Energy intake and sources of nutritional support in patients with head and neck cancer--a randomised longitudinal study.

BACKGROUND/OBJECTIVES: Malnutrition decreases the cancer patient's ability to manage treatment, affects quality of life and survival, and is common among head and neck (HN) cancer patients due to the tumour location and the treatment received. In this study, advanced HN cancer patients were included and followed during 2 years in order to measure their energy intake, choice of energy sources and to assess problems with dysphagia. The main purpose was to explore when and for how long the patients had dysphagia and lost weight due to insufficient intake and if having a PEG (percutaneous endoscopic gastrostomy) in place for enteral nutrition made a difference. SUBJECTS/METHODS: One hundred thirty-four patients were included and randomised to either a prophylactic PEG for early enteral feeding or nutritional care according to clinical praxis. At seven time points weight, dysphagia and energy intake (assessed as oral, nutritional supplements, enteral and parenteral) were measured. RESULTS: Both groups lost weight the first six months due to insufficient energy intake and used enteral nutrition as their main intake source; no significant differences between groups were found. Problems with dysphagia were vast during the 6 months. At the 6-, 12- and 24-month follow-ups both groups reached estimated energy requirements and weight loss ceased. Oral intake was the major energy source after 1 year. CONCLUSIONS: HN cancer patients need nutritional support and enteral feeding for a long time period during and after treatment due to insufficient energy intake. A prophylactic PEG did not significantly improve the enteral intake probably due to treatment side effects.

Silk--a new substrate for UDP-d-xylose:proteoglycan core protein beta-D-xylosyltransferase.

The formation of most connective tissue polysaccharides is initiated by transfer of D-xylose from UDP-D-xylose to specific serine residues in the core proteins of the putative proteoglycans. The substrate specificity of the xylosyltransferase catalyzing this reaction has not yet been examined in detail, but it appears that a -Ser-Gly- pair is an essential part of the substrate structure. Since the preparation of the known acceptors (e.g., Smith-degraded or HF-treated cartilage proteoglycan) involves a substantial effort, we have searched for readily available proteins with the -Ser-Gly-sequence, which might serve as alternative substrates. In the present work, it was found that silk fibroin from Bombyx mori, which consists, in large part, of the repeating hexapeptide, Ser-Gly-Ala-Gly-Ala-Gly, is an excellent substrate for the xylosyltransferase from embryonic chick cartilage. Pieces of silk were used directly in the reaction mixtures, and [14C]xylose transferred from UDP-D-[14C]xylose was measured by liquid scintillation spectrometry after rinsing the silk in 1 M NaCl and water. Substantially greater incorporation was observed with preparations of silk or fibroin which had been dissolved in 60% LiSCN and subsequently dialyzed exhaustively or diluted appropriately. Under standard reaction conditions, the Vmax for fibroin was 531 pmol/h/mg enzyme protein, as compared to 223 pmol/h/mg for Smith-degraded proteoglycan. Km values were 182 mg/liter (fibroin) and 143 mg/liter (Smith-degraded proteoglycan). The product of [14C]xylose transfer to silk was alkali labile, and [14C]xylitol was formed when [14C]xylosylsilk was treated with borohydride in alkali. Proteolytic digestion with papain, Pronase, leucine aminopeptidase, and carboxypeptidase A yielded a radioactive product which was identified as [14C]xylosylserine by electrophoresis and chromatography. The identity of the isolated [14C]xylosylserine was further supported by its resistance to treatment with alkali (0.5 M KOH; 100 degrees C; 8 h) and by acid hydrolysis which yielded [14C]xylose. Tryptic and chymotryptic fragments from fibroin were also good xylose acceptors and had Vmax values 60-70% of that observed for the intact protein. Substantial acceptor activity was displayed also by the sericin fraction of silk and by the silk sequence hexapeptide. Ser-Gly-Ala-Gly-Ala-Gly; the latter had a Vmax value close to 20% of that of intact fibroin.

Biosynthesis of heparin. Substrate specificity of heparosan N-sulfate D-glucuronosyl 5-epimerase.

The substrate specificity of heparosan N-sulfate D-glucuronosyl 5-epimerase from a mouse mastocytoma was examined to determine the effects of N-acetyl and O-sulfate groups on substrate recognition by the enzyme. [5-3H]Glucuronosyl-labeled heparosan N-sulfate was prepared enzymatically and was modified chemically by partial N-desulfation and N-acetylation. After enzymatic release of tritium, the location of remaining label was determined by deaminative cleavage and analysis of resulting di-, tetra-, and higher oligosaccharides. This analysis indicated that a D-glucuronosyl residue is recognized as a substrate if it is linked at C-1 to an N-acetylated glucosamine residue and at C-4 to an N-sulfated unit. However, the reverse structure, in which the D-glucuronosyl moiety is bound at C-1 to an N-sulfated residue and at C-4 to N-acetylated glucosamine, is not a substrate. Similar studies with O-sulfated heparin intermediates showed that O-sulfate groups either at C-2 of the L-iduronosyl moieties or at C-6 of vicinal D-glucosaminyl moieties prevent 5-epimerization. These findings were confirmed by studies of the reverse reaction, in which tritium was incorporated from 3H2O into partially O-desulfated heparin and the location of incorporated radioactivity was determined. These and more direct experiments corroborated the previous conclusion that the L-iduronosyl moieties are formed after N-sulfation but before O-sulfation. Assessment of the influence of substrate size on the reaction further showed that a large substrate is preferred; an octasaccharide released tritium at a rate approximately 10% of that observed for the parent polysaccharide, and some release occurred also with smaller oligosaccharides.

New oligosaccharides from heparin and heparan sulfate and their use as substrates for heparin-degrading enzymes.

Oligosaccharides were isolated from heparin and heparan sulfate by a procedure consisting of three major steps: (a) acid hydrolysis; (b) gel chromatography; and (c) cation exchange chromatography on an amino acid analyzer. To date, six new oligosaccharides have been isolated by this procedure and have been sequenced by a combination of NaB3H4-labeling and deaminative cleavage with nitrous acid. The structures of these oligosaccharides were as follows: 1. GlcN-GlcUA-GlcN 2. GlcN-IdUA-GlcN 3. GlcN-GlcUA-GlcN-GlcUA-GlcN 4. GlcN-IdUA-GlcN-GlcUA-GlcN 5. GlcN-GlcUA-GlcN-IdUA-GlcN 6. GlcN-IdUA-GlcN-IdUA-GlcN The linkage positions and anomeric configurations were assumed to be the same as in the polysaccharides from which the oligosaccharides originated. The usefulness of some of these oligosaccharides as enzyme substrates was tested after appropriate modifications and radioactive labeling. Oligosaccharides 2 and 3 were N-[35S]sulfated and were found to serve as substrates for heparan N-sulfate sulfatase (heparin sulfamidase), with a homogenate of cultured skin fibroblasts as enzyme source. Similarly, reduction of oligosaccharide 2 with NaB3H4 yielded a substrate for acetyl-CoA:alpha-D-glucosaminide N-acetyltransferase. Finally, the previously known disaccharide, 4-O-alpha-D-glucosaminyl-L-iduronic acid, which was isolated in the course of this work, was N-acetylated with [3H] acetic anhydride and was shown to be a substrate for N-acetyl-alpha-D-glucosaminidase.

Biosynthesis of heparin. Concerted action of late polymer-modification reactions.

The substrate specificity of O-sulfotransferases involved in the biosynthesis of heparin was studied by incubating exogenous polysaccharide acceptors with mouse mastocytoma microsomal fraction in the presence of phosphoadenylyl[35S]sulfate. Characterization of the labeled products showed that O-sulfation occurs preferentially in the vicinity of N-sulfate groups; that 2-O-sulfation of L-iduronic acid residues occurs preferentially or exclusively in the absence of a 6-O-sulfate group on adjacent D-glucosamine units; and that 6-O-sulfation of D-glucosamine residues occurs readily in the presence of 2-O-sulfate groups on adjacent L-iduronic acid units. Furthermore, structural analysis of microsomal heparin-precursor polysaccharides showed a distinct intermediate species that contained 2-O-sulfated L-iduronic acid units but essentially no 6-O-sulfate groups on the (N-sulfated) D-glucosamine residues. The results suggest that 2-O-sulfation of L-iduronic acid units is tightly coupled to the formation of these units (by 5-epimerization of D-glucuronic acid residues) and, furthermore, that both processes are completed before 6-O-sulfation of the polysaccharide molecule is initiated. D-Glucuronosyl 5-epimerization not accompanied by 2-O-sulfation occurs at a still earlier stage of polymer modification; the resulting L-iduronic acid units appear to remain nonsulfated throughout the subsequent modification reactions.

Biosynthesis of heparin. Partial purification of the uronosyl C-5 epimerase.

Heparosan N-sulfate D-glucuronosyl 5-epimerase, which catalyzes the conversion of beta-D-glucuronosyl to alpha-L-iduronosyl residues in the course of heparin biosynthesis, has been purified approximately 9000-fold from the high speed supernatant fraction of a homogenate of a mouse mastocytoma. Following ammonium sulfate fractionation, the material precipitating between 35 and 60% saturation was subjected to a series of affinity chromatography steps on matrices containing immobilized concanavalin A, heparan sulfate, O-desulfated heparin, and Cibacron blue, respectively. Epimerase purified by this procedure yielded two major components on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The purified enzyme had approximately the same Kav as bovine serum albumin when chromatographed on Sepharose 6B. The activity of the purified enzyme was increased 50-fold by addition of the fraction which was not adsorbed to concanavalin A-Sepharose. The stimulating factor is likely to be a protein since it was nondialyzable, heat labile, and lost activity on digestion with trypsin.

Identification of N-sulphated disaccharide units in heparin-like polysaccharides.

1. Preparations of heparin and heparan sulphate were degraded with HNO2. The resulting disaccharides were isolated by gel chromatography, reduced with either NaBH4 or NaB3H4 and were then fractionated into non-sulphated, monosulphated and disulphated species by ion-exchange chromatography or by paper electrophoresis. The non-sulphated disaccharides were separated into two, and the monosulphated disaccharides into three, components by paper chromatography. 2. The uronic acid moieties of the various non- and mono-sulphated disaccharides were identified by means of radioactive labels selectively introduced into uronic acid residues (3H and 14C in D-glucuronic acid, 14C only in L-iduronic acid units) during biosynthesis of the polysaccharide starting material. Labelled uronic acids were also identified by paper chromatography, after liberation from disaccharides by acid hydrolysis or by glucuronidase digestion. Similar procedures, applied to disaccharides treated with NaB3H4, indicated 2,5-anhydro-D-mannitol as reducing terminal unit. On the basis of these results, and the known positions and configurations of the glycosidic linkages in heparin, the two non-sulphated disaccharides were identified as 4-O-(beta-D-glucopyranosyluronic acid)-2,5-anhydro-D-mannitol and 4-O-(alpha-L-idopyranosyluronic acid)-2,5-anhydro-D-mannitol. 3. The three monosulphated [1-3H]anhydromannitol-labelled disaccharides were subjected to Smith degradation or to digestion with homogenates of human skin fibroblasts, and the products were analysed by paper electrophoresis. The results, along with the 1H n.m.r. spectra of the corresponding unlabelled disaccharides, permitted the allocation of O-sulphate groups to various positions in the disaccharides. These were thus identified as 4-O-(beta-D-glucopyranosyl-uronic acid)-2,5-anhydro-D-mannitol 6-sulphate, 4-O-(alpha-L-idopyranosyluronic acid)-2,5-anhydro-D-mannitol 6-sulphate and 4-O-(alpha-L-idopyranosyluronic acid 2-sulphate)-2,5-anhydro-D-mannitol. The last-mentioned disaccharide was found to be a poor substrate for the iduronate sulphatase of human skin fibroblasts, as compared with the disulphated species, 4-O-(alpha-L-idopyranosyluronic acid 2-sulphate)-2,5-anhydro-D-mannitol 6-sulphate. 4. The identified [1-3H]anhydromannitol-labelled disaccharides were used as reference standards in a study of the disaccharide composition of heparins and heparan sulphates. Low N-sulphate contents, most pronounced in the heparin sulphates, were associated with high ratios of mono-O-sulphated/di-O-sulphated (N-sulphated) disaccharide units, and in addition, with relatively large amounts of 2-sulphated L-iduronic acid residues bound to C-4 of N-sulpho-D-glucosamine units lacking O-sulphate substituents.