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Biomedical subjects

J E Carpenter

Publications and source records attributed to J E Carpenter.

At least 19 recordsLinked to original sources
PubMed2001

Managed care and the evolution of patient rights.

Managed care has grown into the driving force for coordinating and managing healthcare delivery and its financing. At the same time, major initiatives have gained momentum in societal and legislative efforts regarding patient rights. This article provides a historical, legal, and philosophical review of the major events that have shaped the evolution of healthcare services and development of the patient rights issue. As the healthcare industry finds itself in a state of needed reform, the future evolution of managed care in light of the patient rights issue will have important implications for legislators, clinicians, and healthcare organizations as they struggle to provide quality care and improve cost controls.

Humans↗
PubMed2000

Phorbol 12-myristate 13-acetate induces protein kinase ceta-specific proliferative response in astrocytic tumor cells.

Protein kinase C (PKC) activation has been implicated in cellular proliferation in neoplastic astrocytes. The roles for specific PKC isozymes in regulating this glial response, however, are not well understood. The aim of this study was to characterize the expression of PKC isozymes and the role of PKC-eta expression in regulating cellular proliferation in two well characterized astrocytic tumor cell lines (U-1242 MG and U-251 MG) with different properties of growth in cell culture. Both cell lines expressed an array of conventional (alpha, betaI, betaII, and gamma) and novel (theta and epsilon) PKC isozymes that can be activated by phorbol myristate acetate (PMA). Another novel PKC isozyme, PKC-eta, was only expressed by U-251 MG cells. In contrast, PKC-delta was readily detected in U-1242 MG cells but was present only at low levels in U-251 MG cells. PMA (100 nm) treatment for 24 h increased cell proliferation by over 2-fold in the U-251 MG cells, whereas it decreased the mitogenic response in the U-1242 MG cells by over 90%. When PKC-eta was stably transfected into U-1242 MG cells, PMA increased cell proliferation by 2.2-fold, similar to the response of U-251 MG cells. The cell proliferation induced by PMA in both the U-251 MG and U-1242-PKC-eta cells was blocked by the PKC inhibitor bisindolylmaleimide (0.5 micrometer) and the MEK inhibitor, PD 98059 (50 micrometer). Transient transfection of wild type U-251 with PKC-eta antisense oligonucleotide (1 micrometer) also blocked the PMA-induced increase in [(3)H]thymidine incorporation. The data demonstrate that two glioblastoma lines, with functionally distinct proliferative responses to PMA, express different novel PKC isozymes and that the differential expression of PKC-eta plays a determining role in the different proliferative capacity.

Astrocytes↗
PubMed1999

Insulin-like growth factor-1 content and pattern of expression correlates with histopathologic grade in diffusely infiltrating astrocytomas.

Studies of experimental tumorigenesis have strongly implicated signaling of the insulin-like growth factor 1 (IGF-1) as a key component in astrocytic neoplasia; however, its role in the growth of low-grade and malignant human tumors is not well understood. Correlative analyses of IGF-1, p53, and Ki-67 (MIB-1) immunohistochemistry and IGF-1 receptor (IGF-1R) mRNA expression were performed to examine the cellular pattern of IGF-1 signaling in 39 cases of astrocytoma (World Health Organization grades II-IV). Tumor cells expressing IGF-1 and IGF-1R were present in all tumor grades. The proportion of tumor cells that expressed IGF-1 correlated with both histopathologic grade and Ki-67 labeling indices, while expression of IGF-1R mRNA correlated with Ki-67 indices. In cases where stereotactic tissue sampling could be identified with a specific tumor area by neuroimaging features, the numbers of IGF-1 immunoreactive cells correlated with the tumor zones of highest cellularity and Ki-67 labeling. In glioblastomas, the localization of IGF-1 immunoreactivity was notable for several features: frequent accentuation in the perivascular tumor cells surrounding microvascular hyperplasia; increased levels in reactive astrocytes at the margins of tumor infiltration; and selective expression in microvascular cells exhibiting endothelial/pericytic hyperplasia. IGF-1R expression was particularly prominent in tumor cells adjacent to both microvascular hyperplasia and palisading necrosis. These data suggest that IGF-1 signaling occurs early in astroglial tumorigenesis in the setting of cell proliferation. The distinctive correlative patterns of IGF-1 and IGF-1R expression in glioblastomas also suggest that IGF-1 signaling has an association with the development of malignant phenotypes related to aberrant angiogenesis and invasive tumor interactions with reactive brain.

Astrocytoma↗
PubMed1999

Animal models of tendon and ligament injuries for tissue engineering applications.

Improved methods are needed for prevention and treatment of injuries to the musculoskeletal soft tissues. Tissue engineering techniques have led to more effective clinical protocols for treating these injuries. Improvement of tissue healing through the addition of biologic factors, and the development of biologically active tissue engineered replacements, are two promising areas of research. An essential component of progress in this field is the use of animal models of tendon and ligament injuries, which allows for rigorous testing of hypotheses related to disease pathogenesis and treatment. Because these animal models must be appropriate for the condition being studied, no single model exists that is appropriate for all investigations. It generally is necessary to differentiate between tendon and ligament tissues. Furthermore, ligaments should be divided into intraarticular and extraarticular models, whereas tendons should be divided into intrasynovial and extrasynovial models. Other important factors in the appropriate use of an animal model include size of the animal, anatomic features, and techniques available for tissue analysis. The tissues used should be large enough to allow for accurate and reproducible manipulations (injury creation, repair, reconstruction). In addition, it is preferable to use tissues that are amenable to quantitative analysis.

Animals↗
PubMed1999

Harvest of patellar tendon (bone-tendon-bone) autograft for ACL reconstruction significantly alters surface strain in the human patella.

The purpose of this study was to measure the effect of bone-patellar tendon-bone autograft harvest for anterior cruciate ligament (ACL) reconstruction on the surface strain of the human patella. Through progressive removal of bone from the patella, three different defect shapes as well as the intact patella were tested in each of seven knees. Maximum principal strain and corresponding principal direction were determined from each of three gages around the defect for the four conditions (intact plus three defect shapes). There were no statistically significant differences in overall average surface strain between any of the defect shapes. Following graft harvest, overall average strain (all three defects combined) increased in the patella both medial (15 percent increase) and lateral (34 percent increase) to the defect, while decreasing in the region directly proximal (22 percent decrease) to the harvest site compared to the intact patella. A statistically significant 7.5 deg shift of principal direction from longitudinal toward a more transverse (lateral-superior to medial-inferior) direction was observed in the medial region when a shallow-dome defect was made. We conclude that removal of a bone block from the anterior, inferior part of the patella induces a significant redistribution of the surface strain. This results in greater local strain adjacent to the upper border of the bone block increasing the risk for patella fracture. This effect may be of importance in various complications known to occur after ACL reconstruction.

Aged↗
PubMed1997

Biomechanics of the rotator cuff.

Thorough understanding of rotator cuff mechanics is important for effective treatment and/or prevention of cuff injuries. This understanding is achieved through knowledge of normal cuff structure and mechanics. Only then, can the effects of injuries and pathologic processes on normal cuff function be carefuly assessed. Rotator cuff structures are viewed and analyzed on a number of different levels. This article presents current knowledge of rotator cuff mechanics through review of cuff structure and anatomy, corocoacromial arch structure and biomechanics, and biomechanical models.

Acromion↗
PubMed1997

Biomechanical evaluation of current patella fracture fixation techniques.

OBJECTIVE: To compare the mechanical effectiveness of three different techniques for stabilization of transverse fractures of the patella. DESIGN: Cadaveric knees were used to model acute fractures of the patella. To test three treatment techniques in pairs of knees, specimen pairs were assigned randomly to a set of predetermined treatment pairs so as to provide equal numbers of paired and unpaired data sets. Results then were analyzed using a two-way analysis of variance. SETTING: The treatment techniques used are widely applicable in the clinical setting for the treatment of transverse fractures of the patella. No specialized equipment or training is required for the general or subspecialized orthopaedic surgeon. PATIENTS/PARTICIPANTS: None. INTERVENTIONS: Fractures were created in eighteen knees (nine pairs) and repaired by one of three techniques: (a) modified tension band (AO technique); (b) two parallel 4.5-millimeter interfragmentary lag screws; or (c) a new technique using four-millimeter cannulated lag screws with a tension band wired through the screws. MAIN OUTCOME MEASURES: In mechanical testing, the amount of interfragmentary separation in simulated knee extension and the maximum load to failure at 45 degrees of flexion were measured. RESULTS: Fractures stabilized with a modified tension band were found to displace significantly more than those fixed with screws alone or screws plus a tension band in simulated knee extensions (p < 0.05). The fractures fixed with the cannulated screws plus the tension band failed at higher loads (mean = 732 newtons) than those stabilized with screws alone (mean = 554 newtons, p = 0.06) or those with a modified tension band (mean = 395 newtons, p < 0.05). CONCLUSIONS: Combining interfragmentary screw fixation with the tension band principle appears to provide improved stability over the modified tension band or screws alone for transverse patella fractures. Cannulated screws allow for simple, reliable addition of a tension band to screw fixation.

Aged↗
PubMed1996

Coracoacromial ligament: in situ load and viscoelastic properties in rotator cuff disease.

The coracoacromial ligament plays a role in rotator cuff disease. The changes in the in situ load and viscoelastic properties of the coracoacromial ligament in shoulders with rotator cuff tears were evaluated. Coracoacromial ligaments from 16 cadaveric shoulders (8 with rotator cuff tears, 8 without tears) were evaluated via biomechanical testing of bone ligament bone specimens. An in situ load existed in the coracoacromial ligaments of 19.6 +/- 15.4 N (rotator cuff tear) and 18.3 +/- 9.8 N (no rotator cuff tear). This difference was not statistically significant. Cyclic loading of the ligaments demonstrated a greater drop in peak stress in rotator cuff tear shoulders than in normal shoulders, whereas the stress relaxation response was not different. These changes in the coracoacromial ligament in shoulders with cuff tears may be attributable to ultrastructural changes within the ligament as a result of an altered loading environment. It remains unknown whether they occur as a result of a rotator cuff tear or if they contribute to the pathogenesis of cuff disease.

Aged↗
PubMed1994

Fractures of the acromion process: a proposed classification system.

A review of 27 fractures of the acromion process during a 15-year period revealed five distinct types that were classified into three groups. Stress fractures are rare, do not result from acute trauma, and gain little benefit from nonoperative treatment. Type I fractures are minimally displaced. Type IA fractures are avulsion fractures and heal rapidly. Type IB fractures result from direct trauma to the extremity, and are minimally displaced. Most heal with nonoperative treatment. Type II fractures are displaced laterally, superiorly or anteriorly and do not reduce the subacromial space. Most are pain free with full motion after 6 weeks of nonoperative treatment. Type III fractures reduce the subacromial space. This may occur by an inferiorly displaced acromion fracture, or an acromion fracture associated with an ipsilateral, superiorly displaced glenoid neck fracture. Patients in this group sustained significant trauma to the involved extremity. All type III fractures treated nonoperatively develop significant limited shoulder motion with pain, suggesting that early surgical intervention may be indicated.

Acromion↗
PubMed1994

Geometric and mechanical properties of the coracoacromial ligament and their relationship to rotator cuff disease.

One of the most common causes of pain and disability in the upper limb is inflammation of the rotator cuff tendons. When no significant bony abnormality exists in the surrounding structures, the coracoacromial ligament has been implicated as a possible cause of impingement on the cuff tendons. Geometric and mechanical properties of 20 coracoacromial ligaments, 10 from shoulders with rotator cuff tears and 10 from normal shoulders, were accurately determined. In comparing rotator cuff tear and normal specimens, statistically significant changes in geometric properties were measured in the lateral band, but not in the medial band, of the ligament. The lateral band, which is the region most likely to impinge on the rotator cuff, was shorter and had a larger cross-sectional area in specimens with rotator cuff tears. Although there were no statistical differences in structural properties of the ligament between normal and rotator cuff tear groups, significant changes were evident in material properties. Previously reported histologic differences in the ligament in shoulders with rotator cuff tears are supported by the decreased material properties measured in the current study. Whether the differences in the coracoacromial ligament cause impingement or are due to impingement is still unknown at this time.

Acromioclavicular Joint↗
PubMed1994

Shoulder proprioception. Effect of joint laxity, joint position, and direction of motion.

Recently, considerable importance has been ascribed to that portion of shoulder stability which may be provided by active muscle forces. Joint proprioception likely has a considerable role in muscular stabilization of the shoulder by providing information to the central nervous system for the management of muscular activity. Normal human shoulder proprioception has not yet been thoroughly characterized. We have measured shoulder joint proprioception in a population of subjects without known shoulder abnormalities by quantifying the subjects' ability to correctly detect passive shoulder rotation in the abducted shoulder. We have found absolute angular proprioception to range from an average "best" of 0.78 degrees to a "worst" of 1.08 degrees. Individuals who have clinically determined generalized joint laxity are significantly less sensitive in proprioception (P < .002). Detection of external rotation is significantly more sensitive than detection of internal rotation (P < .001). Detection of external rotation becomes significantly more sensitive as the limit of external rotation is approached. We have concluded that these findings suggest capsular tightening as one possible mechanism for shoulder proprioception.

Adult↗
PubMed1994

Fractures of the patella.

Patellar fractures usually occur from distraction and three-point bending of the patella as well as from direct blows. Surgical treatment is necessary for fractures that are displaced more than 2 mm and may include open reduction and internal fixation, partial patellectomy, or rarely, total patellectomy. We have presented a new technique for the stabilization of a simple transverse fracture that has provided superior results in laboratory tests. Postoperative complications can be minimized by good attention to wound care, accurate fracture reduction, secure fracture fixation and an early range of motion. Despite the surgeon's best efforts, however, post-traumatic osteoarthrosis can develop and may require additional treatment.

Fracture Fixation↗
PubMed1993

Pull-out strength of five suture anchors.

Five commercially available suture anchor devices were tested to failure in human cadaveric proximal tibiae. A total of 198 trials were completed. Insertion was uncomplicated for all anchors, with the exception of the Acufex Rod TAG device, with five of 22 (23%) of these breaking upon insertion into thicker cortical bone. Overall, the anchors performed significantly (p < 0.05) better when placed in thicker cortical bone, further away from the joint surface, and when loaded in a direction parallel to the bone surface. The Mitek GII anchor failed (pulled out of bone) less often than the other anchors (19% vs. 46%). In loading perpendicular to the bone surface, the Mitek GII and Statak were the strongest (p < 0.05), with mean loads at failure of 82.5 and 90.2 N, respectively. The Acufex Rod TAG, Acufex Wedge TAG, and Mitek GI failed at 67.2, 65.5, and 49.4 N respectively.

Aged↗
PubMed1993

Electrical stimulation of soft tissues.

It is well-documented that electrical potentials normally are present in biologic soft tissues. The discovery of these has generated interest in effecting a change in the biology of these tissues by externally imposing an electrical field. There is experimental evidence that ligament and tendon repair can be affected by ES, but there have been no clinical studies to demonstrate its effectiveness in human ligament or tendon injuries. The only clinical support for use of ES to enhance soft-tissue healing is for its use in chronic, open dermal wounds. ES has been shown to be effective for these chronic wounds under certain conditions. There is currently insufficient justification for the use of ES for reduction of soft-tissue edema.

Electric Stimulation Therapy↗