Assessment of the effects of sex, age, and rearing condition on ultrasonic vocalizations elicited by pups during the maternal potentiation paradigm in C57BL/6J mice.

Isolation-induced ultrasonic vocalizations (USVs) are important to elicit parental retrieval. This behavior is critical for the animal's survival and can be altered in models of developmental disorders. The potentiation of vocalizations in response to reunion with the dam, also called maternal potentiation, has been extensively studied in rats. However, the assessment of this paradigm in mice is scarce. In rats, the potentiation of vocalizations is dependent on rearing conditions. Since mice are the main species used for genetic models of diseases, we aimed to investigate how different factors such as age, sex, and rearing conditions can affect the potentiation of vocalizations in the maternal potentiation paradigm in mice. We carried out experiments using biparental (dam and sire) or uniparental rearing (dam). Pups were tested on postnatal days (PD) 9 or 12. Pups showed increased potentiation in both sexes at PD9 with uniparental rearing. Both rearing conditions and ages changed the repertoire from the first to the second isolation. Spectral parameters were affected by sex, rearing condition and reunion at PD9. At PD12, only duration was altered by reunion. We conclude that the performance of the pups in the maternal potentiation paradigm is dependent on age, sex, and rearing condition.

Locally delivered GLP-1 analogues liraglutide and exenatide enhance microvascular perfusion in individuals with and without type 2 diabetes.

AIMS/HYPOTHESIS: Glucagon-like peptide-1 (GLP-1) analogues reduce the risk of macrovascular disease in diabetes; however, little is known about their microvascular effects. This research examined the microvascular actions of the GLP-1 analogues liraglutide and exenatide in individuals with and without type 2 diabetes (study 1). It also explored the involvement of the GLP-1 receptor (study 2) and the nitric oxide pathway in mediating the microvascular effects of the analogues. METHODS: Trial design: Studies 1 and 2 had a randomised, controlled, double-blind study design. Study 1 participants, intervention and methods: three participant groups were recruited: individuals with well-controlled type 2 diabetes, and obese and lean individuals without diabetes (21 participants per group). Liraglutide (0.06 mg), exenatide (0.5 µg) and saline (154 mmol/l NaCl; 0.9%) control were microinjected into separate sites in the dermis (forearm) in a randomised order, blinded to operator and participant. Skin microvascular perfusion was assessed by laser Doppler perfusion imaging. Outcomes were stabilised response (mean skin perfusion between 7.5 and 10 min post microinjection) and total response (AUC, normalised for baseline perfusion). Perfusion response to GLP-1 analogues was compared with saline within each group as well as between groups. Study 2 participants, intervention and methods: in healthy individuals (N = 16), liraglutide (0.06 mg) and saline microinjected sites were pretreated with saline or the GLP-1 receptor blocker, exendin-(9,39), in a randomised order, blinded to participant and operator. Outcomes were as above (stabilised response and total perfusion response). Perfusion response to liraglutide was compared between the saline and the exendin-(9,39) pretreated sites. In vitro study: the effects of liraglutide and exenatide on nitrate levels and endothelial nitric oxide synthase phosphorylation (activation) were examined using human microvascular endothelial cells. RESULTS: Study 1 results: both analogues increased skin perfusion (stabilised response and total response) in all groups (n = 21 per group, p < 0.001), with the microvascular responses similar across groups (p ≥ 0.389). Study 2 results: liraglutide response (stabilised response and total response) was not influenced by pretreatment with exendin-(9,39) (70 nmol/l) (N = 15, one dataset excluded) (p ≥ 0.609). Liraglutide and exenatide increased nitrate production and endothelial nitric oxide synthase (eNOS) phosphorylation (p ≤ 0.020). CONCLUSIONS/INTERPRETATION: Liraglutide and exenatide increased skin microvascular perfusion in individuals with and without well-controlled diabetes, potentially mediated, at least in part, by NO. TRIAL REGISTRATION: ClinicalTrials.gov NCT01677104. FUNDING: This work was supported by Diabetes UK (grant numbers: 09/0003955 and 12/0004600 [RW and JM Collins Legacy, Funded Studentship]).

Langerhans Cell Histiocytosis of the Head and Neck: Experience at a Rural Tertiary Referral Center.

OBJECTIVES: Retrospectively analyze head and neck Langerhans Cell Histiocytosis at a rural tertiary referral center and compare results with previously published data. METHODS: Electronic health record review was performed from 2003 to 2019. Patients with biopsy proven LCH with primary head and neck involvement were included. Demographics, presentation, imaging characteristics, treatment modality, delay in diagnosis (DD, ≥60 days), and outcomes were analyzed and reported. RESULTS: Twenty-four patients were included. The most common presenting symptoms were otorrhea (n = 6) and scalp pain or swelling (n = 6). All patients had bony involvement. The most common site was facial or skull lesions (n = 20). Most skull lesions (75%) demonstrated CNS risk. Six patients were treated with primary surgery, 15 with primary chemotherapy, and 3 with surgery plus adjuvant chemotherapy. Nine patients experienced relapse of disease with median time to documented relapse of 11.4 months; all were treated with salvage chemotherapy to achieve complete remission (median follow-up: 72 months). Patients most likely to relapse were those with multisystem disease (5/7, 71.4%), temporal bone lesions (4/7, 57.1%), and DD (7/12, 58.3%). Of the 9 total patients who experienced relapse, 78% had a delay in diagnosis. CONCLUSIONS: LCH is a complex disease process in which diagnosis can be delayed if not considered in the differential. Within the head and neck, the skull, including isolated temporal bone involvement, is the most common site of involvement. Treatment modality does not appear to have an influence on relapse rates. Relapse was more likely to occur in the first year after treatment and close monitoring is required.

The coevolution of toxin and antitoxin genes drives the dynamics of bacterial addiction complexes and intragenomic conflict.

Bacterial genomes commonly contain 'addiction' gene complexes that code for both a toxin and a corresponding antitoxin. As long as both genes are expressed, cells carrying the complex can remain healthy. However, loss of the complex (including segregational loss in daughter cells) can entail death of the cell. We develop a theoretical model to explore a number of evolutionary puzzles posed by toxin-antitoxin (TA) population biology. We first extend earlier results demonstrating that TA complexes can spread on plasmids, as an adaptation to plasmid competition in spatially structured environments, and highlight the role of kin selection. We then considered the emergence of TA complexes on plasmids from previously unlinked toxin and antitoxin genes. We find that one of these traits must offer at least initially a direct advantage in some but not all environments encountered by the evolving plasmid population. Finally, our study predicts non-transitive 'rock-paper-scissors' dynamics to be a feature of intragenomic conflict mediated by TA complexes. Intragenomic conflict could be sufficient to select deleterious genes on chromosomes and helps to explain the previously perplexing observation that many TA genes are found on bacterial chromosomes.

Psychosocial factors associated with use of continuous glucose monitoring.

AIMS: To identify psychosocial factors associated with the use of continuous glucose monitoring by adults with Type 1 diabetes. METHODS: Twenty adult patients (aged 45 +/- 15 years, diabetes duration 25 +/- 19 years, 50% female) followed at our site in the multi-centre Juvenile Diabetes Research Foundation continuous glucose monitoring trial were divided into three groups: Glycated haemoglobin (HbA(1c)) Responders who demonstrated an improvement in glycaemic control with continuous glucose monitoring (baseline HbA(1c)> or = 7.0%, HbA(1c) reduction greater than or equal to 0.5%), Hypoglycaemia Responders (baseline HbA(1c) < 7.0%) who demonstrated decreased time < 3.9 mmol/l while remaining within target HbA(1c), and HbA(1c) Non-Responders (baseline HbA(1c)> or = 7.0%, HbA(1c) reduction less than 0.5%). Subjects participated in semi-structured interviews focusing on their psychosocial experiences with continuous glucose monitoring. RESULTS: Three major themes were identified that differentiated Responders (including both the HbA(1c) and Hypoglycaemia groups) from Non-Responders: (i) coping with frustrations-Responders used self-controlled rather than emotions-based coping when faced with continuous glucose monitoring frustrations; (ii) use of information-Responders used retrospective pattern analysis, not just minute-by-minute data analysis, in glycaemic management; (iii) 'significant other'/spousal involvement-Responders endorsed interest, encouragement and participation by their loved ones. Both Responders and Non-Responders expressed body image concerns when wearing continuous glucose monitoring devices. CONCLUSIONS: This qualitative study points to the importance of coping skills, retrospective review of data, and 'significant other' involvement in the effective use of continuous glucose monitoring. These findings will inform clinical initiatives to improve patient selection and training in the use of this new technology and have served as the basis for development of quantitative surveys to be used in clinical practice.

Anxiety: its role in the history of psychiatric epidemiology.

BACKGROUND: The role played by anxiety in the history of psychiatric epidemiology has not been well recognized. Such lack of understanding retarded the incremental growth of psychiatric research in general populations. It seems useful to look back on this history while deliberations are being carried out about how anxiety will be presented in DSM-V. METHOD: Drawing on the literature and our own research, we examined work that was carried out during and after the Second World War by a Research Branch of the United States War Department, by the Stirling County Study, and by the Midtown Manhattan Study. The differential influences of Meyerian psychobiology and Freudian psychoanalysis are noted. RESULTS: The instruments developed in the early epidemiologic endeavors used questions about nervousness, palpitations, sweating, trembling, shortness of breath, upset stomach, etc. These symptoms are important features of what the clinical literature called 'manifest', 'free-floating' or 'chronic anxiety'. A useful descriptive name is 'autonomic anxiety'. CONCLUSIONS: Although not focusing on specific circumstances as in Panic and Phobic disorders, a non-specific form of autonomic anxiety is a common, disabling and usually chronic disorder that received empirical verification in studies of several community populations. It is suggested that two types of general anxiety may need to be recognized, one dominated by excessive worry and feelings of stress, as in the current DSM-IV definition of Generalized Anxiety Disorder (GAD), and another emphasizing frequent unexplainable autonomic fearfulness, as in the early epidemiologic studies.

Physical and biological development of a newly breached managed realignment site, Humber estuary, UK.

As part of the Humber flood defence upgrade works (Urgent works) undertaken by the Environment Agency, the Paull Holme Strays site was identified as one of twelve potential managed realignment sites within the Humber catchment. The site was breached in September 2003, creating 80 hectares of new intertidal habitat. Initial accretion monitoring commenced in December 2003 with annual surveys of invertebrate colonisation commencing in October 2004. The present study gives details of the physical development of the newly created mudflat within the site, together with invertebrate colonisation and benthic community change over time. Comparisons between the newly created habitat and the existing mudflat outside the old sea wall are made. The macrofaunal communities found within the area as a whole are considered to be characteristic of the area with low species diversity, high abundance and small body size. The community within the managed realignment site is still in an early successional stage with low abundance and diversity in comparison with other sites within this part of the Humber. However the community biomass increased considerably between 2004 and 2005. Colonisation within the managed realignment site is still primarily concentrated in the areas around the two breach sites and is thought to be restricted in other areas due to infrequent tidal inundation.

Aerosols in the Pre-industrial Atmosphere.

PURPOSE OF REVIEW: We assess the current understanding of the state and behaviour of aerosols under pre-industrial conditions and the importance for climate. RECENT FINDINGS: Studies show that the magnitude of anthropogenic aerosol radiative forcing over the industrial period calculated by climate models is strongly affected by the abundance and properties of aerosols in the pre-industrial atmosphere. The low concentration of aerosol particles under relatively pristine conditions means that global mean cloud albedo may have been twice as sensitive to changes in natural aerosol emissions under pre-industrial conditions compared to present-day conditions. Consequently, the discovery of new aerosol formation processes and revisions to aerosol emissions have large effects on simulated historical aerosol radiative forcing. SUMMARY: We review what is known about the microphysical, chemical, and radiative properties of aerosols in the pre-industrial atmosphere and the processes that control them. Aerosol properties were controlled by a combination of natural emissions, modification of the natural emissions by human activities such as land-use change, and anthropogenic emissions from biofuel combustion and early industrial processes. Although aerosol concentrations were lower in the pre-industrial atmosphere than today, model simulations show that relatively high aerosol concentrations could have been maintained over continental regions due to biogenically controlled new particle formation and wildfires. Despite the importance of pre-industrial aerosols for historical climate change, the relevant processes and emissions are given relatively little consideration in climate models, and there have been very few attempts to evaluate them. Consequently, we have very low confidence in the ability of models to simulate the aerosol conditions that form the baseline for historical climate simulations. Nevertheless, it is clear that the 1850s should be regarded as an early industrial reference period, and the aerosol forcing calculated from this period is smaller than the forcing since 1750. Improvements in historical reconstructions of natural and early anthropogenic emissions, exploitation of new Earth system models, and a deeper understanding and evaluation of the controlling processes are key aspects to reducing uncertainties in future.

Affective disorders and mortality. A general population study.

A 16-year prospective study of a general population sample indicates that those who had reported a depression and/or anxiety disorder at baseline experienced 1.5 times the number of deaths expected on the basis of rates for a large reference population. As part of the Stirling County Study (Canada), the information was gathered from 1003 adults through structured interviews and was analyzed by means of a diagnostic computer program. The risk for mortality was assessed using external and internal standards, controlling for the effects of age and sex as well as for the presence of self-reported physical disorders at baseline. Increased risk was found to be significantly associated with affective but not physical disorders and with depression but not generalized anxiety. When this evidence about mortality was combined with information about subsequent psychiatric morbidity among survivors, 82% of those who were depressed at baseline had a poor outcome.

A 40-year perspective on the prevalence of depression: the Stirling County Study.

BACKGROUND: According to epidemiologic studies that use recall of lifetime episodes, the prevalence of depression is increasing. This report from the Stirling County Study compares rates of current depression among representative samples of adults from a population in Atlantic Canada. METHODS: Sample sizes were 1003, 1201, and 1396 in 1952, 1970, and 1992, respectively. The depression component of the study's method, the DPAX (DP for depression and AX for anxiety), was employed. The original procedure (DPAX-1) was applied in all years. A revision (DPAX-2) was used in 1970 and 1992. The Diagnostic Interview Schedule (DIS) was also used in 1992. RESULTS: With the DPAX-1, the overall prevalence of current depression was steady at 5% over the 2 early samples but declined in 1992 because of vernacular changes referring to dysphoria. The DPAX-2 gave a stable overall prevalence of 5% in the 2 recent samples, but indicated that women and younger people were at greater risk in 1992 than in 1970. The DIS, like the DPAX-2, found a current 1992 rate of 5% for major depressive episodes combined with dysthymia. Recalled lifetime rates using the DIS showed the same profile interpreted in other studies as suggesting an increase in depression over time. CONCLUSIONS: Three samples over a 40-year period showed a stable current prevalence of depression using the DPAX methods that was comparable in 1992 with the current rates using the DIS. This casts doubt on the interpretation that depression is generally increasing. Within the overall steady rate observed in this study, historical change was a matter of redistribution by sex and age, with a higher rate among younger women being of recent origin.

A comparison of diagnostic interviews for depression in the Stirling County study: challenges for psychiatric epidemiology.

BACKGROUND: High prevalence rates in psychiatric epidemiologic studies raise questions about whether data-gathering procedures identify transient responses rather than clinical disorders. This issue is explored relevant to depression using data from the Stirling County Study. METHODS: The study's customary method, the DPAX (DP for depression and AX for anxiety) was compared with the Diagnostic Interview Schedule (DIS), both of which were administered to a sample of 1396 subjects selected in 1992. Reasons for discordance were analyzed, and demographic correlates of responses to questions about dysphoria were examined. These lay-administered interviews were then compared with clinician-administered interviews that used the Structured Clinical Interview for DSM-III-R (SCID) with 139 subjects. The kappa statistic and logistic regression were used for statistical assessment. RESULTS: For the level of agreement between the DPAX and the DIS for current and lifetime depression, kappa = 0.40 and kappa = 0.33, respectively. Subjects diagnosed only by the DPAX tended to have less education than those diagnosed only by the DIS. Some idioms for dysphoria seemed to work better than others. Using SCID interviews as a clinical standard, the DPAX had 15% sensitivity and 96% specificity and the DIS had 25% sensitivity and 98% specificity. CONCLUSIONS: Comprehension of an interview can be improved by using multiple questions for dysphoria and a simpler mode of inquiry. Clinician-administered interviews tend to corroborate disorders identified in lay-administered interviews but suggest that survey methods underestimate prevalence. Further research is needed to evaluate the validity of both types of interviews, but evidence from a 16-year follow-up evaluation indicates that depression diagnosed by the DPAX is a serious disorder in terms of morbidity and mortality.

Stability of prevalence. Depression and anxiety disorders.

Information about point prevalence of depression and anxiety disorders from two cross-sectional surveys in Stirling County (Canada) indicates that an overall prevalence rate of 12.5% characterized a year close to midcentury and a prevalence rate of 12.7% characterized another year toward the end of the century's third quarter. The stability of the prevalence rates contrasts sharply with the fact that numerous social changes took place over this period of time in this place of study. There were, however, small trends in the distribution of depression and anxiety by sex and age, especially an increased similarity in the overall rates for men and women in the age range of 40 to 69 years. Hypotheses are offered about social circumstances that may have influenced the diminishing difference between the sexes.

Depression and anxiety in relation to social status. A prospective epidemiologic study.

Longitudinal research in Stirling County, Atlantic Canada, indicated that during the 1950s and 1960s the prevalence of depression was significantly and persistently higher in the "low" socioeconomic status population than at other socioeconomic status levels. Anxiety was found to show a less clear picture. Incidence of depression after the study started was also higher among those who were initially in the low socioeconomic status group, supporting the view that the stress of poverty may be causally related to depression. There was also a trend for prior depression to be associated with subsequent downward social mobility, supporting the view that the concentration of depressed people at the lower end of the social hierarchy may result from handicapping aspects of the illness. Neither of these trends was statistically significant. More striking was evidence that, irrespective of socioeconomic status, depression carried a substantial risk for poor clinical course and outcome. Both depression and poverty tended to be chronic, and, accordingly, their association at the end of the study was influenced by their association at its beginning. The stability of the relationship between poverty and depression warrants the attention of caregivers and policymakers and raises new questions about strategies for the study of causal sequences.

Barriers to adequate care for mentally ill people.

A serious and chronic problem that confronts mentally ill people and mental health professionals is the inability of society to provide the requisite resources for adequate care-giving systems. This difficulty has been evident for almost two hundred years. The present paper summarizes the major causal processes as these were revealed in the course of a case study of a mental health centre and its catchment area in Nova Scotia. These barriers to adequate care systems are then considered in historical perspective in order to illustrate how they function more generally. The historical perspective reveals a further handicap in the fact that experiences gained in one reform movement are not transmitted and utilized in subsequent efforts.

Surveillance of wild animal diseases in Europe.

A study of the methods and personnel involved in general surveillance of wild animal diseases in Europe was conducted by correspondence and personal interview in 1993-1994. Twenty-seven of the thirty-six countries contacted participated in the study. A great range was observed in the intensity of surveillance programmes and the details of their organisation. Programmes of comprehensive general surveillance were present in four countries, while eleven countries had general surveillance programmes which were limited to certain geographical regions and/or wild animal species. Twelve countries had no programmes of general wildlife disease surveillance, but had surveillance programmes for one or more specific diseases which included wild animals. Significant information on the occurrence of diseases in wild animals was available in each participating country. Factors found to be important in the structure and function of surveillance programmes were as follows: historical occurrences of rabies, hog cholera (classical swine fever), viral haemorrhagic disease of rabbits and the European brown hare syndrome; approaches to wildlife management and relationships between wildlife-oriented field personnel and the surveillance programme; whether or not fees were charged for diagnosis of diseases in wild animal specimens; training and equipment of diagnostic personnel; organisation of wild animal disease data.

Effects of photoperiod and filtered light on growth, reproduction, and mating behavior of turkeys. 1. Growth performance of two lines of males and females.

This study was designed to determine the effects of photoperiod and filtered light on growth of male and female turkeys. Large White (LW) and Medium White (MW) turkeys were reared under intermittent (2 h light: 2 h dark) or diurnal (12 h light: 12 h dark) photoperiods using white light, red (650 nm), or blue (450 nm)-filtered lights. Both males and females grew more rapidly under blue light than under red or white light up to 16 wk of age. After that age, rates of gain were significantly better under the white and red lights. Growth rates were significantly greater under the intermittent than under the diurnal photoperiod for both lines and sexes in Experiment 1 but not in Experiment 2. The greatest acceleration in growth rate was observed from 4 to 10 wk of age, with this advantage still evident at 24 wk of age. No significant differences in feed efficiency due to photoperiod or light color occurred. Early mortality was highest under blue light but late mortality was greater under red and white light. Mortality was higher for the LW than MW birds. Live grades were unaffected by light regimen or light color, but feather condition was poorest for birds reared under the white diurnal photoperiod.

Effects of light environment and population density on growth performance of male turkeys: 2. Physiological changes.

This study was designed to determine the effects of intermittent white light [2 h of light (L) followed by 2 h of dark (D) repeated six times per day] vs. diurnal white, blue, and red light (12L:12D), light intensities of 86.1 lx (high) vs. 5.4 lx (low) at high and low population densities, and season of the year on changes in the pineal, pituitary, and adrenal glands and testes of male turkeys. Pineal gland weights were unaffected by any of the factors under study. Pituitary gland weights significantly increased only in 12-wk-old males reared during the fall and winter compared with those reared during the spring and summer, but were unaffected by the imposed light environments or population density. Adrenal glands were significantly larger in males reared under high population density conditions in comparison with those reared under low density housing. The different light environments were ineffective in altering the effects of population density on adrenal response. Intermittent, high intensity light caused precocious sexual development when males were between 12 and 23 wk of age. White light and red-filtered light stimulated testes activity and seminiferous tubule development, whereas blue-filtered light was nonstimulatory.

Effect of presence or absence of the opposite sex on egg production and semen quality of breeder turkeys.

The effect of the presence or absence of the opposite sex on egg production and semen quality of breeder turkeys was evaluated. Ninety-six female and 36 male Medium White turkeys were used in this study. Two males were released, individually, into each of eight pens of females for 15 min each day, 5 days/wk. Two males in each of four pens of females were physically isolated in wire-enclosed cages in full view of the females. Males assigned to the remaining four pens of females were placed in isolated pens so they were physically, visually, and vocally separated from the females. Egg production was significantly higher for females under natural mating conditions than for females visually exposed to males in holding pens or for females completely isolated from males. Females visually exposed to, but not in contact with males, laid more eggs than those completely isolated from males during the 13th through the 18th week of production. Semen volume and semen concentration was significantly lower, and the percentage normal sperm was higher for males mating naturally than for those maintained in the presence of or completely isolated from females. Semen concentration was highest in isolated males.

Effect of light environment during the adolescent period on subsequent semen volume and concentration of male turkeys.

One hundred eighty males were utilized in two field-type experiments. In one experiment, light was restricted to 6 or 12 hr of light per day at a light intensity of 10.76 1x from 12 through 28 weeks of age. In the second experiment, one flock was maintained under natural light while the other was maintained under 12-hr lights and 10.76 1x of light intensity from 12 to 31 weeks of age. All flocks were placed under a 14-hr light day and a light intensity of 32.3 1x in light-controlled houses during the breeding season. Results obtained in the first experiment showed an increase in semen volume from the first to the fourth observation period and then a decline in both flocks during the last period. Average semen volume over the entire experimental period was unaffected by light treatment during the adolescent period. Semen concentration was highest during the early part of the breeding season and gradually declined as the season progressed. Males under a 6-hr restricted light regimen during the rearing period produced an average of .6 billion more sperm cells per milliliter than did those reared under 12 hr of light per day (P less than or equal to .01). Results obtained in the second experiment showed an average semen volume throughout the breeding season of .24 and .19 ml and a semen concentration of 7.0 and 6.4 billion sperm cells per milliliter for males reared under natural light compared to those reared under 12-hr lights, respectively . These differences were significant (P less than or equal to .01). Data were subjected to polynomial analyses.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of light environment and population density on growth performance of male turkeys.

This study was designed to determine the effects of various light environments on the growth performance of male turkeys reared under two extremes of population density. Environmental lighting had subtle but persistent effects on growth performance. Low-intensity illumination consistently improved body weight gains during early growth periods while high-intensity illumination improved body weight gains during the later growth period. Intermittent lighting, especially at a light intensity of 86.1 1x, caused precocious sexual development and appeared to stimulate growth after 18 weeks of age during cool weather and after 12 weeks during warmer weather. Diurnal, blue-filtered light improved weight gains during early growth periods compared to either white- or red-filtered diurnal light, while white- or red-filtered light tended to improve weight gains during the later growth period. Floor space allowances studied had no significant effect on growth or feed efficiency prior to 12 weeks of age. At that time, high population density caused lower body weight gains, lower feed efficiency, poorer feathering, a higher incidence of downgrading, and higher mortality than did a relatively low population density. Different light environments [intermittent (2L:2D) white light and diurnal (12L:12D), white-, red-, or blue-filtered light] were ineffective in altering the responses of turkeys to crowding. There was, however, a significant interaction of light intensity with population density. This interaction indicated that high light intensity allowed maximum expression of growth potential in a low population density environment but reduced growth under high population density pressures.