Evaluation of Fasting and Probiotics in Reducing Postweaning Stress in Rabbits: Study of their Effects on Biochemical and Gene expression Patterns

Postweaning stress in mammalian in vivo models leads to significant oxidative stress in the body as well as inducing hormonal disturbance. In this study, we assessed progressive alterations in reactive oxygen species (ROS), which at high levels can show oxidative stress, in addition to oxidative damage to the DNA structure of rabbits. Different groups of rabbits were fasted for 48 h per week for 3 weeks, fed a commercial diet with probiotics added (200 mg of Bacillus licheniformis and Bacillus subtilis), and fasted while being treated with probiotics. The results showed that weaning induced a significant elevation in oxidative stress markers, such as the ROS-related genes malate dehydrogenase 1 (MDH1) and flavin-containing monooxygenase 2 (FMO2), DNA damage, and hormonal disturbance. However, probiotic treatment resulted in significant decreases in the levels of malondialdehyde, cortisol, and triiodothyronine (T3); DNA damage; and apoptosis, as well as changes in the expression of ROS-related genes. On the other hand, supplementation with probiotics reduced these postweaning stress signs in fasted animal models by elevating the genes encoding catalase and superoxide dismutase as well as increasing glutathione peroxidase (GSH-Px), glutathione-s-transferase, alkaline phosphatase, glucose, and thyroxin (T4) levels. The results suggest that supplementation with probiotics accompanied by a fasting program could decrease oxidative stress, ROS genes, and genomic DNA damage and improve the hormonal status that is induced by postweaning stress in mammalian in vivo models.

Fast fetal head compounding from multi-view 3D ultrasound

The diagnostic value of ultrasound images may be limited by the presence of artefacts, notably acoustic shadows, lack of contrast and localised signal dropout. Some of these artefacts are dependent on probe orientation and scan technique, with each image giving a distinct, partial view of the imaged anatomy. In this work, we propose a novel method to fuse the partially imaged fetal head anatomy, acquired from numerous views, into a single coherent 3D volume of the full anatomy. Firstly, a stream of freehand 3D US images is acquired using a single probe, capturing as many different views of the head as possible. The imaged anatomy at each time-point is then independently aligned to a canonical pose using a recurrent spatial transformer network, making our approach robust to fast fetal and probe motion. Secondly, images are fused by averaging only the most consistent and salient features from all images, producing a more detailed compounding, while minimising artefacts. We evaluated our method quantitatively and qualitatively, using image quality metrics and expert ratings, yielding state of the art performance in terms of image quality and robustness to misalignments. Being online, fast and fully automated, our method shows promise for clinical use and deployment as a real-time tool in the fetal screening clinic, where it may enable unparallelled insight into the shape and structure of the face, skull and brain.

The effect of Ramadan and intermittent fasting on the development of Helicobacter pylori-induced peptic ulcers

A considerable portion of the world's population practices fasting, for religious purposes like Ramadan or to adopt a healthier lifestyle such as intermittent fasting. During this period, individuals undergo metabolic changes that alter their internal environment. The literature was analysed to identify a possible relationship between fasting and the development of Helicobacter pylori-induced peptic ulcers. This found that fasting does not affect the incidence of peptic ulcers, and studies that saw an increase in the incidence were not significant. However, remodelling of the gastric environment and increases in concentrations of H. pylori were recorded. There is no relationship between fasting and the risk of developing H. pylori-induced peptic ulcers, suggesting that individuals with uncomplicated ulcers are not at risk of developing further ulcers and can participate in fasts provided they take the recommended measures.

Superfast Magnetic Resonance Imaging-based Diagnostic Pathway for Prostate Cancer

We describe a <36-h superfast diagnostic pathway for men at risk of prostate cancer (PCa) that was initiated in our centre in March 2022. Patients are scheduled to undergo a repeat prostate-specific antigen blood test, magnetic resonance imaging, a urology consultation, and, if indicated, prostate biopsies in a single morning. The histopathology report is available the next day, after which the biopsy results and treatment options are discussed via a telephone consultation. The project has included 122 patients so far. With a reduction to only one hospital visit per patient and just five appointments (4%) cancelled so far, this timely pathway seems to be efficient from a patient perspective. In addition, reducing the waiting time until histopathology diagnosis could decrease the anxiety and depression that patients may experience during the diagnostic workup for PCa. Therefore, we believe that this fast-track diagnostic pathway could be incorporated in the future European standard of care, bringing PCa care in line with other malignancies such as breast cancer.

Patient summary

We describe a superfast diagnostic pathway for men at risk of prostate cancer. So far, this strategy seems to be an efficient and appropriate way to shorten time to diagnosis and to reduce the number of hospital visits for patients.

A hypnotic turbo-induction technique for wisdom tooth extraction

The hypnotic turbo-induction technique has been used for more than three decades for various indications in dentistry and medicine. The use of the technique is described step by step using therapeutic communication and hypnotic suggestions in a dento-surgical treatment of a 48-year-old adult man. In a 15-minute appointment, two maxillary third molars (wisdom teeth) have been extracted without interruptions/complications by a dental team in a private practice trained in dental/medical hypnosis. The hypnotic turbo-induction technique proved to be a successful application method for anxiety reduction/relaxation, pain relief as well as postoperative wound healing after the extraction of wisdom teeth, which had to be extracted due to a medical indication. Anxiety- and pain reducing effects were noted by the patient during and after the treatment; rapid wound healing was noted by the dental team at the follow-up appointment one week later in this case. The cooperation of the two dental professionals trained in hypnosis proved to be beneficial, especially when the dentist must concentrate on the dento-surgical treatment, the dental assistant can concentrate on both the patient and the hypnosis and to maintain the hypnotic state by additional suggestions. Clinical research is needed to further investigate the effects of the proposed hypnotic turbo-induction technique.

The Impact of the Rate of Weight Loss on Body Composition and Metabolism

PURPOSE OF REVIEW

Weight loss has multiple beneficial effects on body composition and metabolism, but whether these depend on the rate at which body weight is lost is not clear. We analyzed data from studies in which the same amount of weight loss was induced rapidly or gradually.

RECENT FINDINGS

Thirteen studies were included in which the same percentage weight loss was achieved at slow or fast rates (range: 0.2 to 3.2 kg/week) by means of dietary calorie restriction, exercise, and bariatric surgery. Faster rates of weight loss may result in more fat-free mass and less fat mass being lost during the dynamic phase of weight reduction compared with slower rates of weight loss, in conjunction with greater declines in resting energy expenditure. However, these differences are attenuated after 2-4 weeks of stabilization at the new, lower body weight, and do not affect the rate and amount of weight regain 9-33 months later (nor the tissue composition of regained weight). Differences in waist circumference, visceral and liver fat contents, resting blood pressure, fasting blood lipid profile, and insulin and adipokine concentrations in response to different rates of weight loss are trivial. The decline in fasting glucose concentration and the improvement in insulin sensitivity after 6-11% weight loss are both greater with rapid than gradual weight loss, but not different after 18-20% weight loss. Changes in body composition and metabolism after losing the same amount of body weight at different rates are largely similar, and occasional differences are likely not meaningful clinically for the long-term management of obesity and cardiometabolic diseases.

The Feasibility of a Fast Liver MRI Protocol for Lesion Detection of Adults at 3.0-T

Purpose

To investigate the feasibility of a fast liver magnetic resonance imaging (MRI) protocol for lesion detection in adults using 3.0-T MRI.

Methods

A fast liver MRI exam protocol was proposed. The protocol included motion-resistant coronal T2-w sequence, axial T2-w fast spin echo sequence with fat suppression, axial in-op phase gradient recalled echo (GRE) T1, axial diffusion weighted imaging (DWI), and axial contrast-enhanced T1 sequences. To evaluate the diagnostic capacity of the proposed protocol, 31 consecutive patients (20 males and 11 females; mean age, 53.2 years) underwent a liver MRI exam with conventional sequences, including the proposed protocol as a subset. Images from the conventional protocol and extracted abbreviated protocol were independently read, and the diagnostic concordance rate was assessed for each patient. The concordance analysis is presented as the proportion of concordant cases between the two protocols.

Results

The net measurement time of the fast liver MRI protocol without adjustment and waiting time were 4 min and 28 s. In the 31 patients included in this study, 139 suspicious findings were found from both the conventional liver MR protocol and the fast liver MRI protocol. The diagnostic concordance rate was 96.4%.

Conclusions

The fast liver MRI protocol is feasible at 3.0-T, with a shorter exam time and high diagnostic concordance compared to the conventional liver MRI workflow.

Fast versus gradual adaptation of soft monthly contact lenses in neophyte wearers

AIM

To determine if a gradual adaptation period is necessary for neophytes when fitted with modern hydrogel or silicone hydrogel reusable disposable contact lenses.

METHOD

Across four sites, 74 neophytes (18-28 years) were randomly assigned to a reusable lens cleaned nightly with Opti-Free® Puremoist® multi-purpose contact lens solution: Proclear® (hydrogel) or Biofinity® (silicone hydrogel) and an adaptation schedule: fast (10 h wear from the first day) or gradual (4 h on the first day, increasing their wear time by 2 h on each subsequent day until they had reached 10 h). Masked investigators graded ocular surface physiology and non-invasive tear breakup time (NIBUT) and a range of comfort, vision and lens handling subjective ratings (0-100 visual analogue scales) were recorded at the baseline visit and after 10 h of lens wear, 4-6 days and 12-14 days after lens fitting. Subjective scores were also repeated after 7 days.

RESULTS

There was no difference (p > 0.05) in ocular surface physiology or NIBUT between fast and gradual adaptation groups at any time point in either lens type with the exception of increased corneal staining (p = 0.019) in the silicone hydrogel fast adaptation group after 4-6 days, but was similar by 12-14 days. Subjective scores were also similar across the visits and lens types with the exception of 'lens awareness' (p = 0.019) which was less in the gradual versus the fast adaptation silicone hydrogel lens group at 12-14 days.

CONCLUSION

There seems to be no clinical benefit for recommending a gradual adaptation period in new wearers fitted with modern soft reusable disposable contact lenses. The findings of this work add to a growing body of evidence suggesting that such advice is unnecessary in regular soft contact lens wear, which has important ramifications for the initial clinical management of these patients.

Eating disorder diagnosis and the female athlete: A longitudinal analysis from college sport to retirement

OBJECTIVES

Female athletes experience eating disorders (EDs) at clinical, and subclinical, levels; most studies have determined point-prevalence rates through cross-sectional methodologies. To date, few studies have examined the long-term stability of EDs in female athletes; none extend into retirement.

DESIGN

A longitudinal investigation of ED classification (i.e., Clinical ED, Subclinical ED, Healthy) and weight control behaviors (e.g., vomiting, laxative use) from when athletes actively competed (T1) into their retirement (T2).

METHODS

Participants included U.S. female athletes (N=193) who were collegiate competitors (T1) and eventually were retired from their collegiate sports six years later (T2).

RESULTS

At T2, athletes were classified as Healthy (69.9%), Subclinical ED (26.9%), and Clinical ED (3.1%). Overall percentage of Subclinical EDs increased from 18.7% (T1) to 26.9% (T2); 52.8% of T1 Subclinical ED athletes continued to meet criteria for either Subclinical or Clinical ED at T2. Of the 13 Clinical ED athletes at T1, six (46.2%) continued to meet criteria for either a subclinical or clinical ED at T2. Though exercising (2+ hours/day; n=8, 4.1%) and dieting/fasting (4+ times/year; n=14, 7.3%) were the most frequently used weight control behaviors at T2, rates were substantially lower than at T1.

CONCLUSIONS

Retirement does not result in immediate remittance of eating concerns among female athletes; many continue or develop Subclinical and Clinical ED symptoms. Thus, addressing healthy body image and nutrition when athletes are competing is imperative to assist prevention and intervention efforts that may alleviate ED symptoms as athletes transition from sport.

Pluripotent stem cell-derived skeletal muscle fibers preferentially express myosin heavy-chain isoforms associated with slow and oxidative muscles

BACKGROUND

Skeletal muscle function is essential for health, and it depends on the proper activity of myofibers and their innervating motor neurons. Each adult muscle is composed of different types of myofibers with distinct contractile and metabolic characteristics. The proper balance of myofiber types is disrupted in most muscle degenerative disorders, representing another factor compromising muscle function. One promising therapeutic approach for the treatment of these diseases is cell replacement based on the targeted differentiation of pluripotent stem cells (PSCs) towards the myogenic lineage. We have previously shown that transient induction of Pax3 or Pax7 in PSCs allows for the generation of skeletal myogenic progenitors endowed with myogenic regenerative potential, but whether they contribute to different fiber types remains unknown.

RESULTS

Here, we investigate the fiber type composition of mouse PSC-derived myofibers upon their transplantation into dystrophic and non-dystrophic mice. Our data reveal that PSC-derived myofibers express slow and oxidative myosin heavy-chain isoforms, along with developmental myosins, regardless of the recipient background. Furthermore, transplantation of the mononuclear cell fraction re-isolated from primary grafts into secondary recipients results in myofibers that maintain preferential expression of slow and oxidative myosin heavy-chain isoforms but no longer express developmental myosins, thus indicating postnatal composition.

CONCLUSIONS

Considering oxidative fibers are commonly spared in the context of dystrophic pathogenesis, this feature of PSC-derived myofibers could be advantageous for therapeutic applications.

Energy Metabolism and Intermittent Fasting: The Ramadan Perspective

Intermittent fasting (IF) has been gaining popularity as a means of losing weight. The Ramadan fast (RF) is a form of IF practiced by millions of adult Muslims globally for a whole lunar month every year. It entails a major shift from normal eating patterns to exclusive nocturnal eating. RF is a state of intermittent liver glycogen depletion and repletion. The earlier (morning) part of the fasting day is marked by dominance of carbohydrate as the main fuel, but lipid becomes more important towards the afternoon and as the time for breaking the fast at sunset (iftar) gets closer. The practice of observing Ramadan fasting is accompanied by changes in sleeping and activity patterns, as well as circadian rhythms of hormones including cortisol, insulin, leptin, ghrelin, growth hormone, prolactin, sex hormones, and adiponectin. Few studies have investigated energy expenditure in the context of RF including resting metabolic rate (RMR) and total energy expenditure (TEE) and found no significant changes with RF. Changes in activity and sleeping patterns however do occur and are different from non-Ramadan days. Weight changes in the context of Ramadan fast are variable and typically modest with wise inter-individual variation. As well as its direct relevance to many religious observers, understanding intermittent fasting may have implications on weight loss strategies with even broader potential implications. This review examines current knowledge on different aspects of energy balance in RF, as a common model to learn from and also map out strategies for healthier outcomes in such settings.

Prospective gating control for highly efficient cardio-respiratory synchronised short and constant TR MRI in the mouse

PURPOSE

Cardiac and respiratory motion derived image artefacts are reduced when data are acquired with cardiac and respiratory synchronisation. Where steady state imaging techniques are required in small animals, synchronisation is most commonly performed using retrospective gating techniques but these invoke an inherent time penalty. This paper reports the development of prospective gating techniques for cardiac and respiratory motion desensitised MRI with significantly reduced minimum scan time compared to retrospective gating.

METHODS

Prospective gating incorporating the automatic reacquisition of data corrupted by motion at the entry to each breath was implemented in short TR 3D spoiled gradient echo imaging. Motion sensitivity was examined over the whole mouse body for scans performed without gating, with respiratory gating, and with cardio-respiratory gating. The gating methods were performed with and without automatic reacquisition of motion corrupted data immediately after completion of the same breath. Prospective cardio-respiratory gating, with acquisition of 64 k-space lines per cardiac R-wave, was used to enable whole body DCE-MRI in the mouse.

RESULTS

Prospective cardio-respiratory gating enabled high fidelity steady state imaging of physiologically mobile organs such as the heart and lung. The automatic reacquisition of data corrupted by motion at the entry to each breath minimised respiratory motion artefact and enabled a highly efficient data capture that was adaptive to changes in the inter-breath interval. Prospective cardio-respiratory gating control enabled DCE-MRI to be performed over the whole mouse body with the acquisition of successive image volumes every 12-15 s at 422 μm isotropic resolution.

CONCLUSIONS

Highly efficient cardio-respiratory motion desensitised steady state MRI can be performed in small animals with prospective synchronisation, centre-out phase-encode ordering, and the automatic reacquisition of data corrupted by motion at the entry to each breath. The method presented is robust against spontaneous changes in the breathing rate. Steady state imaging with prospective cardio-respiratory gating is much more efficient than with retrospective gating, and enables the examination of rapidly changing systems such as those found when using DCE-MRI.

Data set of healthy old people assessed for three walking conditions using accelerometric and opto-electronic methods

BACKGROUND

Gait patterns of healthy aging are needed to allow a comparison with pathological situations. However, little data is available.

OBJECTIVE

To present gait pattern of healthy older specially selected to be "healthy walkers".

METHOD

Fifty-seven older people benefited from a geriatric assessment including clinical and functional evaluations to include only those without gait disorders. Gait data were simultaneously recorded using a tri-axial accelerometer placed on the waist and four 3D position markers placed on the feet at the level of the heel and the toe. Volunteers walked at comfortable self-selected speed (CW), fast self-selected speed (FW), and finally in dual task walking condition (DTW). The extracted gait parameters were: gait speed, stride length, stride frequency, regularity and symmetry, swing, stance and double support time and ratio and minimum toe clearance. Gait speed and stride length were normalized to the right leg length.

RESULTS

Fifty-seven older people with a mean age of 69.7 ± 4.2 years old (range from 65 to 82 years) were included. Data were analyzed according to the gender and according to the age (<70 or ≥70 years old). After normalization to leg length, the main significant differences were shown for stride length and minimum toe clearance in CW, FW and in DTW that were shorter in women. The regularity in FW was significantly lower among older volunteers.

CONCLUSIONS

This work provides a data set considering 14 gait parameters obtained from 57 healthy old people strictly selected and assessed for three walking conditions and shows that GS, SL and MTC have to be related to the gender. The age-related impact on gait performances appears reduced in this cohort.

A nonrandomized controlled clinical pilot trial on 8 wk of intermittent fasting (24 h/wk)

OBJECTIVE

The aim of the study was to evaluate whether intermittent fasting (IF) is an effective preventive measure, and whether it is feasible for healthy volunteers under every day conditions.

METHODS

A nonrandomized controlled clinical trial on IF was performed with healthy volunteers over a period of 8 wk, and a subsequent 4-mo follow-up. Outcomes were assessed at baseline, after 8 wk, and after 6 mo. Volunteers who were not interested in fasting served as a control group. Participants in the fasting group were asked to continue their regular nutritional habits on the nonfasting days, whereas the control group maintained their habitual nutrition throughout the whole period. Outcomes included changes of metabolic parameters (insulin, glucose, insulin resistance, insulin-like growth factor-1, brain-derived neurotropic factor, lipids, liver enzymes, hemoglobin A1c) and coagulation markers; bioelectrical impedance analysis; body mass index; abdominal girth; blood pressure; general quality of life (five-item World Health Organization Well-Being Index [WHO-5] questionnaire), as well as mood and anxiety (Hospital Anxiety and Depression Scale [HADS], Profile of Mood States, Flourishing-Scale, visual analog scale, Likert scales). The intervention consisted of a fasting day, which was repeated every week for 8 wk, with abstinence from solid food between 00:00 and 23:59 at minimum and a maximum caloric intake of 300 kcal on each fasting day. A per-protocol analysis was performed. P < 0.05 was considered significant.

RESULTS

Thirty-six volunteers were included; 22 allocated themselves to the fasting group, and 14 to the control group. Thirty-three data sets were included in the final analysis. Although significant in-group changes were observed in both groups for a number of outcomes after 8 wk and 6 mo, no significant between-group differences were observed for any outcome other than overall body fat mass after 8 wk as well as for the HADS total score and the WHO-5 total score after 6 mo, all in favor of the fasting group. However, none of the between-group differences were clinically relevant.

CONCLUSIONS

We did not find any clinically relevant differences between groups in this controlled clinical pilot trial of 8 wk of IF in healthy volunteers. Further clinical research in this field is warranted to further analyze mechanisms and effects of IF.

Fast removal of tetracycline from wastewater by reduced graphene oxide prepared via microwave-assisted ethylenediamine-N,N'-disuccinic acid induction method

A green reagent of ethylenediamine-N,N'-disuccinic acid (EDDS) was reported herein for reduction of graphene oxide (GO) with microwave assistance. The characteristics of EDDS reduced graphene oxide (ERG), and the tetracycline (TC) adsorption behavior of ERG was investigated. The results showed that the deoxygenation efficiency of GO strongly depended on the EDDS amount and the ERG can be successively obtained by recycled EDDS. The ERG obtained at EDDS/GO ratio of 5 (ERG5) exhibited a maximum capacity of 558.66 mg/g for TC adsorption, which is superior to GO and ERGs obtained at other EDDS/GO ratio. The adsorption reached equilibrium within 10 min, and the driving forces are likely the van der Waals forces, π-π electron-donor-acceptor (EDA) interaction and cation-π bonding between TC and the ERG surface. The adsorbent dose, pH, temperature, initial TC concentration, and ionic strength significantly affect the TC adsorption. The pseudo-second-order kinetics describes TC adsorption process very well, with correlation coefficients (R (2) ) greater than 0.99. The adsorption isotherm was best fitted by Freundlich equation, followed by Langmuir, Temkin, and Hill model equations. Analysis on adsorption thermodynamics shows that the adsorption is a spontaneous endothermic process. The ERG could be a cost-effective and promising sorbent for TC wastewater treatment due to its high-efficiency performance in real river water, medical wastewater, and municipal wastewater.

Measuring Chitinase and Protease Activity in Cultures of Fungal Entomopathogens

Entomopathogenic fungi produce a variety of destructive enzymes and metabolites to overcome the unique defense mechanisms of insects. In a first step, fungal chitinases and proteinases need to break down the insect's cuticle. Both enzyme classes support the infection process by weakening the chitin barrier and by producing nutritional cleavage products for the fungus. In a second step, the pathogen can now mechanically penetrate the weakened cuticle and reach the insect's hemolymph where it starts proliferating. The critical enzymes chitinase and proteinase are also excreted into the supernatants of fungal cultures and can be used as indicators of virulence. Chromogenic assays adapted for 96-well microtiter plates that measure these enzymes provide a sensitive, fast, and easy screening method for evaluating the potential biocontrol activity of fungal isolates and may be considered as an alternative to laborious and time-consuming bioassays. Furthermore, monitoring fungal enzyme production in dependence of time, nutrient sources, or other factors can facilitate in establishing optimal growth and harvesting conditions for selected isolates with the aim of achieving maximum biocontrol activity.

Endogenous glucose production increases in response to metformin treatment in the glycogen-depleted state in humans: a randomised trial

AIMS/HYPOTHESIS

Metformin is believed to reduce glucose levels primarily by inhibiting hepatic glucose production. Recent data indicate that metformin antagonises glucagon-dependent glucose output, suggesting that compensatory mechanisms protect against hypoglycaemia. Here, we examined the effect of metformin on glucose metabolism in humans after a glycogen-depleting fast and the role of reduced-function alleles in OCT1 (also known as SLC22A1).

METHODS

In a randomised, crossover trial, healthy individuals with or without reduced-function alleles in OCT1 were fasted for 42 h twice, either with or without prior treatment with 1 g metformin twice daily. Participants were recruited from the Pharmacogenomics Biobank of the University of Southern Denmark. Treatment allocation was generated by the Good Clinical Practice Unit, Odense University Hospital, Denmark. Variables of whole-body glucose metabolism were assessed using [3-(3)H]glucose, indirect calorimetry and measurement of substrates and counter-regulatory hormones. The primary outcome was endogenous glucose production (EGP).

RESULTS

Thirty-seven individuals were randomised. Thirty-four completed the study (12 had none, 13 had one and nine had two reduced-function alleles in OCT1). Three were excluded from the analysis because of early dropout. Metformin significantly stimulated glucose disposal rates and non-oxidative glucose metabolism with no effect on glucose oxidation. This increase in glucose utilisation was explained by a concomitant increase in glycolytic flux and accompanied by increased EGP, most likely mediated by increased plasma lactate, glucagon and cortisol levels. There was no effect of reduced-function OCT1 alleles on any of these measures. All individuals completed the glycogen-depleting fast without hypoglycaemia.

CONCLUSIONS/INTERPRETATION

Metformin stimulates glycolytic glucose utilisation and lactate production in the glycogen-depleted state. This may trigger a rise in glucose counter-regulatory hormones and subsequently an increase in EGP, which protects against hypoglycaemia.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01400191 FUNDING: Danish Research Council for Health and Disease (0602-02695B) and Odense University Hospital Free Research Fund, 2012.

Bioaccumulation of hydroxylated polychlorinated biphenyls and pentachlorophenol in the serum of northern elephant seal pups (Mirounga angustirostris)

Northern elephant seals (NES) (Mirounga angustirostris) from the Año Nuevo State Reserve (CA, USA) were sampled at 1-, 4-, 7- and 10-week post-weaning. Concentrations of hydroxylated polychlorinated biphenyls (HO-PCBs) and their parent PCBs were measured in the serum of each individual. The ΣHO-PCB concentrations in the serum increased significantly between early and late fast (from 282 ± 20 to 529 ± 31 pg/mL). This increase might result from a mobilisation of HO-PCBs transferred from the mother during gestation and/or lactation and stored in the pup's liver. Food deprivation has been shown to exacerbate biotransformation capacities in mammals, birds and fish. The HO-penta-CBs was the predominant homologue group, followed by HO-hexa-CBs and HO-hepta-CBs. No preferential pathway for the metabolism of HO-PCBs (HO-direct insertion or NIH-shift of a chlorine atom) could be evidenced. The concentrations of pentachlorophenol (PCP) in the serum of weaned NES increased from 103 ± 7 pg/mL at early fast to 246 ± 41 pg/mL at late fast, which is within the range of PCP concentrations usually encountered in marine mammals.

Corticosterone, food intake and refueling in a long-distance migrant

Elevated baseline corticosterone levels function to mobilize energy in predictable life-history stages, such as bird migration. At the same time, baseline corticosterone has a permissive effect on the accumulation of fat stores (fueling) needed for migratory flight. Most migrants alternate flight bouts with stopovers, during which they replenish the fuel used during the preceding flight (refueling). The role of corticosterone in refueling is currently unclear. In a fasting-re-feeding experiment on northern wheatears (Oenanthe oenanthe) in autumn we found that baseline total and free corticosterone levels were negatively related with both food intake and the rate of fuel deposition after fasting. This confirms our earlier findings in wild conspecifics in spring and indicates that corticosterone does not stimulate stopover refueling. Whether the negative relationship between baseline corticosterone level and fuel deposition rate is causal is questionable, because within-individual comparison of corticosterone metabolite levels in droppings did not reveal differences between refueling and control periods. In other words, corticosterone does not appear to be down-regulated during refueling, which would be expected if it directly hampers refueling. We discuss possible correlates of corticosterone level that may explain the negative association between corticosterone and stopover refueling. Additionally, we found that fasting decreases total corticosterone level, which contrasts with previous studies. We propose that the difference is due to the other studies being conducted outside of the migration life-history stage, and provide a possible explanation for the decrease in corticosterone during fasting in migrating birds.