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Biomedical subjects

B W Oakes

Publications and source records attributed to B W Oakes.

At least 19 recordsLinked to original sources
PubMed1995

Biomechanics of patellar tendon autograft for reconstruction of the anterior cruciate ligament in the goat: three-year study.

This study examined the biomechanics of anterior cruciate ligament-patellar tendon autografts for as long as 3 years after surgery. Twenty-seven adult female goats were tested; four served as controls and the others received an autograft to the right knee with each left knee serving as an additional control. The animals with grafts were tested at 0 week (n = 4), 6 weeks (n = 4), 12 weeks (n = 4), 24 weeks (n = 3), 1 year (n = 5), and 3 years (n = 3) after surgery. The anteroposterior laxity of the knee joint, load-relaxation, and structural and material properties of the graft were tested. The anteroposterior laxity was significantly greater than that of the controls for all groups except at 3 years. Load-relaxation was greater than that of the control anterior cruciate ligaments, but in the 1 and 3-year grafts load-relaxation was less than that of the patellar tendons with 5 minutes of sustained loading. Between 12 and 52 weeks, the stiffness and modulus of the grafts increased 3-fold, but the improvement was slow afterward. At 3 years, the strength and stiffness of the grafts were 44 and 49% those of the control ligaments, respectively; the modulus was 37 and 46% that of the control anterior cruciate ligaments and patellar tendons, respectively. The persistent inferior mechanical performance at 3 years suggests that anterior cruciate ligament grafts may never attain normal strength.

Animals↗
PubMed1990

Characterization and synthesis of macromolecules by adult collateral ligament.

Bovine collateral ligament was found to have a water content of 67.5 +/- 2.5%, the tissue was highly collagenous containing 100.3 +/- 15.1 micrograms hydroxyproline/mg dry weight. Type I collagen was the major collagen present with small amounts of Type III and V. The hexuronate content of the tissue was found to be 2.62 +/- 0.40 micrograms hexuronate/mg dry weight of tissue. On incubation in vitro collateral ligament incorporated [35S]sulfate and [3H]acetate into proteoglycans and [3H]acetate into hyaluronate and glycoproteins. The rate of synthesis of proteoglycans by collateral ligament was shown on a weight basis to be greater than that of tendon but lower than that of articular cartilage. Analysis of the proteoglycans present in collateral ligament showed two populations of proteoglycans to be present. Approx. 20% of the total proteoglycans present were large chondroitin- and keratan sulfate-containing proteoglycans capable of forming aggregates with hyaluronate. The major species of proteoglycan present were small dermatan sulfate proteoglycans made up of a core protein with a molecular mass of 45,000 daltons with one dermatan/chondroitin sulfate glycosaminoglycan chain of 30,000 daltons attached. The N-terminal amino acid sequence of the core protein of this proteoglycan showed it to be analogous to the core protein of dermatan sulfate proteoglycan II.

Amino Acid Sequence↗
PubMed1985

Alteration of the extracellular matrix of smooth muscle cells by ascorbate treatment.

The protein composition in the extracellular matrix of cultured neonatal rat aortic smooth muscle cells has been monitored over time in culture. The influence of ascorbate on insoluble elastin and collagen has been described. In the absence of ascorbate, the cells accumulate an insoluble elastin component which can account for as much as 50% of the total protein in the extracellular matrix. In the presence of ascorbate, the amount of insoluble collagen increases, while the insoluble elastin content is significantly less. When ascorbate conditions are varied at different times during the culture, the extracellular matrices are altered with respect to collagen and elastin ratios. The decrease in elastin accumulation in the presence of ascorbate may be explained by an overhydroxylation of tropoelastin. Approximately 1/3 of the prolyl residues in the soluble elastin fractions isolated from cultures grown in the presence of ascorbate are hydroxylated. Since the insoluble elastin accumulated in these cultures contain the unique lysine-derived cross-links in amounts comparable to aortic tissue, this culture system proves ideal for studying the influence of extracellular matrix elastin on cell growth and metabolism.

Amino Acids↗
PubMed1984

In vitro response of chondrocytes to mechanical loading. The effect of short term mechanical tension.

Chick epiphyseal chondrocytes were grown in high density cultures for 14 days, after which the cell layers were placed in a cyclical stretching apparatus and subjected to a strain of 5.5% at a frequency of 0.2 Hz. There was a 1.4- and 1.7-fold increase in the incorporation of 35SO4 and 14C-glucosamine, respectively, into glycosaminoglycans in cultures subjected to mechanical loading for 24 h. No significant change was observed in the hydrodynamic size of the proteoglycans synthesized by chondrocytes subjected to mechanical loading. In this time period there was no increase in 3H-glycine incorporation into acid-insoluble protein, but there was a 2.4-fold increase of 3H-thymidine into DNA in cultures subjected to tensional strain. Concomitant with these changes, the cellular levels of cyclic AMP increased 2.2 times in the mechanically loaded cultures. This is discussed as a possible mechanism whereby chondrocytes respond to mechanical stimuli.

Animals↗
PubMed1984

Hamstring muscle injuries.

Probably the most common lower limb injury in amateur and professional athletics is strain of the hamstring muscles. Its frequent mismanagement stems from the inability of the athlete and his medical advisors to assess accurately the severity of the damage, coupled with the often premature return to competition which can result in a demoralising repeat muscle tear.

Athletic Injuries↗
PubMed1982

The synthesis of elastin, collagen, and glycosaminoglycans by high density primary cultures of neonatal rat aortic smooth muscle. An ultrastructural and biochemical study.

Primary cultures of neonatal rat aortic smooth muscle cells inoculated at high densities (1 X 10(6) cells/25 cm2 Falcon flask) with adequate nutrient media and pH control grow rapidly and form multilayers of cells with typical "hill and valley" organization. After 10 days growth insoluble elastin formation could be visualized by phase contrast microscopy as small particles which grew rapidly to become larger irregular refractile aggregates and later coalesced to form larger aggregates and small fibres. With light and electronmicroscopy, elastin was the predominant matrix protein formed, with the "hill regions" of cultures containing abundant elastin aggregates and some collagen. In 2-week-old cultures differentiation could be observed within the cell multilayer. The older deeper cells contained more protein synthesis organelles and myofilaments and were in close association with large often coalescing elastin aggregates; compared to younger more superficial cells which contained more free polyribosomes less myofilaments, and were associated with fewer and small elastin aggregates. In older cultures this differentiation was not apparent; the cells contained many myofilaments, dense bodies, and lysosomes. Elastin aggregates and newly formed elastic fibres were abundant in the matrix. Quantitative analysis of insoluble elastin formation in the cell layer during the 4-week culture period indicated continuous biosynthesis and deposition which paralleled that of desmosine formation. Amino-acid analysis of a hot alkali insoluble residue (regarded as elastin) from 30-day-old cultures gave a profile identical with neonatal rat aortic elastin in vivo. Insoluble collagen formation in the cell layer tended to plateau after the log phase of growth was completed (10 days). Proteoglycans were found predominantly in the supernatant media. Glycosaminoglycan analysis revealed a profile of dermatan sulphate (32%), chondroitin 4-sulphate (43%), keratan and heparan sulphate (30%), with only a trace of hyaluronic acid. This study indicates that primary cultures of neonatal rat aortic smooth muscle cells remain differentiated in culture and have the unique capacity to continue to synthesize and deposit large amounts (mg) of insoluble elastin which aggregate and from elastic fibres in vitro.

Animals↗
PubMed1981

In vitro studies of elastin metabolism.

Neonatal pig and rat aortas were studied for their ability to synthesize elastin in an in vitro situation. Smooth muscle cells from the rat aorta produced excellent multilayered cultures and produced soluble elastin (tropoelastin), insoluble elastin, and small amounts of collagen. BAPN proved to be toxic to these cells, adversely affecting the level of extracellular protein production. Tissue minces from pig aorta continued to synthesize elastin for two hours after removal. However, a 24 hour study indicated that elastin synthesis had almost completely shut down and that collagen synthesis continued in an apparently normal fashion. It is concluded that in vitro elastin synthesis is an extremely sensitive process easily altered by culture conditions and the addition of extraneous substances such as BAPN, and also highly influenced by the past history of the smooth muscle cells involved.

Animals↗
PubMed1975

Characterization of the collagen synthesized by cultured cartilage cells.

Cartilage cells from embryonic chick cartilage were grown in primary cultures. The cell layer was sequentially extracted with neutral saline, mercaptoethylamine and pepsin which revealed that these cells produced salt-soluble and salt-insoluble collagen. The alpha1- to alpha2-chain ratio was determined for the collagen extracted from the cultured cells and was found to be 13 to 1. Further analysis of the molecule was carried out by CNBr cleavage of the salt-extracted collagen and separation of resulting peptides by ion-exchange chromatography. It was shown that the cultured cartilage cells synthesize collagen of the type (alpha1[II])3.

Amino Acids↗