Qualitative Evaluation of Common Quantitative Metrics for Clinical Acceptance of Automatic Segmentation: a Case Study on Heart Contouring from CT Images by Deep Learning Algorithms

Organs-at-risk contouring is time consuming and labour intensive. Automation by deep learning algorithms would decrease the workload of radiotherapists and technicians considerably. However, the variety of metrics used for the evaluation of deep learning algorithms make the results of many papers difficult to interpret and compare. In this paper, a qualitative evaluation is done on five established metrics to assess whether their values correlate with clinical usability. A total of 377 CT volumes with heart delineations were randomly selected for training and evaluation. A deep learning algorithm was used to predict the contours of the heart. A total of 101 CT slices from the validation set with the predicted contours were shown to three experienced radiologists. They examined each slice independently whether they would accept or adjust the prediction and if there were (small) mistakes. For each slice, the scores of this qualitative evaluation were then compared with the Sørensen-Dice coefficient (DC), the Hausdorff distance (HD), pixel-wise accuracy, sensitivity and precision. The statistical analysis of the qualitative evaluation and metrics showed a significant correlation. Of the slices with a DC over 0.96 (N = 20) or a 95% HD under 5 voxels (N = 25), no slices were rejected by the readers. Contours with lower DC or higher HD were seen in both rejected and accepted contours. Qualitative evaluation shows that it is difficult to use common quantification metrics as indicator for use in clinic. We might need to change the reporting of quantitative metrics to better reflect clinical acceptance.

Ultra-low-dose CT combined with noise reduction techniques for quantification of emphysema in COPD patients: An intra-individual comparison study with standard-dose CT

PURPOSE

Phantom studies in CT emphysema quantification show that iterative reconstruction and deep learning-based noise reduction (DLNR) allow lower radiation dose. We compared emphysema quantification on ultra-low-dose CT (ULDCT) with and without noise reduction, to standard-dose CT (SDCT) in chronic obstructive pulmonary disease (COPD).

METHOD

Forty-nine COPD patients underwent ULDCT (third generation dual-source CT; 70ref-mAs, Sn-filter 100kVp; median CTDIvol 0.38 mGy) and SDCT (64-multidetector CT; 40mAs, 120kVp; CTDIvol 3.04 mGy). Scans were reconstructed with filtered backprojection (FBP) and soft kernel. For ULDCT, we also applied advanced modelled iterative reconstruction (ADMIRE), levels 1/3/5, and DLNR, levels 1/3/5/9. Emphysema was quantified as Low Attenuation Value percentage (LAV%, ≤-950HU). ULDCT measures were compared to SDCT as reference standard.

RESULTS

For ULDCT, the median radiation dose was 84 % lower than for SDCT. Median extent of emphysema was 18.6 % for ULD-FBP and 15.4 % for SDCT (inter-quartile range: 11.8-28.4 % and 9.2 %-28.7 %, p = 0.002). Compared to SDCT, the range in limits of agreement of emphysema quantification as measure of variability was 14.4 for ULD-FBP, 11.0-13.1 for ULD-ADMIRE levels and 10.1-13.9 for ULD-DLNR levels. Optimal settings were ADMIRE 3 and DLNR 3, reducing variability of emphysema quantification by 24 % and 27 %, at slight underestimation of emphysema extent (-1.5 % and -2.9 %, respectively).

CONCLUSIONS

Ultra-low-dose CT in COPD patients allows dose reduction by 84 %. State-of-the-art noise reduction methods in ULDCT resulted in slight underestimation of emphysema compared to SDCT. Noise reduction methods (especially ADMIRE 3 and DLNR 3) reduced variability of emphysema quantification in ULDCT by up to 27 % compared to FBP.

Relationship between cardiovascular risk factors and coronary calcification in a middle-aged Dutch population: the Imalife study

Background

Systematic COronary Risk Evaluation (SCORE) has been proposed to assess the 10-year risk of fatal cardiovascular diseases, with distinction between low-risk and high-risk countries. Risk modifiers are recommended to further improve risk reclassification, for example the coronary artery calcium (CAC) score. CAC scoring can significantly improve risk prediction for coronary events based on outcome studies. The impact of CAC scoring on risk classification in a middle-aged cohort from a low-risk country in comparison to SCORE is unknown.

Purpose

To assess presence of coronary calcification and association with cardiovascular risk factors and related SCORE risk in a middle-aged population from a low risk country.

Methods

Coronary calcification and classical cardiovascular risk factors were analyzed in 4,083 Dutch participants aged 45–60 years (57.9% women) without a known history of coronary artery disease in the population-based ImaLife (Imaging in Lifelines) study. Individuals underwent non-contrast cardiac CT using third generation dual-source CT. Coronary artery calcium (CAC) scores were quantified using Agatston's method. Age- and sex- specific distributions of CAC categories (0, 1–99, 100–299, ≥300) and percentiles were assessed. Distribution of CAC categories was compared to SCORE risk categories (<1%, ≥1% to 5%, and ≥5%) for low risk countries. Relationship between risk factors and CAC presence was evaluated by logistic regression models. Population attributable fractions (PAFs) of classical risk factors for CAC presence were estimated to investigate potential prevention strategy.

Results

CAC was present in 54.5% of men and in 26.5% of women. With increasing age, an increasing percentage had a positive CAC score, from 38.1% of men and 15.2% of women at age 45–49 years, to 66.9% of men and 36.6% of women at age 55–60. Mean SCORE was 1.3% (2.0% in men, 0.7% in women). In SCORE risk <1%, 32.7% of men and 17.1% of women had CAC. In men with SCORE risk ≥5% (0.1% of women), 26.9% had no CAC. Overall PAF for presence of CAC of the classical risk factors was 18.5% in men and 31.4% in women. PAF was highest for hypertension (in men 8.0%, 95% CI 4.2–11.8%; in women 13.1%, 95% CI 7.9–18.2%) followed by hypercholesterolemia and obesity.

Conclusion

In this middle-aged Dutch cohort, slightly over half of men and a quarter of women had any CAC. With age there was an increase in CAC presence for both sexes. Only a minor proportion of CAC presence was attributable to classical risk factors. This provides further support that CAC scoring can impact risk classification in a middle-aged population of a low-risk country.

Funding Acknowledgement

Type of funding source: Other. Main funding source(s): The ImaLife study is supported by an institutional research grant from Siemens Healthineers and by the Ministry of Economic Affairs and Climate Policy by means of the PPP Allowance made available by the Top Sector Life Sciences & Health to stimulate public-private partnerships.

P5309Age and gender distributions of coronary artery calcium in the Dutch adult population: preliminary results of the ImaLife study

Background

Coronary artery calcium (CAC) scoring is a promising tool for cardiovascular risk classification. Population-based reference values are important for the clinical interpretation of CAC scores.

Purpose

To establish standards of CAC distributions by age and gender in an unselected Dutch population, which can be used to determine reference values.

Methods

ImaLife (Imaging in Lifelines) is a computed tomography (CT) based substudy of the Lifelines cohort, with a primary aim to establish reference values of imaging biomarkers for early stages of coronary artery disease in adults (above 45 years old). In total, 12,000 participants will be enrolled from an unselected adult population in the northern Netherlands for CAC scoring with third generation dual-source CT. CAC is quantified with dedicated commercial software using the Agatston method.

Results

Included so far were 3,702 participants (57.5% females, mean age 54 years, range 45–82 years). CAC was present in 39.2% of participants, with a higher prevalence of CAC in men (55.3%) than in women (27.3%). CAC scores increased with increasing age in both genders. The percentiles of CAC scores by age and gender groups are summarized in the table.

Agatston CAC score percentiles by age and gender Percentiles Women – Age, years Men – Age, years 45–49 50–54 55–59 60–64 65∼ 45–49 50–54 55–59 60–64 65∼ N 505 634 719 260 10 355 473 543 185 18 25th 0 0 0 0 0 0 0 0 1 75 50th 0 0 0 0 4 0 1 6 22 556 75th 0 0 6 33 386 6 21 72 129 751 90th 4 26 77 120 1037 49 154 242 500 1803

Conclusion

This preliminary result presents CAC distribution by age and gender in a middle-aged unselected Dutch population. Compared with the Heinz Nixdorf Recall study, CAC scores in our cohort for both genders were lower in the 5-year age groups between 45 and 64 years. Based on the overall data, expected within 2 years, reference values of CAC for the Dutch population can be established.

P1555Agreement of coronary calcium scoring on chest CT and ECG triggered cardiac CT: a population-based study

Background

Low-dose chest computed tomography (CT) is increasingly used in lung cancer screening. The heart is inherently visualized on chest CT. Coronary artery calcium (CAC) identified on chest scans has predictive value for risk of cardiovascular disease. There is discussion whether non-ECG-triggered chest CT is reliable for CAC scoring.

Purpose

To investigate the agreement between chest CT and ECG-triggered cardiac CT in CAC identification and risk classification.

Methods

We included 1000 ImaLife participants who underwent a cardiac scan immediately followed by a non-ECG triggered chest scan. Third-generation dual-source CT and dedicated software were used for scan acquisition and CAC measurement. Chest scans were analyzed after cardiac scans with an interval of at least a month and in a different order. To ensure a comparable prevalence of CAC with previous studies and adequate samples in CAC strata, after the inclusion of the 500th consecutive participants with zero CAC, only participants with >0 CAC based on dedicated cardiac CT were included. CAC scores were divided into four risk strata: 0, 1–99, 100–399, 400. Kappa was used to assess agreement in CAC identification (0 versus >0) and risk classification.

Results

The mean age was 54 years (range 45–77), 42.5% were women, average body mass index (BMI) was 26.1kg/m2. Compared with dedicated cardiac CT, non-ECG triggered chest CT had an accuracy of 0.97, sensitivity of 0.96 and specificity of 0.99 for identifying CAC, and agreement between scans was very high (kappa 0.95) for CAC presence. In terms of CAC risk strata, chest CT had a very high agreement with cardiac CT (kappa 0.95). Total misclassification rate of CAC strata was 6.5%, with most misclassified cases shifting one risk category downward (55/65, 85%). BMI of discordant pairs was significantly higher than concordant pairs, while no difference in heart rate was found.

Conclusion

Non-ECG triggered chest CT may be reliably used for CAC identification and risk classification since chest CT has very high agreement with dedicated cardiac CT results.

Centrifugo-pneumatic valving utilizing dissolvable films

In this article we introduce a novel technology that utilizes specialized water dissolvable thin films for valving in centrifugal microfluidic systems. In previous work (William Meathrel and Cathy Moritz, IVD Technologies, 2007), dissolvable films (DFs) have been assembled in laminar flow devices to form efficient sacrificial valves where DFs simply open by direct contact with liquid. Here, we build on the original DF valving scheme to leverage sophisticated, merely rotationally actuated vapour barriers and flow control for enabling comprehensive assay integration with low-complexity instrumentation on "lab-on-a-disc" platforms. The advanced sacrificial valving function is achieved by creating an inverted gas-liquid stack upstream of the DF during priming of the system. At low rotational speeds, a pocket of trapped air prevents a surface-tension stabilized liquid plug from wetting the DF membrane. However, high-speed rotation disrupts the metastable gas/liquid interface to wet the DF and thus opens the valve. By judicious choice of the radial position and geometry of the valve, the burst frequency can be tuned over a wide range of rotational speeds nearly 10 times greater than those attained by common capillary burst valves based on hydrophobic constrictions. The broad range of reproducible burst frequencies of the DF valves bears the potential for full integration and automation of comprehensive, multi-step biochemical assay protocols. In this report we demonstrate DF valving, discuss the biocompatibility of using the films, and show a potential sequential valving system including the on-demand release of on-board stored liquid reagents, fast centrifugal sedimentation and vigorous mixing; thus providing a viable basis for use in lab-on-a-disc platforms for point-of-care diagnostics and other life science applications.

Donor kidney adapts to body dimensions of recipient: no influence of donor gender on renal function after transplantation

Female kidneys and kidneys from small donors have been suggested to perform worse after kidney transplantation. Here, we evaluate the impact of gender and body dimensions on posttransplantation GFR in living donor transplantation. Two hundred and ninety-three donor-recipient pairs, who were transplanted at our center were evaluated. All pairs had detailed renal function measurement ((125) I-iothalamate and (131) I-hippuran) 4 months predonation in the donor and 2.5 months posttransplantation in donor and recipient. For 88 pairs, 5 years of recipient follow-up was available. Delta GFR was calculated as (recipient GFR-donor single kidney GFR). Recipients of both male and female kidneys had similar renal function at early and long term after transplantation. Male recipients had higher ERPF, ΔGFR and ΔERPF at both time points. Kidneys of donors smaller than their recipient had higher ΔGFR and ΔERPF than kidneys of larger donors at both time points (p < 0.05). In multivariate analysis, ΔGFR was predicted by donor/recipient BSA-ratio together with transplantation related factors (R(2) 0.19), irrespective of donor and recipient gender. In conclusion, in living donor transplantation, female kidneys perform as well as male donor kidneys. Kidneys adapt to the recipient's body size and demands, independent of gender, without detrimental effects in renal function and outcome up to mid-long term.

Detection of Mollicutes in bioreactor samples by real-time transcription-mediated amplification

AIM

Contamination by Mollicutes is a significant challenge for research laboratories and biopharmaceutical industry. It leads to alteration of results or production quality as well as loss of time, materials and revenue. These organisms can czoriginate from mammalian, avian, insect, plant or fish cells. Culture-based methods may require 28 days to detect Mollicutes. Traditional microbiology could advantageously be replaced by nucleic acid testing for earlier detection.

METHODS AND RESULTS

A membrane filtration-based concentration of the Mollicutes has been coupled to real-time transcription-mediated amplification (real-time TMA) to demonstrate these advantages. The eight species required by European Pharmacopoeia have been tested and were detected with sensitivity below 100 CFU per 20-ml sample. Co-culture experiments, in which Mollicutes are grown with CHO-S (suspension) or HEK 293 (adherent) cells, were also performed to respectively mimic a bioreactor or flask contamination. Despite the fact that Mollicutes can attach to or invade mammalian cells, they were consistently detected over multiple days.

CONCLUSIONS

the sample preparation and amplification method used in this study increases sensitivity and reduces time-to-result for detection of Mollicutes.

SIGNIFICANCE AND IMPACT OF THE STUDY

the described system allows real-time monitoring for microbial contamination of cell-based processes and products for the biopharmaceutical industry.

Nephrectomy elicits impact of age and BMI on renal hemodynamics: lower postdonation reserve capacity in older or overweight kidney donors

Renal functional reserve could be relevant for the maintenance of renal function after kidney donation. Low-dose dopamine induces renal vasodilation with a rise in glomerular filtration rate (GFR) in healthy subjects and is thought to be a reflection of reserve capacity (RC). Older age and higher body mass index (BMI) may be associated with reduced RC. We therefore investigated RC in 178 consecutive living kidney donors (39% males, age 48 +/- 11 years, BMI 25.5 +/- 4.1). RC was determined as the rise in GFR ((125)I-iothalamate), 4 months before and 2 months after donor nephrectomy. Before donor nephrectomy, GFR was 114 +/- 20 mL/min, with a reduction to 72 +/- 12 mL/min after donor nephrectomy. The dopamine-induced rise in GFR of 11 +/- 10% was reduced to 5 +/- 7% after donor nephrectomy (p < 0.001). Before donor nephrectomy, older age and higher BMI did not affect reserve capacity. After donor nephrectomy, the response of GFR to dopamine independently and negatively correlated with older age and higher BMI. Moreover, postdonation reserve capacity was absent in obese donors. The presence of overweight had more impact on loss of RC in younger donors. In conclusion, donor nephrectomy unmasked an age- and overweight-induced loss of reserve capacity. Younger donors with obesity should be carefully monitored.

Predictive capacity of pre-donation GFR and renal reserve capacity for donor renal function after living kidney donation

Kidney transplantation from living donors is important to reduce organ shortage. Reliable pre-operative estimation of post-donation renal function is essential. We evaluated the predictive potential of pre-donation glomerular filtration rate (GFR) (iothalamate) and renal reserve capacity for post-donation GFR in kidney donors. GFR was measured in 125 consecutive donors (age 49 +/- 11 years; 36% male) 119 +/- 99 days before baseline GFR (GFRb) and 57 +/- 16 days after donation (GFRpost). Reserve capacity was assessed as GFR during stimulation by low-dose dopamine (GFRdopa), amino acids (GFRAA) and both (GFRmax). GFRb was 112 +/- 18, GFRdopa 124 +/- 22, GFRAA 127 +/- 19 and GFRmax 138 +/- 22 mL/min. After donation, GFR remained 64 +/- 7%. GFRpost was predicted by GFRb(R2 = 0.54), GFRdopa(R2 = 0.35), GFRAA(R2 = 0.56), GFRmax(R2 = 0.55)and age (R2 = -0.22; p < 0.001 for all). Linear regression provided the equation GFRpost = 20.01 + (0.46*GFRb). Multivariate analysis predicted GFRpost by GFRb, age and GFRmax(R2 = 0.61, p < 0.001). Post-donation renal function impairment (GFR < or = 60 mL/min/1.73 m2) occurred in 31 donors. On logistic regression, GFRb, body mass index (BMI) and age were independent predictors for renal function impairment, without added value of reserve capacity. GFR allows a relatively reliable prediction of post-donation GFR, improving by taking age and stimulated GFR into account. Long-term studies are needed to further assess the prognostic value of pre-donation characteristics and to prospectively identify subjects with higher risk for renal function loss.

DNA amplification method tolerant to sample degradation

Despite recent advances in linear whole genome amplification of intact DNA/RNA, amplification of degraded nucleic acids in an unbiased fashion remains a serious challenge for genetic diagnosis. We describe a new whole genome amplification procedure, RCA-RCA (Restriction and Circularization-Aided Rolling Circle Amplification), which retains the allelic differences among degraded amplified genomes while achieving almost complete genome coverage. RCA-RCA utilizes restriction digestion and whole genome circularization to generate genomic sequences amenable to rolling circle amplification. When intact genomic DNA is used, RCA-RCA retains gene-amplification differences (twofold or higher) between complex genomes on a genome-wide scale providing highly improved concordance with unamplified material as compared with other amplification methodologies including multiple displacement amplification. Using RCA-RCA, formalin-fixed samples of modest or substantial DNA degradation were successfully amplified and screened via array-CGH or Taqman PCR that displayed retention of the principal gene amplification features of the original material. Microsatellite analysis revealed that RCA-RCA amplified genomic DNA is representative of the original material at the nucleotide level. Amplification of cDNA is successfully performed via RCA-RCA and results to unbiased gene expression analysis (R(2) = 0.99). The simplicity and universal applicability of RCA-RCA make it a powerful new tool for genome analysis with unique advantages over previous amplification technologies.

Balanced-PCR amplification allows unbiased identification of genomic copy changes in minute cell and tissue samples

Analysis of genomic DNA derived from cells and fresh or fixed tissues often requires whole genome amplification prior to microarray screening. Technical hurdles to this process are the introduction of amplification bias and/or the inhibitory effects of formalin fixation on DNA amplification. Here we demonstrate a balanced-PCR procedure that allows unbiased amplification of genomic DNA from fresh or modestly degraded paraffin-embedded DNA samples. Following digestion and ligation of a target and a control genome with distinct linkers, the two are mixed and amplified in a single PCR, thereby avoiding biases associated with PCR saturation and impurities. We demonstrate genome-wide retention of allelic differences following balanced-PCR amplification of DNA from breast cancer and normal human cells and genomic profiling by array-CGH (cDNA arrays, 100 kb resolution) and by real-time PCR (single gene resolution). Comparison of balanced-PCR with multiple displacement amplification (MDA) demonstrates equivalent performance between the two when intact genomic DNA is used. When DNA from paraffin-embedded samples is used, balanced PCR overcomes problems associated with modest DNA degradation and produces unbiased amplification whereas MDA does not. Balanced-PCR allows amplification and recovery of modestly degraded genomic DNA for subsequent retrospective analysis of human tumors with known outcomes.

International comparison of quality indicators in United States, Icelandic and Canadian nursing facilities

AIM

To discuss the results of a comparison using minimum data set (MDS)-based quality indicators (QIs) for residents in nursing facilities in three countries (Iceland; Ontario, Canada; and Missouri, United States) together with implications regarding nursing practices and resident outcomes in these countries.

METHOD

Data were extracted from databases in each country for four consecutive quarterly periods during 1997 and 1998. All facilities investigated had the required consecutive quarterly data. Analytical techniques were matched to measure resident outcomes using the same MDS-based QIs in the three countries.

RESULTS

Similarities among the three countries included the use of nine or more multiple medications, weight loss, urinary tract infection, dehydration, and behavioural symptoms that affect others. Differences among the three countries included bowel and bladder incontinence, indwelling catheter use, fecal impaction, tube feeding use, development of pressure ulcers, bedridden residents, physical restraint use, depression without receiving antidepressant therapy, residents with depression, use of anti-anxiety or hypnotic drugs, use of anti-psychotic drugs in the absence of psychotic and related conditions, residents spending little or no time in activities, and falls.

CONCLUSIONS

Comparisons highlighted differences in clinical practices among countries, which may account for differences in resident outcomes. Learning from each other's best practices can improve the quality of care for older people in nursing homes in many countries.

International field test results of the Observable Indicators of Nursing Home Care Quality instrument

Researchers at the University of Missouri-Columbia developed the Observable Indicators of Nursing Home Care Quality instrument to measure the dimensions of nursing home care quality during a brief on-site visit to a nursing home. The instrument has been translated for use in Iceland and used in Canada. Results of the validity and reliability studies using the instrument in 12 nursing homes in Reykjavik, in a large Veterans Home in Ontario with 14 units tested separately, and in 20 nursing homes in Missouri, are promising. High-content validity was observed in all countries, together with excellent inter-rater reliability and coefficient alpha. Test-retest reliabilities in Iceland and Missouri were good. Results of the international field test of the Observable Indicators of Nursing Home Care Quality instrument points to the usefulness of such an instrument in measuring nursing home care quality following a quick on-site observation in a nursing facility. The instrument should be used as a facility-wide assessment of quality, rather than for individual units within a facility. We strongly recommend its use by practising nurses in nursing homes to assess quality of care and guide efforts to improve care. We recommend its use by researchers and consumers and further testing of the use of the instrument with regulators.

Evaluation of communication surrounding the implementation of the resident assessment instrument

Two outcomes of the introduction of the Resident Assessment Instrument at Sunnybrook Health Sciences Centre in 1996 were (1) a communication plan and (2) patient unit RAI communication centres. This article describes a survey that was used to evaluate the effectiveness of the plan and centres in implementing the RAI Staff identified the InfoRAInbow Newsletter as the most useful communication strategy. Satisfaction with communication about the RAI implementation was only 57 percent. Further investigation of this level of satisfaction is required. This result may be attributed to the "choices" staff make as to whether or not to read information, or to environmental factors that occurred at the time of the survey's completion. Future directions for improving the RAI Communication Plan should focus on environmental factors that may impede communication of information, especially information that affects integration of the RAI into the clinical care system.

Implementation of the resident assessment instrument: a Canadian experience

As the population ages, the increasing number and complexity of needs of individuals requiring institutionalization will increase the demands for chronic care services. In this article, the authors describe the implementation process used to introduce interdisciplinary staff to the use of the Minimum Data Set (MDS) for assessment of both nursing home and chronic care residents. This screening tool assesses resident characteristics over a wide spectrum of dimensions. The assessment findings are then integrated into the clinical plan of care.

Quality control (Part 2). Communication: implementation of the Resident Assessment Instrument (RAI): the benefits of a structured communication plan

Following a government mandate to use the assessment portion of the Resident Assessment Instrument, S&WCHSC began to integrate the RAI into the care of its Aging Program residents. S&WCHSC have used this as an opportunity to provide a structure for assessment and care planning within the existing philosophy of Patient Focused Care. Implementation of the RAI required the development and implementation of a Communication Plan. An adaptation of a framework, "Effective Strategic Planning for Communications" provided guidelines for assessment of key stakeholders' communication needs.

Transfection with different connexin genes alters growth and differentiation of human choriocarcinoma cells

To examine the role of cell-cell communication via gap junctions in controlling proliferation and differentiation we transfected the malignant trophoblast cell line Jeg-3, which exhibits extremely low cell-cell communication mediated by endogenously expressed connexin40, with connexin26, connexin40, and connexin43, respectively. In vitro growth of all cell clones transfected with connexin genes was significantly reduced compared to controls. This effect corresponded to a significant increase in total junctional conductance of all clones. Single-channel conductances for channels formed by the transfected connexins were in the range of the values published previously. Though total junctional conductance varied highly among clones and even within one clone, differentiation of the cells indicated by beta-hCG secretion was most prominent in the clones that revealed the largest amount of well-coupled cell pairs. Connexin26 channels enable cells of one clone to reduce drastically growth rate and produce significantly higher secretion of beta-hCG. Connexin43 had only moderate effects on the differentiation properties of Jeg-3 cells. These findings suggest that restoration of cell-cell communication plays a role in growth reduction and in differentiation of tumor cells and that different channel proteins might have different effects.

The procoagulant effect of thrombin on fibrin(ogen)-bound platelets

In a final stage of activation, platelets become procoagulant because of the appearance of phosphatidylserine (PS) at the membrane outer surface. This PS exposure requires a rise in cytosolic [Ca(2+)](i), is accompanied by formation of membrane blebs, and stimulates the formation of thrombin from its precursor prothrombin. Here, we investigated whether thrombin, as a potent platelet agonist, can induce this procoagulant response in plasma-free platelets interacting with fibrin or fibrinogen through their integrin alpha(IIb)beta(3) receptors. First, in platelets that were stimulated to spread over fibrin or fibrinogen surfaces with adrenaline, addition of thrombin and CaCl(2) caused a potent Ca(2+) signal that in about 30% of the cells was accompanied by exposure of PS. At low doses, integrin alpha(IIb)beta(3) receptor antagonist (RGD peptide) inhibited platelet spreading as well as thrombin-evoked PS exposure. Second, in platelet-fibrinogen microaggregates that were preformed in the presence of adrenaline, thrombin/CaCl(2) induced PS exposure and bleb formation of about 35% of the cells. Third, a potent, thrombin-dependent stimulation of prothrombinase activity was measured in platelet suspensions that were incubated with a fibrin clot. These results indicate that, in the absence of coagulating plasma, thrombin is a moderate inducer of the procoagulant response of platelets, once integrin alpha(IIb)beta(3)-mediated interactions are stimulated (by adrenaline) and CaCl(2) is present.

Revolutionary versus evolutionary change: the experience of a university hospital department of psychiatry

In the spring of 1991, the Department of Psychiatry at Sunnybrook Health Science Centre chose to undergo a major reorganization in an attempt to better meet the needs of patients as well as the academic and research requirements of the University of Toronto. This brief report describes the circumstances leading up to the decision to make a "revolutionary" change, the department's experiences during the period of radical change and the impacts of the change process.