The Keystone Perforator Island Flap: Review of Utility and Versatile Clinical Applications

Background

The keystone perforator island flap (KPIF) was described almost a decade ago. However, this flap has only recently been recognized for its advantages in various clinical applications in plastic surgery. A better understanding of the versatility of KPIFs can help promote the widespread adoption of this technique for complex wounds in various anatomical regions.

Methods

A retrospective chart review was conducted of patients undergoing KPIFs from December 2018 to March 2022 at the authors' home institution. The indications, surgical approaches, patient characteristics, and outcomes were extracted for review and analysis.

Results

A total of 12 patients (ages 13-86 years) underwent reconstruction with KPIFs for oncologic and nononcologic defects. By anatomic region, three cases involved the upper back, six involved the lumbosacral region, one involved the perineum, and two involved the midfoot. Half of the patients (n = 6) had failed previous attempts at wound closure. The mean defect size was 13.8 × 10.0 cm for the upper back lesions, 13.7 × 4.8 for the lumbosacral defects, and 3.5 × 2.0 for the metatarsal wounds. Median follow-up time for all patients was 7.5 months (IQR: 4-10.5). On follow-up, there was 100% flap survival.

Conclusion

KPIFs are a simple, safe, and suitable option for reconstructive closure of defects in many anatomical areas, including wounds complicated by previous failed closure attempts, with low complication risk profile.

Poor accessibility to consumer pricing exists for elective hernia repair surgery

BACKGROUND

Hospital price transparency is federally mandated to improve consumer accessibility. We aimed to evaluate how hospitals were complying with these regulations for elective hernia repairs.

METHODS

Searches were performed for different hospital systems in attempt to find a price for the procedure using author's own health insurance. Data collected included time to reach the cost estimate tool, time to obtain price estimates, and price ranges. With prices for inguinal and ventral hernia repairs varying across the state's medical centers.

RESULTS

Fourteen medical centers across the country were included, all had a cost estimate calculator. The average success rate of obtaining a cost for inguinal hernia was 48%. Comparatively, the average success rate of obtaining a cost for ventral hernia was 12%. Of the successful searches for price, significant variation exists amongst the accessed hernia procedure cost.

CONCLUSION

Despite federal mandates for hospital price transparency, online cost-estimate calculators are underperforming, thus exposing a need for more accessible cost-estimates for patients undergoing elective hernia repair.

External Validation of the Breast Cancer Surgery Risk Calculator (BCSRc): A Predictive Model for Postoperative Complications

BACKGROUND

The breast cancer surgical risk calculator (BCSRc) is a prognostic tool that determines a breast cancer patient's unique risk of acute complications following each possible surgical intervention. When used in the preoperative setting, it can help to stratify patients with an increased complication risk and enhance the patient-physician informed decision-making process. The objective of this study was to externally validate the four models used in the BCSRc on a large cohort of patients who underwent breast cancer surgery.

METHODS

The BCSRc was developed by using a retrospective cohort from the National Surgical Quality Improvement Program database from 2005 to 2018. Four models were built by using logistic regression methods to predict the following composite outcomes: overall, infectious, hematologic, and internal organ complications. This study obtained a new cohort of patients from the National Surgical Quality Improvement Program by utilizing participant user files from 2019 to 2020. The area under the curve, brier score, and Hosmer-Lemeshow goodness of fit test measured model performance, accuracy, and calibration, respectively.

RESULTS

A total of 192,095 patients met inclusion criteria in the development of the BCSRc, and the validation cohort included 60,144 women. The area under the curve during external validation for each model was approximately 0.70. Accuracy, or Brier scores, were all between 0.04 and 0.003. Model calibration using the Hosmer-Lemeshow statistic found all p-values > 0.05. All of these model coefficients will be updated on the web-based BCSRc platform: www.breastcalc.org .

CONCLUSIONS

The BCSRc continues to show excellent external-validation measures. Collectively, this prognostic tool can enhance the decision-making process, help stratify patients with an increased complication risk, and improve expectant management.

The adoption of oncoplastic surgery: Is there a learning curve?

INTRODUCTION

Oncoplastic surgery (OPS) is a form of breast conservation surgery involving partial mastectomy followed by volume displacement or replacement surgery. As the field of OPS is growing, we sought to determine if there was a learning curve to this surgery.

METHODS

A retrospective chart review was conducted of all patients who underwent OPS over a 6-year period with a single surgeon formally trained in both Plastic Surgery and Breast Oncology. Cumulative summation analysis (CUSUM) was performed on mean operative time to generate the learning curve and learning curve phases. Outcomes were compared between phases to determine significance.

RESULTS

Mean operative time decreased significantly across the 6-year period, generating three distinct learning curve phases: Learner phase (cases 1-23), Competence phase (24-73), and Mastery phase (74 and greater). The overall positive margin rate was 10.9% and there was no significant difference in rates between phases (p = 0.49). Overall complication rates, reoperation rates, and locoregional recurrence remained the same across all phases (p = 0.16; p = 0.65; p = 0.41). The rate of partial nipple loss decreased between phases (p = 0.02).

CONCLUSION

As with many complex operations, there does appear to be a learning curve with OPS, as the operative time and the rates of partial nipple loss decreased over time.

Closed Incision Negative Pressure Therapy in Oncoplastic Breast Surgery: A Comparison of Outcomes

We aim to discern the impact of closed incision negative pressure therapy (ciNPT) on wound healing in the oncoplastic breast surgery population.

Methods

A retrospective analysis was conducted on patients who underwent oncoplastic breast surgery with and without ciNPT in a single health system over 6 years. Oncoplastic breast surgery was defined as breast conservation surgery involving partial mastectomy with immediate volume displacement or replacement techniques. Primary outcomes were rates of clinically significant complications requiring either medical or operative intervention, including seroma, hematoma, fat necrosis, wound dehiscence, and infection. Secondary outcomes were rates of minor complications.

Results

ciNPT was used in 75 patients; standard postsurgical dressing was used in 142 patients. Mean age (P = 0.73) and Charlson Comorbidity Index (P = 0.11) were similar between the groups. The ciNPT cohort had higher baseline BMIs (28.23 ± 4.94 versus 30.55 ± 6.53; P = 0.004), ASA levels (2.35 ± 0.59 versus 2.62 ± 0.52; P = 0.002), and preoperative macromastia symptoms (18.3% versus 45.9%; P ≤ 0.001). The ciNPT cohort had statistically significant lower rates of clinically relevant complications (16.9% versus 5.3%; P = 0.016), the number of complications (14.1% versus 5.3% with one complication, 2.8% versus 0% with >2; P = 0.044), and wound dehiscence (5.6% versus 0%; P = 0.036).

Conclusions

The use of ciNPT reduces the overall rate of clinically relevant postoperative complications, including wound dehiscence. The ciNPT cohort had higher rates of macromastia symptoms, BMI, and ASA, all of which put them at increased risk for complications. Therefore, ciNPT should be considered in the oncoplastic population, especially in those patients with increased risk for postoperative complications.

Examining a decade of racial disparity in partial mastectomy and oncoplastic surgery

BACKGROUND AND OBJECTIVES

Understanding racial disparity is crucial to addressing health equity and access to care. Our study aims to examine racial differences in breast conserving surgery (BCS) utilization rates and determine how these rates have changed over time.

METHODS

This retrospective cohort analysis utilized the NSQIP database to identify women diagnosed with breast cancer who underwent BCS procedures between 2008 and 2019. Racial utilization trends were analyzed using a Cochran-Armitage test and Index of Disparity analysis.

RESULTS

In the 12-year period, 202 492 women underwent a breast cancer surgery, of which 47% underwent BCS. Within the BCS subgroup, oncoplastic surgery utilization increased from 3% to 10%, leading to a declining proportion of partial mastectomies: 97% to 90.0% (both p < 0.01). The racial index of disparity for overall BCS patients decreased from 7% to 6%, remained unchanged (1%) for partial mastectomies, and significantly decreased in oncoplastics (23%-7.6%).

CONCLUSION

BCS represents a mainstay option for early-staged breast cancer interventions, this study demonstrate promising progress in decreasing the index of disparity among races and persistent racial inequalities.

Single Versus Dual Surgeon Approaches to Oncoplastic Surgery: A Comparison of Outcomes

INTRODUCTION

Oncoplastic surgery (OPS) is traditionally performed using a dual surgeon (DS) approach that involves both a breast surgeon and a plastic surgeon. It is also performed using a single surgeon (SS) approach with a surgeon trained in both breast surgical oncology and plastic surgery. We sought to determine if outcomes differed between SS versus DS OPS approaches.

METHODS

A retrospective chart review was conducted of all OPS performed in a single health system over a 6-y period by either an SS or a DS approach. Primary outcomes were rates of positive margins and the overall complication rate; secondary outcomes were loco-regional recurrence, disease-free survival, and overall survival.

RESULTS

A total of 217 patients were identified; 117 were SS cases and 100 were DS cases. Baseline preoperative patient characteristics were similar between the two groups as there was no difference in mean Charlson Comorbidity Index scores (P = 0.07). There was no difference in tumor stage (P = 0.09) or nodal status (P = 0.31). Rates of positive margins were not significantly different (10.9% (SS) versus 9% (DS); P = 0.81), nor were rates of complications (11.1% (SS) versus 15% (DS); P = 0.42). Rates of locoregional recurrence were also not significantly different (1.7% (SS) versus 0% (DS); P = 0.5). Disease-free survival and overall survival were not significantly different at 1-y, 3-y, and 5-y time points (P = 0.20 and P = 0.23, respectively) although follow-up time was not sufficient for definitive analysis regarding survival.

CONCLUSIONS

Both SS and DS approaches to OPS have similar outcomes with regards to positive margin rates and surgical complication rates and are comparably safe.

Comparing oncoplastic breast reduction with immediate symmetry surgery to standard breast reduction surgery: Are postoperative complications worse?

INTRODUCTION

Oncoplastic breast reduction mammoplasty (ORM) is an excellent treatment option for women with breast cancer and macromastia undergoing breast conservation therapy. Here, we aim to better understand the risks associated with ORM compared to standard reduction mammoplasty (SRM).

METHODS

A retrospective chart review was performed of patients undergoing ORM or SRM from 2015 to 2021. Primary outcomes included the occurrence of major or minor postoperative complications in the two groups and delays to adjuvant therapy (>90 days) among the women undergoing ORM.

RESULTS

Women in the ORM group (n = 198) were significantly older (p < 0.001) with a higher prevalence of smoking (p < 0.001), diabetes mellitus (p < 0.01), and a Charlson comorbidity index ≥ 3 (p < 0.001) compared to women undergoing SRM (n = 177). After controlling for potential confounders, there were no significant between-group differences in the odds of developing postoperative complications (odds ratio = 0.80, 95% confidence interval: 0.36-1.69). Only 3% (n = 4) of the 150 women undergoing adjuvant radiation or chemotherapy experienced delays related to postoperative complications.

CONCLUSION

ORM has a similar safety profile as SRM, despite the older age and higher number of comorbidities often seen in patients undergoing ORM, and is a safe option for achieving contralateral symmetry at the time of partial mastectomy without delays to adjuvant therapy.

Rare Presentation of Breast Implant Infection and Breast Implant Illness Caused by Penicillium Species

What is breast implant illness? What is the proposed pathophysiology behind breast implant illness? What are the most common etiologies of fungal breast implant infections? What risks should patients undergoing breast augmentation be informed of?

A Cost-Utility Analysis of the Use of Closed-Incision Negative Pressure System in Vascular Surgery Groin Incisions

OBJECTIVE

Closed-incision negative pressure therapy (CINPT) with the Prevena system has been used and clinically evaluated in high-risk groin incisions to reduce the risk of postoperative complications. We performed a cost-effectiveness analysis evaluating CINPT in femoral-popliteal bypass with prosthetic graft.

METHODS

A literature review looking at prospective randomized trials determined the probabilities and outcomes for femoral-popliteal bypass with and without CINPT. Reported utility scores were used to estimate the quality adjusted life years (QALYs) associated with a successful procedure and postoperative complications. Medicare current procedure terminology and diagnosis-related group codes were used to assess the costs for a successful surgery and associated complications. A decision analysis tree was constructed with rollback analysis to highlight the more cost-effective strategy. An incremental cost-effectiveness ratio (ICER) analysis was performed with a willingness to pay at $50,000. Deterministic and probabilistic sensitivity analyses were performed to validate the robustness of the results, and to accommodate for the uncertainty in the literature.

RESULTS

Femoral-popliteal bypass with CINPT is less costly ($40,138 vs $41,774) and more effective (6.14 vs 6.13) compared to without CINPT. This resulted in a negative ICER of -234,764.03, which favored CINPT, indicating a dominant strategy. In one-way sensitivity analysis, surgery without CINPT was more cost-effective if the probability of successful surgery falls below 84.9% or if the cost of CINPT exceeds $3139. Monte Carlo analysis showed a confidence of 99.07% that CINPT is more cost-effective.

CONCLUSIONS

Despite the added device cost of CINPT, it is cost-effective in vascular surgical operations using groin incisions.

Sleep Quality Among Burn Survivors And The Importance Of Intervention: A Systematic Review And Meta-Analysis

Burn survivors undergo a plethora of physiologic disturbances which can greatly affect quality of life (QOL) and healing processes. This review aimed to systematically examine sleep quality among individuals with burns and to explore the effectiveness of interventions using a meta-analytic approach. A systematic review of the literature was conducted by searching for articles using various databases. Titles and abstracts were screened and full texts of retained articles were assessed based on eligibility criteria. Methodological quality was ascertained in all articles using various scales. Overall, 5,323 articles were screened according to titles and abstracts and 25 articles were retained following full-text screening. Of the twenty-five articles, 17 were assessed qualitatively while 8 were included in the meta-analysis. Based on the qualitative analysis, sleep was found to be negatively affected in burn patients. The subsample of 8 articles included in the meta-analysis showed an overall weighted mean effect size (Hedges's g) of 1.04 (SE = 0.4, 95% CI, z = 3.0; p < 0.01), indicating a large, positive effect of intervention on sleep quality for burn patients. This review was able to demonstrate the detrimental effects of burn injury on sleep quality. Several interventions have been examined throughout the literature and have shown to be beneficial for sleep quality. However, there is great heterogeneity between existing interventions. The results from this review suggest that further research is needed before recommendations can be made as to which intervention is most effective at improving sleep in patients suffering from burn injuries.

Breast Implant Illness: Treatment Using Total Capsulectomy and Implant Removal

BACKGROUND

Breast implant illness (BII) is extramammary systemic symptoms that are caused by breast implants. The emergence of this controversial topic has spurred patients with breast implants who are experiencing these symptoms to seek implant removal, hoping to feel better. This article presents novel outcomes and suggestions for plastic surgeons in managing BII using total capsulectomy and breast implant removal.

METHODS

In this retrospective cohort study conducted between 2016 and 2020, medical records of all patients undergoing breast implant removal were reviewed. Inclusion criteria consisted of all patients with history of breast implant placement presenting with mastodynia and capsular contracture on physical examination. Patients with history of implant-based reconstruction following mastectomy and patients who underwent implant exchange were excluded. All patients underwent bilateral implant removal and total capsulectomies.

RESULTS

A total of 200 patients who fulfilled the inclusion criteria were identified. Average age was 45.5 (range: 29-73) years and average body mass index was 26.28 (range: 19-36.8), with an average follow-up time of 5 months postoperatively. Of patients with a presentation of BII, 96% reported improved or complete resolution of their systemic symptoms after implant removal and total capsulectomy. A positive microbial culture was found in 68.5% of patients, and all culture-positive patients reported improvement post-treatment. The most common organisms found were Propionibacterium acnes (49.6%). There were no associations between implant characteristics and rate of positive microbiology findings.

CONCLUSIONS

Our study shows that implant removal with capsulectomy drastically improves BII symptoms. Further large prospective cohort studies are needed to better understand this entity.

Surgical Lymphedema Treatment: A Meta-Analysis and Recommendations

Background

Lymphedema is a common complication of lymph node surgery; however, evidence on diagnosing, monitoring, and treating the condition is sparse. This meta-analysis evaluates the outcomes of common surgical treatments of lymphedema and provides suggestions for future research directions.

Methods

A review of PubMed and Embase was performed according to Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines. All English-language studies published through June 1, 2020, were included. We excluded nonsurgical interventions, literature reviews, letters, commentaries, nonhuman or cadaver studies, and studies with inadequate sample size (N < 20).

Results

A total of 583 cases from 15 studies in patients with lymphedema met our inclusion criteria for our 1-arm meta-analysis: 387 upper extremity treatments and 196 lower extremity treatments. The volume reduction rates of lymphedema for upper extremity and lower extremity treatments were 38.0% [95% confidence interval (CI), 25.9%-50.2%] and 49.5% (95% CI, 32.6%-66.3%), respectively. The most common postoperative complications were cellulitis, reported in 4.5% of patients (95% CI, 0.9%-10.6%), and seromas, reported in 4.6% (95% CI, 0%-17.8%) of patients. Average quality of life measures across all studies improved by 52.2% (95% CI, 25.1%-79.2%) for patients who underwent upper extremity treatment.

Conclusions

Surgical management of lymphedema shows great promise. Our data suggest that adopting a standardized system of limb measurement and disease staging can increase effectiveness of treatment outcomes.

Immediate Lymphatic Reconstruction for Prevention of Secondary Lymphedema: A Meta-Analysis

BACKGROUND

Secondary lymphedema remains one of the most notorious complications of axillary and pelvic lymph node surgery following mastectomy. There is a lack of high-level evidence found on the effectiveness of immediate lymphatic reconstruction (ILR) in preventing secondary lymphedema. This meta-analysis evaluates the outcomes of ILR for prevention of secondary lymphedema in patients undergoing different surgeries, and provides suggestions for lymphatic microsurgical preventive healing approach (LYMPHA).

METHODS

A review of PubMed, Embase, and Web of Science was performed according to Preferred Reporting Items for Systematic Review and Meta-Analyses guidelines. All English-language studies published from January 1, 2009 to June 1, 2020 were included. We excluded non-ILR interventions, literature reviews/letters/commentaries, and nonhuman or cadaver studies. A total of 789 patients that were enrolled in 13 studies were included in our one-arm meta-analysis.

RESULTS

A total of 13 studies (n=789) met inclusion criteria: upper extremity ILR (n=665) and lower extremity ILR (n=124). The overall incidence of lymphedema for upper extremity ILR was 2.7% (95%CI: 1.1%-4.4%) and lower extremity ILR was 3.6% (95%CI: 0.3%-10.1%). For upper extremity ILR, the average follow-up time was 11.6 ± 7.8 months and the LE incidence appeared to be the highest approximately 1 to 2 years postoperation.

CONCLUSIONS

Lymphedema is a common complication in cancer treatment. ILR, especially LYMPHA, may be an effective technique to facilitate lymphatic drainage at the time of the index procedure but future studies will be required to show its short-term efficacy and long-term outcomes.

Assessment of Financial Conflicts of Interest Related to the Use of Dermal Substitutes in Burn Management

This study aims to systematically review the accuracy of the self-reporting of conflicts of interest (COI) among studies related to the use of dermal substitute products in burn management and evaluate factors associated with increased discrepancies. To do so, a literature search was done to identify studies investigating the use of dermal substitutes in burn management published between 2015 - 2019. Industry payments were collected using the Centers for Medicare & Medicaid Services Open Payments database. Declared COI were then compared with the listed payments. Studies and authors were considered to have a COI if they received payments totaling >$100 for each company. A total of 51 studies (322 authors) were included for analysis. Thirty-eight studies (75%) had at least one author received an undisclosed payment from industry. From 2015 to 2019, 1391 general payments (totaling $1,696,848) and 108 research payments (totaling $1,849,537) were made by 82 companies. When increasing the threshold on what would be considered an undisclosed payment, the proportion of authors with discrepancies gradually decreased, from 88% of authors with undisclosed payments >$100 to 27% of authors with undisclosed payments >$10,000. Author order, journal impact factor, and study type were not significantly associated with increased risk of discrepancy. We found that the majority of studies investigating the use of dermal substitute products for burn management did not accurately declare COI, highlighting the need for a uniform declaration process and greater transparency of industry sponsorship by authors when publishing peer-reviewed burn surgery research papers.

Abstract SS1-03: Examining a decade of racial disparity in partial mastectomy and oncoplastic surgery

BACKGROUND: Breast Conservation Surgery (BCS) includes either partial mastectomy or oncoplastic surgery, of which oncoplastic surgery has become increasingly prevalent. Previous studies have examined BCS rates and post-operative complications, however, no known study has analyzed racial disparity in BCS utilization rates. Understanding racial disparity is crucial to addressing health equality and access to care. Therefore, our study aims to examine racial differences in BCS utilization rates within an 11-year period to determine how these rates have changed over time. METHODS: This retrospective cohort analysis utilized the NSQIP (National Surgical Quality Improvement Program) database to identify women who underwent BCS procedures between 2008-2018. All patients were diagnosed with ductal carcinoma in situ or invasive breast cancer. BCS was further sub-divided into partial mastectomy and oncoplastic surgery. Patient demographics were recorded, and racial utilization trends were analyzed using a Cochran- Armitage test and Index of Disparity analysis, which is a method for summarizing proportional changes within a group’s population and its subgroups. RESULTS: In the 11-year period, 180,700 women underwent a breast cancer resection, of which 46% underwent BCS. Within BCS, 92% underwent a partial mastectomy and 8% received oncoplastic procedures. For both BCS subgroups, Caucasian women held the highest sample size (82%), followed by African Americans (12%), and Asian Americans (5%). Within the total sample size, BCS utilization increased from 38% in 2008 to 53% in 2018. Within the BCS subgroup, the proportion of patients having oncoplastics increased from 3.5% in 2008 to 10% in 2018, leading to a declining proportion of partial mastectomies: 96.5% to 90.0% (all p&lt;0.01). When stratified by race, oncoplastic utilization between 2008 and 2018 increased from 4% to 10% in Asian and Caucasian patients, and 1% to 10% in African American patients (p&lt;0.01). Overall, the racial index of disparity for BCS patients decreased from 17.1% to 9.7%. Interestingly, the index of disparity has remained relatively unchanged for partial mastectomies (1.2% to 0.2%), but significantly decreased in oncoplastics (35% to 1.6%) suggesting an improvement in racial disparities for this surgical option. CONCLUSION: As breast conservation surgery becomes the mainstay for early-staged breast cancer interventions, it is crucial to understand the potential for novel procedures to worsen healthcare inequalities. This study demonstrates promising progress within the field of breast conservation surgery with a decreasing index of disparity among races especially in oncoplastic surgery.

Citation Format: Jolie Jean, Michael M. Jonczyk, Christopher Homsy, Stephen Naber, Abhishek Chatterjee. Examining a decade of racial disparity in partial mastectomy and oncoplastic surgery [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr SS1-03.

A cost-utility analysis comparing large volume displacement oncoplastic surgery to mastectomy with single stage implant reconstruction in the treatment of breast cancer

BACKGROUND

For larger cancers in moderate to large breast sized women, breast surgical cancer treatment may include large volume displacement oncoplastic surgery (LVOS) or mastectomy with single stage implant reconstruction (SSIR). Often in the case of LVOS, reduction mammaplasty designs are used in the oncoplastic reconstructions with a contralateral symmetry operation. The goal of this study was to investigate the cost-utility between LVOS versus SSIR to determine which approach is cost-effective in the treatment of breast cancer.

METHODS

A review of the literature was performed to determine baseline values and ranges. An average national Medicare payment rates using DRG and CPT codes were used for cost assessment. After constructing a decision tree, an incremental cost-utility ratio (ICUR) was calculated comparing the difference for both surgical options in costs by the difference in clinical-effectiveness. To validate our results, we performed one-way sensitivity analyses in addition to a Monte-Carlo analysis.

RESULTS

An ICUR of $546.81/QALY favoring LVOS was calculated based off of its clinical-effectiveness gain of 7.67 QALY at an additional cost of $4194. One-way sensitivity analyses underscored the degree by which LVOS was cost-effective. For example, LVOS became cost-ineffective when a successful LVOS cost more than $50,000. Similarly, probabilistic sensitivity analysis using Monte-Carlo simulation showed that even with varying multiple variables at once, results tended to favor our conclusion supporting the cost-effectiveness of LVOS.

CONCLUSIONS

For the appropriate patients with moderate to large sized breasts with breast cancer, large volume displacement oncoplastic surgery is cost-effective compared to mastectomy with single staged implant reconstruction.

A CpG-rich RNA and an RNA helicase tightly associated with the DNA demethylation complex are present mainly in dividing chick embryo cells

In the developing chicken embryo, active DNA demethylation requires both RNA and proteins (Nucleic Acids Res. 25, 2375-2380, 1997; ibid. 25, 4545-4550, 1997, FEBS Lett. 449, 251-254, 1999a). In vitro assays indicate that in the 5- and 12-day-old embryos the highest specific activity of 5-methylcytosine DNA glycosylase is found in the brain, the eyes and the skin. In situ hybridization with antisense CpG-rich RNA tightly associated to the DNA demethylation complex shows a restricted expression pattern only in proliferating tissues such as the neuroepithelia of the brain in 5-day-old embryos. The RNA is absent in differentiated tissues like the skeletal and heart muscle, liver and the crystallin-producing cells in the lens. The CpG-rich RNA is transcribed in a developmental stage-specific rather than in a cell-specific manner. In contrast transcripts of DNA methyltransferase are found in dividing and quiescent cells. In situ hybridization with a probe of a RNA helicase which is also associated with the DNA demethylation complex shows a very similar localization in mitotically active tissues as the CpG-rich RNA. The content of 5-methylcytosine in individual cells was determined with a specific monoclonal antibody and cytometric analysis on tissue sections. The results indicate that proliferating cells have on the average 15% more methylated cytosines than non-dividing cells. This represents roughly 3x10(6) more methylation sites per haploid genome.

Experimental development of a fixed volume, gravity draining, prosthetic urinary bladder

A fixed volume, semi-rigid, gravity draining prosthetic urinary bladder has been developed in experimental animals. The conceptual model demands: 1) an encrustation resistant lumenal surface; 2) successful urothelial-prosthesis and bowel-prosthesis anastomoses; 3) a transcutaneous abdominal wall prosthesis that bonds with skin, muscle, bladder, and peritoneum which resists external and intraluminal bacterial challenge; and 4) an air permeable, fluid impermeable filter which allows passive filling and gravity evacuation of urine. The principles involved have been successfully tested in rodents, rabbits, swine, and dogs. To date two total alloplastic prosthetic bladders fabricated from Biolor II and Proplast have been inserted in mini-swine for 4 weeks.