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Biomedical subjects

J Oh

Publications and source records attributed to J Oh.

At least 55 records · Page 3Linked to original sources
PubMed2000

Biochemical and molecular approaches to understanding protein import into peroxisomes.

Peroxisomes are eukaryotic organelles that perform diverse and variable functions. Although genetic studies in yeasts and mammals have identified approximately 20 genes (PEX genes) required for the biogenesis of this important organelle, biochemical studies of protein targeting and import have lagged behind and in many cases we have no idea of the function of the PEX gene products (peroxins). Using an import assay in vitro derived from sunflower cotyledon cells and recombinant proteins, we have obtained translocation intermediates on the peroxisome import pathway and are using cross-linking to identify interacting partners. We have also used antibodies raised against human PEX14 to inhibit the import of matrix proteins in this system. To obtain homologous antibodies for inhibition experiments, to immunoprecipitate cross-linked products and to enable us to study the import pathways of peroxins we have cloned and characterized plant orthologues of three PEX genes, PEX6, PEX10 and PEX14.

ATPases Associated with Diverse Cellular Activitie↗
PubMed2000

Nasal carriage of Staphylococcus aureus in families of children on peritoneal dialysis. European Pediatric Peritoneal Dialysis Study Group (EPPS).

Nasal carriage of Staphylococcus aureus is a risk factor for catheter-related infections with S. aureus in patients on chronic peritoneal dialysis (CPD). In children, S. aureus may transmitted to the catheter either from the patients' nares, or from the nares of caregiving carriers. As part of a prospective trial on the efficacy of mupirocin prophylaxis in children on CPD and their caregivers, we evaluated the prevalence of S. aureus carriage in 92 families of pediatric CPD patients. Patients and their caregivers (usually both parents) were screened by three nasal cultures obtained within four weeks. In 62% of the families, neither the patients nor any caregiver carried S. aureus. In 23%, the patient or at least one caregiver (sometimes both) was identified as a carrier. In 15%, at least one caregiver, but not the patient, was colonized with S. aureus. During further follow-up by once-monthly nasal cultures, 5 of the 57 initially negative patients developed S. aureus colonization, and in two families, at least one caregiver turned positive. Including these "occasional" carriers, the cumulative likelihood of one or several family members carrying S. aureus gradually increased to a plateau of about 55% after 6 observation months. Susceptibility rates of cultured S. aureus were 100% for vancomycin, 99% for aminoglycosides, 95% for piperacillin/tazobactam, 94% for cephalosporins, and 15% for ampicillin. In two patients and two caregivers (four different families), methicillin-resistant S. aureus was found. Three isolates from three different families were resistant to mupirocin. We conclude that S. aureus colonization is common in families of children on CPD. While 85% of carrier families are detected by 3 sequential nose cultures in patient and caregivers, up to 9 cultures may be required in "occasional" carriers.

Adolescent↗
PubMed1999

Antibodies against pex14p block ATP-independent binding of matrix proteins to peroxisomes in vitro.

The membrane protein Pex14p is a key component of the protein import machinery of peroxisomes. Antibodies raised against human Pex14p recognise a 66 kDa protein in sunflower glyoxysomes (HaPex14p) and immunoprecipitate in vitro-translated Arabidopsis Pex14p (AtPex14p). These antibodies inhibit the ATP-independent binding to sunflower peroxisome membranes of peroxisome targeting signal type (PTS) 1- and PTS2-targeted matrix proteins, but not an integral membrane protein. These results suggest that Pex14p functions before the ATP-dependent step of peroxisome assembly.

Adenosine Triphosphate↗
PubMed1999

Heterozygous prothrombin gene mutation: a new risk factor for early renal allograft thrombosis.

BACKGROUND: Underlying thrombophilic disorders increase the risk of early allograft loss after renal transplantation. We report three cases of early graft thrombosis in two carriers of a recently discovered prothrombotic variation of the prothrombin gene. CASE REPORTS: The first patient, an adolescent girl, developed multiple thrombotic shunt occlusions after the initiation of hemodialysis until continuous cumarin anticoagulation was instituted. During living-related kidney transplantation, peracute thrombosis of the renal arteries and veins occurred during surgery despite excellent intraoperative conditions and continuous low-dose heparinization. A few hours after reperfusion of the organ by immediate thrombectomy and intrarenal fibrinolysis, an irreversible rethrombosis occurred. A detailed evaluation of the coagulation system showed highly elevated prothrombin protein activity and concentrations. A heterozygous G-->A transition at position 20210 of the prothrombin gene was identified. Hemodialysis was resumed using recombinant hirudin, a direct and selective thrombin inhibitor, as an anticoagulant. The second patient, a girl with end-stage renal failure due to atypical hemolytic uremic syndrome, lost two cadaver kidney allografts, each time by massive thrombosis a few days after transplantation. In this patient also, elevated prothrombin activity and concentrations were present and a heterozygous G-->A transition at position 2210 of the prothrombin gene was detected. CONCLUSIONS: The prothrombin gene mutation is a new risk factor for thrombotic complications both on hemodialysis and after renal transplantation. It may be useful to screen for this disorder in the pretransplant thrombophilia work-up.

Adolescent↗
PubMed1999

Current followup strategies after radical prostatectomy: a survey of American Urological Association urologists.

PURPOSE: Followup care of men who have undergone potentially curative surgical treatment for prostate cancer varies widely among clinicians. To determine current practice patterns we mailed a custom designed questionnaire to American and nonAmerican urologists who were American Urological Association (AUA) members. MATERIALS AND METHODS: Surveys were mailed to a random sample of the approximately 12,000 AUA members, comprising 3,205 Americans and 1,262 nonAmericans. Evaluable surveys were returned by 760 American (24%) and 290 nonAmerican (23%) urologists. Our analysis is based on these 1,050 responses. RESULTS: In generally healthy patients after radical prostatectomy for stages T1 to 2NOMO and T3a to cNOMO prostate cancer the most frequently recommended followup diagnostic tests included office visit with digital rectal examination, serum prostate specific antigen (PSA) and urinalysis. Although there is appreciable variation in the frequency of use of these methods, respondents generally recommended office visit with digital rectal examination, serum PSA and urinalysis every 3 months in year 1, every 6 months in years 2 to 5 and annually thereafter. Other tests, such as serum prostatic acid phosphatase, bone scan, and abdominal and pelvic computerized tomography and magnetic resonance imaging, are rarely recommended. CONCLUSIONS: Our survey provides information regarding current followup strategies recommended by AUA urologists after radical prostatectomy for stages T1 to 2NOMO and T3a to cNOMO disease. Office visits and digital rectal examination, urinalysis and PSA measurement are the main tools that urologists currently use. Although optimal strategy remains unknown, these data permit the rational design of clinical trials of alternate followup strategies based on actual current practice to answer this important question.

Adult↗
PubMed1999

Cytokine molecular adjuvants modulate immune responses induced by DNA vaccine constructs for HIV-1 and SIV.

DNA or nucleic acid immunization has been shown to induce both antigen-specific cellular and humoral immune responses in vivo. Moreover, immune responses induced by DNA immunization can be enhanced and modulated by the use of molecular adjuvants. To further engineer the immune response in vivo, we investigated the induction and regulation of immune responses from the codelivery of Thl cytokines (interleukin-2 [IL-2] and IL-12), Th2 cytokines (IL-4 and IL-10), and granulocyte-macrophage colony-stimulating factor (GM-CSF) genes along with a DNA vaccine construct encoding for simian immunodeficiency virus (SIV) gag/pol proteins. We observed that coinjection with IL-2, IL-4, IL-10, and GM-CSF resulted in increased levels of antigen-specific antibodies. In addition, we found that coinjection with cytokine genes drove the immune responses toward a more Thl or Th2 phenotype. We also observed that coadministration of IL-2, IL-12, and GM-CSF genes resulted in a dramatic enhancement of Th proliferation responses. Moreover, coimmunization with IL-12 genes resulted in a dramatic enhancement of antigen-specific cytotoxic T lymphocyte (CTL) responses. These results support the potential utility of molecular adjuvants in DNA vaccine regimens.

Adjuvants, Immunologic↗
PubMed1999

Dialysis in neonates with inborn errors of metabolism.

BACKGROUND: Certain inborn errors of metabolism become manifest during the neonatal period by acute accumulation of neurotoxic metabolites leading to coma and death or irreversible neurological damage. Outcome critically depends on the immediate elimination of the accumulated neurotoxins. Recent technological progress provides improved tools to optimize the efficacy of neonatal dialysis. METHODS: We report our experience with continuous venovenous haemodialysis (CVVHD) in six neonates with hyperammonaemic coma due to urea-cycle disorders or propionic acidaemia and in one child with leucine accumulation due to maple-syrup urine disease (MSUD), in comparison with five patients managed by peritoneal dialysis (PD) (2 hyperammonaemia, 3 MSUD). Application of a new extracorporeal device specifically designed for use in small children permitted the establishment of stable blood circuits utilizing small-sized catheters, and the tight control of balanced dialysate flows over wide flow ranges. RESULTS: Plasma ammonia or leucine levels were reduced by 50% within 7.1 +/- 4.1 h by CVVHD and within 17.9 +/- 12.4 h by PD (P<0.05). Also, total dialysis time was shorter with CVVHD (25 +/- 21 h) than with PD (73 +/- 35 h, P<0.02). A comparison of the CVVHD results with published literature confirmed superior metabolite removal compared to PD, and suggested comparable efficacy as achieved with continuous haemofiltration techniques. Apart from accidental pericardial tamponade during catheter insertion in one case, no major complications were noted with CVVHD. In three of the five PD patients, dialysis was compromised by mechanical complications. None of the MSUD patients but four children with urea-cycle disorders died, two during the acute period and two later during the first year of life, with signs of severe mental delay. Of the eight children presenting with hyperammonaemic coma, the four with the most rapid dialytic ammonia removal rate (50% reduction in < 7 h) survived with no or moderate mental retardation, whereas slower toxin removal was always associated with a lethal outcome. Simulation studies showed that the efficacy of neonatal CVVHD is limited mainly by blood-flow restrictions. CONCLUSIONS: While CVVHD is the potentially most efficacious dialytic technique for treating acute metabolic crises in neonates, utmost care must be taken to provide an adequately sized vascular access.

Humans↗
PubMed1999

Intracellular adhesion molecule-1 modulates beta-chemokines and directly costimulates T cells in vivo.

The potential roles of adhesion molecules in the expansion of T cell-mediated immune responses in the periphery were examined using DNA immunogen constructs as model antigens. We coimmunized cDNA expression cassettes encoding the adhesion molecules intracellular adhesion molecule-1 (ICAM-1), lymphocyte function associated-3 (LFA-3), and vascular cell adhesion molecule-1 (VCAM-1) along with DNA immunogens, and we analyzed the resulting antigen-specific immune responses. We observed that antigen-specific T-cell responses can be enhanced by the coexpression of DNA immunogen and adhesion molecules ICAM-1 and LFA-3. Coexpression of ICAM-1 or LFA-3 molecules along with DNA immunogens resulted in a significant enhancement of T-helper cell proliferative responses. In addition, coimmunization with pCICAM-1 (and more moderately with pCLFA-3) resulted in a dramatic enhancement of CD8-restricted cytotoxic T-lymphocyte responses. Although VCAM-1 and ICAM-1 are similar in size, VCAM-1 coimmunization did not have any measurable effect on cell-mediated responses. These results suggest that ICAM-1 and LFA-3 provide direct T-cell costimulation. These observations are further supported by the finding that coinjection with ICAM-1 dramatically enhanced the level of interferon-gamma (IFN-gamma) and beta-chemokines macrophage inflammatory protein-1alpha (MIP-1alpha), MIP-1beta, and regulated on activation normal T-cell expression and secreted (RANTES) produced by stimulated T cells. Through comparative studies, we observed that ICAM-1/LFA-1 T-cell costimulatory pathways are independent of CD86/CD28 pathways and that they may synergistically expand T-cell responses in vivo.

AIDS Vaccines↗
PubMed1999

A Rational Approach to Selective Recognition of NH(4)(+) over K(+).

An ion-selective electrode (ISE) based on receptor 1 is highly selective for binding NH(4)(+) over K(+) (lg K(NH(4)(+)/K(+))=-2.6); the three imine nitrogen atoms in 1 are ideally positioned for hydrogen bonding with the tetrahedral NH(4)(+) ion. This selectivity is considerably greater than that found for commercial ISEs based on nonactin (lg K(NH(4)(+)/K(+))=-1.0).

Journal Article↗
PubMed1999

Monitoring during and after intravenous conscious sedation.

Monitoring the patient's physiological parameters through clinical observation and information obtained through monitoring devices is important for early detection of problems that can occur during IVCS. The importance of clinical observation is realized when monitoring is described as an art where our eyes, ears, fingers, and even nose gather more information than the instruments we use. Clearly, clinical correlation and appropriate management are necessary for effective patient care because monitoring devices provide only data. In addition to patient care during IVCS, maintenance of monitoring equipment and repair of malfunctioning equipment are important for patient safety. Collection of data through accurate record keeping is valuable for quality assurance as well as in future developments and modification of patient care standards during IVCS.

Blood Pressure↗
PubMed1998

Heme-regulated eIF-2alpha kinase purifies as a hemoprotein.

The regulation of protein synthesis by the availability of heme in reticulocytes is well established. However, the mechanism by which heme regulates translational initiation is not clear. In this study, we have examined the heme regulation directly on the homogeneous heme-regulated eIF-2alpha kinase (HRI), which is activated during heme deficiency. We found that HRI purified as a hemoprotein with the characteristic Soret band of hemoprotein at 424 nm. This HRI was an active autokinase and eIF-2alpha kinase, and its kinase activities were inhibited by submicromolar concentrations of hemin with an apparent Ki of 0.5 microM. Homogeneous HRI was a homodimer, and its activities could not be inhibited by incubation with purified inactive K199R HRI in vitro. Our results suggest that there are two distinct types of heme-binding sites in the HRI homodimer. The binding of heme to the first site is stable, while the binding of heme to the second site is responsible for the rapid downregulation of HRI activity by heme. These results indicate that HRI binds heme and serves as a sensor of the availability of heme to coordinate the balanced synthesis of globins and heme in erythroid cells.

Animals↗
PubMed1998

CD8 positive T cells influence antigen-specific immune responses through the expression of chemokines.

The potential roles of CD8(+) T-cell-induced chemokines in the expansion of immune responses were examined using DNA immunogen constructs as model antigens. We coimmunized cDNA expression cassettes encoding the alpha-chemokines IL-8 and SDF-1alpha and the beta-chemokines MIP-1alpha, RANTES, and MCP-1 along with DNA immunogens and analyzed the resulting antigen-specific immune responses. In a manner more similar to the traditional immune modulatory role of CD4(+) T cells via the expression of Th1 or Th2 cytokines, CD8(+) T cells appeared to play an important role in immune expansion and effector function by producing chemokines. For instance, IL-8 was a strong inducer of CD4(+) T cells, indicated by strong T helper proliferative responses as well as an enhancement of antibody responses. MIP-1alpha had a dramatic effect on antibody responses and modulated the shift of immune responses to a Th2-type response. RANTES coimmunization enhanced the levels of antigen-specific Th1 and cytotoxic T lymphocyte (CTL) responses. Among the chemokines examined, MCP-1 was the most potent activator of CD8(+) CTL activity. The enhanced CTL results are supported by the increased expression of Th1 cytokines IFN-gamma and TNF-alpha and the reduction of IgG1/IgG2a ratio. Our results support that CD8(+) T cells may expand both humoral and cellular responses in vivo through the elaboration of specific chemokines at the peripheral site of infection during the effector stage of the immune response.

AIDS Vaccines↗