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Biomedical subjects

K Hsiao

Publications and source records attributed to K Hsiao.

At least 19 recordsLinked to original sources
PubMed2005

Paediatric home ventilatory support: the Auckland experience.

OBJECTIVES: To examine the trend over time, describe the disease categories treated, intervention success and outcomes of the children treated at home with continuous positive airway pressure (CPAP), non-invasive ventilation (NIV) and ventilation via tracheostomy (invasive ventilatory support, IVS) by the Respiratory Service at the Starship Children's Hospital in Auckland. METHODS: A retrospective review was undertaken of the Respiratory Service records from November 1991 to February 2004. RESULTS: Home CPAP, NIV or IVS was initiated in 160 children (89 boys, median age 6 years) in the study period. Sixty-nine (46 boys) remain on support and are still actively managed by the Starship Respiratory Service, of whom 46% live outside the Greater Auckland Region. Despite 42% of children being less than 5 years of age at initiation of therapy, institution of support failed in only 11%. The majority received treatment by non-invasive mask interface (68% (n = 108) CPAP, 29% (n = 47) NIV), with only 3% (n = 5) supported via tracheostomy. The numbers and complexity of support rose over the 12 years. Respiratory support was discontinued in 57% of cases, after a median of 12.5 months (range 3-52 months); in two-thirds, support was no longer required due to an improvement in the medical condition. The most common indication for support in current patients is respiratory parenchymal or airway disease followed by neuromuscular disease. Obesity is not a common indication. CONCLUSION: This review documents the increasing trend in children receiving respiratory support at home. Future planning and resources are needed to address this growing need.

Adolescent↗
PubMed2001

A surrogate-based approach for post-genomic partner identification.

BACKGROUND: Modern drug discovery is concerned with identification and validation of novel protein targets from among the 30,000 genes or more postulated to be present in the human genome. While protein-protein interactions may be central to many disease indications, it has been difficult to identify new chemical entities capable of regulating these interactions as either agonists or antagonists. RESULTS: In this paper, we show that peptide complements (or surrogates) derived from highly diverse random phage display libraries can be used for the identification of the expected natural biological partners for protein and non-protein targets. Our examples include surrogates isolated against both an extracellular secreted protein (TNFbeta) and intracellular disease related mRNAs. In each case, surrogates binding to these targets were obtained and found to contain partner information embedded in their amino acid sequences. Furthermore, this information was able to identify the correct biological partners from large human genome databases by rapid and integrated computer based searches. CONCLUSIONS: Modified versions of these surrogates should provide agents capable of modifying the activity of these targets and enable one to study their involvement in specific biological processes as a means of target validation for downstream drug discovery.

Computational Biology↗
PubMed2001

Induction of NADPH cytochrome P450 reductase by the Alzheimer beta-protein. Amyloid as a "foreign body".

A large body of data suggests that the Alzheimer's amyloid peptide (Abeta) causes degeneration and death of neurons by mechanisms that involve reactive oxygen species. The pathways involved in Abeta-mediated oxidative injury are only partially understood. We theorized that abnormal microaggregates and/or pathological conformations of Abeta peptides may behave as xenobiotics and trigger the induction of NADPH cytochrome P450 reductase (CP450r), an enzyme which, if induced by non-physiological substrates (such as xenobiotics like drugs or other 'foreign molecules'), is known to cause oxidative stress. In order to test this hypothesis, i.e. that Abeta can increase the expression of CP450r, SK-N-SH human neuroblastoma cells were exposed to Abeta25-35 and Abeta1-42 and then examined for induction of this enzyme in immunoblots, using specific antibodies. Following exposure to Abeta peptides, neuroblastoma cells showed a clear-cut induction of CP450r. To determine whether this mechanism is operational in vivo, we investigated the expression of CP450r in a transgenic mouse model of Alzheimer's disease (AD) and in brains from patients afflicted with AD, using an immunocytochemical approach. Tissue sections from brains of transgenic mice exhibited strong immunoreactivity for CP450r, surrounding amyloid deposits. The pattern of expression of CP450r was similar to that exhibited by neuritic and oxidative stress markers. Sections from non-transgenic mice showed no detectable immunoreactivity. Immunostaining of sections from four brains with neuropathologically confirmed AD showed a pattern of abnormality different from transgenic mice that was characterized by abnormal immunoreactivity for CP450r within the cytoplasm of cortical neurons. No labeling was seen in sections from aged-matched control brains. The data showed that CP450r is induced by Alzheimer amyloid peptide and that such a response must be considered as one possible mechanism whereby Abeta causes oxidative stress.

Alzheimer Disease↗
PubMed1999

Behavioral changes in transgenic mice expressing both amyloid precursor protein and presenilin-1 mutations: lack of association with amyloid deposits.

Mutations in the amyloid precursor protein (mAPP) and in presenilin 1 (mPS1) have both been linked to increased production of the beta-amyloid peptide (A beta). Doubly transgenic mice produced by mating of a parental line carrying the "Swedish" (K670N/M671L) APP mutation with a FAD4 (M146L) mutant presenilin 1 line developed numerous fibrillar A beta deposits by 6 months of age. Prior work demonstrated that mAPP and doubly transgenic (mAPP/mPS1) mice have deficits in Y-maze alternation behavior as early as 3 months of age. Increased activity was also apparent in the mAPP/mPS1 mice at this time point. These changes in Y-maze performance persisted in mAPP/mPS1 mice at 6 and 9 months of age. The mPS1 singly transgenic mice were not impaired on this task at any age. Six- and nine-month-old mice were also tested for spatial navigation behavior in the Morris water maze. In training trials, no differences in escape latency were detected among the four genotypes. In probe trials, no differences were detected in either the time spent in the trained quadrant or the number of platform crossings among the four groups. Histological staining for A beta amyloid deposits indicates that all doubly transgenic mice have amyloid deposits by 6 months of age (roughly 25 mice examined thus far), yet no 3-month-old mice have been found with deposits. A beta immunostaining confirmed that the 9-month-old mice tested behaviorally also have A beta deposits. Thus, doubly transgenic mice exhibited changes in Y-maze performance prior to the formation of amyloid deposits, which are essentially unchanged as the deposits increase in number and size to 9 months of age. Yet these mice fail to reveal impairments in spatial navigation at 6 or 9 months in spite of the increasing plaque burden. These data indicate that A beta deposits alone are not sufficient to cause robust spatial memory impairment in mice of this mixed background lineage and age.

Alzheimer Disease↗
PubMed1998

Accelerated Alzheimer-type phenotype in transgenic mice carrying both mutant amyloid precursor protein and presenilin 1 transgenes.

Genetic causes of Alzheimer's disease (AD) include mutations in the amyloid precursor protein (APP), presenilin 1 (PS1), and presenilin 2 (PS2) genes. The mutant APP(K670N,M671L) transgenic line, Tg2576, shows markedly elevated amyloid beta-protein (A beta) levels at an early age and, by 9-12 months, develops extracellular AD-type A beta deposits in the cortex and hippocampus. Mutant PS1 transgenic mice do not show abnormal pathology, but do display subtly elevated levels of the highly amyloidogenic 42- or 43-amino acid peptide A beta42(43). Here we demonstrate that the doubly transgenic progeny from a cross between line Tg2576 and a mutant PS1M146L transgenic line develop large numbers of fibrillar A beta deposits in cerebral cortex and hippocampus far earlier than their singly transgenic Tg2576 littermates. In the period preceding overt A beta deposition, the doubly transgenic mice show a selective 41% increase in A beta42(43) in their brains. Thus, the development of AD-like pathology is substantially enhanced when a PS1 mutation, which causes a modest increase in A beta42(43), is introduced into Tg2576-derived mice. Remarkably, both doubly and singly transgenic mice showed reduced spontaneous alternation performance in a "Y" maze before substantial A beta deposition was apparent. This suggests that some aspects of the behavioral phenotype in these mice may be related to an event that precedes plaque formation.

Alzheimer Disease↗
PubMed1998

Amyloid-beta deposition in Alzheimer transgenic mice is associated with oxidative stress.

Increased awareness for a role of oxidative stress in the pathogenesis of Alzheimer's disease has highlighted the issue of whether oxidative damage is a fundamental step in the pathogenesis or instead results from disease-associated pathology. In vitro experiments support both possibilities: Oxidative stress increases amyloid-beta production, and, conversely, amyloid-beta increases oxidative damage. To address the relationship between amyloid-beta and oxidative stress in vivo, we examined, using an array of oxidative markers, transgenic mice that overexpress amyloid-beta precursor protein and, as in Alzheimer's disease, develop characteristic amyloid-beta deposits within the brain parenchyma. Transgenic animals show the same type of oxidative damage that is found in Alzheimer's disease, and it is important that this damage directly correlates with the presence of amyloid-beta deposits. The significance of these studies is twofold. First, they provide evidence that amyloid-beta and oxidative damage are inextricably linked in vivo. Second, they support the use of transgenic animals for the development of antioxidant therapeutic strategies.

Aldehydes↗
PubMed1998

Microglial response to amyloid plaques in APPsw transgenic mice.

Microglial activation is central to the inflammatory response in Alzheimer's Disease (AD). A recently described mouse line, Tg(HuAPP695.K670N/M671L)2576, expressing human amyloid precursor protein with a familial AD gene mutation, age-related amyloid deposits, and memory deficits, was found to develop a significant microglial response using Griffonia simplicifolia lectin or phosphotyrosine probe to identify microglia Both Griffonia simplicifolia lectin and phosphotyrosine staining showed increased numbers of intensely labeled, often enlarged microglia clustered in and around plaques, consistent with microglial activation related to beta-amyloid formation. Using quantitative image analysis of coronal phosphotyrosine-immunostained sections, transgene-positive 10- to 16-month-old, hemizygous, hybrid Tg2576 (APPsw) animals showed significantly increased microglial density and size in plaque-forming areas of hippocampus and frontal, entorhinal, and occipital cortex. Quantitative analysis of microglia as a function of distance from the center of plaques (double labeled for A beta peptide and microglia) revealed highly significant, two- to fivefold elevations in microglial number and area within plaques compared with neighboring regions. Tg2576 beta-amyloid-plaque-forming mice should be a useful system for assessing the consequences of the microglial-mediated inflammatory response to beta-amyloid and developing anti-inflammatory therapeutic strategies for Alzheimer's disease. These results provide the first quantitative link between beta-amyloid plaque formation and microglial activation in an animal model with neuritic plaques and memory deficits.

Alzheimer Disease↗
PubMed1998

Evidence of oxidative stress and in vivo neurotoxicity of beta-amyloid in a transgenic mouse model of Alzheimer's disease: a chronic oxidative paradigm for testing antioxidant therapies in vivo.

Increased expression of antioxidant enzymes and heat-shock proteins are key markers of oxidative stress. Such proteins are abnormally present within the neuropathological lesions of Alzheimer's disease (AD), suggesting that oxidative stress may play significant but yet undefined roles in this disorder. To gain further insight into the role of oxidative stress in AD, we studied the expression of CuZn superoxide dismutase (SOD) and hemoxygenase-1 (HO-1), two established markers of oxidative stress, in a transgenic mouse model of AD. Immunohistochemistry with anti-SOD and anti-HO-1 antibodies revealed a very pronounced increase of these proteins only in aged transgene-positive mice. Interestingly, the distribution of the oxidative burden was largely overlapping with dystrophic neuritic elements in the mice as highlighted with anti-ubiquitin antibodies. Because the most conspicuous alterations were identified around amyloid (Abeta) deposits, our results provide strong support for the hypothesis that Abeta is neurotoxic in vivo and that such toxicity is mediated by free radicals. To obtain additional experimental evidence for such an interpretation (ie, a cause-effect relationship between Abeta and oxidative neurotoxicity), PC12 cells were exposed to increasing concentrations of Abeta or to oxidative stress. In agreement with the in vivo findings, either treatment caused marked induction of SOD or HO-1 in a dose-dependent fashion. These results validate the transgenic approach for the study of oxidative stress in AD and for the evaluation of antioxidant therapies in vivo.

Aging↗
PubMed1997

Activation of interferon-gamma inducing factor mediated by interleukin-1beta converting enzyme.

The interleukin-1beta (IL-1beta) converting enzyme (ICE) processes the inactive IL-1beta precursor to the proinflammatory cytokine. ICE was also shown to cleave the precursor of interferon-gamma inducing factor (IGIF) at the authentic processing site with high efficiency, thereby activating IGIF and facilitating its export. Lipopolysaccharide-activated ICE-deficient (ICE-/-) Kupffer cells synthesized the IGIF precursor but failed to process it into the active form. Interferon-gamma and IGIF were diminished in the sera of ICE-/- mice exposed to Propionibacterium acnes and lipopolysaccharide. The lack of multiple proinflammatory cytokines in ICE-/- mice may account for their protection from septic shock.

Animals↗
PubMed1997

Vesicle movement in rat hepatocytes is reduced by ethanol exposure: alterations in microtubule-based motor enzymes.

BACKGROUND & AIMS: Ethanol is known to alter vesicle-mediated protein trafficking in hepatocytes by undefined mechanisms. In this study, the effects of long- and short-term ethanol exposure on vesicle movements were measured in isolated hepatocytes, and alterations in the function of the microtubule-associated motor enzymes dynamin, kinesin, and dynein, which are believed to support the transport and/or budding of vesicles along microtubules, were tested. METHODS: Vesicular movements in isolated hepatocytes exposed to short- and long-term ethanol treatment were measured. Motor adenosine triphosphatase activities and their association with specific membrane organelles were assessed in response to long-term administration of ethanol in vivo or acetaldehyde in vitro. RESULTS: Hepatocytes exposed to short- or long-term ethanol treatment showed a significant reduction in the number of motile vesicles. No alterations in the levels of motor messenger RNA, protein, or enzymatic activity were observed. Interestingly, ethanol had no effect on the association of dynein and kinesin with membranes, whereas there was a significant increase in the amount of dynamin associated specifically with Golgi membranes. CONCLUSIONS: Long- and short-term ethanol exposure markedly reduces hepatocellular vesicle transport by a mechanism apparently independent of any alteration in the enzymatic activity of molecular motors, possibly involving a change in the function of dynamin.

Acetaldehyde↗
PubMed1997

The structural basis for the specificity of pyridinylimidazole inhibitors of p38 MAP kinase.

BACKGROUND: The p38 mitogen-activated protein (MAP) kinase regulates signal transduction in response to environmental stress. Pyridinylimidazole compounds are specific inhibitors of p38 MAP kinase that block the production of the cytokines interleukin-1beta and tumor necrosis factor alpha, and they are effective in animal models of arthritis, bone resorption and endotoxin shock. These compounds have been useful probes for studying the physiological functions of the p38-mediated MAP kinase pathway. RESULTS: We report the crystal structure of a novel pyridinylimidazole compound complexed with p38 MAP kinase, and we demonstrate that this compound binds to the same site on the kinase as does ATP. Mutagenesis showed that a single residue difference between p38 MAP kinase and other MAP kinases is sufficient to confer selectivity among pyridinylimidazole compounds. CONCLUSIONS: Our results reveal how pyridinylimidazole compounds are potent and selective inhibitors of p38 MAP kinase but not other MAP kinases. It should now be possible to design other specific inhibitors of activated p38 MAP kinase using the structure of the nonphosphorylated enzyme.

Adenosine Triphosphate↗
PubMed1997

APPSw transgenic mice develop age-related A beta deposits and neuropil abnormalities, but no neuronal loss in CA1.

The recent availability of transgenic mouse models of Alzheimer disease has allowed direct in vivo assessment of the molecular and neuropathological effects of cerebral amyloid deposition. We examined 16-month-old Tg(HuAPP695. K670N-M671L)2576 mice expressing human APP K670N-M671L (APPSw), which have amyloid deposition and behavioral deficits by 11 months of age. Transgene expression is predominantly neuronal, and results in amyloid deposits, comparable to human senile plaques, at terminal zones of transgene positive neurons in cortical and limbic regions. Amyloid deposits were associated with prominent gliosis and neuritic dystrophy, without neuronal loss in CA1, loss of synaptophysin immunoreactivity in the hippocampal dentate gyrus, or loss of messenger RNA for neuronal synaptic, cytoskeletal, or metabolic proteins. We conclude that A beta is not acutely neurotoxic, but can disrupt neuronal processes and provoke an inflammatory response.

Aging↗
PubMed1997

Polynucleotide modulation of the protease, nucleoside triphosphatase, and helicase activities of a hepatitis C virus NS3-NS4A complex isolated from transfected COS cells.

The hepatitis C virus (HCV) nonstructural 3 protein (NS3) is a 70-kDa multifunctional enzyme with three known catalytic activities segregated in two somewhat independent domains. The essential machinery of a serine protease is localized in the N-terminal one-third of the protein, and nucleoside triphosphatase (NTPase) and helicase activities reside in the remaining C-terminal region. NS4A is a 54-residue protein expressed immediately downstream of NS3 in the viral polyprotein, and a central stretch of hydrophobic residues in NS4A form an integral structural component of the NS3 serine protease domain. There is no evidence to suggest that the two domains of NS3 are separated by proteolytic processing in vivo. This may reflect economical packaging of essential viral replicative components, but it could also mean that there is functional interdependence between the two domains. In this study, a full-length NS3-NS4A complex was isolated after expression and autoprocessing in transiently transfected COS cells. The protein was used to examine the effects of polynucleotides on the NTPase, helicase, and protease activities. Unlike the previously reported behavior of a separately expressed NS3 helicase domain, the full NS3-NS4A complex demonstrated optimal NTPase activity between pH 7.5 and 8.5. All three NS3-NS4A activities were modulated by polynucleotides, with poly(U) having the most remarkable effect. These findings suggest that the domains within NS3 may influence the activity of one another and that the interplay of HCV genomic elements may regulate the enzyme activities of this complex HCV replicase component.

Acid Anhydride Hydrolases↗
PubMed1997

The hepatitis C virus NS4A protein: interactions with the NS4B and NS5A proteins.

Hepatitis C virus encodes a large polyprotein precursor that is proteolytically processed into at least 10 distinct products, in the order NH2-C-E1-E2-p7-NS2-NS3-NS4A-NS4B-NS5A-NS5B -COOH. A serine proteinase encoded in the N-terminal 181 residues of the NS3 nonstructural protein is responsible for cleavage at four sites (3/4A, 4A/4B, 4B/5A, and 5A/5B) in the nonstructural region. NS4A, a 54-residue nonstructural protein which forms a stable complex with the NS3 proteinase, is required as a cofactor for cleavage at the 3/4A and 4B/5A sites and enhances processing at the 4A/4B and 5A/5B sites. Recently reported crystal structures demonstrated that NS4A forms an integral part of the NS3 serine proteinase. In this report, we present evidence that NS4A forms a nonionic-detergent-stable complex with the NS4B5A polyprotein substrate, which may explain the requirement of NS4A for the 4B/5A cleavage. Isoleucine-29 of NS4A, which has been previously shown to be essential for its proteinase cofactor activity and formation of the NS3 complex, was found to be important for the interaction between NS4A and the NS4B5A substrate. In addition, two more hydrophobic residues in the NS4A central region (valine-23 and isoleucine-25) were also shown to be essential for the cofactor activity and for the interaction with either the NS3 proteinase or the NS4B5A polyprotein substrate. Finally, the possible mechanisms by which these viral proteins interact with each other are discussed.

Animals↗
PubMed1997

Two novel mutations in phenylalanine hydroxylase gene and in vitro expression analysis on mutation Arg252Gln.

We report novel mutations in exon 7 of human phenylalanine hydroxylase (PAH) gene of phenylketonuria (PKU) in southern Chinese, analysed by using PCR-DGGE (denaturing gradient gel electrophoresis), solid phase DNA sequencing and in vitro expression. One of the 2 novel mutations, IVS6nt-1, is an intron-exon junctional mutation which results a splicing defect in mRNA. Arg252Gln is another novel mutation with residual PAH activity only 24% compared to wild type in in vitro mutagenesis and expression in Cos-1 cell. Other 3 known mutations and polymorphism including Arg241Cys, Arg243Gln and Val245Val (GTG to GTA) together with these novel mutations composed the mutational profile of exon 7 in the PAH gene of PKUs in this populations.

Exons↗
PubMed1996

Correlative memory deficits, Abeta elevation, and amyloid plaques in transgenic mice.

Transgenic mice overexpressing the 695-amino acid isoform of human Alzheimer beta-amyloid (Abeta) precursor protein containing a Lys670 --> Asn, Met671 --> Leu mutation had normal learning and memory in spatial reference and alternation tasks at 3 months of age but showed impairment by 9 to 10 months of age. A fivefold increase in Abeta(1-40) and a 14-fold increase in Abeta(1-42/43) accompanied the appearance of these behavioral deficits. Numerous Abeta plaques that stained with Congo red dye were present in cortical and limbic structures of mice with elevated amounts of Abeta. The correlative appearance of behavioral, biochemical, and pathological abnormalities reminiscent of Alzheimer's disease in these transgenic mice suggests new opportunities for exploring the pathophysiology and neurobiology of this disease.

Aging↗