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Studies have been made of mucus glycoprotein biosynthesis in different regions of the lower gastrointestinal tract in normal patients and those with ulcerative colitis (UC), active or inactive, by means of 3H-glucosamine (3H-GlcNH2)--35S-sulphate double labelling of epithelial biopsy specimens under culture conditions. The time based rate of 3H-GlcNH2 labelling of mucus in rectal tissue was similar to that in active or inactive UC whereas the rate of 35SO4(2) labelling was significantly increased in active disease. The 3H specific activities measuring the amount of isotopic incorporation into surface and tissue mucus glycoproteins were increased in patients with active UC compared with normal or inactive subjects. The 35S specific activities did not differ significantly between patients with active UC and those in remission. In the rectum, glycosylation of mucus glycoproteins decreases with the increasing age of the patient. Regional differences in 3H-labelling of mucus components are reported for ascending colon, transverse colon, sigmoid colon, and rectum. Sulphation (35S-labelling) was higher in all parts of the colon in left sided UC. Results point to accelerated glycosylation of core proteins in the active phase of UC.

Pig tracheal epithelium, a site of extensive mucin biosynthesis, contained polypeptide N-acetylgalactosaminyltransferase activity directed towards L-threonine residues. The enzyme preparation was broadly similar in properties to preparations from other tissues, e.g. pig and bovine submaxillary glands, bovine colostrum, BW5147 mouse lymphoma and baby-hamster kidney cells. Enzyme was membrane-bound and was released from microsomal preparations by extraction with Triton X-100. Extracted enzyme had a pH optimum of 7.5, had a requirement for Mn2+ (10 mM) and was inhibited by Na2EDTA. The Km for UDP-N-acetylgalactosamine was 110 microM and that for an octapeptide acceptor (VTPRTPPP) was 3.0 mM at 37 degrees C. Using a range of synthetic peptides of known structure related to TPPP it was established that L-threonine residues were specifically O-glycosylated probably in the alpha-configuration. Synthetic peptides containing the TPPP sequence required a peptide length of five or more for significant acceptor activity. In VTPRTPPP the two threonine residues were similarly glycosylated, as revealed by tryptic cleavage of the glycosylated product and separation of the 3H-labelled fragments. The enzyme preparation also specifically catalysed the transfer of N-acetylgalactosaminyl residues from UDP-N-acetyl[1-3H]galactosamine to bovine submaxillary mucin core protein and to myelin basic protein.

Dual-radiolabelled avian tracheal secretions were obtained by giving Na235SO4 and D-[1-3H]glucosamine simultaneously into the lumen of the trachea in preparations in vitro. These secretions comprised fibrillar, gelatinous and soluble-phase mucins. These were eluted as single components in the non-retarded fractions from Bio-Gel A-15m. Although no evidence of the presence of subunit structure was found, chemical and radiolabelling analyses showed a high degree of internal inhomogeneity among the three types of mucins. The differences among these mucins could be attributed to the chemical nature of their constituent glycoproteins. Glycoprotein fractions separated by ion-exchange chromatography were found to contain sulphate and N-acetylneuraminic acid residues in differing amounts. The overall acidic properties appeared to be correlated with ester sulphate content. A close similarity in the carbohydrate composition and a reciprocal relationship between the total ester sulphate residue contents and 35S- and 3H-labelling suggested that, in addition to stepwise glycosylation and sulphation, some pre-existing sulphated oligosaccharides might have been utilized for the synthesis of acidic glycoproteins.

1. Incubation of rabbit tracheal explants with N-[(3)H]acetyl-d-glucosamine and N-acetyl-d-[1-(14)C]glucosamine led to labelling of a number of soluble macromolecular products separable from the medium, after papain digestion, by ion-exchange chromatography. 2. With N-acetyl-d-[1-(14)C]glucosamine in the incubation medium, a neutral glycoprotein, two acidic glycoprotein fractions, hyaluronic acid and a glycosaminoglycan fraction were obtained and all were radioactively labelled. Similar labelling occurred with N-fluoroacetyl-d-[1-(14)C]glucosamine or N-fluoro[(3)H]acetylglucosamine as precursor. 3. Maximal labelling was obtained at 96h after incubation of cultures. N-Fluoroacetyl-glucosamine under these conditions was incorporated into hyaluronate less efficiently than N-acetylglucosamine. 4. With N-fluoroacetyl-d-[1-(14)C]glucosamine as precursor, a hyaluronate component was separated that on enzymic degradation by glycosidases (hyaluronidase, beta-glucuronidase and N-acetyl-beta-hexosaminidase) yielded a (14)C-labelled oligosaccharide fraction together with N-acetyl-d-[1-(14)C]glucosamine and N-fluoroacetyl-d-[1-(14)C]glucosamine, consistent with some exchange of N-acetyl groups having occurred. 5. The results on enzymic degradation of labelled macromolecules by glycosidases suggest that the presence of incorporated N-fluoroacetyl side chains may render the hyaluronate analogue more resistant to hyaluronidase.

Chicken tracheal mucosa in vitro transported and incorporated radioactive precursors into mucins, which were secreted at a steady rate into the tracheal lumen. Secretion of mucins labelled with (35)S and (3)H after pulse-labelling of the mucosal layer with Na(2) (35)SO(4) and d-[1-(3)H]glucosamine as precursors was an energy-dependent process, as it was strongly inhibited by the action of respiratory-chain inhibitors, an uncoupler of oxidative phosphorylation, a metabolic blocker and a temperature shift from 41 degrees C to 5 degrees C. On the other hand, both cholinergic and parasympathomimetic agents considerably increased the secretion of dual-radiolabelled mucins when applied on the submucosal side of the trachea. The effect of Ca(2+) was directional, since only high submucosal (3.6 or 18mm) or low luminal (zero or 0.18mm) Ca(2+) massively enhanced the secretion of radiolabelled mucin compared with the mucin output measured under physiological Ca(2+) conditions (1.8mm). Whereas application of ionophore A23187 on either side of the trachea significantly increased mucin output, its presence in the appropriate tracheal compartment and under appropriate Ca(2+) conditions further accentuated the output of radiolabelled mucins. Addition of acetylcholine under appropriate conditions also had an additive effect on the Ca(2+)-stimulated secretion of mucins. Ca(2+) stimulation of mucin secretion appears to be dependent on the metabolic integrity of the mucosal cells. Mucins secreted in response to high submucosal and low luminal [Ca(2+)] appear to consist of a number of different types of glycoproteins, as judged from their ion-exchange-chromatographic behaviour.

1. When cultured in medium 199 in an atmosphere of O2+CO2 (95:5) rabbit tracheal explants retained their viability for up to 21 days. 2. The explants secreted into the culture medium three electrophoretically separable components which were eluted in the non-retarded fraction from Sephadex G-200. 3. Digestion with papain and fractionation with a LiCl gradient on DEAE-cellulose resulted in the separation of these components, which were identified as a sialic acid-rich glycoprotein of epithelial origin, and chondroitin sulphate and hyaluronic acid from sub-epithelial cartilage and connective tissue. 4. Incorporation of radioactive precursors ( D-[U-14-C]glucose, D-[1-14-C]glucosamine, D-[1-14-C]galactose and Na2-35SO4) into these secreted macromolecules was indicative of their active biosynthesis by the tracheal tissue.

1. Lactose 6'-O-sulphate, N-acetylneuraminyl-(alpha 2 leads to 3)-D-lactose 6'-O-sulphate, N-acetylneuraminyl ?-O-sulphate-(alpha 2 leads to 3)-D-lactose 6'0-O-sulphate, N-acetylneuraminyl ?-O-sulphate-(alpha 2 leads to 6)-D-lactose and N-acetylneuraminyl-(alpha 2 leads to 3)- and -(alpha 2 leads to 6))-lactose 6'-O-sulphate were prepared by chemical sulphation of lactose, N-acetylneuraminyl-lactose and tis isomers by using pyridine-SO3 reagent. 2. Significant kinetic differences were observed in the enzymic hydrolysis of the sulphated derivatives compared with unsubstituted substrates. 3. In the case of reactions catalysed by rat liver lysosomal and Clostridium perfringens neuraminidases (EC 3.2.1.18), the presence of an O-sulphate group in the N-acetylneuraminyl moiety affected the reaction by decreasing the Km and the Vmax, its presence in the galactosyl moiety affected the reaction by decreasing the Km and increasing the Vmax. and its presence in both N-acetylneuraminyl and galactosyl moieties decreased the Km and the Vmax. of the reaction. 4. Mixed-substrate reaction kinetic data indicated competition between the sulphated and unsubstituted substrates for the same active sites on the neuraminidase molecule. 5. Lactose 6'-O-sulphate neither behaved as a substrate nor acted as an inhibitor with respect to unsubstituted lactose and p-nitrophenyl beta-D-galactopyranoside when tested with lactase of suckling rat intestine and Escherichia coli beta-D-galactosidase (EC 3.2.1.23). 6. Preliminary investigation also indicated that, whereas glucose 6-O-sulphate and glucose 3-O-sulphate were were neither substrate nor inhibitor of glucose oxidase (EC 1.1.3.4), galactose 6-O-sulphate was oxidized half as fast as unsubstituted galactose by galactose dehydrogenase (EC 1.1.1.48).

1. Transmural Ca2+ fluxes in tracheal tissue under physiological [Ca2+] conditions and the effect of altered serosal and luminal [Ca2+] on Ca2+ movements were investigated using chicken tracheal preparations in vitro. 2. In the presence of physiological [Ca2+] (1.8 mM), there was unidirectional Ca2+ flux with a small but steady uptake of Ca2+ from the serosal side into the submucosa followed by Ca2+ transport into the mucosa and then Ca2+ efflux into the tracheal lumen. The Ca2+ uptake by the tracheal tissue was via a diffusion process. There was no evidence of Ca2+ uptake via slow Ca2+ channels or Na+-Ca2+ exchange pathways. On the other hand, Ca2+ uptake from the lumen into the mucosa and Ca2+ efflux from the submucosa into the serosal side were almost negligible. 3. High serosal [Ca2+] (18.0 mM) and/or low luminal [Ca2+] (0.18 mM) increased significantly both Ca2+ uptake by the tissue from its serosal side and Ca2+ efflux into the lumen. Directional Ca2+ effect appeared to increase Ca2+ uptake via a diffusion process. 4. Transport of Ca2+ from the mucosa into the lumen comprised efflux of both filterable and mucin-bound forms of Ca2+. Under physiological [Ca2+] conditions, whilst initial efflux rates of both filterable and mucin-bound Ca2+ were almost equal, the net efflux of Ca2+ in mucin-bound form after 10 min was about 33% higher than that of filterable Ca2+. Similarly, the increase in Ca2+ efflux as a result of high serosal [Ca2+] involved a significant increase in the efflux of mucin-bound Ca2+ only, whereas the increased Ca2+ efflux as a result of low luminal [Ca2+] involved a significant increase in efflux of both filterable and mucin-bound Ca2+. 5. The transport of Ca2+ from the mucosa into the lumen in the form of mucin-bound Ca2+ appeared to play a significant role in the regulation of Ca2+ efflux from the tissue under increased Ca2+ influx or efflux conditions resulting from interventions with serosal and luminal [Ca2+]. 6. A concurrent stimulation of secretion of unique low molecular weight sulphate-rich components and high molecular weight mucin complexes with increased Ca2+ influx into and efflux from the tracheal tissue in response to high serosal and low luminal [Ca2+] allude to a plausible role of these secretory macromolecular mucin complexes as cellular Ca2+ transport vehicles.

Suspensions of cells isolated from rabbit small intestine were prepared which showed a considerable rate of respiration after 4 h of their isolation. Rabbit intestinal cells accumulated 3-O-methyl-glucose by an active transport mechanism which was Na+-dependent whereas 2-deoxyglucose was transported by a saturable pathway. Analysis of the initial transport data indicated that the uptake of both sugars by cells followed Michaelis-Menten-type kinetics. These cells also showed a considerable degree of 2-deoxyglucose phosphorylation and the transport of the sugar into the cells appeared to be a rate-limiting factor for its phosphorylation. Sulphated glycopeptide had no effect on the respiration rate of these cells but it increased the transport of 3-O-methyl-glucose and 2-deoxyglucose into cells by many fold compared with untreated cells. Kinetic analysis of the data indicated that the increase in the transport was due to increased V while the Km remained unchanged. Presence of sulphated glycopeptide had no effect on the kinetics of phosphorylation of 2-deoxyglucose. These effects of sulphated glycopeptide on the transport activity of the cells have been discussed as a result of an increase in the number of sugar sites in the cell membrane due to unmasking or activation of preexisting sites owing to the interaction between the cell membrane components and highly polyanionic sulphated glycopeptides.

Chemically sulphated glycopeptides (derived from pig duodenal mucosa) inhibited Clostridium perfringens neuraminidase (EC 3.2.1.18) activity in a pH-dependent manner. Analysis of inhibition kinetics data indicated that, although the enzyme inhibition could not be categorized into any of the classical types of inhibition, it could be interpreted as a function of the size and shape of the substrates used. The enzyme activity was inhibited by 86% and 40% when tested with bovine submaxillary-gland mucin (mol. wt. 4 x 10(5)-40 x 10(5) and N-acetylneuraminyl-lactose (mol. wt. 633) as substrates respectively. Presence of sulphated glycopeptide did not affect the binding of N-acetylneuraminic acid (mol. wt. 309), a competitive inhibitor of Vibrio cholerae neuraminidase, to the enzyme active site. The enzyme inhibition was thus considered to be due to steric hindrance as a consequence of the non-specific interactions between the enzyme molecule and polyanionic sulphated glycopeptide affecting the differential accessibility of the substrate molecules to the enzyme active site. The enzyme-inhibitor interaction could be suppressed by rapid and many-fold dilution of the reaction mixture, by concurrent addition of the inactive enzyme or by partial removal of the sulphate esters from the sulphated glycopeptide molecule by the action of Helix pomatia arylsulphatase (EC 3.1.6.1).

Glucosamine synthetase is the first enzyme in glycoprotein biosynthesis, catalysing the formation of glucosamine-6-phosphate, from which N-acetylglucosamine is formed. The levels of this enzyme in normal human colonic mucosa (in colectomy specimens and rectal biopsies) were found to be 13-8 +/- 4-0 micron mol glucosamine synthesised/h/g wet wt. In the colonic mucosa in ulcerative colitis and Crohn's colitis the enzyme level was diminished when there was loss of epithelial cells in the mucosa, although not when there was just loss of goblet cells. In patients recovering from an acute attack of ulcerative colitis, the enzyme levels rose to a peak above the normal range, an effect which did not occur in patients who did not recover promptly. This recovery peak may be related to the synthesis of gastrointestinal mucus, or immunoglobulin, or the secretory component of IgA, all of which contain large amounts of N-acetylglucosamine.

Glucosamine synthetase, the first enzyme in glycoprotein synthesis, has been measured in serial rectal biopsies in four patients with membranous colitis. In two of the patients the levels of the enzyme were very high initially and in the other two patients the enzyme levels rose to a peak above the normal range after a delay of up to 10 days. These high levels may be related to the mucus hypersecretion which is a feature of membranous colitis but it seems more likely that they represent the healing of the mucosa.

The extent to which the self-administration of drugs is achieved under the conditions of treatment supervision available in economically under-developed countries is of crucial importance in tuberculosis control. This is a problem not only in regard to the treatment of patients suffering from active disease; it is one that is relevant, too, to the whole question of the prophylactic administration of drugs to tuberculosis contacts and to tuberculosis suspects.In this study an attempt has been made, by means of tablet counting and urine examination, to assess the extent and regularity of drug-taking over a period of one year among 87 tuberculosis patients, 478 tuberculosis household contacts and 181 tuberculosis suspects in East Africa.The results of this assessment indicate that the level of drug acceptability in all three groups was low, and it is suggested that such a level is not peculiar to the groups in this study, but is probably representative of most groups receiving antituberculosis chemotherapy under conditions of limited supervision of drug-taking.

1. Sheep colonic mucin contains three types of sialic acids, separable from the macrostructure by mild acidic hydrolysis. These are composed chiefly of N-acetyl-and N-glycollyl-neuraminic acid in ratios between 1:1.2 and 1:3.5 for different preparations of the mucin. The third sialic acid appears to be a diacetylated neuraminic acid. 2. A particle-free enzyme preparation, obtained from sheep colonic mucosa by gentle homogenization and high-speed centrifugation, catalyses a series of reactions involving N-acylamino sugars and leading to the formation of sialic acids in vitro: (i) phosphorylation by ATP of d-glucosamine, N-acetyl-and N-glycollyl-d-glucosamine; (ii) conversion of N-acetylglucosamine 6-phosphate into N-acetyl-d-glucosamine 1-phosphate; (iii) formation of sialic acids from phosphoenolpyruvate and N-acetyl- or N-glycollyl-d-glucosamine; (iv) formation of N-acetylneuraminic acid from uridine diphospho-N-acetylglucosamine or from N-acetylmannosamine; (v) incorporation of l-[U-(14)C]serine into the mucin by whole mucosal preparations.

1. Incubation of sheep colonic mucosal scrapings in Krebs-Ringer buffer for 2(1/2)hr. in the presence of salicylate (15mm) resulted in decreased incorporation of radioactivity into the epithelial glycoprotein from the following labelled precursors: 16.6mum-d-[2-(14)C]glucose (83.9% inhibition), 20mum-l-[U-(14)C]threonine (82%) and (35)SO(4) (2-)(79%). Oxygen uptake measured simultaneously was diminished to 41% of the control value. 2. At lower concentrations of salicylate (e.g. 3.75mm), incorporation of 20mum-l-[U-(14)C]threonine was little affected (3-6% inhibition), whereas utilization of 4mum-d-[U-(14)C]glucose and (35)SO(4) (2-) was inhibited (41-48% and 40-59% of the control values respectively). 3. Analysis of the papain-digested glycoprotein from tissue incubations with 16.6mum-d-[2-(14)C]glucose in the presence of salicylate (3.75mm) showed large decreases in labelling of N-acetylneuraminic acid and N-glycollylneuraminic acid residues (57% and 34% of the control values respectively) and of hexosamine constituents (glucosamine, 55% inhibition; galactosamine, 33% inhibition). Labelling of neutral sugars (galactose and fucose) was relatively little affected (9 and 11% inhibition respectively). 4. Glucose 6-phosphate transaminase and glucosamine 6-phosphate acetylase in particle-free enzyme preparations of the sheep tissue were unaffected by salicylate at the above concentrations. Acetyl-CoA synthetase was markedly inhibited. 5. Human gastric mucosa (from operation), on incubation as above, had in one experiment an oxygen consumption of 9.9mul./hr./mg. dry wt. of tissue and incorporated 5mum-d-[U-(14)C]glucose (15.8% of the total radioactivity added) into bound hexosamine (20.6% of the total radioactivity incorporated), hexoses (glucose and galactose, 5.7%) and fucose (14.2%). The presence of salicylate (15mm) decreased the incorporation of 5mum-d-[U-(14)C]glucose into the glycoprotein by 74%, all sugar constituents being affected, without influence on the rate of oxygen consumption. 6. The results suggest an inhibitory effect of salicylate on glycoprotein biosynthesis at the level of the amino sugar intermediates.

1. Synthesis of N-iodoacetyl-d-glucosamine and its N-iodo[1,2-(14)C(2)]acetyl form has been achieved from the tetra-O-acetyl amino sugar and iodoacetic acid in the presence of dicyclohexylcarbodi-imide followed by catalytic deacetylation. 2. N-Iodoacetylglucosamine (up to 0.1mm) linearly inhibits uptake (up to 1min) of methyl alpha-d-glucoside by Escherichia coli ML308 and K12. Uptake of methyl beta-d-thiogalactoside and glycerol is also inhibited. 3. Growth of the organism (strain ML308) on glucose, succinate and glycerol is strongly inhibited by the iodoacetyl compound. The inhibition is relieved by N-acetylglucosamine. 4. The inhibitor has multiple effects, some of which are considered to be intracellular. 5. A separate transport pathway exists for N-acetylglucosamine by means of which the iodoacetyl analogue may enter the cell.