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Biomedical subjects

K T Paige

Publications and source records attributed to K T Paige.

7 recordsLinked to original sources
PubMed1996

De novo cartilage generation using calcium alginate-chondrocyte constructs.

These studies investigated the utility of calcium alginate as a biocompatible polymer matrix within which large numbers of chondrocytes could be held successfully in a three-dimensional structure and implanted. Further, the ability of chondrocyte-calcium alginate constructs to engraft and generate new cartilage was examined. Chondrocytes isolated from calf shoulders were mixed with a 1.5% sodium alginate solution to generate cell suspensions with densities of 0, 1.0, 5.0, and 10.0 x 10(6) chondrocytes/ml. The cell suspensions were gelled to create disks that were placed in subcutaneous pockets on the dorsums of nude mice. The alginate concentration and CaCl2 concentration used to make the disks also were varied. A total of 20 mice were implanted with 67 bovine chondrocyte-calcium alginate constructs. Samples with an initial cellular density of at least 5.0 x 10(6) chondrocytes/ml demonstrated gross cartilage formation 12 weeks after implantation. Cartilage formation was observed microscopically in specimens with a cellular density as low as 1.0 x 10(6) chondrocytes/ml. The histoarchitecture of the new cartilage closely resembled that of native cartilage. Cartilage formation was independent of CaCl2 concentration (15 to 100 mM) or alginate concentration (0.5% to 4.0%) used in gel polymerization.

Alginates↗
PubMed1995

Injectable cartilage.

Slowly polymerizing calcium alginate gels were investigated as a means of delivering large numbers of isolated chondrocytes by means of injection to determine if these gels would promote engraftment and could provide three-dimensional templates for new cartilage growth. Chondrocytes isolated from the articular surface of calf forelimbs were added to a 1% sodium alginate dissolved in a 0.1 M potassium phosphate buffer solution (pH 7.4) to generate a final cellular density of 10 x 10(6)/ml (representing approximately 10 percent of the cellular density of human juvenile articular cartilage). The calcium alginate-chondrocyte mixture was injected through a 22-gauge needle in 100-microliters aliquots under the panniculus carnosus on the dorsum of nude mice and incubated for 6 (n = 4), 8 (n = 11), and 12 (n = 12) weeks in vivo. Time-zero specimens (n = 10) consisting of 100-microliters aliquots of the calcium alginate-chondrocyte mixture were used to calculate initial weight. At harvest, all calcium alginate-chondrocyte specimens exhibited a pearly opalescence and were firm to palpation as early as 6 weeks after injection. By 12 weeks of in vivo incubation, the specimens weighed 0.15 +/- 0.04 gm, significantly more than the initial weight of 0.11 +/- 0.01 gm (p < 0.05). Specimens stained with hematoxylin and eosin demonstrated lacunae within a basophilic ground-glass substance. Control specimens of calcium alginate without chondrocytes (n = 4) had a doughy consistency 12 weeks after injection and had no histologic evidence of cartilage formation.(ABSTRACT TRUNCATED AT 250 WORDS)

Alginates↗
PubMed1994

Experimental tracheal replacement using tissue-engineered cartilage.

The authors tested the feasibility of using tissue-engineered cartilage, grown in the shape of cylinders, for replacing large circumferential defects of the cervical trachea in rats. Chondrocytes obtained from the shoulder of newborn calves were seeded onto a synthetic nonwoven mesh, 100 microns thick, of polyglycolic acid fibers 15 microns in diameter, cut into pieces of 2.5 x 4 cm. Twenty cell-polymer constructs were wrapped around silastic tubes and implanted into 10 nude mice for 4 weeks. Specimens were then excised and evaluated grossly and histologically for the presence of new cartilage, and biomechanically for their ability to resist collapse upon application of negative pressure. Six cylinders of tissue-engineered cartilage were then sutured into large circumferential defects created in the cervical tracheas of nude rats to replace the excised trachea. Implantation of cell-polymer constructs resulted in the formation of cylinders of hyaline cartilage. When placed within the lumen of a segment of bowel denuded of its mucosal lining, the hollow cylinders resisted collapse in all instances upon administration of negative 200 mm Hg pressure. The cartilage was grossly and histologically identical to that from which the cells had been initially isolated. Four of the six animals receiving these cartilage cylinders as tracheal replacements survived the procedure and were able to breathe in an unassisted fashion. Three of these animals never recovered fully from the anesthetic and the operation, and expired at 24, 48, and 72 hours. The fourth animal fully recovered from the procedure, and breathed spontaneously for 1 week, with no apparent limitations. Increasing respiratory distress then developed, and the animal died.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Endoscopic treatment of vesicoureteral reflux with a chondrocyte-alginate suspension.

Injection of polytetrafluoroethylene (Teflon) or collagen has been used in the endoscopic treatment of vesicoureteral reflux. Although the principle of an endoscopic treatment is valid, there are concerns regarding the long-term safety and effectiveness of these substances. In search of a different injectable material we conducted experiments using chondrocytes in a biodegradable polymer solution for the treatment of vesicoureteral reflux in an animal model. Reflux was created in 4 mini-pigs and confirmed with a cystogram. Cartilage was obtained from the auricular surface of each animal. Chondrocytes were harvested and expanded in vitro. The cells were individually quantitated and concentrated to 40 million cells per cc. The cell suspensions were mixed with a sodium alginate and calcium sulfate solution. Each pig was injected unilaterally in the subureteral region with the autologous chondrocyte suspension. The opposite ureter served as an internal control in all animals. Cystograms showed resolution of reflux in the treated side and persistence of reflux in the opposite untreated side in each instance. Excretory urograms revealed no evidence of obstruction. Histological examination of the subureteral region demonstrated cartilage. Autologous chondrocytes can be readily harvested, expanded in vitro and injected cystoscopically. The cells survive and form a cartilage nidus that is nonantigenic. This system is able to correct reflux without any evidence of obstruction.

Alginates↗
PubMed1994

Comparison of artifact from craniomaxillofacial internal fixation devices: magnetic resonance imaging.

This study compares artifact from craniomaxillofacial internal fixation devices in magnetic resonance images and examines heating and magnetic deflection effects on these devices. Stainless steel wires, microfixation plates of vitallium and titanium, and minifixation and mandibular reconstruction plates of stainless steel, vitallium, and titanium were evaluated. The plates were mounted on a dry skull and submerged in dilute copper sulfate solution. All images were obtained in duplicate by two independent, nonblinded teams of observers with a 1.5-T Signa magnetic resonance system. Each team ranked artifact size for each material by computerized measurement. The rank order of artifact size for each material within each fixation system group and between fixation groups was identical between the two teams. Bath and plate temperatures were recorded before and after imaging. Artifact production was related to hardware size and composition. Titanium hardware caused the least amount of "black-hole" artifact. Vitallium and stainless steel fixation devices of similar size produced significantly more artifact. No significant heating or magnetic deflection effects were seen with any of the fixation devices.

Artifacts↗
PubMed1993

Injectable alginate seeded with chondrocytes as a potential treatment for vesicoureteral reflux.

Injection of polytetrafluoroethylene (Teflon) or collagen has been used in the endoscopic treatment of vesicoureteral reflux. Although the principle of an endoscopic treatment is valid, there are concerns regarding the long-term safety and effectiveness of these substances. The goal of several investigators has been to find alternate implant materials that would be safe for human use. Toward this goal we conducted a study to determine the effect of chondrocytes using a biodegradable polymer solution as a template. Hyaline cartilage was obtained from the articular surfaces of calf shoulders and chondrocytes were harvested. Chondrocyte suspensions were concentrated to 20, 30 and 40 x 10(6) cells per cc and mixed with dry alginate powder (a biodegradable polymer) to form a gel. Twelve athymic mice were injected subcutaneously with a chondrocyte-alginate solution. Each mouse had 4 injection sites, consisting of control, 10, 15 and 20 x 10(6) chondrocyte cells (48 injection sites). Mice were sacrificed at 2, 4, 6 and 12 weeks after injection. Histological examination of the injection sites demonstrated evidence of cartilage formation in 34 of the 36 experimental injection sites. Gross examination of the injection sites with increasing time showed that the polymer gels were progressively replaced by cartilage. The ultimate size of the cartilage formed was related to the initial chondrocyte concentration injected, and appeared to be uniform and stable within each category. There was no evidence of cartilage formation in the 12 controls. Histological analyses of distant organs showed no evidence of cartilage or alginate gel migration, or granuloma formation. In conclusion, chondrocyte-alginate gel suspensions are injectable, appear to be nonmigratory and are able to conserve their volume. In addition, the use of autologous cartilage cells would preclude an immunological reaction. These preliminary studies indicate that autologous cartilage-polymer gel solutions may be potentially useful in the endoscopic treatment of reflux.

Alginates↗