Long-term follow-up of temporary abdominal closure in complex abdomens during liver transplant

BACKGROUND

Temporary abdominal closure is commonly employed in liver transplantation when patient factors make primary fascial closure challenging. However, there is minimal data evaluating long-term survival and patient outcomes after temporary abdominal closure.

METHODS

A single-center, retrospective review of patients undergoing liver transplantation from January 2013 through December 2017 was performed with a 5-year follow-up. Patients were characterized as either requiring temporary abdominal closure or immediate primary fascial closure at the time of liver transplantation.

RESULTS

Of 422 patients who underwent 436 liver transplantations, 17.2% (n = 75) required temporary abdominal closure, whereas 82.8% (n = 361) underwent primary fascial closure. Patients requiring temporary abdominal closure had higher Model for End-Stage Liver Disease scores preoperatively (27 [22-36] vs 23 [20-28], P = .0002), had higher rates of dialysis preoperatively (28.0% vs 12.5%, P = .0007), and were more likely to be hospitalized within 90 days of liver transplantation (64.0% vs 47.5%, P = .0093). On univariable analysis, survival at 1 year was different between the groups (90.9% surviving at 1 year for primary fascial closure versus 82.7% for temporary abdominal closure, P = .0356); however, there was no significant difference in survival at 5 years (83.7% vs 76.0%, P = .11). On multivariable analysis, there was no difference in survival after adjusting for multiple factors. Patients requiring temporary abdominal closure were more likely to have longer hospital stays (median 16 days [9.75-29.5] vs 8 days [6-14], P < .0001), more likely to be readmitted within 30 days (45.3% vs 32.2%, P = .03), and less likely to be discharged home (36.5% vs 74.2%, P < .0001).

CONCLUSIONS

Temporary abdominal closure after liver transplantation appears safe and has similar outcomes to primary fascial closure, though it is used more commonly in complex patients.

Predicting early discharge and readmission following pancreaticoduodenectomy [S079]

INTRODUCTION

Implementing enhanced recovery after surgery (ERAS) protocols for major abdominal surgery has been shown to decrease length of stay (LOS) and postoperative complications, including mortality and readmission. Little is known to guide which patients undergoing pancreaticoduodenectomy (PD) should be eligible for ERAS protocols.

METHODS AND PROCEDURES

A retrospective chart review of all PD performed from 2010 to 2018 within an integrated healthcare system was conducted. A predictive score that ranges from 0 to 4 was developed, with one point assigned to each of the following: obesity (BMI > 30), operating time > 400 min, estimated blood loss (EBL) > 400 mL, low- or high-risk pancreatic remnant (based on the presence of soft gland or small duct). Chi-squared tests and ANOVA were used to assess the relationship between this score and LOS, discharge before postoperative day 7, readmission, mortality, delayed gastric emptying (DGE), and pancreatic leak/fistula.

RESULTS

291 patients were identified. Mean length of stay was 8.5 days in those patients who scored 0 compared to 16.2 days for those who scored 4 (p = 0.001). 30% of patients who scored 0 were discharged before postoperative day 7 compared to 0% of those who scored 4 (p = 0.019). Readmission rates for patients who scored 0 and 4 were 12% and 33%, respectively (p = 0.017). Similarly, postoperative pancreatic fistula occurred in 2% versus 25% in these groups (p = 0.007).

CONCLUSION

A simple scoring system using BMI, operating time, EBL, and pancreatic remnant quality can help risk-stratify postoperative PD patients. Those with lower scores could potentially be managed via an ERAS protocol. Patients with higher scores required longer hospitalizations, and adjunctive therapy such as medication and surgical technique to decrease risk of delayed gastric emptying and pancreatic fistula could be considered.

Pancreatic Neuroendocrine Tumor: Rationale for Centralization in an Integrated Health Care System

OBJECTIVES

Given the complex surgical management and infrequency of pancreatic neuroendocrine tumor, we hypothesized that treatment at a center of excellence improves survival.

METHODS

Retrospective review identified 354 patients with pancreatic neuroendocrine tumor treated between 2010 and 2018. Four hepatopancreatobiliary centers of excellence were created from 21 hospitals throughout Northern California. Univariate and multivariate analyses were performed. The χ2 test of clinicopathologic factors determined which were predictive for overall survival (OS).

RESULTS

Localized disease was seen in 51% of patients, and metastatic disease was seen in 32% of patients with mean OS of 93 and 37 months, respectively (P < 0.001). On multivariate survival analysis, stage, tumor location, and surgical resection were significant for OS (P < 0.001). All stage OS for patients treated at designated centers was 80 and 60 months for noncenters (P < 0.001). Surgery was more common across stages at the centers of excellence versus noncenters at 70% and 40%, respectively (P < 0.001).

CONCLUSIONS

Pancreatic neuroendocrine tumors are indolent but have malignant potential at any size with management often requiring complex surgeries. We showed survival was improved for patients treated at a center of excellence, where surgery was more frequently utilized.

Centralization of pancreatic cancer treatment within an integrated healthcare system improves overall survival

BACKGROUND

Higher-volume centers for pancreatic cancer surgeries have been shown to have improved outcomes such as length of stay. We examined how centralization of pancreatic cancer care within a regional integrated healthcare system improves overall survival.

METHODS

We conducted a retrospective study of 1621 patients treated for pancreatic cancer from February 2010 to December 2018. Care was consolidated into 4 Centers of Excellence (COE) in surgery, medical oncology, and other specialties. Descriptive statistics, bivariate analysis, Chi-square tests, and Kaplan-Meier analysis were performed.

RESULTS

Neoadjuvant chemotherapy use rose from 10% to 31% (p < .001). The median overall survival (OS) improved by 3 months after centralization (p < .001), but this did not reach significance on multivariate analysis.

CONCLUSIONS

Our results suggest that in a large integrated healthcare system, centralization improves overall survival and neoadjuvant therapy utilization for pancreatic cancer patients.

Abstract P2-11-09: Excellent acute toxicity outcomes with proton therapy for partial breast irradiation in early stage breast cancer: Initial results of a multi-institutional phase II trial

Background and Purpose: Partial breast irradiation (PBI) with proton therapy after lumpectomy for early stage invasive breast cancer is an area of active investigation. Advantages of this technique include a shorter treatment course and the potential for decreased morbidity versus external beam photon radiation therapy given superior sparing of the surrounding normal breast tissue. To date, multiple single-institutional studies have reported conflicting results on the acute toxicity of PBI. This prospective phase II trial investigates the feasibility, safety, and efficacy of delivering PBI with proton therapy in a multi-institutional setting.

Methods: Patients over the age of 50 years with ER-positive nonlobular invasive breast cancer or ductal carcinoma in situ ≤3 cm in size who had undergone lumpectomy with at least 2 mm negative surgical margins were treated with proton therapy to a dose of 40 Gy delivered over 10 daily fractions. In this initial analysis, we assess early toxicity and treatment efficacy of proton PBI. Patients were followed up at 4 weeks post-treatment and annually thereafter, along with annual mammograms. Patient-reported quality of life and physician-reported cosmesis assessments including photographs were obtained at 1 and 3 years post-treatment.

Results: Forty patients were enrolled, of which 38 were evaluable. At a median follow-up of 17.8 months (range 2-36 months), all patients had overall breast cosmesis that was scored “good” or “excellent”. Of 6 grade 2 acute adverse events that occurred, only 1 was radiation dermatitis, with others including lymphedema, hot flashes, and fatigue. One grade 3 acute toxicity occurred 3 weeks after radiation completion in the form of vascular disease requiring stent placement, highly unlikely to be attributable to radiation effects. Patient-reported quality of life outcomes were recorded using the standardized Breast Cancer Treatment Outcome Scale (BCTOS) scored from 1-4 (1: none; 2: mild; 3: moderate; 4: large), with endpoints receiving a score of 3 or 4 most frequently involving change in breast size, breast texture, nipple appearance, or scar tissue. Patients assigned a score of 4 for change in nipple appearance (n=2), breast shape (n=2), and scar tissue formation (n=2). To date, local, locoregional, and distant disease control are 100%, although one patient has developed a new hormone receptor-negative invasive ductal carcinoma of the contralateral breast.

Conclusion: Proton PBI provides excellent early cancer control with acceptable cosmetic outcomes and minimal adverse effects as per patient- and physician-reported assessments. On continued follow-up, late toxicity and cosmesis, as well as long-term disease control outcomes, will be assessed.

Citation Format: Choi JI, Chang AL. Excellent acute toxicity outcomes with proton therapy for partial breast irradiation in early stage breast cancer: Initial results of a multi-institutional phase II trial [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-11-09.

Surgeon Characteristics Supersede Hospital Characteristics in Mortality After Urgent Colectomy

BACKGROUND

Urgent colectomy is a common procedure with a high mortality rate that is performed by a variety of surgeons and hospitals. We investigated patient, surgeon, and hospital characteristics that predicted mortality after urgent colectomy.

METHODS

The University HealthSystem Consortium was queried for adults undergoing urgent or emergent colectomy between 2009 and 2013 (n = 50,707). Hospitals were grouped into quartiles according to risk-adjusted observed-to-expected (O/E) mortality ratios and compared using the 2013 American Hospital Association Annual Survey. Multiple logistic regression was used to determine patient and provider characteristics associated with in-hospital mortality.

RESULTS

The overall mortality rate after urgent colectomy was 9 %. Mortality rates were higher for patients with extreme severity of illness (27.6 %), lowest socioeconomic status (10.6 %), weekend admissions (10.7 %), and open (10.5 %) and total (15.8 %) colectomies. Hospitals with the lowest O/E ratios were smaller and had lower volume and less teaching intensity, but there were no significant trends with regard to financial (expenses, payroll, capital expenditures per bed) or personnel characteristics (physicians, nurses, technicians per bed). On multivariate analysis, mortality was associated with patient age (10 years: OR 1.31, p < 0.01), severity of illness (extreme: OR 34.68, p < 0.01), insurance status (Medicaid: OR 1.24, p < 0.01; uninsured: OR 1.40, p < 0.01), and weekend admission (OR 1.09, p = 0.04). Surgeon volume was associated with reduced mortality (per 10 cases: OR 0.99, p < 0.01), but hospital volume was not (per case: OR 1.00, p = 0.84).

CONCLUSIONS

Mortality is common after urgent colectomy and is associated with patient characteristics. Surgeon volume and practice patterns predicted differences in mortality, whereas hospital factors did not. These data suggest that policies focusing solely on hospital volume ignore other more important predictors of patient outcomes.

pH modulation ameliorates the red blood cell storage lesion in a murine model of transfusion

BACKGROUND

Prolonged storage of packed red blood cells (pRBCs) induces a series of harmful biochemical and metabolic changes known as the RBC storage lesion. RBCs are currently stored in an acidic storage solution, but the effect of pH on the RBC storage lesion is unknown. We investigated the effect of modulation of storage pH on the RBC storage lesion and on erythrocyte survival after transfusion.

METHODS

Murine pRBCs were stored in Additive Solution-3 (AS3) under standard conditions (pH, 5.8), acidic AS3 (pH, 4.5), or alkalinized AS3 (pH, 8.5). pRBC units were analyzed at the end of the storage period. Several components of the storage lesion were measured, including cell-free hemoglobin, microparticle production, phosphatidylserine externalization, lactate accumulation, and byproducts of lipid peroxidation. Carboxyfluorescein-labeled erythrocytes were transfused into healthy mice to determine cell survival.

RESULTS

Compared with pRBCs stored in standard AS3, those stored in alkaline solution exhibited decreased hemolysis, phosphatidylserine externalization, microparticle production, and lipid peroxidation. Lactate levels were greater after storage in alkaline conditions, suggesting that these pRBCs remained more metabolically viable. Storage in acidic AS3 accelerated erythrocyte deterioration. Compared with standard AS3 storage, circulating half-life of cells was increased by alkaline storage but decreased in acidic conditions.

CONCLUSIONS

Storage pH significantly affects the quality of stored RBCs and cell survival after transfusion. Current erythrocyte storage solutions may benefit from refinements in pH levels.

Variability in postoperative resource utilization after pancreaticoduodenectomy: Who is responsible

BACKGROUND

We aimed to quantify and predict variability that exists in resource utilization after pancreaticoduodenectomy and determine how such variability impacts postoperative outcomes.

METHODS

The University HealthSystems Consortium database was queried for all pancreaticoduodenectomies performed between 2011-2013 (n = 9,737). A composite resource utilization score was created using z-scores of 8 clinically significant postoperative care delivery variables including number of laboratory tests, imaging tests, computed tomographic scans, days on antibiotics, anticoagulation, antiemetics, promotility agents, and total number of blood products transfused per patient. Logistic, Poisson, and gamma regression models were used to determine predictors of increased variability in care between patients.

RESULTS

Having a high (versus low) resource utilization score after pancreaticoduodenectomy correlated with increased duration of stay; (odds ratio 2.28), cost (odds ratio 1.89), readmission rate (odds ratio 1.46), and mortality (odds ratio 7.54). Patient-specific factors were the strongest predictors and included extreme severity of illness (odds ratio 114), major comorbidities/complications (odds ratio 5.99), and admission prior to procedure (odds ratio 2.72; all P < .01). Surgeon and center volume were not associated with resource utilization.

CONCLUSION

Public reporting of patient outcomes and resource utilization, invariably tied to reimbursement in the near future, should consider that much of the postoperative variability after complex pancreatic operation is related to patient-specific risk factors.

The impact of morbid obesity on resource utilization after renal transplantation

BACKGROUND

A growing number of renal transplant recipients have a body mass index ≥40. While previous studies have shown that patient and graft survival are significantly decreased in renal transplant recipients with body mass indexes ≥40, less is known about perioperative outcomes and resource utilization in morbidly obese patients. We aimed to analyze the effects of morbid obesity on these parameters in renal transplant.

METHODS

Using a linkage between the Scientific Registry of Transplant Recipients and the databases of the University HealthSystem Consortium, we identified 29,728 adult renal transplant recipients and divided them into 2 cohorts based on body mass index (<40 vs ≥40 kg/m²). The body mass index ≥40 group comprised 2.5% (n = 747) of renal transplant recipients studied.

RESULTS

Body mass index ≥40 recipients incurred greater direct costs ($84,075 vs $79,580, P < .01), index admission costs ($91,169 vs $86,141, P < .01), readmission costs ($5,306 vs $4,596, P = .01), and combined costs ($99,590 vs $93,939, P < .001). Thirty-day readmission rates were also greater among body mass index ≥40 recipients (33.92% vs 26.9%, P < .01). Morbid obesity was not predictive of stay (odds ratio 1.01, P = .75).

CONCLUSION

Morbidly obese renal transplant recipients incur greater costs and readmission rates compared with nonobese patients. Recognition of increased resource utilization should be accompanied by appropriate, risk-adjustment reimbursement.

Metabolic syndrome in liver transplantation: A preoperative and postoperative concern

BACKGROUND

Metabolic syndrome is increasing among patients undergoing liver transplantation. Nonalcoholic steatohepatitis is a manifestation of metabolic syndrome and is an increasingly common cause of end-stage liver disease necessitating orthotopic liver transplantation. We sought to determine the effect of preoperative risk factors on the development of post-transplant metabolic syndrome, complications, readmissions, and mortality.

METHODS

We conducted a review of 114 orthotopic liver transplantations at our institution from May 2012 to April 2014.

RESULTS

Patients with (n = 19) and without (n = 95) metabolic syndrome were similar with regard to age, race, and model for end-stage liver disease at time of transplant. Donor and operative factors also were similar between the groups. Preoperative diabetes was found to be associated with an increased rate of readmission (odds ratio 3.45, P = .03). While preoperative metabolic syndrome itself was not a significant predictor of worse outcomes, postoperative metabolic syndrome was associated with significantly greater readmissions in the first year. Major predictors of new onset metabolic syndrome after orthotopic liver transplantation included preoperative diabetes and obesity (odds ratio 8.54 and odds ratio 5.49, P < .01 each).

CONCLUSION

Efforts to decrease the incidence of postoperative metabolic syndrome after orthotopic liver transplantation may decrease readmissions and improve outcomes, along with decreasing resource utilization.

Acid Sphingomyelinase Inhibition Prevents Hemolysis During Erythrocyte Storage

Background/Aims

During storage, units of human red blood cells (pRBCs) experience membrane destabilization and hemolysis which may cause harm to transfusion recipients. This study investigates whether inhibition of acid sphingomyelinase could stabilize erythrocyte membranes and prevent hemolysis during storage.

Methods

Human and murine pRBCs were stored under standard blood banking conditions with and without the addition of amitriptyline, a known acid sphingomyelinase inhibitor. Hemoglobin was measured with an electronic hematology analyzer and flow cytometry was used to measure erythrocyte size, complexity, phosphatidylserine externalization, and band 3 protein expression.

Results

Cell-free hemoglobin, a marker of hemolysis, increased during pRBC storage. Amitriptyline treatment decreased hemolysis in a dose-dependent manner. Standard pRBC storage led to loss of erythrocyte size and membrane complexity, increased phosphatidylserine externalization, and decreased band 3 protein integrity as determined by flow cytometry. Each of these changes was reduced by treatment with amitriptyline. Transfusion of amitriptyline-treated pRBCs resulted in decreased circulating free hemoglobin.

Conclusion

Erythrocyte storage is associated with changes in cell size, complexity, membrane molecular composition, and increased hemolysis. Acid sphingomyelinase inhibition reduced these changes in a dose-dependent manner. Our data suggest a novel mechanism to attenuate the harmful effects after transfusion of aged blood products.

Role of Leukoreduction of Packed Red Blood Cell Units in Trauma Patients: A Review

Hemorrhagic shock is a leading cause of mortality within the trauma population, and blood transfusion is the standard of care. Leukoreduction filters remove donor leukocytes prior to transfusion of blood products. While the benefits of leukocyte depletion are well documented in scientific literature, these benefits do not translate directly to the clinical setting. This review summarizes current research regarding leukoreduction in the clinical arena, as well as studies performed exclusively in the trauma population.

Molecular mechanisms of erythrocyte aging

Anemia and hemorrhagic shock are leading causes of morbidity and mortality worldwide, and transfusion of human blood products is the ideal treatment for these conditions. As human erythrocytes age during storage in blood banks they undergo many biochemical and structural changes, termed the red blood cell 'storage lesion'. Specifically, ATP and pH levels decrease as metabolic end products, oxidative stress, cytokines, and cell-free hemoglobin increase. Also, membrane proteins and lipids undergo conformational and organizational changes that result in membrane loss, viscoelastic changes and microparticle formation. As a result, transfusion of aged blood is associated with a host of adverse consequences such as decreased tissue perfusion, increased risk of infection, and increased mortality. This review summarizes current research detailing the known parts of the erythrocyte storage lesion and their physiologic consequences.

Risk of Reoperation Within 90 Days of Liver Transplantation: A Necessary Evil?

BACKGROUND

The rate and consequences of reoperation after liver transplantation (LT) are unknown in the United States.

STUDY DESIGN

Adult patients (n = 10,295; 45% of all LT) undergoing LT from 2009 through 2012 were examined using a linkage of the University HealthSystem Consortium and Scientific Registry of Transplant Recipients databases providing recipient, donor, center, hospitalization, and survival details. Median follow-up was 2 years. Reoperations were identified within 90 days after LT.

RESULTS

Overall 90-day reoperation rate after LT was 29.3%. Risk factors for 90-day reoperation included recipients with a history of hemodialysis, severely ill functional status, government insurance, increasing Model for End-Stage Liver Disease score, and increasing donor risk index. Reoperation within 90 days was found to be an independent predictor of adjusted 1-year mortality (odds ratio = 1.8; 95% CI, 1.5-2.1), as was government-provided insurance and increasing donor risk index. Additionally, patients undergoing delayed reoperative intervention (after 30 days) were found to have increased risk of 1-year mortality compared with those undergoing early reoperative intervention (odds ratio = 1.96; 95% CI, 1.4-2.7; p < 0.01).

CONCLUSIONS

This is the first national study reporting that nearly one-third of transplant recipients undergo reoperation within 90 days of LT. Although necessary at times, reoperation is associated with increased risk of death at 1 year; however, it appears that the timing of these interventions can be critical, due to the type of intervention required. Early reoperative intervention does not appear to influence long-term outcomes, and delayed intervention (after 30 days) is strongly associated with decreased survival.

Modulation of endothelial cell migration via manipulation of adhesion site growth using nanopatterned surfaces

Orthogonally functionalized nanopatterend surfaces presenting discrete domains of fibronectin ranging from 92 to 405 nm were implemented to investigate the influence of limiting adhesion site growth on cell migration. We demonstrate that limiting adhesion site growth to small, immature adhesions using sub-100 nm patterns induced cells to form a significantly increased number of smaller, more densely packed adhesions that displayed few interactions with actin stress fibers. Human umbilical vein endothelial cells exhibiting these traits displayed highly dynamic fluctuations in spreading and a 4.8-fold increase in speed compared to cells on nonpatterned controls. As adhesions were allowed to mature in size in cells cultured on larger nanopatterns, 222 to 405 nm, the dynamic fluctuations in spread area and migration began to slow, yet cells still displayed a 2.1-fold increase in speed compared to controls. As all restrictions on adhesion site growth were lifted using nonpatterned controls, cells formed significantly fewer, less densely packed, larger, mature adhesions that acted as terminating sites for actin stress fibers and significantly slower migration. The results revealed an exponential decay in cell speed with increased adhesion site size, indicating that preventing the formation of large mature adhesions may disrupt cell stability thereby inducing highly migratory behavior.

Radiation dose for 345 CT-guided interlaminar lumbar epidural steroid injections

BACKGROUND AND PURPOSE

CT guidance is increasingly being used to localize the epidural space during epidural steroid injections. A common concern is that CT may be associated with significantly higher radiation doses compared with conventional fluoroscopy. The goal of this retrospective study was to determine the average dose-length product and effective dose delivered while interlaminar epidural steroid injections are performed and allow comparison with other modalities.

MATERIALS AND METHODS

A total of 281 patients who had undergone 345 consecutive CT-guided epidural steroid injections of the lumbar spine were evaluated for radiation exposure. The dose-length product for each scan was derived from the CT dose index volume and scan length. Effective dose was then calculated from the dose-length product and a κ coefficient of 0.015. Procedure time was calculated from the PACS time stamp on the scout image to the last CT image of the last image series.

RESULTS

The average dose-length product across all procedures was 89.6 ± 3.33 mGy·cm, which represents an effective dose of 1.34 ± 0.05 mSv. No complications from the procedure were observed, and average procedure time was 8 minutes.

CONCLUSIONS

The use of a stationary table and an intermittent scanning technique allow for short procedures and doses that are significantly lower than those of conventional diagnostic CT scans. Furthermore, because CT dose index overestimates radiation dose in stationary table procedures, the actual radiation dose may be even lower than stated here.

Quality of life of adults with intellectual disabilities who live with families in Taiwan

BACKGROUND

Little research has been conducted about the quality of life (QOL) of people with intellectual disabilities (ID) in Taiwan, particularly their subjective QOL. This study examined the personal perceptions of these individuals as measured on internationally recognized core QOL domains and indicators.

METHODS

A census interview survey was conducted in Hsin-Chu City in Taiwan; 233 adults aged over 16 years with mild ID and living with their families participated in the study. Data were collected using the Cross-Cultural QOL Indicators (CCQOLI) together with socio-demographic data that included 'activities of daily living' and 'instrumental activities of daily living' (IADL). The CCQOLI were based on the three most commonly reported indicators of each of the eight QOL domains: emotional well-being, interpersonal relations, material well-being, personal development, physical well-being, self-determination, social inclusion and rights. Each indicator has two sets of questions related to the indicator's 'importance' and 'use'. These are answered by the respondent using a 4-point Likert scale.

RESULTS

The importance and use of the QOL indicators were evaluated positively by the respondents. The adults' individual characteristics, namely IADL and educational level, were significant predictors for the 'importance' while the adults' perceptions of 'use' for overall QOL were significantly affected by his/her socio-economic data, that is, residence location and father's educational level.

CONCLUSIONS

The present study addressed the issue of self-reported QOL in people with ID in Taiwanese society, becoming a possible benchmark for similar measurements carried out by disability movements there. These results contribute to current advocacy efforts towards creating a supportive environment for people with ID.

Phosphodiesterase A1, a regulator of cellulose synthesis in Acetobacter xylinum, is a heme-based sensor

The phosphodiesterase A1 protein of Acetobacter xylinum, AxPDEA1, is a key regulator of bacterial cellulose synthesis. This phosphodiesterase linearizes cyclic bis(3'-->5')diguanylic acid, an allosteric activator of the bacterial cellulose synthase, to the ineffectual pGpG. Here we show that AxPDEA1 contains heme and is regulated by reversible binding of O(2) to the heme. Apo-AxPDEA1 has less than 2% of the phosphodiesterase activity of holo-AxPDEA1, and reconstitution with hemin restores full activity. O(2) regulation is due to deoxyheme being a better activator than oxyheme. AxPDEA1 is homologous to the Escherichia coli direct oxygen sensor protein, EcDos, over its entire length and is homologous to the FixL histidine kinases over only a heme-binding PAS domain. The properties of the heme-binding domain of AxPDEA1 are significantly different from those of other O(2)-responsive heme-based sensors. The rate of AxPDEA1 autoxidation (half-life > 12 h) is the slowest observed so far for this type of heme protein fold. The O(2) affinity of AxPDEA1 (K(d) approximately 10 microM) is comparable to that of EcDos, but the rate constants for O(2) association (k(on) = 6.6 microM(-)(1) s(-)(1)) and dissociation (k(off) = 77 s(-)(1)) are 2000 times higher. Our results illustrate the versatility of signal transduction mechanisms for the heme-PAS class of O(2) sensors and provide the first example of O(2) regulation of a second messenger.

Production of transforming growth factor alpha by hamster eosinophils

Previously it was demonstrated that malignant transformation of the Syrian hamster cheek pouch mucosa is associated with the expression of TGF-alpha. Therefore in situ hybridization and immunohistochemistry was used to investigate the cellular sources of TGF-alpha production in this model system. Surprisingly one cell type in the inflammatory infiltrate present in the connective tissue adjacent to the transformed epithelium represented a major source of TGF-alpha mRNA. Detailed analysis of these cells revealed that they were eosinophils. In addition to TGF-alpha mRNA, about 40% of the eosinophils associated with the oral tumors exhibited TGF-alpha product reactive with a monoclonal antibody against the C terminus of the mature TGF-alpha peptide. Normal hamster bone marrow eosinophils also exhibited TGF-alpha mRNA and product by in situ hybridization and immunohistochemistry. These results suggest that the eosinophil represents a biologically significant source of TGF-alpha.

A rapid method to determine proliferation patterns of normal and malignant tissues by H3 mRNA in situ hybridization

A general method applicable for the determination of any mammalian tissue's proliferative pattern is described. This method determines the cellular mRNA level of a proliferation-dependent gene, histone H3, by in situ hybridization. The cell-cycle S-phase-specific expression of this highly conserved ubiquitous cellular gene, and the lack of it in resting cells, permits the unambiguous identification of cycling cells in any tissues, normal or diseased. This method can be conveniently coupled with routine biopsy and could be streamlined for a central laboratory with results obtainable in 2 days. Furthermore, this procedure works successfully on formalin-fixed paraffin-embedded sections, thus allowing retrospective studies of biopsies or autopsy materials.

Detection of Ki-ras messenger RNA in normal and chemically transformed hamster oral keratinocytes

The cheek pouch of the Syrian hamster is an excellent model for the experimental study of oral carcinogenesis. The carcinogenic chemical 7,12-dimethylbenz[a]anthracene consistently produces epidermoid carcinomas in the cheek pouch of the Syrian hamster, giving rise to characteristic histopathological lesions in a time-dependent manner. We now present experimental evidence that c-Ki-ras mRNA can be detected in all 7,12-dimethylbenz[a]anthracene-induced tumors examined (in vivo and in vitro) in this experimental oral cancer model while no detectable c-Ki-ras mRNA can be found in the normal hamster cheek pouch epithelium. Cellular synchronization experiments using a cell line (hamster cheek pouch carcinoma cell line 1) derived from one of these 7,12-dimethylbenz[a]anthracene-induced hamster oral tumors revealed that the c-Ki-ras protooncogene is expressed during the G1 phase of the cell cycle (proliferation dependent). Serum starvation and RNA synthesis inhibition experiments using hamster cheek pouch carcinoma cell line 1 cells suggest that the c-Ki-ras protooncogene is indeed quiescent in the normal hamster cheek pouch epithelium and that failure to detect its mRNA is not related to the slower proliferation of the normal epithelial cells. These results suggest that the transcription of the c-Ki-ras protooncogene is associated with malignant transformation in the cheek pouch of the Syrian hamster.

TGF-alpha and EGF-receptor mRNAs in human oral cancers

Transforming growth factor alpha (TGF-alpha) and epidermal growth factor receptor (EGFR) have been shown to be present in most squamous cell carcinomas. Using the Syrian hamster oral cancer model, we have recently demonstrated the consistent presence of TGF-alpha and EGFR mRNAs in chemically transformed hamster oral keratinocytes. We now present evidence that in human oral cancer (in vivo and in vitro), TGF-alpha and EGFR mRNAs can also be consistently detected. No TGF-alpha mRNA can be detected in normal human oral epithelium by Northern blot analysis. These findings reinforce the use of the hamster cheek pouch as an experimental model for the study of oral cancer development, at least in reference to the possible participation of TGF-alpha in the malignant transformation process.

Transforming growth factor alpha in chemically transformed hamster oral keratinocytes

The cheek pouch of the Syrian hamster is an excellent tissue for the experimental induction of oral cancer by carcinogenic chemicals. Lysate prepared from a cell line (HCPC-1) derived from one of these hamster oral tumors greatly increased the growth of these oral tumor cells in vitro. We now show that the mitogenic substance, transforming growth factor alpha (TGF-alpha), is present in all of the chemically transformed hamster oral tumors examined (in vitro and in vivo). In no adult normal tissue of the Syrian hamster can we detect expression of TGF-alpha. TGF-alpha could be partly or wholly responsible for the mitogenic activity detected in the lysate of the chemically transformed hamster oral keratinocytes. Both normal and chemically transformed hamster oral keratinocytes express the receptor to epidermal growth factor. The consistent detection of TGF-alpha and epidermal growth factor receptor mRNAs in these hamster oral tumor cells suggests that an autocrine growth mechanism might be operative. This hamster cheek pouch oral cancer model can be used for the molecular analysis of how TGF-alpha and epidermal growth factor receptor might be involved in the malignant transformation of epithelial tissues.