Fate of parathyroid hormone during hemodialysis and ultrafiltration

In order to shed light on the discrepant changes in plasma immunoreactive parathyroid hormone (iPTH) during hemodialysis (HD) and ultrafiltration (UF) in end-stage renal failure, the influence of filtration of PTH fragments on the iPTH level in plasma was examined in 2 sets of experiments: in vitro dialysis of 125I-bPTH 1-84, 125I-hPTH 1-34 and 125I-hPTH 53-84 added to plasma was successively performed through a cuprophane membrane. Gel filtration on a Biogel P-100 column and subsequent counting of the eluate were performed with the plasma before and after dialysis, and with the dialysate fluid after dialysate fluid after dialysis. An ultrafiltrate obtained from a patient with renal failure was also analyzed for iPTH with a 'C-' and with an 'N-terminal' antiserum (GP 500 MA and AS 211/32), and so was his plasma before and after UF, and after a subsequent dialysis session. Fluid obtained by lavage of the filter with acetic acid after dialysis was also analyzed. Chromatography with measurements of iPTH in the eluate was performed in each case, and the procedure was repeated applying a different transmembrane pressure. Immunoreactive material found in the concentrated ultrafiltrate, but not in plasma, was characterized by means of dilution curves in different RIA performed with the C-terminal antiserum preincubated with various synthetic PTH fragments. Results showed that intact PTH does not cross the cuprophane membrane during both in vitro dialysis and in vivo UF. The 1-34 fragments are poorly dialyzed in vitro; either they stick to the membrane or they are disintegrated.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mycoplasma contamination of leukemic cell lines alters protein expression determined by reverse phase protein arrays

Mycoplasma contamination is a major problem in cell culturing, potentially altering the results of cell line-based experiments in largely uncharacterized ways. To define the consequences of mycoplasma infection at the level of protein expression we utilized the reverse phase protein array technology to analyze the expression of 235 proteins in mycoplasma infected, uninfected post treatment, and never-infected leukemic cell lines. Overall, protein profiles of cultured cells remained relatively stable after mycoplasma infection. However, paired comparisons for individual proteins identified that 18.7% of the proteins significantly changed between the infected and the never-infected cell line samples, and that 14.0% of the proteins significantly altered between the infected and the post treatment samples. Six percent of the proteins were affected in the post treatment samples compared to the never-infected samples, and 7.2% compared to treated cells that had never had mycoplasma infection before. Proteins that were significantly altered in the infected cells were enriched for apoptotic signaling processes and auto-phosphorylation, suggesting an increased cellular stress and a decreased growth rate. In conclusion, this study shows that mycoplasma infection of leukemic cell lines alters the proteins expression levels, potentially confounding experimental results. This reinforces the need for regular testing of mycoplasma.     

Long-term scatterhoarding by Eurasian red squirrels (Sciurus vulgaris)

Hoarding behavious, seed species hoarded and hoarding intensity by red squirrels ( Sclurus vulgaris L.) are described for two population; one in a coniferous woodland with few deciduous trees, the other in a mixed deciduous woodland with some conifers. Seasonal variation in the recovery of hoards and the importance of hoarded food with regard to a squirrel's annual energy demands are discussed. The importance of having hoards is compared among tree squirrel species.     

Pancreas-Specific Sirt1-Deficiency in Mice Compromises Beta-Cell Function without Development of Hyperglycemia

Aims/Hypothesis

Sirtuin 1 (Sirt1) has been reported to be a critical positive regulator of glucose-stimulated insulin secretion in pancreatic beta-cells. The effects on islet cells and blood glucose levels when Sirt1 is deleted specifically in the pancreas are still unclear.

Methods

This study examined islet glucose responsiveness, blood glucose levels, pancreatic islet histology and gene expression in Pdx1^Cre; Sirt1^ex4F/F mice that have loss of function and loss of expression of Sirt1 specifically in the pancreas.

Results

We found that in the Pdx1^Cre; Sirt1^ex4F/F mice, the relative insulin positive area and the islet size distribution were unchanged. However, beta-cells were functionally impaired, presenting with lower glucose-stimulated insulin secretion. This defect was not due to a reduced expression of insulin but was associated with a decreased expression of the glucose transporter Slc2a2/Glut2 and of the Glucagon like peptide-1 receptor (Glp1r) as well as a marked down regulation of endoplasmic reticulum (ER) chaperones that participate in the Unfolded Protein Response (UPR) pathway. Counter intuitively, the Sirt1-deficient mice did not develop hyperglycemia. Pancreatic polypeptide (PP) cells were the only other islet cells affected, with reduced numbers in the Sirt1-deficient pancreas.

Conclusions/Interpretation

This study provides new mechanistic insights showing that beta-cell function in Sirt1-deficient pancreas is affected due to altered glucose sensing and deregulation of the UPR pathway. Interestingly, we uncovered a context in which impaired beta-cell function is not accompanied by increased glycemia. This points to a unique compensatory mechanism. Given the reduction in PP, investigation of its role in the control of blood glucose is warranted.     

Comparing data of different survey methods for sustainable wildlife management in hunting areas: the case of Tarangire–Manyara ecosystem,northern Tanzania

Cost–benefit considerations of wildlife monitoring are essential, particularly, in areas outside national park boundaries, where resources for conducting wildlife censuses are scarce, but that, at the same time, are subject to high pressure for wildlife utilization, such as hunting. Large mammal survey data from various sources were collated and analyzed to investigate which methods are best suited for monitoring purposes at low cost in the Tarangire–Manyara ecosystem, northern Tanzania. Our results indicate that primary data (from aerial and road transects counts) that involve direct species observations, although sometimes very expensive, are required for establishing the status of the target species in terms of density or population size. Concomitantly, secondary data from various sources, such as interviews, hunting quota, and damage reports, obtained over wide areas and over longer periods of time, can provide important information on presence/absence and distribution of species within an area. In addition, the study revealed that hunting quotas set did not correlate with species abundance/numbers from the primary data surveys for most of the large mammals hunted within the ecosystem. For a better conservation and management of wildlife, in particular with respect to the forthcoming formation of Wildlife Management Areas, we propose an integrated approach to wildlife monitoring using primary and secondary data sources through the involvement of local people’s knowledge.     

Effects of spatio-temporal variation in food supply on red squirrel Sciurus vulgaris body size and body mass and its consequences for some fitness components

Food availability is likely to influence body condition and, in turn, fitness. The intensity of this response may vary between populations of the same species on a small spatial and temporal scale. We used 5 yr of data from 6 Eurasian red squirrel Sciurus vulgaris populations from the southern Alps to explore differences in body size and body mass among neighbouring populations, in relation to habitat type and variation in food supply. We also investigated sexual dimorphism in these traits and whether phenotypic variation affects local survival and female reproductive success. Mean hind foot length, a measure of body size, did not differ between sexes but differed between areas. Seasonal variation in body mass was small with no evidence for fattening in autumn. Females were slightly heavier than males, but this difference was largely explained by mass gain of females during reproduction. The size of conifer seed crops, the major food supply, varied strongly over years and between habitats, but this variation corresponded only weakly with autumn body mass. Differences in size and mass between populations were partially explained by habitat‐related differences in body size and variability of seed‐crops, suggesting differential selection for smaller squirrels in spruce‐larch forests against selection for larger and heavier animals in mixed broadleaves and conifer forests and in Scots pine forests with more stable seed production. The probability of reproduction by females increased with body mass, but varied strongly between habitats and years, with more females reproducing in years with rich seed‐crops. In both sexes, body mass positively affected probability of settlement and length of residency. Our results suggest that in temporally variable environments that differ in overall amount of food resources, individual variation in body mass is related to habitat type, and that having a relatively high body mass, within each population, positively affects male and female settlement success and local survival, and female reproductive success.     

Visceral fat is a determinant of PAI-1 activity in diabetic and non-diabetic overweight and obese women.

Plasminogen activator inhibitor type 1 (PAI-1), an inhibitor of fibrinolysis and an important and independent cardiovascular risk factor, has been shown to be elevated in obesity and type 2 diabetes. Recent study results have suggested that adipose tissue--visceral fat in particular--could play an important role in the fibrinolytic process.In order to assess the specific role of this fat distribution, we measured PAI-1 activity (AU/ml) and visceral fat (CT-scan at level L4-L5) in 2 groups of 30 overweight and obese diabetic and overweight and obese non-diabetic women. Subjects were matched for age, weight, body mass index, fat mass and total abdominal fat. Visceral adipose tissue and PAI-1 were significantly higher in diabetic women (p = 0.022 and p = 0.004 respectively) than in non-diabetic patients. Visceral fat correlated significantly with PAI-1 activity, even after correction for insulin and triglycerides (r = 0.28, p = 0.034). Stepwise regression analysis showed visceral fat as the most important determinant factor for PAI-1 in the whole group and in the non-diabetic group. In the diabetic group, fasting insulin was the most important determinant. These results show that visceral fat is more important than BMI or total body fat in the determination of PAI-1 levels. Furthermore, the increased amount of visceral fat in type 2 diabetics may contribute to the increase of PAI-1 activity levels and the subsequent increased risk for thrombovascular disease, regardless of BMI and total fatness.     

The structural unit of the thiazide-sensitive NaCl cotransporter is a homodimer

The thiazide-sensitive NaCl cotransporter (NCC) is responsible for the reabsorption of 5% of the filtered load of NaCl in the kidney. Mutations in NCC cause Gitelman syndrome. To gain insight into its regulation, detailed information on the structural composition of its functional unit is essential. Western blot analysis of total membranes of Xenopus laevis oocytes heterologously expressing FLAG-tagged NCC revealed the presence of both complex-(140-kDa) and core (100-kDa)-glycosylated monomers and a broad band of high molecular mass (250-350-kDa) complexes. Chemical cross-linking with dithiobispropionimidate eliminated the low molecular weight bands and increased the intensity of the high molecular weight bands, indicating that NCC is present in multimeric complexes. Co-expression of HA- and FLAG-tagged NCC followed by co-immunoprecipitation demonstrated that these multimers contained at least two complex-glycosylated NCC proteins. The dimeric nature of the multimers was further substantiated by sucrose gradient centrifugation yielding a peak of approximately 310 kDa. A concatameric construct of two NCC polyproteins exhibited significant 22Na+ uptake, indicating that the transporter is functional as a homodimer. A concatamer of partially retarded G980R- and wild type (wt)-NCC displayed normal Na+ transport. This demonstrates that G980R-NCC, provided that it reaches the surface, is fully active and that wt-NCC is dominant in its association with this mutant. Conversely a concatamer of fully retarded G741R- and wt-NCC did not reach the cell surface, showing that wt-NCC is recessive in its association with this mutant. Oocytes co-expressing G741R- and wt-NCC did not show G741R staining at the plasma membrane, whereas Na+ transport was normal, indicating that wt-NCC dimerizes preferentially with itself. The results are discussed in relation to the recessive nature of NCC mutants in Gitelman syndrome.