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Biomedical subjects

J R Fraser

Publications and source records attributed to J R Fraser.

At least 73 records · Page 4Linked to original sources
PubMed1989

A pharmacokinetic model of intravenously administered hyaluronan in sheep.

Hyaluronan (HA: hyaluronic acid) is produced in the interstitium and reaches the blood circulation through the lymph. It is rapidly eliminated by means of specific receptors on liver endothelium. The elimination characteristics of intravenously administered HA were studied in 10 conscious sheep at the normal plasma HA concentration by injection of a 3H-labeled tracer and at a very high concentration by an i.v. infusion of unlabeled HA and simultaneous injection of a tracer dose of 3H-labeled HA. At a normal plasma HA concentration (0.12 +/- 0.05 microgram/ml; range, 0.072-0.228 microgram/ml), the apparent T 1/2 of 3H-HA was 5.3 +/- 1.1 min (range, 3.3-6.5 min). At higher plasma concentrations (range, 1.83-3.35 micrograms/ml), the apparent T 1/2 was considerably prolonged (range, 18.2-43.5 min). A one-compartment, nonlinear model was fitted to data obtained from the bolus-infusion study of unlabeled HA. The Michaelis-Menten constant, Km, was 0.12 +/- 0.04 microgram/ml, indicating that a deviation from linear kinetics will occur when the normal plasma concentration is exceeded. The Vmax was 0.062 +/- 0.009 microgram/ml/min. Three-dimensional surface plots showed that the plasma HA concentration and the total hepatic plasma flow influence the apparent metabolic clearance, extraction ratio, turnover, and T 1/2 of intravenously injected hyaluronan. There was a high correlation between T 1/2 as measured by the injected 3H-HA and T 1/2 calculated from the model (r = 0.96).

Animals↗
PubMed1989

Elimination and subsequent metabolism of circulating hyaluronic acid in the fetus.

Hyaluronic acid differs from other glycosaminoglycans in its lack of covalently linked peptide, absence of sulphate groups, and the exceptional size of its single-chain polymers. These differences can be related to its distinct physical and functional properties, and may be pertinent to its greater abundance in early tissue development. In mature animals, the turnover of hyaluronic acid in tissues is reflected at least partly in the blood stream. The metabolism of circulating hyaluronic acid was therefore studied in fetal sheep after intravenous injection of [3H]acetylhyaluronic acid. Between 95% and 99% was removed within 6 min. Plasma radioactivity decayed by first-order kinetics, with a half-life between 0.8 and 1.25 min. The rate of elimination did not vary materially with hyaluronic acid fractions of widely disparate average Mr or with fetal age between 70 and 120 days. 3H2O was detected in plasma within 8-10 min. Labelled material found in urine from 10 min onward included polymers greater than or equal to 70,000 Mr, which indicates that urine may be a source of hyaluronic acid in amniotic fluid. Elimination from the plasma took place mainly in the liver, where labelled material was largely recovered in small metabolic residues as early as 28 min after injection. These were shown by high pressure liquid chromatography (h.p.l.c.) to include water, acetate, N-acetylglucosamine and a fraction tentatively identified as N-acetylglucosamine 1-phosphate. Tritium radioactivity was detected in hepatic lipids but not those of the spleen. Estimated plasma turnover was in the order of 10 micrograms/min per kg body weight. This is about 3-10 times that in adult animals and is consistent with an increased inflow of hyaluronic acid generated during the maturation of developing tissues.

Amniotic Fluid↗
PubMed1989

Turnover and metabolism of hyaluronan.

The highest concentrations of hyaluronan occur in synovial fluid, vitreous body, skin and certain specialized tissues such as umbilical cord and rooster comb, during fetal development, and in tissue repair and regeneration. The largest amounts are found in the intercellular matrix of skin and musculoskeletal tissues. Turnover in the bloodstream is normally in the range of 0.3-1.0 microgram min-1/kg body weight. Circulating hyaluronan is mostly derived from lymph. Lymph nodes may nevertheless extract as much as 80-90% from peripheral lymph before it can reach the bloodstream. Turnover in peripheral tissues may be effected by degradation in situ, or by transfer into lymph by diffusion or hydrodynamic forces. Hyaluronan is firmly bound in specific association with cells or binding proteins but much of it exists in freely mobilized compartments with a half-life of two days or less, and it is metabolized after transport elsewhere. Metabolic degradation of hyaluronan is principally intracellular and relies on uptake by a receptor which, in contrast with other hyaluronan-binding structures, also binds chondroitin sulphate. It is suggested that this dual specificity may be primarily associated with metabolic degradation of hyaluronan. Uptake and metabolism are primarily effected in liver and lymph node by endothelial cells lining the sinusoids of each. Further studies indicate that in lymph nodes and in spleen, macrophage-like cells intertwined with the endothelial cells also take up hyaluronan. The metabolic cycle from polymer to monosaccharides, acetate and beyond can be completed in vivo within 10 minutes.

Animals↗
PubMed1988

Uptake and degradation of hyaluronan in lymphatic tissue.

Afferent lymph vessels entering popliteal lymph nodes of sheep were infused with [3H]acetyl-labelled hyaluronan of high Mr (4.3 x 10(6)-5.5 x 10(6)) and low Mr (1.5 x 10(5)). Analysis of efferent lymph and of residues in the nodes showed that hyaluronan presented by this route is taken up and degraded by lymphatic tissue. Labelled residues isolated in node extracts by gel chromatography and h.p.l.c. included N-acetylglucosamine, acetate, water and a fraction provisionally identified as N-acetylglucosamine 6-phosphate. Between 48 and 75% of the infused material was unrecovered, and had been presumably eliminated through the bloodstream as diffusible residues. Rates of degradation reached as high as 43 micrograms/h in a node of 2 g wt. infused with 56 micrograms/h. Some HA passed into efferent lymph and some was detected in the nodes, but fractions of Mr greater than 1 x 10(6) were not found in either. It is concluded that the amounts and Mr values of hyaluronan released from the tissues into peripheral lymph can be significantly underestimated by analysis of efferent lymph, i.e. lymph that has passed through lymph nodes. A substantial role in the normal metabolic turnover of at least one major constituent of intercellular matrix and connective tissue may now be added to the established functions of the lymphatic system.

Adsorption↗
PubMed1988

Immune complexes and Ross River virus disease (epidemic polyarthritis).

Immune complexes were sought in serum and synovial fluid in Ross River virus disease (epidemic polyarthritis). Multiple samples from 15 patients showing varied degrees of disease activity over a 3 month period were analysed for their content of complement components C3 and C4, and for C1q solid-phase and Raji cell binding activity. Levels of C3 and C1q binding activity were normal. C4 and Raji cell binding activity were normal except for three high levels of Raji cell binding, of which two were accompanied by low levels of C4, with normal C3 and C1q binding. Synovial fluid showed anomalous Raji cell reactivity of uncertain significance. Conglutinin solid-phase binding activity and IgG rheumatoid factor were compared in the serum of 20 patients during active disease and after recovery. The results were identical and within the normal range in both phases. One patient developed IgM rheumatoid factor in a low titre late in his illness. Although these findings do not entirely exclude a role for immune complexes formed at the onset in the circulation or tissues, it is concluded from this and other evidence that circulating complexes are not commonly responsible for the persistence of syndromes in this disease.

Antigen-Antibody Complex↗
PubMed1988

An experimental technique to study the turnover of concentrated hyaluronan in the anterior chamber of the rabbit.

An experimental technique to study the turnover of hyaluronan in the anterior chamber in single animals has been developed. It is based on the fact that circulating hyaluronan labelled with tritium in the acetyl group is rapidly taken up by the liver and degraded to tritiated water. 3H-labelled hyaluronan was mixed with high concentration, high molecular weight hyaluronan (Healon) and injected into the anterior chamber of rabbits. The concentration of tritiated water in blood plasma was followed for up to 13 days. An initial rise of radioactivity in the blood was followed by an exponential decrease. From the exponential disappearance it was possible to calculate the rate of turnover of water in the body. This was used to correct the initial rise of tritium for water losses. After this correction the appearance of radioactive water in blood corresponded to the disappearance of hyaluronan from the eye plus a 45 min time-lag due to the catabolism in the liver. Using this technique it was found that trace amounts of radioactive hyaluronan and 0.055 ml and 0.2 ml of 1% hyaluronan exhibited half-lives in the anterior chamber of 1.5, 7 and 13 hr respectively. When the same technique was used for subcutaneously and intramuscularly injected hyaluronan half-lives of 50 and 30 hr, respectively, were recorded.

Animals↗
PubMed1988

Glomerulonephritis in the acute phase of Ross River virus disease (epidemic polyarthritis).

Hematuria and proteinuria were detected at the peak of symptoms in a case of Ross River virus (RRV) disease. No other infective cause was identified. A renal biopsy 28 days after the onset of nephritis showed mild mesangial proliferative changes and one segmental sclerotic lesion. Immunofluorescence showed widespread linear deposition of IgG in glomerular capillary walls with similar but weak staining for IgM, complement (C3) and fibrinogen; granular deposits of IgM and C3 in several arterioles; and IgM in a few mesangial cells. No electron-dense deposits were detected, nor was RRV antigen found in the renal tissue. Anti-glomerular basement membrane antibodies were not detected in the serum. Recovery from the renal disturbance was complete within three months although rheumatic symptoms persisted for 30 months.

Acute Disease↗
PubMed1987

Diverse morphological responses of normal human synovial fibroblasts to mononuclear leukocyte products: relationship to prostaglandin production and plasminogen activator activities, and comparison with the effects of purified interleukin 1.

Supernatant media from cultured human mononuclear blood leukocytes (MCCM) induced morphological changes in normal human synovial fibroblasts in culture, including the formation of cells with a dendritic or stellate morphology and, less frequently, cells with a striking fenestrated appearance. These changes were fully reversed within 1 h of removing the MCCM. They were inhibited by indomethacin, the glucocorticoids hydrocortisone, prednisolone and dexamethasone, and by colcemid, but not by actinomycin D and only weakly by cycloheximide. The morphological responses to MCCM could be reproduced by MCCM fractions containing interleukin 1-like activity and by purified forms of human interleukin 1 (IL-1), including monocyte-derived IL-1 beta and recombinant IL-1 alpha. These responses were also inhibited by indomethacin, indicating a link with prostanoid production. However, the morphological responses were not related to the stimulation of plasminogen activator activity due to MCCM, MCCM fractions, or IL-1.

Cells, Cultured↗
PubMed1987

Collagen antibodies in Ross River virus disease (epidemic polyarthritis).

Antibody activity against collagen was measured in 53 samples of serum from 48 patients with active signs of epidemic polyarthritis (EPA) following infection with Ross River virus. Activity was higher against denatured collagen than against native collagen, but was within the normal range for each. Determination of HLA phenotypes permitted a search for any relationship between HLA type and differences in collagen antibody levels within the normal range. No relationship was detected with HLA antigens predominating in EPA or with HLA antigens that are associated with high collagen-antibody levels in rheumatoid arthritis (RA), which suggests that the latter associations may represent failure to control collagen antibody levels after the onset of RA. The findings also provide evidence against a role for nonspecific enhancement of humoral immune responses in the pathogenesis of EPA, and constitute a further point of distinction between EPA and RA.

Adolescent↗
PubMed1987

Interleukin-1 beta and interleukin-1 alpha stimulate the N-acetyl-beta-glucosaminidase activity of human synovial cells.

The properties of synovial cells are altered in vitro by monocyte-macrophage polypeptides (monokines), and these changes could explain some of the properties of the inflamed synovium in rheumatoid disease. Purified monokines have become available only recently for testing on the target synovial cells. We report here that purified human interleukin (IL)-1 beta and recombinant human IL-1 alpha stimulate the extracellular activity of the lysosomal hydrolase, N-acetyl-beta-glucosaminidase (NAG), of human synovial fibroblast-like cells. In contrast, another monokine, synovial activator, does not increase the NAG activity. Thus NAG is another cellular activity which can be modulated by interleukin-1.

Acetylglucosaminidase↗
PubMed1987

Specific IgA antibody response in Ross River virus infection.

Sera were collected over a period of several years from the onset of initial symptoms from 77 patients with Ross River virus infection. When tested for virus-specific IgA antibodies, using an enzyme-linked immunosorbent assay (ELISA) based on antibody class capture, 245 out of 704 sera were antibody-positive. Although Ross River virus IgA antibodies were present in the serum of all patients soon after onset of symptoms, the IgA response was relatively short-lived in comparison with specific IgM antibodies. The results suggested that the detection of high levels of Ross River virus IgA antibodies was of potential value in differentiating between recent and past infection, especially in those patients with persisting IgM antibodies.

Alphavirus↗
PubMed1986

Concentration and relative molecular mass of hyaluronate in lymph and blood.

Human lymph was collected from patients with leaking lymph vessels after thoracic surgery. Ovine lymph was obtained from the mesenteric, lumbar, popliteal and prescapular lymph ducts by cannulation. The concentration of hyaluronate varied considerably (between 0.2 and 50 mg/l) and the highest concentrations were found in mesenteric lymph. The Mr of the polysaccharide showed a great polydispersity and variation between individuals and in different regions of the lymphatic system. High-Mr hyaluronate (greater than 10(6) was present in lymph both from man and sheep. Hyaluronate was also isolated by affinity chromatography in 70-80% yield from human serum and plasma obtained from healthy individuals and patients with rheumatoid arthritis and primary biliary cirrhosis. The weight (Mw)- and number (Mn)-average relative molecular masses were roughly the same in the three groups [(1.4-2.7) X 10(5) and (2.1-5.7) X 10(4) respectively]. The low Mr of hyaluronate in blood compared with that in lymph is explained by a preferential uptake of the large molecules by the liver endothelial cells.

Adult↗
PubMed1986

Binding of hyaluronate and chondroitin sulphate to liver endothelial cells.

Hyaluronate is taken up and metabolized in liver endothelial cells by means of a receptor. To characterize the interaction with the receptor, two preparations of 3H-labelled hyaluronate, of Mr 4 X 10(5) and 6.4 X 10(6), and a series of hyaluronate oligosaccharides were bound to cultured liver endothelial cells at 7 degrees C. The dissociation constant varied between 4.6 X 10(-6) M for an octasaccharide and 9 X 10(-12) M for the largest polymer. The Mr-dependence for the series of oligosaccharides was explained by the increased probability of binding due to the repetitive sequence along the chain. The high affinity of high-Mr hyaluronate for the receptor could also be mainly ascribed to this effect, which rules out any major contribution of co-operative multiple-site attachment to the cell surface. Each liver endothelial cell can bind 10(5) oligosaccharides, about 10(4) molecules with Mr 4 X 10(5) and about 10(3) molecules with Mr 6.4 X 10(6). This is explained by mutual exclusion of large molecules from the cell surface. Chondroitin sulphate is also bound to liver endothelial cells. Inhibition studies showed that it binds to the same receptor as hyaluronate and with an affinity that is about 3-fold higher than that of hyaluronate of the same degree of polymerization.

Animals↗
PubMed1986

The properties and turnover of hyaluronan.

Hyaluronan (HA) was discovered over 50 years ago but its metabolism and cellular interactions have only recently received detailed attention. HA is synthesized in the plasma membrane by addition of monosaccharides to the reducing terminal. In tissues, it occurs bound to plasma membranes, aggregated with other macromolecules, or as free polysaccharide. Tissue HA enters the bloodstream in significant amounts through the lymph and is rapidly absorbed via a receptor into liver endothelial cells, where degradation follows. HA levels in serum are normally 10-100 micrograms/l, but can be elevated in cirrhosis, rheumatoid arthritis and scleroderma, due either to impaired hepatic uptake or to increased production. Studies on aqueous humour, middle ear secretion, amniotic fluid, lung lavage fluid, urine, skin diseases and cancer have identified other causes of deranged HA metabolism. HA can be visualized on some cell surfaces as a coating impermeable to particulate material. Specific HA binding occurs on lymphoma cell lines, lung macrophages and SV-3T3 cells but, except in synthesis or uptake, the significance of membrane-associated HA is incompletely understood. It has been reported to activate macrophages and granulocytes, protect cells, control cell migration, and cooperate with intercellular matrix in cell detachment; it also plays a central role in growth control, cellular differentiation and tissue morphogenesis.

Animals↗
PubMed1986

Arbovirus infection in a Murray Valley community.

Serum antibodies to Ross River virus and Murray Valley encephalitis virus were measured during 1974-1975 in residents of Echuca, an urban Murray Valley community. A representative group of volunteers was obtained by random selection of households. The prevalence of antibodies to both viruses increased progressively with age. Prevalence was equal in both sexes for both viruses in all age groups, indicating that the risk of infection was mainly determined by geography rather than by personal activities. Antibody levels remained unchanged in the following year when there was no disease activity in the area. The stability of antibody levels permitted retrospective estimates of mean rates of infection. These were approximately 0.4% per annum for both viruses when age was used as the index for years of exposure. With allowance for other factors, the best estimate for both virus infections is probably closer to 1%. The morbidity rate for Ross River virus infection appeared to be low. It is concluded that infection with Ross River virus and with Murray Valley encephalitis-related viruses is endemic in the Murray Valley.

Adolescent↗
PubMed1986

The catabolic fate of hyaluronic acid.

Part of the hyaluronic acid (HA) synthesized in peripheral tissues enters the blood circulation through the lymph. It is rapidly taken up by the endothelial cells in the liver (half-life in blood is 2.5-5.5 minutes) and degraded. Pure primary cultures of liver endothelial cells were obtained by a newly developed technique and used to follow the metabolism of the polysaccharide on the cell surface. At 37 degrees C the HA is effectively endocytosed and degraded to acetate and lactate. A radioassay specific for HA and sensitive in the nanogram range has been developed to follow the concentration of HA in serum. The normal level in man is 10 to 100 micrograms/l. Elevated serum levels of HA are seen in liver cirrhosis, rheumatoid arthritis and scleroderma indicating that both an impaired catabolism in the liver and an increased synthesis in the peripheral tissues can modify the HA level.

Animals↗