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Biomedical subjects

G Naughton

Publications and source records attributed to G Naughton.

18 recordsLinked to original sources
PubMed1999

A method for tissue engineering of cartilage by cell seeding on bioresorbable scaffolds.

This chapter describes a method for the in vitro generation of a 3-dimensional cartilage matrix from articular chondrocytes seeded onto a bioresorbable polymeric scaffold. This particular growth system was chosen for the subject of this chapter owing to the relative simplicity of the methods required and the ease with which the necessary materials can be obtained. The tissue produced using this protocol is a cellular, metabolically active hyaline-like matrix, containing the major cartilage constituents: sulfated proteoglycan, collagen type II, and water. It serves as a useful in vitro tool for studying the influence of various mechanical and chemical factors on cartilage metabolism, as well as providing an implantable material for in vivo cartilage repair studies.

Animals↗
PubMed1998

Examination of the self-selected fluid intake practices by junior athletes during a simulated duathlon event.

Thirty-two elite junior athletes in two age categories, older than or equal to 15 years old (O15) (8 females and 9 males) and less than 15 years old (U15) (8 females and 7 males), performed a laboratory-based duathlon (run-ride-run). At the completion of the event, significant body mass losses were recorded for all groups. Compared with the other three groups, the O15 males lost body mass at a greater absolute rate (1.26 +/- 0.06 kg.hr-1 vs. a mean of 0.62 +/- 0.11 kg.hr-1 for the other three groups) and a greater relative rate (1.95 +/- 0.10%BM.hr-1 vs. a mean of 1.23 +/- 0.19%BM.hr-1 for the other three groups) (p < .05). No differences were observed between groups for fluid consumption. Subjects consumed more fluid (p < .05) during the cycle phase and postevent than preevent or during the run phases. Results indicated that the athletes' fluid intake practices were insufficient to maintain adequate hydration during the simulated event.

Adolescent↗
PubMed1998

Moderate exercise during growth in prepubertal boys: changes in bone mass, size, volumetric density, and bone strength: a controlled prospective study.

Cross-sectional studies of elite athletes suggest that growth is an opportune time for exercise to increase areal bone mineral density (BMD). However, as the exercise undertaken by athletes is beyond the reach of most individuals, these studies provide little basis for making recommendations regarding the role of exercise in musculoskeletal health in the community. To determine whether moderate exercise increases bone mass, size, areal, and volumetric BMD, two socioeconomically equivalent schools were randomly allocated to be the source of an exercise group or controls. Twenty boys (mean age 10.4 years, range 8.4-11.8) allocated to 8 months of 30-minute sessions of weight-bearing physical education lessons three times weekly were compared with 20 controls matched for age, standing and sitting height, weight, and baseline areal BMD. Areal BMD, measured using dual-energy X-ray absorptiometry, increased in both groups at all sites, except at the head and arms. The increase in areal BMD in the exercise group was twice that in controls; lumbar spine (0.61 +/- 0.11 vs. 0.26 +/- 0.09%/month), legs (0.76 +/- 0.07 vs. 0.34 +/- 0.08%/month), and total body (0.32 +/- 0.04 vs. 0.17 +/- 0.06%/month) (all p < 0.05). In the exercise group, femoral midshaft cortical thickness increased by 0.97 +/- 0. 32%/month due to a 0.93 +/- 0.33%/month decrease in endocortical (medullary) diameter (both p < 0.05). There was no periosteal expansion so that volumetric BMD increased by 1.14 +/- 0.33%/month, (p < 0.05). Cortical thickness and volumetric BMD did not change in controls. Femoral midshaft section modulus increased by 2.34 +/- 2. 35 cm3 in the exercise group, and 3.04 +/- 1.14 cm3 in controls (p < 0.05). The growing skeleton is sensitive to exercise. Moderate and readily accessible weight-bearing exercise undertaken before puberty may increase femoral volumetric BMD by increasing cortical thickness. Although endocortical apposition may be a less effective means of increasing bone strength than periosteal apposition, both mechanisms will result in higher cortical thickness that is likely to offset bone fragility conferred by menopause-related and age-related endocortical bone resorption.

Age Determination by Skeleton↗
PubMed1997

Evaluation of matrix scaffolds for tissue engineering of articular cartilage grafts.

Injury to articular cartilage predisposes that joint to further degeneration and eventually osteoarthritis. Recent studies have demonstrated the feasibility of using chondrocytes together with different biomaterial carriers as grafts for the repair of cartilage defects. The following study was undertaken to determine the effect of a variety of these materials on chondrocyte growth and extracellular matrix synthesis. We cultured chondrocytes on several commonly used materials and compared their rates of synthesis of proteoglycan and collagen. Additionally, we evaluated them in a closed culture recirculating system on these materials and compared them with standard culture techniques. This was done to see whether such a bioreactor-type system can be used to enhance the quality of in vitro reconstructed tissues. Our results demonstrated marked variability with respect to how chondrocytes responded to culture on the various materials. Bioabsorbable polymers such as polyglycolic acid (PGA)--enhanced proteoglycan synthesis, whereas collagen matrices stimulated synthesis of collagen. The use of the closed culture system, in general, improved the rates of synthesis of collagen and proteoglycan on the different material scaffolds. Exceptions were collagen synthesis on collagen matrices: use of the closed culture system did not enhance the rate of synthesis. Rates of proteoglycan synthesis on PGA scaffold initially was higher in the closed culture system but did not sustain a difference over the entire course of the 3-week culture period. This study demonstrates the importance of carrier material for the purpose of cartilage tissue reconstruction in vitro.

Biocompatible Materials↗
PubMed1997

A metabolically active human dermal replacement for the treatment of diabetic foot ulcers.

Tissue engineering, the science of growing living human tissues for transplantation, promises to revolutionize aspects of medical care. Ulcers of the skin of the feet of diabetic patients are a serious health problem and a major cause of amputations. Dermagraft, a tissue-engineered, living human dermal tissue, which provides normal growth factors and matrix proteins, has been implanted to replace a patients' destroyed dermises and heal these ulcers. Large-scale clinical studies and in vitro experiments have demonstrated the importance of controlling specific product parameters, especially the metabolic activity of the tissue, to provide, upon implantation into the wound bed, a living tissue that facilitates healing. Implanting tissue within a defined therapeutic range of metabolic activity dramatically improves healing of diabetic foot ulcers, with significantly more ulcers healed completely in a shorter time. In this new, rapidly moving science, such elucidation of the mechanism of action is vital to ensure that tissues will provide their intended benefit.

Collagen↗
PubMed1994

Performance characteristics of children using various braking resistances on the wingate anaerobic test.

This study examined the performances of children exercising against varying braking forces in short-term, all-out cycling tests. The braking force resistances were 0.04, 0.065, 0.075, and 0.08 kiloponds for every kilogram of body mass (kp.kgBM-1). Results for the peak and mean power performances in 30 s Wingate Anaerobic Tests (WAnT) were recorded for a wide age range of male and female children [6 (n = 23), 8 (n = 19), 10 (n = 19), and 12 (n = 14) years of age]. Univariate ANOVAs with repeated measures on resistance, and Newman Keuls post hoc analysis tests revealed that the absolute peak and mean power responses of the children increased incrementally with age and demonstrated very few sex differences. The overall meaned peak and mean power values of the four resistances and age groups were 161, 231, 242 and 248 Watts and 130, 183, 189, and 196 Watts, respectively. In all of the age groups the three higher resistances (0.065, 0.075, and 0.08 kp.kgBM-1) produced significantly higher peak and mean power performances than did the 0.04 kp.kgBM-1 resistance. The overall meaned relative peak and mean power values of the four resistances and age groups were 4.9, 6.9, 7.4 and 7.4 W.kg-1 and 4.2, 5.2, 5.7 and 6.2 W.kg-1, respectively. Among the three higher resistances there was no one resistance which elicited a significantly more powerful performance.

Age Factors↗
PubMed1992

Determining the variability of performance on Wingate anaerobic tests in children aged 6-12 years.

In two parts, this study investigated variability of performance in Wingate anaerobic tests (WAnTs) of normal, healthy, male children aged six, eight, ten and twelve years. The purpose of the first part of the study was to investigate the mean coefficient of variation (C.V. = [S.D./X].100) of children who performed four WAnTs over a period of four weeks. The results revealed age-related differences in the performance data of peak power (PP) and mean power (MP) but no differences between age groups in fatigue index (FI%) = [PP-Pend)/PP.100]. C.V. data from this group of children did not differ significantly between ages in any of the dependent variables. Coggan and Costill (5) measured the variability of male adults during 30 seconds of highly intense cycling and reported C.V.s in PP and MP performances of 6.7 and 6.5%, respectively. C.V.s of children in the first part of the present study were 7.3 and 6.8% for PP and MP, respectively. The C.V. in the FI% of the children (26.7%) however differed substantially from the previously studied adults (10.3%). The second part of the study was conducted to examine the C.V. in FI% performances of children in the WAnT. The purpose of this part of the study was to examine the extent to which a computerized onscreen game, which was linked to pedal cadence affected the variability of children performing WAnTs. A significant decrease was obtained in the C.V. of the FI% in the presence of the computerized feedback game (16.3 and 23.6, with and without the game, respectively). It is suggested that game-based testing procedures may ensure more consistent result in the assessment of pediatric populations.

Anaerobic Threshold↗
PubMed1992

Evaluation of a biodegradable matrix containing cultured human fibroblasts as a dermal replacement beneath meshed skin grafts on athymic mice.

Meshed, expanded split-thickness skin grafts (MSTSG) frequently achieve poor results when used to cover full-thickness wounds. Poor cosmetic and functional results occur in part because the epithelium that grows across the skin graft interstices lacks a dermis. We used a living dermal replacement composed of either polyglycolic acid (PGA) or polyglactin-910 (PGL) mesh containing confluent, cultured human fibroblasts. These grafts were applied to full-thickness wounds on athymic mice; widely expanded, 3:1 ratio human MSTSG was then placed over the dermal graft. Histologic examination of wounds during a 99-day period after graft placement showed that PGA/PGL-fibroblast grafts vascularized to the wound, and the MSTSG simultaneously vascularized to the PGA/PGL-fibroblast graft. Epithelialization from the MSTSG bridges proceeded rapidly across the surface of the PGA/PGL-fibroblast grafts, resulting in an epithelialized layer that covered a densely cellular substratum that resembled dermis. Basement membrane formation at the dermal-epidermal junction of the epithelialized interstices was confirmed by immunohistochemical microscopy. Minimal inflammatory reaction to the PGA/PGL-fibroblast grafts was seen. Grafts composed of PGA or PGL biodegradable meshes combined with cultured fibroblasts vascularize in full-thickness wounds, resulting in formation of organized tissue beneath the epithelialized surface that resembles dermis.

Animals↗
PubMed1991

In vivo optimization of a living dermal substitute employing cultured human fibroblasts on a biodegradable polyglycolic acid or polyglactin mesh.

The design of a skin-substitute must address the need for a dermal component, as this mesenchymally-derived tissue is important in maintaining the integrity and function of skin. An in vivo study was undertaken to assess the use of two biodegradable meshes, polyglycolic acid and polyglactin-910, as carriers for cultured human fibroblasts in a living dermal replacement. The consistent vascularization and epithelialization of these grafts placed on athymic mice showed that this has potential in re-creating the dermis in a skin-substitute.

Animals↗
PubMed1985

A histological, immunological, and electron microscopic study of bovine collagen implants in the human.

The histological fate of an injectable form of type I bovine dermal collagen (Zyderm collagen implant) in the human dermis and subcutaneous tissue has been studied. Sequential biopsies were analyzed by hematoxylin-eosin and Weigert's stains, by immunofluorescence (using a highly specific rabbit anti-Zyderm collagen antibody and a specific anti-human type III collagen antibody), and by electron miscroscopy. The results of this study suggest that the bovine implant material stimulates a host response resulting in implant degradation and replacement by newly generated host collagen.

Adult↗
PubMed1983

Bovine collagen implant: histologic chronology in pig dermis.

The histologic fate of an injectable form of type I bovine dermal collagen (Zyderm Collagen Implant, ZCI) in the pig dermis and subcutaneous tissue has been studied. Biopsies were taken sequentially and analyzed by hematoxylin and eosin (H&E) and Weigert's stain, by birefringence, by direct immunofluorescence (using a highly specific rabbit anti-Zyderm antibody), and by electron microscopy. The implant material was found to stimulate a host response resulting in implant degradation and replacement by newly generated host collagen.

Animals↗