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Biomedical subjects

R M Mason

Publications and source records attributed to R M Mason.

At least 109 records · Page 6Linked to original sources
PubMed1989

Synthesis of hyaluronate in cultured bovine articular cartilage.

The synthesis and distribution of hyaluronate and proteoglycan were studied in bovine articular cartilage in short-term explant culture with [3H]acetate and H2(35)SO4 as precursors. The incorporation of [3H]acetate into hyaluronate and sulphated glycosaminoglycans was linear with time, except that hyaluronate synthesis showed a marked lag at the beginning of the incubation. [3H]Hyaluronate represented 4-7% of the total [3H]glycosaminoglycans synthesized over a 6 h period. However, the distributions of [3H]hyaluronate and 3H-labelled sulphated glycosaminoglycans were different: about 50% of the newly synthesized [3H]hyaluronate appeared in the medium, compared with less than 5% of the 3H-labelled sulphated proteoglycans. A pulse-chase experiment revealed that the release of newly synthesized [3H]hyaluronate from cartilage was rapid. No difference was observed in the distribution of [3H]hyaluronate between medium and tissue by cartilage from either the superficial layer or the deep layer of articular cartilage. When articular cartilage was incubated with 0.4 mM-cycloheximide, proteoglycan synthesis was markedly inhibited, whereas the synthesis of hyaluronate was only partially inhibited and resulted in more of the newly synthesized hyaluronate being released into the medium. Analysis of the hydrodynamic size of [3H]hyaluronate isolated from cartilage on Sephacryl-1000 revealed one population that was eluted as a broad peak (Kav. less than 0.7), compared with two populations (Kav. greater than 0.5 and less than 0.5) appearing in the medium of cultures. These data suggest that hyaluronate is synthesized in excess of proteoglycan synthesis and that the hyaluronate that is not complexed with proteoglycans is rapidly lost from the tissue.

Animals↗
PubMed1989

Hyaluronan and hyaluronan-binding proteins in cartilaginous tissues.

Recent developments in the biology of hyaluronan in cartilage are reviewed. The homology between the hyaluronan-binding sites of cartilage proteoglycan and link protein is discussed. Previous reports indicate that an increased concentration of extracellular hyaluronan inhibits 35S-proteoglycan synthesis by several types of chondrocyte. We report data showing that this response varies in its reproducibility and sensitivity to low concentrations of hyaluronan in rat chondrosarcoma chondrocytes and pig laryngeal chondrocytes in suspension culture. Two newly recognized hyaluronan-binding proteins have been isolated from extracts of Swarm rat chondrosarcoma. The major protein has a molecular mass of 102 kDa and the less prominent protein a molecular mass of 91 kDa. The latter may be derived from the former. Neither protein cross-reacts with antisera against cartilage proteoglycan HABR (hyaluronan-binding region), link protein, hyaluronectin or type II collagen.

Animals↗
PubMed1989

In vivo turnover of the basement membrane and other heparan sulfate proteoglycans of rat glomerulus.

The metabolic turnover of rat glomerular proteoglycans in vivo was investigated. Newly synthesized proteoglycans were labeled during a 7-h period after injecting sodium [35S]sulfate intraperitoneally. At the end of the labeling period a chase dose of sodium sulfate was given. Subsequently at defined times (0-163 h) the kidneys were perfused in situ with 0.01% cetylpyridinium chloride in phosphate-buffered saline to maximize the recovery of 35S-proteoglycans. Glomeruli were isolated from the renal cortex and analyzed for 35S-proteoglycans by autoradiographic, biochemical, and immunochemical methods. Grain counting of autoradiographs revealed a complex turnover pattern of 35S-labeled macromolecules, commencing with a rapid phase followed by a slower phase. Biochemical analysis confirmed the biphasic pattern and showed that the total population of [35S]heparan sulfate proteoglycans had a metabolic half-life (t1/2) of 20 and 60 h in the early and late phases, respectively. Heparan sulfate proteoglycans accounted for 80% of total 35S-proteoglycans, the remainder being chondroitin/dermatan sulfate proteoglycans. Whole glomeruli were extracted with 4% 3-[(cholamidopropyl)dimethy-lammonio]-1-propanesulfonate-4 M guanidine hydrochloride, a procedure which solubilized greater than 95% of the 35S-labeled macromolecules. Of these 11-13% was immunoprecipitated by an antiserum against heparan sulfate proteoglycan which, in immunolocalization experiments, showed specificity for staining the basement membrane of rat glomeruli. Autoradiographic analysis showed that 18% of total radioactivity present at the end of the labeling period was associated with the glomerular basement membrane. The glomerular basement membrane [35S]heparan sulfate proteoglycans, identified by immunoprecipitation, have a very rapid turnover with an initial phase, t1/2 = 5 h, and a later phase t1/2 = 20 h.

Animals↗
PubMed1989

Ultrastructural changes accompany inhibition of proteoglycan synthesis in chondrocytes by Cyclofenil diphenol.

Cyclofenil diphenol, a weak non-steroidal oestrogen, profoundly inhibits [35S]proteoglycan synthesis in cultures of Swarm chondrosarcoma chondrocytes under conditions in which protein synthesis is only marginally reduced. In the present experiments it was shown that after a 40-min treatment with Cyclofenil diphenol (90 micrograms ml-1) most of the normally abundant Golgi stacks in these cells disappeared and after 60 min they were absent. After 2-3 h treatment the cisternae of the endoplasmic reticulum (ER) were grossly distended and transformed into large ribosome-studded vesicles containing flocculent and filamentous material. These changes were dependent on the concentration of Cyclofenil and were fully reversible within 21 h of withdrawing the drug. The ultrastructural changes differed in some aspects if protein synthesis was blocked with cycloheximide for 15 min or 180 min before and during treatment with Cyclofenil. The Golgi disappeared but the ER cisternae, though distended, formed a continuous network and swollen ribosome-studded vesicles did not develop. However, non-membrane-bounded structures containing lipid droplets and material of low electron density developed in the cytoplasm under these conditions. The ultrastructural changes induced by Cyclofenil differ from those induced by monensin and diethylcarbamazine, suggesting that the drug acts at a different point in the secretory pathway for macromolecules.

Animals↗
PubMed1989

Macroglossia: clinical considerations.

Macroglossia is a multifactorial condition that is almost always associated with a space-occupying mass of the tongue. The usual treatment is surgical resection. The typical medical conditions that lead to macroglossia have been described. The orofacial myologist should be alert to the presence of possible pathology of the tongue during orofacial examination, and refer suspected instances of macroglossia to an appropriate medical resource for definitive diagnosis and treatment.

Humans↗
PubMed1988

Renal glomerular proteoglycans. An investigation of their synthesis in vivo using a technique for fixation in situ.

Newly synthesized rat glomerular [35S]proteoglycans were labelled in vivo after injecting Na2[35S]SO4 intraperitoneally. At the end of the labelling period (7 h) the kidneys were perfused in situ with 0.01% (w/v) cetylpyridinium chloride. This fixed proteoglycans in the tissue and increased their recovery 2-3-fold during subsequent isolation of glomeruli from the renal cortex. The glomeruli were fractionated by a modified osmotic lysis and detergent extraction procedure [Meezan, Brendel, Hjelle & Carlson (1978) in The Biology and Chemistry of Basement Membranes (Kefalides, N.A., ed.), Academic Press, New York; Kanwar & Farquhar (1979) Proc. Natl. Acad. Sci. U.S.A. 76, 4493-4497] to obtain a basement membrane preparation. The proteoglycans released at each stage of the procedure were characterized using DEAE-Sephacel ion-exchange chromatography, chondroitinase ABC and HNO2 digestion and Sepharose CL-4B gel-permeation chromatography. About 85% of the [35S]proteoglycans synthesized were of the heparan sulphate variety, the remainder being chondroitin sulphate proteoglycans. Three sizes of heparan sulphate proteoglycans were identified. The largest (HS1, Kav. 0.47) accounts for 44% of the total extractable heparan sulphates. About one third of HS1 were extracted from the glomerular basement-membrane fraction with 8 M-urea and 4 M-guanidine hydrochloride but the remainder were released from the glomerulus during preparation of the fraction. The two smaller molecules (HS2, Kav. 0.56 and HS3, Kav. 0.68) accounted for 27% and 28% of the extractable heparan sulphate respectively and were not associated with the basement membrane fraction. HS1, HS2 and HS3 were also isolated from non-fixed glomeruli labelled in vivo but with much lower recovery. In glomeruli labelled in vitro, heparan sulphate accounted for only 35% of the proteoglycans, the remainder being of the chondroitin sulphate type. Proteoglycans similar to HS1, HS2 and HS3 were present in glomeruli labelled in vitro but, in addition, a large, highly charged heparan sulphate (HS1a) was extracted from the glomerular basement-membrane fraction of these glomeruli. It accounted for 6% of the total heparan sulphate.

Animals↗
PubMed1988

Pharmacological actions of 17 beta-oestradiol on articular cartilage chondrocytes and chondrosarcoma chondrocytes in the absence of oestrogen receptors.

(1) Pharmacological concentrations (greater than 10(-5) M) of 17 beta-oestradiol inhibited 35S-labelled proteoglycan synthesis in bovine articular cartilage explant cultures. They also inhibited 35S-labelled proteoglycan synthesis and 3H-labelled protein synthesis in cell cultures of chondrocytes from bovine articular cartilage and Swarm rat chondrosarcoma. Maximal inhibition was about 30-50%. Physiological concentrations (10(-9)-10(-8) M) of oestradiol had no effect on the synthesis of either protein or proteoglycan. (2) The inhibitory action of high concentrations of oestradiol on these biosynthetic pathways is not common to all steroids since 10(-4) M cortisol had no effect on articular chondrocyte cell cultures. 10(-4) M testosterone had a similar action to oestradiol. (3) Neither physiological nor pharmacological concentrations of 17 beta-oestradiol had any effect on 35S-labelled proteoglycan turnover in the cartilage explant system. (4) 10(-5) M oestradiol inhibited cell division in cultures of articular chondrocytes which had entered the log growth phase. 10(-7) M oestradiol had no effect on articular chondrocyte growth. (5) In male rats implanted with silastic capsules releasing 17 beta-oestradiol, increase in body weight was retarded by about 25% over a period of 6 weeks, compared to control rats. Rat chondrosarcoma grew to the same size in oestrogen-treated rats as it did in controls. (6) Oestrogen receptors could not be detected in freshly isolated bovine articular chondrocytes or in rat chondrosarcoma. (7) In conclusion, neither the mitotic rate of articular chondrocytes nor their proteoglycan metabolism is under the direct physiological control of oestradiol. Growth and biosynthetic activity of the rat chondrosarcoma chondrocytes are independent of either direct control by the hormone or control effected by oestradiol regulation of a second hormone or growth factor.

Animals↗
PubMed1988

Collagen stability and cross-linking in normal and kyphoscoliotic mouse intervertebral discs.

Intervertebral discs of the cervical-thoracic region of the spine of BDL mice which are homozygous for the ky gene mutation undergo degeneration. Discs from these mice have a normal collagen content and undergo normal collagen cross linking prior to the appearance of degenerative changes. The major reducible collagen cross-link formed in discs of these mice and in normal CBA strain mice is hydroxylysino-5-ketonorleucine. These results and other previous results indicate that the discs in the ky mouse develop degenerative disease due to an extrinsic factor rather than to an intrinsic abnormality of their extracellular matrix. The extrinsic factor has been identified as spinal muscle atrophy.

Animals↗
PubMed1987

Tunicamycin partially delays release of newly synthesized hyaluronate from Swarm rat chondrosarcoma chondrocytes.

Tunicamycin (5-100 micrograms/ml) inhibits total [3H]hyaluronate synthesis in cultures of Swarm rat chondrosarcoma chondrocytes by approx. 15%. In agreement with previous results (Lohmander, L.S., Fellini, S.K., Kimura, J.H., Stevens, R.L. and Hascall, V.C. (1983) J. Biol. Chem. 258, 12280-12286) the relative decrease in [3H]hyaluronate radioactivity in the culture medium was greater than in the cell layer. Treated cultures show a concentration-related decrease in the proportion of medium 35S-labelled proteoglycans forming 'natural aggregates'. Pulse-chase experiments in cultures pretreated with tunicamycin (100 micrograms/ml, 13 h) showed that 30-40% of the total [3H]hyaluronate synthesized is released more slowly from these chondrocytes than from control culture chondrocytes. Release of some hyaluronate molecules may be delayed by 6 h or more. After a 24 h chase period almost all the [3H]hyaluronate is released from the cells. The proportion of 35S-labelled proteoglycans present as aggregates in the 24 h chase medium (57%) remained depressed compared to controls (81%), although the monomers could form aggregates if exogenous hyaluronate was added. Hyaluronate synthesized in the presence of tunicamycin has the same hydrodynamic size as control culture hyaluronate, as assessed by its sedimentation profile in CsSO4 gradients and its chromatographic profile on a dissociative Sephacryl S-1000 column.

Animals↗
PubMed1987

Antibodies in calves on feed supplemented with chlortetracycline after vaccination with Brucella abortus strain 19.

Twenty dairy heifers each consumed 350 mg of chlortetracycline/day in their feed. Four tests were performed on serum specimens from these and 20 control calves after vaccination with Brucella abortus strain 19. The numbers of positive test results on the card test and mean titers on the tube and rivanol agglutination and complement-fixation tests were compared in the 2 groups. Using the rivanol and complement-fixation tests, there were differences in the mean titers at weeks 5 and 6 after vaccination, but by week 10, differences were not found. The results suggest that addition of low concentration of chlortetracycline in feeds have minimal effects on postvaccinal serologic reactions determined after strain-19 inoculation.

Agglutination Tests↗
PubMed1987

Different growth rates of swarm chondrosarcoma in Lewis and Wistar rats correlate with different thyroid hormone levels.

The transplantable Swarm rat chondrosarcoma grew to twice the weight in 5 weeks in Lewis strain rats (approximately 80 g) as it did in Wistar strain rats (approximately 40 g). Wistar tumor passaged into Lewis rats adopted the accelerated growth rate of the Lewis tumor on the second passage. Conversely Lewis tumor passaged into Wistar rats grew like Wistar lineage chondrosarcoma after two passages. Lewis and Wistar tumors had a similar histological appearance. The extracellular matrix composition of the two tumors was very similar. Tumor explant cultures synthesized about the same amount of 35S-proteoglycans and the same proportion of 3H-hyaluronate: 3H-chondroitin sulfate. Serum levels of growth hormone and insulin were the same in the two strains but T3 and T4 levels were 50% higher in Lewis rats compared to Wistar rats. It is likely that accelerated tumor growth in Lewis strain rats is related to the higher thyroid hormone levels.

Animals↗
PubMed1987

Mineral content of milk, colostrum, and serum as affected by physiological state and mineral supplementation.

A 22-mo experiment was conducted to determine effects of mineral supplementation of cows on mineral elements in milk, colostrum, and blood serum. Purebred Brahman beef cows grazing pastures grown on sandy and well-drained soils were allotted to three treatments of 12 cows each as follows: control, a complete commercial mineral mixture, control plus dietary and injected Se, and control plus fortified mineral mixture. Milk and serum were analyzed for minerals 2 consecutive yr at parturition and 3 mo postpartum. Mean cow serum, Ca, Mg, P, and packed cell volume values were higher at parturition than 3 mo later, whereas serum Cu was highest at 3 mo. Mean serum concentrations were affected by year with higher Ca and hemoglobin and lower Cu concentrations in 1982 than in 1981. Increasing dietary Se resulted in higher serum Se. Colostrum was higher in Mg, P, Cu, Fe, Se, and Zn than milk, whereas milk was higher than colostrum in Mn. Means for treatment X time showed cows fed dietary and dietary plus injected Se and vitamin E had more Se in milk than milk from cows fed no supplemental Se.

Animals↗