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Biomedical subjects

B S Chang

Publications and source records attributed to B S Chang.

At least 19 recordsLinked to original sources
PubMed2006

A familial syndrome of unilateral polymicrogyria affecting the right hemisphere.

A number of familial syndromes of bilateral polymicrogyria (PMG) have been described, but reported unilateral PMG cases have generally been sporadic. The authors identified four families in which unilateral right-sided PMG on MRI was present in more than one individual, with pathologic confirmation in one. Core clinical features included contralateral hemiparesis, developmental delay, and focal seizures. The authors' findings suggest that unilateral PMG exists in a familial syndrome of probable germline genetic origin.

Adolescent↗
PubMed2005

Reading impairment in the neuronal migration disorder of periventricular nodular heterotopia.

OBJECTIVE: To define the behavioral profile of periventricular nodular heterotopia (PNH), a malformation of cortical development that is associated with seizures but reportedly normal intelligence, and to correlate the results with anatomic and clinical features of this disorder. METHODS: Ten consecutive subjects with PNH, all with epilepsy and at least two periventricular nodules, were studied with structural MRI and neuropsychological testing. Behavioral results were statistically analyzed for correlation with other features of PNH. RESULTS: Eight of 10 subjects had deficits in reading skills despite normal intelligence. Processing speed and executive function were also impaired in some subjects. More marked reading difficulties were seen in subjects with more widely distributed heterotopia. There was no correlation between reading skills and epilepsy severity or antiepileptic medication use. CONCLUSION: The neuronal migration disorder of periventricular nodular heterotopia is associated with an impairment in reading skills despite the presence of normal intelligence.

Adolescent↗
PubMed2005

The presence of megamitochondria in the ellipsoid of photoreceptor inner segment of the zebrafish retina.

Although the megamitochondria (MM) were localized in various pathological conditions, normal retina of some mammalian species was reported to include MM for various physiological roles. However, it was not clearly confirmed whether the MM is present in the retina of lower vertebrate as well. In this study, we tried to show the presence of the MM in the zebrafish retina using electron microscopic technique. In all the photoreceptors including rods, cones and double cones of the zebrafish retina, MM were observed in the ellipsoid of inner segment. In the photoreceptor epllipsoid of the zebrafish retina, the mitochondria located in the central portion of the ellipsoid had a highly electron-dense matrix, which were accompanied by the mitochondria with electron-lucent matrix in the apical portion of the ellipsoid. The presence of MM was more clearly discernable in the rods, which were localized under the double cones. This finding is somewhat different from those observed in the previous studies because MM were localized in the inner segment of cones, but were not in those of rods in the case of mammalian retina. Although the exact physiological meaning for the presence of MM in some vertebrate species should be further studied, the present study could show that the MM in the ellipsoid of the retinal photoreceptors was not only restricted in some mammalian species.

Animals↗
PubMed2004

Bilateral generalized polymicrogyria (BGP): a distinct syndrome of cortical malformation.

BACKGROUND: Syndromes of bilateral symmetric polymicrogyria include an autosomal recessive form of bilateral frontoparietal polymicrogyria (BFPP), in which the malformation is most severe rostrally. The authors describe a new syndrome they have termed "bilateral generalized polymicrogyria" (BGP), in which the malformation occurs in a generalized distribution but is often most severe in the perisylvian regions. METHODS: Patients with bilateral polymicrogyria were identified from multiple medical centers worldwide. The diagnosis of BGP was based on findings from conventional spin echo MRI and, in one case, postmortem neuropathologic findings. Genetic analysis was performed for those patients from consanguineous pedigrees and those with multiple affected siblings to rule out linkage to the BFPP locus on chromosome 16q. RESULTS: Twelve patients were identified with BGP. Clinical features included cognitive and motor delay as well as seizures. Some specific features characteristic of other known bilateral polymicrogyria syndromes, such as pseudobulbar palsy and dysconjugate gaze, were not commonly seen in these patients. Radiologically, polymicrogyria appeared widespread but was often most severe in the perisylvian regions. Pathologic examination in one case revealed a diffusely thin and excessively folded cerebral cortex lacking normal six-layered architecture. Seven patients subjected to genetic analysis did not demonstrate linkage to the BFPP locus. CONCLUSIONS: BGP is a distinct syndrome of cortical malformation. Several features allow BGP to be distinguished from other disorders on the growing list of bilateral symmetric polymicrogyria syndromes.

Abnormalities, Multiple↗
PubMed2003

Leakage of cement in percutaneous transpedicular vertebroplasty for painful osteoporotic compression fractures.

e analysed the CT scans and radiographs of 76 vertebrae in 49 patients who underwent vertebroplasty for painful osteoporotic compression fractures. Leaks of cement were classified into three types: those via the basivertebral vein (type B), via the segmental vein (type S), and through a cortical defect (type C). More leaks were identified on CT scans than on radiographs by a factor of 1.5 (74/49). Most type-B (93%) and type-S (86%) leaks were missed or underestimated on a lateral radiograph which is usually the only view used during the injection of cement. Of the leaks into the spinal canal, only 7% (2/28) were correctly identified on radiographs. The areas on lateral radiographs where this type of leak may be observed were divided into four zones, and their diagnostic value in predicting a leak into the spinal canal was evaluated. The results showed that cement in the neural foramina had the highest positive predictive value (86%).

Aged↗
PubMed2001

Online size-exclusion high-performance liquid chromatography light scattering and differential refractometry methods to determine degree of polymer conjugation to proteins and protein-protein or protein-ligand association states.

Characterizing the solution structure of protein-polymer conjugates and protein-ligand interactions is important in fields such as biotechnology and biochemistry. Size-exclusion high-performance liquid chromatography with online classical light scattering (LS), refractive index (RI), and UV detection offers a powerful tool in such characterization. Novel methods are presented utilizing LS, RI, and UV signals to rapidly determine the degree of conjugation and the molecular mass of the protein conjugate. Baseline resolution of the chromatographic peaks is not required; peaks need only be sufficiently separated to represent relatively pure fractions. An improved technique for determining the polypeptide-only mass of protein conjugates is also described. These techniques are applied to determining the degree of erythropoietin glycosylation, the degree of polyethylene glycol conjugation to RNase A and brain-derived neurotrophic factor, and the solution association states of these molecules. Calibration methods for the RI, UV, and LS detectors will also be addressed, as well as online methods to determine protein extinction coefficients and dn/dc values both unconjugated and conjugated protein molecules.

Animals↗
PubMed2001

Calcium-dependent catalytic activity of a novel phytase from Bacillus amyloliquefaciens DS11.

The thermostable phytase from Bacillus amyloliquefaciens DS11 hydrolyzes phytate (myo-inositol hexakisphosphate, IP6) to less phosphorylated myo-inositol phosphates in the presence of Ca2+. In this report, we discuss the unique Ca2+-dependent catalytic properties of the phytase and its specific substrate requirement. Initial rate kinetic studies of the phytase indicate that the enzyme activity follows a rapid equilibrium ordered mechanism in which binding of Ca2+ to the active site is necessary for the essential activation of the enzyme. Ca2+ turned out to be also required for the substrate because the phytase is only able to hydrolyze the calcium-phytate complex. In fact, both an excess amount of free Ca2+ and an excess of free phytate, which is not complexed with each other, can act as competitive inhibitors. The Ca2+-dependent catalytic activity of the enzyme was further confirmed, and the critical amino acid residues for the binding of Ca2+ and substrate were identified by site-specific mutagenesis studies. Isothermal titration calorimetry (ITC) was used to understand if the decreased enzymatic activity was related to poor Ca2+ binding. The pH dependence of the Vmax and Vmax/Km consistently supported these observations by demonstrating that the enzyme activity is dependent on the ionization of amino acid residues that are important for the binding of Ca2+ and the substrate. The Ca2+-dependent activation of enzyme and substrate was found to be different from other histidine acid phytases that hydrolyze metal-free phytate.

6-Phytase↗
PubMed2001

Correlation between biopsy and radical cystectomy in assessing grade and depth of invasion in bladder urothelial carcinoma.

OBJECTIVES: To assess the degree of correlation between the pathologic characteristics of the specimens obtained from biopsy and radical cystoprostatectomy. The stage and grade of bladder urothelial (transitional cell) carcinoma are important predictors of prognosis. METHODS: We retrospectively identified 169 cases of urothelial carcinoma from 222 radical cystectomies performed at University of Chicago Hospitals from 1992 to 1999. RESULTS: For all the cases in this study, the histologic grade, using the 1998 World Health Organization and International Society of Urological Pathologists (WHO/ISUP) classification, was identical when the biopsy specimen and radical cystectomy specimen were compared. However, when the same cases were assessed using the traditional three-grade system, the histologic grade increased or decreased by one grade in 19 (11%) and 8 (5%) of 169 cases, respectively. Patients with invasion of the lamina propria on biopsy had tumor extending outside the bladder in 15 (27%) of 55 cases. Patients with invasion of the muscularis propria on biopsy had tumor extending outside the bladder in 47 (49%) of 96 cases, including nodal metastasis in 22 (23%) of 96 cases. Overall, bladder biopsy underestimated the true extent of the disease in 78 (46%) of 169 cases. CONCLUSIONS: Using either the WHO/ISUP (1998) classification or the traditional three-grade system, the histologic grade of the biopsy specimen is a fairly good predictor of the final histologic grade. The preoperative biopsy tends to understage bladder cancer. Patients with muscularis propria invasion demonstrated by biopsy have a significantly higher risk of non-organ-confined disease than those with lamina propria invasion.

Aged↗
PubMed2001

Pharmaceutical significance of the cyclic imide form of recombinant human glial cell line derived neurotrophic factor.

PURPOSE: The purpose of this paper is to determine the significance of cyclic imide formation of an aspartic acid residue during storage on the pharmaceutical quality of a recombinant human glial cell line-derived neurotrophic factor (rhGDNF) formulation. METHODS: A combination of chromatography, peptide mapping, mass spectroscopy, and protein sequencing was used to purify and characterize the degradation product. Circular dichroism, 1,8-ANS and heparin binding, melting temperature determination, bioassays, and preclinical pharmacokinetic and toxicology testing were performed to examine its equivalence to native rhGDNF. RESULTS: The rhGDNF with cyclic imide at aspartic acid residue 96 showed identical activity, structure, pharmacokinetic profile, and toxicity profile to the native rhGDNF. CONCLUSIONS: Formation of cyclic imide at aspartic acid residue 96 does not affect the pharmaceutical quality of the rhGDNF formulation.

Animals↗
PubMed2001

Effect of enrofloxacin-Na against pathogens related to the respiratory and alimentary diseases in suckling and weanling piglets.

A field trial was conducted to evaluate effect of enrofloxacin-Na against pathogens related to the respiratory and alimentary diseases in eighty suckling piglets (6-7 days old) and eighty weanling piglets (5-6 weeks old). Respective twenty of the suckling and weanling piglets were assigned to each of 4 experimental groups; control (non-treated), clinical injection dose (CID), 2x clinical injection dose (2CID). and premix. A 0.05 ml (2.5 mg) of enrofloxacin-Na injection (5% solution, 1 ml) per kg body weight of piglets as CID was injected intramuscularly for 3 days and the clinical signs were observed for 9 days. The premix (150 ppm) of enrofloxacin-Na was administered with feed for 7 days ad libitum and the clinical signs were observed for 13 days. The enrofloxacin-Na-treated piglets showed a higher increase in body weight and a lower feed per gain than the control piglets. In addition, the treatment of enrofloxacin-Na, regardless of the route of administration, decreased the incidence rate of diarrhea in suckling piglets and respiratory symptoms in weanling piglets. The isolation index of E. coli and Cl. perfringens during the treatment periods was also lowered by the enrofloxacin-Na treatment in both suckling and weanling piglets. The antibiotics was also evaluated as safe locally and whole bodily as treated by injection or feeding. These results indicate that the newly developed antibiotics, enrofloxacin-Na, is very useful for the prevention and therapy of swine diseases in the pig industry.

Animals↗
PubMed2001

Spinal deformities in Noonan syndrome: a clinical review of sixty cases.

BACKGROUND: Skeletal abnormalities, including spinal deformities, in Noonan syndrome have been described, but no detailed and systematic study of such spinal deformities has been presented in the literature. METHODS: The cases of sixty patients with Noonan syndrome were reviewed retrospectively, and the general appearance, growth disturbance, and mental status of the patients were documented. Spinal deformities were evaluated radiographically, and the frequency, pattern, and severity of the curves were documented. RESULTS: Spinal deformity was present in eighteen (30%) of the sixty patients. Two patients had congenital spinal deformity. Of the remaining sixteen patients with scoliosis, nine had a single thoracic curve, four had a single thoracolumbar curve, and three had a double major curve. Thoracic lordosis was also present in three of these sixteen patients. No patient had only increased kyphosis or lordosis. The mean age when the spinal deformities were detected was nine years; seven deformities were detected before the age of seven years. Overall, surgery was recommended to eleven of the eighteen patients; it was recommended for the treatment of scoliosis (mean, 68.5 degrees; range, 45 degrees to 125 degrees ) in eight patients and for the treatment of an associated thoracic lordosis (8 degrees, 15 degrees, and 18 degrees ) in three. Seven of the eleven patients underwent spinal arthrodesis. The operation was deferred in one patient because malignant hyperthermia developed during the induction of anesthesia. CONCLUSIONS: Scoliosis with an associated thoracic lordosis occurs more frequently in Noonan syndrome than has been reported previously. Since the deformities tend to develop early and are relatively severe, a clinical and, if necessary, radiographic assessment of the spine with careful follow-up should be performed for early detection and treatment of spinal deformity. Although malignant hyperthermia is rare, all patients with Noonan syndrome should be considered to be at risk for the development of this complication before operative treatment.

Adolescent↗
PubMed2001

[Gene cloning and expression of human soluble interleukin-6 receptor in insect cells].

OBJECTIVE: To clone the human soluble interleukin-6 receptor(hsIL-6R) gene and expression in insect cell line. METHODS: The hsIL-6R gene was cloned into plasmid pAcGP67B. After co-transfection of recombinant plasmid and wild type AcNPV DNA, the rAcNPV was confirmed by the end point dilution assay and dot blot. Then it was purified by plaque assay. RESULTS: SDS-PAGE showed molecular weight of the expressed product was about 47,000. The expressed recombinant protein was confirmed to be specific and capable of binding its ligand IL-6 by Western blot and ligand-receptor binding assays. CONCLUSIONS: Secretory expression of hsIL-6R gene in baculovirus expression system was indicated. The expressed product had immunological and biological activities.

Animals↗
PubMed2000

Osteoconduction at porous hydroxyapatite with various pore configurations.

To assess the histological response and the reinforcing effects of bone ingrowth within porous hydroxyapatite (HA) implants depending on pore geometry, four kinds of cylindrical-type with parallel linear pores phi50, 100, 300, 500 microm), one kind of sponge-type with irregular interconnecting pores (phi250 microm) and one cross-type with crossing linear pores (phi100 x 120 microm) of porous HA were prepared. Eighty-four rabbits were divided into six groups, and a 5 x 5 x 7 mm sized porous HA block was inserted through the medial cortical window of the proximal tibia. Histomorphological changes were examined using light and scanning electron microscopy. A biomechanical compression test was performed using material test machines. After implantation, the implants showed different histological changes depending on pore geometry. Active osteoconduction was also found in the phi50 microm sized cylindrical-type porous HA. Evidence of remodeling of new bone and bone marrow formation within porous HA was found in the larger cylindrical-types (phi300, 500 microm), and the sponge- and cross-types. The biomechanical test showed that the ultimate compressive strength increased significantly in the phi300 microm sized cylindrical-type, and in the sponge- and cross-types eight weeks after implantation. Porous HA with cylindrical pores could be a useful graft material due to its strength, osteoconductivity and the ease with which its pore geometry can be controlled.

Animals↗
PubMed2000

Bias in phylogenetic reconstruction of vertebrate rhodopsin sequences.

Two spurious nodes were found in phylogenetic analyses of vertebrate rhodopsin sequences in comparison with well-established vertebrate relationships. These spurious reconstructions were well supported in bootstrap analyses and occurred independently of the method of phylogenetic analysis used (parsimony, distance, or likelihood). Use of this data set of vertebrate rhodopsin sequences allowed us to exploit established vertebrate relationships, as well as the considerable amount known about the molecular evolution of this gene, in order to identify important factors contributing to the spurious reconstructions. Simulation studies using parametric bootstrapping indicate that it is unlikely that the spurious nodes in the parsimony analyses are due to long branches or other topological effects. Rather, they appear to be due to base compositional bias at third positions, codon bias, and convergent evolution at nucleotide positions encoding the hydrophobic residues isoleucine, leucine, and valine. LogDet distance methods, as well as maximum-likelihood methods which allow for nonstationary changes in base composition, reduce but do not entirely eliminate support for the spurious resolutions. Inclusion of five additional rhodopsin sequences in the phylogenetic analyses largely corrected one of the spurious reconstructions while leaving the other unaffected. The additional sequences not only were more proximal to the corrected node, but were also found to have intermediate levels of base composition and codon bias as compared with neighboring sequences on the tree. This study shows that the spurious reconstructions can be corrected either by excluding third positions, as well as those encoding the amino acids Ile, Val, and Leu (which may not be ideal, as these sites can contain useful phylogenetic signal for other parts of the tree), or by the addition of sequences that reduce problems associated with convergent evolution.

Animals↗
PubMed1999

Bcl-xL regulates apoptosis by heterodimerization-dependent and -independent mechanisms.

A hydrophobic cleft formed by the BH1, BH2 and BH3 domains of Bcl-xL is responsible for interactions between Bcl-xL and BH3-containing death agonists. Mutants were constructed which did not bind to Bax but retained anti-apoptotic activity. Since Bcl-xL can form an ion channel in synthetic lipid membranes, the possibility that this property has a role in heterodimerization-independent cell survival was tested by replacing amino acids within the predicted channel-forming domain with the corresponding amino acids from Bax. The resulting chimera showed a reduced ability to adopt an open conductance state over a wide range of membrane potentials. Although this construct retained the ability to heterodimerize with Bax and to inhibit apoptosis, when a mutation was introduced that rendered the chimera incapable of heterodimerization, the resulting protein failed to prevent both apoptosis in mammalian cells and Bax-mediated growth defect in yeast. Similar to mammalian cells undergoing apoptosis, yeast cells expressing Bax exhibited changes in mitochondrial properties that were inhibited by Bcl-xL through heterodimerization-dependent and -independent mechanisms. These data suggest that Bcl-xL regulates cell survival by at least two distinct mechanisms; one is associated with heterodimerization and the other with the ability to form a sustained ion channel.

Amino Acid Sequence↗
PubMed1999

'Loop' domain deletional mutant of Bcl-xL is as effective as p29Bcl-xL in inhibiting radiation-induced cytosolic accumulation of cytochrome c (cyt c), caspase-3 activity, and apoptosis.

PURPOSE/OBJECTIVE: To investigate the effect of the enforced expression of p29Bcl-xL or its loop deletional mutant, p18Bcl-xLdelta, on irradiation-induced apoptosis and cell-cycle distribution of HL-60 cells. MATERIALS & METHODS: We compared the irradiation-induced molecular cascade of apoptosis in control human AML HL-60/neo versus Bcl-xL overexpressing (approximately 8-fold) (HL-60/Bcl-xL) and HL-60/Bcl-XLdelta cells that express the loop domain deletional mutant construct (delta26-83 AA) of Bcl-xL. The three cell lines were irradiated with 6MV photons to varying doses up to 20 Gy. Following this, cytosolic cyt c levels, caspase-3 activity, and the Bcl-2 family of proteins were evaluated utilizing Western blot analysis (whole cell lysate or cytosolic S-100 fraction). Apoptosis was assessed by internucleosomal DNA fragmentation, Annexin-V staining and FACS analysis, as well as by morphologic criteria. The cell-cycle effects of radiation were analyzed by flow cytometry. RESULTS: Eight hours following irradiation (12 Gy) of HL-60/neo cells, a marked increase (approximately 8-fold) in the cytosolic accumulation of cyt c in the S-100 fraction was observed. This was associated with the cleavage of caspase-3, as well as the generation of its poly (ADP-ribose) polymerase (PARP) and DFF (DNA fragmentation factor)-45 cleavage activity. Twenty-four to forty-eight hours after irradiation, internucleosomal DNA fragmentation and positive Annexin-V staining (32.3+/-3.3%) was detected in HL-60/neo cells. In contrast, in both HL-60/Bcl-xL and HL-60/Bcl-xLdelta cells, a significantly lower percentage of apoptotic cells (p<0.05) were detected and internucleosomal DNA fragmentation was not induced. Following irradiation, Western analysis neither demonstrated any significant alteration in Bcl-2, p29Bcl-xL, p18Bcl-xLdelta, or Bax; nor induced CD95 (Fas receptor) or Fas ligand expression in any cell type. However, in all cell types, irradiation produced approximately a 2-fold increase in the percentage of cells in the G2/M phase of the cell cycle. CONCLUSION: These results demonstrate that an intact loop domain is not necessary for the full antiapoptotic function of Bcl-xL against irradiation-induced cytosolic accumulation of cyt c, caspase activation, and apoptosis of HL-60 cells. Additionally, the cell-cycle effects of ionizing radiation in HL-60 cells are not affected by enforced expression of Bcl-xL or Bcl-xLdelta.

Apoptosis↗
PubMed1999

Reversibility of heat-induced denaturation of the recombinant human megakaryocyte growth and development factor.

PURPOSE: The present study was performed to examine the effect of solution conditions on the reversibility of the thermal denaturation of megakaryocyte growth and development factor (rHuMGDF). METHODS: Changes in the far UV CD spectra of rHuMGDF with temperature were used to monitor the thermal denaturation of the protein, and the recovery of folded protein following a return to room temperature. The effect of protein concentration, scan rate, and buffer composition on thermal denaturation and on the reversibility were determined. Surface tension measurements were used to determine the effect of this unfolding reaction on the surface adsorption of the protein. Sedimentation velocity was used to assess recovery of native monomer and the size of soluble aggregates. In addition, monomeric protein remaining in solution after incubation at 37 degrees C for 2 weeks in either 10 mM imidazole of 10 mM phosphate was determined. RESULTS: In phosphate buffer the rHuMGDF irreversibly precipitates upon unfolding under all the conditions examined. In imidazole the unfolding is at least partially reversible, with no visible precipitate seen; the degree of reversibility increased by lowering both protein and salt concentrations, and the amount of time spent at elevated temperature. In order to compare thermal unfolding occuring with different degrees of reversibility, the melting temperature was defined as the temperature at which melting begins. The melting temperature itself is relatively independent of the buffer composition, or experimental conditions. At low protein concentrations the protein stabilizer sucrose had a marginal effect on the thermal transition of rHuMGDF, while at protein concentrations of about 2 mg/ml the inclusion of sucrose increased the apparent melting temperature by about 4 degrees C, to that seen at low protein concentrations, but had little effect on the reversibility of denaturation. Inclusion of 1 or 2 M urea did not affect the reaction. Surface tension measurements of rHuMGDF solutions showed little difference before and after melting, and in the presence or absence of sucrose. When unfolding is irreversible, the MGDF appears to form soluble aggregates of tetramers to 14-mers, while under reversible conditions native monomer is recovered. More monomeric MGDF remained in solution following storage for 2 weeks at 37 degrees C in imidazole than in phosphate, in both the presence and absence of sucrose. CONCLUSIONS: These results can be explained by assuming that thermal denaturation proceeds as a two-step reaction, the first step being the equilibrium between folded and unfolded states, while the second step is a slow irreversible aggregation. The different buffer systems affect the rate of the aggregation step, but not the intrinsic thermal stability nor the rate of the unfolding step.

Buffers↗