Cellulitis in chronic oedema of the lower leg: an international cross-sectional study.

BACKGROUND: Cellulitis and chronic oedema are common conditions with considerable morbidity. The number of studies designed to assess the epidemiology of cellulitis in chronic oedema is scarce. OBJECTIVES: To investigate the prevalence and risk factors of cellulitis in chronic leg oedema, including lymphoedema. METHODS: A cross-sectional study included 40 sites in nine countries during 2014-17. Adults with clinically proven unilateral or bilateral chronic oedema (oedema > 3 months) of the lower leg were included. The main outcome measures were frequency and risk factors for cellulitis within the last 12 months. RESULTS: Out of 7477 patients, 15·78% had cellulitis within the last 12 months, with a lifetime prevalence of 37·47%. The following risk factors for cellulitis were identified by multivariable analysis: wounds [odds ratio (OR) 2·37, 95% confidence interval (CI) 2·03-2·78], morbid obesity (OR 1·51, 95% CI 1·27-1·80), obesity (OR 1·21, 95% CI 1·03-1·41), midline swelling (OR 1·32, 95% CI 1·04-1·66), male sex (OR 1·32, 95% CI 1·15-1·52) and diabetes (OR 1·27, 95% CI 1·08-1·49). Controlled swelling was associated with a reduced risk (OR 0·59, 95% CI 0·51-0·67). In a subgroup analysis, the risk increased with the stage of oedema [International Society of Lymphology, stage II OR 2·04 (95% CI 1·23-3·38) and stage III OR 4·88 (95% CI 2·77-8·56)]. CONCLUSIONS: Cellulitis in chronic leg oedema is a global problem. Several risk factors for cellulitis were identified, of which some are potentially preventable. Our findings suggest that oedema control is one of these. We also identified that advanced stages of oedema, with hard/fibrotic tissue, might be an important clinical indicator to identify patients at particular risk.

The campylobacteriosis conundrum - examining the incidence of infection with Campylobacter sp. in Australia, 1998-2013.

Campylobacter sp. are a globally significant cause of gastroenteritis. Although rates of infection in Australia are among the highest in the industrialized world, studies describing campylobacteriosis incidence in Australia are lacking. Using national disease notification data between 1998 and 2013 we examined Campylobacter infections by gender, age group, season and state and territory. Negative binomial regression was used to estimate incidence rate ratios (IRRs), including trends by age group over time, with post-estimation commands used to obtain adjusted incidence rates. The incidence rate for males was significantly higher than for females [IRR 1·20, 95% confidence interval (CI) 1·18-1·21], while a distinct seasonality was demonstrated with higher rates in both spring (IRR 1·18, 95% CI 1·16-1·20) and summer (IRR 1·17, 95% CI 1·16-1·19). Examination of trends in age-specific incidence over time showed declines in incidence in those aged <40 years combined with contemporaneous increases in older age groups, notably those aged 70-79 years (IRR 1998-2013: 1·75, 95% CI 1·63-1·88). While crude rates continue to be highest in children, our findings suggest the age structure for campylobacteriosis in Australia is changing, carrying significant public health implications for older Australians.

A large outbreak of Campylobacter jejuni infection in a university college caused by chicken liver pâté, Australia, 2013.

In October 2013, public health authorities were notified of a suspected outbreak of gastroenteritis in students and guests following a catered function at a university residential college. A retrospective cohort study was undertaken to examine whether foods served at the function caused illness. A total of 56 cases of gastroenteritis, including seven laboratory-confirmed cases of Campylobacter jejuni infection, were identified in 235 eligible respondents. Univariate analysis showed a significant association with a chicken liver pâté entrée [relative risk (RR) 3·64, 95% confidence interval (CI) 2·03-6·52, P < 0·001], which retained significance after adjustment for confounding via multivariable analysis (adjusted RR 2·80, 95% CI 1·26-6·19, P = 0·01). C. jejuni and C. coli were also isolated in chicken liver pâté recovered from the college's kitchen. Subsequent whole genome multilocus sequence typing (wgMLST) of clinical and food-derived C. jejuni isolates showed three genetically distinct sequence types (STs) comprising ST528, ST535 (both clinically derived) and ST991 (food derived). The study demonstrates the value of utilizing complementary sources of evidence, including genomic data, to support public health investigations. The use of wgMLST highlights the potential for significant C. jejuni diversity in epidemiologically related human and food isolates recovered during outbreaks linked to poultry liver.

A preliminary randomized controlled study to determine the application frequency of a new lymphoedema bandaging system.

BACKGROUND: Bandaging plays an important role in the treatment of lymphoedema. OBJECTIVE: To investigate efficacy and safety of the 3M™ Coban™ 2 compression system (Coban 2 system) with different application frequencies in comparison to short-stretch bandaging. METHODS: A multicentre, randomized, prospective study was performed with 82 patients suffering from arm or leg lymphoedema stage II or late stage II. Patients were allocated to traditional short-stretch bandaging five times per week or to the Coban 2 system applied two, three or five times per week for 19 days. Limb volume and adverse events were recorded at each study visit. The primary endpoint was percentage volume reduction. RESULTS: The highest lymphoedema volume reduction was achieved with the Coban 2 system applied two times per week. A mean reduction of 18·7% (SD 14·5) in legs and 10·5% (SD 8·3) in arms was achieved. More frequent bandage changes of three and five times per week did not demonstrate additional benefits. Short-stretch bandaging five times per week showed a mean volume reduction of 10·9% (SD 5·2) and 8·2% (SD 3·1) for legs and arms, respectively. Bandage slippage was low for all treatment groups. A relevant change in overall mobility was achieved during the use of the Coban 2 system. The adverse reactions were in agreement with already known side-effects and did not differ remarkably between the treatment groups. CONCLUSION: The 3M™ Coban™ 2 compression system applied twice weekly demonstrated a high rate of volume reduction and a good safety profile. Oedema reduction was still effective with 4 days between bandage change, which allows a constant therapeutic effect in routine practice. This should give the patient a high degree of independence and mobility.

Efficacy of two compression systems in the management of VLUs: results of a European RCT.

OBJECTIVE: To evaluate the efficacy, tolerance and acceptability an innovative two-layer system (KTwo; Laboratoires URGO) versus an established four-layer bandage system (Profore; Smith & Nephew) in the local management of venous leg ulcers. METHOD: A non-inferiority European randomised controlled trial, conducted in 37 centres, in three countries (France, U.K. and Germany), on patients presenting with venous leg ulcers (VLUs). Participants were adult, non-immunosuppressed patients who presented with non-infected, non-malignant leg ulcers, predominantly of venous origin (ABPI > 0.8), with a surface area of 2-50 cm2 and duration 1-24 months. Patients were followed-up every 2 weeks for a period of 12 weeks, or until full closure. Visits included a clinical examination, wound area tracings and photographic evidence. The primary endpoint was the percentage of leg ulcers healed after the 12 weeks, with secondary endpoints of relative wound area reduction (RWAR), absolute wound area reduction (AWAR) and the percentage of wounds with RWAR > or = 40%. RESULTS: In total, 187 patients were randomised to either the two-layer bandage (2LB, n=94) or four-layer bandage (4LB; n=93) system. The two groups were comparable,with regard to wound and patient characteristics, at baseline. By week 12, 44% of VLUs in the 2LB group and 39% in the 4LB group had healed (intention-to-treat [ITT] analysis). The per-protocol (PP) analysis showed that complete wound closure was obtained in 48% and 38% of the 2LB and 4LB groups, respectively. A non-inferiority margin within -10% is considered as demonstrating a 95% and 97.5% confidence interval (p = 0.001). The AWAR was 6.6 cm2 in the test and 4.9 cm2 in the control group. The percentage of wounds with a RWAR > OR =40% was 47% and 44% for the 2LB and 4LB systems, respectively. Pain between dressing changes was reported in 27% of the test and 40% of the control group, and the incidence of adverse events was 17% and 25%, respectively. The 2LB compression system was considered to be significantly easier to apply than the 4LB (p = 0.038). CONCLUSION: The 2LB system (KTwo) was not seen to be any less effective than a well-known 4LB system (Profore) in the management of VLUs. Furthermore, the 2LB system was considered to be easier to apply, representing an alternative to the conventional treatment with 4LB currently available. DECLARATION OF INTEREST: This study was sponsored by a grant from Laboratoires URGO, manufacturers of KTwo. S. Bohbot and A. Sauvadet are employees of Laboratoires Urgo. S. Meaume has received monetary compensation as a speaker for Laboratoires Urgo. Data management and statistical analyses were conducted by Vertical (J. C. Kerihuel; Paris, France).

The experience of patients with complex wounds and the use of NPWT in a home-care setting.

OBJECTIVE: To explore the experience of patients living with complex wounds and the impact of undergoing negative pressure wound therapy (NPWT) as part of their treatment. METHOD: Qualitative data were collected from eight patients, using semi-structured interviews. A purposive, stratified sampling approach was used to identify participants with a range of wound types, as well as age and gender. Participants were recruited from one primary care trust and were interviewed, following 10 days of treatment with NPWT. The matrix-based 'Framework' approach, from the National Centre for Social Research, was used to structure the analysis. RESULTS: Of the eight participants recruited, five were female and three male, with an age range of 46-77 years. Five overarching categories, with their constituent themes, were identified from the data. The first, developing a wound through crisis, has three themes: a failing body, missed diagnosis and failed professional intervention. The second category, decreased control, has four related themes: poor communication; failed wound healing; poor discharge planning and failure to recover. The third category, increased control, has four themes: understanding what is happening; symptom control; positive professional relationships and returning to health. The fourth category, using NPWT, has two themes: information and understanding of NPWT and expectations and experience of NPWT. The final category sets out participant recommendations about the device and has two themes: device issues and improving professional practice. CONCLUSION: This study investigated the experience of patients undergoing NPWT for complex wounds in the home setting and reveals a number of the psychosocial effects of using this therapy in this environment. Participants saw NPWT as an active intervention, associated with improved wound healing and symptom control. The participant experience described in this study, and the recommendations they make, provide a valuable resource to inform service improvement programmes and wound research. DECLARATION OF INTEREST: This study was supported by a research grant from Smith & Nephew Ltd.

Clinical predictors of leg ulcer healing.

Background Identification of factors associated with healing can help in understanding the causes of delayed healing in chronic leg ulceration, and can allow for programmes to be developed to modify these factors to improve patient outcomes. Objectives To determine factors associated with healing in patients with chronic leg ulceration of all types within a defined patient population. Methods The patients were identified within the combined acute/community leg ulcer service within Wandsworth Primary Care Trust. All identified patients agreed to be interviewed and those who were able underwent clinical and noninvasive testing to determine the cause of the ulceration. Follow ups were to a maximum of 48 weeks, with time to healing given as the principal outcome measure. Analysis was by the Cox proportional hazards model for both univariate and multivariate analysis. Results were expressed as hazard ratio with 95% confidence intervals derived from the models. Results In total, 113 patients took part in this study. Univariate analysis revealed statistically significant differences for delayed healing according to the ulcer duration (P = 0.002), complexity of the ulcer aetiology (P = 0.035), presence of lipodermatosclerosis (P = 0.02), history of deep vein thrombosis (DVT) (P = 0.03) and thrombophlebitis (P = 0.03). Multivariate analysis showed that ulcer duration (P = 0.014), DVT (P = 0.008) and a lack of Pseudomonas on wound swab (P = 0.005) were independently associated with delayed healing. Conclusions The results indicate the complexity of determining risk factors for poor healing in patients with chronic leg ulceration. There appears to be little scope for interventions to improve healing from the factors identified.

Surveillance for outbreaks of influenza-like illness in the institutionalized elderly.

Respiratory outbreaks are common in aged-care facilities (ACFs), are both underreported and frequently identified late, and are often associated with considerable burden of illness and death. There is emerging evidence that active surveillance coupled with early and systematic intervention can reduce this burden. Active surveillance for influenza-like illness and rapid diagnosis of influenza were established in 16 ACFs in Sydney, Australia, prior to the winter of 2006. A point-of-care influenza test and laboratory direct immunofluorescence tests for common respiratory viruses were used for diagnosis. We achieved early identification of seven respiratory disease outbreaks, two of which were caused by influenza. For the influenza outbreaks, antiviral treatment and prophylaxis were initiated 4-6 days from symptom onset in the primary case. A simple active surveillance system for influenza was successfully implemented and resulted in early detection of influenza and other respiratory disease outbreaks. This enabled earlier implementation of prevention and control measures and increased the potential effectiveness of anti-influenza chemoprophylaxis.

Psychological factors in leg ulceration: a case-control study.

BACKGROUND: There is increasing recognition of the role that psychological status plays in the development and outcomes of chronic disease, but little understanding of its importance in chronic leg ulceration. OBJECTIVES: To examine psychological health and perceived social support in patients with chronic leg ulceration. METHODS: Patients with leg ulceration within a defined population were matched for age and gender (1:1) with community controls in a matched case-control study. Analysis was by conditional logistic regression and matched t-test analysis. RESULTS: Ninety-five patients (60 women and 35 men; 59% aged over 75 years) were identified and matched to the same number of controls. Cases had significantly poorer health-related quality of life in all domains of the Nottingham Health Profile (all P < or = 0.001), compared with controls. Levels of depression (Hospital Anxiety and Depression Scale) were significantly greater in the patient group (mean 5.3 vs. 3.6, P < 0.001). Social support (Medical Outcomes Study Social Support Survey scale) showed significantly fewer social networks and less perceived social support in patients than controls (P = 0.008). Patients used significantly fewer coping strategies (COPE scale) than controls, particularly with regard to problem-focused coping strategies. CONCLUSIONS: Patients with leg ulceration experience poor psychological health with a greater risk of depression, less perceived social support and greater social isolation. Systems of care should offer an environment that reduces social isolation and increases support to this patient group.

Assessing community nurses' level of knowledge of lymphoedema.

As part of a major project to develop a primary care trust-based framework of lymphoedema management, the educational needs of community nurses regarding the care of patients with lymphoedema were assessed using focus groups and questionnaires. Community nurses assessed their current knowledge and skill in the care and management of patients with lymphoedema as adequate or poor. They were concerned about their lack of knowledge and skill and were uncertain regarding their role relative to other professions involved in the care of this patient group. At the same time they understood the importance of their role in providing ongoing care, recognizing problems, offering sound advice and referring on to a specialist practitioner when necessary. Any education provision that prepares community nurses for their role within a framework of lymphoedema management should emphasize the important place they occupy in providing long-term care for this patient group.

Winter adaptations of male deer mice (Peromyscus maniculatus) and prairie voles (Microtus ochrogaster) that vary in reproductive responsiveness to photoperiod.

Individuals of many nontropical rodent species restrict breeding to the spring and summer. Seasonal reproductive quiescence putatively reflects the energetic incompatibility of breeding and thermoregulatory activities. However, so-called "out-of-season" breeding occurs in virtually all rodent populations examined, suggesting that the incompatibility can be resolved. Both reproductive inhibition and development of energy-saving adaptations are mediated by environmental photoperiod, but some individuals do not inhibit reproduction in short days. In order to assess the costs and benefits of winter breeding, the present study examined the extent to which male prairie voles (Microtus ochrogaster) and deer mice (Peromyscus maniculatus) that maintained summer reproductive function in winter-simulated daylengths also maintained summer thermoregulatory adaptations. Circadian locomotor activity patterns, basal metabolic rate, capacity for nonshivering thermogenesis, nest building, body mass, and daily food consumption were compared among short-day (LD 8:16) regressed males, short-day (LD 8:16) nonregressed males, and long-day (LD 16:8) males. Short-day nonregressed deer mice resembled long-day conspecifics in terms of body mass and nest-building activities; however, the locomotor activity pattern of short-day nonregressed deer mice was similar to that of their short-day regressed conspecifics. Short-day nonregressed prairie voles had body masses similar to those of long-day conspecifics. Regardless of their reproductive response to photoperiod, short-day prairie voles reduced their daily food consumption and wheel-running activity, compared to long-day voles. These results suggest that winter breeding has energetic costs, most likely resulting from maintaining a "summer-like" body mass relative to that of reproductively regressed animals. These costs may be ameliorated to some extent by the reduction in locomotor activity and nest-building behavior emitted by short-day animals, regardless of reproductive response to short days. Thus, the occurrence of winter breeding may be the result of sufficient numbers of reproductively photoperiod-nonresponsive morphs in the population and sufficiently mild ambient conditions to permit survival of these larger animals.

Progesterone-independent activation of rat brain progestin receptors by reproductive stimuli.

Activation of steroid hormone receptors by steroid hormones alters both the physiology and behavior of animals. Steroid hormone receptors (e.g., progestin receptors) can also be activated in the absence of steroid hormones by pharmacological treatment with neurotransmitters or neuropeptides. However, it is not known if progesterone-independent activation of brain progestin receptors occurs under natural, physiological, conditions. We report that increases in reproductive behavior and brain immediate early gene expression in female rats induced by mating stimuli can be blocked by prior treatment with progesterone antagonists in the absence of circulating progesterone. This suggests that progestin receptors are activated in a progesterone-independent manner by a physiologically relevant stimulus in female rats, thus implicating a novel pathway by which mating stimuli and other environmental influences could activate steroid receptors to influence neuronal response and behavior.

Reproductively-relevant stimuli induce Fos-immunoreactivity within progestin receptor-containing neurons in localized regions of female rat forebrain.

An experiment was conducted to determine if neurons that respond to stimuli associated with mating in female brain also contain progestin receptors. We found that a portion of the neurons that respond to stimuli associated with mating also contains progestin receptors. While the appropriate hormonal conditions are important for sexual receptivity, somatosensory information provided by the male also influences sexual behavior. One important stimulus provided by the male during copulation is vaginal-cervical stimulation (VCS). VCS has been shown to elicit many different behavioral and endocrine changes in female rats, such as increases in lordosis, pseudopregnancy, and termination of sexual receptivity. VCS also increases the expression of the immediate early gene product, Fos, in areas associated with reproduction. A portion of the neurons responding to VCS with increased Fos-immunoreactivity (Fos-IR) in female rat forebrain also contains estrogen receptors, illustrating that hormonal and mating-stimuli converge in a population of cells. As progesterone also plays an important role in female sex behavior, it is important to determine if some of the neurons also integrate information concerning serum progesterone levels and social interactions. Thus, we used a dual immunofluorescent technique to label both Fos-IR and progestin receptor-immunoreactivity (PR-IR) in the brains of estradiol-primed, ovariectomized female rats following VCS manually applied by the experimenter. Many of the neurons that respond to VCS with increased Fos-IR within the medial preoptic area, the arcuate nucleus, and the progestin receptor-rich areas of the rostral and caudal ventromedial nucleus of the hypothalamus also contain PR-IR.

Prevalence of leg ulceration in a London population.

BACKGROUND: Current prevalence estimates of chronic leg ulceration are frequently based on studies from the 1980s. During the last decade, major changes have occurred in the application of evidence-based practice to this condition. AIM: To determine the prevalence and cause of leg ulceration in a defined geographical population after 8 years of providing standardized evidence based protocols of care. DESIGN: Prospective survey. METHODS: Patients with leg ulceration of >4 weeks duration) within an integrated acute and community leg ulcer service were ascertained, interviewed and clinically assessed, using a standardized questionnaire on medical history, ulcer details and non-invasive vascular investigation to describe causes. Ulcers were classified by aetiology. RESULTS: We identified 113 patients in a population of 252 000, giving a crude prevalence of 0.45/1000 (95%CI 0.37-0.54/1000): 0.34/1000 in men, 0.54/1000 in women. Rates were highly dependent on age, increasing to 8.29 (men) and 8.06/1000 (women) in those aged >85 years. Of the responders, 62/113 (55%) had their ulcer for >1 year. Uncomplicated venous ulceration was observed in only 59/138 (43%) ulcerated limbs; a further 21 had ulceration primarily due to arterial disease. Complex causes were present in 48 (35%) limbs, mostly venous disease in combination with diabetes (35%), lymphoedema (42%) and rheumatoid arthritis (26%). DISCUSSION: Our prevalence of chronic leg ulceration is approximately one-third of that predicted by previous studies using similar methodologies in the 1980s. Patients with ulceration have more complex aetiologies than previously recognized, which may be a consequence of both increasing ulcer chronicity and age.

Lymphoedema: an underestimated health problem.

BACKGROUND: Lymphoedema/chronic oedema is an important cause of morbidity in the population, but little is known of its epidemiology and impact on patients or health services. AIM: To determine the magnitude of the problem of chronic oedema in the community, and the likely impact of oedema on use of health resources, employment and patient's quality of life. DESIGN: Questionnaire-based survey. METHODS: Health professionals from dedicated lymphoedema services, specific out-patient clinics, hospital wards and community services (GP clinics and district nurses) were contacted to provide information on patients from within South West London Community Trust. A subset of the identified patients was interviewed. RESULTS: Within the catchment area, 823 patients had chronic oedema (crude prevalence 1.33/1000). Prevalence increased with age (5.4/1000 in those aged > 65 years), and was higher in women (2.15 vs. 0.47/1000). Only 529 (64%) were receiving treatment, despite two specialist lymphoedema clinics within the catchment area. Of 228 patients interviewed, 78% had oedema lasting > 1 year. Over the previous year, 64/218 (29%) had had an acute infection in the affected area, 17/64 (27%) being admitted for intravenous antibiotics. Mean length of stay for this condition was 12 days, estimated mean cost pound 2300. Oedema caused time off work in > 80%, and affected employment status in 9%. Quality of life was below normal, with 50% experiencing pain or discomfort from their oedema. DISCUSSION: Chronic oedema is a common problem in the community with at least 100 000 patients suffering in the UK alone, a problem poorly recognized by health professionals. Lymphoedema arising for reasons other than cancer treatment is much more prevalent than generally perceived, yet resources for treatment are mainly cancer-based, leading to inequalities of care.

The effects of photoperiod on olfactory c-fos expression in prairie voles, Microtus ochrogaster.

Reproduction stops among the majority of prairie voles (Microtus ochrogaster) during the winter. Short day lengths suppress male reproductive function dramatically in the laboratory, but photoperiod exerts only subtle effects on female reproductive function. Thus, the regulation of seasonal breeding in this species remains partially unspecified. In contrast to commonly studied rodents, female prairie voles do not undergo spontaneous estrous cycles; rather, they are induced into estrus by exposure to chemosignals expressed in conspecific male urine. In the present study, the hypothesis was tested that seasonal breeding among female prairie voles in the field reflects photoperiod-mediated changes in the responsiveness of the chemosensory system to male urine. Responsiveness was assessed by localizing the product of the c-fos immediate early gene with an immunocytochemical procedure. Female prairie voles were maintained in either long (LD 16:8) or short (LD 8:16) photoperiods from birth until adulthood, and exposed to either male urine or skim milk. Immunocytochemistry for fos protein revealed an increased number of immunoreactive cells within the accessory olfactory system of female prairie voles, including the accessory olfactory bulbs, granule cell layer, as well as the medial and cortical divisions of the amygdala 1 h after exposure to a single drop of urine as compared to individuals exposed to skim milk. The number of immunoreactive fos cells induced in females by conspecific male urine was also affected by photoperiod; short day females displayed fewer immunoreactive fos neurons in the accessory olfactory system as compared to long-day animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Venous ulcer healing: effect of socioeconomic factors in London.

OBJECTIVE: To determine which social and clinical factors are associated with healing in patients with venous ulceration. DESIGN: Patients were questioned about social factors at their first visit to a community ulcer clinic. They were treated by high compression bandage system and were interviewed again after 12 weeks. SETTING: Community leg ulcer clinics held in health centres throughout Riverside Health Authority in London. PATIENTS: All patients referred to five community leg ulcer clinics with venous ulceration over a six month period. MAIN OUTCOME MEASURES: These were factors significantly associated with healing within 12 weeks of beginning treatment, measured by odds ratio (OR) given by logistic regression analysis. MAIN RESULTS: Of 168 patients with venous ulceration, 87 (52%) healed after 12 weeks of treatment. Univariate analysis showed that low social class (OR = 3.44, 95% CI 1.17, 10.14), lack of central heating (OR = 2.22, 95% CI 1.18, 4.18), and being single (OR = 2.77, 95% CI 1.15, 6.69) were all significantly associated with delayed healing. After adjustment for the known risk factors of ulcer size, ulcer duration, and general mobility only lack of central heating was still significant (OR = 2.27, 95% CI 1.11, 4.55). The remaining factors failing to achieve statistical significance because of their inter-relationship with the known risk factors. CONCLUSIONS: Clinical features of the ulcer seem to determine the progress of healing in patients with leg ulceration. Although there were associations between socio-economic factors and poor healing, adjustment for clinical risk factors generally led to lower non-significant associations. Only lack of central heating retained its association and may play a part in prolonging healing of venous ulceration.

Day length influences proceptive behavior of female prairie voles (Microtus ochrogaster).

Prairie voles typically do not breed during the winter; instead, they typically confine breeding to the spring and summer. One proximate cue contributing to this seasonal change in breeding among males is photoperiod. However, photoperiod does not appear to affect female fecundity. Female prairie voles are induced into estrus by chemosensory cues in the urine of male conspecifies. Females are exposed to these cues when they groom the ano-genital region of males. Females that do not groom the ano-genital region of males rarely become estrus. Ano-genital grooming can be considered a proceptive behavior because the onset of estrus is dependent upon females exhibiting this behavior. This study addressed whether or not photoperiod influenced the proceptive behavior of female prairie voles. The results indicated that females maintained in a long photoperiod groomed the ano-genital region of anesthetized stimulus males more frequently than females maintained in a short photoperiod. This change in proceptive behavior may contribute to the seasonal changes in breeding exhibited by prairie voles.

Effects of photoperiod and 6-methoxy-2-benzoxazolinone on male-induced estrus in prairie voles.

Prairie voles (Microtus ochrogaster) are characterized as facultative breeders with higher rates of reproductive activities observed during spring and summer than autumn and winter. The environmental factors regulating seasonal breeding in this species remain unspecified. Short day lengths inhibit reproductive organ development in male prairie voles in the laboratory, but these males remain fertile and capable of siring offspring; female prairie voles have been reported to be reproductively unresponsive to day length in the laboratory. The organization of estrus in this species is unusual in that females never display the cyclic changes associated with estrus; rather, female prairie voles require chemosensory stimuli associated with fertile males in order to be induced into estrus. The plant compound, 6-methoxy-2-benzoxazolinone (6-MBOA), is present in vegetatively growing grasses and sedges and acts to trigger reproduction in other rodent species exposed to short days. It was suspected that 6-MBOA present in the laboratory diet may have overridden the effects of photoperiod on female prairie voles in previous laboratory studies. In the present study, the effects of 6-MBOA and photoperiod on estrus induction were examined. Beginning at Week 0, female prairie voles were housed in long (LD 16:8) or short (LD 8:16) photoperiods for 9 weeks, then implanted subcutaneously either with an empty Silastic capsule or one packed with 6-MBOA. A special diet, devoid of 6-MBOA, was available ad lib from Week 5 to the end of the study.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of photoperiod and food intake on reproductive development in male deer mice (Peromyscus maniculatus).

Seasonal breeding is a tactic that has evolved in rodents that limits reproduction to specific times of the year to increase reproductive success. In order to time breeding accurately, many animals respond to changes in daily photoperiod. Short day lengths inhibit breeding in many nontropical rodent species. Restricted food availability can also inhibit reproductive function among some individuals in these so-called "photoperiodic" populations. Rodents born at the end of the breeding season typically delay sexual maturation until the following spring. Prepubertal rodents exposed to day lengths that are < 12 h light/day will not undergo puberty for 4-7 months in the laboratory. Food restriction can also affect the timing of puberty onset. Reproductive function of food-restricted juvenile mice may remain inhibited until food availability improves. Alternatively, reproductive function of food-restricted juvenile mice might eventually develop despite restricted food intake. This study examined the effects of chronic food restriction and photoperiod on reproductive development in male deer mice (Peromyscus maniculatus bairdii). Short-day mice fed ad lib delayed gonadal development for 5-7 months, but eventually achieved reproductive maturity. The reproductive function of short-day mice fed ad lib was indistinguishable from long-day control animals when assessed at week 32. Long-day food-restricted mice exhibited an intermediate level of gonadal development and function. Short-day food-restricted deer mice also inhibited reproductive growth, but failed to demonstrate reproductive maturity by week 32 of the study. Taken together, these results suggest that retardation of reproductive development by food restriction is only superficially similar to the delay in reproductive maturation imposed by short day exposure. It does not appear that male deer mice escape from the inhibitory effects of food restriction to attain sexual development.