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Biomedical subjects

S Koh

Publications and source records attributed to S Koh.

At least 19 recordsLinked to original sources
PubMed2006

Magnetic source imaging localizes epileptogenic zone in children with tuberous sclerosis complex.

The authors assessed whether magnetoencephalography/magnetic source imaging (MEG/MSI) identified epileptogenic zones in patients with tuberous sclerosis complex (TSC). In six TSC children with focal seizures, ictal video-EEG predicted the region of resection with 56% sensitivity, 80% specificity, and 77% accuracy (p = 0.02), whereas interictal MEG/MSI fared better (100%, 94%, and 95%, respectively; p < 0.0001). Interictal MEG/MSI seems to identify epileptogenic zones more accurately in children with TSC and focal intractable epilepsy.

Child↗
PubMed2005

Surgery for symptomatic infant-onset epileptic encephalopathy with and without infantile spasms.

Children undergoing surgery with infant-onset epilepsy were classified into those with medically refractory infantile spasms (IS), successfully treated IS, and no IS history, and the groups were compared for pre- and postsurgery clinical and Vineland Adaptive Behavior Scale (VABS) developmental quotients (DQ). Children without an IS history were older at surgery and had longer epilepsy durations than those with IS despite similar substrates, surgeries, and seizure frequencies. In all groups, better postsurgery VABS-DQ scores were associated with early surgical intervention indicating that infant-onset epilepsy patients with or without IS are at risk for seizure-induced encephalopathy.

Cohort Studies↗
PubMed2004

Antenatal use of a novel vaginal birth training device by term primiparous women in Singapore.

INTRODUCTION: To study the use, safety and effectiveness of a novel antenatal vaginal birth training device (EPI-NO) in primiparous women. METHODS: Antenatal use of the EPI-NO vaginal birth trainer was prospectively studied in 31 primiparous booked patients who were delivered by obstetricians from July to December 2002 at the KK Women's and Children's Hospital. This was studied in relation to episiotomy rate, perineal trauma and analgesic requirements during the postpartum period. A patient questionnaire form was used to assess their perception of pain and how well they coped with its use. For comparison, perineal trauma was also studied retrospectively in 60 consecutive obstetrician-booked primiparous term patients who had normal vaginal delivery (NVD) and who did not use EPI-NO during the same study period. RESULTS: The mean length of usage was for 2.1 weeks (standard deviation [sd] 1.2 weeks). The mean frequency of use was 5.3 episodes per week (sd 2.1, range 1 to 7). There was no laceration and vaginal infection arising from its usage. There was a case of minimal bleeding post-usage. There were 20 (64.5 percent) NVDs, four (12.9 percent) forceps deliveries, five vacuum deliveries (16.1 percent) and two (6.5 percent) Caesarean sections. Of the 29 vaginal delivery cases, 19 (65.5 percent) had episiotomy, eight (27.6 percent) had lacerations, and two (6.9 percent) did not sustain laceration. The reasons for episiotomy in the 19 cases were nine cases of pending tearing of vagina/perineum, nine cases of instrumental vaginal deliveries, and one to shorten second stage. There was no third degree tear. 21 (67.7 percent) out of 30 required a painkiller. The majority of patients (17; 54.8 percent) appeared to be comfortable with the use of EPI-NO. All coped well with vaginal examination after using EPI-NO perineal training. Comparing among term primiparous NVD cases with (n value equals 20) and without (n value equals 60) EPI-NO, the perineal trauma rate (90.0 percent vs 96.6 percent, p value equals 0.24) was slightly but not significantly lower in the EPI-NO group. The episiotomy rate was significantly lower (50.0 percent vs 93.3 percent, p value is less than 0.0001) and the extent of perineal trauma in the patient appeared to be less severe in cases using EPI-NO. CONCLUSION: EPI-NO appeared to be safe and acceptable to the majority of users. Although birth training with EPI-NO significantly decreases the rate of episiotomies in term primiparous patients, and the degree of perineal tissue injury appeared to be less in the EPI-NO group especially among those with lacerations, the overall perineal trauma rate was slightly but not significantly lower, in view of the higher spontaneous laceration rate in the EPI-NO group.

Analgesics↗
PubMed2003

[Surgically treated mucoepidermoid carcinoma in a 6-year-old boy; report of a case].

A 6-year-old boy was admitted to our hospital with a history of recurrent obstructive pneumonia and hemoptysis. A chest computed tomography (CT) showed atelectasis in the left lower lobe. Angiograpy, which was performed for the suspicion of pulmonary sequestration, showed no feeding artery and revealed bleeding from the bronchial artery in the left lower lobe. As hemoptysis would not stop, an emergency left lower lobectomy was performed. Macroscopic examination of the resected specimen revealed a mass measuring 20 x 15 x 17 mm in the S8 proximal lung parenchyma, bronchiectasis, and an abscess in the distal lung parenchyma. Histopathologic examination determined the tumor was a mucoepidermoid carcinoma. Immunohistochemical staining revealed some tumor cells were positive for CA 19-9. The child has not had a recurrence 3 years postoperatively.

Bronchial Neoplasms↗
PubMed2002

Surgical treatment for chronic radial head dislocation.

BACKGROUND: The treatment of chronic radial head dislocation remains controversial. High rates of redislocation and complications have been reported after surgery. In our view, correction of malalignment with ulnar osteotomy is the key to a good surgical result. METHODS: Since 1975, twenty-two patients were treated surgically for chronic radial head dislocation at our hospital. The procedure consisted of open reduction of a dislocated radial head followed by radial and/or ulnar osteotomy, with or without reconstruction of the annular ligament or by reconstruction of the annular ligament alone. The ages of the patients ranged from four to twenty years. In 1991, we modified the surgical technique by performing an oblique ulnar osteotomy with angulation and elongation and rigid plate fixation. Bone-grafting at the osteotomy site was also performed if necessary. A cast was applied with the forearm in neutral rotation and was worn for two to four weeks. Nine patients were treated with this modified technique. RESULTS: The mean interval between the initial injury and the reconstructive surgery was ten months. There were no serious surgical complications. Of the thirteen patients treated before 1991, four had a good reduction and seven had redislocation. Seven patients had restricted forearm rotation postoperatively. Of the nine patients treated with the modified osteotomy since 1991, seven had a good reduction. Two patients, who had had slight radial head deformity preoperatively, had subluxation postoperatively. Two patients had restricted forearm rotation. CONCLUSIONS: Since we modified our technique for ulnar osteotomy, good reduction of the radial head has been achieved without causing serious contracture. Both angulation and elongation of the ulna are required to allow the radial head to reduce.

Adolescent↗
PubMed2001

Decreased glutamate receptor 2 expression and enhanced epileptogenesis in immature rat hippocampus after perinatal hypoxia-induced seizures.

Hypoxic encephalopathy is the most common cause of neonatal seizures and can lead to chronic epilepsy. In rats at postnatal days 10-12 (P10-12), global hypoxia induces spontaneous seizures and chronically decreases seizure threshold, thus mimicking clinical aspects of neonatal hypoxia. We have shown previously that the acute and chronic epileptogenic effects of hypoxia are age-dependent and require AMPA receptor activation. In this study, we aimed to determine whether hypoxia-induced seizures and epileptogenesis are associated with maturational and seizure-induced changes in AMPA receptor composition and function. Northern and Western blots indicated that glutamate receptor 2 (GluR2) mRNA and protein expression were significantly lower in neocortex and hippocampus at P10-12 compared with adult. After hypoxia-induced seizures at P10, GluR2 mRNA was significantly decreased within 48 hr, and GluR2 protein was significantly decreased within 96 hr. AMPA-induced Co(2+) uptake by neurons in hippocampal slices indicated higher expression of Ca(2+)-permeable AMPA receptors in immature pyramidal neurons compared with adult. In slices obtained 96 hr after hypoxia-induced seizures, AMPA-induced Co(2+) uptake was significantly increased compared with age-matched controls, and field recordings revealed increased tetanus-induced afterdischarges that could be kindled in the absence of NMDA receptor activation. In situ end labeling showed no acute or delayed cell death after hypoxia-induced seizures. Our results indicate that susceptibility to hypoxia-induced seizures occurs during a developmental stage in which the expression of Ca(2+)-permeable AMPA receptors is relatively high. Furthermore, perinatal hypoxia-induced seizures induce increased expression of Ca(2+)-permeable AMPA receptors and an increased capacity for AMPA receptor-mediated epileptogenesis without inducing cell death.

Aging↗
PubMed2001

Topiramate blocks perinatal hypoxia-induced seizures in rat pups.

Neonatal seizures caused by hypoxia can be refractory to conventional anticonvulsants. Currently, there is no effective postnatal intervention for newborn infants with hypoxic encephalopathy to prevent brain injury and long-term neurologic sequelae. We previously developed a rat model of perinatal hypoxia-induced seizures with subsequent long-term increases in seizure susceptibility and showed that these epileptogenic effects are selectively blocked by the alpha-amino-3-hydoxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor antagonist 6-nitro-7-sulfamoylbenzo(f)quinoxaline-2,3-dione. Using this model of perinatal seizures, we evaluated the efficacy of topiramate, a structurally novel anticonvulsant drug recently shown to attenuate AMPA/kainate currents. Topiramate effectively suppressed acute seizures induced by perinatal hypoxia in a dose-related manner with a calculated ED50 of 2.1 mg/kg, i.p. Furthermore, in animals that had seizures suppressed by topiramate during acute hypoxia, there were no long-term increases in susceptibility to kainate-induced seizures and seizure-induced neuronal injury. Our results suggest that topiramate may have clinical potential as a therapeutic agent for refractory seizures in human neonates.

Animals↗
PubMed2000

Expression of integrated hepatitis B virus X variants in human hepatocellular carcinomas and its significance.

Hepatitis B virus X protein (HBX) has been implicated in the transactivation of diverse cellular genes and possibly also the pathogenesis of human hepatocellular carcinoma (HCC). We report the characterization of HBX variants from HBV-related human hepatocellular carcinoma (HCC). These HBX variants were integrated into the host chromosomes and also expressed in the HCC tissues. In addition, we report a novel in vitro HBX activity assay based on color changes that were indicative of the beta-galactosidase enzyme activity. Conducted in wheat germ lysates, the transactivating function of either wild type or mutant HBX protein was measured through their interaction with the Early Growth Response factor 1 (Egr-1) that controls the beta-galactosidase gene. Further analysis of these HBX deletion mutants using this assay may shed new insights on the significance of various mutations occurring in HCC-associated HBX.

Amino Acid Sequence↗
PubMed2000

Sleep apnea treatment improves seizure control in children with neurodevelopmental disorders.

Seizure disorder and sleep apnea are common chronic disorders in children, but the relationship between sleep apnea and seizure control has not been studied in the pediatric population. This retrospective review included nine children with neurodevelopmental disorders who had well-documented sleep apneic episodes and seizure disorders. Seizure frequency was reduced in five patients (56%) in the first 12 months after sleep apnea treatment without changes in their antiepileptic medications. Sleep apnea can be one of the seizure precipitants in children with epilepsy. This study indicates the importance of identifying sleep apnea when treating children with intractable epilepsy, particularly in those who are at high risk.

Anticonvulsants↗
PubMed2000

Cloning and functional characterization of a constitutively expressed nitrate transporter gene, OsNRT1, from rice.

Elucidating how rice (Oryza sativa) takes up nitrate at the molecular level could help improve the low recovery rate (<50%) of nitrogen fertilizer in rice paddies. As a first step toward that goal, we have cloned a nitrate transporter gene from rice called OsNRT1. OsNRT1 is a new member of a growing transporter family called PTR, which consists not only of nitrate transporters from higher plants that are homologs of the Arabidopsis CHL1 (AtNRT1) protein, but also peptide transporters from a wide variety of genera including animals, plants, fungi, and bacteria. However, despite the fact that OsNRT1 shares a higher degree of sequence identity with the two peptide transporters from plants (approximately 50%) than with the nitrate transporters (approximately 40%) of the PTR family, no peptide transport activity was observed when OsNRT1 was expressed in either Xenopus oocytes or yeast. Furthermore, contrasting the dual-affinity nitrate transport activity of CHL1, OsNRT1 displayed only low-affinity nitrate transport activity in Xenopus oocytes, with a K(m) value of approximately 9 mM. Northern-blot and in situ hybridization analysis indicated that OsNRT1 is constitutively expressed in the most external layer of the root, epidermis and root hair. These data strongly indicate that OsNRT1 encodes a constitutive component of a low-affinity nitrate uptake system for rice.

Amino Acid Sequence↗
PubMed2000

Epilepsy surgery in children with tuberous sclerosis complex: presurgical evaluation and outcome.

PURPOSE: Children with tuberous sclerosis complex (TSC) benefit from excisional surgery if seizures can be localized to a single tuber. We evaluated the role of noninvasive studies to localize the epileptogenic tuber/region (ET/R) and the outcome of focal resection. METHODS: We identified 21 children with TSC, ages 3 months to 15 years (mean 4.8 years). All had video-(electroencephalogram) EEG and magnetic resonance imaging (MRI) scans, and 18 also had ictal single photon emission-computed tomography (SPECT) studies. An ET/R was localized in 17 patients. Thirteen patients underwent resection guided by intraoperative electrocorticography (n = 7) or subdural monitoring (n = 6). RESULTS: Interictal EEG revealed a principal spike focus (PSF) that corresponded to the ET/R in 14 children. In seven, PSFs occurred in rhythmic runs. PSFs were not observed remote from the ET/R. Focal polymorphic slowing and attenuation occurred in the region of the PSF in 11 patients. Sixteen patients demonstrated an ictal focus corresponding to the ET/R. Ictal SPECT revealed focal hyperperfusion correlating with the ET/R in 10 patients. Although the MRIs in all children revealed multiple tubers, the ET/R corresponded to a large discrete tuber in 8 patients and a calcified tuber in 13 patients. Patchy calcified tubers were also seen elsewhere in six patients. At a mean follow-up of 26 months, 9 of the 13 children who underwent surgery were seizure-free, one had greater than 75% reduction in seizures, two were unchanged, and one was lost to follow-up. New seizures developed in one child from a contralateral tuber. CONCLUSIONS: Surgical resection of an ET/R alleviates seizures in most children with TSC and intractable epilepsy. The scalp EEG and MRI help define the ET/R and improve case selection when ictal SPECT is nonlocalizing.

Adolescent↗
PubMed2000

Selection criteria and preoperative investigation of patients with focal epilepsy who lack a localized structural lesion.

Children with medically resistant epilepsy are often referred for surgical evaluation. The absence of a specific focal lesion on MRI may render the work-up difficult. In response to the need to localize the primary area of epileptogenesis, surgery protocols are being developed which rely on clinical semiology, EEG and functional imaging data. In selected cases, intracranial EEG monitoring may be required. While testing more often depends on the convergence of modalities, it is possible to localize seizure origin in the majority of children, and fully excise the epileptogenic region. This review presents the etiology and preoperative modalities available for children with intractable, non-lesional epilepsy.

Brain↗
PubMed1999

Early-life seizures in rats increase susceptibility to seizure-induced brain injury in adulthood.

BACKGROUND: Early childhood convulsions have been correlated with the finding of subsequent hippocampal neuronal loss and memory impairment in patients with intractable temporal lobe epilepsy. There is little direct evidence, however, that links early seizures with the later development of epilepsy and selective hippocampal neuronal loss. OBJECTIVE: To study the long-term effect of early seizures on later seizure-induced neuronal damage and behavior. METHODS: We used a "two hit" rat seizure mode in which systemic kainate was used to induce seizures during the second week of life (P15) and again in adulthood (P45). Memory was subsequently tested using a Morris water maze, and brains were examined for histologic evidence of injury. RESULTS: Although the first kainate-induced seizure is not associated with detectable injury or cell death, it predisposes animals to more extensive neuronal injury after kainate-induced seizures in adulthood. Moreover, although early-life kainate-induced seizures cause no impairment of spatial learning, animals that have early-life and adult kainate-induced seizures perform significantly worse than those that have seizures only as adults. CONCLUSIONS: We concluded that early-life seizures, without causing overt cellular injury, predispose the brain to the damaging effect of seizures later in life.

Age Distribution↗