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Biomedical subjects

S B Hong

Publications and source records attributed to S B Hong.

At least 19 recordsLinked to original sources
PubMed2003

The effects of dual blockade of the renin-angiotensin system on urinary protein and transforming growth factor-beta excretion in 2 groups of patients with IgA and diabetic nephropathy.

AIMS: The therapeutic benefits of dual blockade of the renin-angiotensin system (RAS) have been inconsistent on renal function and proteinuria. To know the contribution of the heterogeneity of study subjects to such inconsistency, we evaluated the effects of dual blockade of RAS in 2 groups of selected renal diseases, IgA and diabetic nephropathy. To avoid confounding by the blood pressure-reducing effects, angiotensin II receptor antagonists (ATRAs) were added on the patients with long-term, optimally controlled blood pressure taking ACE inhibitors. Twenty-four-hour urinary protein excretion rate and urinary TGF-beta1 level were measured as surrogate markers of renal injury. METHODS: We conducted a prospective crossover trial with 14 IgA and 18 type-2-diabetic nephropathy patients showing moderate degree of proteinuria (> or = 1.0 g/day) and renal dysfunction (creatinine clearance 25 - 75/ml/min). Four to 8 mg once-daily dose of candesartan and placebo were alternatively added on ramipril dose of 5 - 7.5 mg/day for 16 weeks. RESULTS: All baseline data except for the age factor were statistically the same between the 2 disease groups. Twenty-four-hour mean arterial blood pressures were 91.2 +/- 1.6 and 92.3 +/- 1.8 mmHg in IgA and diabetic nephropathy patients respectively at baseline (p = NS). Mean arterial pressure did not change by the addition of candesartan or placebo in both groups. The addition of candesartan (combination) reduced 24-hour urinary protein excretion rate in IgA nephropathy patients with a mean change of -12.3 +/- 4.5%, which is significantly greater compared to a mean change of -0.1 +/- 3.3% after the addition of placebo (placebo) (mean difference 12.4 +/- 5.0, 95% CI 1.2 - 23.5; p < 0.05). Urinary TGF-beta1 level was reduced considerably by the combination therapy, with a -28.9 +/- 6.0% decrease, which was significantly different to that by the placebo, with +4.3 +/- 12.4% (33.3 +/- 13.5, 3.2 - 63.3; p < 0.05). In diabetic nephropathy patients, the addition of candesartan did not reduce 24-hour urinary protein excretion rate. Mean changes of 24-hour urinary protein excretion rate were -0.8 +/- 4.7% by the combination therapy and +0.5 +/- 6.1% by placebo (mean difference 1.3 +/- 4.7, 95% CI -6.8 - 13.5; p < NS). The level of urinary TGF-beta1 was reduced by the combination therapy, with -14.3 +/- 9.5% decrease, but it did not reach statistical significance compared to placebo of +0.7 +/- 15.5% (15.0 +/- 13.5, -14.4 - 44.5; p < NS). The changes in 24-hour urinary protein excretion rate and urinary TGF-beta1 level were neither correlated with each other, nor with the change in mean arterial pressure. Significant changes in the renal function were not detected during the study period. CONCLUSION: Definite beneficial effects of dual blockade of RAS on proteinuria and TGF-beta1 excretion were found in IgA nephropathy patients, which was independent of blood pressure-reducing effect. With our 16-week trial, such benefits were not observed in type 2 diabetic nephropathy. The reduction in urinary TGF-beta1 level suggests that the combination therapy may provide additional renoprotection through the antisclerosing effects. Based on our results, for a proper interpretation the therapeutic effects of the combination therapy should be evaluated separately according to the underlying renal disease.

Adult↗
PubMed2001

Pathogenic role of endothelin 1 in hemodynamic dysfunction in experimental acute pulmonary thromboembolism.

The plasma endothelin-1 (ET-1) level is elevated in patients with acute pulmonary thromboembolism (APE). Whether ET-1 is a pathogenic mediator or a simple marker of APE is not known. We investigated the role of ET-1 in hemodynamic dysfunction in APE through evaluating the effects of ET(A) receptor antagonist in an experimental APE model. We also examined ET-1 expression in embolized lungs. In a canine autologous blood clot pulmonary embolism model, ET(A) receptor antagonist ZD2574 (10 mg/kg, intravenous; ZD2574 group; n = 6) or vehicle (control group; n = 5) was administered. Hemodynamic and gas exchange parameters and plasma levels of ET-1 were serially measured. Prepro-ET-1 mRNA expression and the distribution of ET-1 peptide in lung tissues were also examined. With ZD2574 pulmonary arterial pressure and pulmonary vascular resistance significantly decreased, and were lower compared with the control group. The decrease in cardiac output was also less in the ZD2574 group. Plasma ET-1 levels increased after embolization. Prepro-ET-1 mRNA expression increased in embolized lungs and ET-1 peptide expression also increased in embolized lungs, particularly in the muscular pulmonary arteries, compared with normal lungs. These findings suggest that ET-1 partially contributes to hemodynamic derangements of APE, and that ET(A) receptor antagonists might constitute a useful therapeutic tool for APE.

Acute Disease↗
PubMed2001

Structural determinants of the substrate and stereochemical specificity of phosphotriesterase.

Bacterial phosphotriesterase (PTE) catalyzes the hydrolysis of a wide variety of organophosphate nerve agents and insecticides. Previous kinetic studies with a series of enantiomeric organophosphate triesters have shown that the wild type PTE generally prefers the S(P)-enantiomer over the corresponding R(P)-enantiomers by factors ranging from 1 to 90. The three-dimensional crystal structure of PTE with a bound substrate analogue has led to the identification of three hydrophobic binding pockets. To delineate the factors that govern the reactivity and stereoselectivity of PTE, the dimensions of these three subsites have been systematically altered by site-directed mutagenesis of Cys-59, Gly-60, Ser-61, Ile-106, Trp-131, Phe-132, His-254, His-257, Leu-271, Leu-303, Phe-306, Ser-308, Tyr-309, and Met-317. These studies have shown that substitution of Gly-60 with an alanine within the small subsite dramatically decreased k(cat) and k(cat)/K(a) for the R(P)-enantiomers, but had little influence on the kinetic constants for the S(P)-enantiomers of the chiral substrates. As a result, the chiral preference for the S(P)-enantiomers was greatly enhanced. For example, the value of k(cat)/K(a) with the mutant G60A for the S(P)-enantiomer of methyl phenyl p-nitrophenyl phosphate was 13000-fold greater than that for the corresponding R(P)-enantiomer. The mutation of I106, F132, or S308 to an alanine residue, which enlarges the small or leaving group subsites, caused a significant reduction in the enantiomeric preference for the S(P)-enantiomers, due to selective increases in the reaction rates for the R(P)-enantiomers. Enlargement of the large subsite by the construction of an H254A, H257A, L271A, or M317A mutant had a relatively small effect on k(cat)/K(a) for either the R(P)- or S(P)-enantiomers and thus had little effect on the overall stereoselectivity. These studies demonstrate that by modifying specific residues located within the active site of PTE, it is possible to dramatically alter the stereoselectivity and overall reactivity of the native enzyme toward chiral substrates.

Amino Acid Substitution↗
PubMed2001

A new Ti-5Ag alloy for customized prostheses by three-dimensional printing (3DP).

Three important considerations in the fabrication of customized cranio-maxillofacial prostheses are geometric precision, material strength, and biocompatibility. Three-dimensional printing (3DP) is a rapid part-fabrication process that can produce complex parts with high precision. The aim of this study was to design, synthesize by 3DP, and characterize a new Ti-5Ag (wt%) alloy. Silver nitrate was found to be an appropriate inorganic binder for the Ti powder-based skeleton, and the optimum sintering parameters for full densification were determined. The hardness of the Ti-5Ag alloy was shown to be much higher than that of a pure titanium sample. Potentiodynamic measurements, carried out in saline solution at body temperature, showed that the Ti-5Ag alloy had good passivation behavior, similar to that of pure titanium. It is concluded that the Ti-Ag system may be suitable for fabrication of customized prostheses by 3DP.

Alloys↗
PubMed2001

Ictal hyperperfusion of cerebellum and basal ganglia in temporal lobe epilepsy: SPECT subtraction with MRI coregistration.

UNLABELLED: The ictal hyperperfusion (compared with the interictal state) of the cerebellum and basal ganglia has not been investigated systematically in patients with temporal lobe epilepsy (TLE). Their ictal perfusion patterns were analyzed in relation to temporal and frontal hyperperfusion during TLE seizures using SPECT subtraction. METHODS: Thirty-three TLE patients had interictal and ictal SPECT, video-electroencephalographic (EEG) monitoring, and volumetric MRI. SPECT subtraction with MRI coregistration was performed using commercial software. The presence of ictal hyperperfusion was determined in the ipsilateral and contralateral temporal lobe, frontal lobe, cerebellum, and basal ganglia. RESULTS: All patients showed ictal hyperperfusion in the temporal lobe of seizure origin. Vermian cerebellar hyperperfusion (CH) was observed in 26 patients (78.8%) and hemispheric CH was found in 25 (75.8%). Compared with the side of the epileptogenic temporal lobe, there were 7 patients with ipsilateral hemispheric CH (28.0%), 15 with contralateral hemispheric CH (60.0%), and 3 with bilateral hemispheric CH (12.0%). CH was observed more frequently in patients with additional frontal hyperperfusion (14/15, 93.3%; 2 ipsilateral to the seizure focus, 10 contralateral, and 2 bilateral) than in patients without frontal hyperperfusion (11/18, 61.1%). Among 18 patients with temporal hyperperfusion without frontal hyperperfusion, 11 patients showed hemispheric CH (5 ipsilateral to seizure focus, 5 contralateral, 1 bilateral). Hyperperfusion in the basal ganglia (BGH) was seen in 11 of the 15 patients with temporal and frontal hyperperfusion (73.3%) and in 11 of the 18 with only temporal hyperperfusion (61.1%). In 17 patients with unilateral BGH (13 ipsilateral to the seizure focus, 4 contralateral), CH contralateral to the BGH was observed in 14 (82.5%), CH ipsilateral to the BGH was found in 2 (11.8%), and CH bilateral to the BGH was found in 1 (5.9%). CONCLUSION: During TLE seizures, hemispheric CH occurred not only in contralateral but also in ipsilateral or bilateral cerebellar hemispheres to the side of seizure origin. Although temporal lobe origin seizures associated with additional frontal hyperperfusion produced more frequent hemispheric CH, seizures showing only temporal hyperperfusion without frontal hyperperfusion could produce BGH and CH. To determine the side of hemispheric CH, the most important factor appears to be the side of BGH, not the side of seizure origin.

Adolescent↗
PubMed2000

The binding of substrate analogs to phosphotriesterase.

Phosphotriesterase (PTE) from Pseudomonas diminuta catalyzes the detoxification of organophosphates such as the widely utilized insecticide paraoxon and the chemical warfare agent sarin. The three-dimensional structure of the enzyme is known from high resolution x-ray crystallographic analyses. Each subunit of the homodimer folds into a so-called TIM barrel, with eight strands of parallel beta-sheet. The two zinc ions required for activity are positioned at the C-terminal portion of the beta-barrel. Here, we describe the three-dimensional structure of PTE complexed with the inhibitor diisopropyl methyl phosphonate, which serves as a mimic for sarin. Additionally, the structure of the enzyme complexed with triethyl phosphate is also presented. In the case of the PTE-diisopropyl methyl phosphonate complex, the phosphoryl oxygen of the inhibitor coordinates to the more solvent-exposed zinc ion (2.5 A), thereby lending support to the presumed catalytic mechanism involving metal coordination of the substrate. In the PTE-triethyl phosphate complex, the phosphoryl oxygen of the inhibitor is positioned at 3.4 A from the more solvent-exposed zinc ion. The two structures described in this report provide additional molecular understanding for the ability of this remarkable enzyme to hydrolyze such a wide range of organophosphorus substrates.

Aryldialkylphosphatase↗
PubMed2000

Effect of advanced glycation end products on lens epithelial cells in vitro.

The extended exposure of proteins to reducing sugars leads to nonenzymatic glycation with the accumulation of advanced glycation end products (AGEs). Long-lived proteins, such as collagen and crystallins, are subjected to this modification, and are implicated as causal factors in several diseases including diabetic complications, cataracts, and arteriosclerosis. One means through which AGEs modulate cellular interactions is via binding to specific receptors. In the current study, the existence of AGEs in human anterior polar lens capsules of cataracts was confirmed using a combination of dot-immunoblot and fluorescent detection. Human lens epithelial cells (LECs) attached to anterior lens capsules expressed mRNA for the receptor for AGEs (RAGE). The interaction of LECs with AGEs using bovine lens epithelial explants demonstrated that AGEs induced mRNAs and proteins of fibronectin, collagen type I, aberrant extracellular matrix proteins, and alpha-SMA, a specific marker for myofibroblastic cells. These findings suggest that AGEs may alter cellular functions which induce mRNAs and proteins associated with fibrosis in LECs.

Actins↗
PubMed2000

Mapping of functional organization in human visual cortex: electrical cortical stimulation.

OBJECTIVES: To investigate the pattern of functional organization in the human visual cortex through electrical cortical stimulation. METHODS: Electrical cortical stimulation was applied to the occipital cortex and adjacent cortices using subdural grid electrodes in 23 epilepsy patients. Diverse visual responses were recorded. These responses were divided into different categories according to the specific response modalities, such as form, color, and motion. Form visual responses were further subdivided into simple, intermediate, and complex responses. The cortical localization of subdural electrodes was identified using MRI-CT coregistration. The cortical distribution of different visual responses was projected into three-dimensional surface renderings of the brain. The distribution and frequency of subdural electrodes showing different visual responses were quantified by calculating the percentage of the number of electrodes showing one specific type of visual response at the corresponding anatomic region to the total number of electrodes in all brain regions that produced the same response. RESULTS: Simple form responses were obtained mostly at the occipital pole and the inferior occipital gyrus (47.4%) and the striate cortex (42.4%). Intermediate form responses occurred mainly on the peristriate cortex (52.5%) and the lateral occipital (28.0%) and fusiform gyri (19.5%). Complex forms were produced by stimulation of the basal temporo-occipital region (57.6%) and the lateral temporal or lateral temporo-occipital junctional region (42.4%). Color responses occurred on the basal occipital area, mostly at the fusiform (40.0%) and lingual gyri (36.0%). Moving sensations were evoked by stimulation of the basal temporo-occipital (28.4%) and the mesial parieto-occipital or temporo-parieto-occipital junctional regions (23.9%). CONCLUSIONS: Different modalities of vision, such as form, color, and moving sensation, appeared to be distributed and organized in different areas of the human visual cortex.

Adolescent↗
PubMed2000

Effect of an additional 1-hour T-piece trial on weaning outcome at minimal pressure support.

PURPOSE: The purpose of this article was to investigate the effect of an additional 1-hour T-piece trial at the level of minimum pressure support (PSmin) on weaning outcome. MATERIALS AND METHODS: Open, randomized, prospective study of 44 patients who had received mechanical ventilation for more than 3 days.Thirty-six patients satisfied the protocol. There were 42 weaning trials. The patients were randomized into an intervention group (additional 1-hour period of T-piece trial) and a control group (extubation directly) at PSmin. Blood gas analysis and estimation of respiratory and hemodynamic variables were performed at the 15 cm H2O level of pressure support. Measurements were repeated at PSmin and during weaning process (in intervention group). RESULTS: Mean PSmin level was 7.6 (+/- 1.9) cm H2O. There were no differences in total ventilation time (TVT), acute physiology and chronic health evaluation (APACHE) II score, nutritional indices, and respiratory mechanics on PSmin between the two groups. The weaning success rate and the reintubation rate were similar for the intervention group (55% and 18%, respectively) and control group (70% and 20%, respectively). Work of breathing, pressure time product, and tidal volume significantly worsened after a 1-hour T-piece trial when compared with those values measured at PSmin in the intervention group (P < .05). For the combined patient sample, TVT and tidal volume at PSmin were significantly different between the patients with weaning success (246 +/- 195 hours, 0.43 +/- 0.11 L) and those with weaning failure (407 +/- 248 hours, 0.35 +/- 0.10 L) (P < .05 in each). CONCLUSION: There were no advantages in weaning outcome by the addition of a 1-hour T-piece trial compared with prompt extubation at PSmin.

APACHE↗
PubMed2000

Opposite ictal perfusion patterns of subtracted SPECT. Hyperperfusion and hypoperfusion.

To investigate the patterns of ictal perfusion and related clinical factors, single photon emission computed tomography (SPECT) subtraction was performed in 61 patients who had undergone epilepsy surgery. In addition to the ictal hyperperfusion region, the ictal hypoperfusion area was obtained by SPECT subtraction. The ictal perfusion patterns of subtracted SPECT were classified into focal hyperperfusion, hyperperfusion-plus, combined hyperperfusion-hypoperfusion and focal hypoperfusion only. The concordance rate of seizure localization was 91.8% in the combined analysis of ictal hyperperfusion-hypoperfusion by SPECT subtraction, 85.2% in hyperperfusion images of SPECT subtraction and 68.9% in the visual inspection of ictal SPECT. Ictal hypoperfusion occurred less frequently in temporal lobe epilepsy (TLE) than in extra-TLE. Mesial temporal hyperperfusion alone was seen only in mesial TLE while lateral temporal hyperperfusion alone was observed only in neocortical TLE. Hippocampal sclerosis had a much lower incidence of ictal hypoperfusion than other pathologies. Some patients showed ictal hypoperfusion at the epileptic focus with ictal hyperperfusion in the neighbouring brain regions where ictal discharges propagated. Hypoperfusion as well as hyperperfusion in ictal SPECT should be considered for localizing epileptic focus. The mechanism of ictal hypoperfusion could be an intra-ictal early exhaustion of seizure focus or a steal phenomenon associated with the propagation of ictal discharges to adjacent brain areas.

Adolescent↗
PubMed2000

Analysis of gene promoters for two tomato polygalacturonases expressed in abscission zones and the stigma.

The tomato (Lycopersicon esculentum cv Ailsa Craig) polygalacturonase genes TAPG1 (LYCes;Pga1;2) and TAPG4 (LYCes;Pga1;5) are abundantly expressed in both abscission zones and the pistils of mature flowers. To further investigate the spatial and temporal expression patterns for these genes, the TAPG gene promoters were ligated to beta-glucuronidase (GUS) reporter genes and transformed into tomato. GUS expression with both constructs was similar and entirely consistent with the expression patterns of the native gene transcripts. GUS activity was observed in the weakening abscission zones of the leaf petiole, flower and fruit pedicel, flower corolla, and fruit calyx. In leaf petiole and flower pedicel zones this activity was enhanced by ethylene and inhibited by indole-3-acetic acid. On induction of abscission with ethylene, GUS accumulation was much earlier in TAPG4:GUS than in TAPG1:GUS transformants. Moreover, TAPG4:GUS staining appeared to predominate in the vascular bundles relative to surrounding cortex cells whereas TAPG1:GUS was more evenly distributed across the separation layer. Like the native genes, GUS was also expressed in the stigma. Activity was not apparent in pistils until the flowers had opened and was confined to the stigma and style immediately proximal to it. A minimal promoter construct consisting of a 247-bp 5'-upstream element from TAPG1 was found to be sufficient to direct GUS expression in both abscission zones and the stigma.

Ethylenes↗
PubMed2000

Correlation of temporal lobe glucose metabolism with the Wada memory test.

PURPOSE: The goal of the present study was to examine the relationship of 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) and the Wada memory test in lateralizing memory dominance and epileptic focus. METHODS: FDG-PET and the Wada test were performed in 18 patients with temporal lobe epilepsy (TLE). The asymmetry indices of FDG-PET (PET-AI) were calculated in mesial, polar, anterolateral, midlateral, and posterolateral regions of the temporal lobe, and those of Wada memory test (Wada-AI) were obtained as well. RESULTS: The Wada-AI was significantly correlated with PET-AI in mesial (r = 0.67, p = 0.003), polar (r = 0.55, p = 0.019), anterolateral (r = 0.55, p = 0.019), and midlateral (r = 0.51, p = 0.031) regions of the temporal lobe. However, after a linear regression analysis, PET-AI of only the mesial temporal region was significantly correlated with Wada-AI (p = 0.008). Wada-AI could correctly lateralize the seizure focus in 90% of the left TLE and 75% of the right TLE patients. The PET-AI of the mesial temporal region showed the highest sensitivity of seizure lateralization (80% of left TLE and 87.5% of right TLE). PET-AI of other temporal regions had lower sensitivities (50-80% of left TLE, 20-75% of right TLE). One or two patients showed false seizure lateralization by PET-AI on each temporal region. CONCLUSIONS: Although FDG-PET hypometabolism is observed at both mesial and lateral regions of the temporal lobe in mesial TLE, mesial temporal region appeared to be a dominant and leading area for lateralizing Wada memory dominance and epileptic focus.

Adolescent↗
PubMed2000

Contralateral EEG slowing and amobarbital distribution in Wada test: an intracarotid SPECT study.

PURPOSE: To relate the occurrence of contralateral electroencephalogram slowing (CES) to amobarbital distribution, we performed electroencephalogram (EEG) monitoring and intracarotid single photon emission computed tomography (SPECT) during an intracarotid amobarbital procedure (IAP). METHODS: IAP was performed on 22 patients with temporal lobe epilepsy. CES was defined as the occurrence of significant EEG slowing on the contralateral hemisphere (>50% of the ipsilateral hemisphere slowing) after amobarbital injection. To map the distribution of the amobarbital, we injected a mixture of amobarbital and (99m)technetium-ethylcysteinate dimer (99mTc-ECD) into the internal carotid artery and performed a brain SPECT 2 h later. In the SPECT images, regions of interest were determined by ipsilateral and contralateral anterior cerebral artery territories (iACA, cACA), ipsilateral and contralateral middle cerebral artery territories (iMCA, cMCA), and ipsilateral and contralateral posterior cerebral artery territories (iPCA, cPCA), as well as ipsilateral and contralateral anterior and posterior mesial temporal regions (iAMT, cAMT, iPMT, cPMT). The perfusion of amobarbital was interpreted visually in each region. RESULTS: Amobarbital was distributed in the iMCA in all the patients; in the iACA in 20 (90.9%) patients; in the iAMT in 14 (63.5%); and in the iPCA and iPMT in only two (9.1%). CES was observed in 13 (59.1%) patients. Cross-perfusion of amobarbital in limited areas of the cACA were observed in only four of 13 patients. Wada retention memory scores (WRMS) showed no significant difference between the CES- (n = 9) and CES+ (n = 13) groups. CONCLUSIONS: Amobarbital rarely perfused the iPCA territory and the iPMT region and was rarely delivered to the contralateral hemisphere. The occurrence of CES was not related to the cross-perfusion of amobarbital. CES appears to be produced by a transient functional disconnection from the ipsilateral hemisphere.

Adolescent↗
PubMed2000

Surgical treatment of intractable epilepsy accompanying cortical dysplasia.

OBJECT: Surgical treatment of cortical dysplasia (CD) together with intractable seizures is challenging because both visualization and localization of the lesion are difficult, correlation with seizure foci requires comprehensive study, and the surgical outcomes reported thus far are unsatisfactory. The authors report their experience in the surgical treatment of CD classified according to a surgical point of view. METHODS: The definition of CD used in this study was a dysplastic lesion visible on magnetic resonance (MR) images or a lesion that, although not visible on MR images, was diagnosed as moderate-to-severe dysplasia by using pathological analysis. During the last 4.5 years, the authors treated 36 patients with intractable epilepsy accompanied by CD. They divided the 36 cases of CD into four characteristic groups: Group A, diffuse bilateral hemispheric dysplasia; Group B, diffuse lobar dysplasia; Group C, focal dysplasia; and Group D, a moderate to severe degree of CD with a normal appearance on MR images. All but one patient in Group C were monitored in the epilepsy monitoring unit by using subdural electrodes for seizure localization and functional mapping. The incidence of CD among a cohort of 291 patients who had undergone epilepsy surgery at the authors' center during the study period was 12.4%. The mean age of the 36 patients was 21.3 years and the mean age at seizure onset was 8.5 years. The mean follow-up period was 26 months. Twenty-six patients (72.2%) belonged to Engel Class I or II (20 and six, respectively). There were five cases in Group A, nine in Group B, nine in Group C, and 13 in Group D. Patients in Groups A and B were significantly younger at seizure onset and had significantly poorer surgical outcomes compared with patients in Groups C and D (p < 0.05). If outcome is compared on the basis of the extent of removal of CD, patients in whom CD was completely removed had significantly better outcomes than those in whom CD was only partially removed (p < 0.001). CONCLUSIONS: The authors conclude that intractable epilepsy accompanied by CD can be treated surgically using comprehensive preoperative approaches. Deliberate resective procedures aimed at complete removal of dysplastic tissue ensure excellent seizure control without permanent neurological deficit.

Adolescent↗
PubMed1999

The SH2-SH2-SH3 domain of phospholipase C-gamma1 directly binds to translational elongation factor-1alpha.

Phospholipase C-gamma1 (PLC-gamma1) is a lipase that hydrolyzes PIP2 to generate two second messengers, IP3 and DAG. By using the yeast two-hybrid system, we identified the translational elongation factor-1alpha (EF-1alpha) as a binding protein of PLC-gamma1 from the human B-lymphocyte library. Direct interaction between EF-1alpha and PLC-gamma1 was confirmed by the in vitro binding experiment using purified PLC-gamma1. Furthermore, from the in vitro binding experiment, we could demonstrate that the carboxyl terminal region of EF-1alpha is involved in the interaction with PLC-gamma1, and that both SH2 and SH3 domains of PLC-gamma1 are required for the interaction with EF-1alpha. In vivo interaction between EF-1alpha and PLC-gamma1 was confirmed by the immunoprecipitation experiment using anti-EF-1alpha antibody. The interaction between EF-1alpha and PLC-gamma1 was enhanced by EGF-treatment. Taken together, we suggest that EF-1alpha might play a role in PLC-gamma1-mediated signal transduction.

Animals↗
PubMed1999

Molecular cloning and characterization of a human cDNA and gene encoding a novel acid ceramidase-like protein.

Computer-assisted database analysis of sequences homologous to human acid ceramidase (ASAH) revealed a 1233-bp cDNA (previously designated cPj-LTR) whose 266-amino-acid open reading frame had approximately 36% identity with the ASAH polypeptide. Based on this high degree of homology, we undertook further molecular characterization of cPj-LTR and now report the full-length cDNA sequence, complete gene structure (renamed human ASAHL since it is a human acid ceramidase-like sequence), chromosomal location, primer extension and promoter analysis, and transient expression results. The full-length human ASAHL cDNA was 1825 bp and contained an open-reading frame encoding a 359-amino-acid polypeptide that was 33% identical and 69% similar to the ASAH polypeptide over its entire length. Numerous short regions of complete identity were observed between these two sequences and two sequences obtained from the Caenorhabditis elegans genome database. The 30-kb human ASAHL genomic sequence contained 11 exons, which ranged in size from 26 to 671 bp, and 10 introns, which ranged from 150 bp to 6.4 kb. The gene was localized to the chromosomal region 4q21.1 by fluorescence in situ hybridization analysis. Northern blotting experiments revealed a major 2.0-kb ASAHL transcript that was expressed at high levels in the liver and kidney, but at relatively low levels in other tissues such as the lung, heart, and brain. Sequence analysis of the 5'-flanking region of the human ASAHL gene revealed a putative promoter region that lacked a TATA box and was GC rich, typical features of a housekeeping gene promoter, as well as several tissue-specific and/or hormone-induced transcription regulatory sites. 5'-Deletion analysis localized the promoter activity to a 1. 1-kb fragment within this region. A major transcription start site also was located 72 bp upstream from the ATG translation initiation site by primer extension analysis. Expression analysis of a green fluorescence protein/ASAHL fusion protein in COS-1 cells revealed a punctate, perinuclear distribution, although no acid ceramidase activity was detected in the transfected cells using a fluorescence-based in vitro assay system.

5' Untranslated Regions↗
PubMed1999

Stereochemical preferences for chiral substrates by the bacterial phosphotriesterase.

The bacterial phosphotriesterase from Pseudomonas diminuta catalyzes the hydrolysis of organophosphate nerve agents such as paraoxon (diethyl p-nitrophenyl phosphate) with a turnover number of approximately 10(4) s(-1). The active site of the enzyme has been shown to be composed of a binuclear Zn2+ complex with a bridging hydroxide. The utilization of chiral phosphotriesters has demonstrated that the overall hydrolytic reaction occurs with net inversion of stereochemistry at the phosphorus center. The stereochemical constraints of the active site have been probed by the synthesis and characterization of paraoxon analogs. One or both of the two ethoxy substituents of paraoxon have been replaced with various combinations of methyl, isopropyl, or phenyl groups. Racemic mixtures and individual enantiomers were tested as substrates for the phosphotriesterase. In general, the kinetic constants (k(cat) and k(cat)/Km) for the (-)-enantiomers were one to two orders of magnitude greater than the (+)-enantiomer. Conversely, acetylcholinesterase was more rapidly inactivated by the (+)-enantiomers than the (-)-enantiomers. These results were examined in the context of the three-dimensional structure of the bacterial phosphotriesterase.

Acetylcholinesterase↗