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Biomedical subjects

P Hwang

Publications and source records attributed to P Hwang.

At least 37 records · Page 2Linked to original sources
PubMed1995

Pediatric magnetic source imaging.

Magnetic source imaging has changed the perspective of managing pediatric patients with epilepsy since its introduction into clinical imaging in the pediatric population. Magnetic source imaging can be important in understanding pediatric functional neuroanatomy and for epileptic surgery in children with intractable seizures. The use and efficacy of magnetic source imaging for surgical planning and patient management is demonstrated by case reports presented in this article.

Brain Mapping↗
PubMed1994

Saliva versus blood sampling for therapeutic drug monitoring in children: patient and parental preferences and an economic analysis.

The objective of this study was to conduct an assessment of patient and parental preferences and an economic analysis of hospital costs in sampling blood and saliva for therapeutic drug monitoring (TDM). Costs and preferences were evaluated in the course of a study, which compared anticonvulsant concentrations in blood routinely drawn for therapeutic monitoring and in saliva in infants and children attending a pediatric neurology clinic. Parents of 84.8% of children, and half of the children, indicated a preference for saliva sampling over venous blood drawing. Children who had been on medications that required therapeutic monitoring for < 2 years were more likely to prefer saliva sampling as compared to those who were under treatment for > or = 2 years. Computation, based upon a basic assumption that a registered nurse obtained blood and a medical technician or a registered nurse assistant sampled saliva, indicated that for every 1,000 cases of changing from blood to saliva sampling, total cost savings would amount to $1,930 for cooperative children and $1,660 for infants and uncooperative children. This saving is equivalent to approximately 100 h of a registered nurse's initial salary. The important contributions to the differential cost were derived from the requirements for more highly trained individuals to take the blood sample and from the doubling time required for the procedure.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Medical treatment of Rasmussen's syndrome (chronic encephalitis and epilepsy): effect of high-dose steroids or immunoglobulins in 19 patients.

We treated 19 patients with Rasmussen's syndrome (chronic encephalitis and epilepsy)--a rare progressive disorder of unknown etiology causing focal epilepsy, hemiparesis, and intellectual deterioration--with intravenous immunoglobulins, high-dose steroids, or both, to control seizures and improve the end point of the disease. Ten of 17 patients receiving steroids, and eight of nine patients receiving immunoglobulins, had some reduction of seizure frequency in the short term. Improvement in hemiparesis was slight. The effect of these drugs in ameliorating the end point of the disease in the long term remains unknown, and further multicenter studies with standardized protocols are warranted.

Adolescent↗
PubMed1993

Neuronal heterotopia with capillary penetration of neurons and cortical dysplasia in a patient with complex partial seizures. Case report.

Unusual pathological findings were encountered in a temporal lobectomy specimen from a 9-year-old boy with intractable complex partial seizures. Magnetic resonance imaging revealed an enlarged left temporal lobe, with diffuse high signal intensity over the cortex and poor gray-white differentiation on T2-weighted imaging; single-photon emission computerized tomography showed decreased blood flow. Active epileptiform discharges were identified in the left temporal lobe with focal slow waves and generalized epileptiform paroxysms. Pathologically, the cortex revealed changes of focal cortical dysplasia with extensive disorganization of neuronal morphology, layering, and orientation as well as focal polymicrogyria. The cortical-white matter junction was indistinct with extensive neuronal heterotopias in the white matter. Large pale balloon cells akin to those seen in tuberous sclerosis were found scattered within the cortex and white matter. The most striking finding was that of a heterotopic nodule in the white matter, which revealed abnormal neurons with penetration of cell bodies by capillaries. Ultrastructurally, there were no degenerative changes in these neurons, and this unusual phenomenon is attributed to a developmental disturbance affecting neuronal, glial, and vascular elements.

Brain Neoplasms↗
PubMed1992

Pain perception and effectiveness of the eutectic mixture of local anesthetics in children undergoing venipuncture.

The emulsion of lidocaine and prilocaine (EMLA) is effective in preventing the pain of venipuncture in children. It is therefore important to identify children who could benefit the most from EMLA. We studied the safety and feasibility of two methods of application of EMLA (patch and cream) in a randomized, open-label trial of EMLA patch versus EMLA cream in 160 children with chronic diseases undergoing venipuncture. EMLA patch or cream was applied 60 to 120 min before puncture. Pain was assessed by the children using a visual analogue score. Children also scored the pain of their last puncture and the pain of removing the tape. EMLA patch and cream had similar efficacy (visual analogue scores for the venipuncture were 8.5 +/- 16 and 9.5 +/- 17 out of 100, respectively). Side effects occurred in similar frequencies in the two groups. Adhesiveness of the patch was less effective than that of the cream with Tegaderm. Age was a major determinant of pain perception; younger children recalled more severe pain in their previous puncture. Children recently diagnosed had higher visual analogue scores than those with a long history of chronic disease. We concluded that EMLA patch and cream have a similar efficacy in children undergoing venipuncture. Young children recently diagnosed with chronic disease are most likely to benefit from EMLA.

Adolescent↗
PubMed1992

The pharmacology of chewable versus regular carbamazepine in chronically treated children with epilepsy.

We report the first comparison of Chewable and Regular Carbamazepine (CBZ) tablets in children with epilepsy. Forty-four children receiving chronic monotherapy CBZ participated. In month 1 children received regular CBZ; in month 2, the same dose of Chewable CBZ. Once per week fasting predose CBZ and CBZ epoxide serum levels were determined. In a subset of 15 children, at the end of each month serum levels were obtained every 2 hours for 12 hours beginning pre-dose. Standards for CBZ and CBZ epoxide were tested in each centre. Overall, weekly levels showed no consistent differences between the month on chewable CBZ and regular CBZ. Seizure control and rates of reported side effects were similar. In five patients chewable CBZ produced higher peak CBZ levels while five had higher peaks with regular CBZ. In conclusion, regular and chewable CBZ often have unpredictable differences in peak but not trough levels of CBZ suggesting that peak level side effects with one form of CBZ might be alleviated by changing to the other.

Carbamazepine↗
PubMed1990

Rare McArdle disease locus polymorphic site on 11q13 contains CpG sequence.

When probes throughout the McArdle disease (myophosphorylase) gene region were used to search for DNA polymorphisms, only an MspI polymorphism was found in 94 enzyme-probe combinations. Along with an insertion/deletion polymorphism more 3' to the gene locus, these polymorphisms will be informative in 75% of at-risk patients. These results contrast strikingly to the six polymorphic sites detected in 15 enzyme-probe combinations in the homologous Her's disease (liver phosphorylase) gene region. This single MspI polymorphic site includes a CpG sequence of known increased mutability suggesting that DNA regions with rare polymorphisms will have most polymorphic sites at sequences with enhanced mutability. Fluorescence in situ hybridization sublocalized this gene to proximal band 11q13, establishing a point of cross-reference between the physical and genetic maps.

Base Sequence↗
PubMed1990

Inhibition: its stability and correlates in sixteen- to forty-month-old children.

Inhibition was assessed in 144 Swedish children when they averaged 16 months of age using a composite measure tapping sociability toward strange adults, noninvolvement in peer play, and parental ratings of fearfulness. 91 children entered out-of-home care within 2 weeks of these initial assessments. Children were observed in this setting playing with peers; teachers and parents also rated children's adjustment to the out-of-home care settings. 1 and 2 years later, the children were assessed again, both at home and in the alternative care settings. Results showed that individual differences in inhibition were stable over the 2 years of the study. Inhibited children engaged in less high-quality peer play both at home and in the alternative care settings, and they were less able to play alone in their mothers' absence. On contemporaneous but not subsequent ratings, inhibited children had more difficulty adjusting to out-of-home care. Inhibition was not itself affected by out-of-home care experiences, and there were no sex differences in inhibition.

Child Day Care Centers↗
PubMed1988

Perceiving mitosis in eukaryotic cells.

A sensitive method has been developed for visualizing eukaryotic cells in mitosis (M) phase. It employs Zenker's fixative, which makes the plasma membrane but not the nuclear envelope permeable to immunoglobulins. Zenker's-fixed cells are exposed to an antibody which recognizes a major constituent of chromatin. In this case the antibody is a monoclonal (MC 21) which recognizes histone H2b. Because cells in M phase do not have an intact nuclear envelope, the antibody has access to and interacts with their chromatin. The presence of a nuclear envelope in Zenker's-fixed interphase cells precludes access of the antibody to the nuclear chromatin. Consequently, this indirect immunofluorescence procedure selectively labels M-phase cells. At high enough magnification some details of the chromatin figures are revealed. MC 21 recognizes the chromatin of cells of many different species. With appropriate fixation it can be used effectively on cells in culture. With some procedural modifications it can also be used with more complex tissue systems. Detailed mitotic patterns for chick embryos up to Day 3 of development have been obtained by this method.

Animals↗
PubMed1987

Intron/exon structure of the human gene for the muscle isozyme of glycogen phosphorylase.

The intron/exon organization of the human gene for glycogen phosphorylase has been determined. The segments of the polypeptide chain that corresponds to the 19 exons of the gene are examined for relationships between the three-dimensional structure to the protein and gene structure. Only weak correlations are observed between domains of phosphorylase and exons. The nucleotide binding domains that are found in phosphorylase and other glycolytic enzymes are examined for relationships between exons of the genes and structures of the domains. When mapped to the three-dimensional structures, the intron/exon boundaries are shown to be widely distributed in this family of protein domains.

Amino Acid Sequence↗
PubMed1987

Isolating and sequencing the infrequent 3'-ends of a specific mRNA.

Procedures are described for identification of very infrequent in vivo 3'-ends of RNA. After purification by filter hybridization, the 3'-ends were labeled with [5'-32P] cytosine-3'-P in the RNA ligase reaction. Significantly fewer counts were incorporated in the ligase reaction than in the polynucleotide kinase reaction to label 5'-ends. The incorporation was increased by increasing the RNA concentration 5-10 fold by using only one round of filter hybridization. Non-specific RNA binding could be eliminated by RNase A treatment of the filter if a great excess of denatured heterologous DNA was immobilized along with the DNA probe. Significant amounts of DNA were released when eluting the hybrid RNA from such filters. DNA inhibited the ligase reaction, while its DNase products were even more inhibitory. Treatment of the DNase products with alkaline phosphatase completely eliminated the inhibition. We detected no spurious 5'- or 3'-ends generated in the hybrid RNA by RNase A activity used to reduce the non-specific RNA. Also, RNase T1 could be used in place of RNase A to eliminate non-specific RNA binding, but about 25 times more RNase T1 (microgram/microgram) was needed. We used partial alkali digestion to sequence 3'-ends. A major (one hit) and minor (two hit) set of products were produced which could be distinguished from each other by alkaline phosphatase treatment and homochromatography of the products.

Base Sequence↗
PubMed1987

Surgical management of children with temporal lobe epilepsy and mass lesions.

In a review of 48 children who underwent temporal lobectomy for temporal lobe epilepsy, 16 patients had mass lesions in the temporal lobe. These mass lesions consisted of 12 tumors, 3 vascular malformations, and 1 arachnoid cyst. In 9 of 10 patients where the hippocampus was present in the pathological specimen and was not involved by tumor, there was concomitant mesial temporal sclerosis. All 16 patients have been followed for more than 1 year. Nine are free of seizures, with 4 of these 9 still on medication. Seven patients have had a greater than 50% reduction in seizures.

Adolescent↗
PubMed1984

Purification and crystallization of bovine liver phosphorylase.

We have purified and crystallized bovine liver phosphorylase a. Starting from 2.5 kg of liver, we obtain 250 mg of phosphorylase a, with a specific activity of 90 units/mg, representing 15% recovery. SDS polyacrylamide gels show three bands, a 95 kDa band with the same mobility as muscle phosphorylase, and two smaller bands of 55 kDa and 40 kDa, which are probably proteolytic fragments. These fragments remain associated and have native conformation and catalytic activity. Crystals which diffract to 2.8 A resolution, were prepared by the hanging drop method using polyethylene glycol PEG 4000 as precipitant. The crystals were prepared in the presence of activators maltotriose and phosphite and crack when placed in solutions containing the inhibitors glucose and caffeine. This suggests phosphorylase is present in an active conformation.

Animals↗
PubMed1976

Characterization of natriuretic activity from posterior pituitary lobes.

Previous studies have indicated the existence of natriuretic factors of hormonal nature with the posterior pituitary gland as a possible site of origin. It was in this light that a series of experiments was designed to examine the posterior pituitary for such factors. Acetic acid extracts of porcine and bovine posterior pituitary lobe tissue were subjected to gel filtration on Sephadex G-25. Several fractions in the molecular size range of 1000 were obtained which possessed potent natriuretic activity as assayed in rats. The activity of these fractions maximally increased sodium excretion to 6-8 muequiv./min, a 10- to 40-fold increase above control, when administered intraperitoneally to hydropenic, conscious rats. However, oxytocin and vasopressin, present in the posterior pituitary are natriuretic. These hormones were measured by radioimmunoassay, and invariably only those fractions which contained vasopressin and (or) oxytocin possessed natriuretic activity. Moreover, the extent of the natriuresis could be accounted for by the vasopressin and (or) oxytocin content of the test fractions. The natriuretic property of this material was abolished by treatment with thioglycollate. Further purification of natriuretic fractions by ion exchange resins, thin-layer chromatography and isoelectric focusing failed to resolve natriuretic activity from vasopressin and oxytocin. Similar results were observed following analysis of fractions isolated by gel filtration of acetic acid extracts of ventral hypothalamus tissue. The natriuretic fractions isolated from hypothalamic tissue were indistinguishable from oxytocin and vasopressin. These experiments suggest that the natriuretic activity in neurohypophyseal extracts can be attributed to oxytocin and vasopressin.

Animals↗