PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 2666518

Structure and function of lymphatics.

T J Ryan
View original source ↗Export metadata ↓

Abstract

Lymphatics are large vessels with a lumen potentially ten times wider than blood vessels and have a mean mesh diameter in the upper dermis of approximately 504 +/- 88 microns. The plexus lies just deep to the subpapillary venous plexus and when functioning well it is difficult to identify because of the attenuated endothelium and collapsed lumen. The role of the lymphatic as a pathway for the Langerhans cell and as an exit for macromolecules such as lipid and protein make it an essential organ for normal skin biology. When this system fails, impaired immunity, fibrosis, and recurrent infections are inevitable. Even vasculitis may be a consequence of failure of clearance of immune complexes from the interstitium. The adipose tissue and deep dermis are especially vulnerable in this respect. Elastin fibers support cutaneous lymphatics and may be low resistance pathways through the connective tissues into the lymphatic. Identification of lymphatics by special markers is a concept that currently fails to take into account that changing roles in disease may be associated with a change in the specificity of markers. The anatomy of lymphatic vessels in the skin is described and the role of the lymphatic is emphasized.

Explore related subjects

AnionsBiomarkersElastic TissueEndotheliumHumansLymphatic SystemJournal ArticleReview

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

T J Ryan. 1989. Structure and function of lymphatics.. https://doi.org/10.1111/1523-1747.ep12580899

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2000

The transition between the open and closed states of rubisco is triggered by the inter-phosphate distance of the bound bisphosphate.

d-Ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) catalyses the central CO(2)-fixing reaction of photosynthesis in a complex, multiple-step process. Several structures of rubisco complexed with substrate analogues, inhibitors and products have been determined by X-ray crystallography. The structures fall into two well-defined and distinct states. The active site is either "open" or "closed". The timing and mechanism of the transition between these two states have been uncertain. We solved the crystal structure of unactivated (metal-free) rubisco from tobacco with only inorganic phosphate bound and conclude that phosphate binding per se does not trigger closure, as it does in the similarly structured enzyme, triosephosphate isomerase. Comparison of all available rubisco structures suggests that, instead, the distance between the terminal phosphates (P1 and P2) of the bisphosphate ligand is the trigger: if that distance is less than 9.1 A, then the active site closes; if it is greater than 9.4 A then the enzyme remains open. Shortening of the inter-phosphate distance results from the ligand binding in a more curved conformation when O atoms of the ligand's sugar backbone interact either with the metal, if it is present, or with charged groups in the metal-binding site, if the metal is absent. This shortening brings the P1 phosphate into hydrogen bonding contact with Thr65. Thr65 exists in two discrete states related by a rotation of the backbone psi torsion angle. This rotation is coupled to domain rotation and hence to active site closure. Rotation of the side-chain of Thr65 also affects the C-terminal strand of large subunit which packs against Loop 6 after closure. The position of the C-terminal strand in the closed state is stabilised by multiple polar interactions with a distinctive highly-charged latch site involving the side-chain of Asp473. In the open state, this latch site may be occupied instead by phosphorylated anions.

Anions↗
PubMed2000

Role of the carbonate radical anion in tyrosine nitration and hydroxylation by peroxynitrite.

Peroxynitrite has been receiving increasing attention as the pathogenic mediator of nitric oxide cytotoxicity. In most cases, the contribution of peroxynitrite to diseases has been inferred from detection of 3-nitrotyrosine in injured tissues. However, presently it is known that other nitric oxide-derived species can also promote protein nitration. Mechanistic details of protein nitration remain under discussion even in the case of peroxynitrite, although recent literature data strongly suggest a free radical mechanism. Here, we confirm the free radical mechanism of tyrosine modification by peroxynitrite in the presence and in the absence of the bicarbonate-carbon dioxide pair by analyzing the stable tyrosine products and the formation of the tyrosyl radical at pH 5.4 and 7.4. Stable products, 3-nitrotyrosine, 3-hydroxytyrosine, and 3, 3-dityrosine, were identified by high performance liquid chromatography and UV spectroscopy. The tyrosyl radical was detected by continuous-flow and spin-trapping electron paramagnetic resonance (EPR). 3-Hydroxytyrosine was detected at pH 5.4 and its yield decreased in the presence of the bicarbonate-carbon dioxide pair. In contrast, the yields of the tyrosyl radical increased in the presence of the bicarbonate-carbon dioxide pair and correlated with the yields of 3-nitrotyrosine under all tested experimental conditions. Taken together, the results demonstrate that the promoting effects of carbon dioxide on peroxynitrite-mediated tyrosine nitration is due to the selective reactivity of the carbonate radical anion as compared with that of the hydroxyl radical. Colocalization of 3-hydroxytyrosine and 3-nitrotyrosine residues in proteins may be useful to discriminate between peroxynitrite and other nitrating species.

Anions↗
PubMed2000

Fast repair of dAMP radical anions by phenylpropanoid glycosides and their analogs.

Repair effect on 2'-deoxyadenosine-5'-monophosphate (dAMP) radical anions by phenylpropanoid glycosides (PPGs) and their analogs, isolated from Chinese folk medicinal herb, was studied using pulse radiolysis technique. The radical anion of dAMP was formed by the reaction of hydrated electron with dAMP. On pulse irradiation of nitrogen-saturated dAMP aqueous solution containing 0.2 M t-BuOH and one of PPGs or their analogs, the transient absorption spectrum of the radical anion of dAMP decayed with the formation of that of the radical anion of PPGs or their analogs within several decades of microseconds after electron pulse irradiation. The results indicated that dAMP radical anions can be repaired by PPGs or their analogs. The rate constants of the repair reactions were deduced to be 1.6-4.5 x 10(8) M(-1) s(-1).

Anions↗