Biomedical subjects

A Wong

Publications and source records attributed to A Wong.

At least 55 records · Page 3Linked to original sources

PubMed2001

Lipid, sugar and liposaccharide based delivery systems.

Although there are formidable barriers to the oral delivery of biologically active drugs, considerable progress in the field has been made, using both physical and chemical strategies of absorption enhancement. A possible method to enhance oral absorption is to exploit the phenomenon of lipophilic modification and mono and oligosaccharide conjugation. Depending on the uptake mechanism targeted, different modifications can be employed. To target passive diffusion, lipid modification has been used, whereas the targeting of sugar transport systems has been achieved through drugs conjugated with sugars. These drug delivery units can be specifically tailored to transport a wide variety of poorly absorbed drugs through the skin, and across the barriers that normally inhibit absorption from the gut or into the brain. The delivery system can be conjugated to the drug in such a way as to release the active compound after it has been absorbed (i.e. the drug becomes a prodrug), or to form a biologically stable and active molecule (i.e. the conjugate becomes a new drug moiety). Examples where lipid, sugar and lipid-sugar conjugates have resulted in enhanced drug delivery will be highlighted in this review.

Animals↗

PubMed2001

Cyclosporine and FK506 differentially regulate the sarcolemmal Na(+)-K(+) pump.

Cyclosporine A (CsA) and FK506, important immunosuppressants, have been shown to inhibit the enzymatic equivalent of the Na(+)-K(+) pump (Na(+), K(+)-ATPase) in renal tissue. A similar effect in the heart may contribute to the adverse effects of these agents that include calcification, contractile dysfunction, and altered calcium handling. However, inhibition of the pump has not been demonstrated in cardiac myocytes. We isolated single ventricular myocytes from control rabbits and from rabbits administered CsA or FK506 for 1 week. Na(+)-K(+) pump current (I(p)) was measured using the whole-cell patch-clamp technique. When patch pipettes contained Na(+) in a concentration ([Na](pip)) near physiological intracellular levels mean I(p) of cardiac myocytes from rabbits with serum CsA levels within the therapeutic range was significantly lower than mean I(p) of cardiac myocytes from controls. Treatment had no effect on I(p) measured using a [Na](pip) expected to nearly saturate intracellular binding sites. The CsA-induced inhibition of I(p) was dependent on the K(+) concentration in pipette solutions. Mean I(p) in myocytes from rabbits with serum levels of FK506 within the therapeutic range was similar to mean I(p) in myocytes from controls, whereas FK506 in a dose inducing serum levels severalfold above the therapeutic range caused significant pump inhibition. Using ion-sensitive microelectrodes we showed the intracellular Na(+) activity in papillary muscles isolated from rabbits treated with CsA was significantly higher than in papillary muscles from control rabbits, indicating that CsA causes pump inhibition in intact myocytes with a physiological intracellular milieu.

Animals↗

PubMed2001

Toxicity and Efficacy of Concurrent Gemcitabine and Radiotherapy for Locally Advanced Pancreatic Cancer.

Gemcitabine has been demonstrated to be a potentradiosensitizer in the laboratory and in the clinic (1-7)and has proven clinical systemic activity to pancreaticcancer. Responses to systemic gemcitabine inpatients with metastatic pancreatic adenocarcinomahave been documented in phase I, phase II, and phaseIII clinical settings (8,9). Moreover, a recent randomizedtrial of gemcitabine vs 5-FU as first-linetherapy in patients with advanced pancreatic adenocarcinomademonstrated a modest median survivalbenefit (4.41 vs 5.65 mo,p= 0.0025) for those patientswho received gemcitabine compared to those whoreceived 5-FU (10). In addition, gemcitabine wasshown to improve cancer-related symptoms and performancestatus as assessed by a quantitative clinicalbenefit scale in both untreated and previouslytreated patients with metastatic adenocarcinoma ofthe pancreas (10,11). Based on these data, the FDAapproved gemcitabine as a first-line agent for patientswith advanced adenocarcinoma of the pancreas.

Journal Article↗

PubMed2000

Increased cyclooxygenase-2 and 5-lipoxygenase activating protein expression in peritoneal macrophages during ovalbumin immunization of mice and cytosolic phospholipase A(2) activation after antigen challenge.

The present study investigates phenotypic and functional differentiation of peritoneal macrophages during ovalbumin-induced subcutaneous immunization of mice. For the first time we show that, in mouse peritoneal macrophages, ovalbumin immunization induces an increase in cyclooxygenase-2 (COX-2) and 5-lipoxygenase activating protein (FLAP) expression whereas it inhibits cytosolic phospholipase A(2) (cPLA2) expression. The study of arachidonic acid (AA) metabolism in peritoneal macrophages from control (cPM) and ovalbumin-immunized (iPM) mice shows that the reduced cPLA2 expression is correlated to a reduced basal AA metabolism, but is not a limiting factor for the opsonized zymosan-, PMA-, or A23187-triggered AA metabolism. We also show that in vitro ovalbumin challenge induces, only in iPM, cPLA2 activation through phosphorylation of serine residues, via a mechanism involving MAP kinases, and through increased intracellular calcium concentrations, leading to eicosanoid production. In parallel, we report that, in peritoneal macrophages, ovalbumin immunization induces the expression of CD23, the low affinity receptor for IgEs known for its involvement in allergic diseases. Thus, the modified expression of the enzymes involved in AA metabolism and the difference of response of cPM and iPM toward the antigen are important elements to understand the underlying mechanisms of ovalbumin-induced allergic responses.

5-Lipoxygenase-Activating Proteins↗

PubMed2000

Phylogenetic relationships of xenodontine snakes inferred from 12S and 16S ribosomal RNA sequences.

The phylogenetic relationships of xenodontine snakes are inferred from sequence analyses of portions of two mitochondrial genes (12S and 16S ribosomal RNA) in 85 species. Although support values for most of the basal nodes are low, the general pattern of cladogenesis observed is congruent with many independent molecular, morphological, and geographical data. The monophyly of xenodontines and the basal position of North American xenodontines in comparison with Neotropical xenodontines are favored, suggesting an Asian-North American origin of xenodontines. West Indian xenodontines (including endemic genera and members of the genus Alsophis) appear to form a monophyletic group belonging to the South American clade. Their mid-Cenozoic origin by dispersal using ocean currents is supported. Within South American mainland xenodontines, the tribes Hydropsini, Pseudoboini, and Xenodontini are monophyletic. Finally, our results suggest that some morphological and ecological traits concerning maxillary dentition, macrohabitat use, and foraging strategy have appeared multiple times during the evolution of xenodontine snakes.

Animals↗

PubMed2000

Crosslinking of alpha-synuclein by advanced glycation endproducts--an early pathophysiological step in Lewy body formation?

An excess of reactive carbonyl compounds (carbonyl stress) and their reaction products, advanced glycation endproducts (AGEs), are thought to play a decisive role in the pathogenesis of neurodegenerative disorders and Parkinson's disease (PD) in particular. Accumulation of AGEs in various intracellular pathological hallmarks of PD, such as Lewy bodies, densely crosslinked intracellular protein deposits formed from neurofilament components and alpha-synuclein, have already been described in patients in advanced stages of the disease. There is, however, no indication of the involvement of AGE-induced crosslinking of alpha-synuclein in very early stages of the disease. In this study, we observed that AGEs and alpha-synuclein are similarly distributed in very early Lewy bodies in the human brain in cases with incidental Lewy body disease. These cases might be viewed as pre-Parkinson patients, i.e. patients who came for autopsy before the possible development of clinical signs of PD. AGEs are both markers of transition metal induced oxidative stress as well as, inducers of protein crosslinking and free radical formation by chemical and cellular processes. Thus, it is likely that AGE promoted formation of Lewy bodies reflects very early causative changes rather than late epiphenomenons of PD.

Aged↗

PubMed2000

Sensitivity analysis and other improvements to tailored combinatorial library design

"Tailoring" combinatorial libraries was developed several years ago as a very general and intuitive method to design diverse compound collections while controlling the profile of other pharmaceutically relevant properties. The candidate substituents were assigned to "categorical bins" according to their properties, and successive steps of D-optimal design were performed to generate diverse substituent sets consistent with required membership quotas from each bin. This serial algorithm was expedient to implement from existing D-optimal design codes, but was order-dependent and did not generally locate the very best possible design. A new "parallel" Fedorov search algorithm has now been implemented that can find the most diverse property-tailored design. An ambiguous mass penalty has been added, whereby most duplicate masses can be eliminated with little loss of library diversity. Sensitivity analysis has also been added to quantitatively explore the diversity trade-offs due to increasing or decreasing each specific kind of bias.

Journal Article↗

PubMed2000

Single vs twice daily G-CSF dose for peripheral blood stem cells harvest in normal donors and children with non-malignant diseases.

The optimal dose and schedule of G-CSF for mobilization of peripheral blood stem cells (PBSC) is not well defined. G-CSF mobilization was performed in a group of healthy donors and paediatric patients for autologous back-up before receiving allogeneic stem cell transplant. Seventeen consecutive subjects who received G-CSF at 5 microg/kg/dose twice daily (group A) were compared with a historical control group of 25 subjects who received a single daily dose of 10 microg/kg/day G-CSF (group B). Double blood volume apheresis for PBSC collection was started on day 5. G-CSF was continued and apheresis repeated until the targeted CD34+ cell dose was achieved. Both groups were comparable for sex, age, body weight and reason for PBSC collection. Over two-thirds of the subjects in both groups were less than 16 years of age. The G-CSF priming and apheresis were well tolerated. When the first day apheresis products were analyzed, group A resulted in significantly higher yield of total nucleated cells (5.91 vs 3.92 x 108/kg, P = 0. 013), mononuclear cells (5.73 vs 3.92 x 108/kg, P = 0.017), CD34+ cells (2.80 vs 1.69 x 106/kg, P = 0.049) and colony-forming units (107 vs 54 x 104/kg, P = 0.010) as compared with group B. We conclude that the two dose schedule is more efficient in mobilizing PBSC in normal donors and children with non-malignant diseases. This approach may reduce the number of aphereses required and thus reduce the transplant cost.

Adolescent↗

PubMed2000

Expression of human Wiskott-Aldrich syndrome protein in patients' cells leads to partial correction of a phenotypic abnormality of cell surface glycoproteins.

The Wiskott-Aldrich syndrome (WAS) is an uncommon X-linked recessive disease characterized by thrombocytopenia, eczema and immunodeficiency. The biochemical defect of this disorder primarily affects cells derived from bone marrow. To understand better the molecular mechanisms underlying this disease and to evaluate the possibility of correcting the genetic defects in hematopoietic cells, a Moloney murine leukemia virus (MoMLV)- based retroviral vector carrying a functional Wiskott-Aldrich syndrome protein (WASp) cDNA driven by an SV40 promoter (LNS-WASp) was constructed. A packaging cell line containing this vector produced a stable level of WAS protein and maintained a high titer of viral output. Epstein-Barr virus (EBV)-transformed B lymphoblastoid cell lines (B-LCL) from WAS patients, which lack expression of the WAS protein, were transduced by the LNS-WASp retroviral vector and showed expression of WASp by Western blot. Analysis of the O-glycan pattern on cell surface glycoproteins from WAS patients' B-LCL showed an altered glycosylation pattern, due to increased activity of beta-1, 6-N-acetylglucosaminyltransferase (C2GnT). Transduction by the retroviral vector carrying the functional WASp cDNA partially restored the abnormal glycosylation pattern, and was accompanied by a decreasing C2GnT activity. These findings imply a functional linkage between the WAS protein and the expression of the glycosyltransferase involved in the O-glycosylation, and also suggest a potential gene therapy via transferring a functional WASp cDNA into hematopoietic cells for Wiskott-Aldrich syndrome. Gene Therapy (2000) 7, 314-320.

Cells, Cultured↗

PubMed2000

Pooling of prognostic studies in cancer of the pancreatic head and periampullary region: the Triple-P study. Triple-P study group.

OBJECTIVE: Development of a prognostic tool for patients with unresectable pancreatic cancer to distinguish between with low or high probabilities of survival 3 to 9 months after diagnosis. DESIGN: Data about individual patients from five studies were pooled. A multivariate proportional hazards model with time-dependent covariates was developed, including age, sex, and metastases. An extended model was developed on a subset of patients, including weight loss, pain, and jaundice at diagnosis. SETTING: Multicentre study, The Netherlands, Norway, USA, UK, and Canada. SUBJECTS: 1020 patients with unresectable pancreatic cancer. MAIN OUTCOME MEASURES: Prediction of prognosis. RESULTS: Patients with metastases, pain, or weight loss at diagnosis had a significantly poorer prognosis than the others. Older men had a worse prognosis than younger men, while older women had a better prognosis than younger ones. Patients with jaundice had a relatively good prognosis. Differences in survival among the studies were incorporated in a prognostic score chart. CONCLUSION: The prognostic score chart can be used to select patients with relatively low expectation of survival for endoscopic palliation, and patients with relatively high expectation for surgical palliation.

Aged↗

PubMed2000

Sensitivity of FRDA lymphoblasts to salts of transition metal ions.

Friedreich's ataxia (FRDA) is an autosomal recessive neurodegenerative disease resulting from decreased expression of the nuclear-encoded mitochondrial protein, frataxin. FRDA patients have characteristic iron deposits and dysfunction of mitochondrial enzymes in the heart. Inactivation of the frataxin homologue in yeast causes dysregulation of both mitochondrial iron levels and iron export. Previously, we have observed sensitivity of FRDA fibroblasts to FeCl3 and hydrogen peroxide, results consistent with the hypothesis that FRDA cells may experience increased Fenton chemistry. To determine whether the sensitivity of FRDA cells to transition metal ions is a general or specific property, we have compared the sensitivity of lymphoblasts from FRDA patients and healthy controls to the transition metal salts CoCl2, CuSO4 FeCl3 FeSO4, MnCl2, and ZnCl2. FRDA lymphoblasts were significantly more sensitive to FeCl3 and MnCl2 than control cells. However, there were no significant differences observed in sensitivity to CoCl2, CuSO4, FeSO4 and ZnCl2 in the concentration ranges studied. Thus, the sensitivity of FRDA lymphoblasts exposed to transition metals appears to be specific, and could be relevant to the pathophysiological mechanism, which is discussed.

Blotting, Western↗

PubMed2000

Meta-analysis of treatment termination rates among rheumatoid arthritis patients receiving disease-modifying anti-rheumatic drugs.

OBJECTIVE: To summarize the evidence on treatment withdrawal rates reported in observational studies and randomized controlled trials (RCTs) of methotrexate (MTX), parenteral gold (GST), sulphasalazine (SSZ) and hydroxychloroquine (HCQ) among patients with rheumatoid arthritis (RA). METHODS: Two independent Medline searches were used to retrieve relevant studies published between 1966 and 1997. Those which disclosed information on the number of patients withdrawing from the drug were retained. Cumulative probabilities of survival on treatment were then computed using actuarial survival estimates, and differences were tested using log-rank, Wilcoxon and Cox proportional hazards tests. RESULTS: A total of 159 studies provided withdrawal information, and the numbers of patients who withdrew, in general or because of inefficacy or toxicity, could be abstracted from 110 studies contributing 142 treatment arms (MTX, 48; GST, 56; SSZ, 22; HCQ, 16). Data for HCQ were available only up to 24 months, but combined percentages of patients estimated to have continued MTX, GST or SSZ, respectively, for 60 months were 36, 23 and 22% when all failures were considered, 75, 73 and 53% when withdrawals due to lack of efficacy alone were considered, and 65, 36 and 48% when only withdrawals due to toxicity were taken into account. The Cox proportional hazards test performed on all withdrawals, after adjusting for year of publication and type of study, revealed that patients remained on MTX significantly longer than they did on the other three agents; however, the patients stayed significantly longer on GST than MTX when withdrawals for inefficacy were analysed separately. No significant differences in withdrawal rates were noted between observational studies and RCTs. CONCLUSION: Patients with RA stay significantly longer on MTX than on other disease-modifying anti-rheumatic drugs. Higher withdrawal rates among those given GST are mainly due to high toxicity, whereas the majority of withdrawals from SSZ and HCQ result from lack of efficacy. Withdrawal rates in observational studies are similar to those reported in RCTs.

Antirheumatic Agents↗

PubMed2000

Reverse transcriptase-PCR analysis of bacterial rRNA for detection and characterization of bacterial species in arthritis synovial tissue.

Onset of rheumatoid arthritis (RA) is widely believed to be preceded by exposure to some environmental trigger such as bacterial infectious agents. The influence of bacteria on RA disease onset or pathology has to date been controversial, due to inconsistencies between groups in the report of bacterial species isolated from RA disease tissue. Using a modified technique of reverse transcriptase-PCR amplification, we have detected bacterial rRNA in the synovial tissue of late-stage RA and non-RA arthritis controls. This may be suggestive of the presence of live bacteria. Sequencing of cloned complementary rDNA (crDNA) products revealed a number of bacterial sequences in joint tissue from each patient, and from these analyses a comprehensive profile of the organisms present was compiled. This revealed a number of different organisms in each patient, some of which are common to both RA and non-RA controls and are probably opportunistic colonizers of previously diseased tissue and others which are unique species. These latter organisms may be candidates for a specific role in disease pathology and require further investigation to exclude them as causative agents in the complex bacterial millieu. In addition, many of the detected bacterial species have not been identified previously from synovial tissue or fluid from arthritis patients. These may not be easily cultivable, since they were not revealed in previous studies using conventional in vitro bacterial culture methods. In situ hybridization analyses have revealed the joint-associated bacterial rRNA to be both intra- and extracellular. The role of viable bacteria or their nucleic acids as triggers in disease onset or pathology in either RA or non-RA arthritis controls is unclear and requires further investigation.

Adult↗

PubMed2000

In situ production of gamma interferon, interleukin-4, and tumor necrosis factor alpha mRNA in human lung tuberculous granulomas.

Human tuberculous granulomas from five adults undergoing surgery for hemoptysis were analyzed by nonradioactive in situ hybridization for tumor necrosis factor alpha (TNF-alpha), gamma interferon (IFN-gamma), and interleukin-4 (IL-4) gene expression. All of the patients produced TNF-alpha mRNA. Three patients stained positive for both IFN-gamma and IL-4 mRNA; the other two stained positive for IFN-gamma but not IL-4 mRNA. Heterogeneity between the granulomas was observed in those patients staining positive for both IFN-gamma and IL-4 mRNA; these patients exhibited granulomas having IFN-gamma and not IL-4 mRNA as well as granulomas positive for both cytokine mRNAs. There was no evidence of caseation in these granulomas, and the cytokine patterns may represent events in the evolution of the granuloma. However, in those granulomas exhibiting caseous necrosis, very little IFN-gamma or IL-4 mRNA was observed, implying that progression of the granuloma is accompanied by a down regulation of T-cell responses. TNF-alpha mRNA expression was highest in patients with both IFN-gamma and IL-4 mRNA. Populations of CD68 positive macrophage-like cells within the granulomas produce mRNA for TNF-alpha, IFN-gamma, and IL-4. This implies that macrophages within the tuberculous granuloma may not be dependent on T-cell cytokines for modulation of their function but may be able to regulate their own activation state and that of the surrounding T cells. These findings have implications on the delivery of immunotherapies to patients with tuberculosis.

Adult↗

PubMed2000

Validating a screening questionnaire for parkinsonism in Australia.

Parkinson's disease is a common neurodegenerative disorder in elderly people. Epidemiological studies of the disease can be labour intensive. A two phase design including a screening questionnaire as the first phase has become a popular method in prevalence studies of Parkinson's disease. Such a design has many advantages including less work for assessing physicians and enhanced recruitment of people to be screened. However, its wider application may be questioned because validation has been limited to samples that are drawn from hospitals (or clinics) and may be inappropriate for a community setting. This study assesses whether validating screening questionnaire by using a hospital sample yields the same result as a community based sample. Furthermore, it seeks to establish whether the screening instrument can be simplified to involve less questions. The findings show that some of the questions used in the screening phase yield different responses when comparing a hospital group with a community group. This study also provides a simplified model of questions that may be relevant for screening in the community setting.

Aged↗

PubMed2000

Use of transcranial Doppler ultrasound to predict outcome in patients with intracranial large-artery occlusive disease.

BACKGROUND AND PURPOSE: Intracranial large-artery occlusive disease is the predominant vascular lesion found in stroke patients of Asian, African, and Hispanic ancestry, making it numerically perhaps the most common vascular cause of stroke in the world. Relatively little is known about the clinical significance of finding such lesions. We investigate whether the presence and the extent of these vascular lesions help predict outcome after stroke. METHODS: On the basis of transcranial Doppler of the intracranial arteries with supplementary duplex ultrasound of the carotid arteries, we determined the number of occlusive arteries in the craniocervical circulation of consecutive patients who were hospitalized for acute cerebral ischemia. Patients were followed for 6 months for further vascular events (including transient ischemic attack, stroke, and acute coronary syndrome) or death. RESULTS: Among 705 consecutive Chinese patients studied, occlusive arteries were found in 345 patients (49%): 258 patients (37%) had intracranial lesions only, 71 (10%) had both extracranial and intracranial lesions, and 16 (2.3%) had extracranial lesions only. Sixty-three (18%) of the 345 patients with occlusive arteries and 35 (9.7%) of the 360 patients without occlusive arteries had further vascular event or death within 6 months. The risk of vascular events or death increased rapidly with rising numbers of occlusive arteries, after adjustment for vascular risk factors and stroke severity (adjusted odds ratio [OR] 1.25 per occlusive artery, 95% CI 1.12 to 1.39). Other independent risk factors included age (OR 1.03 per year of age, 95% CI 1.01 to 1.05) and atrial fibrillation (OR 3.00, 95% CI 1.40 to 6.69). CONCLUSIONS: In patients with predominantly intracranial large-artery occlusive disease, the presence and the total number of occlusive arteries in the craniocervical circulation predict further vascular events or death within 6 months after stroke. Transcranial Doppler ultrasound is an important investigation for the evaluation of patients with stroke in populations at risk of intracranial atherosclerotic disease.

Arterial Occlusive Diseases↗

PubMed2000

Consumerism in the financial services industry: lessons for managed care.

Managed care today is being shaped by the emergence of a savvier, better informed health care consumer. Facing a strikingly similar consumer movement over the past two decades, the banking industry experienced a market transformation that holds important lessons for managed care. Nontraditional entrants in the financial services industry, offering focused "monoline" products and services closely analogous to "carve-out" providers in health care, targeted rising consumer demands and stronger preferences. Banks in time answered these formidable new competitive forces with innovative consolidation and globalization strategies. The most successful initiatives in healthcare, as in banking, will focus on satisfying the consumer's hunger for information, improved levels of service, and enhanced outcomes. Managed care plans may play a lead role in accelerating the impact of consumerism by bridging the disconnect between patients and their purchasing decisions.

Commerce↗

PubMed2000

Seroprevalence of cytomegalovirus, toxoplasma and parvovirus in pregnancy.

AIM OF STUDY: The aim of our study was to determine the seroprevalence of cytomegalovirus (CMV), toxoplasma and parvovirus infection in our local antenatal population, and to see the effects, if any, of age, race, parity and nationality on its seroprevalence. METHODOLOGY: The sera of 120 consecutive antenatal women seen in KK Women's and Children's Hospital between the period of October 1997 and March 1998 were screened for cytomegalovirus (CMV) IgG, toxoplasma IgG and parvovirus B19 IgG and IgM. An antibody titer greater than 1:32 was regarded as positive. RESULTS: A total of 87.0% of patients were tested seropositive for CMV IgG, 17.2% seropositive for toxoplasma IgG and 30.0% seropositive for parvovirus IgG. There seemed to be a trend of increasing seropositivity with age in all three groups, however only parovirus B19 reached statistical significance. The incidence of all three infections were higher among the Malays, Indians and other races compared to the Chinese. CONCLUSION: CMV is endemic in our population and hence the most common infection. Toxoplasmosis and parvovirus is relatively low in our population but this implies that a large proportion of our antenatal women are still susceptible to these infections. Prevention of congenital CMV, toxoplasmosis and parvovirus infection is mainly by educating the antenatal population.

Adult↗