Chronic fatigue syndrome: Abnormally fast muscle fiber conduction in the membranes of motor units at low static force load.

OBJECTIVE: Chronic fatigue syndrome (CFS) and fibromyalgia (FM) are disorders of unknown etiology and unclear pathophysiology, with overlapping symptoms of - especially muscular -fatigue and pain. Studies have shown increased muscle fiber conduction velocity (CV) in the non-painful muscles of FM patients. We investigated whether CFS patients also show CV abnormalities. METHODS: Females with CFS (n = 25), with FM (n = 22), and healthy controls (n = 21) underwent surface electromyography of the biceps brachii, loaded up to 20% of maximum strength, during short static contractions. The mean CV and motor unit potential (MUP) velocities with their statistical distribution were measured. RESULTS: The CV changes with force differed between CFS-group and both FM-group and controls (P = 0.01). The CV of the CFS-group increased excessively with force (P < 0.001), whereas that of the controls increased only slightly and non-significantly, and that of the FM-group did not increase at all. In the CFS-group, the number of MUPs conveying very high conduction velocities increased abundantly with force and the MUPs narrowed. CONCLUSION: Our results suggest disturbed muscle membrane function in CFS patients, in their motor units involved in low force generation. Central neural deregulation may contribute to this disturbance. SIGNIFICANCE: These findings help to detangle the underlying mechanisms of CFS.

Fibromyalgia: Increased reactivity of the muscle membrane and a role of central regulation.

OBJECTIVE: Fibromyalgia (FM) is characterized by widespread muscle pain and central neural deregulation. Previous studies showed increased muscle fiber conduction velocity (CV) in non-painful muscles of FM patients. This study investigates the relationship between central activation and the CV in FM. METHODS: Twenty-two females with primary FM and 21 controls underwent surface electromyography of the non-painful biceps brachii. Mean CVs were calculated from the motor unit potential velocities (CV-MUPs), and the CV-MUPs' statistical distributions were presented as histograms. The amount of muscle activity (average rectified voltage, ARV) was measured. RESULTS: The CV was higher in the FM-group than in the controls (P = 0.021), with CV-MUPs generally shifted to higher values, indicative of increased muscle membrane propagation speeds. The largest increase in the CV of the FM-group occurred when adopting and maintaining a limb position at only 5% of maximum strength (P < 0.001); the CV did not, as normal, increase with greater force. However, the ARV in both groups similarly increased with force. CONCLUSIONS: In fibromyalgia patients, the muscle membrane propagation speed increases independently of the force load or amount of muscle activity produced. When adopting a limb position, the patients show an augmented muscle membrane reaction, suggesting deregulation from higher neural centers. SIGNIFICANCE: These findings contribute to understanding fibromyalgia.

Paired Analysis of Outcomes After Kidney Transplantation in Peritoneal and Hemodialysis Patients.

BACKGROUND: The impact of dialysis modality before kidney transplantation (hemodialysis or peritoneal dialysis) on outcomes is not clear. In this study we retrospectively analyzed the impact of dialysis modality on posttransplant follow-up. METHODS: To minimize donor bias, a paired kidney analysis was applied. One hundred thirty-three pairs of peritoneal dialysis (PD) and hemodialysis (HD) patients were transplanted at our center between 1994 and 2016. Those who received kidneys from the same donor were included in the study. HD patients were significantly older (44 vs 48 years), but the Charlson Comorbidity Index was similar (3.12 vs 3.46) in both groups. The groups did not differ significantly with respect to immunosuppressive protocols and number of mismatches (2.96 vs 2.95). RESULTS: One-year patient (98% vs 96%) and graft (90% vs 93%) survival was similar in the PD and HD patient groups. The Kaplan-Meier curves of the patients and graft survival did not differ significantly. Delayed graft function (DGF) and acute rejection (AR) occurred significantly more often in the HD recipients. Graft vessel thrombosis resulting in graft loss occurred in 9 PD (6.7%) and 4 HD (3%) patients (P > .05). Serum creatinine concentration and estimated glomerular filtration rate (using the Modification of Diet in Renal Disease guidelines) showed no difference at 1 month, 1 year, and at final visit. On multivariate analysis, factors significantly associated with graft loss were graft vessel thrombosis, DGF, and graft function 1 month after transplantation. On univariate analysis, age, coronary heart disease, and graft loss were associated with death. Among these factors, only coronary heart disease (model 1) and graft loss were significant predictors of death on multivariate analysis. CONCLUSION: The long-term outcome for renal transplantation is similar in patients with PD and HD. These groups differ in some aspects, however, such as susceptibility to vascular thrombosis in PD patients, and to DGF and AR in HD patients.

Risk of Skin Diseases in Maintenance Hemodialysis.

INTRODUCTION: Maintenance hemodialysis (HD) patients are potential transplant recipients. One of the most common cancers in the population of kidney recipients is skin neoplasm. Skin infections are also of a particular importance. In this population, especially in patients on the transplant waiting list, full dermatological examination, including dermatoscopy, should be carried out routinely. MATERIALS AND METHODS: The research was comprised of 105 HD patients (57 men, 48 women) with a mean age of 60.8 (range 25-94) years. The patients' skin condition was assessed and a dermatoscopic examination was performed. We compared the incidence of skin diseases in the two subpopulations: HD patients (n = 89) and HD patients active on the transplant waiting list (n = 16). RESULTS: Bacterial, fungal, and viral infections in the group of HD patients occurred in 24.7%, 14.6%, and 6.7% of patients, respectively. In HD patients on the waiting list, bacterial skin diseases were reported in 12.5% of patients, and neither fungal nor viral infections were noticed. Malignant skin lesions and precancerous conditions, such as basal cell carcinoma and keratosis actinic, developed in 4.5% and 3.4% of the HD patients. These malignancies did not occur in HD patients on the waiting list. The results show proper qualification for transplantation in maintenance HD patients before the waiting list. In the group of dialysis patients, 67.4% required dermatological care, while in the HD waiting group only 12.5% required dermatological care. CONCLUSIONS: The presented results prove the necessity of performing dermatological examinations on HD patients. Some dermatological skin lesions, if not diagnosed and treated, could progress to cancer after organ transplantation.

Level of Education and Knowledge of Skin Cancer Risk Factors in Patients Undergoing Maintenance Hemodialysis.

INTRODUCTION: An increased risk of skin cancer is particularly important in patients undergoing maintenance hemodialysis (HD), who are potential transplant recipients. In transplant recipients who are exposed to immunosuppressive therapy, neoplastic skin disease my take a more aggressive course. Increased exposure to photoradiation, elderly age, a low skin phototype, sunburn during childhood, and a history of smoking are the main factors contributing to the development of skin neoplasms. Knowledge of these risk factors as well as education on sun protection should be important for such patients. PATIENTS AND METHODS: We studied 105 HD patients (57 men, 48 women) with a mean age of 60.8 (range 25-94) years. Knowledge of skin cancer risk factors was assessed on the basis of a questionnaire regarding skin cancer risk factors. RESULTS: In the study group, 23.8% of patients claimed that they frequently and intensively engage in sunlight exposure. However, only 11.4% have started to apply sunblockers recently. Sunburn during adolescence was reported by 12.4% patients. Among the patients studied, 65.7% had skin phototype I or II, and only 34.3% had phototype III. In the investigated study group, 55.2% admitted smoking: 30.5% smoked more than 20 pack-years. Among the patients studied only 2.86% could name 3 skin cancer risk factors, 29.5% 2 risk factors, 60% 1 risk factor, and 7.6% could not name any risk factor. CONCLUSIONS: The results presented prove that patients undergoing HD lack knowledge regarding skin cancer risk factors, which explains the necessity of education, particularly on the dangers of sun radiation.

Do Patients With End-Stage Chronic Renal Failure Treated With the Use of Hemodialysis Have Healthy Skin? Evaluation of Skin Lesions and Basic Education About Risk Factors for Skin Cancer in This Patient Population.

BACKGROUND: Considering the increasing incidence of skin cancers in patients after renal transplantation, evaluation of skin condition in dialysis patients, from whom kidney transplant recipients are recruited, appears to be very important. Particular importance is attached to the identification of such dialysis patients in the population who require dermatologic care before qualifying for transplantation. The objective of this study was to determine the prevalence of skin diseases in the dialysis patient population. Education of the patients regarding risk factors for skin cancer and the need for sun protection was performed. METHODS: Full dermatologic examination, including dermatoscopy, was performed on a group of 77 dialysis patients (38 women, 39 men) and a control group of 77 healthy people (60 women, 17 men). RESULTS: Eight hemodialysis patients had healthy skin compared with 33 people from the control group. In the remaining hemodialysis patients, the following skin lesions were observed: 1) inflammatory and allergic skin disorders in 17 patients; 2) bacterial, fungal, and viral infections in 26 patients; 3) benign lesions in 39 patients; 4) malignant skin lesions and precancerous conditions in 4 patients; and 5) other skin changes in 63 patients. CONCLUSIONS: Skin lesions are common in the dialysis patient population. Only 10% of the examined population had completely healthy skin, compared with 43% of the control group. More than one-half of dialysis patients required dermatologic care compared with one-third of healthy control subjects.

Gastrointestinal Pathologies in Patients After Successful Renal Transplantation-A Pilot Study.

BACKGROUND: The beneficial effect of kidney transplantation in patients requiring continuous renal replacement therapy owing to chronic kidney disease is well known and accepted. Kidney transplantation protects the patient from complications that may develop during chronic dialysis. Unfortunately, there is also evidence that kidney transplant patients are more prone to developing cancer than healthy persons. The aim of this study was to evaluate the prevalence of gastrointestinal pathologies in patients after kidney transplantation. METHODS: Adult patients after kidney transplantation, who are under the care of the Outpatient Department of Nephrology in Gdansk, received alarm symptom questionnaires and referral for testing for the presence of fecal occult blood. Then, in 45 selected patients (29 men and 16 women) endoscopic examination was performed. Mean age was 57.6 ± 10.1 (range, 35-83) years. RESULTS: Out of ∼940 patients after kidney transplantation, resting under supervision of outpatient department, 181 patients completed the questionnaire and 100 gave a stool sample for testing: 32 results were positive. After analyzing the questionnaires and stool results, 88 patients were qualified for further investigation. The endoscopic examination had been performed so far in 45 patients and revealed gastritis and/or duodenitis in 33 patients, diverticular colon disease in 18, esophagitis in 8, colon polyps in 14, stomach polyps in 3, inflammatory bowel disease in 7, and cancers in 3. CONCLUSIONS: The preliminary results indicate that patients after kidney transplantation have significant risk of gastrointestinal pathologies and require detailed diagnostic endoscopy.

Venus Flytrap HKT1-Type Channel Provides for Prey Sodium Uptake into Carnivorous Plant Without Conflicting with Electrical Excitability.

The animal diet of the carnivorous Venus flytrap, Dionaea muscipula, contains a sodium load that enters the capture organ via an HKT1-type sodium channel, expressed in special epithelia cells on the inner trap lobe surface. DmHKT1 expression and sodium uptake activity is induced upon prey contact. Here, we analyzed the HKT1 properties required for prey sodium osmolyte management of carnivorous Dionaea. Analyses were based on homology modeling, generation of model-derived point mutants, and their functional testing in Xenopus oocytes. We showed that the wild-type HKT1 and its Na(+)- and K(+)-permeable mutants function as ion channels rather than K(+) transporters driven by proton or sodium gradients. These structural and biophysical features of a high-capacity, Na(+)-selective ion channel enable Dionaea glands to manage prey-derived sodium loads without confounding the action potential-based information management of the flytrap.

Pregnancy after kidney transplantation: a single-center experience and review of the literature.

After kidney transplantation (KT), pregnancy is possible, although the risk of maternal and fetal complications is much higher than in the general population. Outcome of 22 pregnancies in 17 patients transplanted in the Gdansk center in the period 1980-2012 was studied. Mean maternal age at pregnancy was 30 ± 5 (range, 23-39) years, interval between transplantation and conception 3.4 ± 2.5 (range, 0.6-11) years. Mean creatinine concentration before conception was 1.29 ± 0.36 (range, 0.8-2.45) mg/dL and was stable during 1 year preceding pregnancy (mean increase, 0.01 mg/dL). Nine of the 17 patients received 1 and 4 received ≥2 antihypertensive drugs, and 1 had proteinuria. Twelve of the 17 patients were primagravidas, 1 was pregnant 3 times, and 14 times. At the time of conception, 20 patients received CNI (14 cyclosporine, 6 tacrolimus), 15 antimetabolites (3 mycophenolate mofetil [MMF], 12 azathioprine), 1 mammalian target of rapamycin inhibitor (mTORi; sirolimus), and all prednisone. MMF and mTORi were discontinued before or during the 1st weeks of pregnancy. Maternal outcome: all survived the pregnancy. None experienced rejection or graft loss as a direct result of pregnancy. Maternal complications included edema (5/17), worsening of blood pressure control (5/17), and worsening (1/17) or new onset of proteinuria (2/17). Mean creatinine decrease during pregnancy was 0.06 mg/dL. Mean creatinine 1 year after pregnancy was 1.49 ± 0.53 mg/dL. There were 12 cesarean sections. Fetal outcomes: 17 live births (2 with serious congenital defects), 2 spontaneous and 1 induced abortion, 2 stillbirths. Mean pregnancy age and neonate birth weights were 35 ± 4 (range, 23-39) weeks and 2,552 ± 629 (range, 1,480-3,420) g, respectively. During mean 8.5 (range, 1-25) years of follow-up after pregnancy, 4/17 patients lost grafts. Grafts were lost in the 3rd to 7th years after pregnancy. We conclude that pregnancy does not exert a direct negative influence on patient and graft survivals; 68% of all pregnancies resulted in delivering healthy neonates.

Open prospective study to evaluate cardiovascular risk factors and renal function in 2 dosage regimens of tacrolimus combined with mycophenolate mofetil and steroids in renal transplant patients: 5-year results.

BACKGROUND: Cyclosporine and tacrolimus (TAC) are the most potent immunosuppressants. TAC is considered less nephrotoxic, but may be an important factor in chronic graft dysfunction. The aim of the study was to evaluate kidney function and cardiovascular risk profile in 2 groups of low immunological risk kidney allograft recipients receiving 2 TAC dosages. MATERIALS AND METHODS: Patients were randomly assigned to 2 TAC-based treatments (group I [n = 14], standard dose; group II [n = 15], reduced dose). Patient and graft survival, graft function, occurrence of cardiovascular events (cardiac death, myocardial infarction, stroke), incidence of new-onset diabetes mellitus after transplantation, and cardiovascular risk factors were assessed over a 5-year period. RESULTS: Patient demographics and transplant characteristics were not statistically different between groups. TAC trough levels were significantly higher in group I for 24 months post transplant. Patient survival did not differ, but there were more acute rejection episodes and graft losses in group II. There were no significant differences in the rate of cardiac events. Graft function measured as serum creatinine levels and calculated glomerular filtration rate did not differ between groups. The same applies to new-onset diabetes mellitus after transplantation incidence. Office blood pressures were numerically higher in group I up to 24 months but this difference did not reach significance at any time. Similar results were obtained for serum lipids. CONCLUSIONS: Immunosuppression based on low doses of tacrolimus seems to be safe in the group of low immunological risk patients but in the 60-month follow-up does not offer any clear benefits in terms of potential nephrotoxicity or cardiovascular risk.

The efficacy and safety of valganciclovir vs. oral ganciclovir in the prevention of symptomatic CMV infection in children after solid organ transplantation.

Routine prophylaxis for CMV with valganciclovir is common in adult recipients but data to support its use in children are scarce. The aim of this study was to compare the efficacy and safety of valganciclovir vs. ganciclovir in a pediatric cohort. We performed a retrospective analysis of 92 children after KTx and/or LTx. All children have received IV ganciclovir for two wk, and then oral ganciclovir (TID; n = 41) before 2004, or valganciclovir (OD; n = 51) thereafter. Treatment was given for three months in R+/D+ or R+/D- recipients and for six months in R-/D+. Patients were followed for one yr post transplant. Both groups were comparable in their demographic and transplant-related history. Symptomatic CMV infection/disease developed in 13.7% vs. 19.5% of valganciclovir and ganciclovir groups, respectively (P-NS). Time-to-onset of CMV infection was comparable in both groups (P-NS); rates of acute allograft rejection were similar in both groups (3.9% vs. 9.8%). Risk factors for CMV infection included young age, serostatus of R-/D+, and allograft from cadaver donor. No significant side effects were noted in both groups. As in adults, valganciclovir appears to be as efficacious and safe as oral ganciclovir. Valganciclovir should be considered as a possible prophylactic treatment for CMV in pediatric recipients of KTx or LTx.

Effects of the flaxseed lignans secoisolariciresinol diglucoside and its aglycone on serum and hepatic lipids in hyperlipidaemic rats.

The present study involved a comparative analysis of the effects of purified flaxseed lignans, secoisolariciresinol diglucoside (SDG) and its aglycone metabolite (SECO), in hyperlipidaemic rats. For hypercholesterolaemia, female Wistars (six rats per group) were fed a standard or 1 % cholesterol diet and orally administered 0, 3 or 6 mg SDG/kg or 0, 1.6 or 3.2 mg SECO/kg body weight once daily for 4 weeks. Hypertriacylglycerolaemia was induced in male Sprague-Dawley rats (ten rats per group) by supplementing tap water with 10 % fructose. These rats were orally administered 0, 3 or 6 mg SDG/kg body weight once daily for 2 weeks. Fasting blood samples (12 h) were collected predose and at the end of the dosing period for serum lipid analyses. Rats were killed and livers rapidly excised and sectioned for lipid, mRNA and histological analyses. Chronic administration of equimolar amounts of SDG and SECO caused similar dose-dependent reductions in rate of body-weight gain and in serum total and LDL-cholesterol levels and hepatic lipid accumulation. SDG and SECO failed to alter hepatic gene expression of commonly reported regulatory targets of lipid homeostasis. SDG had no effect on serum TAG, NEFA, phospholipids and rate of weight gain in 10 % fructose-supplemented rats. In conclusion, our data suggest that the lignan component of flaxseed contributes to the hypocholesterolaemic effects of flaxseed consumption observed in humans. Future studies plan to identify the biochemical mechanism(s) through which flaxseed lignans exert their beneficial effects and the lignan form(s) responsible.

Distribution of motor unit potential velocities in short static and prolonged dynamic contractions at low forces: use of the within-subject's skewness and standard deviation variables.

Behaviour of motor unit potential (MUP) velocities in relation to (low) force and duration was investigated in biceps brachii muscle using a surface electrode array. Short static tests of 3.8 s (41 subjects) and prolonged dynamic tests (prolonged tests) of 4 min (30 subjects) were performed as position tasks, applying forces up to 20% of maximal voluntary contraction (MVC). Four variables, derived from the inter-peak latency technique, were used to describe changes in the surface electromyography signal: the mean muscle fibre conduction velocity (CV), the proportion between slow and fast MUPs expressed as the within-subject skewness of MUP velocities, the within-subject standard deviation of MUP velocities [SD-peak velocity (PV)], and the amount of MUPs per second (peak frequency=PF). In short static tests and the initial phase of prolonged tests, larger forces induced an increase of the CV and PF, accompanied with the shift of MUP velocities towards higher values, whereas the SD-PV did not change. During the first 1.5-2 min of the prolonged lower force levels tests (unloaded, and loaded 5 and 10% MVC) the CV and SD-PV slightly decreased and the MUP velocities shifted towards lower values; then the three variables stabilized. The PF values did not change in these tests. However, during the prolonged higher force (20% MVC) test, the CV decreased and MUP velocities shifted towards lower values without stabilization, while the SD-PV broadened and the PF decreased progressively. It is argued that these combined results reflect changes in both neural regulatory strategies and muscle membrane state.

Altered expression of SOCS3 in the hypothalamic arcuate nucleus during seasonal body mass changes in the field vole, Microtus agrestis.

We have previously shown that cold-acclimated (8 degrees C) male field voles (Microtus agrestis) transferred from short day (SD, 8 h light) to long day (LD, 16 h light) photoperiod exhibit an increase in body mass lasting 4 weeks, after which they stabilise at a new plateau approximately 7.5 g (24.8%) higher than animals maintained in SD. By infusing voles with exogenous leptin, we have also demonstrated that SD voles respond to the hormone by reducing body mass and food intake, whereas LD animals increasing body mass are resistant to leptin treatment. In the present study, we investigated whether seasonal changes in body mass could be linked to modulation of the leptin signal by suppressor of cytokine signalling-3 (SOCS3). We used in situ hybridisation to examine hypothalamic arcuate nucleus (ARC) expression of SOCS3, neuropeptide Y (NPY), agouti-related peptide (AgRP), pro-opiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART) genes in 90 voles exposed to either SD or LD for up to 11 weeks. LD voles increasing body mass had significantly higher levels of SOCS3 mRNA than SD or LD voles with a stable body mass. There were no associated changes in expression of NPY, AgRP, POMC and CART genes. These results suggest that voles that regulate body mass at either the lower (SD) or upper (LD) plateau remain sensitive to leptin action, whereas SOCS3-mediated leptin resistance is a short-term mechanism that enables animals to move between the stable body mass plateaus. Our data provide evidence that expression of SOCS3 in the ARC is involved in the modulation of the strength of the leptin signal to facilitate seasonal cycles in body mass and adiposity.

One-year observation of kidney allograft recipients converted from cyclosporine microemulsion to tacrolimus.

The results from previous trials suggested that tacrolimus-based treatment in kidney transplantation was associated with a significantly lower incidence of acute rejection, and that cyclosporine microemulsion (CsA-Me)-treated patients converted to tacrolimus had numerically better 6-year graft survival than those remaining on CsA-Me. Death with a functioning graft and chronic graft nephropathy are the leading causes of late allograft loss. While standard cardiovascular risk factors are relevant, renal function itself becomes an important risk factor for cardiovascular morbidity and mortality in kidney transplantation patients. Expected benefits of the conversion from CsA-Me to tacrolimus with respect to renal function and cardiovascular status were the rationale for this observational study. Twenty one patients underwent conversion due to nephrotoxicity of cyclosporine (n = 18) or side effects (n = 3). Two out of 21 patients did not complete the study. The patient survival after 1 year was 100% in this group of patients; graft survival 94.7%. No cases of de novo diabetes mellitus were identified. Mean serum creatinine fell from 2.13 +/- 0.4 to 1.84 +/- 0.3 mg/dL (P < .02) and calculated glomerular filtration rate increased from 49.6 +/- 14.4 to 56.2 +/- 15.5 mL/min (P < .01). Total cholesterol decreased from 229.4 +/- 50.1 to 195.9 +/- 28.5 mg/dL (P < .005) and, low-density lipoprotein cholesterol from 125.7 +/- 37.3 to 104.4 +/- 22.6 mg/dL (P < .02). No significant changes in mean systolic or diastolic pressure or blood glucose levels were observed. The results of this observational study showed that in a group of patients with raised creatinine levels at entry, conversion to tacrolimus resulted in improved graft function and a more favorable cardiovascular risk profile.

Photoperiod regulates leptin sensitivity in field voles, Microtus agrestis.

We have previously shown that cold-acclimated (8 degrees C) male field voles (Microtus agrestis) transferred from short (SD, 8:16 h L:D) to long photoperiod (LD, 16:8 h L:D) exhibit increases in body mass, adiposity and food intake. To assess whether these increases were associated with decreased leptin sensitivity, we infused LD and SD voles with physiological doses of murine leptin (or saline) delivered peripherally for 7 days via mini-osmotic pumps. Measurements were made of body mass (weight-reducing effect of leptin), food intake (anorectic effect of leptin) and gene expression of uncoupling protein 1 (UCP1) in brown adipose tissue (BAT) (thermogenic effect of leptin). The SD animals were sensitive to the weight-reducing effects of leptin (mean body mass decrease of 1.2 g over 7 days) and appetite-reducing effect of leptin (mean food intake decrease of 2.5 g over 7 days), whereas LD voles were resistant to the hormone treatment. The switch from a leptin-sensitive to leptin-resistant state appears to act as a desensitisation mechanism that allows voles transferred from SD to LD to ignore elevated leptin levels generated by increased body fat and accumulate adipose tissue without stimulating compensatory changes opposing the weight gain. Neither SD nor LD voles responded to infusion of leptin by changes in BAT UCP1 gene expression, suggesting dissociation of anorectic and thermogenic effects of leptin, possibly related to chronic cold exposure. Our results indicate that cold-acclimated voles show photoperiod-regulated changes in leptin sensitivity and may provide an attractive model for elucidating molecular mechanisms of leptin resistance.

Effect of photoperiod on body mass, food intake and body composition in the field vole, Microtus agrestis.

Many small mammals respond to seasonal changes in photoperiod by altering body mass and adiposity. These animals may provide valuable models for understanding the regulation of energy balance. Here, we present data on the field vole (Microtus agrestis) - a previously uncharacterised example of photoperiod-induced changes in body mass. We examined the effect of increased day length on body mass, food intake, apparent digestive efficiency, body composition, de novo lipogenesis and fatty acid composition of adipose tissue in cold-acclimated (8 degrees C) male field voles by transferring them from a short (SD, 8 h:16 h L:D) to long day photoperiod (LD, 16 h:8 h L:D). During the first 4 weeks of exposure to LD, voles underwent a substantial increase in body mass, after which the average difference between body masses of LD and SD voles stabilized at 7.5 g. This 24.8% increase in body mass reflected significant increases in absolute amounts of all body components, including dry fat mass, dry lean mass and body water mass. After correcting body composition and organ morphology data for the differences in body mass, only gonads (testes and seminal vesicles) were enlarged due to photoperiod treatment. To meet energetic demands of deposition and maintenance of extra tissue, voles adjusted their food intake to an increasing body mass and improved their apparent digestive efficiency. Consequently, although mass-corrected food intake did not differ between the photoperiod groups, the LD voles undergoing body mass increase assimilated on average 8.4 kJ day(-1) more than animals maintained in SD. The majority (73-77%) of the fat accumulated as adipose tissue had dietary origin. The rate of de novo lipogenesis and fatty acid composition of adipose tissue were not affected by photoperiod. The most important characteristics of the photoperiodic regulation of energy balance in the field vole are the clear delineation between phases where animals regulate body mass at two different levels and the rate at which animals are able to switch between different levels of energy homeostasis. Our data indicate that the field vole may provide an attractive novel animal model for investigation of the regulation of body mass and energy homeostasis at both organism and molecular levels.

Global transcriptional analysis of the phosphate starvation response in Sinorhizobium meliloti strains 1021 and 2011.

The global response to phosphate starvation was analysed at the transcriptional level in two closely related strains of Sinorhizobium meliloti, Rm1021 and Rm2011. The Pho regulon is known to be induced by PhoB under conditions of phosphate limitation. Ninety-eight genes were found to be significantly induced (more than three-fold) in a phoB -dependent manner in phosphate-stressed cells, and phoB -independent repression of 86 genes was observed. Possible roles of these genes in the phosphate stress response are discussed. Twenty new putative PHO box sequences were identified in regions upstream of 17 of the transcriptional units that showed phoB -dependent, or partially phoB -dependent, regulation, indicating direct regulation of these genes by PhoB. Despite the overall similarity between the phosphate stress responses in Rm1021 and Rm2011, lower induction rates were found for a set of phoB -dependent genes in Rm1021. Moreover, Rm1021 exhibited moderate constitutive activation of 12 phosphate starvation-inducible, phoB -dependent genes when cells were grown in a complex medium. A 1-bp deletion was observed in the pstC ORF in Rm1021, which results in truncation of the protein product. This mutation is probably responsible for the expression of phosphate starvation-inducible genes in Rm1021 in the absence of phosphate stress.

Photoperiodic effects on body mass, energy balance and hypothalamic gene expression in the bank vole.

We examined the effect of increasing photoperiod, at a constant low temperature, on the body mass and energy budget of the bank vole Clethrionomys glareolus. Simultaneously, we determined the hypothalamic gene expression of neuropeptides and receptors known to be involved in short-term energy balance. Despite an increase in body mass (approximately 10% of initial mass), we found no significant changes in any energetic parameters (food intake, energy assimilation rate, resting metabolic rate and total daily energy expenditure by doubly-labelled water). Apparent energy assimilation efficiency was higher in voles exposed to long-days (LD) compared to short-days (SD). Surprisingly, gene expression of corticotrophin releasing factor (CRF; in the paraventricular nucleus), and the melanocortin-3 receptor (in the arcuate nucleus), both known to be involved in appetite suppression and elevation of energy expenditure in short-term energy balance, were higher in voles kept in LD compared to SD. CRF expression was also elevated in females compared to males. These paradoxical data suggest an alternative mechanism for the control of seasonal body mass changes compared to short-term body mass changes, and between male and female voles. Furthermore, they highlight the need for studies to perform simultaneous measurements at both the molecular and whole animal levels.