Biomedical subjects

C W Prince

Publications and source records attributed to C W Prince.

42 records · Page 3Linked to original sources

PubMed1984

Incorporation of [35S]sulphate into glycosaminoglycans by mineralized tissues in vivo.

To investigate the metabolism of proteoglycans in young growing rats, calvaria, incisors, femoral diaphysis and metaphysis were labelled in vivo for 0.5-72 h with [35S]sulphate. At each time point the specific radioactivity, expressed as c.p.m. of [35S]sulphate/micrograms of uronic acid, of papain-resistant macromolecules in each tissue was determined. The identity of the glycosaminoglycans was established by the use of specific enzymic and chemical methods of degradation. Incorporation of the label into each tissue was maximal at 12 h; it then declined to 50-75% of that value by 72 h. Chondroitin sulphate was the predominant glycosaminoglycan in each tissue, representing 80-96% of the total; heparan sulphate comprised 2-14% of the total; in general, radioactive material sensitive to keratanase comprised less than 1% of the total. The relative amount of labelled chondroitin sulphate increased, whereas that of heparan sulphate decreased, with increasing time of incorporation. These data show that 25-50% of the newly synthesized glycosaminoglycans are lost from mineralizing tissues, during the time in which the newly secreted organic matrix becomes mineralized.

Animals↗

PubMed1984

Isolation and partial characterization of proteoglycans from rat incisors.

Newly synthesized proteoglycans of rat incisors were labelled in vivo for 6h with [35S]-sulphate in order to facilitate their detection during purification and characterization. Proteoglycans were extracted from non-mineralized portions (predentine) of rat incisors with 4M-guanidinium chloride and subsequently from dentine by demineralization with a 0.4M-EDTA solution containing 4M-guanidinium chloride. Both extractions were performed at 4 degrees C in the presence of proteinase inhibitors. Purification of proteoglycans was achieved with a procedure involving gel-filtration chromatography, selective precipitation of phosphoproteins, affinity chromatography and ion-exchange chromatography. Two proteoglycan populations were found in the initial extract (Pd-PG I and Pd-PG II), whereas only one fraction (D-PG) was obtained after demineralization. The minor proteoglycan fraction from the first extract, Pd-PG I, although not totally characterized, differed sharply from the other proteoglycans in that it had a larger molecular size with larger glycosaminoglycan chains composed of chondroitin 4- and 6-sulphate isomers. In contrast, the major proteoglycans Pd-PG II and D-PG had smaller hydrodynamic sizes with smaller glycosaminoglycan chains (but larger than those from bovine nasal cartilage proteoglycans) composed exclusively of chondroitin 4-sulphate. The major proteoglycans were incapable of interacting with hyaluronic acid. In general, the amino acid compositions of the major proteoglycans of rat incisors resembled that of bovine nasal cartilage proteoglycans, but the former had lower proline, valine, isoleucine, leucine, and higher aspartic acid, contents.

Amino Acids↗

PubMed1983

Metabolism of rat bone proteoglycans in vivo.

Former evaluations of the role of proteoglycans in mineralization have neglected to address the possibility that the metabolism of proteoglycans may be of significance in this regard. This problem was studied by using radiolabeling in vivo of rat calvaria with [35Sulphate for 2-72 h and a sequential extraction procedure to yield two pools of newly synthesized proteoglycans: one obtained from non-mineralized tissue by extraction with guanidinium chloride (GdmCl) and another obtained only after demineralization with EDTA. Total radioactivity in calvaria was maximal after 12 h of incorporation, but by 36 h had declined to a level that was about 55-65% of maximum. Radioactivity in the GdmCl extract declined steadily after 12 h, whereas that in the EDTA extract remained constant until 36 h, when it began to increase. Each extract contained a minor proteoglycan that eluted at the void volume (Vo) of a Sepharose CL-6B column. Unlike in the EDTA extract, this proteoglycan gradually disappeared from the GdmCl extract. Each extract also contained a major, smaller proteoglycan, with a Kav. of 0.24 and 0.36 in the GdmCl and EDTA extracts respectively. Papain digestion of each extract yielded glycosaminoglycan chains with Kav. values of 0.32 and 0.50 on CL-6B in the GdmCl and EDTA extracts respectively. Digestion of each extract with chondroitinase ABC and chondroitinase AC showed that the glycosaminoglycans were of similar disaccharide composition, with about 85% being 4-sulphated and the remainder 6-sulphated and/or iduronic acid-containing. These data suggest that about 45% of the newly synthesized proteoglycans are removed from the tissue during the course of mineralization.

Animals↗

PubMed1983

Glycosaminoglycan alterations in rat bone due to growth and fluorosis.

Evidence in the literature has suggested that alterations in bone glycosaminoglycans (GAGs) are at least partially responsible for the defective calcification in skeletal fluorosis. The major objectives of this study were to quantitate the GAGs of bone from normal and fluorotic rats and to characterize the change in bone GAGs that occurred during maturation. Weanling male rats were fed a semipurified diet and deionized water with or without fluoride (125 ppm) for 1 or 2 months. Also, a control group of rats was pair-fed to the rats receiving fluoride. GAGs were isolated from dry, fat-free tibias and then quantitated by digestion with chondroitinases and chondrosulfatases. Chondroitin-4-sulfate (C4S) comprised 90% of the bone GAGs, while chondroitin-6-sulfate (C6S), dermatan sulfate (DS) and hyaluronic acid (HA) together comprised about 10% of the total bone GAGs. With increasing age, total GAGs, C4S and HA decreased in amount, but DS remained constant. Fluorotic bone (containing in excess of 5000 ppm of fluoride) had three times as much C6S and twice as much DS as bone from weight- and age-matched control rats. Thus, using a controlled experimental animal model, we have demonstrated that specific alterations of bone GAGs result from fluorosis independently of changes in body weight and age.

Animals↗

PubMedDate not supplied

Bone response to titanium alloy implants placed in diabetic rats.

Although dental implants continue to provide consistent and predictable treatment options for most patients, some people with uncontrolled systemic disease may be denied implant treatment. Diabetes is one such disease. According to the U.S. Centers for Disease Control and Prevention, diabetes is a leading cause of blindness, kidney failure, and amputations of the lower extremities. These complications result from microvascular disturbances associated with diabetes. The effect of diabetes on the healing of titanium implants has not been well established. In this study of 32 rats, diabetes was induced in 16 animals by injection of streptozotocin (65 mg/kg); the remaining 16 animals served as controls. Titanium alloy implants were placed in the tibiae of all 32 rats using standard surgical techniques. Implants healed for 14 days. Blood samples were obtained for serum glucose, osteocalcin, and alkaline phosphatase analyses. Implants were retrieved and processed for histomorphometric analyses. Three quantities were measured using light microscopy, video capture, and computer analysis: percent osseointegration (i.e., linear bone interface), associated bone volume percent, and contact frequency. Diabetic animals demonstrated significantly less osseointegration than controls. However, bone volume percent in diabetic animals was about 4 times greater than controls. Biochemical analyses were mixed; diabetic animals demonstrated increased serum osteocalcin levels compared to controls but decreased alkaline phosphatase. Based on the results of this study, it was concluded that the bone response associated with titanium alloy implants in the tibiae of diabetic rats is uniquely different from controls.

Alkaline Phosphatase↗

PubMedDate not supplied

TPA-mediated regulation of osteopontin in human malignant glioma cells.

Malignant gliomas are the most common primary intracranial neoplasms in adults and are largely refractory to post-surgical therapy despite intensive therapeutic efforts. Using a number of different brain tumor-derived cell lines we have demonstrated that the mRNA for osteopontin (OPN), which is substantially over-expressed by some tumors in comparison with normal tissues, is preferentially expressed in high grade and metastatic brain tumors compared to low grade brain tumors. One glioma-derived cell line, U105MG, which does not express significant amounts of OPN mRNA, could be induced dose-dependently by the tumor-promoting and PKC-activating phorbol ester, TPA, to over-express OPN mRNA in a PKC-dependent manner. Unexpectedly, treatment of U105MG cells with Ca2+ ionophore (A23187) completely inhibited TPA-mediated induction of OPN while treatment with the intracellular Ca2+ antagonist TMB-8 had no significant effect. Elucidation of regulatory mechanisms for OPN induction in glioma cells should facilitate rational design of novel therapeutics for human malignant gliomas.

Calcium↗