EUS-guided management of anastomotic stricture: A case report

INTRODUCTION AND IMPORTANCE

Anastomotic stenosis after low anterior resection is a serious complication and at times even requires surgical revision of the anastomosis.

CASE PRESENTATION AND CLINICAL DISCUSSION

The patient presented with a 4.0 cm tubulovillous adenoma of the proximal rectum and underwent low anterior resection with loop ileostomy and subsequent reversal. The case was complicated by complete anastomotic stenosis. A novel technique was utilized to create an Endoscopic Ultrasound (EUS)-guided neo-anastomosis endoscopically.

CONCLUSION

EUS-guided creation of a neo-colorectal anastomosis is a safe and effective alternative to surgical anastomosis revision of a completely stenosed anastomosis.

Events, care, and outcomes after hernia mesh explantation for infection

BACKGROUND

Mesh explantation for infection after hernia surgery sets a cascade of events that has not been previously described. The purpose of this study is to review the care of these patients and outcomes.

METHODS

We obtained data on all Veterans Health Administration enrollees undergoing hernia repair during 2008-2015. All mesh explantation cases were identified and manually reviewed through December 2020 to identify surgical site occurrences, re-repairs, and subsequent explantations.

RESULTS

We identified 332 index explantations due to infection. A first subsequent repair was performed in 82.5% (274/332); a second repair in 18.2% (50/274); a third repair in 16.0% (8/50); and a fourth repair in 25% (2/8). Overall recurrence rate over a 12 year-period was 160/332 (48.1%).

CONCLUSIONS

Mesh explantation due to infection sets a cascade of complications and hernia recurrences necessitating re-operation. Complications resulting from mesh explantation suggest that resolution of the initial abdominal wall infection is crucial to prevent future mesh infections.

Re-Infection after Explantation of Infected Hernia Mesh: Are the Same Micro-Organisms Involved?

Background: It is unclear if a history of mesh explantation for infection is predictive of future microbiology after subsequent hernia operations. We investigated how often the same causative organism is cultured in the initial explantation and subsequent repairs. Patients and Methods: We obtained data on patients undergoing ventral/incisional, umbilical, and inguinal hernia repairs from the Veterans Affairs Surgical Quality Improvement Program during 2008-2015. Manual review was performed for all patients with an administrative code indicative of mesh explantation and those with explantation for infection were retained. We then obtained data on cultured organisms from the mesh site at the time of index explantation and at any re-repair or subsequent explantation during a follow-up period ending in December 2020. Results: We identified 332 patients undergoing mesh explantation because of infection (64.8% ventral, 18.7% umbilical, 16.6% inguinal). Mean age was 60.3 years (standard deviation [SD], 9.7) and 93.9% were male. The same organism was cultured at re-infection in 23 of 59 (39%) cases. Gram-positive micro-organisms were the most prevalent in 20 of 23 (87%). Among the gram-positive, Staphylococcus aureus was the most common pathogen and was cultured in 18 of 20 (90%) cases, of which 14 of 18 (77.8%) were methicillin-susceptible Staphylococcus aureus (MSSA) and 4 of 18 (22.2%) were methicillin-resistant Staphylococcus aureus (MRSA). Three of 23 (13%) gram-negative organisms were the same at both re-infection and index explantation consisting of Escherichia coli in 2 of 3 (66.7%), and Pseudomonas aeruginosa in one of three (33.3%). Conclusions: Identification of organisms at time of prosthetic infection is helpful not only in treating the initial infection, but also in prevention of infection with the same organisms after subsequent repairs. Same organism re-infection should not be underestimated, particularly when Staphylococcus aureus is isolated.

Association of Postoperative Infection With Risk of Long-term Infection and Mortality

Importance

Surgical site infection has been shown to decrease survival in veterans by up to 42%. The association of 30-day postoperative infections with long-term infections in the overall surgical population remains unknown.

Objective

To determine whether exposure to 30-day postoperative infection is associated with increased incidence of infection and mortality during postoperative days 31 to 365.

Design, Setting, and Participants

In this retrospective observational cohort study, veterans undergoing major surgery through the Veterans Health Administration from January 2008 to December 2015 were included. Stabilized inverse probability of treatment weighting was used to balance baseline characteristics of the control and exposure groups. Cox proportional hazards regression was used to estimate hazard ratios of long-term infection and mortality. Data were analyzed from September 2018 to May 2019.

Exposures

Any 30-day postoperative infection (exposure group) vs no 30-day infection (control group).

Main Outcomes and Measures

Number of days between index surgery and the occurrence of death or the patient's first infection during postoperative days 31 to 365. Patients who died before having a long-term infection were censored for the infection outcome.

Results

Of the 659 486 included patients, 604 534 (91.7%) were male, and the mean (SD) age was 59.7 (13.6) years. Among these patients, 23 815 (3.6%) had a 30-day infection, 43 796 (6.6%) had a long-term infection, and 24 810 (3.8%) died during follow-up. The most frequent 30-day infections were surgical site infection (9574 [40.2%]), urinary tract infection (6545 [27.5%]), pneumonia (3515 [14.8%]), and bloodstream infection (1906 [8.0%]). Long-term infection types included urinary tract infection (21 420 [48.7%]), skin and soft tissue infection (14 348 [32.6%]), bloodstream infection (3862 [8.8%]), and pneumonia (2543 [5.8%]). Patients in the exposure group had a higher observed incidence of long-term infection (5187 of 23 815 [21.8%]) and mortality (3067 of 23 815 [12.9%]) compared with those without 30-day infection (38 789 of 635 671 [6.1%] and 21 743 of 635 671 [3.4%], respectively). The estimated hazard ratio for long-term infection was 3.17 (95% CI, 3.05-3.28) and for mortality was 1.89 (95% CI, 1.79-1.99).

Conclusions and Relevance

At any given point during the follow-up period, patients with 30-day postoperative infection had a 3.2-fold higher risk of 1-year infection and a 1.9-fold higher risk of mortality compared with those who had no 30-day infection. Cost-benefit calculations for surgical infection prevention programs should include the increased risk and costs of long-term infection and death. Preventive efforts in the first 30 days postoperatively may improve long-term patient outcomes.

Incidence and Risk Factors for Long-Term Mesh Explantation Due to Infection in More than 100,000 Hernia Operation Patients

BACKGROUND

Infectious complications after hernia operation are potentially disastrous, often requiring long-term antibiotic administration, debridement, and mesh explantation. Our objective was to describe the long-term incidence and risk factors for synthetic mesh explantation due to infection after hernia operation in a large cohort.

STUDY DESIGN

Retrospective database study using Veterans Affairs Surgical Quality Improvement Program and chart review of veterans undergoing abdominal or groin hernia repair with synthetic mesh implantation during 2008-2015. The main outcome was mesh explantation due to infection within 5 years.

RESULTS

The study population consisted of 103,869 hernia operations, of which 74.3% were inguinal, 10.7% umbilical, and 15.0% ventral. Explantation incidence was highest among ventral (1.5%). Median explantation interval overall was 208 days. In multivariable logistic regression, all obesity levels from pre-obesity to obesity class III were associated with higher explantation risk. American Society of Anesthesiology physical status classification of 3 to 5 was associated with odds ratio (OR) of 1.7 (95% CI, 1.28 to 2.26), as was longer operative duration (OR 1.83; 95% CI, 1.51 to 2.21), and contaminated or dirty surgical wound classification (OR 2.27; 95% CI, 1.11 to 4.64). Umbilical repair (OR 6.11; 95% CI, 4.14 to 9.02) and ventral repair (OR 14.35; 95% CI, 10.39 to 19.82) were associated with higher risk compared with inguinal. Open repair was associated with a higher risk compared with laparoscopic (OR 3.57; 95% CI, 2.52 to 5.05). Deep incisional surgical site infection within 30 days of operation was more likely to result in long-term mesh explantation (29.2%) than either superficial (6.4%) or organ space infection (22.4%).

CONCLUSIONS

Mesh explantation for infection is most common after ventral hernia repair. Risk factor optimization is crucial to minimize such an end point.

Comparing cataract surgery complication rates in veterans receiving VA and community care

OBJECTIVES

To compare 90-day postoperative complication rates between Veterans receiving cataract surgery in VA vs Community Care (CC) during the first year of implementation of the Veterans Choice Act.

DATA SOURCES

Fiscal Year (FY) 2015 VA and CC outpatient data from VA's Corporate Data Warehouse (CDW) 10/01/14-9/30/15). FY14 data were used to obtain baseline clinical information prior to surgery.

STUDY DESIGN

Retrospective one-year study using secondary data to compare 90-day complication rates following cataract surgery (measured using National Quality Forum (NQF) criteria) in VA vs CC. NQF defines major complications from a specified list of Current Procedural Terminology (CPT) codes. We ran a series of logistic regression models to predict 90-day complication rates, adjusting for Veterans' sociodemographic characteristics, comorbidities, preoperative ocular conditions, eye risk group, and type of cataract surgery (classified as routine vs complex).

DATA COLLECTION

We linked VA and CC users through patient identifiers obtained from the CDW files. Our sample included all enrolled Veterans who received outpatient cataract surgery either in the VA or through CC during FY15. Cataract surgeries were identified through CPT codes 66 984 (routine) and 66 982 (complex).

PRINCIPAL FINDINGS

Of the 83,879 cataract surgeries performed in FY15, 31 percent occurred through CC. Undergoing complex surgery and having a high-risk eye (based on preoperative ocular conditions) were the strongest clinical predictors of 90-day postoperative complications. Overall, we found low complication rates, ranging from 1.1 percent in low-risk eyes to 3.6 percent in high-risk eyes. After adjustment for important confounders (eg, race, rurality, and preoperative ocular conditions), there were no statistically significant differences in 90-day complication rates between Veterans receiving cataract surgery in VA vs CC.

CONCLUSIONS

As more Veterans seek care through CC, future studies should continue to monitor quality of care across the two care settings to help inform VA's "make vs buy decisions."

Interaction of Alpha-Crystallin with Phospholipid Membranes

Purpose/Aim: The amount of membrane-bound α-crystallin increases significantly with age and cataract formation, accompanied by a corresponding decline in the level of α-crystallin in the lens cytoplasm. The purpose of this research is to evaluate the binding affinity of α-crystallin to the phospholipid membranes as well as the physical properties of the membranes after α-crystallin binding. Materials and Methods: The continuous wave and saturation recovery electron paramagnetic resonance (EPR) methods were used to obtain the information about the binding affinity and the physical properties of the membrane. In this approach, the cholesterol analog spin label CSL was incorporated in the membrane and the binding of α-crystallin to the membrane was monitored by this spin label. Small uni-lamellar vesicles were prepared from 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) with 1% of CSL. The measured membrane properties included the mobility parameter, fluidity, and the oxygen transport parameter. Results: The binding affinity (K_a ) of α-crystallin with the POPC membrane was estimated to be 4.9 ± 2.4 µM^-1. The profiles of mobility parameter showed that mobility parameter decreased with an increase in the binding of α-crystallin. The profiles of spin-lattice relaxation rate showed that the spin-lattice relaxation rate decreased with an increase in binding. These results show that the binding of α-crystallin makes the membrane more immobilized near the head group region of the phospholipids. Furthermore, the profiles of the oxygen transport parameter indicated that the oxygen transport parameter decreased with an increase of binding, indicating the binding of α-crystallin forms a barrier for the passage of non-polar molecules which supports the barrier hypothesis. Conclusions: The binding of α-crystallin to the membrane alters the physical properties of the membranes, and this plays a significant role in modulating the integrity of the membranes. EPR techniques are useful in studying α-crystallin membrane interactions.

Data on highway maintenance, rehabilitation, and mobility projects for integrated planning in Texas

State Highway Agencies (SHAs) have different functional groups that work towards improving the functional and physical performance of highway assets. These functional groups often propose multiple inter-related highway projects on the same network. However, the respective information systems of such functional groups lack interoperability capabilities between them. This data article is related to an earlier study by France-Mensah et al. (France-Mensah et al., 2017) that explored the integrated visualization of highway projects proposed by different functional groups working in the same highway agency. This dataset provides a spatially integrated set of maintenance and capital planning projects which is rarely available due to organizational silos which often exist in highway agencies. The data includes approximately 700 highway projects with over 16 attributes that includes spatial, temporal, cost, and description attributes. The highway projects are located in the Fort Worth District of the Texas Department of Transportation (TxDOT) which is responsible for a large network (approximately 9000 lane miles) of highway assets. The agency currently oversees around $4 billion in construction projects and spends around $120 million annually for asset preservation. An analysis of the fund allocations categorized by different project types for pavement and bridge assets is presented. The data presented can be used to compare competing approaches or policies for cross-asset allocation, spatial-temporal projects coordination, and safety planning in the infrastructure management domain.

Differences in Risk Scores of Veterans Receiving Community Care Purchased by the Veterans Health Administration

OBJECTIVE

To assess differences in risk (measured by expected costs associated with sociodemographic and clinical profiles) between Veterans receiving outpatient services through two community care (CC) programs: the Fee program ("Fee") and the Veterans Choice Program ("Choice").

DATA SOURCES/STUDY SETTING

Administrative data from VHA's Corporate Data Warehouse in fiscal years (FY) 2014-2015.

STUDY DESIGN

We compared the clinical characteristics of Veterans across three groups (Fee only, Choice only, and Fee & Choice). We classified Veterans into risk groups based on Nosos risk scores and examined the relationship between type of outpatient utilization and risk within each CC group. We also examined changes in utilization of VHA and CC in FY14-FY15. We used chi-square tests, t tests, and ANOVAs to identify significant differences between CC groups.

PRINCIPAL FINDINGS

Of the 1,400,977 Veterans using CC in FY15, 91.4 percent were Fee-only users, 4.4 percent Choice-only users, and 4.2 percent Fee & Choice users. Mean concurrent risk scores were higher for Fee only and Fee & Choice (1.9, SD = 2.7; 1.8, SD = 2.2) compared to Choice-only users (1.0, SD = 1.2) (p < .0001). Most CC users were "dual users" of both VHA and CC in FY14-FY15.

CONCLUSIONS

As care transitions from VHA to CC, VHA should consider how best to coordinate care with community providers to reduce duplication of efforts, improve handoffs, and achieve the best outcomes for Veterans.

Detection of cholesterol bilayer domains in intact biological membranes: Methodology development and its application to studies of eye lens fiber cell plasma membranes

Four purported lipid domains are expected in plasma membranes of the eye lens fiber cells. Three of these domains, namely, bulk, boundary, and trapped lipids, have been detected. The cholesterol bilayer domain (CBD), which has been detected in lens lipid membranes prepared from the total lipids extracted from fiber cell plasma membranes, has not yet been detected in intact fiber cell plasma membranes. Here, a saturation-recovery electron paramagnetic resonance spin-labeling method has been developed that allows identification of CBDs in intact fiber cell plasma membranes of eye lenses. This method is based on saturation-recovery signal measurements of the cholesterol-analog spin label located in the lipid bilayer portion of intact fiber cell membranes as a function of the partial pressure of molecular oxygen with which the samples are equilibrated. The capabilities and limitations of this method are illustrated for intact cortical and nuclear fiber cell plasma membranes from porcine eye lenses where CBDs were detected in porcine nuclear intact membranes for which CBDs were also detected in lens lipid membranes. CBDs were not detected in porcine cortical intact and lens lipid membranes. CBDs were detected in intact membranes isolated from both cortical and nuclear fiber cells of lenses obtained from human donors. The cholesterol content in fiber cell membranes of these donors was always high enough to induce the formation of CBDs in cortical as well as nuclear lens lipid membranes. The results obtained for intact membranes, when combined with those obtained for lens lipid membranes, advance our understanding of the role of high cholesterol content and CBDs in lens biology, aging, and/or cataract formation.

Factors Associated with Hospital Admission after Outpatient Surgery in the Veterans Health Administration

OBJECTIVE

To examine factors associated with 0- to 7-day admission after outpatient surgery in high-volume specialties: general surgery, orthopedics, urology, ear/nose/throat, and podiatry.

STUDY DESIGN

We calculated rates and assessed diagnosis codes for 0- to 7-day admission after outpatient surgery for Centers for Medicare and Medicaid Services (CMS) and Veterans Health Administration (VA) dually enrolled patients age 65 and older. We also estimated separate multilevel logistic regression models to compare patient, procedure, and facility characteristics associated with postoperative admission.

DATA COLLECTION

2011-2013 surgical encounter data from the VA Corporate Data Warehouse; geographic data from the Area Health Resources File; CMS enrollment and hospital admission data.

PRINCIPAL FINDINGS

Among 63,585 outpatient surgeries in 124 facilities, 0- to 7-day admission rates ranged from 5 percent (podiatry) to 28 percent (urology); nearly 66 percent of the admissions occurred on the day of surgery. Only 97 admissions were detected in the CMS data (1 percent). Surgical complications were diagnosed in 4 percent of admissions. Procedure complexity, measured by relative value units or anesthesia risk score, was associated with admission across all specialties.

CONCLUSION

As many as 20 percent of VA outpatient surgeries result in an admission. Complex procedures are more likely to be followed by admission, but more evidence is required to determine how many of these reflect potential safety or quality problems.

Factors Associated With Long-term Outcomes of Umbilical Hernia Repair

Importance

Umbilical hernia repair is one of the most commonly performed general surgical procedures. However, there is little consensus about the factors that lead to umbilical hernia recurrence.

Objective

To better understand the factors associated with long-term umbilical hernia recurrence.

Design, Setting, and Participants

A retrospective cohort of 332 military veteran patients who underwent umbilical hernia repair was studied between January 1, 1998, and December 31, 2008, at the VA Boston Healthcare System. Recurrence and mortality outcomes were tracked from that period until June 1, 2014. Data were collected on patient characteristics, operative, and postoperative factors and univariate and multivariable analyses were used to assess which factors were significantly associated with umbilical hernia recurrence and mortality. All patients with primary umbilical hernia repair, with or without a concurrent unrelated procedure, were included in the study. Patients excluded were those who underwent umbilical hernia repair as a part of another major planned procedure with abdominal incisions. Data were collected from June 1, 2014, to November 1, 2015. Statistical analysis was performed from November 2, 2015, to April 1, 2016.

Main Outcomes and Measures

The primary study outcomes were umbilical hernia recurrence and death.

Results

Of the 332 patients in this study, 321 (96.7%) were male, mean age was 58.4 years, and mean (SD) time of follow-up was 8.5 (4.1) years. The hernia recurrence rate was 6.0% (n = 20) at a mean 3.1 years after index repair (median, 1.0-year; range, 0.33-13 years). The primary suture repair recurrence rate was 9.8% (16 of 163 patients), and the mesh repair recurrence rate was 2.4% (4 of 169 patients). On univariate analysis, ascites (P = .02), liver disease (P = .02), diabetes (P = .04), and primary suture (nonmesh) repairs (P = .04) were significantly associated with increased recurrence rates. Patients who had a history of hernias (125 [39%]) were less likely to have umbilical hernia recurrences (χ21 = 4.65, P = .03). On multivariable regression analysis, obesity and ascites were associated with significantly increased odds ratios of recurrence of 3.3 (95% CI, 1.0-10.1) and 8.0 (95% CI, 1.8-34.4), respectively. Mesh repair was seen to decrease recurrence with odds of 0.28 (95% CI, 0.08-0.95). There was no significant difference in complication rates between mesh repair and primary suture repair. The survival rate was 73% (n = 242) at the end of the study. Factors associated with mortality were older age, smoking, liver disease, ascites, emergency or semiurgent repair, and need for intraoperative bowel resection.

Conclusions and Relevance

Ascites, liver disease, diabetes, obesity, and primary suture repair without mesh are associated with increased umbilical hernia recurrence rates. Elective umbilical hernia repair with mesh should be considered in patients with multiple comorbidities given that the use of mesh offers protection from recurrence without major morbidity.

Organization of lipids in fiber-cell plasma membranes of the eye lens

The plasma membrane together with the cytoskeleton forms the only supramolecular structure of the matured fiber cell which accounts for mostly all fiber cell lipids. The purpose of this review is to inform researchers about the importance of the lipid bilayer portion of the lens fiber cell plasma membranes in the maintaining lens homeostasis, and thus protecting against cataract development.

What is the value of adding Medicare data in estimating VA hospital readmission rates?

OBJECTIVE

To determine the effects of including diagnostic and utilization data from a secondary payer on readmission rates and hospital profiles.

DATA SOURCES/STUDY SETTING

Veterans Health Administration (VA) and Medicare inpatient and outpatient administrative data for veterans discharged from 153 VA hospitals during FY 2008-2010 with a principal diagnosis of acute myocardial infarction, heart failure, or pneumonia.

STUDY DESIGN

We estimated hospital-level risk-standardized readmission rates derived using VA data only. We then used data from both VA and Medicare to reestimate readmission rates and compared hospital profiles using two methods: Hospital Compare and the CMS implementation of the Hospital Readmissions Reduction Program (HRRP).

DATA COLLECTION/EXTRACTION METHODS

Retrospective data analysis using VA hospital discharge and outpatient data matched with Medicare fee-for-service claims by scrambled Social Security numbers.

PRINCIPAL FINDINGS

Less than 2 percent of hospitals in any cohort were classified discordantly by the Hospital Compare method when using VA-only compared with VA/Medicare data. In contrast, using the HRRP method, 13 percent of hospitals had differences in whether they were flagged as having excessive readmission rates in at least one cohort.

CONCLUSIONS

Inclusion of secondary payer data may cause changes in hospital profiles, depending on the methodology used. An assessment of readmission rates should include, to the extent possible, all available information about patients' utilization of care.

Lipid domains in intact fiber-cell plasma membranes isolated from cortical and nuclear regions of human eye lenses of donors from different age groups

The results reported here clearly document changes in the properties and the organization of fiber-cell membrane lipids that occur with age, based on electron paramagnetic resonance (EPR) analysis of lens membranes of clear lenses from donors of age groups from 0 to 20, 21 to 40, and 61 to 80 years. The physical properties, including profiles of the alkyl chain order, fluidity, hydrophobicity, and oxygen transport parameter, were investigated using EPR spin-labeling methods, which also provide an opportunity to discriminate coexisting lipid domains and to evaluate the relative amounts of lipids in these domains. Fiber-cell membranes were found to contain three distinct lipid environments: bulk lipid domain, which appears minimally affected by membrane proteins, and two domains that appear due to the presence of membrane proteins, namely boundary and trapped lipid domains. In nuclear membranes the amount of boundary and trapped phospholipids as well as the amount of cholesterol in trapped lipid domains increased with the donors' age and was greater than that in cortical membranes. The difference between the amounts of lipids in domains uniquely formed due to the presence of membrane proteins in nuclear and cortical membranes increased with the donors' age. It was also shown that cholesterol was to a large degree excluded from trapped lipid domains in cortical membranes. It is evident that the rigidity of nuclear membranes was greater than that of cortical membranes for all age groups. The amount of lipids in domains of low oxygen permeability, mainly in trapped lipid domains, were greater in nuclear than cortical membranes and increased with the age of donors. These results indicate that the nuclear fiber cell plasma membranes were less permeable to oxygen than cortical membranes and become less permeable to oxygen with age. In clear lenses, age-related changes in the lens lipid and protein composition and organization appear to occur in ways that increase fiber cell plasma membrane resistance to oxygen permeation.

High-throughput assays for superoxide and hydrogen peroxide: design of a screening workflow to identify inhibitors of NADPH oxidases

Recent progress characterizing the reaction mechanism(s) of fluorescent probes with reactive oxygen species has made it possible to rigorously analyze these reactive species in biological systems. We have developed rapid high throughput-compatible assays for monitoring cellular production of superoxide radical anion and hydrogen peroxide using hydropropidine and coumarin boronic acid probes, respectively. Coupling plate reader-based fluorescence measurements with HPLC-based simultaneous monitoring of superoxide radical anion and hydrogen peroxide provides the basis for the screening protocol for NADPH oxidase (Nox) inhibitors. Using this newly developed approach along with the medium-throughput plate reader-based oximetry and EPR spin trapping as confirmatory assays, it is now eminently feasible to rapidly and reliably identify Nox enzyme inhibitors with a markedly lower rate of false positives. These methodological advances provide an opportunity to discover selective inhibitors of Nox isozymes, through enhanced conceptual understanding of their basic mechanisms of action.

Lipid-protein interactions in plasma membranes of fiber cells isolated from the human eye lens

The protein content in human lens membranes is extremely high, increases with age, and is higher in the nucleus as compared with the cortex, which should strongly affect the organization and properties of the lipid bilayer portion of intact membranes. To assess these effects, the intact cortical and nuclear fiber cell plasma membranes isolated from human lenses from 41- to 60-year-old donors were studied using electron paramagnetic resonance spin-labeling methods. Results were compared with those obtained for lens lipid membranes prepared from total lipid extracts from human eyes of the same age group [Mainali, L., Raguz, M., O'Brien, W. J., and Subczynski, W. K. (2013) Biochim. Biophys. Acta]. Differences were considered to be mainly due to the effect of membrane proteins. The lipid-bilayer portions of intact membranes were significantly less fluid than lipid bilayers of lens lipid membranes, prepared without proteins. The intact membranes were found to contain three distinct lipid environments termed the bulk lipid domain, boundary lipid domain, and trapped lipid domain. However, the cholesterol bilayer domain, which was detected in cortical and nuclear lens lipid membranes, was not detected in intact membranes. The relative amounts of bulk and trapped lipids were evaluated. The amount of lipids in domains uniquely formed due to the presence of membrane proteins was greater in nuclear membranes than in cortical membranes. Thus, it is evident that the rigidity of nuclear membranes is greater than that of cortical membranes. Also the permeability coefficients for oxygen measured in domains of nuclear membranes were significantly lower than appropriate coefficients measured in cortical membranes. Relationships between the organization of lipids into lipid domains in fiber cells plasma membranes and the organization of membrane proteins are discussed.

Properties of fiber cell plasma membranes isolated from the cortex and nucleus of the porcine eye lens

The organization and physical properties of the lipid bilayer portion of intact cortical and nuclear fiber cell plasma membranes isolated from the eye lenses of two-year-old pigs were studied using electron paramagnetic resonance (EPR) spin-labeling. Membrane fluidity, hydrophobicity, and the oxygen transport parameter (OTP) were assessed from the EPR spectra of precisely positioned spin labels. Intact cortical and nuclear membranes, which include membrane proteins, were found to contain three distinct lipid environments. These lipid environments were termed the bulk lipid domain, boundary lipid domain, and trapped lipid domain (lipids in protein aggregates). The amount of boundary and trapped lipids was greater in intact nuclear membranes than in cortical membranes. The properties of intact membranes were compared with the organization and properties of lens lipid membranes made of the total lipid extracts from the lens cortex or nucleus. In cortical lens lipid membranes, only one homogenous environment was detected, which was designated as a bulk lipid domain (phospholipid bilayer saturated with cholesterol). Lens lipid membranes prepared from the lens nucleus possessed two domains, assigned as a bulk lipid domain and a cholesterol bilayer domain (CBD). In intact nuclear membranes, it was difficult to discriminate the CBD, which was clearly detected in nuclear lens lipid membranes, because the OTP measured in the CBD is the same as in the domain formed by trapped lipids. The two domains unique to intact membranes-namely, the domain formed by boundary lipids and the domain formed by trapped lipids-were most likely formed due to the presence of membrane proteins. It is concluded that formation of rigid and practically impermeable domains is enhanced in the lens nucleus, indicating changes in membrane composition that may help to maintain low oxygen concentration in this lens region.

Fluorocyclines. 2. Optimization of the C-9 side-chain for antibacterial activity and oral efficacy

Utilizing a fully synthetic route to tetracycline analogues, the C-9 side-chain of the fluorocyclines was optimized for both antibacterial activity and oral efficacy. Compounds were identified that overcome both efflux (tet(K), tet(A)) and ribosomal protection (tet(M)) tetracycline-resistance mechanisms and are active against Gram-positive and Gram-negative organisms. A murine systemic infection model was used as an oral efficacy screen to rapidly identify compounds with oral bioavailability. Two compounds were identified that exhibit both oral bioavailability in rat and clinically relevant bacterial susceptibility profiles against major respiratory pathogens. One compound demonstrated oral efficacy in rodent lung infection models that was comparable to marketed antibacterial agents.

Fluorocyclines. 1. 7-fluoro-9-pyrrolidinoacetamido-6-demethyl-6-deoxytetracycline: a potent, broad spectrum antibacterial agent

This and the accompanying report (DOI: 10.1021/jm201467r ) describe the design, synthesis, and evaluation of a new generation of tetracycline antibacterial agents, 7-fluoro-9-substituted-6-demethyl-6-deoxytetracyclines ("fluorocyclines"), accessible through a recently developed total synthesis approach. These fluorocyclines possess potent antibacterial activities against multidrug resistant (MDR) Gram-positive and Gram-negative pathogens. One of the fluorocyclines, 7-fluoro-9-pyrrolidinoacetamido-6-demethyl-6-deoxytetracycline (17j, also known as TP-434, 50th Interscience Conference on Antimicrobial Agents and Chemotherapy Conference , Boston, MA , September 12-15, 2010 , poster F1 - 2157 ), is currently undergoing phase 2 clinical trials in patients with complicated intra-abdominal infections (cIAI).

Synthesis and antibacterial activity of pentacyclines: a novel class of tetracycline analogs

Employing a highly efficient total synthesis approach, we synthesized and evaluated for antibacterial activity diverse and novel pentacycline analogs with systematic variations at C7, C8, C9, and C10. Certain substitution groups, as well as substitution patterns at various positions, were found to be preferred for increased antibacterial activity. A number of pentacycline analogs displayed potent activity in vitro and in vivo, especially against Gram-positive organisms. Several analogs have also shown promising oral bioavailability in rats and cynomolgus monkey.

Mitochondrial dysfunction links ceramide activated HRK expression and cell death

Purpose

Cell death is an essential process in normal development and homeostasis. In eyes, corneal epithelial injury leads to the death of cells in underlying stroma, an event believed to initiate corneal wound healing. The molecular basis of wound induced corneal stromal cell death is not understood in detail. Studies of others have indicated that ceramide may play significant role in stromal cell death following LASIK surgery. We have undertaken the present study to investigate the mechanism of death induced by C6 ceramide in cultures of human corneal stromal (HCSF) fibroblasts.

Methods

Cultures of HCSF were established from freshly excised corneas. Cell death was induced in low passage (p<4) cultures of HCSF by treating the cells with C6 ceramide or C6 dihydroceramide as a control. Cell death was assessed by Live/Dead cell staining with calcein AM and ethidium homodimer-1 as well as Annexin V staining, caspase activation and TUNEL staining Mitochondrial dysfunction was assessed by Mito Sox Red, JC-1 and cytochrome C release Gene expression was examined by qPCR and western blotting.

Results

Our data demonstrate ceramide caused mitochondrial dysfunction as evident from reduced MTT staining, cyto c release from mitochondria, enhanced generation of ROS, and loss in mitochondrial membrane potential (ΔΨ_m). Cell death was evident from Live -Dead Cell staining and the inability to reestablish cultures from detached cells. Ceramide induced the expression of the harikari gene(HRK) and up-regulated JNK phosphorylation. In ceramide treated cells HRK was translocated to mitochondria, where it was found to interact with mitochondrial protein p32. The data also demonstrated HRK, p32 and BAD interaction. Ceramide-induced expression of HRK, mitochondrial dysfunction and cell death were reduced by HRK knockdown with HRK siRNA.

Conclusion

Our data document that ceramide is capable of inducing death of corneal stromal fibroblasts through the induction of HRK mediated mitochondria dysfunction.

8-Azatetracyclines: synthesis and evaluation of a novel class of tetracycline antibacterial agents

A novel series of fully synthetic 8-azatetracyclines was prepared and evaluated for antibacterial activity. Compounds were identified that overcome both efflux (tet(K)) and ribosomal protection (tet(M)) tetracycline resistance mechanisms and are active against Gram-positive and Gram-negative organisms. Two compounds were identified that exhibit comparable efficacy to marketed tetracyclines in in vivo models of bacterial infection.

Estimation of visual shade matching errors with 2 shade guides

OBJECTIVE

To compare the interobserver difference in visual shade matching and estimate the precision of color discrimination.

METHOD AND MATERIALS

Visual shade matching of a maxillary central incisor of 33 subjects was performed by 2 prosthodontists independently in a chair under ceiling daylight-corrected fluorescent lighting, using the Vitapan Classical and the Vitapan 3D Master shade guides (Vita Zahnfabrik). The 3 closest shade tabs were selected and ranked in order of best, second best, and third best matches. Interobserver agreement was found by comparing the best shade and the common shade for each subject by the 2 clinicians. The CIE Lab color difference, DeltaE*, between the best shade and the common shade selected by the clinicians was calculated for each subject. A t test (alpha = .05) was performed to find clinician differences of the means of the best shade and the common shade for both shade guides.

RESULTS

Interobserver agreement was 30% when matching the best shade; however, the ratio increased to over 85% for the common shade (a significant difference at the .05 level). No significant differences were found between the 2 shade guides by means of the mean color differences between the best shade match and the common shade match, while the Vitapan 3D Master shade guide was superior to the Vitapan Classical shade guide in reducing the interobserver color differences from 0.8 to 0.2.

CONCLUSION

Visual shade matching of teeth gave better agreement using the Vitapan 3D Master shade guide when selecting the common shade from among the closest 3 shades chosen by multiple observers.

Mechanisms of goniochromism relevant to restorative dentistry

OBJECTIVES

This study aims to determine the effects of multiple translucent layers, the alignment of composite structures, and specular reflecting backings as goniochromatic mechanisms relevant to dentistry.

METHODS

Rectangular composite specimens were filled with very short E-glass fibers (120 microm length, 16 microm diameter). The fibers were oriented random, perpendicular, and parallel to the surface normal using an electric field. A Minolta CS-100 colorimeter was used to measure the color at various angles of samples with various filler alignments, translucent sublayers, and specular reflecting backings.

RESULTS

All three investigated mechanisms were proven to have a goniochromatic effect. Filler alignment perpendicular to the surface made the composites more transmissive and reduced the dependence of lightness on observation angle. Backing composites with a pigmented sublayer caused the color of the sublayer to be more apparent when the observation angle is perpendicular to the surface. The specular reflection of a gold backing was only partially diffused by the specimen.

SIGNIFICANCE

The determination of the effects of these goniochromatic mechanisms is relevant to dentistry, because teeth are naturally aligned composites composed of multiple translucent layers. Therefore, understanding these goniochromatic effects is important to recreating them in restorative materials. Also, gold backings were previously found to give restoratives a more vital appearance, and this perceived vitality may be related to goniochromism.

Expression of NADPH oxidase in rabbit corneal epithelial and stromal cells in culture

PURPOSE

Reactive oxygen- and nitrogen-containing molecules produced in high concentrations are mediators of tissue damage caused by inflammation. The free radical molecules superoxide (O2-*) and nitric oxide (NO*), when produced at low concentrations, may function as second messengers or regulators of signal transduction. The purpose of these studies was to determine whether corneal epithelial and stromal cells are capable of producing O2-* via an NADPH oxidase complex.

METHODS

Rabbit corneal epithelial and stromal cells, grown as primary cultures and low-passage isolates, were used as the sources of RNA for RT-PCR with primers specific for mRNAs encoding the proteins that comprise an NADPH oxidase complex. The RT-PCR products were sequenced to confirm their identities. The production of proteins composing the oxidase complex was confirmed, and the proteins were identified by Western blot analysis. The production of superoxide in cell-free preparations was assessed by measurement of NADPH-dependent superoxide dismutase (SOD)-inhibitable cytochrome c reduction and by electron paramagnetic resonance (EPR) with a superoxide specific spin trap.

RESULTS

Cell-free extracts of corneal epithelial and stromal cells produced superoxide in an NADPH-dependent manner, and this production was inhibited by SOD. EPR confirmed the identity of the reaction product as superoxide anion. Both rabbit corneal epithelial and stromal cells constitutively produced mRNAs encoding five proteins known to comprise a classic neutrophil-like NADPH oxidase complex. Production of NOX4, p22phox, p47phox, p67phox, and p40phox was confirmed by Western blot. Both epithelial and stromal cells expressed isoforms of Rac, a putative regulator of the activity of the complex.

CONCLUSIONS

A constitutively expressed NADPH oxidase complex that includes NOX4 is a source of O2-* produced by rabbit corneal epithelial and stromal cells. Superoxide produced by the oxidation of NADPH via the NADPH oxidase complex is a potential contributor to signal transduction pathways as well as a potential participant in processes that occur during inflammation.

Diffuse reflectance of short-fiber-reinforced composites aligned by an electric field

OBJECTIVES

This study aims to characterize the translucency of aligned, short-fiber composites by determining the effects of filler particle orientation on the Kubelka-Munk absorption and scattering coefficients.

METHODS

Rectangular composite specimens (n = 3) were filled with very short E-glass fibers. The fibers were oriented random, perpendicular, and parallel to the surface normal using an alternating electric field of 0.75 kV/mm. Diffuse reflectances of the composites on white and black backings were acquired with a spectrophotometer. The Kubelka-Munk model was then employed to calculate absorption and scattering coefficients.

RESULTS

The ordering of the reflectances on a white backing is neither the same nor the reverse of the reflectances on the black backing. The effects of orientation were different for the absorption and scattering coefficients. Orientation parallel to the average light flux notably decreases the amount of absorption, while perpendicular orientation appreciably increases the amount of scattering.

SIGNIFICANCE

Since orientation affects the absorption and scattering coefficients differently, the ordering of the reflectances may be different when the backing is varied. This is because the translucency is composed of two parameters (absorption and scattering) and cannot be adequately summarized with one parameter such as transmittance or reflectance. Therefore, the use of a diffuse reflectance model, such as Kubelka-Munk, is essential to a quantitative understanding of the translucency effects of filler orientation. Understanding how the filler orientation affects diffuse reflectance of composites will yield insight as to how the orientation of enamel rods affects the diffuse reflectance in teeth by analogy.

Fraunhofer diffraction of short-fiber-reinforced composites aligned by an electric field

OBJECTIVES

This study aims to determine if aligned, short-fiber composites are capable of producing Fraunhofer diffraction patterns similar to those of human enamel sections and to validate the mechanism of diffraction by comparing the experimental and theoretical fiber spacings.

METHODS

Rectangular composite specimens were filled with short E-glass fibers (120 microm length, 15 microm diameter) to contents of 1, 5, 10, and 25% (vol%). The fibers were oriented perpendicular to the surface normal using an alternating electric field of 0.75 kV/mm. A He-Ne laser was used with thin slices of specimen placed behind a pinhole to produce diffraction patterns. The locations of the diffraction maxima were used to determine the theoretical slit spacings which were compared to the experimental slit spacings determined by microscopy.

RESULTS

The specimens produced diffraction patterns analogous to the theoretical Fraunhofer diffraction of light through multiple slits. This was verified by comparing the theoretical spacing of the fibers calculated from the diffraction pattern with the experimental spacing of the fibers determined from the optical micrographs.

SIGNIFICANCE

This work has verified that orientation of short-fiber composites using an electric field can yield composites with sufficient order to produce Fraunhofer diffraction patterns that are qualitatively similar to the diffraction patterns of human enamel sections.

In vitro human enamel wear by a hydrated high-alkali porcelain

OBJECTIVE

The purpose of this study was to examine the hydration of a high-alkali dental porcelain (Ducera LFC) and its relative abrasive wear against human enamel. The hypothesis is that the composition of the porcelain (LFC) will form a softer, hydrated layer in artificial saliva, which will reduce wear against enamel relative to other dental porcelains.

METHOD AND MATERIALS

The first experiment was to estimate the thickness of the hydrated layer formed on LFC by storage in artificial saliva using microindentation hardness. The second experiment involved an estimate of enamel wear relative to other porcelains (d-Sign, LFC, Ducera Gold, and the control substance, Ceramco II) of hydrated LFC using a pin-on-disk wear test.

RESULTS

The mean microindentation hardness values of hydrated and unhydrated LFC and the Ceramco II control were 5750 Mpa, 8230 Mpa, and 7180 MPa, respectively, at a stylus depth of 400 nm. The average enamel wear values measured with the porcelains are (in microns): LFC saliva (hydrated), 23.8; d-Sign, 35.6; LFC, 59.4; Ducera Gold (hydrated), 75; Ducera Gold, 81.3; Ceramco II, 109.4. Using Tukey's analysis at a 5% error level, there were significant differences between the wear of enamel against hydrated LFC and the more abrasive Ceramco II control.

CONCLUSION

Comparing the effect of hydration of LFC on enamel wear, using an independent t test, hydrated LFC was significantly less abrasive than LFC (P< .008), but was not significantly less abrasive than d-Sign.

The effect of cesium-containing leucite additions on the thermal and mechanical properties of two leucite-based porcelains

It has been demonstrated that a Cs(2)O-stabilized leucite porcelain was susceptible to a stress-induced phase transformation, but toughening was not observed.1 It was hypothesized that if Cs(2)O-stabilized leucite core particles were added to a cesium-free matrix porcelain, selected or designed to enhance the toughening mechanism, toughening would occur. A commercial porcelain (VP) and a synthesized leucite-based porcelain (NP) were the matrix materials. Core particles of Cs(2)O (0.0-2.0 mol%) containing synthetic leucite were mixed with the two cesium-free matrix porcelains and vacuum fired into specimens for testing. The toughness of both types of matrix-based materials was dependent upon cesium content of the added core particles with a maximum toughness reached for those containing 0.75 mol% Cs(2)O. The toughness of the 0.75 mol% specimens (1.42 MNm(-3/2) for VP based and 2.15 MNm(-3/2) for NP based) was statistically (p <.02) higher than either of the matrix materials alone or the matrix materials containing added core particles of synthetic cesium-free leucite. However, the toughest materials (0.75 mol% Cs(2)O) were not the strongest materials, most likely because of large internal flaws. The results suggested that transformation toughening was possible.

Color measurements as quality criteria for clinical shade matching of porcelain crowns

STATEMENT OF PROBLEM

The ability of a dentist to select and communicate an acceptable shade match to a dental laboratory may be the most important factor in esthetic restorative dentistry.

PURPOSE

The purpose of this study was to evaluate the use of instrumental color measurement in clinical shade matching of porcelain-fused-to-metal (PFM) and all-porcelain crowns. The relative effects of clinical and laboratory factors related to shade matching for PFM and all-porcelain crowns were also evaluated.

MATERIALS AND METHOD

Forty patients treatment planned to receive PFM or all-porcelain crowns made up the study population. The patients were randomly divided into two groups for shade selection: conventional visual assessment and photocolorimetric analysis. At the preparation appointment, a photograph was taken of the target tooth along with four shade guide tabs selected by the two visual observers. The crown was fabricated by either visual selection or by the lowest E* values determined from the photographs and a spectrophotometer. The same dental laboratory fabricated all 40 restorations. At the cementation appointment, clinical criteria were used to evaluate anatomy/contour, surface texture, and the amount of glaze as it relates to color perception before the restoration was cemented.

RESULTS

The mean E* between the reference tooth before preparation and the crown before cementation in the visual assessment group was 10.49 (+/- 14.6), whereas the mean E* in the photocolorimetric group was 8.99 (+/- 5.7). Analysis of data showed that the observers and the colorimetric technique were perfect (E* = 0) 41% of the time and varied (E* = 0.1 or higher) 59% of the time. Data collected further showed no significant difference or correlation between shade selection methods and the evaluated clinical criteria.

CONCLUSIONS

These results provide evidence that there is no significant difference in shade selection using the conventional visual assessment by two experienced clinicians or the photocolorimetric technique.

CLINICAL SIGNIFICANCE

The use of photocolorimetric analysis in shade selection can serve as a reliable alternative to conventional visual shade selection. This method is useful for clinicians who have difficulty with shade selection.

Sufficiency of the reactive site loop of maspin for induction of cell-matrix adhesion and inhibition of cell invasion. Conversion of ovalbumin to a maspin-like molecule

Maspin, an ov-serpin, inhibits tumor invasion and induces cell adhesion to extracellular matrix molecules. Here, we use maspin/ovalbumin chimeric proteins and the maspin reactive site loop (RSL) peptide to characterize the role of the RSL in maspin-mediated functions. Replacement of the RSL plus the C-terminal region or the RSL alone of maspin with that of ovalbumin resulted in the loss of the stimulatory effect on adhesion of corneal stromal cells to type I collagen, fibronectin, and laminin and of mammary carcinoma MDA-MB-231 cells to fibronectin. Maspin with ovalbumin as the C-terminal region retained activity, suggesting the maspin C-terminal polypeptide is not required. An R340Q mutant retained full maspin activity; however, an R340A mutant lost activity. This indicates the arginine side chain at the putative P1 site forms a hydrogen bond and not an ionic bond. The RSL peptide (P10-P5', amino acids 330-345) alone induced cell-matrix adhesion of mammary carcinoma cells and corneal stromal cells and inhibited invasion of the carcinoma cells. Substitution of the RSL of ovalbumin with that of maspin converted inactive ovalbumin into a fully active molecule. Maspin bound specifically to the surface of the mammary carcinoma cells with a kd of 367 +/- 67 nM and 32.0 +/- 2.2 x 10(6) binding sites/cell. The maspin RSL peptide inhibited binding, suggesting the RSL is involved in maspin binding to cells. Sufficiency of the maspin RSL for activity suggests the mechanism by which maspin regulates cell-matrix adhesion and tumor cell invasion does not involve the serpin mechanism of protease inhibition.

Adsorption of catechol and comparative solutes on hydroxyapatite

Contemporary medical and dental adhesives often have difficulty sticking to wet surfaces or weaken with long-term exposure to water. Substantial research has been dedicated to finding a means of achieving adhesion in an aqueous environment. A study evaluates the adsorption of catechol relative to other chemical groups as means of gauging how effective they may be as adsorptive groups in adhesives. Contact angle and surface-tension measurements of solutions of catechols and other chemical groups were used to determine their works of adhesion. Adsorption isotherms were also constructed to ascertain Langmuir constants. Solutes containing catechol groups were compared to solutes containing other polar groups to see how well catechol adsorbs to hydroxyapatite, the mineral component of bones and teeth, relative to other chemical groups found in adhesives. The results of this study show that catechol and molecules containing catechol groups have higher rates and energies of adsorption to hydroxyapatite than do groups such as alcohols, amines, and carboxylic acids.

Maspin: synthesis by human cornea and regulation of in vitro stromal cell adhesion to extracellular matrix

PURPOSE

Maspin, a tumor-suppressor protein that regulates cell migration, invasion, and adhesion, is synthesized by many normal epithelial cells, but downregulated in invasive epithelial tumor cells. The purpose of this study was to determine whether cells in the normal human cornea express maspin and whether maspin affects corneal stromal cell adhesion to extracellular matrix molecules.

METHODS

Maspin expression was analyzed by immunodot blot, Western blot, and RT-PCR analyses in cells obtained directly from human corneas in situ. Maspin protein and mRNA were also studied in primary and passaged cultures of corneal stromal cells using Western blot analysis, RT-PCR, and immunofluorescence microscopy. Maspin cDNA was cloned and sequenced from human corneal epithelial cells and expressed in a yeast system. The recombinant maspin was used to study attachment of cultured human corneal stromal cells to extracellular matrices.

RESULTS

Maspin mRNA and micromolar amounts of the protein were found in all three layers of the human cornea in situ, including the stroma. Maspin was also detected in primary and first-passage corneal stromal cells, but its expression was downregulated in subsequent passages. Late-passage stromal cells, which did not produce maspin, responded to exogenous recombinant maspin as measured by increased cell adhesion not only to fibronectin, similar to mammary gland tumor epithelial cells, but also to type I collagen, type IV collagen, and laminin.

CONCLUSIONS

The corneal stromal cell is the first nonepithelial cell type shown to synthesize maspin. Loss of maspin expression in late-passage corneal stromal cells in culture and their biological response to exogenous maspin suggests a role for maspin on the stromal cells in the cornea. Maspin may function within the cornea to regulate cell adhesion to extracellular matrix molecules and perhaps to regulate the migration of activated fibroblasts during corneal stromal wound healing.

Mechanical properties of glass-only porcelains prepared by the use of two feldspathic frits with different thermal properties

Low- and non-leucite-containing commercial porcelains with low firing temperatures have become popular. However, improving the strength of glass porcelains is difficult. The purpose of this study was to determine if dispersed glass particles could be used as a reinforcing agent for an all-glass porcelain. We produced 3 feldspathic glasses (high-fusing, medium-fusing, low-fusing) by melting powders consisting of potassium-feldspar and 0, 5, or 20 mass% Na2O, respectively. For high-fusing, medium-fusing, and low-fusing feldspathic glasses, the deformation temperatures were 945 degrees C, 647 degrees C, and 518 degrees C, and the thermal expansion coefficient values were 8.6 x 10(-6)/degrees C, 10.3 x 10(-6)/degrees C, and 13.4 x 10(-6)/degrees C between 25 degrees C and the glass-transition temperature, respectively. The high-fusing-glass (or medium-fusing-glass) powders were mixed with low-fusing-glass powders before being fired into test specimens. The mean flexural strength and fracture toughness (K1C) of 3 single-glass porcelains ranged from 57 to 63 MPa and from 0.68 to 0.73 MPa m(1/2), respectively, presenting no significant differences in one-way ANOVA. However, the flexural strength of 50% high-fusing-glass + 50% low-fusing-glass porcelain was 114 MPa (p < 0.05) and K1C was 1.2 MPa m(1/2) (p < 0.05). Microcracks were observed with a back-scattered scanning electron microscope and were associated with the high- (or medium-) fusing glass particles, suggesting residual stress in the low-fusing-glass matrix due to a coefficient of thermal expansion mismatch between the dispersed glass particles and the matrix glass. The dispersing glass particles appeared to act as a reinforcing agent for strengthening a glassy porcelain.

Regulation of nitric oxide synthase 2 in rabbit corneal cells

PURPOSE

The purpose of these studies was to investigate the role of interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), interleukin 1beta (IL-1beta), and transforming growth factor-beta (TGF-beta) in the regulation of inducible nitric oxide synthase (NOS2) activity in rabbit corneal cells.

METHODS

Rabbit corneal epithelial, stromal, and endothelial cells were grown in culture and treated with cytokines and growth factors, alone or in combination. NOS activity was measured at times up to 72 hours after treatment by assaying the culture medium for nitrite using the Griess reaction. Cell lysates were analyzed by Western blot analysis for NOS2 protein. RNA was isolated and amplified with NOS1-, NOS2-, and NOS3-specific primers by RT-PCR.

RESULTS

NOS2 expression was induced by combined cytokine treatment from nondetectable levels to abundant levels in low passage (<4) stromal cells and to low levels in corneal endothelial cells but not in corneal epithelial cells. In the absence of IFN-gamma, little or no nitrite accumulation was induced by TNF-alpha, IL-1beta, or lipopolysaccharide (LPS) treatment. The inductive effects of IFN-gamma were antagonized in a dose-dependent manner by the myxoma virus rabbit IFN-gamma receptor homolog, M-T7. rRaIFN-gamma, in combination with IL-1beta and TNF-alpha, induced the appearance of NOS2 mRNA within 24 hours but detectable nitrite did not accumulate in large amounts (>10 microM) until after 24 hours postinduction. NOS2 was identified as a 130 kDa protein on Western blot analysis using monoclonal antibody against murine NOS2. TGF-beta(1) and beta(2) inhibited the accumulation of cytokine-induced nitrite in a dose-dependent manner while not significantly reducing the steady state level of NOS2 mRNA. The activity of the induced NOS was inhibited by 1400W, a NOS2-selective inhibitor, but not 7-nitroindazole, a NOS1-selective inhibitor.

CONCLUSIONS

In cultured corneal stromal cells, NOS2 expression was upregulated by IFN-gamma in combination with IL-1beta and TNF-alpha but not by any of these cytokines alone, while TGF-beta downregulated the activity. Cultures of corneal epithelial cells could not be induced to express NOS2, yet cultures of endothelial cells produced low amounts of NO in response to cytokines. The NOS1 and NOS3 isoforms were not detected in any of these corneal cells.

Interferon coordinately inhibits the disruption of PML-positive ND10 and immediate-early gene expression by herpes simplex virus

Interferons (IFNs) are important components of the innate immune response, limiting herpes simplex virus (HSV) infection. In recombinant HSV-infected cells, IFN inhibited expression of beta-galactosidase from the immediate-early gene, ICP4, promoter. The extent of inhibition was dependent on IFN dose, IFN type, cell type, and multiplicity of infection (moi). IFN inhibited gene transcription, leading to a complete block in ICP4 promoter-driven gene expression in 90% of cells. The same IFN treatments resulted in an increase in the size and number of nuclear domain 10 (ND10) structures that stained positive by immunofluorescence for the promyelocytic leukemia (PML) protein. In cultures infected at low moi with a recombinant HSV producing ICP4 as a fusion protein with green fluorescence protein, the appearance of green fluorescence in the nucleus coincided with loss of PML-positive ND10 in the same nucleus, even in the rare ICP4-expressing IFN-treated cells. IFN-dependent inhibition was nearly complete when the immediate-early promoter was in the viral genome but was minimal when the promoter was stably integrated into the cellular genome. These data reveal that IFN can completely block viral gene expression in infected cells and that enhancement of the ND10 structure, which is the site of initiation of HSV replication, correlates with the block in viral gene expression.

Strengthening mechanisms of current dental porcelains

Dental porcelains have a high glass content, which provides the translucency necessary for esthetic restorations. Because glasses are brittle, they fail under tension or bending by the propagation of preexisting flaws (e.g., scratches, porosities). Several approaches that are based on impeding the propagation of flaws have been used to strengthen dental porcelains, including bonding to metals, adding microcrystalline phases, and surface treatments (i.e., polishing, ion exchange, hydration). Through these methods, porcelain systems are used routinely for all-ceramic anterior restorations; however, porcelain-fused-to-metal restorations remain the most reliable for posterior applications.

Investigation of two mercury vapor collection techniques

OBJECTIVES

The purpose of this investigation was to develop and test two in vitro mercury vapor collection techniques: a closed bottle technique (CB) and an intraoral flow (IOF) technique.

METHODS

Amalgam samples were prepared in acrylic first molars (#30) with standardized Class I preparations. In the CB technique, samples were placed in either a 25, 100 or 500 ml bottle (n = 5). Vapor was analyzed with the Jerome M-411 using a syringe method over a 7 day period. In the IOF technique an impression of the lower right quadrant of a Typodont was taken with PVS impression material leaving a 5 mm space over #30. Samples were analyzed with the Jerome M-411 connected to the impression tray via tygon tubing at the buccal surface. Average mercury vapor release rates and standard deviations were calculated for each method. Data were analyzed by two-way ANOVA followed by Tukey HSD pairwise analysis for significant findings (alpha = 0.05).

RESULTS

Both techniques indicated mercury vapor release was dependent on volume. The largest bottle, 500 ml, yielded a significantly greater (p < or = 0.00) amount of mercury vapor within the CB systems. In the IOF technique, the addition of air flow over the restoration demonstrated a significant increase (p < or = 0.05) in mercury vapor released compared to the sealed IOF technique.

SIGNIFICANCE

A method for mercury vapor analysis was developed for possible intraoral application. The IOF method with direct air flow removes possible saturation effects found in a CB system, while limiting external variables, which may contribute to errors associated with in vivo measurements.

Effects of palladium addition on emission of mercury vapor from dental amalgam

OBJECTIVES

The purpose of this investigation was to test the hypothesis that palladium causes a reduction in mercury emission when added to dental amalgam during condensation.

METHODS

Mercury vapor release was measured in a closed bottle system and an Intraoral Flow device(IOF). Conventional amalgam restorations were modified by addition of various palladium pellets. 1.57 mm diameter palladium pellets with different porosities were fabricated. These pellets were then placed in amalgam restoration using typical condensation and carving procedures. The samples were stored in a closed bottle and mercury measurements were taken from the bottles at 30 min, 1, 3, 5, 24 and 48 h and 7 days after trituration using a Jerome 411 Mercury Vapor Analyzer (Arizona Instrument Corp., Jerome, AZ). The palladium pellets identified as the most effective in mercury vapor reduction were further tested in an IOF device. Data were analyzed by two-way ANOVA followed by Tukey HSD pairwise analysis for significant findings (alpha = 0.05).

RESULTS

The palladium containing amalgams when tested in the closed bottle system yielded significantly lower (p < 0.05) mercury vapor release than the controls. Pellets fabricated with the highest porosity yielded the greatest reduction in overall mercury vapor release. In the IOF device the overall amount of mercury vapor released from the palladium containing amalgams was also significantly less than the control (p < 0.05).

SIGNIFICANCE

Mercury vapor emission from dental amalgam was greatly reduced by adding palladium pellets to amalgam during condensation. These techniques require only slight modifications of the standard operative procedures.