Biomedical subjects

J A Albright

Publications and source records attributed to J A Albright.

At least 19 recordsLinked to original sources

PubMed2000

Gap junctions in human synovial cells and tissue.

Our objective was to establish the existence of intercellular communication through gap junctions in synovial lining cells and in primary and passaged cultures of human synovial cells. Communication between cells was assessed using the nystatin perforated-patch method, fluorescent dye transfer, immunochemistry, transmission electron microscopy, and immunoblotting. Functional gap junctions were observed in primary and passaged cultures and were based on measurements of the transient current response to a step voltage. The average resistance between cells in small aggregates was 300 +/- 150 MOmega. Gap junctions were also observed between synovial lining cells in tissue explants; the size of the cell network in synovial tissue was estimated to be greater than 40 cells. Intercellular communication between cultured cells and between synovial lining cells was confirmed by dye injection. Punctate fluorescent regions were seen along intercellular contacts between cultured cells and in synovial membranes in cells and tissue immunostained for connexin43. The presence of the protein was verified in immunoblots. Regular 2-nm intermembrane gap separations characteristic of gap junctions were seen in transmission electron micrographs of synovial biopsies. The results showed that formation of gap-junction channels capable of mediating ionic and molecular communication was a regular feature of synovial cells, both in tissue and in cultured cells. The gap junctions contained connexin43 protein and perhaps other proteins. The physiological purpose of gap junctions in synovial cells is unknown, but it is reasonable to anticipate that intercellular communication serves some presently unrecognized function.

Arthritis, Rheumatoid↗

PubMed2000

Effect of soft-tissue trauma on the early periosteal response of bone to injury.

OBJECTIVE: To determine whether the periosteal response to skeletal trauma is impaired when muscle is also injured, thereby providing a possible explanation for why fractures with extensive soft-tissue damage may take longer to heal. METHODS: A bone defect was made in the tibia of male Fisher rats, and the proliferative response, osteoblast concentration, and callus formation that occurred within 7 days were measured in the presence and absence of simultaneously administered model soft-tissue injury (removal of 10% of the anterior tibialis muscle from a region within 2 to 3 mm of the bone defect). Measurements were made by using autoradiography, quantitative histology, and morphometry. RESULTS: Addition of the muscle injury increased proliferation in the cambium and in the fibrous periosteum on day 1, but had no effect thereafter; proliferation of fibroblasts in the loose connective tissue above the periosteum was not affected. Addition of the muscle injury resulted in increased osteoblast levels 2 to 5 days after injury but had no effect on the amount of callus produced. CONCLUSION: The inflammatory milieu created by the muscle injury unexpectedly resulted in an increased periosteal response to skeletal trauma, suggesting that inflammatory mediators generated in response to wounding of soft tissues are unlikely to account for delayed fracture healing. These findings may indicate that surgical trauma associated with internal fixation by using plates and screws may not be as deleterious to the fracture-healing response as previously thought.

Animals↗

PubMed2000

The effect of isometric graft posterior cruciate ligament reconstruction on anterior tibial translation.

Eight fresh-frozen cadaver knees were studied to evaluate whether an isometrically placed posterior cruciate ligament (PCL) graft restores normal posterior tibial translation without overconstraining anterior tibial translation. Each knee was tested with a three-axis load cell in the intact state, after PCL sectioning, and after PCL reconstruction. After PCL reconstruction, posterior tibial displacement was restored to values observed in the intact state for all flexion angles except 60 degrees and 90 degrees. Anterior tibial translation was not significantly changed for any of the three states. These results indicate isometric reconstruction of the PCL significantly reduces posterior tibial translation without overconstraining anterior tibial translation.

Adult↗

PubMed2000

Programmed cell death in post-traumatic bone callus.

Some osteoblasts in the expanded population of periosteal cells that occurs following bone injury are removed from the callus by apoptosis. Our objective was to study whether the consequences of activation of the death program could include feedback control of the healing response. Transforming growth factor beta and interleukin-1beta were delivered together continuously to a standardized tibial defect in rats for 3 days using implanted micro-osmotic pumps. The bones were recovered at 1, 2, 3, 5, 7, 10 and 14 days after injury (n = 6 in each treated and control group) and concentrations of proliferating cells, osteoblasts and apoptotic bodies were determined. The injury-induced apoptotic component of the healing response was shifted in time due to the combined cytokines, compared with vehicle only, with the result that the peak in the concentration of apoptotic bodies occurred 2-3 days earlier in the treated animals. Neither osteoprogenitor proliferation nor osteoblast concentration was affected by addition of the cytokines. The results suggested that activation of apoptosis during injury repair was not necessarily a passive consequence of the cellular response to injury. Programmed cell death could therefore have an active role in modulating bone repair.

Animals↗

PubMed1999

Intracellular signaling mechanisms of interleukin-1beta in synovial fibroblasts.

The possibility that membrane depolarization of synovial fibroblasts caused by interleukin-1beta (IL-1beta) was mediated by protein kinase C (PKC) and Ca2+ influx was studied using inhibitor and activator analysis. The effect of IL-1beta was blocked by bisindolylmaleimide I, an inhibitor of PKC, and by the Ca2+ channel blockers nifedipine and verapamil. In other experiments, PKC was activated using phorbol 12-myristate 13-acetate, and Ca2+ influx was increased by means of a Ca2+ ionophore. Simultaneous application of phorbol ester and Ca2+ ionophore in the absence of IL-1beta mimicked the depolarization caused by IL-1beta. The results were consistent with the hypothesis that, under the conditions studied, activation of PKC and Ca2+ influx are necessary and sufficient processes in the transduction of IL-1beta by synovial cells leading to membrane depolarization. The essential role of protein phosphorylation and Ca2+ influx in the early electrophysiological response of synovial fibroblasts to IL-1beta was therefore established. The role of IL-1beta-induced depolarization in regulating protein expression by the cells remains to be determined, but the results reported here, taken together with observations that protein phosphorylation and Ca2+ influx also mediate the effect of IL-1beta on protease production (1, 2), suggest that electrophysiological changes are actually part of the pathway for expression of proteases in response to IL-1beta.

Animals↗

PubMed1997

Mechanical stability of thoracolumbar pedicle screw fixation. The effect of crosslinks.

STUDY DESIGN: Pedicle screw fixation for unstable thoracolumbar spine injuries is relatively new. The effect of one or two crosslinks on rotational and lateral bending stiffness was studied. OBJECTIVE: To determine the rotational and bending stiffness values of thoracolumbar fractures fixed by the AO's internal fixation system with zero, one, or two crosslinks. METHODS: Eight embalmed thoracolumbar spine segments. (T12-L2) were instrumented at T12 and L2 with a pedicle screw-rod system. Rotational stiffness was determined for 10 cycles to 2.5 degrees, 3.5 degrees, and 5 degrees of rotation, with and without one or two crosslinks, and lateral bending stiffness for 10 cycles to 0.25, 0.40, and 0.50 inch. The results showed a clear trend toward increased stiffness with crosslinks. RESULTS: The stiffness values of the two-crosslink construct at 2.5 degrees and 3.5 degrees of rotation were significantly higher than those of the zero-crosslink system. Also, the bending stiffness of the two-crosslink construct was significantly higher than that of no-crosslink system at all of the displacements. CONCLUSIONS: Rotational stiffness values of the two-crosslink construct were significantly higher than those of the zero-crosslink system, at 2.5 degrees and 3.5 degrees of rotation. Lateral bending stiffness of the two-crosslink system was higher than that of the zero-crosslink system at all levels of displacement.

Biomechanical Phenomena↗

PubMed1997

Electromagnetic fields can affect osteogenesis by increasing the rate of differentiation.

Electromagnetic fields of various kinds can alter osteogenesis in animals with osteotomies and patients with nonunions, but the underlying cellular mechanisms are unknown. The aims of this study were to determine whether I gauss at 60 Hz affected periosteal proliferation and differentiation in either the normal rat tibia or 1 to 14 days after a surgically induced defect. In the injured rats, using histologic study, autoradiography, and morphometry, it was found that exposure for 1 or 3 days had no effect on proliferation but that it produced an increase in osteoblasts 3 days after the injury. Proliferation and differentiation were unaffected by exposure in the absence of injury. The results suggest that the primary effect of the fields was to promote differentiation but not proliferation. Because fields can stimulate proliferation of osteoblastlike cells in vitro, the results of this study may indicate the presence of an in vivo factor that antagonizes the tendency of fields to increase mitotic activity.

Animals↗

PubMed1997

Interleukin-1 beta switches electrophysiological states of synovial fibroblasts.

The role of electro-physiological events in signal transduction of interleukin-1 beta (IL-1 beta) was investigated in rabbit synovial fibroblasts using the perforated-patch method. Aggregated synovial fibroblasts using the perforated-patch method. Aggregated synovial fibroblasts occurred in two different electrophysiological states having membrane potentials (Vm) of -63 +/- 4 (n = 71) and -27 +/- 10 mV (n = 55) (high and low Vm, respectively). IL-1 beta affected the cells with high Vm; it switched the state of the cell from high to low Vm. This effect was strongly dependent on the external potential applied to the cell membrane. Low Vm (-30 mV) alone without IL-1 beta did not switch the state of the cells. Thus a synergistic effect involving the cytokine and cell Vm in switching the electrophysiological state of the cell was shown, indicating that electrophysiological changes are involved in signal transduction. Gap junctions between aggregated cells were necessary for the cells to have a high Vm and to respond to IL-1 beta. Gap junction resistance between adjacent cells was estimated as 300 +/- 100 M omega. Our findings suggest that the electrophysiological behavior of synovial fibroblasts is tightly connected to a signaling or intracellular mediator system that is triggered by IL-1 beta.

Animals↗

PubMed1996

Bone injury response. An animal model for testing theories of regulation.

Therapeutic treatment of bone disease and attempts to accelerate normal healing require knowledge of the soluble factors that control bone repair and the specific effects that they produce. To facilitate study of this regulatory system, an animal model involving creation of a hole in the cortex of the rat tibia was developed. Proliferation, differentiation, and callus formation at the injury site were measured more precisely than in previous animal models by means of autoradiographic, histologic, histochemical, and morphometric methods. Several novel features of bone healing were observed, including the following: (1) synthesis of bone matrix in the defect occurred only after a cambial compartment was established by regeneration of the fibrous periosteum and (2) at least 3 kinds of osteoblasts could be distinguished depending on when and where they deposited calcifiable matrix. The model is well suited to evaluating the use of interventional strategies that involve chemical or electrical agents because the cellular parameters of interest can be measured precisely.

Animals↗

PubMed1995

Anterior screw fixation of type II odontoid fractures. A biomechanical study.

STUDY DESIGN: This study examined the torsional and shear stiffness of Type II odontoid fractures that were stabilized with two 3.5-mm cannulated AO screws or a single 4.5-mm cannulated Herbert screw. OBJECTIVE: To determine the stability of a commonly used two-screw method versus a single-screw fixation method. Insertion of a single screw could make the procedure technically easier. SUMMARY OF BACKGROUND DATA: Biomechanical studies have shown the 4.5-mm Herbert screw to generate greater compressive forces than 3.5-mm cannulated screws, which are commonly used to anteriorly stabilize Type II odontoid fractures. No previous biomechanical studies have compared the shear or torsional stiffness of Type II odontoid fractures stabilized with these screws. METHODS: Twelve cadaver C2 vertebrae were harvested and an osteotomy was performed to simulate a Type II fracture pattern. Six were stabilized with two 3.5-mm cannulated screws, and the remaining were stabilized with a single 4.5-mm cannulated Herbert screw. Each specimen then was tested in torsion through +/- 0.75 degrees, +/- 1.25 degrees, and +/- 1.75 degrees for 10 cycles each. Shear forces then were applied from an anterior to posterior direction to a maximum load of 44.48 N. RESULTS: The mean torsional stiffness for the Herbert screw was 1196 N.m/deg, which was significantly greater than the mean stiffness of the 3.5-mm screw fixation, which measured 434 N.m/deg. The mean shear stiffness for the Herbert screw fixation was 106.9 kN/m, compared to 86.1 kN/m for the 3.5-mm cannulated screw. This was not statistically significant. CONCLUSIONS: The biomechanical properties of the 4.5-mm cannulated Herbert screw suggest it may lend itself for use in fixation of Type II odontoid fractures. With only a single screw to insert, this technically demanding procedure may be less daunting.

Aged↗

PubMed1993

Biomechanical study of C1-C2 posterior arthrodesis techniques.

Fifteen cervical spines from cadavers were used to compare the rotational and translational stability of the Brooks fusion, a fusion construct using Halifax interlaminar clamps, and the Gallie fusion. The Brooks and Halifax clamp constructs exhibited significantly greater rotational and translational stiffness than the Gallie construct (P < 0.001). The Halifax clamp construct exhibited greater rotational stiffness and equal translational stiffness when compared with the Brooks construct (P < 0.05). The Brooks and Halifax fixation constructs provided superior fixation but presented technical challenges. The Gallie construct is less technically demanding but provides less stable fixation.

Biomechanical Phenomena↗

PubMed1993

The use of one compared with two distal screws in the treatment of femoral shaft fractures with interlocking intramedullary nailing. A clinical and biomechanical analysis.

The torsional and compressive biomechanical characteristics of a system for intramedullary fixation with a slotted locking nail and either one or two distal locking screws were evaluated in sixteen femora obtained from eight cadavera. No significant difference was found in the torsional rigidity or axial load to failure when one as opposed to two distal screws had been used. We also managed twenty-seven patients who had a fracture of the femoral shaft with interlocking fixation, using only a single distal screw for distal fixation. The average duration of follow-up was nine months (range, three to twenty-five months). The average time to radiographic healing was three months (range, two to six and one-half months). There were no non-unions or failures of the implant. Clinically unimportant migration of the distal screw occurred in five patients. We concluded that one distal screw provides adequate distal fixation of fractures of the femoral shaft treated with interlocking intramedullary nailing.

Adolescent↗

PubMed1992

Modification of the L'Episcopo procedure for brachial plexus birth palsies.

We reviewed 19 children who had undergone a new modification of the L'Episcopo procedure for obstetric brachial plexus palsy. Through an axillary approach the latissimus dorsi tendon was re-routed anteriorly to the humerus and then anastomosed to the teres major tendon routed posteriorly. At an average follow-up of four years two months, the mean increase in shoulder abduction was 26 degrees and the mean increase in external rotation was 29 degrees. No neurovascular injury or postoperative infection occurred. Two patients had complications, and five did not gain from the procedure. The modified operation was relatively easier to perform and provided excellent cosmesis.

Birth Injuries↗

PubMed1991

Anatomic variations of the blood supply of the soleus muscle.

A total of 36 cadaver and fresh amputation specimens were studied by dissection. Two vascular patterns were identified--a segmental posterior tibial artery (Type 1) and a proximally dominant posterior tibial artery (Type 2). Type 1 was seen in 77.8% of cases, and Type 2 in 22.2%. Injection studies in five fresh specimens demonstrated numerous cross-connections between the two halves of the muscle. A distally based hemisoleus flap should not be performed when a Type 2 vascular pattern is encountered. Also, vascular cross-connections between the two halves of the soleus muscle should be preserved, when possible.

Arteries↗

PubMed1990

Acute compartment syndrome of the thigh: case report.

Compartment syndrome of the thigh is a recognized, yet uncommon, condition characterized by excessive thigh pain following trauma, especially if accompanied by decreasing neurological function. A case is presented in a patient with a subtrochanteric fracture of the femur due to a gunshot wound. Surgical decompression corrected the problem.

Adult↗

PubMed1990

Use of carbon fibers for repair of abdominal-wall defects in rats.

Carbon in the form of 8-micron fibers induces growth of connective tissue. The purpose of this study was to measure and histologically characterize tissue ingrowth occurring in carbon fibers implanted for up to 12 months in abdominal-wall defects in rats, compared with polypropylene mesh. Carbon fibers induced significantly more tissue ingrowth than polypropylene mesh at 6 to 12 months postoperatively. The predominant tissues associated with carbon fibers and polypropylene mesh were dense connective tissue and fat, respectively. Fragmentation of the implants did not occur, and implant debris was not found in the regional lymph nodes. Carbon fibers are potentially useful for reinforcing abdominal-wall defects.

Abdominal Muscles↗

PubMed1990

Biomechanical comparison of slotted and nonslotted interlocking nails in distal femoral shaft fractures.

The torsional and compressive biomechanical characteristics of slotted and nonslotted interlocking nails in distal femoral shaft fractures were evaluated. Slotted (Grosse-Kempf) and nonslotted (Russell-Taylor) locked nail systems were implanted in anatomic specimen femora, which were then tested in torsion and axial compression. For torsional studies, each femur was transversely sectioned distal to the isthmus; for axial loading, a distal 3-cm section of bone was removed. The mean peak torsional stiffness of the femora fixed with nonslotted nails was 0.955 Nm per degree, which was significantly greater than that (0.300 Nm per degree) for the femora fixed with the slotted nails. However, when loaded to failure in compression, the nonslotted nail group failed at a mean load of 2490 N compared with 3050 N for the group fixed with the slotted devices. These results could be due in part to the lesser rigidity of the slotted nail, which may have facilitated greater load sharing with bone and increased resistance to compression failure.

Biomechanical Phenomena↗

PubMed1989

Clinical induction of bone repair with demineralized bone matrix or a bone morphogenetic protein.

Treatment of orthopaedic lesions through induction of bone regeneration has produced promising results in laboratory animals and preliminary human trials. Both demineralized bone powder and bone morphogenetic protein (BMP) are being used clinically to treat bony defects without the need for an autogenous bone harvesting procedure. The historical perspective and laboratory rationale for osteoinduction is presented, as well as current and future clinical applications of demineralized bone powder and BMP.

Animals↗