EGFR Suppression Inhibits the Sphere Formation of MCF7 Cells Overexpressing EGFR.

The epidermal growth factor receptor (EGFR) is an oncogenic tyrosine kinase that is involved in tumor initiation and progression, making EGFR inhibitors and monoclonal antibodies to this receptor essential for anti-tumor therapy. We have previously shown that EGFR transgene expression in the human breast adenocarcinoma cell line MCF7 (MCF7-EGFR) stimulates the 3D spheroid-like growth. The primary focus of our present work was to investigate whether EGFR inhibition could affect the assembly of spheroids or lead to the destruction of pre-existing spheroids. We compared the effects of anti-EGFR siRNA, the anti-EGFR monoclonal antibody cetuximab, and the tyrosine kinase inhibitor AG1478 on dissociated and spheroid MCF7-EGFR cells. MCF7-EGFR cells were found to have a 2.5-fold higher sensitivity towards the cytotoxic effects of cetuximab and AG1478 compared with the parental MCF7 cell line. The suppression of EGFR mRNA with siRNA was found to reduce the sphere formation, whereas treating the pre-existing spheroids had no such effect. Treatment of dissociated spheroids with cetuximab and AG1478 was also found to inhibit the MCF7-EGFR sphere formation. We suggest that EGFR expression is important, at least, during the spheroid formation stage. The transition of a MCF7wt adherent cell culture to MCF7-EGFR spheroids was accompanied by a considerable increase in N-cadherin adhesion proteins. The level of N-cadherin decreased when MCF7-EGFR cells were treated with siRNA and cetuximab. Thus, we have demonstrated that N-cadherin is involved in the EGFR-dependent formation of MCF7-EGFR spheroids. Accordingly, MCF7-EGFR spheroids can be considered a suitable model for studying aggressive hormone-positive breast tumors.

Immunogenic Cell Death in Cancer Therapy.

Apoptosis plays a crucial role in chemotherapy-induced cell death. The conventional theory holding that apoptosis needs to be immunologically silent has recently been revised, and the concept of immunogenic cell death (ICD) has been proposed. This review describes the main features of ICD induction. These ICD markers are important for the effectiveness of anticancer therapy, as well as for basic research into cell death regulation. The mechanism of the "vaccination effect" of dying cancer cells undergoing ICD has been fully described, including the activation of specific antitumor response after re-challenge by the same living tumor cells. This review also discusses the whole set of molecular events attributing cell death to immunogenic type: the exposure of calreticulin and the heat shock protein HSP70 to the outer surface of the cell membrane and the release of the nuclear protein HMGB1 and ATP into the extracellular space. ICD inducers of various nature (chemotherapy drugs, cytotoxic proteins, and oncolytic viruses), as well as physical methods, are classified in the current review.

COMPREHENSIVE RADIOLOGICAL AND HYGIENIC MONITORING OF PARTICULAR SETTLEMENTS OF KYIV REGION IN 2019. / KOMPLEKSNYI RADIATsIINO/GIGIIeNIChNYI MONITORYNG OKREMYKh NASELENYKh PUNKTIV KYÏVS'KOÏ OBLASTI U 2019 ROTsI.

OBJECTIVE: to identificate the main factors and assess their impact on the formation of radiation doses to the population of radioactively contaminated areas of Kyiv region at the current stage of the accident based on complexradiation and hygienic monitoring in the reference settlements in 2019. MATERIALS AND METHODS: Comprehensive radiological and hygienic monitoring was carried out in eight settlementsof Kyiv region - villages of Ragivka, Lygovyky, Mar'yanivka, Zelena Poliana of Polis'kyi district and villages ofHornostaipil, Dytiatky , Pisky, Karpylivka of Ivankiv district. The content of incorporated 137Cs was determined withdirect measurement on whole body counters (WBC) samples of basic foodstuffs were collected to determine the content of radionuclides 90Sr and 137Cs, residents were interviewed about the levels of consumption of these products,and work was performed to estimate external radiation doses. Mathematical, dosimetric, radiochemical methods areused in the work. RESULTS: There was a further decrease in annual doses of internal radiation in the surveyed settlements in 1.3 times, bothin Polis'kyi district (0.041 mSv · year-1 in 2016, 0.030 mSv · year-1 in 2019) and in Ivankiv district (0.023 mSv · year-1in 2016, 0.018 mSv · year-1 in 2019). It is possible to state a slowdown in the reduction of radiation doses comparedto previous years: from 2010 to 2013, the annual doses of internal radiation in the surveyed settlements decreasedby 1.8-2.4 times, from 2013 to 2016 - by 2.3-3.6 times. The content of 137Cs and 90Sr in milk and potatoes in theinspected settlements is lower than the permissible level of the Hygienic Standard HS 6.6.1.1-130-2006 and the useof these foods can not significantly affect the formation of the internal radiation dose. The content of 90Sr in milksamples in the settlements of Ivankiv district is in the range of 2.1-9.9 Bq · kg-1 (in 2016: 1.3-7.4 Bq · kg-1), whichdoes not exceed the permissible level of 20 Bq · kg-1, but due to the dynamics needs further monitoring. The content of 137Cs in samples of dried mushrooms collected from residents of Kyiv region in 2019, as in previous years, issignificantly (up to 100 times) higher than permissible level, and has a high uncertainty - from 1.4 kBq · kg-1 to223.7 kBq · kg-1. CONCLUSIONS: It is established that the annual effective radiation doses of the population in the surveyed settlements in the current year are formed due to internal radiation doses that do not exceed 0.46 mSv · year-1 in Ivankivdistrict and 0.51 mSv · year-1 in Polis'kyi district, which below the RCT criterion 1 mSv · year-1. The main factor that forms the dose of internal radiation of the residents of the surveyed state of emergency of Kyiv region is the intake of 137Cs in the body with forest products, primarily mushrooms.

Lipid monolayer as a simple model membrane for comparative assessment of the photodynamic therapy photosensitizer efficiency via macroscopic measurements.

Cellular membrane is one of the main targets of photodynamic therapy. Its high complexity has led to the study of the efficiency of photosensitizers on artificial lipid systems mimicking membranes. However, the preliminary analysis of this efficiency remains limited due to difficulty of the model construction and/or implementation of the required measurement techniques. Hereby, we propose a quite simple way for the rapid comparative assessment of novel photosensitizers in terms of membrane photodegradation, based on simple and fast measurements, such as wetting angle and surface plasmon resonance spectroscopy. As a proof of concept, we applied this methodology to two bacteriopurpurinimide derivatives. We have shown in particular that such complementary techniques can be employed not only for the multiparametric monitoring of the kinetics of the photodegradation, but also for the comparison of the damaging efficiency of the photosensitizers in the lipid structures as well.

EVALUATION OF MAIN FOODSTUFFS CONSUMPTION BY RESIDENTS OF PARTICULAR SETTLEMENTS ON RADIOLOGICALLY CONTAMINATED TERRITORIES OF UKRAINE. / OTsINKA SPOZhYVANNIa OSNOVNYKh KhARChOVYKh PRODUKTIV MEShKANTsIaMY OKREMYKh NASELENYKh PUNKTIV RADIOAKTYVNO ZABRUDNENYKh TERYTORIY̆ UKRAÏNY.

OBJECTIVE: evaluation of main foodstuffs consumption levels of residents in particular settlements on radiological- ly contaminated territories of Kyiv, Rivne and Zhytomyr regions and determination of the proportion of local house- holds products to goods purchased in the trade network in the daily ration. MATERIALS AND METHODS: The research was conducted in 22 settlements of Kyiv, Rivne, Zhytomyr regions. For the study, the questionnaires were written for adults and children, which included 47 questions in 5 content blocks regarding the questionnaire data of the interviewed person; peculiarities of household management; levels of food consumption grown in local households and separately purchased in the trade network; levels of local wildlife products consumption; and the fifth - regarding the possession of information on radiation, received an individual dose of radiation from the «Chornobyl component¼, protective preventive measures. In total 539 people were inter- viewed, including 359 adults and 180 children aged 1 to 18 years. Information about children under 14 years of age was provided by their parents. Mathematical, statistical methods were used. RESULTS: According to the results of the survey, it can be stated that the main foodstuffs of residents of the sur- veyed settlements are milk and dairy products, potatoes and root crops of local cultivation, bread and bakery products purchased in the trade network. The analysis of the structure and dynamics of the diet of the popula- tion of the surveyed settlements showed a significant decrease in the consumption levels of basic food products, primarily purchased through the trade network, due to a decline in purchasing power of the population in recent years. CONCLUSIONS: The diet of the residents of the surveyed settlements consists mainly of products produced in private or local households. Fewer people use wildlife products - wildfowl, fish from local water bodies, fresh and canned wild berries, and fresh and dried mushrooms, but due to their significant 137Cs contamination, even small amounts of these products can result in a significant dose of radiation.

Difficulty adaptation in a competitive arm rehabilitation game using real-time control of arm electromyogram and respiration.

Rehabilitation robots are often combined with serious games that motivate patients and keep them exercising at high intensities. A promising type of game are competitive rehabilitation games, but few difficulty adaptation algorithms have been presented for them. This paper thus presents the adaptation of difficulty in a competitive arm rehabilitation game based on two physiological signals: respiration and electromyography of the posterior deltoid. It consists of three smaller studies: an open-loop respiration study, a closed-loop respiration study (where a controller attempts to maintain respiration rate at preset levels), and a closed-loop electromyogram study (where a controller attempts to keep the electromyogram at preset levels). The studies control two difficulty parameters based on the physiological responses of one of the two exercising participants, though the ultimate goal is to control the physiological responses of both participants. Furthermore, all three studies are done with unimpaired participants. The closed-loop controllers achieved high correlation coefficients between desired and measured levels of respiration rate (r = 0.83) and electromyogram (r = 0.89), demonstrating that it is possible to control the physiological responses of unimpaired participants in a competitive arm rehabilitation game, thus controlling their level of workload and exercise intensity. In the future, the proposed method will be tested with patients undergoing rehabilitation.

Airflow limitation is accompanied by diaphragm dysfunction.

Chronic airflow limitation, caused by chronic obstructive pulmonary disease (COPD) or by asthma, is believed to change the shape and the position of the diaphragm due to an increase in lung volume. We have made a comparison of magnetic resonance imaging (MRI) of diaphragm in supine position with pulmonary functions, respiratory muscle function and exercise tolerance. We have studied the differences between patients with COPD, patients with asthma, and healthy subjects. Most interestingly we found the lung hyperinflation leads to the changes in diaphragmatic excursions during the breathing cycle, seen in the differences between the maximal expiratory diaphragm position (DPex) in patients with COPD and control group (p=0.0016). The magnitude of the diaphragmatic dysfunction was significantly related to the airflow limitation expressed by the ratio of forced expiratory volume in 1 s to slow vital capacity (FEV(1)/SVC), (%, p=0.0007); to the lung hyperinflation expressed as the ratio of the residual volume to total lung capacity (RV/TLC), (%, p=0.0018) and the extent of tidal volume constrain expressed as maximal tidal volume (V(Tmax)), ([l], p=0.0002); and the ratio of tidal volume to slow vital capacity (V(T)/SVC), (p=0.0038) during submaximal exercise. These results suggest that diaphragmatic movement fails to contribute sufficiently to the change in lung volume in emphysema. Tests of respiratory muscle function were related to the position of the diaphragm in deep expiration, e.g. neuromuscular coupling (P(0.1)/V(T)) (p=0.0232). The results have shown that the lung volumes determine the position of the diaphragm and function of the respiratory muscles. Chronic airflow limitation seems to change the position of the diaphragm, which thereafter influences inspiratory muscle function and exercise tolerance. There is an apparent relationship between the position of the diaphragm and the pulmonary functions and exercise tolerance.

Social capital and physical activity among Croatian high school students.

OBJECTIVE: To examine factors associated with regular physical activity in Croatian adolescents. STUDY DESIGN: A cross-sectional survey among high school students was carried out in the 2013/14 school year. METHOD: A survey was conducted among 33 high schools in Zagreb City, Croatia. Participants were students aged 17-18 years. The dependent variables were regular moderate to vigorous physical activity (MVPA) and overall physical activity measured by the short version of International Physical Activity Questionnaire and defined as 60 min or more of daily physical activity. The independent variables included family, neighborhood, and high school social capital. Other study covariates included: socio-economic status, self-rated health, psychological distress and nutritional status. The associations between physical activity and social capital variables were assessed separately for boys and girls through multiple logistic regression and inverse probability weighting in order to correct for missing data bias. RESULTS: A total of 1689 boys and 1739 girls responded to the survey. A higher percentage of boys reported performing regular vigorous and moderate physical activity (59.4%) and overall physical activity (83.4%), comparing with the girls (35.4% and 70%, respectively). For boys, high family social capital and high informal social control were associated with increased odds of regular MVPA (1.49, 95%CI: 1.18 - 1.90 and 1.26, 95%CI: 1.02 - 1.56, respectively), compared to those with low social capital. For girls, high informal social control was associated with regular overall physical activity (OR 1.38, 95% CI: 1.09 - 1.76). CONCLUSION: High social capital is associated with regular MVPA in boys and regular overall activity in girls. Intervention and policies that leverage community social capital might serve as an avenue for promotion of physical activity in youth.

Multifractal analysis for grading complex fractionated electrograms in atrial fibrillation.

Complex fractionated atrial electrograms provide an important tool for identifying arrhythmogenic substrates that can be used to guide catheter ablation for atrial fibrillation (AF). However, fractionation is a phenomenon that remains unclear. This paper aims to evaluate the multifractal properties of electrograms in AF in order to propose a method based on multifractal analysis able to discriminate between different levels of fractionation. We introduce a new method, the h-fluctuation index (hFI), where h is the generalised Hurst exponent, to extract information from the shape of the multifractal spectrum. Two multifractal frameworks are evaluated: multifractal detrended fluctuation analysis and wavelet transform modulus maxima. hFI is exemplified through its application in synthetic signals, and it is evaluated in a database of electrograms labeled on the basis of four degrees of fractionation. We compare the performance of hFI with other indexes, and find that hFI outperforms them. The results of the study provide evidence that multifractal analysis is useful for studying fractionation phenomena in AF electrograms, and indicate that hFI can be proposed as a tool for grade fractionation associated with the detection of target sites for ablation in AF.

Fractionated electrograms and rotors detection in chronic atrial fibrillation using model-based clustering.

The identification of atrial fibrillation (AF) substrates is needed to improve ablation therapy guided by electrograms, although mechanisms that sustain AF are not fully understood. Detection of complex fractionated atrial electrograms (CFAE) is used for this purpose. Nonetheless, efficacy of this method is inadequate in the case of chronic AF. Recent hypothesis proposes the rotors as fibrillatory substrate. Novel approaches seek to relate CFAE with rotor; nevertheless, such methods are not able to identify the associated substrate. Furthermore, the patterns that characterize CFAE generated by rotors remain unknown. Thus, tracking of rotors is an unsolved issue. In this paper, we propose a non-supervised method to find patterns associated with fibrillatory substrates in chronic AF. We extracted two features based on local activation wave detection and one feature based on non-linear dynamics. Gaussian mixture model-based clustering was used to discriminate CFAE patterns. Resulting clusters are visualized in an electroanatomic map. We assessed the proposed method in a real database labeled according to the level of fractionation and in a simulated episode of chronic AF in which a rotor was detected. Our results indicate that the method proposed can separate different levels of fractionation in CFAE, and provide evidence that clustering can be used to locate the vortex of the rotors. Provided approach can support ablation therapy procedures by means of CFAE patterns discrimination.

Feature selection for discrimination of fractionation levels in atrial electrograms.

Radiofrequency catheter ablation of atrial fibrillation (AF) guided by complex fractionated atrial electrograms (CFAE) is associated with a high AF termination rate in paroxysmal AF, but not in persistent. CFAE does not always identify favorable sites for persistent AF ablation. Studies suggest that only high fractionation level should be used as a target site for ablation. Nonetheless, there are not a standardized criterion to defined fractionation levels. Therefore, a better characterization of the signal is required providing a set of more powerful features that should be extracted from CFAE. Due to the apparent difference among fractionation classes in terms of their stochastic variability, we test time-domain and time-frequency based feature extraction approaches. Also, we carried out the symmetrical uncertainty-based feature selection to determine the most relevant features which improve discrimination of fractionation levels. Obtained results on a tested real electrogram database show that most relevant features in time-domain are related with time intervals and not with amplitudes. Nonetheless, time-frequency features obtained more information from the signal and this representation is likely a better suitable discriminating approach, particularly to detect high fractionated electrograms with a sensitivity and specificity of 83.0% and 93.6%, respectively.

Analysis of actigraph parameters for relapse prediction in bipolar disorder: a feasibility study.

The paper presents a framework for early identification of prodromal syndromes od mania or depression in bipolar disorder. The framework may mitigate relapses and improve patient functioning. The methodology consists of long-term actigraphy monitoring and simplified self-assessment tool to determine manic or depression events. Eight patients were involved in the feasibility study, spanning period of 150 months, resulting in 17 relapses and 3 hospitalizations in total. We concluded that the most promising parameter extracted from actigraphy recording is a circadian rhythm's interdaily stability. Using developed trend analysis applied on interdaily stability parameter, we achieved sensitivity and specificity about 65, resp. 68. We hypothesized that this performance is both mainly due to missing values in data and due to small amount of relapses.

Serum preadipocyte factor-1 concentrations in females with obesity and type 2 diabetes mellitus: the influence of very low calorie diet, acute hyperinsulinemia, and fenofibrate treatment.

Appropriate differentiation capacity of adipose tissue significantly affects its ability to store lipids and to protect nonadipose tissues against lipid spillover and development of insulin resistance. Preadipocyte factor-1 (Pref-1) is an important negative regulator of preadipocyte differentiation. The aim of our study was to explore the changes in circulating Pref-1 concentrations in female subjects with obesity (OB) (n=19), females with obesity and type 2 diabetes mellitus (T2DM) (n=22), and sex- and age-matched healthy control subjects (C) (n=22), and to study its modulation by very low calorie diet (VLCD), acute hyperinsulinemia during isoglycemic-hyperinsulinemic clamp, and 3 months' treatment with PPAR-α agonist fenofibrate. At baseline, serum Pref-1 concentrations were significantly higher in patients with T2DM compared to control group, while only nonsignificant trend towards higher levels was observed in OB group. 3 weeks of VLCD decreased Pref-1 levels in both OB and T2DM group, whereas 3 months of fenofibrate treatment had no significant effect. Hyperinsulinemia during the clamp significantly suppressed Pref-1 levels in both C and T2DM subjects and this suppression was unaffected by fenofibrate treatment. In a combined population of all groups, circulating Pref-1 levels correlated positively with insulin, leptin and glucose levels and HOMA (homeostasis model assessment) index. We conclude that elevated Pref-1 concentrations in T2DM subjects may contribute to impaired adipose tissue differentiation capacity associated with insulin resistance in obese patients with T2DM. The decrease of Pref-1 levels after VLCD may be involved in the improvement of metabolic status and the amelioration of insulin resistance in T2DM patients.

Use of the Internet for home testing for Chlamydia trachomatis in Sweden: who are the users?

Sweden was the first country to introduce online Chlamydia trachomatis testing for both men and women and this article provides information about the user characteristics and which risk groups are reached with this method. During the years 2005-2007 a questionnaire was administered with a response rate of 86% (n = 6025) (62.5% women, 37.5% men). Over 60% of respondents were aged below 26 years and single. The average years of education for men and women was 14 (range 9.0-26.0). The mean Internet usage time was 22.4 hours/week among men and 15.5 hours/week among women. Only 22% men and 34% women had tested themselves for C. trachomatis at clinics previously. Respondents reported a higher frequency of previous sexually transmitted infections (STIs) compared with other Internet users (i.e. C. trachomatis: men 19%, women 24%). Eighty percent of online test users had engaged in sex with ≥ 2 partners without a condom during the previous year. Online C. trachomatis test users are mostly young people with high sexual risk behaviour.

Development of gait segmentation methods for wearable foot pressure sensors.

We present an automated segmentation method based on the analysis of plantar pressure signals recorded from two synchronized wireless foot insoles. Given the strict limits on computational power and power consumption typical of wearable electronic components, our aim is to investigate the capability of a Hidden Markov Model machine-learning method, to detect gait phases with different levels of complexity in the processing of the wearable pressure sensors signals. Therefore three different datasets are developed: raw voltage values, calibrated sensor signals and a calibrated estimation of total ground reaction force and position of the plantar center of pressure. The method is tested on a pool of 5 healthy subjects, through a leave-one-out cross validation. The results show high classification performances achieved using estimated biomechanical variables, being on average the 96%. Calibrated signals and raw voltage values show higher delays and dispersions in phase transition detection, suggesting a lower reliability for online applications.

USA study of sex toy use by HIV-positive men who have sex with other men: implications for sexual health.

HIV/AIDS disproportionately impacts men who have sex with men (MSM) in the USA. Most existing literature on MSM with HIV focuses on transmission risk, but does not acknowledge health-promoting sexual behaviours men may undertake. This study examined sex toy use within this population to describe the extent to which using toys is incorporated into their sexual repertoires as a risk reduction practice. Data regarding sociodemographics, sexual/health-related behaviours and sex toy use were collected from 2275 MSM using an online survey. Most participants reported being sexually active (88.5%), and the majority (70.2%) of participants reported sex toy use within the previous year. Sex toy users were more likely to be white, in sexual relationships with others, and reported higher levels of sexual satisfaction. Given that sex toy use is common among this population, room for discussion exists about sex toys as tools to enhance pleasure and reduce HIV/sexually transmitted infection (STI) transmission.

Measuring body temperature time series regularity using Approximate Entropy and Sample Entropy.

Approximate Entropy (ApEn) and Sample Entropy (SampEn) have proven to be a valuable analyzing tool for a number of physiological signals. However, the characterization of these metrics is still lacking. We applied ApEn and SampEn to body temperature time series recorded from patients in critical state. This study was aimed at finding the optimal analytical configuration to best distinguish between survivor and non-survivor records, and at gaining additional insight into the characterization of such tools. A statistical analysis of the results was conducted to support the parameter and metric selection criteria for this type of physiological signal.

Discrimination of endocardial electrogram disorganization using a signal regularity analysis.

Measures from the theory of nonlinear dynamics were applied on complex fractionated atrial electrograms (CFAEs) in order to characterize their physiological dynamic behavior. The results were obtained considering 113 short term atrial electrograms (A-EGMs) which were annotated by three experts into four classes of fractionation according to A-EGMs signal regularity. The following measures were applied on A-EGM signals: General Correlation Dimension, Approximate Entropy, Detrended Fluctuation Analysis, Lempel-Ziv Complexity, and Katz-Sevcik, Variance and Box Counting Fractal Dimension. Assessment of disorganization was evaluated by a Kruskal Wallis statistical test. Except Detrended Fluctuation Analysis and Variance Fractal Dimension, the CFAE disorganization was found statistically significant even for low significant level alpha = 0.001. Moreover, the increasing complexity of A-EGM signals was reflected by higher values of General Correlation Dimension of order 1 and Approximate Entropy.

Diabetes management in OLDES project.

EU project OLDES (Older People's e-services at home) develops easy to use and low cost ICT platform in order to offer a better quality of life to elderly people directly in their homes through innovative systems of tele-accompany, tele-assistance and tele-medicine. The elderly are able to access the services and send relevant medical data from their home by being connected to the central server via a low cost PC which is based on Negroponte paradigm. The OLDES platform interface uses television screens controlled through a remote control customized for the elderly. The feasibility of OLDES project is evaluated by the pilot study concentrating on compensation of diabetic patients. Compensation of diabetes is achieved by monitoring glucose glycemia level, blood pressure and weight. Moreover, the patient feeds into OLDES system daily consumption of food using interactive food scales and obtains advice if necessary.

[Red-breasted goose colonies on the Taimyr Peninsula: factors responsible for the proximity of goose nests to nests of peregrine falcons, rough-legged buzzards, and snowy owls].

Red-breasted goose colonies have been studied near Medusa Bay (73 degrees 21' N, 80 degrees 32' E), on the northwestern Taimyr Peninsula, and along the Agapa River (70 degrees 11' N, 86 degrees 15' E) down to its mouth (70 degrees 26' N, 89 degrees 13' E), in the central Taimyr Peninsula. Red-breasted geese nesting near peregrine falcons are protected by the falcons from arctic foxes; however, they are sometimes attacked by the falcons themselves. In the colonies near peregrine falcon nests, the vast majority of goose nests were situated no farther than 100 m from the falcon nest. When food is abundant, falcons protect a larger area around their nest. The distance between the falcon nest and the surrounding goose nests is inversely related to the falcon's activity. In years of higher falcon activity, falcons prevent red-breasted geese from nesting as close to their nest as in years of lower falcon activity. Additional stimuli are required for red-breasted geese to form colonies near rough-legged buzzard nests. The distance between snowy owl nests and red-breasted goose nests was smaller when arctic foxes were abundant than when they were scarce.