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AIM Fluid and macromolecule transport from the interstitium into and through lymphatic vessels is necessary for tissue homeostasis. While lymphatic capillary structure suggests that passive, paracellular transport would be the predominant route of macromolecule entry, active caveolae-mediated transcellular transport has been identified in lymphatic endothelial cells (LECs) in vitro. Caveolae also mediate a wide array of endothelial cell processes, including nitric oxide regulation. Thus, how does the lack of caveolae impact "lymphatic function"? METHODS Various aspects of lymphatic transport were measured in mice constitutively lacking caveolin-1 ("CavKO"), the protein required for caveolae formation in endothelial cells, and in mice with a LEC-specific Cav1 gene deletion (Lyve1-Cre x Cav1flox/flox ; "LyCav") and ex vivo in their vessels and cells. RESULTS In each model, lymphatic architecture was largely unchanged. The lymphatic conductance, or initial tissue uptake, was significantly higher in both CavKO mice and LyCav mice by quantitative microlymphangiography and the permeability to 70 kDa dextran was significantly increased in monolayers of LECs isolated from CavKO mice. Conversely, transport within the lymphatic system to the sentinel node was significantly reduced in anaesthetized CavKO and LyCav mice. Isolated, cannulated collecting vessel studies identified significantly reduced phasic contractility when lymphatic endothelium lacks caveolae. Inhibition of nitric oxide synthase was able to partially restore ex vivo vessel contractility. CONCLUSION Macromolecule transport across lymphatics is increased with loss of caveolae, yet phasic contractility reduced, resulting in reduced overall lymphatic transport function. These studies identify lymphatic caveolar biology as a key regulator of active lymphatic transport functions.

The Late Neoproterozoic Greendale Complex, located within the Avalon terrane of Nova Scotia, is a suite of appinitic rocks ranging from ultramafic to felsic in composition that were intruded during regional ensialic arc magmatism and crystallized at shallow crustal levels under conditions of high pH 2 O. Amphibole is the dominant mafic mineral in ultramafic to mafic rocks and displays the extraordinary variability in texture and modal abundance that is characteristic of appinite suites. These features allow sensitivity of amphibole composition (major, trace and REE) to the evolution of water-rich magma to be investigated. All amphiboles in mafic and ultramafic rocks are calcic, with (Ca + Na) B ≥ 1.34 and Si IV between 6.1 and 7.3. They predominantly range in composition from tschermakite to magnesiohornblende and display a dominance of edenite (Na,K A + Al IV = Si IV ) substitution. Although each sample exhibits remarkably uniform Mg# over a wide range in Si of up to one formula unit, the mafic rock amphiboles are characterized by lower (0.5 to 0.7) Mg#, compared to the ultramafic rocks (0.7 and 0.9). REE profiles are bow-shaped, and are characterized by depletion in LREE (La/Sm ≈ 0.61), a slight depletion in HREE (Gd/Yb ≈ 1.55) as well as a negative Eu anomaly, which is attributed to co-precipitation of plagioclase. REE and trace element profiles of ultramafic amphiboles are divided into two groupings. Group A amphiboles occur in all specimens analyzed and their REE profiles are very similar to the whole-rock analyses of the mafic rocks and to those predicted from amphibole/melt partition coefficients. In contrast, Group B amphiboles display relative enrichment in light REEs (La/Sm ≈ 2.05), have lower ΣREE, and lack a negative Eu anomaly relative to Sm and Gd. Group B amphiboles are more enriched in Th and U and show a more pronounced depletion in Nb, Ti, Y and HREE. Group B amphiboles probably grew in a reaction relationship with olivine and pyroxene, and their contrasting profiles suggest that partition coefficients traditionally used for petrogenetic modeling may not be appropriate for such amphiboles. Groups A and B are virtually indistinguishable with respect to the major elements used for amphibole classification, suggesting that REE and selected trace element data, when combined with textural observations, may provide important additional insights into phase equilibria and conditions of crystallization.

Although teeth are considered one of the most important steps in vertebrate evolution, details of their origins are obscure. Two prominent and opposing theories for the evolution of the vertebrate dentition are current: the ‘Outside-in’ hypothesis and the ‘inside-out’ hypothesis. One of the main arguments against the ‘outside-in’ hypothesis is that, although similarities between teeth and scales have been observed, there is little fossil evidence of transitional forms between the two structures. Specimens of ischnacanthid acanthodians from the Man On The Hill (MOTH) locality in the Mackenzie Mountains of Canada provide the first unequivocal example of such transitional forms in an Early Devonian (Lochkovian) vertebrate assemblage. The head scales of these specimens are modified with proximity to the mouth to be extremely tooth-like. Three distinct morphotypes of modified cheek and lip scales are described. Their detailed similarity to teeth suggests that they are a result of the same developmenta...

The Early Devonian (Lochkovian) Man On The Hill (MOTH) locality in the Northwest Territories has yielded hundreds of exquisitely preserved specimens of over 72 different species of early vertebrates, greatly increasing our understanding of the diversity of this period. In this paper, we describe three new genera comprising four new species of ischnacanthid acanthodian, based on their dentigerous jaw bones and teeth. This taxonomic diversity reflects some of the diversity of dentition found among ischnacanthiform acanthodians at the MOTH locality, in contrast to their highly conservative body forms. This high diversity of related forms suggests an early radiation in jaw and tooth morphology in Early Devonian ischnacanthiform acanthodians in this region. All ischnacanthiform specimens from MOTH were originally assigned to Ischnacanthus gracilis. However, study of the unique jaw and tooth morphology of MOTH ischnacanthiform specimens indicates that it is unlikely that Ischnacanthus was present at the...