The NC1 dimer of human placental basement membrane collagen IV: does a covalent crosslink exist?

Triple-helical collagen IV protomers associate through their N- and C-termini, forming a three-dimensional network that provides basement membranes with mechanical strength. Within this network, the C-terminal non-collagenous (NC1) domains form tight dimeric junctions. Crystallographic analyses of isolated NC1 domains show two trimeric cap-like structures interacting via a large interface. Previously, for NC1 from human placenta type-IV collagen we described covalent alpha1-alpha1 and alpha2-alpha2 crosslinks between Met93 and Lys211 of opposing alpha1(IV) and alpha2(IV) NC1-chains, which further stabilize this interface and explain the occurrence of reduction-insensitive NC1-chain dimers. However, their existence was recently questioned, and we therefore analyzed NC1-domain dimers in more detail by biochemical and protein crystallographic methods. Short-exposure diffraction data show a clear electron density cross-connecting the respective residues, which gradually disappears with prolonged crystal irradiation. Sequence analyses of isolated tryptic peptides derived from denatured NC1 monomers and dimers indicate that only the dimers, but not the monomers, yield these chemically labile cross-linked peptides. These data clearly demonstrate the presence of reduction-resistant, but chemically and radiation-sensitive covalent crosslinks between the side chains of Met93 and Lys211 in human placenta type-IV collagen.     

Taxonomic status of purported primate frontal bones from the Eocene Pondaung Formation of Myanmar

Two isolated cranial fragments from the late middle Eocene Pondaung Formation of central Myanmar have previously been interpreted as frontal bones of the amphipithecid primate Amphipithecus mogaungensis. Aside from a few maxillary fragments, these specimens provide the only potential source of information currently available regarding the cranial anatomy of Amphipithecidae. Were this taxonomic attribution correct, these specimens would indicate that amphipithecids retained numerous primitive skull features, including the absence of a postorbital septum, the retention of a voluminous olfactory chamber, and strong separation between the forebrain and the orbital fossa. However, several anatomical details observable on these specimens are incompatible with their attribution to any primate and strongly suggest that they cannot be ascribed to Mammalia. Particularly problematic in this regard are the extreme thickness of the dermal bone, the odd structure of the alleged "frontal trigon," and the mediolateral orientation and uniquely robust construction of the descending process of the frontal bone (which partially segregates the orbital and temporal fossae). Because these isolated elements can no longer be attributed to Amphipithecus, the anatomical, phylogenetic, and behavioral inferences regarding amphipithecid paleobiology that have been drawn from these specimens can no longer be sustained.     

Matrix GLA protein stimulates VEGF expression through increased transforming growth factor-beta1 activity in endothelial cells

Matrix GLA protein (MGP) is expressed in endothelial cells (EC), and MGP deficiency results in developmental defects suggesting involvement in EC function. To determine the role of MGP in EC, we cultured bovine aortic EC with increasing concentrations of human MGP (hMGP) for 24 h. The results showed increased proliferation, migration, tube formation, and increased release of vascular endothelial growth factor-A (VEGF-A) and basic fibroblast growth factor (bFGF). HMGP, added endogenously or transiently expressed, increased VEGF gene expression dose-dependently as determined by real-time PCR. To determine the mechanism by which hMGP increased VEGF expression, we studied the effect of MGP on the activity of transforming growth factor (TGF)-beta1 compared with that of bone morphogenetic protein (BMP)-2 using transfection assays with TGF-beta- and BMP-response element reporter genes. Our results showed a strong enhancement of TGF-beta1 activity by hMGP, which was paralleled by increased VEGF expression. BMP-2 activity, on the other hand, was inhibited by hMGP. Neutralizing antibodies to TGF-beta blocked the effect of MGP on VEGF expression. The enhanced TGF-beta1 activity specifically activated the Smad1/5 pathway indicating that the TGF-beta receptor activin-like kinase 1 (ALK1) had been stimulated. It occurred without changes in expression of TGF-beta1 or ALK1 and was mimicked by transfection of constitutively active ALK1, which increased VEGF expression. Expression of VEGF and MGP was induced by TGF-beta1, but the induction of MGP preceded that of VEGF, consistent with a promoting effect on VEGF expression. Together, the results suggest that MGP plays a role in EC function, altering the response to TGF-beta superfamily growth factors.     

A Potent and Specific CD38 Inhibitor Ameliorates Age-Related Metabolic Dysfunction by Reversing Tissue NAD+ Decline

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Human immunodeficiency virus Tat induces functional unresponsiveness in T cells.

Soluble proteins of the human immunodeficiency virus (HIV) might play a significant role in the pathogenesis of HIV infection. The addition of synthetic Tat peptides, but not that of the recombinant Nef or Vif protein, inhibited proliferative responses of CD4+ tetanus antigen-specific, exogenous interleukin-2 (IL-2)-independent T-cell clones in a dose-dependent manner. In addition, Tat peptides inhibited the anti-CD3 monoclonal antibody-induced proliferative responses of both purified CD4+ and CD8+ T cells. Tat did not affect proliferative responses induced by phorbol myristate acetate plus ionomycin. The Tat peptides at the concentrations used (0.1 to 3 micrograms/ml) did not affect the viability of the cells as determined by trypan blue exclusion. Treatment of Tat peptides with polyclonal Tat antibodies abrogated the inhibitory effect of Tat. Soluble Tat proteins secreted by HeLa cells transfected with the tat gene also inhibited antigen-induced proliferation of the T-cell clones. Tat inhibited the anti-CD3 monoclonal antibody-induced IL-2 mRNA expression and IL-2 secretion but did not affect IL-2 receptor alpha-chain mRNA or protein expression on peripheral blood T cells. Finally, treatment of T-cell clones with the Tat peptide did not affect the antigen-induced increase in intracellular calcium, hydrolysis of phosphatidyl inositol to inositol trisphosphate, or translocation of protein kinase C from the cytosol to the membrane. These studies demonstrate that the mechanism of the Tat-mediated inhibition of T-cell functions involves a phospholipase C gamma 1-independent pathway.     

Cophylogenetic assessment of New World warblers (Parulidae) and their symbiotic feather mites (Proctophyllodidae)

Host–symbiont relationships are ubiquitous in nature, yet evolutionary and ecological processes that shape these intricate associations are often poorly understood. All orders of birds engage in symbioses with feather mites, which are ectosymbiotic arthropods that spend their entire life on hosts. Due to their permanent obligatory association with hosts, limited dispersal and primarily vertical transmission, we hypothesized that the cospeciation between feather mites and hosts within one avian family (Parulidae) would be perfect (strict cospeciation). We assessed cophylogenetic patterns and tested for congruence between species in two confamiliar feather mite genera (Proctophyllodidae: Proctophyllodes, Amerodectes) found on 13 species of migratory warblers (and one other closely related migratory species) in the eastern United States. Based on COI sequence data, we found three Proctophyllodes lineages and six Amerodectes lineages. Distance‐ and event‐based cophylogenetic analyses suggested different cophylogenetic trajectories of the two mite genera, and although some associations were significant, there was little overall evidence supporting strict cospeciation. Host switching is likely responsible for incongruent phylogenies. In one case, we documented prairie warblers Setophaga discolor harboring two mite species of the same genus. Most interestingly, we found strong evidence that host ecology may influence the likelihood of host switching occurring. For example, we documented relatively distantly related ground‐nesting hosts (ovenbird Seiurus aurocapilla and Kentucky warbler Geothlypis formosa) sharing a single mite species, while other birds are shrub/canopy or cavity nesters. Overall, our results suggest that cospeciation is not the case for feather mites and parulid hosts at this fine phylogenetic scale, and raise the question if cospeciation applies for other symbiotic systems involving hosts that have complex life histories. We also provide preliminary evidence that incorporating host ecological traits into cophylogenetic analyses may be useful for understanding how symbiotic systems have evolved.     

Randomised controlled trial of intravenous antibiotic treatment for cellulitis at home compared with hospital

Objectives To compare the efficacy, safety, and acceptability of treatment with intravenous antibiotics for cellulitis at home and in hospital.Design Prospective randomised controlled trial.Setting Christchurch, New Zealand.Participants 200 patients presenting or referred to the only emergency department in Christchurch who were thought to require intravenous antibiotic treatment for cellulitis and who did not have any contraindications to home care were randomly assigned to receive treatment either at home or in hospital.Main outcome measures Days to no advancement of cellulitis was the primary outcome measure. Days on intravenous and oral antibiotics, days in hospital or in the home care programme, complications, degree of functioning and pain, and satisfaction with site of care were also recorded.Results The two treatment groups did not differ significantly for the primary outcome of days to no advancement of cellulitis, with a mean of 1.50 days (SD 0.11) for the group receiving treatment at home and 1.49 days (SD 0.10) for the group receiving treatment in hospital (mean difference 0.01 days, 95% confidence interval -0.3 to 0.28). None of the other outcome measures differed significantly except for patients'' satisfaction, which was greater in patients treated at home.Conclusions Treatment of cellulitis requiring intravenous antibiotics can be safely delivered at home. Patients prefer home treatment, but in this study only about one third of patients presenting at hospital for intravenous treatment of cellulitis were considered suitable for home treatment.