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John Kim

Publications and source records attributed to John Kim.

47 records · Page 3Linked to original sources
PubMed2003

Resistance to DNA-damaging agents is discordant from experimental metastatic capacity in MEF ras-transformants-expressing gain of function MTp53.

Tumor cells can acquire aggressive phenotypes secondary to the loss of expression of the wild-type p53 (WTp53) protein or by the gain of function for selected mutant p53 (MTp53) proteins. However, it is unclear as to whether the development of aggressive phenotypes is inter-related. Herein we report the radiosensitivity, chemosensitivity, and in vivo growth characteristics of isogenic p53(-/-) MEF ras-transformants that variably express an MTp53 protein. Initial experiments revealed significant clonal heterogeneity with respect to cellular sensitivity to DNA-damaging agents (i.e. ionizing radiation, ultraviolet radiation, cis-platinum, and methotrexate) within subclones of a pre-existing p53(-/-) MEF cell population. Moreover, this differential sensitivity was also observed within subclones of p53(-/-) MEF cells transformed with an activated ras allele, suggesting that secondary genetic events and clonal selection, but not cellular transformation per se, may drive the resistance patterns for certain null-p53 tumors. In contrast, uniform resistance was observed following the additional transfection of an MTp53 allele (MTp53pro193) into p53(-/-) MEF transformants and p53(-/-) DP-16 Friend erythroleukemia cells, consistent with a gain of MTp53 function for this allele. Relative tumor growth rate and experimental metastatic ability was not enhanced by MTp53pro193 expression. Our results support the concept that gain of MTp53pro193 function leads to the selection of dominant clones, which may exhibit cellular resistance following cancer therapy.

Animals↗
PubMed2003

Goal-directed abdominal ultrasonography: impact on real-time decision making in the emergency department.

The impact of "goal-directed" abdominal ultrasound (US) on real-time decision making in the emergency department (ED) was studied, with specific emphasis on the certainty of diagnosis, treatment, and disposition plans. A prospective, interventional study enrolled 212 patients at a county teaching hospital ED, who underwent bedside US by experienced ED sonographers. A study questionnaire was completed documenting the US indication, working diagnosis, treatment, and disposition plan. The physicians assigned pre-test and post-test levels of certainty for the diagnosis, treatment plan, and disposition on an integral scale from 1 to 10. Scores for diagnosis were further categorized into low (1-3), moderate (4-7) and high certainty of disease. Absolute mean changes in level of certainty for diagnosis, treatment, and disposition were 3.2 (95% CI 3.1-3.3), 2.0 (95% CI 1.9-2.1), and 1.9 (95% CI 1.8-2.0), respectively. The direction of change after US for certainty of diagnosis was evenly split, with 47% increasing and 47% decreasing. The majority of patients categorized as either high or low certainty of disease had US results concordant with the physician's initial assessment. However, 16% moved from either high to low or from low to high certainty categories after US. Patients with moderate certainty moved evenly to either the low or high post-test category in 97% of cases. Treatment and disposition decisions were less impacted by US, with the majority of cases increasing in certainty irrespective of the US results. Bedside ultrasonography in the ED has an important impact on real-time decision-making, particularly in terms of the certainty of diagnosis.

Abdominal Injuries↗
PubMed2003

Computational and experimental identification of C. elegans microRNAs.

MicroRNAs (miRNAs) constitute an extensive class of noncoding RNAs that are thought to regulate the expression of target genes via complementary base-pair interactions. To date, cloning has identified over 200 miRNAs from diverse eukaryotic organisms. Despite their success, such biochemical approaches are skewed toward identifying abundant miRNAs, unlike genome-wide, sequence-based computational predictions. We developed informatic methods to predict miRNAs in the C. elegans genome using sequence conservation and structural similarity to known miRNAs and generated 214 candidates. We confirmed the expression of four new miRNAs by Northern blotting and used a more sensitive PCR approach to verify the expression of ten additional candidates. Based on hypotheses underlying our computational methods, we estimate that the C. elegans genome may encode between 140 and 300 miRNAs and potentially many more.

Algorithms↗
PubMed2003

A comparison of risk perception and psychological morbidity in women with ductal carcinoma in situ and early invasive breast cancer.

PURPOSE: To assess how women with ductal carcinoma in situ (DCIS) perceive their risks of recurrence, dying from breast cancer, and psychological distress compared to women with early stage invasive breast cancer (EIBC). PATIENTS AND METHODS: Eligible patients included those with DCIS or EIBC (T1 or T2, N0) referred to one cancer center between November 1998 and June 1999. Participants completed a self-administered survey regarding their views of their risks of developing recurrent cancer, of dying of breast cancer and the presence of psychological symptoms of distress. Responses were scored and compared between the two groups. RESULTS: In total, 495 patients were screened, 240 found ineligible, 228 patients who agreed to participate. No significant difference between the two groups was observed in perceptions of risk related to the likelihood of developing local recurrence (DCIS: 53%, EIBC 45%, P = 0.14), distant recurrence (DCIS: 36%; EIBC: 39%, P = 0.35) or dying of breast cancer (DCIS: 27%, EIBC 27%, P = 0.5). Both groups expressed similar levels of psychological distress (anxiety, DCIS: 56%, EIBC 54%, P = 0.38; depression, DCIS: 41%, EIBC, 48%, P = 0.17). CONCLUSIONS: Despite the excellent prognosis, women with DCIS express serious concerns and report similar psychological morbidity as women with invasive cancer.

Adult↗
PubMed2002

A Phase III placebo-controlled trial of oral pilocarpine in patients undergoing radiotherapy for head-and-neck cancer.

PURPOSE: To test the hypothesis that the use of oral pilocarpine during and after radiotherapy (RT) for head-and-neck cancer would reduce the symptoms of post-RT xerostomia. METHODS AND MATERIALS: One hundred thirty patients were randomized in a double-blind method to receive either pilocarpine (5-mg tablets) or placebo three times daily starting on Day 1 of RT and continuing for 1 month after treatment. The eligibility criteria included a planned dose of >50 Gy as radical or postoperative RT for head-and-neck cancer, with at least 50% of both parotid glands included in the treatment fields. The primary outcome measure was the severity of xerostomia as assessed by a patient-completed linear analog scale 3 months after RT. Secondary outcome measures included quality of life during therapy (as assessed by the McMaster University Head-and-Neck Questionnaire) and severity of mucositis during RT (as assessed using Radiation Therapy Oncology Group scales). RESULTS: No difference was observed between the pilocarpine-treated patients and the placebo group in the severity of xerostomia score as assessed by linear analog scale at baseline and 1, 3, and 6 months after treatment (repeated measures analysis, p = 0.92). No difference was apparent in the severity of mucositis during RT; 56.3% of patients receiving pilocarpine had Grade III/IV mucositis compared with 50.8% treated with placebo. No difference in quality of life was noted between the treatment groups during or after RT. The questionnaire score at 3 months after RT was 5.0 (SD 1.0). in the pilocarpine group and 4.9 (SD 0.9) in the placebo group. CONCLUSION: We were unable to detect a beneficial effect of pilocarpine on RT-induced xerostomia when administered during RT for head-and-neck cancer.

Administration, Oral↗
PubMed2002

Stat2 binding to the interferon-alpha receptor 2 subunit is not required for interferon-alpha signaling.

The interferon-alpha (IFNalpha) receptor consists of two subunits, the IFNalpha receptor 1 (IFNaR1) and 2 (IFNaR2) chains. Following ligand binding, IFNaR1 is phosphorylated on tyrosine 466, and this site recruits Stat2 via its SH2 domain. In contrast, IFNaR2 binds Stat2 constitutively. In this study we have characterized the Stat2-IFNaR2 interaction and examined its role in IFNalpha signaling. Stat2 binds the major IFNaR2 protein but not a variant containing a shorter cytoplasmic domain. The interaction does not require a STAT SH2 domain. Both tyrosine-phosphorylated and non-phosphorylated Stat2 bind IFNaR2 in vitro; however, relatively little phosphorylated Stat2 associates with IFNaR2 in vivo. In vitro binding assays defined IFNaR2 residues 418-444 as the minimal interaction domain and site-specific mutation of conserved acidic residues within this domain disrupted in vitro and in vivo binding. An IFNaR2 construct carrying these mutations was either (i) overexpressed in 293T cells or (ii) used to complement IFNaR2-deficient U5A cells. Unexpectedly, the activity of an IFNalpha-dependent reporter gene was not reduced but, instead, was enhanced up to 2-fold. This suggests that this particular IFNaR2-Stat2 interaction is not required for IFNalpha signaling, but might act to negatively inhibit signaling. Finally, a doubly truncated recombinant fragment of Stat2, spanning residues 136-702, associated with IFNaR2 in vitro, indicating that the interaction with IFNaR2 is direct and occurs in a central region of Stat2 marked by a hydrophobic core.

Amino Acid Sequence↗
PubMed2002

Metabolism of a new neuroprotective agent for ischemia-reperfusion damage, KR-31543 in the rat using liquid chromatography/electrospray mass spectrometry.

KR-31543, (2S,3R,4S)-6-amino-4-[N-(4-chlorophenyl)-N-(2-methyl-2H-tetrazol-5-ylmethyl)amino]-3,4-dihydro-2-dimethoxymethyl-3-hydroxy-2-methyl-2H-1-benzopyran is a new neuroprotective agent for ischemia-reperfusion damage. The in vitro and in vivo metabolism of KR-31543 in rats has been studied by LC-electrospray mass spectrometry. Rat liver microsomal incubation of KR-31543 in the presence of NADPH resulted in the formation of a metabolite M1. M1 was identified as N-(4-chlorophenyl)-N-(2-methyl-2H-tetrazol-5-ylmethyl)amine on the basis of LC-MS/MS analysis with the synthesized authentic standard. Rat CYP3A1 and 3A2 are the major CYP isozymes involved in the formation of M1.

Animals↗
PubMed2002

Effects of acute moderate hypoxemia on kinetics of metoclopramide and its metabolites in chronically instrumented sheep.

Hypoxemia is known to induce various physiological changes which can result in alteration in drug pharmacokinetics. To examine the effect of acute moderate hypoxemia on metoclopramide (MCP) pharmacokinetics, a continuous 14-hour infusion of MCP during a normoxemic, hypoxemic and subsequent normoxemic period was conducted in eight adult sheep. Arterial blood and urine samples were collected to examine the effects on the pharmacokinetics of MCP and its deethylated metabolites. MCP and its mono- and di-deethylated metabolites were quantitated using a GC/MS method. Steady-state concentrations of MCP were achieved in each of the three periods. During hypoxemia, MCP plasma steady-state concentration increased significantly from 50.72 +/- 1.06 to 63.62 +/- 1.79 ng/mL, and later decreased to 55.83 +/- 1.15 ng/mL during the post-hypoxemic recovery period. Total body clearance (CL(TB)) of MCP was significantly decreased from 274.2 +/- 48.0 L/h to 205.40 +/- 28.2 L/h during hypoxemia, and later restored to 245.8 +/- 44.2 L/h during the post-hypoxemic period. Plasma mono-deethylated MCP concentration (32.78 +/- 1.73 ng/mL) also increased, compared to the control group (21.20 +/- 1.39 ng/mL), during hypoxemia and subsequent normoxemic period. Renal excretion of MCP and its metabolites was also decreased during hypoxemia, while urine flow was increased with a concomitant decrease in urine osmolality. Thus, the results indicate that acute moderate hypoxemia affects MCP pharmacokinetics.

Acute Disease↗
PubMed2001

Convergence of multiple autophagy and cytoplasm to vacuole targeting components to a perivacuolar membrane compartment prior to de novo vesicle formation.

Under starvation conditions, the majority of intracellular degradation occurs at the lysosome or vacuole by the autophagy pathway. The cytoplasmic substrates destined for degradation are packaged inside unique double-membrane transport vesicles called autophagosomes and are targeted to the lysosome/vacuole for subsequent breakdown and recycling. Genetic analyses of yeast autophagy mutants, apg and aut, have begun to identify the molecular machinery as well as indicate a substantial overlap with the biosynthetic cytoplasm to vacuole targeting (Cvt) pathway. Transport vesicle formation is a key regulatory step of both pathways. In this study, we characterize the putative compartment from which both autophagosomes and the analogous Cvt vesicles may originate. Microscopy analyses identified a perivacuolar membrane as the resident compartment for both the Apg1-Cvt9 signaling complex, which mediates the switching between autophagic and Cvt transport, and the autophagy/Cvt-specific phosphatidylinositol 3-kinase complex. Furthermore, the perivacuolar compartment designates the initial site of membrane binding by the Apg/Cvt vesicle component Aut7, the Cvt cargo receptor Cvt19, and the Apg conjugation machinery, which functions in the de novo formation of vesicles. Biochemical isolation of the vesicle component Aut7 and density gradient analyses recapitulate the microscopy findings although also supporting the paradigm that components required for vesicle formation and packaging concentrate at subdomains within the donor membrane compartment.

Autophagy-Related Protein 7↗
PubMedDate not supplied

Gabapentin for overactive bladder and nocturia after anticholinergic failure.

INTRODUCTION: We reviewed our experience with the use of gabapentin to treat symptoms of overactive bladder (OAB) and nocturia in patients who have failed conventional anticholinergic therapy. METHODS: Thirty-one patients referred to us with refractory (OAB) and/or nocturia were treated with oral gabapentin. All the patients had tried or remained on antimuscarinic drugs during treatment. Twenty-four of 31 complained of bothersome symptoms during day and night and the other seven had primary complaints of nocturia. Initial gabapentin doses ranged from 100-300 mg at bedtime. Dose was slowly titrated up to 3,000 mg based on patients' symptomatology and tolerability. RESULTS: The mean age was 51 years old (range 27-78). There were 13 men and 18 women. The median steady state dose chosen by the patient after initial titration was 600 mg/day. Fourteen of 31 patients reported subjective improvement of their frequency and 8 have been on the medication for over 12 months with persistent efficacy. For the 14 improved patients, mean frequency/24 hours decreased from 14.1 +/- 2.2 to 10.0 +/- 2.1. Three patients with primary nocturia reported improvement from a mean of 4.0 +/- 1.3 to 1.0 +/- 0.3 episodes/night. Six patients stopped taking the drug within one month due to side effects mostly described as drowsiness or lethargy. CONCLUSIONS: Fourteen of 31 patients with refractory (OAB) and nocturia improved with oral gabapentin. Gabapentin was generally well tolerated and can be considered in selective patients when conventional modalities have failed.

Adult↗