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Biomedical subjects

R W Jackson

Publications and source records attributed to R W Jackson.

At least 37 records · Page 2Linked to original sources
PubMed2000

Walking, chair rising, and stair climbing after total knee arthroplasty: patellar resurfacing versus nonresurfacing.

During the past decade, the technology and design of knee joint prostheses has progressed considerably. However, there is still much controversy on whether resurfacing the patella during routine total knee arthroplasty (TKA) is necessary. This study compares the biomechanics of the lower limb in patients after TKA with and without patellar resurfacing during level walking, stair climbing, and chair rising. Eighteen patients who underwent TKA by two different surgeons using the same prosthesis were studied after full rehabilitation while walking, stair climbing, and chair rising. Patients were divided between those who were resurfaced and those who were not resurfaced. An aged-matched control population was recruited for comparison. The Hospital for Special Surgery Knee Rating Scale was used to gather clinical information. Kinematic and kinetic parameters were collected using a 5-camera Motion Analysis System and an AMTI OR6-5 force platform. For level walking, patients were asked to walk at a self-selected speed down an 8-m walkway. For stair climbing, patients were asked to climb a 4-step staircase without handrail support and for chair rising, patients were asked to rise from a chair that was positioned at the height of their knee joint line. Five trials for each side were recorded for averaging and statistical analysis. Temporal-spatial parameters and kinematic and kinetic variables at the knee joint were tested for significance using the repeated measures analysis of variance (ANOVA). There were no significant differences in the biomechanics of walking, stair climbing, or chair rising between patients after TKA with and without a resurfaced patella.

Activities of Daily Living↗
PubMed1999

Identification of a pathogenicity island, which contains genes for virulence and avirulence, on a large native plasmid in the bean pathogen Pseudomonas syringae pathovar phaseolicola.

The 154-kb plasmid was cured from race 7 strain 1449B of the phytopathogen Pseudomonas syringae pv. phaseolicola (Pph). Cured strains lost virulence toward bean, causing the hypersensitive reaction in previously susceptible cultivars. Restoration of virulence was achieved by complementation with cosmid clones spanning a 30-kb region of the plasmid that contained previously identified avirulence (avr) genes avrD, avrPphC, and avrPphF. Single transposon insertions at multiple sites (including one located in avrPphF) abolished restoration of virulence by genomic clones. Sequencing 11 kb of the complementing region identified three potential virulence (vir) genes that were predicted to encode hydrophilic proteins and shared the hrp-box promoter motif indicating regulation by HrpL. One gene achieved partial restoration of virulence when cloned on its own and therefore was designated virPphA as the first (A) gene from Pph to be identified for virulence function. In soybean, virPphA acted as an avr gene controlling expression of a rapid cultivar-specific hypersensitive reaction. Sequencing also revealed the presence of homologs of the insertion sequence IS100 from Yersinia and transposase Tn501 from P. aeruginosa. The proximity of several avr and vir genes together with mobile elements, as well as G+C content significantly lower than that expected for P. syringae, indicates that we have located a plasmid-borne pathogenicity island equivalent to those found in mammalian pathogens.

Bacterial Proteins↗
PubMed1999

Effects of race, sex, and socioeconomic status upon cardiovascular stress responsivity and recovery in youth.

Cardiovascular (CV) responsivity to and recovery from acute laboratory stressors, as derived from aggregate scores of CV functioning during and after postural change, video game challenge, social competence interview, and parent-child conflict discussion, were evaluated in 272 youths [mean age 13.5 +/- 2.6 years; 162 Blacks (77 males, 85 females), 110 Whites (60 males, 50 females)], all with a positive family history of essential hypertension. Blacks demonstrated greater systolic and diastolic blood pressure (SBP, DBP) and lower heart rate responsivity compared to Whites (all P values < 0.05). A race by neighborhood socioeconomic status (SES) interaction for SBP responsivity was also observed where low SES Whites and high SES Blacks had the greatest responsivity compared to their same race cohorts. Additionally, upper SES Whites had the lowest total peripheral resistance responsivity. For recovery, Blacks and males exhibited higher SBP during recovery compared to Whites and females, respectively. These findings extend previous studies and provide further support for the hypothesis that recovery from stress is a potentially informative component of the contribution of stress responsivity to cardiovascular disease.

Adolescent↗
PubMed1999

A dispensable region of the chromosome which is associated with an avirulence gene in Pseudomonas syringae pv. pisi.

Pseudomonas syringae pv. pisi comprises a number of races which fall into two phylogenetically distinct groups (designated I and II). Races are based on cultivar specificity in the host plant, pea (Pisum sativum), and are specified by the presence of avirulence genes. The avirulence gene avrPpiA1 is present on the chromosome of all strains examined in race 2, which belongs to phylogenetic group II. A race 4B strain, from phylogenetic group I, lacks this avirulence gene and a comparative study was made of the chromosome in strains representing these two races. A race 2 cosmid clone (pAV270) carrying avrPpiA1 was used as a basis for collinearity analysis of races 2 and 4B. A region of the chromosome amounting to 8.5 kb and including avrPpiA1 was absent from race 4B compared with race 2. A fragment spanning the junction of the discontinuity in race 4B was isolated, cloned and used to delimit the extent of the additional DNA present in race 2. In both races the borders of the discontinuity contained DNA sequences which showed a high degree of conservation. A 7 bp slightly imperfect direct repeat (CCAGC(T)/(A)T) flanked the additional DNA in race 2, with a single copy in race 4B. The region flanking the additional DNA was present in all races of P. syringae pv. pisi. These results confirm the phylogenetic groupings in P. syringae pv. pisi.

Base Sequence↗
PubMed1999

Comparison of iodixanol and iohexol in renal impairment.

Iodixanol (Visipaque, Nycomed, Oslo, Norway) is an iodinated contrast medium in the form of a non-ionic dimer which is iso-osmolar with plasma at all iodine concentrations. There is little evidence regarding its renal tolerance in renal impairment. We therefore undertook a prospective randomized comparison of iodixanol and the non-ionic monomer iohexol (Omnipaque, Nycomed, Oslo, Norway). The serum creatinine was measured pre- and post-angiography in a series of in-patients to establish whether there was any clinically detectable evidence of superiority of iodixanol over iohexol in this high risk group. 8/54 (15%) patients in the iodixanol group had a rise in creatinine of > 10% in the week following angiography compared with 15/48 (31%) in the iohexol group (p < 0.05). The creatinine rise was positively correlated with the dose of both contrast media. These results suggest that iodixanol may be slightly less nephrotoxic than iohexol.

Aged↗
PubMed1999

Walking boot design: a gait analysis study.

This study investigated the effect of various short-leg walking boot designs on walking. Four commercially available walking boots and a synthetic walking cast were tested using three-dimensional gait analysis to determine their effect on a normal individual's gait pattern. Temporal-spatial parameters and lower limb kinematics and kinetics were analyzed for 10 normal subjects. The synthetic walking cast was the most different when compared with the shoe condition with respect to the all parameters tested. The Bledsoe walking boot was the only boot that was not significantly different from the shoe condition for all parameters tested.

Adult↗
PubMed1999

Energy from the electromagnetic spectrum: the future in orthopedic surgery.

The electromagnetic spectrum contains a tremendous amount of energy, which is now being increasingly explored. Lasers of various wavelengths are being and will be developed in the future to treat specific disease conditions. These lasers also will be smaller and cheaper. Radiothermal and electrocautery devices will be developed for other specific purposes. With all of the ablation devices, however, one must remember that there are energy effects that occur deep to the superficial surface, which must be studied and known. Improper use of these strong energies can cause irreversible iatrogenic damage to tissues. Perhaps the greatest potential of electromagnetic (light) energy is the potential to repair rather than resect tissues-in conjunction with different photoactive chemicals. The future is truly exciting, and as Whipple once said, "Developed as a science, applied as a science, and monitored as a science, lasers will serve us extremely well."

Humans↗
PubMed1998

The in vitro induction of human immunodeficiency virus (HIV) replication in purified protein derivative-positive HIV-infected persons by recall antigen response to Mycobacterium tuberculosis is the result of a balance of the effects of endogenous interleukin-2 and proinflammatory and antiinflammatory cytokines.

Coinfection with Mycobacterium tuberculosis and human immunodeficiency virus (HIV) is a serious problem, particularly in developing countries. Recently, M. tuberculosis and purified protein derivative (PPD) were demonstrated to induce HIV replication in CD8 T cell-depleted peripheral blood mononuclear cells from HIV-positive, PPD-positive persons but not in cells from PPD-negative persons. The role of endogenous and exogenous cytokines in modulating M. tuberculosis-induced HIV replication was evaluated. M. tuberculosis-induced HIV replication decreased following simultaneous inhibition of endogenous interleukin (IL)-2, IL-1beta, and tumor necrosis factor-alpha by the addition of soluble receptors and receptor antagonists or following exogenous IL-10 and transforming growth factor (TGF)-beta. In contrast, neutralization of endogenous IL-10 and TGF-beta augmented M. tuberculosis-induced HIV replication by increasing cellular activation. Thus, the balance between IL-2 and proinflammatory and antiinflammatory cytokines plays a major role in M. tuberculosis-induced replication of HIV.

CD8-Positive T-Lymphocytes↗
PubMed1998

Arthroscopic surgery and a new classification system.

Arthroscopic lavage and debridement is of significant value in the earlier stages of arthritis. This is probably through the removal or dilution of enzymes that are part of the degradative process of osteoarthritis. Mechanical problems such as meniscal tears and loose bodies also can be addressed at the same time. However, patients must be selected carefully for arthroscopic treatment. A severity scale is proposed based on clinical and radiological findings that should indicate in advance those patients who will have the greatest opportunity for improvement from an arthroscopic procedure. Critics have said that lavage and debridement does nothing to change the natural history of the disease and is no more than a placebo effect. While there is no strong evidence to suggest that it does modify the natural history of the disease, it definitely improves the quality of life for a significant period of time, with little in the way of complications or morbidity associated with the procedure. The placebo effect might explain some of the results, but the placebo effect is well-known in medicine, and if it does produce a positive result in terms of reduction of symptoms, it cannot be entirely discounted. The biological resurfacing of a joint under arthroscopic control is the challenge facing orthopedic surgeons today. Healing and restoration of articular tissues back to some functional biological state would seem to be a reasonable goal. If this can be achieved, the future will lie in the salvage of joints through arthroscopic procedures rather than the replacement of joints by arthroplasty.

Arthroplasty↗
PubMed1996

Effect of Mycobacterium tuberculosis on HIV replication. Role of immune activation.

The prevalence of Mycobacterium tuberculosis (MTB) has increased worldwide, in part due to the HIV epidemic. Epidemiology data have demonstrated that HIV-infected individuals are more susceptible to MTB disease, which may lead to an acceleration in the progression of HIV disease. The purpose of this study was to determine whether MTB modulates HIV infection in vivo and to delineate the mechanisms involved by using in vitro model systems. Plasma viral load was measured in HIV-infected individuals before, during, and after the development of MTB disease; a 5- to 160-fold increase in viral replication was observed during the acute phase of MTB disease. In order to evaluate the mechanisms involved in this MTB-induced HIV replication, we used an in vitro system of primary PBMC and lymph node mononuclear cells isolated from HIV-infected individuals. The data demonstrated that MTB induced HIV replication in CD8+ T cell-depleted lymphocytes from HIV-infected individuals with a history of purified protein derivative (PPD) positivity but not in those who were PPD negative; this induction of HIV replication correlated with the level of cellular activation. In an in vitro acute HIV infection model, MTB increased HIV replication in PBMC from healthy donors with a history of PPD positivity, but not in PBMC from PPD-negative donors and this induction of viral replication also correlated with cellular activation. In conclusion, MTB increased HIV replication in vivo and in an in vitro model. This MTB-mediated viral production likely occurs through Ag-specific activation and infection of responding T cells.

Acquired Immunodeficiency Syndrome↗
PubMed1995

HIV-1 non-specifically stimulates production of transforming growth factor-beta 1 transfer in primary astrocytes.

HIV-1 expression in monocytes/macrophages can be controlled by transforming growth factor-beta 1 (TGF-beta 1). TGF-beta 1 is present in astrocytes surrounding HIV-1-infected monocyte/macrophages in brain tissue from patients with AIDS but not from seronegative, normal individuals. We sought to determine whether or not production of TGF-beta 1 can be directly stimulated by HIV-1 in astrocytes. Astrocytes from neonatal rat cortex grown in primary culture were exposed to HIV-1 virions for 24 h. One day later, TGF-beta 1 was measured in culture supernatants by a biological assay. HIV-1 caused 1.7-2.1-fold increase in extracellular concentration of TGF-beta 1. TGF beta 1 production also was stimulated by recombinant HIV-1 proteins gp120, p66 and p24. Gp120 labeled with fluorescein was visualized inside astrocytes and its stimulatory effect was not blocked by antibodies against rat CD4. The effect was not specific to HIV-1 and its proteins, because non-opsonized Latex particles and leucine methyl ester (LME) (known to be phagocytosed and endocytosed, respectively, by astrocytes) also stimulated TGF-beta 1 production. The effect was inhibited by two inhibitors of the phago/endocytotic pathway, chloroquine and leupeptin. These results may be relevant to the neuropathogenesis of HIV-1 infection.

Animals↗
PubMed1995

Cross-linking of CD30 induces HIV expression in chronically infected T cells.

CD30, a member of the tumor necrosis factor (TNF) receptor family, is expressed constitutively on the surface of the human T cell line ACH-2, which is chronically infected with human immunodeficiency virus type-1 (HIV)-1. We demonstrate that cross-linking CD30 with an anti-CD30-specific monoclonal antibody, which mimics the described biological activities of the CD30 ligand (CD30L), results in HIV expression. CD30 cross-linking does not alter proliferation of ACH-2 cells and the induction of HIV expression is not mediated by endogenous TNF alpha/beta. Furthermore, cross-linking of CD30 leads to NF-kappa B activation and enhanced HIV transcription. Thus, CD30-CD30L interactions mediate the induction of HIV expression by a kappa B-dependent pathway that is independent of TNF. This mechanism may be important in the activation of HIV expression from latently infected CD4+ T cells, especially in lymphoid organs where cell to cell contact is conducive to receptor-ligand interactions.

Antibodies, Monoclonal↗