Physiological chromium determination in serum by zeeman graphite furnace atomic absorption spectrometry

Several authors have already underlined chromium implication in glucose and lipids metabolism of humans. In this field, physiological chromium determination in serum could be helpful, but the discrepancies reported in numerous papers are confusing. Here we report some results obtained by Zeeman correction Graphite Furnace Atomic Absorption Spectrometry: This technique includes a dilution of serum with 12.5 mM ultrapure nitric acid and 0.25% Triton X-100 (final concentrations). Some main features can be outlined: (1) the contamination constitutes a serious drawback and (2) the sensitivity of the technique is critical (characteristic mass found: 1.76 pg/0.0044 A.s). Our results obtained from 27 healthy subjects (2.01±0.77 nmol/L) agree with most recent studies and indicate that serum chromium level does not seem to be sex-related.     

Antimetastatic effect of immunomodulators from Nocardia opaca in mice and rats activation of peritoneal macrophages by these fractions

Summary Nocardia delipidated cell mitogen (NDCM), a particulate fraction prepared from Nocardia opaca, injected i.p. in an oil/water emulsion to F6 rhabdomyosarcoma-bearing rats, inhibited the development of pulmonary metastases; 6 out of 10 rats were protected. Repeated i.p. administration of emulsified NDCM and of two other compounds, a Nocardia water soluble mitogen (NWSM a hydrosoluble fraction) and purified cell walls (CW, an insoluble macromolecular fraction) in Lewis lung carcinoma (LLC)-bearing mice resulted in a significant reduction of lung metastases. The efficiency of these fractions was enhanced by association with monokines. A combination regimen of NDCM, NWSM, and CW (100 g/0.1 ml) and monokines (0.1 ml), injected i.p. in LLC-bearing mice, yielded a greater antimetastatic effect than either therapy alone. Peritoneal macrophages from mice which had been injected i.p. with NWSM or CW, when triggered either by TPA (tetradecanoyl phorbol acetate) or by zymosan, released large quantities of hydrogen peroxide and had a high rate of glucose consumption. These macrophages were activated as judged by their cytostatic activity against syngeneic P815 mastocytoma growth; they expressed biochemical markers which have been reported to characterize the activated state. Incubation of thioglycollate-elicited peritoneal macrophages with NWSM, and monokines for 72 h resulted in a cytotoxic activity against labeled LLC cells; addition of macrophage activating factor significantly increased the cytotoxic capacity of these macrophages. In view of this we postulate that the antimetastatic effect of soluble and insoluble N. opaca fractions and monokines might be mediated by activated peritoneal macrophages.     

Cell surface glycosaminoglycans of a tumor cell line and its DNA transfected variant differing in their lung colonizing potential

A highly lung-colonizing cell line RMS/8² was obtained by DNA transfection from a low lung-colonizing line RMS/8, a clone of a rat rhabdomyosarcoma cell line. The cells were metabolically labeled with³H-glucosamine and³⁵S-sulfate. The newly synthesized pericellular glycosaminoglycans and the ability of the cells from the two lines to degrade extracellular matrix components were studied comparatively. The following conclusions were obtained: 1) Thein vitro proliferation rate is not a determinant in the modulation of the colonizing potential of these cells; 2) The strongly colonizing RMS/8² cells release more radioactivity from the radiolabeled extracellular matrix than their weakly colonizing counterparts; 3) The cells with a high colonizing potential incorporated less radioactivity into the cell surface glycosaminoglycans, and exhibited a lower heparan sulfate to chondroitin sulfate ratio than the weakly colonizing RMS/8 line.     

A docking analysis of the statistical physics of protein-protein recognition

We describe protein-protein recognition within the frame of the random energy model of statistical physics. We simulate, by docking the component proteins, the process of association of two proteins that form a complex. We obtain the energy spectrum of a set of protein-protein complexes of known three-dimensional structure by performing docking in random orientations and scoring the models thus generated. We use a coarse protein representation where each amino acid residue is replaced by its Vorono? cell, and derive a scoring function by applying the evolutionary learning program ROGER to a set of parameters measured on that representation. Taking the scores of the docking models to be interaction energies, we obtain energy spectra for the complexes and fit them to a Gaussian distribution, from which we derive physical parameters such as a glass transition temperature and a specificity transition temperature.     

Functional variation among frugivorous birds: implications for rainforest seed dispersal in a fragmented subtropical landscape

Seed dispersal plays a critical role in rainforest regeneration patterns, hence loss of avian seed dispersers in fragmented landscapes may disrupt forest regeneration dynamics. To predict whether or not a plant will be dispersed in fragmented forests, it is necessary to have information about frugivorous bird distribution and dietary composition. However, specific dietary information for frugivorous birds is often limited. In such cases, information on the seed-crushing behaviour, gape width and relative dietary dominance by fruit may be used to describe functional groups of bird species with respect to their potential to disperse similar seeds. We used this information to assess differences in the seed dispersal potential of frugivorous bird assemblages in a fragmented rainforest landscape of southeast Queensland, Australia. The relative abundance of frugivorous birds was surveyed in extensive, remnant and regrowth rainforest sites (16 replicates of each). Large-gaped birds with mixed diets and medium-gaped birds with fruit-dominated diets were usually less abundant in remnants and regrowth than in continuous forest. Small-gaped birds with mixed diets and birds with fruit as a minor dietary component were most abundant in regrowth. We recorded a similar number of seed-crushing birds and large-gaped birds with fruit-dominated diets across site types. Bird species that may have the greatest potential to disperse a large volume and wide variety of plants, including large-seeded plants, tended to be less abundant outside of extensive forests, although one species, the figbird Sphecotheres viridis, was much more abundant in these areas. The results suggest that the dispersal of certain plant taxa would be limited in this fragmented landscape, although the potential for the dispersal of large-seeded plants may remain, despite the loss of several large-gaped disperser species.     

Validation of q-ball imaging with a diffusion fibre-crossing phantom on a clinical scanner

Magnetic resonance (MR) diffusion imaging provides a valuable tool used for inferring structural anisotropy of brain white matter connectivity from diffusion tensor imaging. Recently, several high angular resolution diffusion models were introduced in order to overcome the inadequacy of the tensor model for describing fibre crossing within a single voxel. Among them, q-ball imaging (QBI), inherited from the q-space method, relies on a spherical Radon transform providing a direct relationship between the diffusion-weighted MR signal and the orientation distribution function (ODF). Experimental validation of these methods in a model system is necessary to determine the accuracy of the methods and to optimize them. A diffusion phantom made up of two textile rayon fibre (comparable in diameter to axons) bundles, crossing at 90 degrees , was designed and dedicated to ex vivo q-ball validation on a clinical scanner. Normalized ODFs were calculated inside regions of interest corresponding to monomodal and bimodal configurations of underlying structures. Three-dimensional renderings of ODFs revealed monomodal shapes for voxels containing single-fibre population and bimodal patterns for voxels located within the crossing area. Principal orientations were estimated from ODFs and were compared with a priori structural fibre directions, validating efficiency of QBI for depicting fibre crossing. In the homogeneous regions, QBI detected the fibre angle with an accuracy of 19 degrees and in the fibre-crossing region with an accuracy of 30 degrees .     

A recent insertion of an alu element on the Y chromosome is a useful marker for human population studies

A member of the Alu family of repeated DNA elements has been identified on the long arm of the human Y chromosome, Yq11. This element, referred to as the Y Alu polymorphic (YAP) element, is present at a specific site on the Y chromosome in some humans and is absent in others. Phylogenetic comparisons with other Alu sequences reveal that the YAP element is a member of the polymorphic subfamily-3 (PSF-3), a previously undefined subfamily of Alu elements. The evolutionary relationships of PSF-3 to other Alu subfamilies support the hypothesis that recently inserted elements result from multiple source genes. The frequency of the YAP element is described in 340 individuals from 14 populations, and the data are combined with those from other populations. There is both significant heterogeneity among populations and a clear pattern in the frequencies of the insertion: sub-Saharan Africans have the highest frequencies, followed by northern Africans, Europeans, Oceanians, and Asians. An interesting exception is the relatively high frequency of the YAP element in Japanese. The greatest genetic distance is observed between the African and non-African populations. The YAP is especially useful for studying human population history from the perspective of male lineages.      

Cell surface glycosaminoglycans of rat rhabdomyosarcoma lines with different metastatic potentials and of non-malignant rat myoblasts

Glycosaminoglycans of cultured nickel-induced rat rhabdomyosarcoma cell lines with different metastatic potentials and of non-malignant myoblasts, grown in the presence or in the absence of hydrocortisone, were studied comparatively. The newly formed [3H]glucosamine-labelled cell surface proteoglycans and glycosaminoglycans were separated by ion exchange chromatography and partially characterized. The overall incorporation of the label in the glycosaminoglycan fractions and the average molecular weight of the heparan and of the chondroitin sulfate proteoglycans was lower in the malignant cells than in the non-malignant L6 myoblasts. The strongly metastatic 9-4/0 parental line and the 6 subline were relatively richer in chondroitin sulfate and poorer in dermatan sulfate labels than the very weakly metastatic 8 subline and the L6 myoblasts. Hyaluronic acid and heparan sulfate labels were inversely related to the metastatic capacity of the cell lines studied. Hydrocortisone treatment induced an increase in the cell surface chondroitin and dermatan sulfate labels in the case of the strongly metastatic lines, and a decrease of the same parameters in the case of the weakly metastatic 8 line.