[History of skin graft]. / Une histoire de peau.

Skin graft is the most common and simple procedure to cover superficial defect. Skin of variable thickness and size is completely detached from its origin (donor site) to cover a defect (recipient site). This simple procedure is the result of a long and eventful technical and theoretical evolvement. The aim of this article is to re-trace the history of skin grafting, from its discovery until today.

Involvement of pectin methyl-esterase during the ripening of grape berries: partial cDNA isolation, transcript expression and changes in the degree of methyl-esterification of cell wall pectins.

Grape berries (Vitis vinifera L., cv Ugni blanc) were harvested at 12 different weeks of development in 1996 and 1997. Ripening was induced at veraison, the crucial stage of berry softening, and was followed by a rapid accumulation of glucose and fructose and an increase of pH. Total RNAs, crude proteins and cell wall material were isolated from each developmental stage. A partial length cDNA (pme1, accession number AF159122, GenBank) encoding a pectin methyl-esterase (PME, EC 3.1.1.11) was cloned by RT-PCR with degenerate primers. Northern blots revealed that mRNAs coding for PME accumulate from one week before the onset of ripening until complete maturity, indicating that this transcript represents an early marker of veraison and could be involved in berry softening. However, PME activity was detected during all developmental stages. Total activity per berry increased, whereas "specific" activity, on a fresh weight basis, decreased during development. The amount of cell wall material (per berry and per g of berry) followed the same pattern as that of PME activity (total and "specific" respectively), indicating they were tightly correlated and that PME levels varied very little in the cell walls. Nevertheless, the degree of methyl-esterification of insoluble pectins decreased throughout the development from 68% in green stages to less than 20% for the ripe berries, and this observation is consistent with the induction of PME mRNAs during ripening. Relations between transcript expression, PME activity, the DE of insoluble pectic polysaccharides and their involvement in grape berry ripening are discussed.

Structural characterization of the pectic polysaccharide rhamnogalacturonan II: evidence for the backbone location of the aceric acid-containing oligoglycosyl side chain.

Monomeric rhamnogalacturonan II (mRG-II) was isolated from red wine and the reducing-end galacturonic acid of the backbone converted to L-galactonic acid by treatment with NaBH4. The resulting product (mRG-II'ol) was treated with a cell-free extract from Penicillium daleae, a fungus that has been shown to produce RG-II-fragmenting glycanases. The enzymatically generated products were fractionated by size-exclusion and anion-exchange chromatographies and the quantitatively major oligosaccharide fraction isolated. This fraction contained structurally related oligosaccharides that differed only in the presence or absence of a single Kdo residue. The Kdo residue was removed by acid hydrolysis and the resulting oligosaccharide then characterized by 1- and 2D 1H NMR spectroscopy, ESMS, and by glycosyl-residue and glycosyl-linkage composition analyses. The results of these analyses provide evidence for the presence of at least two structurally related oligosaccharides in the ratio approximately 6:1. The backbone of these oligosaccharides is composed of five (1-->4)-linked alpha-D-GalpA residues and a (1-->3)-linked L-galactonate. The (1-->4)-linked GalpA residue adjacent to the terminal non-reducing GalpA residue of the backbone is substituted at O-2 with an apiosyl-containing side chain. Beta3-L-Araf-(1-->5)-beta-D-DhapA is likely to be linked to O-3 of the GalpA residue at the non-reducing end of the backbone in the quantitatively major oligosaccharide and to O-3 of a (1-->4)-linked GalpA residue in the backbone of the minor oligosaccharide. Furthermore, the results of our studies have shown that the enzymically generated aceryl acid-containing oligosaccharide contains an alpha-linked aceryl acid residue and a beta-linked galactosyl residue. Thus, the anomeric linkages of these residues in RG-II should be revised.

The rhamnogalacturonan-II dimer decreases intestinal absorption and tissue accumulation of lead in rats.

The rhamnogalacturonan-II dimer (dRG-II) forms strong complexes in vitro with lead (Pb) and other selected cations. We examined the in vivo bioavailability of Pb complexed with dRG-II and the effect of unleaded dRG-II on the intestinal absorption and tissue retention of Pb in rats. Forty male Wistar rats were divided into four groups. Each group consumed a purified control diet for 3 wk or the same diet supplemented with: i) 3 mg of Pb/kg, ii) 0.5 g of leaded dRG-II/kg, or iii) 0.5 g of leaded dRG-II/kg and 4.5 g of unleaded dRG-II/kg. The leaded dRG-II provided approximately 3 mg of Pb/kg of diet. A chemical balance study was conducted during the last 5 d of the 3-wk study, and blood and organs were sampled for Pb and mineral analyses. The apparent intestinal absorptions of Pb were 62.3, 15.2, 11.8 and -0.1%, and Pb balances were 1.9, 9.6, 5.6 and -0.2 microg/d for the control and the three experimental groups, respectively. The Pb complexed with dRG-II was less available than Pb acetate, as reflected by significantly lower blood and tissue Pb levels. The addition of unleaded dRG-II decreased the intestinal absorption and the tissue retention of Pb significantly. We further found that the apparent absorption and status of magnesium, zinc and iron were unaffected by Pb treatment or dRG-II addition. We conclude that dRG-II may be useful in decreasing toxicity related to chronic Pb exposure. Human studies will be necessary however, to further evaluate the clinical utility of this beneficial effect.

An NMR solution study of the mega-oligosaccharide, rhamnogalacturonan II.

Rhamnogalacturonan II (RG-II) is a structurally complex pectic mega-oligosaccharide that is released enzymatically from the primary cell wall of higher plants. It contains roughly 30 monosaccharide units (MW approximately 5 kDa) including very unusual residues such as Kdo, Dha, aceric acid and apiose. Previous studies have demonstrated that these monomers are arranged into four structurally well-defined oligosaccharide side chains (A-D), linked to a homogalacturonan mainchain, but the specific attachment sites of these branches on the pectic backbone have not yet been elucidated. In the present work, fairly complete assignments of the 750 MHz 1H NMR spectra and partial assignments of the 13C NMR spectra of the sodium-borohydride-reduced RG-II monomer were obtained for a 5 mM sample isolated from red wine. On the whole, these data corroborate the primary structures of the sidechains previously established by methylation analysis, partial hydrolysis and FAB-MS spectrometry but some heterogeneity has been demonstrated (partial substitution at B5, B6, and A5). The preferred orientations of the majority of the sidechain glycosidic linkages in the RG-II monomer have been determined from the sequential nOe data and the solution structure is generally in good agreement with the stable conformers previously obtained by molecular modeling (MM3) of the disaccharide and sidechain oligosaccharide building blocks. All of a two-residue, a three-residue, and a four-residue segment of the backbone have been tentatively identified from long range interactions between sidechain protons as well as in the mainchain. Taking into account the length of the 9-mer galacturonan mainchain described in prior work, these building blocks constitute almost the complete structure of RG-II (Scheme 2).

The plant cell wall polysaccharide rhamnogalacturonan II self-assembles into a covalently cross-linked dimer.

The location of the 1:2 borate-diol ester cross-link in the dimer of the plant cell wall polysaccharide rhamnogalacturonan II (RG-II) has been determined. The ester cross-links the apiofuranosyl residue of the 2-O-methyl-D-xylose-containing side chains in each of the subunits of the dimer. The apiofuranosyl residue in each of the two aceric acid-containing side chains is not esterified. The site of borate esterification is identical in naturally occurring and in in vitro synthesized dimer. Pb2+, La3+, and Ca2+ increase dimer formation in vitro in a concentration- and pH-dependent manner. Pb2+ is the most effective cation. The dimer accounts for 55% of the RG-II when the monomer (0.5 mM) is treated for 5 min at pH 3.5 with boric acid (1 mM) and Pb2+ (0.5 mM); at pH 5 the rate of conversion is somewhat slower. Hg2+ does not increase the rate of dimer formation. A cation's charge density and its ability to form a coordination complex with RG-II, in addition to steric factors, may regulate the rate and stability of dimer formation in vitro. Our data provide evidence that the structure of RG-II itself determines which apiofuranosyl residues are esterified with borate and that in the presence of boric acid and certain cations, two RG-II monomers self-assemble to form a dimer.

Rhamnogalacturonan II, a dominant polysaccharide in juices produced by enzymic liquefaction of fruits and vegetables.

Rhamnogalacturonan II (RG-II), a small complex pectic polysaccharide, is released from apple (Malus domestica), carrot (Daucus carota), and tomato (Solanum lycopersicum) by treatment with two commercial liquefying enzyme preparations. RG-II was isolated by size-exclusion chromatography from apple, tomato, and carrot juices obtained by enzymic liquefaction. All the RG-IIs contained the diagnostic sugars, apiose, 2-O-methyl-L-fucose, 2-O-methyl-D-xylose, aceric acid, Kdo and Dha. Glycosyl-linkage compositions of the neutral and acidic sugars, including aceric acid, were consistent with the hypothetical model described for sycamore RG-II confirming the conservation of RG-II in plants. Thus, when pectinolytic enzyme preparations are used to process fruits and vegetables, RG-II is released as a main soluble polysaccharide fraction while other pectic polysaccharides are heavily degraded.

Structural characterization of red wine rhamnogalacturonan II.

The pectic polysaccharide rhamnogalacturonan II (RG-II), which accounts for approximately 20% of the ethanol-precipitable polysaccharides in red wine, has been isolated from wine polysaccharides by anion-exchange chromatography. Four fractions enriched with RG-II were obtained and the RG-II then purified to homogeneity by Concanavalin A affinity and size-exclusion chromatographies. The glycosyl-residue compositions of the four RG-IIs are similar; all the RG-IIs contain the monosaccharides (apiose, 2-O-methyl-L-fucose, 2-O-methyl-D-xylose, Kdo, Dha, and aceric acid) that are diagnostic of RG-II. The glycosyl-linkages of the neutral and acidic sugars, including aceric acid, were determined simultaneously by GC-EIMS analysis of the methylated alditol acetates generated from per-O-methylated and carboxyl-reduced RG-II. Two of the RG-IIs contain boron, most likely as a borate di-ester that cross-links two molecules of RG-II together to form a dimer. The dimer contains 3'- and 2,3,3'-linked apiosyl residues whereas the monomer contains only 3'-linked apiosyl residues which suggests that the borate di-ester is located on at least one of the apiosyl residues of RG-II. Although the wine RG-IIs all have similar structures they are not identical since they differ in the length and degree of methyl-esterification of the RG-II backbone and in the presence or absence of borate di-esters. Nevertheless, these studies show that the major structural features of wine and primary cell wall RG-II are conserved.

Rhamnogalacturonan-II, a pectic polysaccharide in the walls of growing plant cell, forms a dimer that is covalently cross-linked by a borate ester. In vitro conditions for the formation and hydrolysis of the dimer.

Rhamnogalacturonan II (RG-II) is a structurally complex pectic polysaccharide present in the walls of growing plant cells. We now report that RG-II, released by endopolygalacturonase treatment of the walls of suspension-cultured sycamore cells and etiolated pea stems, exists mainly as a dimer that is cross-linked by a borate ester. The borate ester is completely hydrolyzed at room temperature within 30 min at pH 1, partially hydrolyzed between pH 2 and 4, and stable above pH 4. The dimer is formed in vitro between pH 2.4 and 6. 2 by treating monomeric RG-II (0.5 mM) with boric acid (1.2 mM); the dimer formed after 24 h at pH 3.4 and 5.0 accounts for approximately 30 and approximately 5%, respectively, of the RG-II. In contrast, the dimer accounts for approximately 80 and approximately 54% of the RG-II when the monomer is treated for 24 h at pH 3.4 and 5.0, respectively, with boric acid and 0.5 m Sr2+, Pb2+, or Ba2+. The amount of dimer formed at pH 3.4 or 5.0 is not increased by addition of 0.5 mM Ca2+, Cd2+, Cu2+, Mg2+, Ni2+, and Zn2+. Steric considerations appear to regulate dimer formation since those divalent cations that enhance dimer formation have an ionic radius >1.1 A. Our data suggest that the borate ester is located on C-2 and C-3 of two of the four 3'-linked apiosyl residues of dimeric RG-II. Our results, taken together with the results of two previous studies (Kobayashi, M., Matoh, T., and Azuma, J.-I. (1996) Plant Physiol. 110, 1017-1020; Ishii, T., and Matsunaga, T. (1996) Carbohydr. Res. 284, 1-9) provide substantial evidence that this plant cell wall pectic polysaccharide is covalently cross-linked.

Pedicle musculocutaneous flap transplantation: prediction of final outcome by transcutaneous oxygen measurements in hyperbaric oxygen.

In pedicle musculocutaneous flaps, a local circulatory insufficiency with a total or subtotal ischemia may occur and jeopardize the result of the reconstructive surgery. Transcutaneous oxygen pressure (PtcO2) monitoring has been shown to reflect tissue perfusion and has been advocated to predict the final outcome of ischemic flaps. Unfortunately, under normal atmospheric conditions, this test is not sufficiently discriminative. We evaluate the effect of hyperbaric oxygen conditions on the efficiency of this test. Fifteen patients with pedicle musculocutaneous flap were evaluated by clinical examination and transcutaneous oxygen tension measurements. The final outcome was healing in 7 and failure in 8. In order to determine the predictive value of transcutaneous oxygen tension, measurements were done immediately after the surgical procedure. In ambient air, neither the absolute value of transcutaneous oxygen tension (2.6 +/- 3.6 versus 11.7 +/- 12.6 torr; N.S.) nor the difference or the ratio between the transcutaneous oxygen tension of the flap and the subclavicular reference shows any significant difference according to the outcome (failure or success). The same is true in normobaric oxygen. In hyperbaric oxygen, however, there is a significant difference in transcutaneous oxygen tension between the two groups (12 +/- 12 versus 378 +/- 385 torr; p < 0.01). A transcutaneous oxygen tension higher than 50 torr in hyperbaric oxygen (2.5 atm abs) is the best cutoff value to discriminate success from failure.

[Hyperbaric oxygen therapy in the treatment of wounds, in plastic and reconstructive surgery]. / L'oxygénothérapie hyperbare dans le traitement des plaies, en chirurgie plastique et reconstructive.

After recalling the mechanism of action of hyperbaric oxygen (HBO) on healing processes, the authors review the principal indications for this technique in plastic and reconstructive surgery, such as crush injuries and acute post-traumatic ischemia of the limbs, skin flaps and skin grafts, when there is a risk of their not taking, and burns. They stress the importance of strict, stratified therapeutic protocols with control of the hyperoxygenation induced by HBO. In the authors' experience, transcutaneous measurements of the partial pressure of oxygen under the hyperbaric atmosphere is a very useful method with a predictive value to determine the indications for treatment with HBO and to monitor its effects.