Revisit the causal inference between organizational commitment and job satisfaction: A meta-analysis disentangling its sources of inconsistencies

Existing theories and studies have exclusively focused on the direct temporal ordering of organizational commitment (OC) and job satisfaction (JS). However, their ordering varies highly across empirical studies. It is unclear whether such high variation is caused by statistical artifacts (i.e., spurious variation) or substantive moderators (i.e., true variation). Therefore, to disentangle artificial and substantial sources of this variation, we adopted traditional and full information meta-analytic structural equation modeling based on 71 independent samples (N = 16,698) with panel designs. After correcting for statistical artifacts, there was moderate heterogeneity in the lagged effects of OC and JS, suggesting that their ordering was not direct or simple but moderated by other variables. Further, the conceptualizations and/or measurements of OC and JS, time lag, and the timing of the investigation (e.g., newcomers vs. nonnewcomers) moderated their ordering. Finally, different specifications of the ordering between OC and JS resulted in differential cross-lagged relationships among JS, OC, and turnover intentions (k = 31, N = 6,876). Our meta-analysis provides new insights into the conceptualizations and/or measurements of OC and JS, adds some theoretical clarification to the dissenting theories by incorporating the time element, nuanced differences in the OC conceptualizations and the timing of the investigation, and raises concern over theory and research informed by studies overlooking alternative orderings of JS and OC. Looking forward, we suggest several promising future directions for explaining the heterogeneous cross-lagged relationships between OC and JS. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Integrating a pressure sensor with an OCT handheld probe to facilitate imaging of microvascular information in skin tissue beds

Optical coherence tomography (OCT) and OCT angiography (OCTA) have been increasingly applied in skin imaging applications in dermatology, where the imaging is often performed with the OCT probe in contact with the skin surface. However, this contact mode imaging can introduce uncontrollable mechanical stress applied to the skin, inevitably complicating the interpretation of OCT/OCTA imaging results. There remains a need for a strategy for assessing local pressure applied on the skin during imaging acquisition. This study reports a handheld scanning probe integrated with built-in pressure sensors, allowing the operator to control the mechanical stress applied to the skin in real-time. With real time feedback information, the operator can easily determine whether the pressure applied to the skin would affect the imaging quality so as to obtain repeatable and reliable OCTA images for a more accurate investigation of skin conditions. Using this probe, imaging of palm skin was used in this study to demonstrate how the OCTA imaging would have been affected by different mechanical pressures ranging from 0 to 69 kPa. The results showed that OCTA imaging is relatively stable when the pressure is less than 11 kPa, and within this range, the change of vascular area density calculated from the OCTA imaging is below 0.13%. In addition, the probe was used to augment the OCT monitoring of blood flow changes during a reactive hyperemia experiment, in which the operator could properly control the amount of pressure applied to the skin surface and achieve full release after compression stimulation.

Local axis orientation mapped by polarization sensitive optical coherence tomography provides a unique contrast to identify caries lesions in enamel

Due to rod-like hydroxyapatite crystal organizations, dental enamel is optically anisotropic, i.e., birefringent. Healthy enamel is known to be intrinsically negatively birefringent. However, when demineralization of enamel occurs, a considerable number of inter-crystallite spaces would be created between the crystallites in the enamel, which could lead to a sign reversion in birefringence of the enamel structure. We propose that this sign reversion can be leveraged in polarization sensitive OCT (PSOCT) imaging to differentiate early caries lesions from healthy enamel. In this study using PSOCT, we first confirm that the change in birefringence sign (negative to positive) can lead to a 90-degree alteration in the local axis orientation because of the switch between the fast and slow optic axes. We then demonstrate, for the first time, that the local axis orientation can be utilized to map and visualize the WSLs from the healthy enamel with a unique contrast. Moreover, the sharp alteration in local axis orientation gives a clear boundary between the WSLs and the healthy enamel, providing an opportunity to automatically segment the three-dimensional WSLs from the healthy enamel, enabling the characterization of their size and depth information in an intuitive way, which may aid clinical decision making and treatment planning.

Intraoral optical coherence tomography and angiography combined with autofluorescence for dental assessment

There remains a clinical need for an accurate and non-invasive imaging tool for intraoral evaluation of dental conditions. Optical coherence tomography (OCT) is a potential candidate to meet this need, but the design of current OCT systems limits their utility in the intraoral examinations. The inclusion of light-induced autofluorescence (LIAF) can expedite the image collection process and provides a large field of view for viewing the condition of oral tissues. This study describes a novel LIAF-OCT system equipped with a handheld probe designed for intraoral examination of microstructural (via OCT) and microvascular information (via OCT angiography, OCTA). The handheld probe is optimized for use in clinical studies, maintaining the ability to detect and image changes in the condition of oral tissue (e.g., hard tissue damage, presence of dental restorations, plaque, and tooth stains). The real-time LIAF provides guidance for OCT imaging to achieve a field of view of approximately 6.9 mm × 7.8 mm, and a penetration depth of 1.5 mm to 3 mm depending on the scattering property of the target oral tissue. We demonstrate that the proposed system is successful in capturing reliable depth-resolved images from occlusal and palatal surfaces and offers added design features that can enhance its usability in clinical settings.

Gingivitis resolution followed by optical coherence tomography and fluorescence imaging: A case study

Gingivitis is highly prevalent in adults, and if left untreated, can progress to periodontitis. In this article, we present an interesting case study where the resolution of gingivitis was followed over a period of 10 days using optical coherence tomography (OCT) and light-induced autofluorescence (LIAF). We demonstrate that OCT and its functional angiography can distinctively capture the changes during the resolution of gingivitis; while LIAF can detect red-fluorescent signals associated with mature plaque present at the inflamed site. The acute inflammatory region showed evidence of angiogenesis based on the quantification of vessel density and number; while no angiogenesis was detected within the less inflamed region. Gingival thickness showed a reduction of 140 ± 26 μm on average, measured between the peak gingivitis event and the period wherein the inflammation was resolved. Vessels in the angiogenesis site was found to reduce exponentially. The mildly inflamed site showed a decreasing trend in the vessel size, which however was within the error of the measurement.

Polarization sensitive optical coherence tomography with single input for imaging depth-resolved collagen organizations

Collagen organization plays an important role in maintaining structural integrity and determining tissue function. Polarization-sensitive optical coherence tomography (PSOCT) is a promising noninvasive three-dimensional imaging tool for mapping collagen organization in vivo. While PSOCT systems with multiple polarization inputs have demonstrated the ability to visualize depth-resolved collagen organization, systems, which use a single input polarization state have not yet demonstrated sufficient reconstruction quality. Herein we describe a PSOCT based polarization state transmission model that reveals the depth-dependent polarization state evolution of light backscattered within a birefringent sample. Based on this model, we propose a polarization state tracing method that relies on a discrete differential geometric analysis of the evolution of the polarization state in depth along the Poincare sphere for depth-resolved birefringent imaging using only one single input polarization state. We demonstrate the ability of this method to visualize depth-resolved myocardial architecture in both healthy and infarcted rodent hearts (ex vivo) and collagen structures responsible for skin tension lines at various anatomical locations on the face of a healthy human volunteer (in vivo).

Trial leadership by women is associated with racial diversity among heart failure clinical trial participants: a systematic bibliometric review 2000–2020

Background

For the results of randomized controlled trials (RCTs) to be generalizable, they should report on and include the broad range of patients who have the disease.

Purpose

We assessed temporal trends and trial factors associated with 1) the reporting of race or ethnicity data and 2) the enrolment of Black, Indigenous, and people of colour (BIPOC) in Heart Failure (HF) RCTs.

Methods

We searched MEDLINE, EMBASE, and CINAHL for RCTs that recruited adults with HF and were published in journals with an impact factor ≥10 between January 1, 2000 and June 17, 2020. We extracted data in duplicate and used the Cochran-Armitage and Jonchkeere-Terpstra tests to examine temporal trends. We used multivariable regression to assess the independent association between trial factors and the outcomes of interest.

Results

A total of 414 RCTs met inclusion criteria, of which a vast majority (90.6%; 95% CI 87.4–93.2%) were coordinated in either Europe or North America. Only 157 of the 414 RCTs (37.9%; 95% CI 33.2–42.8%) reported race/ethnicity data; among the 158,200 participants in these trials, only 29,512 (18.7%; 95% CI 18.5–18.9%) were BIPOC. There was a significant increase in the reporting of race or ethnicity data (from 26.9% in 2000–2001 to 54.2% in 2019–2020, p<0.001) and in enrollment of BIPOC (from 16.5% in 2000–2001 to 23.9% in 2019–2020, p=0.038) between 2000–2020. Trial leadership by a woman was associated with twice the adjusted odds of reporting of race or ethnicity data (OR 2.0; 95% CI 1.1–3.8; p=0.028) and an 8.4% (95% CI 1.9–15.0%; p=0.012) adjusted increase in enrollment of BIPOC. The race/ethnicity of trial leaders was not available for analysis.

Conclusions

Among HF RCTs published between 2000–2020, <38% reported data on race or ethnicity, although this increased over time. Among trials reporting such data, <19% of participants were BIPOC, with modest increases in enrollment over time. Trials led by women had greater adjusted odds of reporting race/ethnicity data and enrollment of BIPOC.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): CIHR

Temporal trends in the inclusion of patient-reported outcomes in heart failure randomized trials published in high-impact medical journals: a systematic bibliometric review

Background

Patient reported outcomes (PROs) are important measures of health, particularly in symptomatic conditions such as heart failure (HF), and regulatory agencies have encouraged their collection in randomized controlled trials (RCTs).

Purpose

To assess temporal trends in the inclusion of patient-reported outcomes (PROs) in heart failure (HF) randomized controlled trials (RCTs) published in high-impact medical journals, explore trial characteristics associated with inclusion of PROs, and describe the quality of PRO reporting in HF RCTs.

Methods

We searched MEDLINE, EMBASE and CINAHL for studies published between January 1, 2000 and July 17, 2020. We included RCTs published in journals with impact factor ≥10. We assessed temporal trends using the Jonckheere-Terpstra test and conducted multivariable logistic regression analysis to explore trial characteristics independently associated with inclusion of PROs. We assessed the quality of PRO reporting using the Consolidated Standards for Trial Reporting PRO extension statement.

Results

We identified 12,342 articles, of which 417 RCTs met inclusion criteria. PROs were included in 224 RCTs (53.7%, 95% confidence interval [CI]: 48.8%-58.6%), of which 44 (19.6%) reported PRO as primary or co-primary endpoint. The proportion of RCTs with PROs increased significantly between 2000–2003 (37.4%) and 2016–2020 (65.1%) (p<0.001). PROs had higher odds of inclusion in RCTs that were multicenter (odds ratio [OR]: 1.95; 95% CI: 1.05–3.64; p=0.036); medium-sized (n=51–250) (OR: 2.29; 95% CI: 1.24–4.23; p=0.008); coordinated in in Central and South America (OR: 6.79; 95% CI: 1.34–34.36; p=0.021); and assessed health services (OR: 4.21; 1.97–8.98; p<0.001), device / surgical (OR: 6.24; 95% CI 3.05–12.80; p<0.001), or exercise and rehabilitation interventions (OR: 3.98; 95% CI 1.59–9.97; p=0.003). A majority (54.9%) of the 224 RCTs reported four or less of the eleven CONSORT-PRO items. The median number of CONSORT-PRO items reported was 4 (interquartile range [IQR] 3–6 items per trial), with improved reporting in trials with PRO as primary or co-primary endpoint.

Conclusions

PROs are included in in just over half of HF RCTs, with an increased reporting of PROs between 2000 and 2020. Large, pharmacotherapy trials conducted in North America and Europe were less likely to include PROs. The quality of PRO reporting in HF RCTs was modest, with trials most often reporting four of eleven CONSORT-PRO items.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Canadian Institutes of Health Research

Global representation of heart failure clinical trial leaders and collaborators: a systematic bibliometric review 2000–2020

Aims

Heart Failure (HF) has a disproportionate burden in low- and middle-income countries. The geographic representation of those who lead HF randomized clinical trials (RCTs) may not reflect the geographic burden of disease. We assessed temporal trends and trial characteristics associated with leadership outside Europe and North America, and explored whether there was a geographic association between trial leadership and participant enrolment.

Methods and results

We searched MEDLINE, EMBASE, and CINAHL for HF RCTs published in journals with an impact factor ≥10 between January 1, 2000, and June 17, 2020. We used the Jonckheere-Terpstra test to assess temporal trends and multivariable logistic regression models to determine associations between predictor and outcome variables.

There were 414 eligible RCTs. Only 80 of 828 trial leaders (9.7%; 95% CI: 7.8% to 11.8%), and 453 of 4656 collaborators (9.7%; 95% CI: 8.8% to 10.6%) were from regions outside Europe and North America, with no temporal change in geographic representation. The odds of trial leadership outside Europe and North America were significantly lower with industry versus public funding (OR: 0.33; 95% CI: 0.15 to 0.75; P=0.008). Trial leadership outside Europe and North America was associated with enrolment of patients outside Europe and North America (OR: 10.0; 95% CI 5.6–19.0; P<0.001).

Conclusion

Trial leadership outside Europe and North America is rare, particularly in industry funded trials, and is associated with participant enrolment in regions with disproportionate disease burden. Building research capacity and networks in under-represented regions could increase generalizability of trial results.

Funding Acknowledgement

Type of funding sources: None.

Noninvasive multimodal imaging by integrating optical coherence tomography with autofluorescence imaging for dental applications

We report the development of an integrated multifunctional imaging system capable of providing anatomical (optical coherence tomography, OCT), functional (OCT angiography, OCTA) and molecular imaging (light-induced autofluorescence, LIAF) for in vivo dental applications. Blue excitation light (405 nm) was used for LIAF imaging, while the OCT was powered by a 1310 nm swept laser source. A red-green-blue digital camera, with a 450 nm cut-on broadband optical filter, was used for LIAF detection. The exciting light source and camera were integrated directly with the OCT scanning probe. The integrated system used two noninvasive imaging modalities to improve the speed of in vivo OCT data collection and to better target the regions of interest. The newly designed system maintained the ability to detect differences between healthy and hypomineralized teeth, identify dental biofilm and visualize the microvasculature of gingival tissue. The development of the integrated OCT-LIAF system provides an opportunity to conduct clinical studies more efficiently, examining changes in oral conditions over time.

FRI0423 CLINICAL BURDEN OF TREATING COMMERCIALLY-INSURED OSTEOARTHRITIS PATIENTS WITH PRESCRIPTION NSAIDS

Background:

Prescription NSAIDs/Cox-2s (“NSAIDs”) are commonly prescribed by physicians to treat patients with chronic pain, and much is known about the potential negative outcomes associated with their use1. Such negative outcomes include gastrointestinal (“GI”) issues and hepatorenal toxicity.1In addition, CV risk of Cox-2s has not been completely clarified.1,2However, less is known about the extent to which these outcomes are pervasive and problematic in specific patient populations such as those diagnosed with osteoarthritis (“OA”).

Objectives:

The goal of this research is to assess the clinical burden of commercially-insured patients diagnosed with OA of the hip and/or knee before and after treatment with prescription NSAIDs, in a large, national database in recent years.

Methods:

The Optum Healthcare Solutions, Inc. data (1/2012-3/2017) were used to identify patients ≥18 years old with ≥2 diagnoses of hip and/or knee OA, and ≥90 days supply of NSAIDs during the three-year period from first prescription (index date) after their first OA diagnosis. Patients were required to be continuously-enrolled during the six months before (baseline period) and 36 months after (follow-up period) the index date. Selected clinical outcomes such as GI issues, CV events, and renal toxicity were compared between the baseline and follow-up periods. Costs and resource use were normalized to account for differential duration in analytic time periods.

Results:

Data for 22,435 patients (60.8% as female, with an average age of 62) with hip and/or knee OA were analyzed. On average, patients were prescribed NSAIDs for 489 days during the follow-up period. From the baseline period to follow-up period, negative clinical outcomes associated with GI issues increased by 393% (1.5% v 7.5%), driven by a 667% (0.3% v 2.3%) increase in acute GI hemorrhages. Additionally, negative clinical outcomes associated with CV events increased by 73% (40.7% v 70.6%), largely due to a 600% (0.3% v 2.1%) increase in acute myocardial infarction. Lastly, negative clinical outcomes associated with renal toxicity increased by 433% (1.5% v 8.0%), with a 740% (0.5% v 4.2%) increase in acute renal failure being the most substantial.

Conclusion:

These findings suggest that prescribing of NSAIDs among OA patients is associated with an increase in negative clinical outcomes. This suggests that new treatment options other than NSAIDs should be evaluated.

References:

[1]van Laar M, et al. Pain treatment in arthritis-related pain: beyond NSAIDs.Open Rheumatol J. 2012;6:320–330.

[2]Nissen SE, et al. Cardiovascular safety of celecoxib, naproxen, or ibuprofen for arthritis.NEJM2016;2519-2529.

Disclosure of Interests:

Stuart Silverman Consultant of: Pfizer and Eli Lilly for this project., Speakers bureau: Amgen, Radius, James Rice Consultant of: Pfizer and Eli Lilly have funded this project., Alan White Consultant of: Pfizer and Eli Lilly have funded this project., Nguyen Le Consultant of: Pfizer and Eli Lilly have funded this project., Michael Somma Consultant of: Eli Lilly and Pfizer have funded this project., Craig Beck Shareholder of: Pfizer, Employee of: Pfizer, Rebecca Robinson Shareholder of: Eli Lilly, Employee of: Eli Lilly, Patricia Schepman Shareholder of: Pfizer, Employee of: Pfizer

Time Trend of Liver Cancer Among Subpopulation of Ages Less Than 40 During 2005-2014 in Nghe An, Viet Nam

Background: Liver cancer has been leading cancer mortality nationwide in Viet Nam. Aim: The aim was to examine time trends of liver cancer mortality by performing population-based mortality registration in Nghe An province, 2005-2014. Methods: We yearly collected data from all 480 Commune Health Stations from 2005 to 2014 using the designed form of “Mortality Registration” with a guideline of underlying-, immediate, - and contribute cause of death. Five variables were included name, age, sex, date of death and cause of death. Average residents of each commune were also yearly reported. All cases were coded ICD-10, then liver cancer (C22) was derived. Age-standardized rate (ASR) was estimated. Trend of liver cancer was observed by estimated mortality rates ratio and 95% confident interval (MRR) for 5-period of 2005-2006 (reference), 2007-2008, 2009-2010, 2011-2012, 2013-2014, adjusted for total mortality rate and proportion of cases with unknown causes of death, for total, subgroup of ages 40 or older, and ages less than 40. Results: Among registered 7,667 cases of liver cancer, there were 855 cases aged less than 40. Mortality rates per 100,000 (ASR) were increased from 37.4 to 52.8 in men and 9.2 to 12.6 in women, from 2005 to 2014, respectively. The increased trends were significantly seen for the subpopulation ages 40 or older only, MRR=1.56, 95% CI: 1.38-1.76 in men and MRR=1.67, 95% CI: 1.36-2.04 in women, all P trend < 0.05. In contrast, the decreased trends were significantly observed for the subpopulation ages less than 40, MRR=0.72, 95% CI: 0.54-0.97 in men and MRR=0.47, 95% CI: 0.22-0.99 in women, all P trend < 0.05. Conclusion: The significant decline risks of death from liver cancer for the subpopulation ages less than 40 during 2005-2014 might be explained by HBV vaccine nationwide from 1998 to date and reduction of environmental factors induced this cancer sites in improving healthy environments after the war ended in 1975. Key-words: Liver-cancer, population-based mortality registration, Viet Nam, HBV-vaccine.

Current Achievement and Challenges of Food, Cooking Methods and Cancer Control: A Pooled Multivariable-Adjusted Analysis for the Association Between Meat Mutagens Intake and Colorectal Adenoma and Cancer

Background: Heterocyclic amines (HCAs), a group of dietary carcinogens, have been hypothesized to increase risk of colorectal adenoma (CRA) cancer (CRC). However, previous findings have been inconsistences. Aim: The aim was to pool analysis of multivariable-adjusted relative risks from published articles for the association between HCAs intake and the risk of CRD and CRC. Methods: We used all available 34 published articles to access the multivariable-adjusted relative risk (hazard ratio or odds ratio) and their 95% confidence interval (95% CI) to estimate ln(RR) and se(ln(RR)). The HCAs 2-amino-3,8-dimethylimidazo[4,5,-f]quinoxaline (MeIQx), 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 2-amino-3,4,8-trimethylimidazo[4,5,-f]quinoxaline (DiMeIQx), and meat-derived mutagenicity (MDM) were examined. The random pooled RR, 95% CI was analyzed in using ln(RR) and se(ln(RR)) for separated prospective cohort studies and case-control studies by STATA-10. Results: Prospective cohort studies have examined for 5,684 CRC occurred among 528,111 registered participants; and for 2,484 CRA occurred among 136,902 registered participants. Case-control studies have examined for 12,753 CRC and 17,152 matched controls; and for 10,821 CRA and 45,099 matched controls. PhIP was majority contributed by cooked chicken (54%–74%). MeIQx was mainly contributed by red meat (83%–92%). For prospective cohort studies on CRC, fifth versus first-quintile, the random pooled RR, (95% CI) was 1.11, (1.00, 1.23), P = 0.052 for MDM; 1.00, (0.91, 1.09), P = 0.958 for PhIP; 1.12, (1.03, 1.22), P = 0.009 for MeIQx; 1.03, (0.87, 1.22), P = 0.763 for DiMeIQx. For CRA, third versus first-quintile, the random pooled RR, (95% CI) was 1.13, (0.92, 1.39), P = 0.237 for MDM; 1.11, (0.96, 1.29), P = 0.169 for PhIP; 1.14, (1.00, 1.30), P = 0.048 for MeIQx; 1.00, (0.87, 1.15), P = 0.999 for DiMeIQx. For case-control studies, the null association was observed for PhIP, DiMeIQx and CRC. A positive association was significantly seen for MeIQx, MDM and both CRC and CRA. Conclusion: Because intake of MeIQx significantly increased the risk of both CRC and CRA in both prospective cohort and case-control studies, the findings support to the hypothesis of the role of underlying mechanisms of red meat induced CRC.

High-intensity-focused ultrasound and phase-sensitive optical coherence tomography for high resolution surface acoustic wave elastography

Elastography has the ability of quantitatively evaluating the mechanical properties of soft tissue; thus it is helpful for diagnosis and treatment monitoring of many diseases, for example, skin diseases. Surface acoustic waves (SAWs) have been proven to be a non-invasive, non-destructive method for accurate characterization of tissue elastic properties. Current SAW elastography using high-energy laser pulse or mechanical shaker still have some problems. In order to improve SAW elastography in medical application, a new technique was proposed in this paper, which combines high-intensity-focused ultrasound as a SAWs impulse inducer and phase-sensitive optical coherence tomography as a SAWs detector. A 2% agar-agar phantom and ex-vivo porcine skin were tested. The data were processed by a new algorithm based on the Fourier analysis. The results show that the proposed method has the capability of quantifying the elastic properties of soft tissue-mimicking materials. The lateral resolution of the elastogram has been significantly improved and the different layers in heterogeneous material could also been distinguished. Our improved technique of SAW elastography has a large potential to be widely applied in clinical use for skin disease diagnosis and treatment monitoring.

Robust principal component analysis in optical micro-angiography

Background

Recent development of optical micro-angiography (OMAG) utilizes principal component analysis (PCA), where linear-regression filter is employed to separate static and blood flow signals within optical coherence tomography (OCT). While PCA is relatively simple and computationally efficient, the technique is sensitive to and easily skewed by outliers. In this paper, robust PCA (RPCA) is thus introduced to tackle this issue in traditional PCA.

Methods

We first provide brief theoretical background of PCA and RPCA in the context of OMAG where coherent (complex) OCT signals are utilized to contrast blood flow. We then compare PCA and RPCA on sets of 4D-OCT complex data (3 dimensions in space and 1 dimension in time), which are collected from microfluidic phantoms and in vivo nail-fold tissue.

Results

In phantom experiments, both analyses perform relatively well since there are little motion within our observation time window, albeit small tail-noise artifacts from PCA. In nail-fold experiment, PCA suffers from tissue motion, from which RPCA does not seem to be affected. Results from RPCA also show enhancements of other dynamic signals, which are likely from the intercellular fluid. This unwanted result is yet to be proven useful for clinical applications.

Conclusions

Traditional PCA method employs linear-regression filter and is sensitive to outliers (tail-noise and motion artifacts). RPCA method is robust against outliers, but is currently computationally expensive.

Methodology on quantification of sonication duration for safe application of MR guided focused ultrasound for liver tumour ablation

BACKGROUND AND OBJECTIVE

Magnetic Resonance Guided Focused Ultrasound (MRgFUS) for liver tumour ablation is a challenging task due to motion caused by breathing and occlusion due the ribcage between the transducer and the tumour. To overcome these challenges, a novel system for liver tumour ablation during free breathing has been designed.

METHODS

The novel TRANS-FUSIMO Treatment System (TTS, EUFP7) interacts with a Magnetic Resonance (MR) scanner and a focused ultrasound transducer to sonicate to a moving target in liver. To meet the requirements of ISO 13485; a quality management system for medical device design, the system needs to be tested for certain process parameters. The duration of sonication and, the delay after the sonication button is activated, are among the parameters that need to be quantified for efficient and safe ablation of tumour tissue. A novel methodology is developed to quantify these process parameters. A computerised scope is programmed in LabVIEW to collect data via hydrophone; where the coordinates of fiber-optic sensor assembly was fed into the TRANS-FUSIMO treatment software via Magnetic Resonance Imaging (MRI) to sonicate to the tip of the sensor, which is synchronised with the clock of the scope, embedded in a degassed water tank via sensor assembly holder. The sonications were executed for 50 W, 100 W, 150 W for 10 s to quantify the actual sonication duration and the delay after the emergency stop by two independent operators for thirty times. The deviation of the system from the predefined specs was calculated. Student's-T test was used to investigate the user dependency.

RESULTS

The duration of sonication and the delay after the sonication were quantified successfully with the developed method. TTS can sonicate with a maximum deviation of 0.16 s (Std 0.32) from the planned duration and with a delay of 14 ms (Std 0.14) for the emergency stop. Student's T tests indicate that the results do not depend on operators (p > .05).

CONCLUSION

The evidence obtained via this protocol is crucial for translation- of-research into the clinics for safe application of MRgFUS. The developed protocol could be used for system maintenance in compliance with quality systems in clinics for daily quality assurance routines.

A phase Ib study of the MEK inhibitor GSK1120212 combined with gemcitabine in patients with solid tumors: Interim results

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Background: GSK1120212 (212) is a reversible, allosteric inhibitor of MEK1/MEK2. The objectives of this open-label, single-arm study are to evaluate the safety, pharmacokinetics (PK), and anti-tumor activity of 212 + gemcitabine (gem), and to determine the recommended phase II regimen (RP2R) in patients (pts) with advanced solid tumors.

Methods: 212 (1-2.5mg) is given continuously, orally, once daily. Gem (1,000mg/m2) is infused on days 1, 8, and 15 every 28 days. Doses are escalated to the maximum tolerated dose (MTD) and followed by an expansion cohort to confirm the RP2R tolerability.

Results: 28 pts received ≥ 1 dose of 212 + gem, including 8 pancreatic, 6 breast, and 4 non-small cell lung (NSCLC) cancer pts. The MTD and RP2R is 2mg 212 + 1,000mg/m2 gem. Dose-limiting toxicities (DLTs) are G3/G4 febrile neutropenia (n=2), G3 AST elevation (n=2), and G2 uveitis (n=1). 16 serious adverse events (SAEs) were reported; 5 were considered to be related to study drugs (1 pneumonitis, 3 febrile neutropenia, 1 dyspnea). All DLTs and SAEs have resolved. The most common AEs at the RP2R (n=18) were rash (78%), fatigue (67%), thrombocytopenia (61%), neutropenia (50%), decreased appetite (50%), nausea (44%), diarrhea and constipation (39%); all ≤ G2 except thrombocytopenia (17% ≥ G3) and neutropenia (33% ≥ G3). Co-administration did not affect the PK profiles of 212 or gem. 25 pts had measurable disease at baseline. 1 pancreatic cancer pt with previous radiotherapy and 2 cycles of gem achieved a partial response and stayed on study for 6 months. 3 additional pancreatic cancer pts reported stable disease; 2 of which were on the study for 3.5-5 months and the third pt continues in the study. 1 triple-negative breast cancer pt, refractory to chemotherapy, and 1 parotid cancer pt experienced a complete response of their target lesions.

Conclusions: 212 + gem is tolerable with an acceptable safety profile in this pt population, with evidence of clinical activity in pancreatic cancer. A randomized phase II study in previously untreated patients with metastatic pancreatic cancer is underway to investigate the clinical activity of this combination.

[Table: see text]

Protective Effect of Estrogen (E2) and Increased Risk of E2 Plus Progestin (Prog) on Breast Cancer (BrCa). The 2009 Review of the Women's Health Initiative (WHI) Hormone Replacement Therapy (HRT) Published Trials

INTRODUCTION & METHODOLOGY.The objective of this review is to identify from the two WHI published randomized HRT trials the BrCa risk or benefit, with a special focus on different impact of E2-alone vs E2+Prog on human breast carcinogenesis (BrCa-genesis).In the 1st trial (JAMA 2002, 2007), healthy women age 50 - 79 were randomized to E2 plus Prog versus placebo (Plac). Reviewed were Hazard ratios (HRs) for all pts and also for those with or without prior Hormone use. Mean follow up was 5.2 years.In the 2nd trial (JAMA 2004, 2006), women with hysterectomy age 50 - 79 were randomized to E2 alone (without Prog) versus Plac. Mean follow up was 7.1 years. Reviewed were all pts, and also subsets with or without prior E2 or Prog; with or without prior history of Benign Breast Disease (PHBrD); and with or without prior history of a 1st degree relative with BrCa (PH1stRelBrCa).RESULTS.Invasive BrCa incidence:N (%)HR95% C.I.1st TrialAll participants:16,608 (100%)1.260.83 - 1.97No prior Hormone use:12,304 (74.1%)1.060.81 - 1.38Prior Hormone use &lt;5 yrs:3,005 (18.1%)2.131.15 - 3.94*Prior Hormone use 5 - 10 yrs:783 (4.7%)4.611.01 - 21.02*2nd TrialAll participants:10,739 (100%)0.800.62 - 1.04No prior hormone use:5,763 (53.7%)0.650.46 - 0.92*Prior E2 use:4,976 (46.3%)0.980.67 - 1.44Prior E2 + PROG use:468 (4.4%)2.350.60 - 9.14No PHBrD:7,681 (71.5%)0.570.41 - 0.78*No PH1stRelBrCa8,554 (80.0%)0.680.50 - 0.92*CONCLUSION:1. Results from the 1st trial show that concomitant use of E2 with Prog, particularly in women with prior Hormone use, is associated with increased BrCa hazards.2. The results of the 2nd HRT trial indicate that use of HRT with E2 alone is associated with a reduction in BrCa incidence, significant in the majority of women with no prior BrCa risk factors. Also the results show that prior Prog but not prior E2 elevate the risk.3. These data indicate that HRT with E2 alone has a BrCa protective effect, while adding Prog increases the risk.4. These results are also compatible with a dual E2 effect on BrCa-genesis, where exogenous E2 are protective, but endogenous E2 [endE2] are carcinogenic, as shown from decades of anti-end E2 research with Tamoxifen, oophorectomy or Aromatase inhibitors.5. Based on these data we propose that in women with hysterectomy and no prior history of risk factors, the use of HRT with E2 alone as chemoprevention is plausible, and needs urgent verification.* significance, "p" &lt;0.05.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 908.

Preoperative tumor markers at diagnosis in women with malignant mixed müllerian tumors/carcinosarcoma of the uterus

CA125 is a well-recognized marker for endometrial cancer. Uterine malignant mixed müllerian tumors (MMMTs) are increasingly being recognized as an aggressive adenocarcinoma, not a sarcoma. There are no data in the literature regarding CA125 in this malignancy. One hundred twelve women with surgically staged MMMT, diagnosed between July 1990 and September 2005, had a retrospective chart review performed. Preoperative CA125 levels were available in 29 (26%) women. Seventeen (49%) women had levels above the upper limit of normal of 35 kμ/L. Mean levels increased with increasing surgical stage: stage I 53.4 kμ/L; stage II 122.5 kμ/L; stage III 147.1 kμ/L; and stage IV 428.4 kμ/L. Elevated levels of CA19-9, CEA, and CA15-3 were found in 8%, 12%, and 25%, respectively.

Myocardial protection by isoflurane vs. sevoflurane in ultra-fast-track anaesthesia for off-pump aortocoronary bypass grafting

BACKGROUND AND OBJECTIVES

Volatile anaesthetics have gained more popularity recently due to the potential for cardiac protection. Ultra-fast-track anaesthesia implies the immediate extubation after cardiac surgery. The purpose of this prospective randomized double-blind controlled study is to compare the cardioprotective effects of sevoflurane and isoflurane in off-pump cardiac bypass surgery.

METHODS

Forty patients undergoing elective off-pump cardiac bypass surgery with high thoracic epidural analgesia and immediate extubation at the end of surgery were randomized into two groups. During surgery, anaesthesia was provided with either 1 minimum alvelolar anaesthetic concentration of sevoflurane or 1 minimum alvelolar anaesthetic concentration of isoflurane. Troponin-T, creatine kinase-MB, left ventricular wall motion anomalies, time to extubation, respiratory functions and haemodynamic parameters were compared between the two groups by analysis of variance.

RESULTS

All patients were successfully extubated in the operating theatre with minimal postoperative pain. Serial creatine kinase-MB and troponin-T concentrations were not significantly different between the two volatile agents. Haemodynamic stability throughout surgery and contractility was not different between groups. However, extubation time was significantly shorter with sevoflurane (10 +/- 5 min) compared to isoflurane (18 +/- 4 min).

CONCLUSION

This study indicates that during off-pump cardiac bypass surgery, sevoflurane and isoflurane provide the same ischaemic cardioprotective effects. There is no difference for heart contractility and haemodynamic values during and after off-pump cardiac bypass surgery between the two agents. Sevoflurane allows a more rapid recovery from anaesthesia, but this does not translate into better pulmonary function or haemodynamics. Both agents are similar in ultra-fast-track off-pump cardiac bypass surgery.

Discovery of novel DNA gyrase inhibitors by high-throughput virtual screening

The bacterial type II topoisomerases DNA gyrase and topoisomerase IV are validated targets for clinically useful quinolone antimicrobial drugs. A significant limitation to widely utilized quinolone inhibitors is the emergence of drug-resistant bacteria due to an altered DNA gyrase. To address this problem, we have used structure-based molecular docking to identify novel drug-like small molecules that target sites distinct from those targeted by quinolone inhibitors. A chemical ligand database containing approximately 140,000 small molecules (molecular weight, <500) was molecularly docked onto two sites of Escherichia coli DNA gyrase targeting (i) a previously unexplored structural pocket formed at the dimer interface of subunit A and (ii) a small region of the ATP binding pocket on subunit B overlapping the site targeted by coumarin and cyclothialidine drugs. This approach identified several small-molecule compounds that inhibited the DNA supercoiling activity of purified E. coli DNA gyrase. These compounds are structurally unrelated to previously identified gyrase inhibitors and represent potential scaffolds for the optimization of novel antibacterial agents that act on fluoroquinolone-resistant strains.

Comparison of three different epidural solutions in off-pump cardiac surgery: pilot study

BACKGROUND

Immediate extubation using thoracic epidural analgesia (TEA) has become more popular after off-pump coronary artery bypass grafting (OPCAB). In this randomized prospective double-blind study, we present the first comparison of preoperative and postoperative haemodynamics during different regimens of TEA for immediate extubation after cardiac surgery.

METHODS

Sixty patients undergoing OPCAB were enrolled in this study. TEA was installed >1 h before application of heparin at levels T2-T4. Analgesia was provided by bupivacaine 0.25%, 8 ml, 15 min before surgery and extubation, and at 10 ml h(-1) during surgery and up to 72 h afterwards using one of the following regimens: bupivacaine 0.125% alone, bupivacaine 0.125% with fentanyl 3 microg ml(-1) or bupivacaine 0.125% with clonidine 0.6 microg ml(-1). Patients were block-randomized for one of the three treatments. Pain scores and infusion rates of TEA were assessed up to 48 h after surgery. Respiratory function was assessed by Pa(o2) and Pa(o2) immediately after surgery, and haemodynamic stability was recorded in the form of heart rate and diastolic and systolic blood pressure.

RESULTS

Patient characteristics, respiratory function and haemodynamic stability did not vary between the three groups. Pain control was very good and was not significantly different between the groups using similar infusion rates after surgery. Paraesthesia in dermatomes T1 or C8 occurred equally in all three groups. There was no neurological complication related to TEA in this study.

CONCLUSIONS

We conclude that immediate extubation after OPCAB using TEA is feasible with different TEA regimens. Respiratory function, haemodynamic stability and pain control are not different between TEA with bupivacaine alone, bupivacaine with fentanyl or bupivacaine with clonidine.

Hodgkin’s lymphoma in Chinese migrants to British Columbia:a 25-year survey

BACKGROUND

Compared with the West, Hodgkin's lymphoma in Oriental countries is characterized by a lower incidence rate and a higher proportion of mixed cellularity histology. Both environmental and genetic factors may be involved.

PATIENTS AND METHODS

The incidence and pattern of pathology of Hodgkin's lymphoma in the migrant Chinese population (0.4 million) in British Columbia (population 3.2 million) were studied. From a computerized database, all Hodgkin's lymphoma cases diagnosed in British Columbia from 1970 to 1997 were identified. Chinese descent was determined using patient surname by standard methodology and verified from the treatment record or by patient interview. The corresponding figures from the Chinese population in Hong Kong were used for comparison. For incidence rates, the age-specific incidence of Hodgkin's lymphoma in Hong Kong was obtained from the government cancer registry. For comparison of histology subtypes, 200 Hodgkin's lymphoma records from a Hong Kong regional referral center for the same time period were reviewed. Crude and age-standardized incidence rates were calculated by 5-year intervals in terms of age and calendar year, and relative rates were compared between the three populations.

RESULTS

From 1970 to 1997, Hodgkin's lymphoma was diagnosed in 34 Chinese patients in BC, with 24 cases diagnosed from 1970 to 1994. Thus, the crude and age-adjusted incidence rates from 1970 to 1994 were 0.91 and 1.14 per 100,000 per year in the British Columbia Chinese migrant population. Within the same period, 1862 cases of Hodgkin's lymphoma were diagnosed in British Columbia, giving a provincial background crude and age-adjusted incidence rates of 5.2 and 4.87 per 100,000 per year. The number of cases in the Hong Kong Chinese population (1970-1994) was 404, giving crude and age-adjusted incidence rates of 0.32 and 0.31 per 100,000 per year, respectively. Corrected for age and calendar year trends, the observed 25-year incidence of Hodgkin's lymphoma in British Columbia Chinese was significantly lower than expected from the British Columbia background population [24 observed versus 71 expected cases; standardized incidence ratio (SIR) = 0.34; 90% confidence interval (CI) 0.24-0.48; P <0.0001]. On the other hand, it is higher than that expected by extrapolating from the Hong Kong Chinese population (24 observed versus 8.5 expected cases; SIR = 2.81; 90% CI 1.94-3.95; P <0.0001). The difference is mainly accounted for by young patients with nodular sclerosis type disease in the migrant population.

CONCLUSIONS

Although any conclusion about the impact of migration on Hodgkin's lymphoma incidence and types in the Chinese population must be considered tentative due to the small number of observed cases and confounding variables such as age, changing diagnostic standards and secular trends in Hodgkin's lymphoma rates, our data demonstrate a tendency for the Chinese population of British Columbia to take on a Western pattern of Hodgkin's lymphoma. This observation provides additional evidence that both genetic and environmental influences play a role in the pathogenesis of this lymphoma, and that environmental factors can exert their influence over a relatively short period of time.

Rapamycin causes down-regulation of CCR5 and accumulation of anti-HIV beta-chemokines: an approach to suppress R5 strains of HIV-1

Propagation of R5 strains of HIV-1 on CD4 lymphocytes and macrophages requires expression of the CCR5 coreceptor on the cell surface. Individuals lacking CCR5 (CCR5 Delta 32 homozygous genotype) are phenotypically normal and resistant to infection with HIV-1. CCR5 expression on lymphocytes depends on signaling through the IL-2 receptor. By FACS analysis we demonstrate that rapamycin (RAPA), a drug that disrupts IL-2 receptor signaling, reduces CCR5 surface expression on T cells at concentrations as low as 1 nM. In addition, lower concentrations of RAPA (0.01 nM) were sufficient to reduce CCR5 surface expression on maturing monocytes. PCR analysis on peripheral blood mononuclear cells (PBMCs) showed that RAPA interfered with CCR5 expression at the transcriptional level. Reduced expression of CCR5 on PBMCs cultured in the presence of RAPA was associated with increased extracellular levels of macrophage inflammatory protein (MIP)-1 alpha and MIP-1 beta. In infectivity assays, RAPA suppressed the replication of R5 strains of HIV-1 both in PBMC and macrophage cultures. In total PBMC cultures, RAPA-mediated inhibition of CCR5-using strains of HIV-1 occurred at 0.01 nM, a concentration of drug that is approximately 103 times lower than therapeutic through levels of drug in renal transplant recipients. In addition, RAPA enhanced the antiviral activity of the CCR5 antagonist TAK-779. These results suggest that low concentrations of RAPA may have a role in both the treatment and prevention of HIV-1 infection.

The HIV protease inhibitor indinavir decreases insulin- and contraction-stimulated glucose transport in skeletal muscle

In many patients with human immunodeficiency virus (HIV) treated with HIV protease inhibitors, a complication develops that resembles abdominal obesity syndrome, with insulin resistance and glucose intolerance that, in some cases, progresses to diabetes. In this study, we tested the hypothesis that indinavir, an HIV-protease inhibitor, directly induces insulin resistance of glucose transport in skeletal muscle. Rat epitrochlearis muscles were incubated with a maximally effective insulin concentration (12 nmol/l) and 0, 1, 5, 20, or 40 micromol/l indinavir for 4 h. In control muscles, insulin increased 3-O-[(3)H]methyl-D-glucose (3MG) transport from 0.15 +/- 0.03 to 1.10 +/- 0.05 micromol. ml(-)(1). 10 min(-)(1). Incubation of muscles with 5 micromol/l indinavir reduced the insulin-stimulated increase in 3MG transport by 40%, whereas 20 micromol/l indinavir reduced the insulin-stimulated increase in 3MG transport by 58%. Indinavir induced a similar reduction in maximally insulin-stimulated 3MG transport in the soleus muscle. The increase in glucose transport activity induced by stimulating epitrochlearis muscles to contract was also markedly reduced by indinavir. The insulin-stimulated increase in cell-surface GLUT4, assessed using the 2-N-4-(1-azi-2,2,2-trifluoroethyl)benzoyl-1,3-bis-[2-(3)H] (D-mannose-4-yloxy)-2-propylamine exofacial photolabeling technique, was reduced by approximately 70% in the presence of 20 micromol/l indinavir. Insulin stimulation of phosphatidylinositol 3-kinase activity and phosphorylation of protein kinase B were not decreased by indinavir. These results provide evidence that indinavir inhibits the translocation or intrinsic activity of GLUT4 rather than insulin signaling.

EGR2 mutations in inherited neuropathies dominant-negatively inhibit myelin gene expression

The identification of EGR2 mutations in patients with neuropathies and the phenotype Egr2/Krox20(-/-) have demonstrated that the Egr2 transcription factor is critical for peripheral nerve myelination. However, the mechanism by which these mutations cause disease remains unclear, as most patients present with disease in the heterozygous state, whereas Egr2(+/-) mice are phenotypically normal. To understand the effect of aberrant Egr2 activity on Schwann cell gene expression, we performed microarray expression profiling to identify genes regulated by Egr2 in Schwann cells. These include genes encoding myelin proteins and enzymes required for synthesis of normal myelin lipids. Using these newly identified targets, we have shown that neuropathy-associated EGR2 mutants dominant-negatively inhibit wild-type Egr2-mediated expression of essential myelin genes to levels sufficiently low to result in the abnormal myelination observed in these patients.

Differential human immunodeficiency virus-suppressive activity of reverse transcription inhibitors in resting and activated peripheral blood lymphocytes: implications for therapy

OBJECTIVES

Because recent evidence indicates that human immunodeficiency virus type 1 (HIV-1) propagates in resting T lymphocytes in vivo, we wanted to evaluate the antiviral effects exerted by currently used nucleoside (NRTI) and non-nucleoside analog reverse transcription inhibitors in resting lymphocytes, and compare those effects to the ones obtained in activated lymphocytes.

METHODS

Tissue culture antiviral assays in which target cells are lymphocytes present in a resting or activated state. Virus replication was measured by a reverse transcription (RT) assay. Cell viability was evaluated using a commercial 3-(4k5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.

RESULTS

In vitro results obtained with concentrations of zidovudine and stavudine equivalent to drug levels found in plasma, showed more than 99% HIV-1 inhibition in activated lymphocytes but less than 50% virus inhibition in resting lymphocytes. Conversely, plasma levels of didanosine-inhibited HIV-1 by approximately 50% and 98% in activated and resting lymphocytes, respectively. Plasma level concentration of zalcitabine, lamivudine, and abacavir inhibited viral replication by more than 90% in both resting and activated cells.

CONCLUSIONS

These data demonstrate that specific NRTI antiretroviral agents have different activity against HIV RT, depending on the state of cell cycle of the infected cell. We suggest that the replication of HIV-1 in resting lymphocytes should be taken into account in the design of future clinical trials, as well as treatment antiretroviral regimens. Selection of combination RTIs so that they provide antiretroviral activity in both resting and activated lymphocytes may be a way to minimize treatment failure and the emergence of drug-resistant variants.

The correlation between epidermal growth factor levels in saliva and the severity of oral mucositis during oropharyngeal radiation therapy

BACKGROUND

Epidermal growth factor (EGF) is present in biologic fluids, including saliva, and plays a role in maintenance of the epithelial barrier and in healing of damaged mucosa. The purpose of this study was to assess the relation between salivary EGF and the severity of oral mucositis in patients with carcinoma of the head and neck during radiation therapy.

METHODS

Whole resting saliva (WRS) and whole stimulated saliva (WSS) were collected prior to radiation and each week during radiation treatment for 11 men and 7 women. Oral mucositis was evaluated using the National Cancer Institute (NCI) scale of 0-4 and the Oral Mucositis Assessment Scale (OMAS), which evaluates the extent of erythema (scale of 0-2) and ulcerations (scale of 0-3) in nine oral sites. The overall OMAS score of 0-45 reflected the mucosal condition. EGF was assayed in the saliva specimens.

RESULTS

The total mean radiation dose delivered to the head and neck was 5667 centigrays (cGy) in a mean of 24 fractions. Ulcerative oral mucositis occurred in 94% of patients. The mean OMAS score ranged from 2.83 in the first week of treatment to 14.77 in the fifth week. The mean WRS and WSS volumes decreased significantly from pretreatment to the first week of radiation treatment and then remained stable. A similar pattern was seen for the mean total output of EGF. A significant and negative correlation was found between higher levels of EGF in stimulated saliva and low OMAS score, reflecting less severe erythema and ulceration. A general trend showing that less tissue damage was associated with a higher EGF level in resting saliva also was illustrated. EGF levels were correlated with the OMAS score; however, no correlation was found when assessing the NCI score, which combines tissue damage with function and symptoms in a single score.

CONCLUSIONS

Radiation-induced mucositis appeared to be modified by saliva volume, total EGF, and concentration of EGF in the oral environment. Saliva volume and total EGF output decreased significantly in the first weeks of treatment and remained reduced throughout radiation therapy. The findings suggest that higher levels of EGF in saliva, particularly in stimulated saliva, prior to and during radiation treatment may be associated with less severe mucosal damage due to radiation therapy. It is also postulated that human EGF may affect the development and healing of radiation-damaged mucosa.

Primary structure of Noetia ponderosa hemoglobins: functional correlates

Homo- and heterodimeric hemoglobins have been isolated from the red cells of the arcid clam Noetia ponderosa (Np). These hemoglobins bind oxygen cooperatively. An extensively studied dimeric hemoglobin from another arcid clam, Scapaharca inaequivalvis, exhibits a molecular mechanism for cooperative ligand binding that is radically different from tetrameric vertebrate hemoglobins. In this study, the two chains found in both Noetia hemoglobins are sequenced and compared to the hemoglobins of the related clam S. inaequivalvis to determine whether Noetia hemoglobins have the structural basis for the same unusual mechanism for cooperative ligand binding and to inquire about the structural basis of absence of tetramers. Although the Noetia sequences are homologous to the Scapharca sequences, critical differences exist. The lack of tetramerization of Np subunits is most likely related to the absence of critical residues in the A and G helices that stabilize the interdimer contact seen in the Scapharca Hb tetramer. The lower affinity of the homodimer (Np-I), but particularly the heterodimer (Np-II) with respect to the homodimer and heterotetramer of Scapharca, can be due to (i) changes in the proximal heme environment and (ii) changes in the dimer interface. Interactions between Asn 100 and the heme of the other subunit are altered in Np-II due to the substitution of this residue by methionine, possibly causing the reduced O(2) affinity of the heterodimer of Noetia. (iii) Sequence changes in the E and F helices present in Np-I and Np-II could also contribute to the effect through interfacial changes. In particular, the substitution of Val for Thr in position 72 is expected to have a substantial influence on the interface. We conclude that Np dimers have the structural basis for a direct heme-heme interaction mechanism for cooperativity, as in Scapharca, but there are enough sequence changes to suggest that the pathway of interaction might be somewhat different.

DNA cleavage by 111In-labeled oligodeoxyribonucleotides

We studied the fine structure of DNA damage produced by the decay of 111In incorporated into duplex and triplex DNA strands to evaluate the usefulness of this radionuclide for sequence-specific DNA cleavage.

METHODS

Oligodeoxyribonucleotides (ODNs) were prepared with 111In attached by diethylenetriaminepentaacetic acid (DTPA) at the 5' end or 3' end through a long chemical linker or to an internal nucleotide position through a short linker. Subsequent formation of DNA duplexes and triplexes was confirmed by gel electrophoresis. The 111In-induced breaks were assayed in denaturing polyacrylamide gel electrophoresis with a single-nucleotide resolution.

RESULTS

111In-labeled oligonucleotides of high specific activity (740-1554 TBq/mmol) were synthesized. The presence of the bulky 111In-DTPA group did not impede duplex or triplex formation. Localized DNA breaks were observed in all duplexes and triplexes formed. The majority of DNA breaks in duplex formations were located within +/- 10 nucleotides from the site of attachment of the 111In-bearing linker. The yield of DNA breaks per decay was 0.38 in a duplex with internally modified ODNs. This is nearly 2 times less than the yield of DNA breaks in the same duplex with 1251 attached through the same linker. The yield of DNA breaks in the pyrimidine and purine strands of DNA triplexes with 111In attached to the triplex-forming ODNs through the linkers of different length varied from 0.05 to 0.10. The distribution of DNA breaks was wider in comparison with the duplex experiment. The lower yields of breaks per 111In decay compared with 125I may be not only the result of lower deposited energy but also of the ionic repulsion of the negatively charged 111In-DTPA group from the DNA strands.

CONCLUSION

We have shown that decay of 111In produces highly localized DNA breaks. 111In introduced into triplex- and duplex-forming ODNs through hydrocarbon linkers produces sequence-specific DNA strand breaks with an efficiency nearly comparable with that of 1251. These findings are supportive of our proposed use of 111In-ODNs for gene-specific radiotherapy.