Common origin and evolution of glycosyltransferases using Dol-P-monosaccharides as donor substrate

On the basis of the analysis of 64 glycosyltransferases from 14 species we propose that several successive duplications of a common ancestral gene, followed by divergent evolution, have generated the mannosyltransferases and the glucosyltransferases involved in asparagine-linked glycosylation (ALG) and phosphatidyl-inositol glycan anchor (PIG or GPI), which use lipid-related donor and acceptor substrates. Long and short conserved peptide motifs were found in all enzymes. Conserved and identical amino acid positions were found for the alpha 2/6- and the alpha 3/4-mannosyltransferases and for the alpha 2/3-glucosyltransferases, suggesting unique ancestors for these three superfamilies. The three members of the alpha 2-mannosyltransferase family (ALG9, PIG-B, and SMP3) and the two members of the alpha 3-glucosyltransferase family (ALG6 and ALG8) shared 11 and 30 identical amino acid positions, respectively, suggesting that these enzymes have also originated by duplication and divergent evolution. This model predicts a common genetic origin for ALG and PIG enzymes using dolichyl-phospho-monosaccharide (Dol-P-monosaccharide) donors, which might be related to similar spatial orientation of the hydroxyl acceptors. On the basis of the multiple sequence analysis and the prediction of transmembrane topology we propose that the endoplasmic reticulum glycosyltransferases using Dol-P-monosaccharides as donor substrate have a multispan transmembrane topology with a first large luminal conserved loop containing the long motif and a small cytosolic conserved loop containing the short motif, different from the classical type II glycosyltransferases, which are anchored in the Golgi by a single transmembrane domain.     

Honeybees assess changes in nectar flow within a single foraging bout

Forager honeybees returning to the hive after a successful foraging trip unload the collected liquid to recipient hivemates through mouth-to-mouth food exchange contacts (trophallaxis). The speed at which the liquid is transferred (unloading rate) from donor to recipient is related to the profitability offered by the recently visited food source. Two of the main characteristics that define food source profitability are the flow of solution delivered by the feeder and the time invested by the forager feeding at the source (feeding time). To investigate which of these two variables is related to unloading rate, we individually trained donor foragers to a regulated-flow feeder that presented changes in the delivered flow of solution within a single foraging bout, while feeding time remained constant. With the range of flows used, bees attained maximum crop loads in all experiments. During the subsequent trophallactic encounter with an unfed recipient hivemate, unloading rate was differentially affected by the changes in flow of solution presented during the previous foraging trip at the source, depending on whether there had been an increase or a decrease of flow rate within that visit. Foragers unloaded at lower rates when they experienced a decrease in flow rate, but did not increase the unloading rate when presented with an increase at the food source. Thus, forager honeybees seem to be able to detect variations in the delivered flow of solution, since they modulate unloading rate in relation to these changes, although decreases in food value seem to be perceptually weighted in relation to increases, independently of the time invested in the food-gathering process.     

The X-ray structure of ferric Escherichia coli flavohemoglobin reveals an unexpected geometry of the distal heme pocket

The x-ray structure of ferric unliganded lipid-free Escherichia coli flavohemoglobin has been solved to a resolution of 2.2 A and refined to an R-factor of 19%. The overall fold is similar to that of ferrous lipid-bound Alcaligenes eutrophus flavohemoglobin with the notable exception of the E helix positioning within the globin domain and a rotation of the NAD binding module with respect to the FAD-binding domain accompanied by a substantial rearrangement of the C-terminal region. An inspection of the heme environment in E. coli flavohemoglobin reveals an unexpected architecture of the distal pocket. In fact, the distal site is occupied by the isopropyl side chain Leu-E11 that shields the heme iron from the residues in the topological positions predicted to interact with heme iron-bound ligands, namely Tyr-B10 and Gln-E7, and stabilizes a pentacoordinate ferric iron species. Ligand binding properties are consistent with the presence of a pentacoordinate species in solution as indicated by a very fast second order combination rates with imidazole and azide. Surprisingly, imidazole, cyanide, and azide binding profiles at equilibrium are not accounted for by a single site titration curve but are biphasic and strongly suggest the presence of two distinct conformers within the liganded species.     

Cytoarchitectural features of Ucides cordatus (Crustacea Decapoda) hepatopancreas: structure and elemental composition of electron-dense granules

Hepatopancreal tissue of the crab Ucides cordatus was investigated by light and electron microscopy. The observed epithelial cells were: E-cells (embryonic), located in the distal portion of the hepatopancreal tubules, R-cells (resorptive) F-cells (fibrillar) and B-cells (blister or secretory), found in its intermediate and proximal regions. Two types of electron-dense granules (EDGs) were found frequently in the cells of the proximal portion of the hepatopancreal tubule. Both types of EDGs presented alternating concentric electron-dense and electron-lucent layers. In order to better characterize these granules, energy dispersive X-ray analysis (EDXA) and glucose-6-phosphatase (G6Pase) cytochemistry were performed. One type of spherical granule was seen inside vacuoles surrounded by an association of myelin-like membranes as well as some small membrane-bound vesicles. This type of granule neither presented detectable Ca and P on EDXA spectra nor G6Pase cytochemical reaction products. The second type of granule had O, P and Ca characteristic peaks. G6Pase cytochemical products were observed inside these structures and showed that this mineralized type was surrounded by endoplasmic reticulum membranes. This result suggests that in U. cordatus the endoplasmic reticulum is associated with the genesis of mineralized EDGs. While amorphous mineral granules may be associated with a storage of Ca and P for the new carapace synthesis, EDGs covered by the non-mineralized spherical multi-layered membranes may be associated with late endosomes. No specific secretory pathway however was determined for the EDGs at the epithelial proximal portion.     

Herding and snaking by the harem stallion in domestic herds

Four herds of pony mares, each consisting of a stallion and six mares, were used to characterize the nature of herding by the stallion and the factors that induced the herding behavior. Herding behaviors were compared among four successive treatments (six mares alone, stallion added, two new mares added, and entire herd moved to a new pasture). A new treatment was initiated every 7 days and behavior was studied for 5 consecutive days (Days 1-5) for each treatment. Observations were made every 10 min during a 2-h period for each day. The extent of herding was quantitated by the mean distances between mares. The extent of snaking (herding with the head and neck extended and ears held back) was scored 0, 1, 2, or 3 (nil, minimal, intermediate, and maximal, respectively). The mean distance among the original mares on Day 1 when the mares were alone was 5.0 mare lengths and was reduced (P < 0.05) to 1.9 mare lengths when the stallion was added. The mean distance among the original mares of an established stallion/mare herd (3.8 mare lengths) was reduced (P < 0.05) on the day the herd was moved to a new pasture (1.9 mare lengths), similar to the effect of the introduction of the stallion. Scores for the extent of snaking, as well as the extent of herding, were highest (P < 0.05) on Day 1 when the stallion was added or the stallion/mare herd was moved to a new pasture. The extent of herding and snaking decreased (P < 0.05) by Day 2 and was seen only occasionally on Days 3-5. The addition of new mares to the herd did not induce herding of the original mares. However, the new mares maintained mean distances of 8-12 mare lengths from the original mares, resulting primarily from chasing by the stallion. By Day 4, the distances between the new and original mares were not different (P > 0.05) from the distances among the original mares.     

Skeletal muscle mitochondrial free-fatty-acid content and membrane potential sensitivity in different thyroid states: involvement of uncoupling protein-3 and adenine nucleotide translocase

The effect of triiodothyronine (T3) on mitochondrial efficiency could be related to an increase in the concentrations of some proteins, such as uncoupling proteins (UCPs). Free fatty acids (FFA) seem to be a cofactor essential for the uncoupling activity of UCP3. In this paper, we report that the hypothyroidism-hyperthyroidism transition is accompanied by increases: (i) in the endogenous levels of mitochondrial FFA and (ii) in the sensitivity to FFA shown by the mitochondrial respiration rate and membrane potential, which correlated with the level of UCP3 protein. The level of the mRNA for adenine-nucleotide translocase-1 (ANT) was not affected by the thyroid state, while the ANT contribution to FFA-induced changes in mitochondrial uncoupling was low in the hypothyroid and euthyroid states but became more relevant in the hyperthyroid state at the highest concentration of FFA.     

Palaeoecology of Upper Pleistocene-Holocene bryozoan and foraminiferal assemblages from Ku?dili (Kadiköy, Istanbul, Turkey)

Bryozoan and foraminiferal assemblages from a core drilled in the Kusdili (Kadiköy, Istanbul) Upper Pleistocene-Holocene sequence were studied. Assemblages are absent from the very basal and top parts but they are well represented all along the middle part of the sequence. All the species found presently live in the Mediterranean. In the area sedimentation seemingly started about 13?000 years ago in very shallow near-shore environments with the deposition of pebbly sediments rapidly evolving to mud. Near the base, the presence of erosional surface allows to recognize three successive sedimentary cycles. Bryozoan and foraminiferal assemblages found in the middle part of the sequence testify to a shallow water, estuarine or lagoonal paleo-environment, in which effects of low salinity waters, more obvious toward the top, could be related to the reestablishment of a connection between the Marmara Sea and the Black Sea through the Bosphorus, about 7000 years BP.     

The Italian Twin Project: from the personal identification number to a national twin registry.

The unique opportunity given by the "fiscal code", an alphanumeric identification with demographic information on any single person residing in Italy, introduced in 1976 by the Ministry of Finance, allowed a database of all potential Italian twins to be created. This database contains up to now name, surname, date and place of birth and home address of about 1,300,000 "possible twins". Even though we estimated an excess of 40% of pseudo-twins, this still is the world's largest twin population ever collected. The database of possible twins is currently used in population-based studies on multiple sclerosis, Alzheimer's disease, celiac disease, and type 1 diabetes. A system is currently being developed for linking the database with data from mortality and cancer registries. In 2001, the Italian Government, through the Ministry of Health, financed a broad national research program on twin studies, including the establishment of a national twin registry. Among all the possible twins, a sample of 500,000 individuals are going to be contacted and we expect to enrol around 120,000 real twin pairs in a formal Twin Registry. According to available financial resources, a sub sample of the enrolled population will be asked to donate DNA. A biological bank from twins will be then implemented, guaranteeing information on future etiological questions regarding genetic and modifiable factors for physical impairment and disability, cancers, cardiovascular diseases and other age related chronic illnesses.     

Protective role of the complement regulatory protein human CD-55 in cardiac xenograft: a descriptive study and a revision of the literature

The limited and inadequate availability of organs from human donors has resulted in the utilisation of xenografts as an alternative tool. Nevertheless, hyperacute rejection (HAR) following xenograft determines the loss of the transplanted organ. The "primum movens" is the activation of the complement pathway mediated by the binding of natural xenogenic antibodies to the endothelium of the graft, followed by the lysis of the endothelial cells with subsequent oedema, thrombosis and necrosis of the transplanted organ. In this work we describe morphological and biomolecular observations of isolated human-decay accelerating factor (h-DAF, CD55) transgenic pig hearts, after perfusion for four hours with human blood. H-DAF is a membrane glycoprotein inhibiting the complement activation in humans. We describe considerably reduced damages in transgenic hearts, compared to controls. The cardiac function resulted preserved. Our data are in agreement with what was already shown by other groups using different experimental models. In conclusion, we encourage the use of new sources of transgenic animals, pointing out the importance of morphological analysis in evaluation of xenograft.     

A low-resolution 3D model of the tetrameric alcohol dehydrogenase from Sulfolobus solfataricus

We describe the computation of a model of the thermophilic NAD-dependent homotetrameric alcohol dehydrogenase from the archaeon Sulfolobus solfataricus (SsADH). Modeling is based on the knowledge that each monomer contains two Zn ions with catalytic and structural function, respectively. In the database of known structures, proteins with similar functions are either dimers containing two zinc ions per monomer or tetramers with one zinc ion per monomer. In any case, the sequence identity of the target to the possible templates is low. A threading procedure is therefore developed which includes constraints taking into account residue conservation both at the zinc ion binding and at the monomer-monomer interaction sites in the tetrameric unit. The model is consistent with previously reported data. Furthermore, cross-linking experiments are described which support the computed tetrameric model.