Regional practice variation in hysterectomy and the implementation of less invasive surgical procedures: A register-based study in the Netherlands.

INTRODUCTION: Many women experience bleeding disorders that may have an anatomical or unexplained origin. Although hysterectomy is the most definitive and common treatment, it is highly invasive and resource-intensive. Less invasive therapies are therefore advised before hysterectomy for women with fibroids or bleeding disorders. This study has two aims related to treating bleeding disorders and uterine fibroids in the Netherlands: (1) to evaluate the regional variations in prevalence and surgical approaches; and (2) to assess the associations between regional rates of hysterectomies and less invasive surgical techniques to analyze whether hysterectomy can be replaced in routine practice. MATERIAL AND METHODS: We completed a register-based study of claims data for bleeding disorders and fibroids in women between 2016 and 2020 using data from Statistics Netherlands for case-mix adjustment. Crude and case-mix adjusted regional hysterectomy rates were examined overall and by surgical approach. Coefficients of variation were used to measure regional variation and regression analyses were used to evaluate the association between hysterectomy and less invasive procedure rates across regions. RESULTS: Overall, 14 186 and 8821 hysterectomies were performed for bleeding disorders and fibroids, respectively. Laparoscopic approaches predominated (bleeding disorders 65%, fibroids 49%), followed by vaginal (bleeding disorders 24%, fibroids 5%) and abdominal (bleeding disorders 11%, fibroids 46%) approaches. Substantial regional differences were noted in both hysterectomy rates and the surgical approaches. For bleeding disorders, regional hysterectomy rates were positively associated with endometrial ablation rates (ß = 0.11; P = 0.21) and therapeutic hysteroscopy rates (ß = 0.14; P = 0.31). For fibroids, regional hysterectomy rates were positively associated with therapeutic hysteroscopy rates (ß = 0.10; P = 0.34) and negatively associated with both embolization rates (ß = -0.08; P = 0.08) and myomectomy rates (ß = -0.03; P = 0.82). CONCLUSIONS: Regional variation exists in the rates of hysterectomy and minimally invasive techniques. The absence of a significant substitution effect provides no clear evidence that minimally invasive techniques have replaced hysterectomy in clinical practice. However, although the result was not significant, embolization could be an exception based on its stronger negative association.

Do women living in a deprived neighborhood have higher maternity care costs and worse pregnancy outcomes? A retrospective population-based study.

BACKGROUND: Living in a deprived neighborhood is associated with poorer health, due to factors such as lower socio-economic status and an adverse lifestyle. There is little insight into whether living in deprived neighborhood is associated with adverse maternity care outcomes and maternity health care costs. We expect women in a deprived neighborhood to experience a more complicated pregnancy, with more secondary obstetric care (as opposed to primary midwifery care) and higher maternity care costs. This study aimed to answer the following research question: to what extent are moment of referral from primary to secondary care, mode of delivery, (extreme or very) preterm delivery and maternity care costs associated with neighborhood deprivation? METHODS: This retrospective cohort study used a national Dutch database with healthcare claims processed by health insurers. All pregnancies that started in 2018 were included. The moment of referral from primary to secondary care, mode of delivery, (extreme or very) preterm delivery and maternity care costs were compared between women in deprived and non-deprived neighborhoods. We reported descriptive statistics, and results of ordinal logistic, multinomial and linear regressions to assess whether differences between the two groups exist. RESULTS: Women in deprived neighborhoods had higher odds of being referred from primary to secondary care during pregnancy (adjusted OR 1.49, 95%CI 1.41-1.57) and to start their pregnancy in secondary care (adjusted OR 1.55, 95%CI 1.44-1.66). Furthermore, women in deprived neighborhoods had lower odds of assisted delivery than women in non-deprived neighborhoods (adjusted OR 0.73, 95%CI 0.66-0.80), and they had higher odds of a cesarean section (adjusted OR 1.19, 95%CI 1.13-1.25). On average, women in a deprived neighborhood had higher maternity care costs worth 156 euros (95%CI 104-208). CONCLUSION: This study showed that living in a deprived neighborhood is associated with more intensive maternal care and higher maternal care costs in the Netherlands. These findings support the needs for greater attention to socio-economic factors in maternity care in the Netherlands.

Practice variation in the stepped care approach to idiopathic heavy menstrual bleeding: A population-based study.

INTRODUCTION: Heavy menstrual bleeding (HMB) affects a quarter of all women, with half having no structural cause. Dutch guidelines recommend a stepped care approach to the management of such idiopathic HMB, starting with medication or a levonorgestrel-releasing intrauterine device (LNG-IUD), before progressing to endometrial ablation, and ultimately, hysterectomy. However, practice variation between hospitals could lead to suboptimal health outcomes and increased healthcare costs for some women. OBJECTIVES: To evaluate adherence to stepped care for women with idiopathic HMB and to identify practice variation among Dutch hospitals. STUDY DESIGN: This population-based cross-sectional study used Dutch insurance claims data from primary and secondary care for all women with idiopathic HMB referred to a gynecologist between January 2019 and December 2020. We calculated the average number of treatments in the 3 years before each treatment step at each hospital, making adjustments for age, socioeconomic status, and ethnicity. Variation in medical practice was measured by the coefficient of variation (CV). RESULTS: We studied 20,715 women treated with LNG-IUDs (56%), endometrial ablation (36%), laparoscopic hysterectomy (13%), or vaginal hysterectomy (4%) in 93 hospitals. Before endometrial ablation, on average 47% used medication (hospital range 27%-71%; CV 0.17) and 16% used an LNG-IUD (hospital range 8%-29%, CV 0.32). Before hysterectomy, 52% (hospital range 28%-65%, CV 0.16) used medication, 21% (hospital range 6%-38%, CV 0.35) used an LNG-IUD, and 23% underwent endometrial ablation (hospital range 0%-59%, CV 0.55). On average, women underwent 0.63 (hospital range 0.36-1.00, adjusted rate 0.40-0.98, CV 0.17) and 0.96 (hospital range 0.56-1.45, adjusted rate 0.56-1.44, CV 0.18) treatments before endometrial ablation and hysterectomy, respectively. CONCLUSIONS: Considerable practice variation exists among Dutch hospitals in the stepped care approach to idiopathic HMB. Improving adherence to this approach could improve quality of care and reduce costs.

Do patients' preferences prevail in hospital selection?: a comparison between discrete choice experiments and revealed hospital choice.

BACKGROUND: In patient choice, patients are expected to select the provider that best fits their preferences. In this study, we assess to what extent the hospital choice of patients in practice corresponds with their preferred choice. METHODS: Dutch patients with breast cancer (n = 631) and cataract (n = 1109) were recruited. We employed a discrete choice experiment (DCE) per condition to measure stated preferences and predict the distribution of patients across four hospitals. Each DCE included five attributes: patient experiences, a clinical outcome indicator, waiting time, travel distance and whether the hospital had been recommended (e.g., by the General Practitioner (GP)). Revealed choices were derived from claims data. RESULTS: Hospital quality was valued as most important in the DCE; the largest marginal rates of substitution (willingness to wait) were observed for the clinical outcome indicator (breast cancer: 38.6 days (95% confidence interval (95%CI): 32.9-44.2); cataract: 210.5 days (95%CI: 140.8-280.2)). In practice, it was of lesser importance. In revealed choices, travel distance became the most important attribute; it accounted for 85.5% (breast cancer) and 95.5% (cataract) of the log-likelihood. The predicted distribution of patients differed from that observed in practice in terms of absolute value and, for breast cancer, also in relative order. Similar results were observed in population weighted analyses. DISCUSSION: Study findings show that patients highly valued quality information in the choice for a hospital. However, in practice these preferences did not prevail. Our findings suggest that GPs played a major role and that patients mostly ended up selecting the nearest hospital.

How important is income in explaining individuals having forgone healthcare due to cost-sharing payments? Results from a mixed methods sequential explanatory study.

BACKGROUND: Patients having forgone healthcare because of the costs involved has become more prevalent in recent years. Certain patient characteristics, such as income, are known to be associated with a stronger demand-response to cost-sharing. In this study, we first assess the relative importance of patient characteristics with regard to having forgone healthcare due to cost-sharing payments, and then employ qualitative methods in order to understand these findings better. METHODS: Survey data was collected from a Dutch panel of regular users of healthcare. Logistic regression models and dominance analyses were performed to assess the relative importance of patient characteristics, i.e., personal characteristics, health, educational level, sense of mastery and financial situation. Semi-structured interviews (n = 5) were conducted with those who had forgone healthcare. The verbatim transcribed interviews were thematically analyzed. RESULTS: Of the 7,339 respondents who completed the questionnaire, 1,048 respondents (14.3%) had forgone healthcare because of the deductible requirement. The regression model indicated that having a higher income reduced the odds of having forgone recommended healthcare due to the deductible (odds ratios of higher income categories relative to the lowest income category (reference): 0.29-0.49). However, dominance analyses revealed that financial leeway was more important than income: financial leeway contributed the most (34.8%) to the model's overall McFadden's pseudo-R2 (i.e., 0.123), followed by income (25.6%). Similar results were observed in stratified models and in population weighted models. Qualitative analyses distinguished four main themes that affected the patient's decision whether to use healthcare: financial barriers, structural barriers related to the complex design of cost-sharing programs, individual considerations of the patient, and the perceived lack of control regarding treatment choices within a given treatment trajectory. Furthermore, "having forgone healthcare" seemed to have a negative connotation. CONCLUSION: Our findings show that financial leeway is more important than income with respect to having forgone recommended healthcare due to cost-sharing payments, and that other factors such as the perceived necessity of healthcare also matter. Our findings imply that solely adapting cost-sharing programs to income levels will only get one so far. Our study underlines the need for a broader perspective in the design of cost-sharing programs.

On the correlation between outcome indicators and the structure and process indicators used to proxy them in public health care reporting.

Hospital quality indicators provide valuable insights for quality improvement, empower patients to choose providers, and have become a cornerstone of value-based payment. As outcome indicators are cumbersome and expensive to measure, many health systems have relied on proxy indicators, such as structure and process indicators. In this paper, we assess the extent to which publicly reported structure and process indicators are correlated with outcome indicators, to determine if these provide useful signals to inform the public about the outcomes. Quality indicators for three conditions (breast and colorectal cancer, and hip replacement surgery) for Dutch hospitals (2011-2018) were collected. Structure and process indicators were compared to condition-specific outcome indicators and in-hospital mortality ratios in a between-hospital comparison (cross-sectional and between-effects models) and in within-hospital comparison (fixed-effects models). Systematic association could not be observed for any of the models. Both positive and negative signs were observed where negative associations were to be expected. Despite sufficient statistical power, the share of significant correlations was small [mean share: 13.2% (cross-sectional); 26.3% (between-effects); 13.2% (fixed-effects)]. These findings persisted in stratified analyses by type of hospital and in models using a multivariate approach. We conclude that, in the context of compulsory public reporting, structure and process indicators are not correlated with outcome indicators, neither in between-hospital comparisons nor in within-hospital comparisons. While structure and process indicators remain valuable for internal quality improvement, they are unsuitable as signals for informing the public about hospital differences in health outcomes.

On selecting quality indicators: preferences of patients with breast and colon cancers regarding hospital quality indicators.

BACKGROUND: There is an increasing number of quality indicators being reported publicly with aim to improve the transparency on hospital care quality. However, they are little used by patients. Knowledge on patients' preferences regarding quality may help to optimise the information presented to them. OBJECTIVE: To measure the preferences of patients with breast and colon cancers regarding publicly reported quality indicators of Dutch hospital care. METHODS: From the existing set of clinical quality indicators, participants of patient group discussions first assessed an indicator's suitability as choice information and then identified the most relevant ones. We used the final selection as attributes in two discrete choice experiments (DCEs). Questionnaires included choice vignettes as well as a direct ranking exercise, and were distributed among patient communities. Data were analysed using mixed logit models. RESULTS: Based on the patient group discussions, 6 of 52 indicators (breast cancer) and 5 of 21 indicators (colon cancer) were selected as attributes. The questionnaire was completed by 84 (breast cancer) and 145 respondents (colon cancer). In the patient group discussions and in the DCEs, respondents valued outcome indicators as most important: those reflecting tumour residual (breast cancer) and failure to rescue (colon cancer). Probability analyses revealed a larger range in percentage change of choice probabilities for breast cancer (10.9%-69.9%) relative to colon cancer (7.9%-20.9%). Subgroup analyses showed few differences in preferences across ages and educational levels. DCE findings partly matched with those of direct ranking. CONCLUSION: Study findings show that patients focused on a subset of indicators when making their choice of hospital and that they valued outcome indicators the most. In addition, patients with breast cancer were more responsive to quality information than patients with colon cancer.

The effect of cost-sharing design characteristics on use of health care recommended by the treating physician; a discrete choice experiment.

BACKGROUND: Cost-sharing programs are often too complex to be easily understood by the average insured individual. Consequently, it is often difficult to determine the amount of expenses in advance. This may preclude well-informed decisions of insured individuals to adhere to medical treatment advised by the treating physician. Preliminary research has showed that the uncertainty in these cost-sharing payments are affected by four design characteristics, i.e. 1) type of payments (copayments, coinsurances or deductibles), 2) rate of payments, 3) annual caps on cost-sharing and 4) moment that these payments must be made (directly at point of care or billed afterwards by the insurer). METHODS: An online discrete choice experiment was used to assess the extent to which design characteristics of cost-sharing programs affect the decision of individuals to adhere to recommended care (prescribed medications, ordered diagnostic tests and referrals to medical specialist care). Analyses were performed using mixed multinomial logits. RESULTS: The questionnaire was completed by 7921 members of a patient organization. Analyses showed that 1) cost-sharing programs that offer clear information in advance on actual expenses that are billed afterwards, stimulate adherence to care recommended by the treating physician; 2) the relative importance of the design characteristics differed between respondents who reported to have forgone health care due to cost-sharing and those who did not; 3) price-awareness among respondents was limited; 4) the utility derived from attributes and respondents' characteristics were positively correlated; 5) an optimized cost-sharing program revealed an adherence of more than 72.9% among those who reported to have forgone health care. CONCLUSIONS: The analyses revealed that less complex cost-sharing programs stimulate adherence to recommended care. If these programs are redesigned accordingly, individuals who had reported to have forgone a health service recommended by their treating physician due to cost-sharing, would be more likely to use this service. Such redesigned programs provide a policy option to reduce adverse health effects of cost-sharing in these groups. Considering the upcoming shift from volume-based to value-based health care provision, insights into the characteristics of a cost-sharing program that stimulates the use of recommended care may help to design value-based insurance plans.

Expanding marine protected areas to include degraded coral reefs.

Marine protected areas (MPAs) are a commonly applied solution to coral reef degradation, yet coral reefs continue to decline worldwide. We argue that expanding the range of MPAs to include degraded reefs (DR-MPA) could help reverse this trend. This approach requires new ecological criteria for MPA design, siting, and management. Rather than focusing solely on preserving healthy reefs, our approach focuses on the potential for biodiversity recovery and renewal of ecosystem services. The new criteria would help identify sites with the highest potential for recovery and the greatest resistance to future threats (e.g., increased temperature and acidification) and sites that contribute to MPA connectivity. The DR-MPA approach is a compliment rather than a substitute for traditional MPA design approaches. We believe that the DR-MPA approach can enhance the natural, or restoration-assisted, recovery of DRs and their ecosystem services; increase total reef area available for protection; promote more resilient and better-connected MPA networks; and improve conditions for human communities dependent on MPA ecosystem services.

L-arginine promotes gut hormone release and reduces food intake in rodents.

AIMS: To investigate the anorectic effect of L-arginine (L-Arg) in rodents. METHODS: We investigated the effects of L-Arg on food intake, and the role of the anorectic gut hormones glucagon-like peptide-1 (GLP-1) and peptide YY (PYY), the G-protein-coupled receptor family C group 6 member A (GPRC6A) and the vagus nerve in mediating these effects in rodents. RESULTS: Oral gavage of L-Arg reduced food intake in rodents, and chronically reduced cumulative food intake in diet-induced obese mice. Lack of the GPRC6A in mice and subdiaphragmatic vagal deafferentation in rats did not influence these anorectic effects. L-Arg stimulated GLP-1 and PYY release in vitro and in vivo. Pharmacological blockade of GLP-1 and PYY receptors did not influence the anorectic effect of L-Arg. L-Arg-mediated PYY release modulated net ion transport across the gut mucosa. Intracerebroventricular (i.c.v.) and intraperitoneal (i.p.) administration of L-Arg suppressed food intake in rats. CONCLUSIONS: L-Arg reduced food intake and stimulated gut hormone release in rodents. The anorectic effect of L-Arg is unlikely to be mediated by GLP-1 and PYY, does not require GPRC6A signalling and is not mediated via the vagus. I.c.v. and i.p. administration of L-Arg suppressed food intake in rats, suggesting that L-Arg may act on the brain to influence food intake. Further work is required to determine the mechanisms by which L-Arg suppresses food intake and its utility in the treatment of obesity.

Measuring Healthcare Providers' Performances Within Managed Competition Using Multidimensional Quality and Cost Indicators.

BACKGROUND AND OBJECTIVES: The Dutch healthcare system is in transition towards managed competition. In theory, a system of managed competition involves incentives for quality and efficiency of provided care. This is mainly because health insurers contract on behalf of their clients with healthcare providers on, potentially, quality and costs. The paper develops a strategy to comprehensively analyse available multidimensional data on quality and costs to assess and report on the relative performance of healthcare providers within managed competition. DATA AND METHODS: We had access to individual information on 2409 clients of 19 Dutch diabetes care groups on a broad range of (outcome and process related) quality and cost indicators. We carried out a cost-consequences analysis and corrected for differences in case mix to reduce incentives for risk selection by healthcare providers. RESULTS AND CONCLUSION: There is substantial heterogeneity between diabetes care groups' performances as measured using multidimensional indicators on quality and costs. Better quality diabetes care can be achieved with lower or higher costs. Routine monitoring using multidimensional data on quality and costs merged at the individual level would allow a systematic and comprehensive analysis of healthcare providers' performances within managed competition.

Sociodemographic Differences in the Use of Electronic Nicotine Delivery Systems in the European Union.

INTRODUCTION: Electronic nicotine delivery systems (ENDS) are rapidly increasing in popularity. However, little is known about sociodemographic differences in use of ENDS. This study aims to assess the sociodemographic characteristics associated with ENDS ever-use and use as a cessation tool in the European Union. METHODS: We analyzed data from the 2012 Eurobarometer wave 77.1, with 25 922 respondents aged 15 years or above from all 27 member states. We estimated the prevalence of ever-use and use as a cessation tool, and performed binary logistic regression to analyze associations with sociodemographic characteristics. RESULTS: Overall, 7.2% reported having ever used ENDS. Of all smokers who ever tried to quit, 7.0% used ENDS. Ever-use was inversely associated with being older than 34 years (odds ratio [OR] = 0.63, 95% confidence interval [CI] = 0.51-0.76 for 35-44 years, and OR = 0.34, 95% CI = 0.25-0.46 for at least 65 years), and positively associated with being higher educated (OR = 1.50, 95% CI = 1.22-1.84) or a student (OR = 2.34, 95% CI = 1.77-3.08). ENDS were more often used to quit smoking by students (OR = 2.05, 95% CI = 1.10-3.82), and were less likely to be used by those aged 65 or older (OR = 0.30, 95% CI = 0.15-0.61). No significant differences were found according to sex, social class, marital status or type of community. CONCLUSIONS: In 2012, ever-use of ENDS was low in the European population in general. However, younger people or those with a high education used ENDS more frequently. These results indicate a need for more appropriate product information targeted at these groups. IMPLICATIONS: This study shows that in the European Union in 2012, regular use of ENDS was rare, especially among nonsmokers. Only age and education were strongly associated with ENDS use. The increased prevalence of ever-use among the younger age groups is relevant, as in this age group smoking habits are established. The higher ever-use of ENDS among younger and higher educated people found in this study indicates a need to target appropriate product information, stressing that ENDS use does not imply zero harm.

L-cysteine suppresses ghrelin and reduces appetite in rodents and humans.

BACKGROUND: High-protein diets promote weight loss and subsequent weight maintenance, but are difficult to adhere to. The mechanisms by which protein exerts these effects remain unclear. However, the amino acids produced by protein digestion may have a role in driving protein-induced satiety. METHODS: We tested the effects of a range of amino acids on food intake in rodents and identified l-cysteine as the most anorexigenic. Using rodents we further studied the effect of l-cysteine on food intake, behaviour and energy expenditure. We proceeded to investigate its effect on neuronal activation in the hypothalamus and brainstem before investigating its effect on gastric emptying and gut hormone release. The effect of l-cysteine on appetite scores and gut hormone release was then investigated in humans. RESULTS: l-Cysteine dose-dependently decreased food intake in both rats and mice following oral gavage and intraperitoneal administration. This effect did not appear to be secondary to behavioural or aversive side effects. l-Cysteine increased neuronal activation in the area postrema and delayed gastric emptying. It suppressed plasma acyl ghrelin levels and did not reduce food intake in transgenic ghrelin-overexpressing mice. Repeated l-cysteine administration decreased food intake in rats and obese mice. l-Cysteine reduced hunger and plasma acyl ghrelin levels in humans. CONCLUSIONS: Further work is required to determine the chronic effect of l-cysteine in rodents and humans on appetite and body weight, and whether l-cysteine contributes towards protein-induced satiety.

SPRED1 germline mutations caused a neurofibromatosis type 1 overlapping phenotype.

OBJECTIVE: Germline loss-of-function mutations in the SPRED1 gene have recently been identified in patients fulfilling the National Institutes of Health (NIH) diagnostic criteria for neurofibromatosis type 1 (NF1) but with no NF1 (neurofibromin 1) mutation found, suggesting a neurofibromatosis type 1-like syndrome. METHODS: 61 index cases with NF1 clinical diagnosis but no identifiable NF1 mutation were screened for SPRED1 mutation. RESULTS: We describe one known SPRED1 mutation (c.190C>T leading to p.Arg64Stop) and four novel mutations (c.637C>T leading to p.Gln213Stop, c.2T>C leading to p.Met1Thr, c.46C>T leading to p.Arg16Stop, and c.1048_1060del leading to p.Gly350fs) in five French families. Their NF1-like phenotype was characterised by a high prevalence of café-au-lait spots, freckling, learning disability, and an absence of neurofibromas and Lisch nodules in agreement with the original description. However, we did not observe Noonan-like dysmorphy. It is noteworthy that one patient with the p.Arg16Stop mutation developed a monoblastic acute leukaemia. CONCLUSIONS: In our series, SPRED1 mutations occurred with a prevalence of 0.5% in NF1 patients and in 5% of NF1 patients displaying an NF1-like phenotype. SPRED1 mutated patients did not display any specific dermatologic features that were not present in NF1 patients, except for the absence of neurofibromas that seem to be a specific clinical feature of NF1. The exact phenotypic spectrum and the putative complications of this NF1 overlapping syndrome, in particular haematological malignancies, remain to be further characterised. NIH diagnostic criteria for NF1 must be revised in view of this newly characterised Legius syndrome in order to establish a specific genetic counselling.

Acrylamide quenching of apo- and holo-alpha-lactalbumin in guanidine hydrochloride.

We have examined the fluorescence properties and acrylamide quenching of calcium-loaded (holo) and calcium-depleted (apo) alpha-lactalbumin (alpha-LA) as a function of guanidine hydrochloride (GDN/HCl) concentration. The spectral changes accompanying increasing GDN/HCl are consistent with protein unfolding and a release of internal fluorescence quenching, which occurs among the three tryptophan residues located in the region of the so-called "tertiary fold." Values for the intrinsic fluorescence emission, the wavelength maximum of the emission, the Stern/Volmer dynamic quench constant, and the static quench constant are consistent with a significant stabilization effect by calcium against protein unfolding. The dynamic quench constant of apo-alpha-LA increases fourfold to its maximum, in the transition from the native state to protein in 1.5 M GDN/HCl. The dynamic quench constant for holo-alpha-LA remains unchanged until exposed to 2.5 M GDN/HCl, but increases by threefold with addition denaturant to 4 M GDN/HCl. The static quench constant of the apo-protein in the native solvent, approximately 0.2 M(-1), declines to zero in 1 M denaturant, where the molten globule folding intermediate is most populated. A more protracted denaturant-dependent decline in the static quench constant occurs for the holo-protein. Sharp increase in the static quenching occurs for apo-alpha-LA and holo-alpha-LA above 1.5 M GDN/HCl and 3.5 M GDN/HCl, respectively. The results for apo-alpha-LA in dilute GDN/HCl suggest that acrylamide can penetrate the protein molecule (as judged by the collision quenching) but is unable to form a stable complex within the quenching domain for the tryptophans (as judged by the absence of the static quench constant). It seems reasonable to suggest that the protein folding intermediate which occurs in dilute denaturant represents a structure in which the tryptophans are, on average, more accessible to collisional quenching but sufficiently compact to prevent formation of a stable, dark equilibrium complex with acrylamide.

Comparison of proliferation and growth of human keratinocytes on plasma copolymers of acrylic acid/1,7-octadiene and self-assembled monolayers.

Human keratinocytes were cultured on plasma copolymers (PCPs), self-assembled monolayers (SAMs), and tissue culture poly(styrene) (TCPS). Plasma copolymerization was used to deposit films with controlled concentrations of carboxylic acid functional groups (<5%). Human keratinocytes were cultured onto these PCP surfaces, TCPS, and collagen I. A hydrocarbon plasma polymer surface was used as the negative control. Keratinocyte attachment was measured at 24 h and cell proliferation and growth at 3 and 7 days using optical microscopy and DNA concentrations. The PCP surfaces were compared with two SAM systems comprising pure acid and pure hydrocarbon functionalities, and pure gold was used as a control surface. PCP surfaces containing carboxylic acid functionalities promoted keratinocyte attachment. The level of attachment on these surfaces was comparable to that seen on collagen I, a preferred substratum for the culturing of keratinocytes. After several days in culture the cells were well attached and proliferative, forming confluent sheets of keratinocytes. This result was confirmed by DNA assays that suggested the acid PCP surfaces were performing as well as collagen I. Keratinocytes attached well to gold and acid-terminated SAMs but attached poorly to methyl-terminated SAMs. The acid functionality also promoted proliferation and growth of keratinocytes after several days in culture. DNA assays revealed that keratinocyte growth on the acid surface was higher than on collagen I.

Purification, characterization, and hydrodynamic properties of arginine kinase from gulf shrimp (Penaeus aztecus).

Arginine kinase from the tail muscle of the Gulf shrimp (Penaeus aztecus) was purified to apparent homogeneity, using a rapid, high-yield method. The protein exhibits a molecular weight of 40 kDa according to the methods of gel filtration and gel electrophoresis in sodium dodecyl sulfate, also indicating that arginine kinase from shrimp is a monomer. The amino acid content of arginine kinase from shrimp is similar to arginine kinases from several species and to creatine kinase from rabbit muscle. Arginine kinase derivatized at the reactive sulfhydryl with 2-(4'-(iodoacetamido)anilino)naphthalene-6-sulfonic acid exhibits significant changes in fluorescence anisotropy only in the presence of the guanidino substrate and the so-called "dead-end complex" containing arginine + MgADP. Several compounds structurally similar to arginine, e.g., ornithine do not interact with arginine kinase, suggesting a narrow specificity for substrate binding. The most suitable description of the decay of the fluorescence of arginine kinase derivatized with 5-[(((acetyl)-amino)ethyl)amino]naphthalene-1-sulfonate (AEDANS-AK), from among discrete and distributed models, is a triple exponential discrete decay. The presence of the dead-end complex only marginally increases the rate of decay, but significantly shifts the magnitude of the preexponentials (amplitudes) between the two major decay components. One interpretation of these results is that multiple conformational isomers may occur, in which the relative concentrations are dependent upon the presence of the dead-end complex. Measurement of the time-dependent anisotropy decay of AEDANS-AK reveals a two-term decay law with rotational correlation times of 0.88 and 15.2 ns. The slower component is close to the theoretical value of 16.7 ns for an isotropic rotator of the molecular mass of arginine kinase. This finding suggests that the overall conformation of arginine kinase may differ considerably from the prolate ellipsoidal subunits of the functionally analogous creatine kinase.

Decreased Carbon and Nutrient Input to Boreal Lakes from Particulate Organic Matter Following Riparian Clear-Cutting

The plankton communities of oligotrophic Canadian Shield lakes are strongly regulated by the allochthonous supply of total phosphorus (TP) and dissolved organic carbon (DOC), a proportion of both of which originate from particulate organic matter. Although decreased inputs of allochthonous leaf litter have been documented for small streams whose riparian forests have been removed, no such data exist for boreal lakes. Through estimates of airborne litter input from forested and clear-cut shorelines and laboratory measurements of concentrations released from leaf leachate, we determined that riparian deforestation resulted in reductions of DOC from 17.8 to 0.4 g/m shoreline/yr and of TP from 2.9 to 0.3 g/m shoreline/yr. Previous predictive models indicate that such reductions may be substantial enough to decrease basic metabolic processes of lake plankton communities by as much as 9% in primary production and 17% in respiration.