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Biomedical subjects

S Chuang

Publications and source records attributed to S Chuang.

At least 19 recordsLinked to original sources
PubMed1999

Distribution of salicylic acid in human stratum corneum following topical application in vivo: a comparison of six different formulations.

Distribution of salicylic acid in human stratum corneum from treatment of six different formulations was assessed by quantitation of drug content in sequentially tape-stripped stratum corneum after a single 2-h dose was applied unoccluded to skin on the ventral forearm of four female subjects. The profile and total amounts of stratum corneum removed in 20 tape-strips varied among different types of formulations. With or without normalization by the total stratum corneum weights removed, the extent of drug delivery to the stratum corneum decreased in the following order: SA (5%) > > SAC (10%), Duofilm (16.7%) > TSSS (2%) > SAO (10%), Salic (2.5%), the percentage in parentheses indicating the salicylic acid concentration in each formulation. The greatest topical bioavailability was observed for the alcoholic solution containing glycerol (SA). The 10% collodion formulation (SAC) was found to deliver an amount of salicylic acid into the stratum corneum 2-fold greater than 10% ointment formulation (SAO). Use of absorption ointment (TSSS) also increased the uptake of salicylic acid into the stratum corneum in comparison with formulations based on simple ointment (SAO) and oil in water (o/w) cream (Salic). The partitioning of salicylic acid from collodion formulations (SAC and Duofilm) appeared to be concentration-independent. The results of this study indicate that topical bioavailability of salicylic acid in the stratum corneum varies substantially among different formulations.

Adhesives↗
PubMed1999

Autocrine interaction between IL-5 and IL-1beta mediates altered responsiveness of atopic asthmatic sensitized airway smooth muscle.

T-helper type 2 (Th2) cytokines have been implicated in the pathogenesis of the pulmonary inflammatory response and altered bronchial responsiveness in allergic asthma. To elucidate the mechanism of Th2-dependent mediation of altered airway responsiveness in the atopic asthmatic state, the expression and actions of specific cytokines were examined in isolated rabbit and human airway smooth muscle (ASM) tissues and cultured cells passively sensitized with sera from atopic asthmatic patients or nonatopic/nonasthmatic (control) subjects. Relative to control tissues, the atopic asthmatic sensitized ASM exhibited significantly enhanced maximal isometric contractility to acetylcholine and attenuated relaxation responses to isoproterenol. These proasthmatic changes in agonist responsiveness were ablated by pretreating the atopic sensitized tissues with either an IL-5 receptor blocking antibody (IL-5ra) or the human recombinant IL-1 receptor antagonist (IL-1ra), whereas an IL-4 neutralizing antibody had no effect. Moreover, relative to controls, atopic asthmatic sensitized ASM cells demonstrated an initial, early (after 3 hours of incubation) increased mRNA expression and protein release of IL-5. This was followed (after 6 hours of incubation) by an enhanced mRNA expression and release of IL-1beta protein, an effect that was inhibited in sensitized cells pretreated with IL-5ra. Extended studies demonstrated that naive ASM exposed to exogenously administered IL-5 exhibited an induced upregulated mRNA expression and protein release of IL-1beta associated with proasthmatic-like changes in ASM constrictor and relaxant responsiveness, and that these effects were ablated in tissues pretreated with IL-1ra. Taken together, these observations provide new evidence that (a) the Th2 cytokine IL-5 and the pleiotropic proinflammatory cytokine IL-1beta are endogenously released by atopic asthmatic sensitized ASM and mechanistically interact to mediate the proasthmatic perturbations in ASM responsiveness; and (b) the nature of this interaction is given by an initial endogenous release of IL-5, which then acts to induce the autologous release of IL-1beta by the sensitized ASM itself, resulting in its autocrine manifestation of the proasthmatic phenotype.

Adolescent↗
PubMed1998

Cerebellar arteriovenous malformations in children.

We review the presentation, imaging findings and outcome in 18 children with cerebellar arteriovenous malformations (AVM). This group is of particular interest because of the reported poor outcome despite modern imaging and neurosurgical techniques. All children had CT and 15 underwent catheter angiography at presentation. Several of the children in the latter part of the study had MRI. Of the 18 children, 17 presented with a ruptured AVM producing intracranial haemorrhage. The remaining child presented with temporal lobe epilepsy and was shown to have temporal, vermian and cerebellar hemisphere AVM. This child had other stigmata of Osler-Weber-Rendu syndrome. Three other children had pre-existing abnormalities of possible relevance. One had a vascular malformation of the cheek and mandible, one a documented chromosomal abnormality and another a midline cleft upper lip and palate. Six of the 17 children with a ruptured cerebellar AVM died within 7 days of the ictus. Vascular pathology other than an AVM was found in 10 of the 14 children with a ruptured cerebellar AVM who had angiography: 4 intranidal aneurysms, 5 venous aneurysms and 2 cases of venous outflow obstruction (one child having both an aneurysm and obstruction). The severity of clinical presentation was directly related to the size of the acute haematoma, which was a reasonable predictor of outcome.

Adolescent↗
PubMed1994

Localized scleroderma: imaging features.

Localized scleroderma is distinct from the diffuse form of scleroderma and does not show Raynaud's phenomenon and visceral involvement. The imaging features in 23 patients ranging from 2 to 17 years of age (mean 11.1 years) were reviewed. Leg length discrepancy and muscle atrophy were the most common findings (five patients), with two patients also showing modelling deformity of the fibula. One patient with lower extremity involvement showed abnormal bone marrow signals on MR. Disabling joint contracture requiring orthopedic intervention was noted in one patient. In two patients with "en coup de sabre" facial deformity, CT and MR scans revealed intracranial calcifications and white matter abnormality in the ipsilateral frontal lobes, with one also showing migrational abnormality. In a third patient, CT revealed white matter abnormality in the ipsilateral parietal lobe. In one patient with progressive facial hemiatrophy, CT and MR scans showed the underlying hypoplastic left maxillary antrum and cheek. Imaging studies of areas of clinical concern revealed positive findings in half our patients.

Adolescent↗
PubMed1993

Mitochondrial encephalomyopathy, lactic acidosis, stroke-like episodes (MELAS): clinical, radiological, pathological, and genetic observations.

We reviewed 10 patients (5 males, 5 females) with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes. The age of symptom onset ranged from 3 months to 12 years. All had lactic acidosis, multiple stroke-like events with secondary neurological deficits, radiological changes of progressive brain infarction, and muscle biopsy showing ragged-red fibers. In patients with earlier onset of symptoms (< 2 yr), involvement tended to be more diffuse, with failure to thrive and early onset of delayed development. Patients whose symptoms appeared later tended to have focal neurological deficits with migraine-like headache, and a rate of cognitive regression reflecting the rapidity of disease progression. Radiological changes included multiple areas of infarction with initial predilection for parietal occipital areas, progressing to generalized atrophy. Pathological findings in muscle biopsies included type 1 fiber predominance, ragged-red fibers, increased intermyofibrillar lipid deposition, and abnormal mitochondria. Four patients showed mitochondrial DNA tRNA mutation at position 3,243. No difference was noted in clinical, radiological, or pathological findings in patients with and without this mutation, suggesting that multiple sites of point mutation may give rise to mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes.

Base Sequence↗
PubMed1991

Brain tumors in children and adolescents--II. The neuroanatomy of deficits in working, associative and serial-order memory.

The neuroanatomy of memory deficits was studied in 46 children and adolescents with brain tumors. CT-scan reconstructions of 88 brain regions were coded with respect to tumor and related damage, and multiple regression procedures established patterns of brain damage predictive of memory deficits. Two forms of memory revealed non-overlapping focal neuroanatomical substrates: memory for the serial order of pictures that corresponded to heard words involved structures in the limbic system and hypothalamic-pituitary axis; whereas working memory, in which each of a succession of heard words is stored in temporary memory long enough to be compared to or contrasted with incoming words, involved the pineal-habenular region and the anterior and medial thalamic nuclei. Memory for semantically-based word-picture associations, in contrast, was unaffected by tumors in several subcortical brain regions. These data bear on current analyses of the neural substrates of associative and representational memory.

Adolescent↗
PubMed1987

The surgical treatment of childhood moyamoya disease.

Moyamoya disease is a progressive disorder, predominantly seen in childhood, that can cause severe permanent disability. The search for effective treatment has largely been unsuccessful in the past, but recent efforts at surgical intervention have shown promising results. The natural history of moyamoya disease, the options for treatment, and a series of patients from the Hospital for Sick Children in Toronto are reviewed. The results of surgical treatment are encouraging and the authors believe that it should be offered to all pediatric patients in the progressive stage of the disease.

Adolescent↗
PubMed1986

Tumors and cysts.

"Congenital" tumors that cause hydrocephalus early in life are large masses and can easily be detected by ultrasound. CT is better for differentiating among the diverse types of mass lesions and is performed after screening by ultrasound. In our experience, ultrasound has proved successful for visualizing all of the intracranial cysts except those in the temporal fossa. Most patients with temporal fossa cysts, however, have other symptoms and signs, such as asymmetric head and seizures that lead to further investigation and correct diagnosis despite the failure to identify the temporal cysts by ultrasound. With newer and better ultrasound equipment, the detection of temporal fossa arachnoid cysts will be improved. We believe that neurosonography should be the initial tool for investigating infants and neonates who present with large heads or abnormally rapid increase in head size.

Brain↗
PubMed1986

Lumbo-peritoneal shunt malfunction. A new, simple and reliable CT sign.

Sixty CT scans in 31 patients who underwent lumboperitoneal shunting for communicating hydrocephalus showed that the size of the ventricles did not represent a good indicator of shunt malfunction. Instead, we discovered that the size of the basal cisterns around the brain stem enabled us to predict blockage earlier and more reliably. In a well functioning shunt, the basal cisterns are usually not visualized. In children with clinical shunt malfunction the cisterns dilate and become visible again. This occurs earlier and more frequently than ventricular enlargement. We therefore conclude that visible cisterns in association with persistent symptoms of malfunction are more reliable predictors of a true blockage that requires shunt revision than serial studies of ventricular size.

Brain↗
PubMed1986

Pediatric surgical neuroangiography. A multicentre approach.

Adult patients who require sophisticated embolization procedures are usually referred to centres where such expertise is available. Because of the special circumstances in the pediatric age group, this type of referral is often not feasible. The authors describe a model in which multiple pediatric institutions have access to sophisticated interventional neuroradiologic procedures through the collaboration of a group of neuroradiologists. The preliminary results are encouraging and appear to indicate that embolization in the pediatric age group can be safe and reliable if performed by well trained teams.

Child↗
PubMed1984

Computed tomography in Alexander's disease.

Computed tomography demonstrated contrast-enhancing lesions in the periventricular frontal regions, caudate nuclei, and thalami in an infant with Alexander's disease. The distribution of the enhancing lesions corresponded to the areas in which Rosenthal fibers were most prominent. These radiological findings have not been described in other white matter diseases; thus, they may help to distinguish Alexander's disease from Canavan's disease and decrease the necessity for diagnostic brain biopsy.

Brain↗
PubMed1983

Yeast inorganic pyrophosphatase substrate recognition.

Monodentate Co(NH3)5PPi was determined not to be a substrate for yeast inorganic pyrophosphatase while P1,P2-bidentate Co(NH3)4PPi was turned over by the enzyme at a rate of 7.5 min-1. A kinetic analysis of the substrate activities of the P1,P2-bidentate complexes, Co(en)2PPi, Cr(NH3)4PPi, Cr(H2O)(NH3)3PPi, and Cr(H2O)2(NH3)2PPi, and Cr(H2O)4PPi was carried out in order to access the potential role of the metal-water ligands in productive binding. While substitution of the H2O ligands with NH3 ligands had a minimal affect on the Km for Mg2+, the binding affinity of the complexes decreased with an increasing NH3/H2O ligand ratio as did the turnover number of the corresponding central complexes. The Co(en)2PPi complex was hydrolyzed at a rate approximately 0.6% of that for the Co(NH3)4PPi complex. The substrate activities of beta, gamma-bidentate Co(NH3)4PPPi and alpha, beta, gamma-tridentate Co(NH3)3PPP with pyrophosphatase were also tested. While both complexes were shown to bind tightly to the Mg2+-activated enzyme neither was hydrolyzed. On the other hand, in the presence of the Zn2+-activated enzyme the tridentate complex was turned over at a rate of 0.17 min-1 while the bidentate complex remained inert to hydrolysis.

Binding Sites↗
PubMed1983

Radiology of the suprapatellar region.

The gross and radiological anatomy of the suprapatellar region has been reviewed and its clinical application outlined. In most patients an accurate assessment of the presence of effusion and lipohaemarthrosis of the knee joint can be made and the possibility of excluding joint disease is discussed. In the individual patient the careful application of the radiological anatomy of this region may prevent mistakes in the localisation of various pathological processes.

Contrast Media↗
PubMed1982

Intracranial neoplasms in children: the effect of computed tomography on age distribution.

In a review of all children with brain neoplasms evaluated at a large pediatric center during a three-year period following the introduction of computed tomography (CT), a change was observed in the age distribution at the time of clinical presentation as compared with a previous series evaluated prior to the introduction of CT. In children under six years of age, there was a highly significant trend for earlier diagnosis; within this age group, relatively more children were diagnosed in the first two years of life. Between six and twelve years of age, there was no change in frequency of brain tumor diagnosis between the two series. Above age twelve, there was again noted a highly significant increase in detection of brain tumors in the more recent series. These differences between the two series may be attributed, at least in part, to earlier referral and diagnosis since the advent of CT, although other factors cannot be excluded as possible causes of the differences.

Adolescent↗