Biomedical subjects

J H Lee

Publications and source records attributed to J H Lee.

At least 19 recordsLinked to original sources

PubMed1999

Inhibition of poly(ADP-ribose)polymerase binding to DNA by thymidine dimer.

The ability of poly(ADP-ribose)polymerase to bind damaged DNA was assessed by electrophoretic mobility shift assay. DNA binding domain of poly(ADP-ribose)polymerase (PARPDBD) binds to synthetic deoxyribonucleotide duplex 10-mer. However, the synthetic deoxyribonucleotide duplex containing cys-syn thymidine dimer which produces the unwinding of DNA helix structure lost its affinity to PARPDBD. It was shown that the binding of PARPDBD to the synthetic deoxyribonucleotide duplex was not affected by O6-Me-dG which causes only minor distortion of DNA helix structure. This study suggests that the stabilized DNA helix structure is important for poly(ADP-ribose)polymerase binding to DNA breaks, which are known to stimulate catalytic activity of poly(ADP-ribose)polymerase.

DNA↗

PubMed1999

Universal conservation in translation initiation revealed by human and archaeal homologs of bacterial translation initiation factor IF2.

Binding of initiator methionyl-tRNA to ribosomes is catalyzed in prokaryotes by initiation factor (IF) IF2 and in eukaryotes by eIF2. The discovery of both IF2 and eIF2 homologs in yeast and archaea suggested that these microbes possess an evolutionarily intermediate protein synthesis apparatus. We describe the identification of a human IF2 homolog, and we demonstrate by using in vivo and in vitro assays that human IF2 functions as a translation factor. In addition, we show that archaea IF2 can substitute for its yeast homolog both in vivo and in vitro. We propose a universally conserved function for IF2 in facilitating the proper binding of initiator methionyl-tRNA to the ribosomal P site.

Amino Acid Sequence↗

PubMed1999

Effects of kerosene cleaning on the formation of DNA adducts in the skin and lung tissues of mice dermally exposed to used gasoline engine oil.

Used gasoline engine oils (UGEO) are carcinogenic and/or mutagenic in long-term studies and capable of increasing the number of mutagen- or carcinogen-DNA adducts when applied dermally to mice. The carcinogenic or mutagenic risk of UGEO has been attributed to the concentration of polycyclic aromatic compounds (PAC) that accumulate in the lubricating system during combustion of gasoline. When dermal exposure to UGEO takes place, the use of hand cleansers, solvent- or d-limonene-based, is commonly recommended for washing, In this study, female mice aged 4-6 wk (12-17 g) were utilized to evaluate the efficiency of kerosene, as solvent-based cleanser, to remove UGEO following dermal exposure. Using a 32P postlabeling technique, the total levels of DNA adducts in skin and lung were significantly increased in kerosene-treated mice. Application of UGEO followed by kerosene washing significantly decreased skin DNA adduct levels but increased lung adduct levels after 8 h. The observed lower DNA adduct skin levels may reflect greater UGEO skin penetration and absorption in the presence of kerosene cleanser.

Administration, Topical↗

PubMed1999

Differential distribution of three members of a gene family encoding low voltage-activated (T-type) calcium channels.

Low voltage-activated (T-type) calcium currents are observed in many central and peripheral neurons and display distinct physiological and functional properties. Using in situ hybridization, we have localized central and peripheral nervous system expression of three transcripts (alpha1G, alpha1H, and alpha1I) of the T-type calcium channel family (CaVT). Each mRNA demonstrated a unique distribution, and expression of the three genes was largely complementary. We found high levels of expression of these transcripts in regions associated with prominent T-type currents, including inferior olivary and thalamic relay neurons (which expressed alpha1G), sensory ganglia, pituitary, and dentate gyrus granule neurons (alpha1H), and thalamic reticular neurons (alpha1I and alpha1H). Other regions of high expression included the Purkinje cell layer of the cerebellum, the bed nucleus of the stria terminalis, the claustrum (alpha1G), the olfactory tubercles (alpha1H and alpha1I), and the subthalamic nucleus (alpha1I and alpha1G). Some neurons expressed high levels of all three genes, including hippocampal pyramidal neurons and olfactory granule cells. Many brain regions showed a predominance of labeling for alpha1G, including the amygdala, cerebral cortex, rostral hypothalamus, brainstem, and spinal cord. Exceptions included the basal ganglia, which showed more prominent labeling for alpha1H and alpha1I, and the olfactory bulb, the hippocampus, and the caudal hypothalamus, which showed more even levels of all three transcripts. Our results are consistent with the hypothesis that differential gene expression underlies pharmacological and physiological heterogeneity observed in neuronal T-type calcium currents, and they provide a molecular basis for the study of T-type channels in particular neurons.

Animals↗

PubMed1999

Cloning and expression of a novel member of the low voltage-activated T-type calcium channel family.

Low voltage-activated Ca2+ channels play important roles in pacing neuronal firing and producing network oscillations, such as those that occur during sleep and epilepsy. Here we describe the cloning and expression of the third member of the T-type family, alpha1I or CavT.3, from rat brain. Northern analysis indicated that it is predominantly expressed in brain. Expression of the cloned channel in either Xenopus oocytes or stably transfected human embryonic kidney-293 cells revealed novel gating properties. We compared these electrophysiological properties to those of the cloned T-type channels alpha1G and alpha1H and to the high voltage-activated channels formed by alpha1Ebeta3. The alpha1I channels opened after small depolarizations of the membrane similar to alpha1G and alpha1H but at more depolarized potentials. The kinetics of activation and inactivation were dramatically slower, which allows the channel to act as a Ca2+ injector. In oocytes, the kinetics were even slower, suggesting that components of the expression system modulate its gating properties. Steady-state inactivation occurred at higher potentials than any of the other T channels, endowing the channel with a substantial window current. The alpha1I channel could still be classified as T-type by virtue of its criss-crossing kinetics, its slow deactivation (tail current), and its small (11 pS) conductance in 110 mM Ba2+ solutions. Based on its brain distribution and novel gating properties, we suggest that alpha1I plays important roles in determining the electroresponsiveness of neurons, and hence, may be a novel drug target.

Amino Acid Sequence↗

PubMed1999

Delivery of an adenovirus vector in a calcium phosphate coprecipitate enhances the therapeutic index of gene transfer to airway epithelia.

Gene transfer could provide a novel treatment for cystic fibrosis. However, current vectors, including recombinant adenoviruses, are relatively inefficient at gene transfer to airway epithelia. We have found that delivering adenovirus in a calcium phosphate coprecipitate (Ad:CaPi coprecipitates) enhanced the efficiency of gene transfer to airway epithelia in vitro and in vivo. However, the potential for injury to the epithelium was not evaluated. In NIH 3T3 cells treated with Ad:CaPi coprecipitates, we found that a 30-min exposure, which was sufficient for maximal transgene expression, produced no toxicity; whereas some other transfection reagents induced significant toxicity. Moreover, when Ad:CaPi coprecipitates were applied to the apical surface of differentiated airway epithelia in vitro, they did not reduce transepithelial resistance, even after prolonged incubation. Delivery of Ad:CaPi coprecipitates to mouse lung induced an inflammatory response, but it was not substantially different from that following administration of adenovirus alone. Thus, Ad:CaPi coprecipitates significantly enhance gene transfer to differentiated human airway epithelia in vitro and to mouse lung in vivo without increasing toxicity or the inflammatory response. Thus, CaPi coprecipitates may enhance the therapeutic index of adenovirus-based gene transfer vectors.

3T3 Cells↗

PubMed1999

Cloning of a novel four repeat protein related to voltage-gated sodium and calcium channels.

Cloning has led to the discovery of more ion channels than predicted by functional studies, yet there remain channels that have not been cloned. We report the cloning of a novel protein that contains the four domain structure found in voltage-gated Ca2+ and Na+ channels. Phylogenetic relationships suggested that the protein might have diverged from an ancestral four repeat channel before the divergence of Ca2+ and Na+ channels. Northern blot analysis showed that mRNA transcripts encoding the protein are expressed predominantly in the brain, moderately in the heart, and weakly in the pancreas. Despite extensive expression attempts, currents from the putative channel were not detected. Based on its sequence, we propose that the novel protein might be a voltage-activated cation channel with unique gating properties.

Amino Acid Sequence↗

PubMed1999

Solution structure of a sweet protein single-chain monellin determined by nuclear magnetic resonance and dynamical simulated annealing calculations.

Single-chain monellin (SCM), which is an engineered 94-residue polypeptide, has proven to be as sweet as native two-chain monellin. SCM is more stable than the native monellin for both heat and acidic environments. Data from gel filtration HPLC and NMR indicate that the SCM exists as a monomer in aqueous solution. The solution structure of SCM has been determined by nuclear magnetic resonance (NMR) spectroscopy and dynamical simulated annealing calculations. A stable alpha-helix spanning residues Phe11-Ile26 and an antiparallel beta-sheet formed by residues 2-5, 36-38, 41-47, 54-64, 69-75, and 83-88 have been identified. The sheet was well defined by backbone-backbone NOEs, and the corresponding beta-strands were further confirmed by hydrogen bond networks based on amide hydrogen exchange data. Strands beta2 and beta3 are connected by a small bulge comprising residues Ile38-Cys41. A total of 993 distance and 56 dihedral angle restraints were used for simulated annealing calculations. The final simulated annealing structures ( k) converged well with a root-mean-square deviation (rmsd) between backbone atoms of 0.49 A for secondary structural regions and 0.70 A for backbone atoms excluding two loop regions. The average restraint energy-minimized (REM) structure exhibited root-mean-square deviations of 1.19 A for backbone atoms and 0.85 A for backbone atoms excluding two loop regions with respect to 20 k structures. The solution structure of SCM revealed that the long alpha-helix was folded into the concave side of a six-stranded antiparallel beta-sheet. The side chains of Tyr63 and Asp66 which are common to all sweet peptides showed an opposite orientation relative to H1 helix, and they were all solvent-exposed. Residues at the proposed dimeric interface in the X-ray structure were observed to be mostly solvent-exposed and demonstrated high degrees of flexibility.

Algorithms↗

PubMed1999

C-terminal fragment of Alzheimer's amyloid precursor protein inhibits sodium/calcium exchanger activity in SK-N-SH cell.

Numerous lines of evidence suggest that some of the neurotoxicity associated with Alzheimer's disease (AD) is due to proteolytic fragments of the amyloid precursor protein (APP). Most research has focused on the amyloid beta peptide (Abeta). However, the possible role of other cleaved products of APP is less clear. We have previously shown that a recombinant carboxy-terminal 105 amino acid fragment (CT 105) of APP induced strong non-selective inward currents and also showed neurotoxicity in PC 12 cells and primary cortical neurons and blocked later phase of long term potentiation (LTP) in rat hippocampus in vivo. In this study, we investigated the effects of CT 105 on Na+-Ca2+ exchanger activity in SK-N-SH human neuroblastoma, in the presence of ouabain and monensin, which are considered to drive Na+-Ca2+ exchanger in the reverse mode. CT 105 inhibited the activity of this exchanger in SK-N-SH cells by approximately 50%.

Amyloid beta-Protein Precursor↗

PubMed1999

Trunk muscle weakness as a risk factor for low back pain. A 5-year prospective study.

STUDY DESIGN: A 5-year prospective study. OBJECTIVES: To investigate trunk muscle weakness as a risk factor for low back pain in asymptomatic volunteers. SUMMARY OF BACKGROUND DATA: Muscle strength has not been sufficiently studied as a risk factor for low back pain. METHODS: The study participants included 30 male and 37 female volunteers (mean age, 17 +/- 2 years), who neither reported nor had ever been treated for low back pain. Trunk muscle strength was measured isokinetically (60 degrees/sec), using the trunk extension and flexion and torso rotation units. The peak torques of the volunteers' extension, flexion, rightward rotation, and leftward rotation were measured, and the agonist/antagonist ratios were calculated as extension/flexion and left rotation/right rotation ratio. The volunteers then were followed prospectively for 5 years to determine the incidence of low back pain and were classified into a non-low back pain group (volunteers with no low back pain during the 5-year follow-up period) and a low back pain group (volunteers who experienced low back pain during this period). RESULTS: The low back pain group consisted of 8 male and 10 female volunteers. There were no significant differences between the non-low back pain group and the low back pain group regarding age, height, weight, the peak torque values, or the left rotation/right rotation ratio. However, the extension/flexion ratio of the low back pain group (men, 0.96 +/- 0.27; women, 0.77 +/- 0.19) demonstrated significantly lower values than that of the non-low back pain group (1.23 +/- 0.28 and 1.00 +/- 0.16 for men and women, respectively, P < 0.05). CONCLUSIONS: An imbalance in trunk muscle strength, i.e., lower extensor muscle strength than flexor muscle strength, might be one risk factor for low back pain.

Adolescent↗

PubMed1999

Clinical and economic impact of a combination Haemophilus influenzae and Hepatitis B vaccine: estimating cost-effectiveness using decision analysis.

BACKGROUND: Compliance with hepatitis B virus (HBV) vaccine remains suboptimal, despite a recommendation by the Advisory Committee on Immunization Practices of the US Public Health Service that all newborns be vaccinated. Although a combined HBV-Haemophilus influenzae type b (Hib) vaccine may improve acceptance of the HBV vaccine, the clinical and economic consequences of this intervention are uncertain. OBJECTIVES: To compare the health impact and cost-effectiveness of the following 2 immunization strategies: current practice of administering HBV vaccine separately (75% compliance) and Hib vaccine alone or as part of a multivalent vaccine (95% compliance); and strategy of delivering a combined HBV-Hib vaccine (95% compliance). DESIGN: A Markov model simulated the natural history of acute and chronic HBV and Hib disease in a cohort of US newborns. Clinical and economic variables were obtained from published reports. RESULTS: The Hib-related outcomes were the same in both strategies, because the efficacy and compliance with Hib vaccine were assumed to be equivalent in both. A 53% reduction in the number of cases of HBV infection with the combination strategy (n = 8541) was estimated when compared with current practice (n = 18 044), along with 205 fewer HBV-related deaths per 1 million infants. Immunization costs of the combination strategy were $11.5 million higher than for current practice ($108.4 million compared with $96.9 million), whereas the cost of HBV-related disease was $4.0 million lower than in current practice. The incremental cost-effectiveness ratio for the combination strategy was $17700 per year of life saved. CONCLUSION: An HBV-Hib vaccine in US infants yields substantial benefits, with a cost-effectiveness ratio that is lower than that of many commonly used medical interventions.

Adolescent↗

PubMed1999

Using flow relaxography to elucidate flow relaxivity.

We have investigated the theoretical and experimental linear dependence of the reciprocal of the apparent longitudinal relaxation time [(T*1)-1] of the NMR signal from spins in a flowing fluid on the volume flow rate, Fv, the so-called inflow effect. We refer to the coefficient of this dependence as the longitudinal flow relaxivity, r1F. A very simple model predicts that, under a range of conditions pertinent to modern flow studies and perfusion imaging experiments, r1F is controlled by the volume of the fluid in which the magnetization is perturbed by pulsed RF inversion or saturation, not the detection volume, and that it can be approximated as the reciprocal of half of the inversion volume. Phantom sample experiments, using a new, quantitative approach that we call flow relaxography, confirm the general predictions of this simple model. There are two intriguing implications of these findings for general NMR flow studies as well as for medical applications. It should be possible to vary the value of r1F by simply (noninvasively) adjusting the inversion slice thickness, and thus measure the value of (blood 1H2O, for example) Fv in a vessel without changing Fv, from the resultant varying T*1 values. Also, it should be possible to extrapolate to the intrinsic T1 value of the fluid signal (as if it were stationary), without altering or stopping the flow. Again, these are quite successful in phantom sample studies. Imaging versions of the flow relaxographic experiments are also possible. The twin goals of flow studies in medical MRI are the quantitative discrimination of the signals from flowing and nonflowing spins, and the accurate measurement of the flow rate of the former.

Blood Flow Velocity↗

PubMed1999

Anterior cervical spinal epidural abscess in an infant.

Spinal epidural abscess (SEA) is rare in children, especially in newborns and infants, groups in which only very few cases have been reported. Because of the nonspecificity of presenting symptoms in children the diagnosis may be delayed, resulting in major permanent neurological deficits. In this paper, we report a case of cervical SEA in a 6-week-old infant who initially presented with fever and developed quadriparesis 19 days prior to admission. After emergency anterior decompression of the abscess the neurological function was improved immediately. Five months after surgery the neurological status was normal, an MR study showing disappearance of the epidural abscess and spinal cord indentation, and progressive fusion of the C3, C4 and C5 vertebral bodies. Anterior decompression without bone graft can provide an excellent prognosis in case of an anterior cervical SEA in infants.

Abscess↗

PubMed1999

The reversed SoxS-binding site upstream of the ribA promoter in Escherichia coli.

The ribA gene, encoding GTP cyclohydrolase II in Escherichia coli, is a member of the soxRS regulon, which is induced by superoxide-generating agents. By evaluating lacZ expression driven by the ribA promoter carrying different lengths of upstream region in a monolysogen, we found that the superoxide-responsive element resides between 56 and 94 nucleotides upstream of the transcriptional start site. Purified SoxS protein bound to this region and protected nucleotides between positions -80 and -58 from degradation by DNase I. This region contains a putative SoxS-binding sequence (soxbox) in reverse orientation. The SoxS protein interacted specifically with four guanine residues within the soxbox sequence, as demonstrated by methylation interference analysis. These results clearly indicate that SoxS binds to the reversed soxbox sequence in the ribA gene, while in other known genes of the soxRS regulon it binds to the normally oriented soxbox. Possible modes of interaction between SoxS and RNA polymerase are discussed.

Bacterial Proteins↗

PubMed1999

Antigenic and genetic variations of the 15 kD nucleocapsid protein of porcine reproductive and respiratory syndrome virus isolates.

The antigenic variability of the 15 kD nucleocapsid protein of porcine reproductive and respiratory syndrome (PRRS) virus was characterized with a panel of 24 monoclonal antibodies (MAbs) raised against the American PRRS virus isolate ISU-P. Five continuous epitopes designated EpORF7-A through E were revealed by the reactivity pattern of these MAbs with 67 American field isolates, two modified-live vaccine viruses, and the European Lelystad virus as determined by the indirect immnofluorescence assay and Western immunoblotting and confirmed by additivity and blocking enzyme-linked immunosorbent assays. The reactivity pattern of isolates in the IFA permitted their subdivision into 4 American antigenic groups which represented 84.1, 11.6, 2.9 and 1.4% of viruses tested. The antigenic variation among isolates was correlated to single, group specific nucleotide substitutions and mediated by a combination of at least 4 of the 5 epitopes. EpORF7-A was conserved in all American isolates and the Lelystad virus which constituted a separate antigenic group. Consequently, monoclonal antibodies specific for EpORF7-A may prove useful as the antigenic basis for a universal diagnostic test for the PRRS virus. EpORF7-C, D and E were only present in the American isolates tested.

Amino Acid Sequence↗

PubMed1999

Germline mutations of the APC gene in Korean familial adenomatous polyposis patients.

We extensively analyzed genomic DNA and messenger RNA (mRNA) from 62 unrelated Korean patients with familial adenomatous polyposis (FAP) for identification of germline adenomatous polyposis coli (APC) gene mutations. We adopted both single-strand conformation polymorphism (SSCP) analysis and a method of analysis involving the reverse transcription-polymerase chain reaction (RT-PCR) followed by a protein truncation test (PTT). DNA sequencing confirmed all alterations represented by aberrant bands. Germline mutations were identified in 38 patients (61%). Nineteen of the detected mutations were presumed to be novel, thus emphasizing the heterogeneity of the mutational spectrum in Korean FAP patients. In the initial 48 patients, SSCP analysis was followed by PTT for those patients for whom no detectable mutations were found by SSCP. Using this combined approach, we identified germline APC gene mutations in 29 of the 48 FAP patients (60%), including 6 patients in whom SSCP analysis failed to distinguish the mutant allele. In the 14 later patients, we identified truncating mutations in 9 patients (64%) using PTT only. Our results confirm that the mutation detection rate with PTT was superior to that with SSCP, and suggest that PTT would be a more practical screening method to detect germline mutations of the APC gene in FAP patients.

Adenomatous Polyposis Coli↗

PubMed1999

Macular hole surgery in conjunction with endolaser photocoagulation.

PURPOSE: To determine whether endolaser photocoagulation to the retinal pigment epithelium at the base of a macular hole increases the anatomic success rate of surgery. METHODS: In a prospective consecutive clinical trial, eight eyes of seven patients with idiopathic macular hole underwent vitrectomy with posterior cortical vitreous removal and peeling of visible epiretinal membrane when present. A single shot of argon endolaser photocoagulation was applied to the retinal pigment epithelium at the center of the macular hole with a duration of 0.05 to 0.2 seconds and an intensity of 50 to 200 mW. After fluid-gas exchange was performed with 14% perfluoropropane gas, patients maintained face-down positioning for 2 weeks. RESULTS: One eye with stage 2 macular hole, six eyes with stage 3 macular hole, and one eye with stage 4 macular hole were included. All eight eyes had a closed macular hole (100% anatomic success rate) at final examination 6 to 12 months after surgery. Best-corrected visual acuity improved 3 or more lines on the Early Treatment Diabetic Retinopathy Study visual acuity chart in all eyes. Four (50%) of the eight eyes had a final visual acuity of 20/40 or better. CONCLUSIONS: Endolaser photocoagulation may be a useful adjunct to macular hole surgery but requires further investigation and long-term evaluation.

Aged↗

PubMed1999

Cerebral metabolic abnormalities in congestive heart failure detected by proton magnetic resonance spectroscopy.

OBJECTIVES: Using proton magnetic resonance spectroscopy, we investigated cerebral metabolism and its determinants in congestive heart failure (CHF), and the effects of cardiac transplantation on these measurements. BACKGROUND: Few data are available about cerebral metabolism in CHF. METHODS: Fifty patients with CHF (ejection fraction < or = 35%) and 20 healthy volunteers were included for this study. Of the patients, 10 patients underwent heart transplantation. All subjects performed symptom-limited bicycle exercise test. Proton magnetic resonance spectroscopy (1H MRS) was obtained from localized regions (8 to 10 ml) of occipital gray matter (OGM) and parietal white matter (PWM). Absolute levels of the metabolites (N-acetylaspartate, creatine, choline, myo-inositol) were calculated. RESULTS: In PWM only creatine level was significantly lower in CHF than in control subjects, but in OGM all four metabolite levels were decreased in CHF. The creatine level was independently correlated with half-recovery time and duration of heart failure symptoms in PWM (r = -0.56, p < 0.05), and with peak oxygen consumption and serum sodium concentration in OGM (r = 0.58, p < 0.05). Cerebral metabolic abnormalities were improved after successful cardiac transplantation. CONCLUSIONS: This study shows that cerebral metabolism is abnormally deranged in advanced CHF and it may serve as a potential marker of the disease severity.

Adult↗