVC) anatomy may present unique challenges for urologists when performing retroperitoneal surgery. Duplication of the IVC is one such anomalous variation and can be found in up to 3% of the population. Misunderstanding of the implications of this aberrant anatomy may lead to intraoperative or postoperative complications. Here, we present two cases of patients undergoing renal surgeries with duplicate IVC. We then review the embryologic origin and anatomic findings in those with abnormal IVC anatomy as well as discuss the surgical implications and considerations for urologists.


Assuntos
Complicações Pós-Operatórias , Veia Cava Inferior , Humanos , Veia Cava Inferior/cirurgia , Espaço Retroperitoneal
5.
Curr Oncol ; 29(12): 9733-9743, 2022 12 08.
Artigo em Inglês | MEDLINE | ID: mdl-36547178

RESUMO

(Background) Radiation failure for localized prostate cancer is seen in 20-60% of patients who do not undergo extirpative surgery. Though potentially curative, salvage prostatectomy (SS) has not been frequently performed historically due to high rates of complications and postoperative incontinence. With the advent of robotic-assisted radical prostatectomy, these rates appear to be improved. Retzius-sparing approaches have additionally been shown to improve continence outcomes in the index setting, and may further improve continence outcomes in salvage cases while maintaining oncologic integrity. (Methods) We performed a literature review and qualitative analysis of published papers on salvage Retzius-sparing robotic-assisted radical prostatectomy (SRS). Three studies met criteria and were included in analysis. (Results) There were more patients with Gleason Grade Group 1 disease after initial treatment in the SRS group vs. SS (22% vs. 8%). Patients most frequently underwent external beam radiation therapy in both groups (52% vs. 49%). 30-day complication rates were 10% and 26% for SRS and SS, respectively. Continence outcomes were significantly improved in SRS with 59% of continence (based on study criteria) compared to 38% in SS. Time to continence was similarly improved for SRS. Positive surgical margins and biochemical recurrence were not significantly different between SRS and SS in any study. (Conclusions) SRS is a safe and feasible option for salvage treatment of localized prostate cancer and may improve postoperative continence outcomes. Positive surgical margin and biochemical recurrence rates are similar to those reported in SS.


Assuntos
Neoplasias da Próstata , Incontinência Urinária , Masculino , Humanos , Resultado do Tratamento , Próstata/cirurgia , Prostatectomia/efeitos adversos , Prostatectomia/métodos , Neoplasias da Próstata/radioterapia , Neoplasias da Próstata/cirurgia , Neoplasias da Próstata/complicações , Incontinência Urinária/etiologia , Incontinência Urinária/cirurgia
6.
Urol Oncol ; 40(8): 382.e7-382.e13, 2022 08.
Artigo em Inglês | MEDLINE | ID: mdl-35690547

RESUMO

PURPOSE: The impact of anemia in postoperative complications following radical cystectomy (RC) is not completely elucidated and its association with direct hospital costs has not been characterized in depth. Our goal is to determine the association between anemia, 90-day surgical complications and the expenditure attributed to preoperative anemia in patients undergoing RC. MATERIALS AND METHODS: We captured all patients who underwent RC between 2003 and 2017 using the Premier Hospital Database (Premier Inc, Charlotte, NC). Patient, hospital and surgical characteristics were evaluated. Anemia was defined by a corresponding diagnostic code that was present on admission prior to RC. Unadjusted patients' demographic characteristics with and without anemia, hospital and surgeon characteristics were compared, and multivariable regression models were developed to evaluate 90-day complications and total direct hospital costs. RESULTS: The cohort included 83,470 patients that underwent RC between 2003 and 2017 and 11% were found to be anemic. On multivariable analysis, preoperative anemia more than doubled the odds of having a complication (odds ratio 2.19 (1.89-2.53)) and significantly increased the risk of major complications (odds ratio 1.51 (1.31-1.75)) at 90-days after RC. Anemic patients had significantly higher 90-days total direct costs due to higher laboratory, pharmacologic, radiology and operating room costs. CONCLUSIONS: Anemic cystectomy patients face a 50% increase in the risk of major complications within the first 90-days after surgery. This increased risk persisted after adjusting for patient, hospital and surgical factors. Our study suggests hematocrit level prior to RC may be used as a pre-exisitng condition for increased risk of surgical complications.


Assuntos
Anemia , Cistectomia , Complicações Pós-Operatórias , Neoplasias da Bexiga Urinária , Anemia/complicações , Cistectomia/efeitos adversos , Custos Hospitalares , Humanos , Complicações Pós-Operatórias/epidemiologia , Complicações Pós-Operatórias/etiologia , Complicações Pós-Operatórias/cirurgia , Estudos Retrospectivos , Neoplasias da Bexiga Urinária/complicações , Neoplasias da Bexiga Urinária/cirurgia
7.
Can J Urol ; 29(3): 11162-11169, 2022 06.
Artigo em Inglês | MEDLINE | ID: mdl-35691038

RESUMO

INTRODUCTION: To identify prognostic factors for overall survival (OS) in patients with malignant ureteral obstruction (MUO) from gynecologic malignancy (GM), with the goal of improving patient selection for urinary diversion. MATERIALS AND METHODS: Retrospective review of 126 patients with MUO from GM at two academic centers from 2011-2019. Factors related to OS identified by Cox regression proportional hazard model. In patients with incomplete survival data (n = 30), hospice was used as a surrogate for death. Multivariate models and receivers operating characteristics (ROC) curves were created for hemoglobin and albumin values. RESULTS: Overall median survival was 6.2 months. On univariate analysis, age at diagnosis, Charlson Comorbidity Index (CCI) ≥ 8, advanced clinical stage, ascites, pleural effusion, albumin, and hemoglobin were associated with poor OS. OS was higher for those receiving ureteral stenting as compared with no intervention. There was no survival difference based on hydronephrosis grade, stent failure (SF), or creatinine at the time of intervention. On multivariate analysis, albumin < 2.85 g/dL and hemoglobin < 9.6 g/dL were predictive of poor OS. CONCLUSIONS: OS in patients with MUO due to GM is poor. Several prognostic factors for poor survival including low serum albumin and hemoglobin were identified. Ureteral stenting was associated with improved OS compared to observation, but selection bias likely contributed to this result. Additional studies are needed to clarify this finding. These data can be utilized to counsel patients regarding outcomes after urinary diversion in the setting of MUO and perhaps avoid additional procedures in some of these patients who will not derive meaningful benefit.


Assuntos
Hidronefrose , Ureter , Obstrução Ureteral , Albuminas , Feminino , Humanos , Hidronefrose/etiologia , Prognóstico , Estudos Retrospectivos , Stents/efeitos adversos , Obstrução Ureteral/diagnóstico , Obstrução Ureteral/etiologia , Obstrução Ureteral/cirurgia
8.
Can J Urol ; 28(5): 10858-10864, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34657659

RESUMO

INTRODUCTION: Placement of coudé catheters, manual irrigation of urinary catheters, and management of continuous bladder irrigation (CBI) are routine interventions for which nurses often receive little or no formal education. In this study, our aim was to determine factors associated with higher comfort levels for these catheter-care techniques and to assess whether online instructional videos could be used to improve nursing comfort. MATERIALS AND METHODS: Three 5-minute videos were created to demonstrate proper technique for coudé catheter placement, manual irrigation of a catheter, and management of CBI. An online module with pre- and post-video surveys was created and administered to all nursing staff at MedStar Georgetown University Hospital. RESULTS: A total of 821 nurses participated in this study and completed the online module with both pre-- and post-video surveys. Using a 10-point Likert scale, pre-video median comfort levels for coudé catheter placement, manual irrigation of a catheter, and management of CBI were 5, 6, and 5, respectively. Post-video median comfort levels increased significantly to 9, 8, and 8, respectively (p < 0.001). In the linear regression models, prior formal training was significantly associated with higher baseline comfort levels for all three techniques (p < 0.001). CONCLUSIONS: Prior formal training as well as baseline nursing comfort levels for common catheter related techniques tend to be low and the implementation of simple instructional videos via an online platform may be a useful strategy for improving nursing comfort. This study demonstrates a reproducible strategy for disseminating catheter education for nurses on a larger scale.


Assuntos
Cateteres Urinários , Humanos
9.
J Urol ; 205(5): 1335, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33656922
10.
Urol Case Rep ; 36: 101598, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33659187

RESUMO

Lymphoceles are common following prostatectomy with lymph node dissection, but the vast majority are asymptomatic. We present a unique case of a large complex lymphocele tracking into the anterior space of Retzius following Retzius sparing prostatectomy and bilateral pelvic lymphadenectomy. The patient initially presented with shortness of breath and subsequent diagnosis of a submassive pulmonary embolism. Further evaluation revealed compression of the iliac vessels by the fluid collection. Following multiple failed attempts of drainage percutaneously, the patient required return to the operating room for peritoneal marsupialization, drainage of fluid collection, and evacuation of large amounts of clot within the collection.

11.
Can Urol Assoc J ; 15(8): E405-E411, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-33410744

RESUMO

INTRODUCTION: We aimed to characterize patient-related factors that promote followup of repeat onabotulinumtoxinA treatments for overactive bladder via a mixed-methods approach. METHODS: A retrospective chart review was conducted for patients who received intra-detrusor injection of onabotulinumtoxinA at our institution from 2011-2018, who were then surveyed to evaluate their experience, knowledge, and perceptions regarding onabotulinumtoxinA treatment and followup. Patients who received one onabotulinumtoxinA treatment and patients who underwent multiple treatments were compared to assess followup rates following initial treatment, group characteristics, patient comfort, and patient knowledge of needed retreatment. RESULTS: A total of 29.3% of patients received a single treatment and 70.7% of patients received multiple treatments. There was no difference in clinical, demographic, or intake variables between groups. Patients receiving multiple treatments reported having their first procedure in the operating room and reported greater improvement in symptoms and procedure comfort. This group was also more likely to understand that repeat treatments are necessary than those undergoing one treatment. CONCLUSIONS: No research to date has systematically explored patient-reported factors that promote retreatment of onabotulinumtoxinA for overactive bladder. This novel, mixed-methods approach indicates that patient comfort and patient knowledge were the strongest predictors of previous retreatment and anticipated retreatment, suggesting concrete avenues for improved periprocedural patient counselling and education.

12.
Can J Urol ; 27(6): 10496-10499, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-33325356

RESUMO

Acute vasitis, or inflammation of the vas deferens, is a rare condition that classically presents with unilateral groin pain radiating into the scrotum and a bulge or induration along the inguinal canal. As a result, it mimics and is often mistaken for more common pathologies such as inguinal hernia, epididymo-orchitis or testicular torsion. A misdiagnosis may lead to unnecessary surgery and morbidity. Here, we present a case of acute vasitis which was originally diagnosed as an incarcerated inguinal hernia. Finally, we review the imaging findings, which can often be subtle and misinterpreted or missed.


Assuntos
Hérnia Inguinal/diagnóstico por imagem , Inflamação/diagnóstico por imagem , Tomografia Computadorizada por Raios X , Ducto Deferente , Doença Aguda , Adulto , Diagnóstico Diferencial , Humanos , Masculino
13.
Urol Oncol ; 38(11): 849.e19-849.e23, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-32616422

RESUMO

INTRODUCTION: Extended outpatient chemoprophylaxis (ECP) following radical cystectomy (RC) for bladder cancer is proven to reduce rates of venous thromboembolism (VTE). While ECP is commonly performed with enoxaparin, its cost-effectiveness and adherence rate has been called into question. Data from orthopedic literature suggest that ECP with direct oral anticoagulants (DOACs) may be as effective in VTE prevention as enoxaparin in patients undergoing joint surgery. Our goal is to determine how urologic oncologists employ ECP following RC. METHODS: Members of the Society of Urologic Oncology were surveyed on practice patterns for the use of ECP after RC. Specific questions were asked regarding the use of inpatient and outpatient VTE prophylaxis, as well as perceived barriers to DOACs and enoxaparin. RESULTS: There were 121 of 878 (13.8%) respondents and the majority were in academic practices (83%). Most respondents had at least 5 years of experience and performed greater than 10 cystectomies annually. Almost all participants utilized inpatient (97%) and extended (80%) chemoprophylaxis for VTE prevention. Of those who elected for ECP, almost all (96%) used enoxaparin. Only 3 respondents (3%) prescribed oral agents such as rivaroxaban (2) or warfarin (1). Among those using enoxaparin, financial-specific barriers to treatment such as lack of insurance coverage (38%), inability to afford the medication (51%), and need for additional insurance authorization (44%) were reported. Poor patient adherence and refusal to perform injections were reported by 20% and 18% of respondents, respectively. Among the 23 physicians who did not use ECP, cost (39%) and delivery method (26%) were cited as barriers to treatment. CONCLUSIONS: The majority of surveyed urologic oncologists are prescribing subcutaneous enoxaparin ECP following RC. Poor patient adherence due to self-injections and financial barriers were frequently reported and represent a possible opportunity for the use of oral anticoagulants in the post-operative setting. These data will be used in the development of a proposed clinical trial of a DOAC in the post-RC setting.


Assuntos
Anticoagulantes/uso terapêutico , Cistectomia , Enoxaparina/uso terapêutico , Complicações Pós-Operatórias/prevenção & controle , Padrões de Prática Médica , Oncologia Cirúrgica , Neoplasias da Bexiga Urinária/cirurgia , Urologia , Tromboembolia Venosa/prevenção & controle , Assistência ao Convalescente , Quimioprevenção , Cistectomia/métodos , Humanos
15.
Histopathology ; 71(3): 475-479, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28374498

RESUMO

AIMS: GATA3 is a relatively new immunohistochemical marker which shows consistent nuclear expression in a variety of tumours, including breast and urothelial carcinoma. The staining pattern of GATA3 in adrenal lesions is not well established. We aim to describe the expression of GATA3 in adrenal tumours and determine if there is differential staining between pheochromocytoma and adrenal cortical carcinoma. METHODS AND RESULTS: A retrospective search was performed to identify 74 adrenal lesions which were tested immunohistochemically for GATA3 expression. GATA3 was negative in 90% of adrenal cortical carcinoma. In contrast, pheochromocytomas were frequently positive (71%), including benign pheochromocytoma, pheochromocytoma with features concerning for malignancy, malignant (metastatic) pheochromocytoma and composite pheochromocytoma with ganglioneuroma. Metastatic lung adenocarcinoma in the adrenal gland had occasional (36%) expression, while metastatic clear cell renal cell carcinoma in the adrenal gland did not express GATA3. CONCLUSION: As the most common pitfall in diagnosing adrenal cortical carcinoma is mistaking it for pheochromocytoma or vice versa, GATA3 may be useful in narrowing the differential diagnosis as a part of a panel of immunohistochemical markers. However, occasional GATA3 expression in the most common source of metastases within the adrenal gland, metastatic pulmonary adenocarcinoma, may confound the diagnosis due to the overlapping expression with pheochromocytoma and other carcinomas.


Assuntos
Neoplasias das Glândulas Suprarrenais/diagnóstico , Carcinoma Adrenocortical/diagnóstico , Biomarcadores Tumorais/análise , Fator de Transcrição GATA3/biossíntese , Feocromocitoma/diagnóstico , Diagnóstico Diferencial , Fator de Transcrição GATA3/análise , Humanos , Estudos Retrospectivos
16.
Life Sci ; 153: 124-31, 2016 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-27091653

RESUMO

Heart disease represents the leading cause of death among Americans. There is currently no clinical treatment to regenerate viable myocardium following myocardial infarction, and patients may suffer progressive deterioration and decreased myocardial function from the effects of remodeling of the necrotic myocardium. New therapeutic strategies hold promise for patients who suffer from ischemic heart disease by directly addressing the restoration of functional myocardium following death of cardiomyocytes. Therapeutic stem cell transplantation has shown modest benefit in clinical human trials with decreased fibrosis and increased functional myocardium. Moreover, autologous transplantation holds the potential to implement these therapies while avoiding the immunomodulation concerns of heart transplantation. Despite these benefits, stem cell therapy has been characterized by poor survival and low engraftment of injected stem cells. The hypoxic tissue environment of the ischemic/infracting myocardium impedes stem cell survival and engraftment in myocardial tissue. Hypoxic preconditioning has been suggested as a viable strategy to increase hypoxic tolerance of stem cells. A number of in vivo and in vitro studies have demonstrated improved stem cell viability by altering stem cell secretion of protein signals and up-regulation of numerous paracrine signaling pathways that affect inflammatory, survival, and angiogenic signaling pathways. This review will discuss both the mechanisms of hypoxic preconditioning as well as the effects of hypoxic preconditioning in different cell and animal models, examining the pitfalls in current research and the next steps into potentially implementing this methodology in clinical research trials.


Assuntos
Sobrevivência Celular , Miocárdio/citologia , Oxigênio/metabolismo , Células-Tronco/citologia , Animais , Humanos
17.
J Phys Chem A ; 118(6): 993-1003, 2014 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-24446774

RESUMO

Ultrafast pump-probe measurements can discriminate the two forms of melanin found in biological tissue (eumelanin and pheomelanin), which may be useful for diagnosing and grading melanoma. However, recent work has shown that bound iron content changes eumelanin's pump-probe response, making it more similar to that of pheomelanin. Here we record the pump-probe response of these melanins at a wider range of wavelengths than previous work and show that with shorter pump wavelengths the response crosses over from being dominated by ground-state bleaching to being dominated by excited-state absorption. The crossover wavelength is different for each type of melanin. In our analysis, we found that the mechanism by which iron modifies eumelanin's pump-probe response cannot be attributed to Raman resonances or differences in melanin aggregation and is more likely caused by iron acting to broaden the unit spectra of individual chromophores in the heterogeneous melanin aggregate. We analyze the dependence on optical intensity, finding that iron-loaded eumelanin undergoes irreversible changes to the pump-probe response after intense laser exposure. Simultaneously acquired fluorescence data suggest that the previously reported "activation" of eumelanin fluorescence may be caused in part by the dissociation of metal ions or the selective degradation of iron-containing melanin.


Assuntos
Ferro/metabolismo , Luz/efeitos adversos , Melaninas/química , Melaninas/metabolismo , Animais , Oxirredução/efeitos da radiação , Sepia , Espectroscopia de Luz Próxima ao Infravermelho
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