Bluegill growth as modified by plant density: an exploration of underlying mechanisms

Summary Bluegill (Lepomis macrochira) growth varies inconsistently with plant density. In laboratory and field experiments, we explored mechanisms underlying bluegill growth as a function of plant and invertebrate density. In the laboratory, bluegills captured more chironomids (Chironomus riparius) than damselflies (Enallagma spp. and Ischnura spp.), but energy intake per time spent searching did not differ between damselfly and chironomid treatments. From laboratory data, we described prey encounter rates as functions of plant and invertebrate density. In Clark Lake, Ohio, we created 0.05-ha mesocosms of inshore vegetation to generate macrophyte densities of 125, 270, and 385 stems/m² of Potamogeton and Ceratophyllum and added 46-mm bluegill (1/m²). In these mesocosms, invertebrate density increased as a function of macrophyte density. Combining this function with encounter rate functions derived from laboratory data, we predicted that bluegill growth should peak at a high macrophyte density, greater than 1000 stems/m², even though growth should change only slightly beyond 100 stems/m². Consistent with our predictions, bluegills did not grow differentially, nor did their use of different prey taxa differ, across macrophyte densities in the field. Bluegills preferred chironomid pupae, which were relatively few in numbers but vulnerable to predation, whereas more cryptic, chironomid larvae, which were associated with vegetation but were relatively abundant, were eaten as encountered. Bluegills avoided physid snails, which were abundant. Contrary to previous work, vegetation did not influence growth or diet of bluegill beyond relatively low densities owing to the interaction between capture probabilities and macroinvertebrate densities.The unit is sponsored jointly by the United States Fish and Wildlife Service, Ohio Department of Natural Resources, The Ohio State University, and The Wildlife Management Institute     

Channel structures in synthetic polypeptides with alternating configurations. Conformational analysis of poly(DL-proline)

Theoretical conformational analysis of L,D alternating sequences of poly alpha-amino acids is reported in connection with the ability of naturally occurring peptide and depsipeptide having alternating configurations to increase selectively the ion permeability across membranes. The most stable structures of poly(DL-proline), of which the conformational variability is practically limited to the choice between cis and trans conformations of the peptide bonds, were characterized. The all-trans conformation results in a flat helical structure possessing the main features for acting as an ion channel across membranes as actually found experimentally. Random cis-trans conformational sequences provide an alternative mechanism of ion transport intermediate between the ion channel and the ion carrier.     

Serum Reference Values for Leptin in Healthy Infants

ObjectiveReports on leptin concentrations in pediatric populations lack reference values for infants in the first months of life. Our study was conducted on healthy full-term infants between 2002 and 2012 to determine serum leptin reference values in subjects less than 18 months old.MethodsRoutine outpatient blood tests for serum leptin were performed on 317 infants using a radioimmunoassay method. The median and 10^th–90^th percentiles were calculated to obtain reference values using quantile regression. Values established in this study were compared with another independent cohort of 110 infants.ResultsThe median (IQR) serum leptin concentration in the infants was 2.37 (3.26) ng/ml (n = 317). The median leptin concentration was 2.81 (3.49) ng/ml (n = 202) in infants younger than 6 months of age, 1.44 (2.27) ng/ml (n = 59) in infants between 6–12 months of age and 1.77 (2.05) ng/ml (n = 56) in infants between 12–18 months of age. We obtained leptin reference values based on age by estimating the lower and upper percentiles. In the entire cohort, the median (IQR) leptin concentration was 2.22 (3.11) ng/ml in males (n = 168) and 2.60 (3.32) ng/ml in females (n = 149). According to the type of feeding median serum leptin concentration was higher in breast-fed infants (n = 188) than in formula-fed infants (n = 129) (2.63 (3.34) ng/ml vs. 2.12 (2.77) ng/ml; p<0.05).ConclusionsOur data revealed no gender difference in leptin concentration in early infancy. After 6 months of life, leptin concentrations decreased slightly. We used a large cohort to confirm that breast-fed infants had significantly higher serum leptin levels than formula-fed infants during the first 6 months of life, although this difference disappeared later in life. In this study, we defined the leptin reference range in healthy infants in the first 18 months of life according to the Clinical and Laboratory Standards Institute (CLSI).     

Predictive markers of clinical outcome in the GRMD dog model of Duchenne muscular dystrophy

In the translational process of developing innovative therapies for DMD (Duchenne muscular dystrophy), the last preclinical validation step is often carried out in the most relevant animal model of this human disease, namely the GRMD (Golden Retriever muscular dystrophy) dog. The disease in GRMD dogs mimics human DMD in many aspects, including the inter-individual heterogeneity. This last point can be seen as a drawback for an animal model but is inherently related to the disease in GRMD dogs closely resembling that of individuals with DMD. In order to improve the management of this inter-individual heterogeneity, we have screened a combination of biomarkers in sixty-one 2-month-old GRMD dogs at the onset of the disease and a posteriori we addressed their predictive value on the severity of the disease. Three non-invasive biomarkers obtained at early stages of the disease were found to be highly predictive for the loss of ambulation before 6 months of age. An elevation in the number of circulating CD4⁺CD49d^hi T cells and a decreased stride frequency resulting in a reduced spontaneous speed were found to be strongly associated with the severe clinical form of the disease. These factors can be used as predictive tests to screen dogs to separate them into groups with slow or fast disease progression before their inclusion into a therapeutic preclinical trial, and therefore improve the reliability and translational value of the trials carried out on this invaluable large animal model. These same biomarkers have also been described to be predictive for the time to loss of ambulation in boys with DMD, strengthening the relevance of GRMD dogs as preclinical models of this devastating muscle disease.KEY WORDS: GRMD, DMD, Dystrophin, Dog, Predictive biomarker, Lymphocyte, CD49d, Gait analysis, Accelerometry     

Extracellular matrix distribution and islet morphology in the early postnatal pancreas: anomalies in the non-obese diabetic mouse

Previously, we reported elevated numbers of macrophages in the pancreas of NOD mice, a spontaneous animal model for T1D, during the early postnatal period. Extracellular matrix plays an important role in the tissue trafficking and retention of macrophages as well as in postnatal pancreas development. Therefore, we have examined the expression and distribution of laminin and fibronectin, two major extracellular matrix proteins and their corresponding integrin receptors, in the pre-weaning pancreases of NOD mice and control mouse strains. In addition, we have characterized the pancreas morphology during this period, since the morphology of the pre-weaning pancreas before the onset of lymphocytic peri-insulitis, when the pancreas is still subject to developmental changes, has been poorly documented. We show that laminin labeling is mainly associated with exocrine tissue, whereas fibronectin labeling was mostly localized at the islet-ductal pole, islet periphery and in intralobular septa. Moreover, the protein expression level of fibronectin was increased in NOD pancreases at the early stage of postnatal development, as compared to pancreases of C57BL/6 and BALB/c mouse strains. Interestingly, pancreatic macrophages were essentially found at sites of intense fibronectin labeling. The increased fibronectin content in NOD neonatal pancreas coincided with altered islet morphology, histologically reflected by enlarged and irregular shaped islets and increased percentages of total endocrine area as compared to that of control strains. In conclusion, increased levels of the extracellular matrix protein fibronectin were found in the early postnatal NOD pancreas, and this is associated with an enhanced accumulation of macrophages and altered islet morphology.This work was supported by the Centre Nationale de la Recherche Scientifique, Université Paris V and grants from the 5th PCRD MONODIAB.     

Thymic hormone-containing cells. VIII. Effects of colchicine, cytochalasin B, and monensin on secretion of thymulin by cultured human thymic epithelial cells

The intracellular pathway for secretion of thymulin, a thymic hormone, was studied in primary cultures of human thymic epithelial cells by experimentally blocking the movement of secretory vesicles within these cells. These cultures were subjected to cytoskeleton inhibitors, such as colchicine and/or cytochalasin B, that block the directed movement of secretory vesicles, or to monensin, an ionophore that specifically perturbs the traffic of Golgi-derived vesicles. Both cytoskeleton inhibitors partially prevented thymulin secretion into the culture supernatants, and their effects were dose-dependent. Moreover, the percentage of thymulin-containing cells (evaluated by immunofluorescence with a zinc-specific anti-thymulin monoclonal antibody), as well as the fluorescence intensity within these cells, was significantly higher than observed in control cultures, suggesting that the hormone was accumulated in the cytoplasm, thus facilitating its detection. Similar results were obtained with monensin. These results, together with the recent identification of high molecular weight proteins reacting with anti-thymulin antibodies, suggest that thymulin is secreted via the following intracellular pathway: a precursor is synthesized at the level of the granular endoplasmic reticulum; it migrates to the Golgi complex, from which it is released within hormone-containing vesicles; the vesicles incorporate zinc, move towards the cell membrane, and eventually fuse with it. This sequence of events characterizes the classical phenomenon of exocytosis.     

Selective binding of actinomycin D induces a reversible conformational transition of nucleosomes

Equilibrium and hydrodynamic studies on the complex of actinomycin D with H1-H5 depleted, 175 basepair nucleosomes are reported. By spectral titration the intrinsic affinities of actinomycin D for nucleosomes and for DNA are found strictly comparable. Sedimentation analysis shows that actinomycin can apparently unfold the nucleosome, like ethidium bromide and daunomycin, but it does so at a much lower bound drug to DNA molar ratio (about 1 drug molecule to 45 basepairs). Since about four bound actinomycin molecules are able to induce the reversible conformational transition of a nucleosome, it is suggested that the sites of interaction may correspond to the kinked DNA sites evidenced by Klug and collaborators (Richmond, T.J., Finch, J.T., Rushton, B., Rhodes, D. and Klug, A. (1984) Nature 311, 532-537) in the structure of the nucleosome. A relevance of these findings to the interaction of actinomycin with "active chromatin" is also suggested.     

A theoretical method to predict DNA permutation gel electrophoresis from the sequence.

The gel electrophoretic permutation assays of DNA fragments experimentally investigated by different authors were theoretically reproduced using our theoretical model of sequence-dependent curvature. The general pattern of agreement obtained suggests that our method can be usefully adopted as an alternative to the experimental assay, in particular where the lack of a sufficient number of unique restriction sites in the fragment prevents the correct localization of the main bend site.     

Influence of storage conditions on MALDI‐TOF MS profiling of gingival crevicular fluid: Implications on the role of S100A8 and S100A9 for clinical and proteomic based diagnostic investigations

Gingival crevicular fluid (GCF) may be a source of diagnostic biomarkers of periodontitis/gingivitis. However, peptide fingerprints may change, depending on GCF collection, handling and storage. We evaluated how storage conditions affect the quality and the reproducibility of MALDI‐TOF profiles of this fluid. GCF was collected on paper strips from four subjects with healthy gingiva. Our findings demonstrated that sample storage conditions significantly affect GCF peptide pattern over time. Specifically, the storage of GCF immediately extracted from paper strips generates less variations in molecular profiles compared to the extraction performed after the storage. Significant spectral changes were detected for GCF samples stored at –20°C directly on the paper strips and extracted after three months, in comparison to the freshly extracted control. Noteworthy, a significant decrease in the peak area of HNP‐3, S100A8, full‐length S100A9 and its truncated form were detected after 3 months at –80°C. The alterations found in the “stored GCF” profile not only may affect the pattern‐based biomarker discovery but also make its use not adequate for in vitro diagnostic test targeting S100A8, S100A9 proposed as potential diagnostic biomarkers for periodontal disease. In summary, this study shows that the best preserved signatures were obtained for the GCF samples eluted in trifluoroacetic acid and then immediately stored at –80°C for 1 month. The wealth of information gained from our data on protein/patterns stability after storage might be helpful in defining new protocols which enable optimal preservation of GCF specimen.