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Biomedical subjects

K Park

Publications and source records attributed to K Park.

At least 325 records · Page 18Linked to original sources
PubMed1994

Transplantation of allogeneic peripheral blood stem cells after myeloablative treatment of a patient in blastic crisis of chronic myelocytic leukemia.

A 48-year-old man in blastic crisis of chronic myelocytic leukemia received a transplant of allogeneic peripheral blood stem cells. The donor was his HLA-identical sister, who refused to donate bone marrow cells, but agreed to donate peripheral blood stem cells. The patient received standard transplant conditioning with cyclophosphamide (120 mg/kg) and busulfan (16 mg/kg). Peripheral blood stem cells were mobilized with granulocyte colony stimulating factor and collected by apheresis. After transplantation, the white blood cell count and the result of microscopic analysis of the bone marrow became normal, and the leukocyte karyotype became 46XX. DNA fingerprinting showed complete chimerism. Graft-versus-host disease was suppressed with cyclosporine and methyl-prednisolone. The patient died of recurrence of leukemia on day 102+.

Blast Crisis↗
PubMed1994

Surface modification of polymeric biomaterials by albumin grafting using h-irradiation.

Polymeric biomaterial surfaces were modified by albumin grafting to improve their blood compatibility. Albumin molecules were functionalized by introducing double bonds using glycidyl acrylate. The functionalized albumin was covalently attached to various biomaterial surfaces such as polypropylene, polycarbonate, and poly(vinyl chloride) by h-irradiation. Surface-induced platelet adhesion and thrombus formation on the albumin-grafted surfaces was examined using computer-enhanced video microscopy and scanning electron microscopy. The amount of the grafted albumin was dependent on the h-irradiation dose and the concentration of albumin used for adsorption. The grafted albumin molecules remained on the surface even after exposure to blood for prolonged time periods. This approach was used to graft albumin to polymeric materials of an oxygenator. The albumin grafting resulted in a substantial improvement in blood compatibility as compared to control oxygenators. The covalent grafting of functionalized albumin by h-irradiation obviates the need for premodification of chemically inert polymer surfaces. It is useful for albumin grafting to various biomaterial surfaces.

Acrylates↗
PubMed1994

DNA helicase requirements for DNA replication during bacteriophage T4 infection.

The lytic bacteriophage T4 uses multiple mechanisms to initiate the replication of its DNA. Initiation occurs predominantly at replication origins at early times of infection, but there is a switch to genetic recombination-dependent initiation at late times of infection. The T4 insertion-substitution system was used to create a deletion in the T4 dda gene, which encodes a 5'-3' DNA helicase that stimulates both DNA replication and recombination reactions in vitro. The deletion caused a delay in T4 DNA synthesis at early times of infection, suggesting that the Dda protein is involved in the initiation of origin-dependent DNA synthesis. However, DNA synthesis eventually reached nearly wild-type levels, and the final number of phages produced per bacterium was similar to that of the wild type. When the dda mutant phage also contained a mutation in T4 gene 59 (a gene normally required only for recombination-dependent DNA replication), essentially no DNA was synthesized. Recent in vitro studies have shown that the gene 59 protein loads a component of the primosome, the T4 gene 41 DNA helicase, onto DNA. A molecular model for replication initiation is presented that is based on our genetic data.

Bacteriophage T4↗
PubMed1994

Transforming growth factor-beta: expression in normal and pathological conditions.

Expression of the various isoforms of transforming growth factor-beta (TGF-beta) is differentially controlled both in vivo and in vitro. Characterization of the molecular mechanisms governing expression of TGF-beta isoforms now provides a basis for understanding the selective regulation of expression of the TGF-beta s by a variety of factors including oncogenes and tumor suppressor genes. In addition to transcriptional control, data suggest that expression of TGF-beta s is also regulated posttranscriptionally. Regulation of TGF-beta s by steroids and retinoids appears to involve predominantly posttranscriptional mechanisms. Identification of these mechanisms may contribute to the understanding of the regulatory events controlling cellular proliferation and differentiation by TGF-beta s and steroids/retinoids.

Animals↗
PubMed1994

A disposable fiberoptic arthroscope: a cadaver study.

Nine fresh cadaver ankle joints underwent arthroscopy to determine effectiveness of a small diameter, disposable, fiberoptic arthroscope. A sequential examination of the joint was performed through routine anteromedial and anterolateral portals. The anterior aspect of the joint with all anatomical structures was well visualized via the two anterior portals. The posterior aspect of the joint was also well visualized via anterior portals without distraction due to the flexibility of the scope and its small diameter. The quality of the visualization of the posterior joint from the anterior portals alone was comparable to that from the posterior approach. The results of this study indicate that diagnostic arthroscopy of the ankle joint with this disposable 1.6-mm arthroscope is comparable to the standard 2.7-mm to 5-mm arthroscopes. The size, flexibility, and 30 degrees viewing angle of this scope allow excellent and thorough joint visualization by routine anterior portals and minimize the need for joint distractors and posterior portals during routine diagnostic ankle arthroscopy.

Ankle Joint↗
PubMed1994

A simple method for predicting the cyclosporin A erythrocyte-to-plasma distribution ratio in blood, and its clinical assessment.

To adapt the monitoring of cyclosporin A (CyA) to clinical practice, we have developed a model to predict the CyA erythrocyte-to-plasma distribution ratio (CyA-EP), and evaluated its utility in clinical practice. We monitored CyA trough concentrations in whole blood and performed a series of biochemical tests during disease states in patients undergoing immunosuppressive therapy with CyA after transplantation. An estimate of CyA-EP (EPpr) was thus given by the following equation: EPpr = 6.0831 - 0.2944 x (TG+CHO) - 0.0037 x (CyAblood) - 0.0553 x (HCT) + 0.0463 x (BW) + 0.4447 x (CRE) - 0.0366 x (AGE). In this predictive model, EPpr is given as a function of the plasma lipid levels (TG+CHO, mM), the CyA concentration in whole blood (CyAblood, ng/ml), and the hematocrit (HCT, %), as well as the patient's body weight (BW, kg), serum creatinine (CRE, mg/dl) and age (AGE, years). The parameters TG+CHO, CyAblood, HCT, and AGE were negatively correlated with the CyA-EP, whereas BW and CRE exhibited a positive correlation. The predictive performance of this model was satisfactory for clinical use and changes in CyA-EP in transplant patients were obtained from monitoring CyA in whole blood and routine biochemical tests, without directly measuring CyA-EP. Since CyA-EP is an useful indicator for predicting a shift of CyA into tissues and its systemic clearance in plasma, our model to predict the CyA-EP will help the physician select a CyA regimen during immunosuppressive therapy in a variety of disease states after transplantation.

Adult↗
PubMed1994

Significance of Langerhans' cells in middle ear cholesteatoma.

Recent advances in immunology have opened a new approach to investigating the etiology and pathogenesis of aural cholesteatoma by the immunohistochemical technique. Immunohistochemical and submicroscopic analysis of human cholesteatoma matrices revealed the presence of Langerhans' cells. Several reports have suggested that Langerhans' cells in cholesteatoma are significant, and that the pathogenesis of this disease including bone resorption could be explained as a cell-mediated immune response, but this is still controversial. In this study, Langerhans' cells in cholesteatoma were quantitated and compared with those in postauricular skin and in skin of the open mastoidectomized cavity. The results did not support the hypothesis that Langerhans' cells have a primary role in the development of aural cholesteatoma.

Cholesteatoma, Middle Ear↗
PubMed1994

Treatment with cytosine arabinoside and granulocyte colony-stimulating factor in patients with myelodysplastic syndrome and its leukemic phase.

Twenty-one patients with myelodysplastic syndrome (MDS) or overt leukemia resulting from MDS were treated with recombinant human granulocyte colony-stimulating factor (rhG-CSF) and cytosine arabinoside (Ara-C). Ara-C was administered in a dose of 20 mg/m2 every 12 h for 5 days and after 2 days 125 micrograms of rhG-CSF was administered for 10 days. After recovery of the leukocyte count the therapy was repeated, doubling the dose of Ara-C serially when possible. Of 13 patients with MDS, four achieved complete remission (CR), two good response (GR), two minor response (MR), and five no response (NR). Of eight patients with overt leukemia from MDS, only one with hyperplastic bone marrow achieved a partial response (PR) and the remaining seven achieved NR. The efficacy of the combination of rhG-CSF and Ara-C in the treatment of MDS and its leukemic phase is discussed, including at which time rhG-CSF should be administered: before, after or concomitantly with Ara-C. Multicenter randomized studies are needed in the evaluation of this combination therapy.

Adult↗
PubMed1994

Intracellular pH modulates ion channel activity in lacrimal gland acinar cells.

The effects of intracellular pH on ion channel activity in lacrimal gland acinar cells were examined. The activity of Ca(2+)-activated K+ channels was studied in inside-out patches with bath pH at 7.8 and 6.8 (Ca2+ was buffered at 100 nM with EGTA). Elevating the bath pH to 7.8 increased channel open probability at each potential examined. The conductance of the channels was not affected by pH. The effects of pH on both K+ and Cl- channels were further investigated in whole-cell experiments. Increasing pH from 6.8 to 7.8 caused an increase in the current observed at hyperpolarising and depolarising potentials. The increase in outward currents at depolarising potentials was due to the increased activity of both K+ and Cl- channels. The activation of Cl- channels probably accounted for the increase in inward current at hyperpolarising potentials. This hypothesis was tested by examining whole-cell Cl- currents in the absence of permeant cations (i.e. K+ and Na+ replaced by N-methyl-D-glucamine). Under these conditions an increase in both inward and outward Cl- current was observed at pH 7.8. These data suggest that increasing intracellular pH increases the activity of Ca(2+)-activated K+ channels and Ca(2+)-activated Cl- channels.

Animals↗
PubMed1994

Evaluation of an orally administered vaccine, using hydrogels containing bacterial exotoxins of Pasteurella haemolytica, in cattle.

Poly(methacrylic acid) hydrogels were tested for oral delivery of a vaccine against Pasteurella haemolytica infection in cattle. Culture supernatants of P haemolytica, the most common bacterium associated with pneumonia in cattle, were used as the antigens in the vaccine. Hydrogels containing culture supernatants were administered orally to calves. Calves were then challenge-exposed with virulent P haemolytica. Calves were euthanatized 3 days after challenge exposure. The lungs of each calf were scored for severity and size of pneumonic lesions. Results indicated that vaccinated calves had smaller, less severe pneumonic lesions and lived longer than nonvaccinated calves. These results indicated that hydrogels can be used to deliver vaccines orally to calves to enhance resistance to pneumonia caused by P haemolytica.

Administration, Oral↗