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Biomedical subjects

J W Alexander

Publications and source records attributed to J W Alexander.

At least 55 records · Page 3Linked to original sources
PubMed1998

Optimal location of a single distal interlocking screw in intramedullary nailing of distal third femoral shaft fractures.

OBJECTIVE: This biomechanical study was done to determine the effect of the level of a single distal screw in a static intramedullary (IM) femoral nail on the stability of fixation of a fracture in the distal third of the femur. DESIGN: Fifteen composite fiberglass femora were osteotomized transversely in the distal third of the femur. A Grosse-Kempf nail was implanted into the femurs, which were divided into three groups of five specimens. Single screw distal nail locking was varied distal to the osteotomy site for each group at 2.5, 5.0, and 7.5 centimeters, respectively. INTERVENTION: All instrumented femurs were mounted on a servohydraulic testing machine and fitted with transducers to measure axial, rotational, and bending displacements. Specimens were cyclically loaded (one hertz) in simultaneous torsion (moment: +/- 10 newton-meters) and axial compression (amplitude: 2,000 newtons) for 500 cycles with a 250-pound abductor force. MAIN OUTCOME MEASUREMENT: Data from linear and rotational transducers were sampled at 100 hertz for five cycles before cycling, every 100 cycles of loading, and immediately after cycling. Custom computer software was developed to convert transducer signals into static and dynamic measurements of axial motion (in millimeters), rotation (in degrees), and angulation (in degrees). RESULTS: Osteotomy site dynamic rotation increased significantly in specimens locked at 7.5 centimeters when compared with the 2.5-centimeter group. There was minimal difference between the stability of the 5.0-centimeter and 7.5-centimeter groups. There was no significant change in position at the fracture site before or after cyclic loading with respect to axial shortening, rotation, or bending. Both dynamic axial and angular displacements were also unaffected by screw position. CONCLUSION: The location of a single distal interlocking screw in static IM nail fixation of distal third femur fractures can significantly affect rotational stability but not axial or angular fixation.

Biomechanical Phenomena↗
PubMed1998

Rapid and prolonged impairment of gut barrier function after thermal injury in mice.

Loss of gut barrier function after burn injury can be important in the pathogenesis of systemic infections and organ dysfunction. The purpose of this study was to determine how rapidly impairment of gut barrier function occurs after burn injury and how long it persists. BALB/c mice were gavaged with 10(10) (111)In-oxine-labeled Escherichia coli 3 h before inflicting a 20% total body surface area burn. They were then killed at 5, 15, 30, 60, 120, or 240 min post-burn. Additional mice were given a 20% or 30% burn injury and were randomized into eight groups, which were killed at either 4 h or 1, 2, 4, 7, 14, or 21 days post-burn. Each mouse was gavaged with 10(10) (111)In-oxine-labeled E. coli 4 h before sacrifice to determine the magnitude of translocation. Gut barrier function was impaired as early as 5 min post-burn and was maximal by 4 h. Rapid improvement was observed by 24 h, followed by slow improvement, but with persistent abnormality through 21 days post-burn. Killing of translocated bacteria was impaired at 4 h and day 7 post-burn, according to the percentage of viable E. coli that remained alive in the tissues. The magnitude of gut dysfunction following burn injury is temporally related.

Animals↗
PubMed1998

Use of tacrolimus eliminates acute rejection as a major complication following simultaneous kidney and pancreas transplantation.

This retrospective study illustrates the efficacy of tracrolimus-based immunosuppression following simultaneous kidney and pancreas transplantation. Between March 1995 and December 1996, 24 simultaneous kidney and pancreas transplant recipients received tacrolimus-based maintenance immunosuppression. All patients received sequential therapy with an antilymphocyte agent, azathioprine, prednisone and tacrolimus. The dose of tacrolimus was adjusted to achieve a whole blood trough level of 8-15 ng/mL (IMx). The mean follow-up was 25 months with a median of 26 months (range 12-33 months). A rise in serum creatinine of > 20% over baseline was investigated with a renal biopsy, after mechanical causes for renal dysfunction had been excluded. Mean serum creatinine concentrations at 3, 6, 12, 18 and 24 months post-transplantation were 1.1, 1.2, 1.3, 1.3 and 1.3 mg/dL respectively. The blood glucose concentrations at the corresponding time period were 115, 94, 95, 93 and 95 mg/dL. Four pancreas allografts were lost (three in the immediate post-transplant period due to thrombosis, and one following iliac artery repair for aneurysm). Transient hyperglycemia requiring treatment was seen in 3 patients. There were four (17%) acute rejection episodes--one of the pancreas allograft alone and three involving the kidney. At a mean follow-up of 25 months, the patient survival and renal allograft survival were 100%, with pancreas allograft survival rate of 78.4% (Kaplan-Meier analysis). Nine (37.5%) patients had evidence of tacrolimus toxicity on renal histology. In conclusion, tacrolimus-based maintenance immunosuppression is associated with stable renal and pancreas allograft function, with freedom from acute rejection in 83% of patients.

Adult↗
PubMed1997

Efficacy of OKT3 as primary therapy for histologically confirmed acute renal allograft rejection.

BACKGROUND: OKT3 is often used as primary treatment for acute renal allograft rejection. In a retrospective study, we sought to determine the efficacy of OKT3 as a first-line agent in reversing histologically confirmed acute renal allograft rejection. METHODS: Patients with mild to moderate, moderate, or severe acute cellular and acute vascular rejection who had not received any other anti-rejection treatment were included in this analysis. A total of 88 patients, who received OKT3 between 1987 and 1995, fulfilled these criteria. RESULT: Seventy of these patients were renal transplant recipients, and 18 were combined kidney and pancreas transplant recipients. The median time to the diagnosis of rejection from transplantation was 32 days (range, 6 days to 13 years). On histology, 6 were graded as mild to moderate, 36 as moderate, 29 as moderate to severe, and 17 as severe rejection. The mean baseline serum creatinine was 1.62 mg/dl (range, 0.7-10.1 mg/dl), and the mean serum creatinine at the time of diagnosis of rejection was 2.60 mg/dl (range, 1.4-12.7 mg/dl) (P=<0.0001). The mean duration of OKT3 treatment was 11.2 days (range, 8-18 days). The mean serum creatinine at the end of OKT3 treatment was 1.73 mg/dl (range, 0.6-5.0 mg/dl; P=0.24 compared with baseline serum creatinine). Rejection was reversed in 86 (98%) patients. Graft survival at 1 year after OKT3 therapy was 87.5% (77 of 88). At a mean follow-up of 38 months, 8 patients had died and 26 grafts were lost. The mean serum creatinine level in the 64 patients with a functioning graft was 1.76 mg/dl (range, 0.8-4.0 mg/dl) at the last follow-up. CONCLUSION: OKT3 when utilized as first-line therapy reversed 98% of the acute rejection episodes, with a 1-year post-OKT3 graft survival of 87.5%.

Acute Disease↗
PubMed1997

Bone marrow and splenocyte coculture-generated cells enhance allograft survival.

BACKGROUND: Protocols that incorporate donor-specific cell infusions using bone marrow, spleen, or blood transfusion continue to enhance allograft survival and often lead to tolerance in experimental models. Clinical benefits from these modalities have not been as striking, leading to ongoing study in this field. We have explored culture techniques for the in vitro selection and development of cellular effectors capable of enhancing allograft survival. METHODS: Rat bone marrow or spleen cells cultured under a variety of conditions were screened for suppressor function. Bone marrow cells, nonadherent to plastic, cultured for 7 days with granulocyte-macrophage colony-stimulating factor, lipopolysaccharide, and with or without splenocytes were found to contain predominantly myeloid lineage cells and had the ability to suppress phytohemagglutinin or mixed lymphocyte reaction-induced splenocyte proliferation. Standard donor-specific peripheral blood transfusion was compared with cultured donor-specific bone marrow cells, splenocytes, or marrow cells cultured with splenocytes (cocultured) administered intravenously at 1 x 10(7) cells/kg the day before an ACI to Lewis heterotopic heart transplant. Cyclosporine was administered at 10 mg/kg on day -1 and 2.5 mg/kg on days 0-6 relative to transplantation. RESULTS: Mean allograft survival in cyclosporine-treated animals was 8.5 days without and 16.6 days with a donor-specific blood transfusion. Cocultured cells extended allograft survival (39.5 days), whereas bone marrow or splenocytes cultured alone did not. With Percoll gradient separation, two predominant culture subfractions, one with potent suppressor function and another with stimulator function, were identified. Flow cytometric analysis showed mixed populations enriched for macrophages but also including dendritic cells in both subfractions. The suppressive fraction extended allograft survival to 20.8 days and the stimulatory fraction was less effective, yet remixing of both fractions regained the full allograft survival advantage. CONCLUSIONS: In this model, the coculture of bone marrow cells and splenocytes with granulocyte-macrophage colony-stimulating factor and lipopolysaccharide produced functionally divergent subpopulations that synergistically enhanced allograft survival. The development of cellular effectors with enhanced ability to prolong allograft survival using in vitro culture techniques is possible, and provides a new therapeutic option in the use of cell infusion-based therapies.

Animals↗
PubMed1997

Neutrophils from burn patients are unable to increase the expression of CD11b/CD18 in response to inflammatory stimuli.

Neutrophils (PMNs) from patients with thermal injury are dysfunctional for the CD11b/CD18-dependent functions of diapedesis, chemotaxis, and phagocytosis. The expression of CD11b/CD18 on normal PMNs is increased after an inflammatory stimulus. We proposed that CD11b/CD18 expression on burn patient PMNs would respond abnormally to inflammatory stimuli. PMNs were obtained from nonseptic burn patients during the second week after thermal injury. PMNs from burn patients incubated with lipopolysaccharide (LPS), N-formyl-methionyl-leucyl-phenylalanine, phorbol myristate acetate, or A23187 did not increase the expression of CD11b/CD18 to the same degree exhibited by normal PMNs. This inability to increase CD11b/CD18 was not due to differences in CD14 receptor expression, LPS binding, or factors present in the serum of burn patients. The upregulation of CD35 also was decreased on burn patient PMNs. Western blot analysis revealed decreased quantities of CD11b protein in burn patient PMNs compared with normal control PMNs. The deficiency in CD11b/CD18 expression after inflammatory stimuli may explain some of the abnormalities observed in burn PMN function.

Burns↗
PubMed1997

Clinical and economic outcomes of expanded criteria donors in renal transplantation.

Although graft and patient survival rates were similar between recipients of kidneys from ECDs and non-ECDs, transplantation with organs from ECDs was significantly more expensive. Multivariate analysis using stepwise linear regression demonstrated length of stay to be a strong proxy for total hospital costs. Inherent tensions between the overall good clinical outcomes associated with the use of ECDs in terms of graft survival and the markedly increased costs seen with these organs are evident.

Age Factors↗
PubMed1997

Effect of dietary ribonucleic acid on bacterial translocationand survival following blood transfusion and thermal injury.

Ribonucleic acid (RNA) has been shown to have a key role in the maintenance of normal cellular function and host resistance to infection. The effect of experimental diets containing RNA on microbial translocation, killing of translocated bacteria and the survival rate of the host was studied in a burn animal model which included immunosuppression. Balb/c mice were fed for 10 days with an RNA supplemented diet (AIN/76A). Control groups were fed with two commercial diets: AIN-76A or Purina chow 5001 (chow). After 10 days of feeding, all animals received an allogenic transfusion. On day 15 the animals were gavaged with 10(10)(14)C radiolabeled or unlabeled Escherichia coli, and given a 20% total body surface area (TBSA) burn injury. Animals gavaged with unlabeled bacteria were observed for survival (n = 60) and animals gavaged with labeled bacteria were sacrificed 4 h post-burn (n = 30) and the mesenteric lymph nodes, liver and spleen were harvested. Slightly less translocation was observed in the liver and spleen of animals fed on RNA diet. Bacterial counts were measured and the percentages of translocated organisms that survived in the tissues were calculated and showed no statistical differences between the three groups. Survival was 45% in RNA group versus 55% in the non-supplemented AIN-76A and 50% in the chow group. It is concluded that a diet enriched in RNA slightly affects bacterial translocation but does not affect survival after severe injury.

Journal Article↗
PubMed1997

A strategy for generating consistent long-term donor-specific tolerance to solid organ allografts.

Current triple drug immunosuppression while effective, increases the risk of opportunistic infection and lymphoproliferative disorders. An alternative strategy would be the generation of donor-specific tolerance with short-term treatment. The use of donor-specific transfusions (DST) with a single brief course of cyclosporine (CsA) and rapamycin (Rapa) has produced promising results in animal models, but falls short of uniform tolerance. It was hypothesized that a DST/CsA/Rapa protocol administered in the perioperative period and redosed at one month might improve on this success in the ACI to Lewis rat heterotopic cardiac transplant model. Recipients received no treatment (group 1), a 1 ml DST intravenously (i.v.) with CsA 10 mg/kg subcutaneously (s.c.) at D-1 and CsA 2.5 mg/kg DO6D+13 (group 2), DST/CsA as dosed above with intraperitoneally (i.p.) Rapa 1 mg/kg D+36D+7 (group 3), DST/CsA/Rapa as above with all components redosed at one month (group 4), DST/CsA/Rapa with only CsA and Rapa repeated (group 5), and DST/CsA/Rapa with CsA redosed and Rapa continued indefinitely (group 6). Comparison of permanent survival (longer than 200 days) between protocols revealed groups 4-6 were significantly greater than control groups 1-3. Donor specificity was verified in group 6, where three permanent survivors received a second cardiac allograft from a Buffalo rat donor and rejected these grafts almost as quickly as untreated strain pair matched controls 21 +/- 1 days vs 30.3 +/- 5 days. Animals from group 6 displayed a greatly reduced mixed lymphocyte response to ACI cells but not to third-party cells. The percentage of T cells producing cytokines was reduced and shifted toward Th-2 type cytokines (IL-4). Thus, a repeated cycle of this brief DST/CsA/Rapa treatment appears to generate consistent permanent graft survival (up to 91%) that exceeds previously studied tolerance inducation protocols and is donor specific.

Animals↗
PubMed1997

Thermal injury induces the development of inflammatory macrophages from nonadherent bone marrow cells.

The normal course of hematopoiesis is controlled by growth factors and cytokines and, therefore, should be susceptible to alterations induced by systemic mediator release such as that seen following thermal injury. We hypothesized that a brief exposure of developing macrophages to the postthermal injury state would result in functionally altered progeny. We measured the production of inflammatory mediators by rat, bone-marrow macrophage precursors harvested 24 h following a 30% TBSA burn after subsequent maturation in a controlled, in vitro environment. Interleukin (IL)-6, tumor necrosis factor (TNF), and prostaglandin (PG) E2 levels in response to 24 h stimulation with lipopolysaccharide (LPS) were measured following 4 or 8 days of incubation with IL-3, granulocyte-macrophage colony-stimulating factor (GM-CSF), or both. Flow cytometric analysis showed that bone marrow cells harvested from burn and sham animals cultured in GM-CSF developed principally into macrophages (His48+, R21A6A+, CD11b+. Unstimulated cells produced negligent levels of cytokines and PGE2. Stimulated burn-derived cells released greater amounts of IL-6 and TNF at 4 or 8 days of culture depending on the conditions. Elevated PGE2 release was noted in all GM-CSF containing cultures, with burn-derived cells showing a trend towards reduced prostaglandin release. Detection of mRNA for cytokines after LPS stimulation showed no change in IL-6 or TNF transcripts. A short exposure to the systemic effects of thermal injury preprogramed macrophage progenitor cells with the propensity to develop into inflammatory macrophages, secreting higher levels of TNF and IL-6. This shift towards proinflammatory functions in these cells suggests they could be a source of enhanced inflammatory mediator release at 4 or more days post thermal injury.

Animals↗
PubMed1997

Arginine, glutamine, and dehydroepiandrosterone reverse the immunosuppressive effect of prednisone during gut-derived sepsis.

OBJECTIVE: Corticosteroids are used broadly in clinical practice but may profoundly impair resistance to infections. In contrast, arginine and glutamine are safe and effective immunonutrients that can improve resistance to infection in both animals and humans. This study assessed whether arginine and/or glutamine, with or without dehydroepiandrosterone, a natural endogenous steroid, could reverse the susceptibility to infection caused by prednisone in a burned animal model. DESIGN: Prospective, randomized study. SETTING: A laboratory approved by the American Association for the Accreditation of Laboratory Animal Care at the Shriners Burns Institute, Cincinnati Unit. SUBJECTS: Adult female Balb/c mice, weighing 18 to 22 g. INTERVENTIONS: Animals were prefed an arginine- and/or glutamine- or a glycine-supplemented diet for 14 days. Dehydroepiandrosterone (25 mg/kg/day) and/or prednisone (10 mg/kg/day) were given on days -4 to 0 before animals were given a gavage of 10(9) 111indium-oxine-radiolabeled or -unlabeled Escherichia coli and 20% total body surface area burn injury. Survival rate and the extent of translocation of E. coli were determined. MEASUREMENTS AND MAIN RESULTS: Feeding with diets supplemented with arginine, glutamine, and arginine plus glutamine and treatment with dehydroepiandrosterone reversed the susceptibility to infections caused by prednisone and burn injury. The beneficial effects were mediated by enhanced killing of translocated bacteria and/or by an improved gut barrier function. CONCLUSIONS: Dietary supplementation can reverse the susceptibility to infections caused by prednisone. Both arginine and glutamine as well as dehydroepiandrosterone may be useful therapeutic agents for preventing infections in steroid-treated patients.

Animals↗
PubMed1997

The effect of blood transfusion on susceptibility to bacterial infection in genetically defined mouse models.

BACKGROUND: Blood transfusions suppress immune function and increase susceptibility to infection, but the effects are not consistent. STUDY DESIGN AND METHODS: Genetically defined mouse strains with the same or different haplotypes were used as blood transfusion recipients and donors. Transfused animals were subjected to cecal ligation and puncture (CLP) and followed for survival or were injected intravenously with Candida albicans to follow clearance of the Candida from the kidneys. RESULTS: BALB/c (H-2d) mice transfused with C3H/HeJ (H-2k) or DBA/2 (H-2d) blood followed by CLP showed significantly lower survival (7 and 10%) than mice transfused with syngeneic blood (61%) or saline controls (56%). Lower survival was also observed in C3H/HeJ (H-2k) mice transfused with BALB/c (H-2d) blood and subjected to CLP (25%) compared with syngeneic transfusion (80%) or saline controls (70%). C57BL/6J (H-2b) mice showed minimal increases in mortality after CLP after transfusion with blood from C3H/HeJ (H-2k) (60% survival), DBA/2 (H-2d) (70% survival), or BALB/c (H-2d) mice (90% survival). When C. albicans was infused intravenously into transfused mice, a similar pattern of altered resistance to infection was found. CONCLUSION: The ability of blood transfusions to increase susceptibility to bacterial infection appears to be dependent on genetic factors unrelated to the major haplotype.

Animals↗
PubMed1997

Does certification mean better performance?

This research addresses the efficacy of certification in nursing in terms of differences in job performance and self-esteem. Study results could help nurse managers determine hiring criteria, design professional development programs and restructure pay scales and reward systems.

Certification↗
PubMed1997

National Delphi study to determine competencies for nursing leadership in public health.

PURPOSE: To identify competencies needed by nurse leaders in public health programs. DESIGN: Five-round national Delphi. SAMPLE: Convenience sample of members of major public health nursing associations and nurse and non-nurse public health leaders in the USA. METHODS: Mailed survey in 1994-1995 using a modified snowball technique based on a modification of the Pew Foundation health professions' competencies for Round 1. Four additional rounds produced consensus. FINDINGS: Initially, 62 competencies were identified. Factor analysis resulted in four factors: political competencies, business acumen, program leadership, and management capabilities; 57 competencies were clustered in the four groupings and accounted for 91.4% of the variance. CONCLUSIONS: Graduate schools in nursing and public health must prepare students with broad-based competencies from a variety of disciplines. Findings of this national survey provide a database for curriculum development and evaluation of programs to prepare nurse leaders for roles in public health-based delivery systems.

Curriculum↗