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Biomedical subjects

A Mak

Publications and source records attributed to A Mak.

At least 19 recordsLinked to original sources
PubMed2006

Estimating vaccine effectiveness against laboratory-confirmed influenza using a sentinel physician network: results from the 2005-2006 season of dual A and B vaccine mismatch in Canada.

INTRODUCTION: We report a case-control design using a sentinel physician network to estimate vaccine effectiveness (VE) against laboratory-confirmed, medically attended influenza (LC-MAI) and provide results for the 2005-2006 season of dual A and B vaccine mismatch in Canada. METHODS: Participants were patients >or=5 years of age presenting with influenza-like illness (ILI) to a sentinel physician in British Columbia, Canada between November 1, 2005 and April 30, 2006. Cases were participants in whom influenza was identified; controls tested negative for influenza A and B by PCR, R-mix and culture. Isolates were characterized by gene-sequencing and hemagglutination-inhibition (HI) assays. Odds ratios (OR) for LC-MAI in vaccinated versus non-vaccinated persons were derived with adjustment for age and chronic conditions. VE was estimated as [1-OR (vaccinated/unvaccinated)]. RESULTS: The sample included 442 patient visits: median age was 26 years, 10% were >or=65 years, 15% had a chronic condition and 22% received the 2005-2006 trivalent inactivated influenza vaccine >or=2 weeks before ILI onset. Two hundred and six participants were positive for influenza; 107 (52%) had influenza A/H3N2 and 99 (48%) had influenza B/Victoria lineage. Gene sequencing identified mutations away from the vaccine strain at key antigenic binding sites of the hemagglutinin (HA) protein of H3N2 isolates; the neuraminidase (NA) protein was conserved. Based on HI assays, three-quarters of influenza A and all B isolates were mismatched to the 2005-2006 vaccine. Point estimates for VE against LC-MAI were in the range of 50 to 70% for both types of influenza. CONCLUSION: 2005-2006 was the third consecutive season of vaccine mismatch based on varying HA for the A/H3N2 component and the third also for the B component since 2001. Vaccine mismatch resulted in diminished VE but substantial cross-protection. More timely detection of drift variants through gene sequencing of isolates facilitates interpretation of VE results. Since it may be more antigenically conserved, the vaccine content and contribution of NA to overall VE should be further evaluated for both A and B components. Infrastructure for real-time epidemiologic assessment of vaccine performance is important annually and in preparation for a pandemic.

Adolescent↗
PubMed2006

Adrenomedullin--a potential disease activity marker and suppressor of nephritis activity in systemic lupus erythematosus.

OBJECTIVES: To investigate whether plasma adrenomedullin (AM) level is elevated in lupus nephritis and to examine if plasma AM level is correlated with systemic lupus erythematosus (SLE) disease activity and severity of lupus nephritis after multivariate adjustment. METHODS: Consecutive SLE patients and healthy volunteers of age >/=16 were recruited from the rheumatology clinics of two hospitals in Hong Kong. SLE patients with nephritis fulfilled the American College of Rheumatology criteria for renal involvement and had percutaneous renal biopsy performed. Subjects were divided into three groups: (i) SLE patients with nephritis, (ii) SLE patients without nephritis and (iii) normal controls. The demographic and clinical variables were compared between these groups of patients and plasma AM level was determined by radioimmunoassay. Factors associated with plasma AM level were explored by regression analysis with adjustment of confounding factors. RESULTS: Sixty SLE patients (39 with nephritis and 21 without) and 23 normal subjects were studied. The plasma AM level of SLE patients was significantly higher than that of normal controls. SLE patients with nephritis had significantly higher plasma AM level than those without nephritis and normal controls (P<0.001). In regression analysis, proteinuria was negatively associated with plasma AM level (P=0.006) whereas SLE disease activity index was positively associated with plasma AM level after multivariate adjustment (P=0.002). CONCLUSIONS: Plasma AM is elevated in lupus nephritis, which correlates with lupus disease activity. It is negatively associated with urine protein excretion although it is unrelated to the type of renal pathology per se. Plasma AM may play a role to suppress the activity of lupus nephritis.

Adrenomedullin↗
PubMed2005

Outcome of protein-losing gastroenteropathy in systemic lupus erythematosus treated with prednisolone and azathioprine.

OBJECTIVES: To report the efficacy of prednisolone and azathioprine (AZA) in the treatment of systemic lupus erythematosus (SLE)-related protein-losing gastroenteropathy (PLGE). METHODS: Between 1995 and 2002, 16 consecutive patients with SLE-related PLGE were treated with a regimen consisting of high-dose prednisolone (0.8-1 mg/kg/day for 6 weeks, then tapered to < or =10 mg/day) and AZA (2 mg/kg/day). Protein leakage from the gastrointestinal tract was confirmed by 99mTc-labelled human serum albumin scintigraphy and significant urinary loss of protein was excluded. Clinical response at 6 months of therapy was assessed and patients were followed for relapse of PLGE. RESULTS: Clinical characteristics of our patients at the time of PLGE were: age 36.2 +/- 8.7 (s.d.) yr; female:male ratio 15 : 1; mean SLE duration 29.6 +/- 65 months. Twelve patients had PLGE as the initial presentation of SLE. Fifteen (94%) patients had concomitant activity in other organs. All patients presented with oedema and eight patients (50%) had non-bloody diarrhoea. The mean serum albumin level was 22.8 +/- 5.7 g/dl. Protein leakage was at the small bowel in 11 (69%) patients and the large bowel in 5 (31%) patients. At 6 months of therapy, 14 (88%) patients had complete clinical response, 1 (6%) patient responded partially and 1 patient (6%) was treatment-refractory. Patients who responded were maintained on low-dose prednisolone (7.8 +/- 6.1 mg/day) and AZA (56.3 +/- 37 mg/day). Over a mean follow-up of 57.5 months, 1 (6%) patient had relapse of PLGE which responded to augmentation of prednisolone dosage. No patients developed alternative gastrointestinal diagnoses. Corticosteroid-induced psychosis, AZA-induced pancytopenia and herpes zoster occurred in three patients. CONCLUSION: PLGE is an uncommon manifestation of SLE. Treatment with a combination of prednisolone and AZA is effective and well tolerated.

Administration, Oral↗
PubMed2005

Bone mineral density in postmenopausal Chinese patients with systemic lupus erythematosus.

The objective was to study the bone mineral density (BMD) and its clinical determinants in a cohort of postmenopausal patients with systemic lupus erythematosus (SLE). All postmenopausal SLE patients receiving long term glucocorticoids were identified from our medical clinics. Lumbar and femoral BMDs were measured by dual X-ray absorptiometry. Clinical determinants of BMD were studied by simple and multiple linear regression. Variables evaluated were: age, body mass index, parity, duration of menopause, smoking and alcohol drinking, duration of SLE and steroid treatment, cumulative prednisone dose, clinical and serological profile, disease activity, damage index and the use of medications. In total, 34 patients were studied. The mean age was 52.9+/-4.9 years and the median duration of SLE was 75.5 months. The mean duration of menopause was 5.2+/-3.9 years and the daily maintenance dose of prednisone was 4.0+/-2.5 mg/day. At the lumbar spine, 33% of the patients were osteopenic and 48% were osteoporotic. Two patients had thoracic and lumbar vertebral compression fractures. At the nondominant femoral neck, 74% of patients were osteopenic but only 3% was osteoporotic. In a multivariate model, the current or past use of hydroxychloroquine (HCQ) was associated with a higher spinal BMD. The presence of anti-Sm and the absence of anti-Ro were associated with a higher femoral BMD. It was concluded that osteoporosis, especially at the spine, is a common and serious problem in postmenopausal Chinese SLE patients receiving long term glucocorticoid therapy. Active intervention should be considered. The protective role of HCQ has to be confirmed with further studies.

Asian People↗
PubMed2005

Mycophenolate mofetil for refractory haemolytic anemia in systemic lupus erythematosus.

Mycophenolate mofetil (MMF) has been increasingly used in patients with systemic lupus erythematosus (SLE). While most information concentrates on lupus nephritis, its efficacy in nonrenal manifestations of SLE has not been systematically studied. We describe the successful use of MMF in a patient with SLE-related hemolytic anemia that was refractory to cyclophosphamide, pulse methylprednisolone, intravenous immunoglobulin and cyclosporine. The mechanisms of action of MMF are briefly reviewed.

Adult↗
PubMed2003

Calcium-independent contraction and sensitization of airway smooth muscle by p21-activated protein kinase.

In Triton-skinned phasic ileal smooth muscle, constitutively active recombinant p21-activated kinase (PAK3) has been shown to induce Ca(2+)-independent contraction, which is accompanied by phosphorylation of caldesmon and desmin (Van Eyk JE, Arrell DK, Foster DB, Strauss JD, Heinonen TY, Furmaniak-Kazmierczak E, Cote GP, and Mak AS. J Biol Chem 273: 23433-23439, 1998). In the present study, we investigated whether PAK has a broad impact on smooth muscle in general by testing the hypothesis that PAK induces Ca(2+)-independent contractions and/or Ca(2+) sensitization in tonic airway smooth muscle and that the process is mediated via phosphorylation of caldesmon. In the absence of Ca(2+) (pCa > 9), constitutively active glutathione-S-transferase-murine PAK3 (GST-mPAK3) caused force generation of Triton-skinned canine tracheal smooth muscle (TSM) fibers to approximately 40% of the maximal force generated by Ca(2+) at pCa 4.4. In addition, GST-mPAK3 enhanced Ca(2+) sensitivity of contraction by increasing force generation by 80% at intermediate Ca(2+) concentrations (pCa 6.2), whereas it had no effect at pCa 4.4. Catalytically inactive GST-mPAK3(K297R) had no effect on force production. Using antibody against one of the PAK-phosphorylated sites (Ser(657)) on caldesmon, we showed that a basal level of phosphorylation of caldesmon occurs at this site in skinned TSM and that PAK-induced contraction was accompanied by a significant increase in the level of phosphorylation. Western blot analyses show that PAK1 is the predominant PAK isoform expressed in murine, rat, canine, and porcine TSM. We conclude that PAK causes Ca(2+)-independent contractions and produces Ca(2+) sensitization of skinned phasic and tonic smooth muscle, which involves an incremental increase in caldesmon phosphorylation.

Animals↗
PubMed2002

Impact of donor arm skin disinfection on the bacterial contamination rate of platelet concentrates.

BACKGROUND AND OBJECTIVES: Despite improved methods for detecting bacterial contamination of blood products, bacterial sepsis remains a significant risk in blood transfusion. This study was undertaken to investigate whether adopting a different skin disinfection protocol could reduce the rate of bacterial contamination of platelet concentrates. MATERIALS AND METHODS: Two skin disinfection protocols were consecutively used in the routine blood collection setting during two 10-month periods: 0.5% cetrimide/0.05% chlorhexidine solution followed by 70% isopropyl alcohol (first 10-month time-period); and 10% povidone-iodine followed by 70% isopropyl alcohol (second 10-month time-period). The rates of bacterial contamination of platelet concentrates were monitored by using a surveillance programme described previously. RESULTS: The overall bacterial contamination rate in the first time-period was 0.072%. After introduction of the povidone-iodine and isopropyl alcohol protocol, the bacterial contamination rate decreased to 0.042% (relative risk reduction: -0.42; 95% confidence interval, -0.12 to -0.61, P= 0.009). There were no differences in the types of micro-organisms identified (P = 0.7). CONCLUSIONS: Skin disinfection by povidone-iodine and isopropyl alcohol is more effective than that by cetrimide/chorhexidine and isopropyl alcohol in reducing venepuncture-associated contamination of platelet concentrates by skin flora. Our data indicate that the disinfection protocol should be used on a routine basis and such implementation should translate into a significant improvement in blood safety to patients receiving platelet transfusion.

2-Propanol↗
PubMed2002

Three patients with lead poisoning following use of a Chinese herbal pill.

We report on three patients with lead poisoning following use of the Chinese herbal pill Bao ning dan, prepared by the same traditional Chinese medicine practitioner. The patients had varying degrees of exposure to Bao ning dan and different clinical manifestations. Blood lead concentrations did not correlate with clinical severity. Two patients received chelating therapy and blood lead concentrations subsequently rapidly decreased. One patient was managed conservatively and end-organ complications resolved gradually. With increasing use of traditional Chinese medicines, related adverse reactions are expected to become increasingly common. Practitioners of western medicine should remain alert to this possibility. A comprehensive drug review, including the use of herbal medicines, should form a routine part of medical history taking.

Adult↗
PubMed2001

G2/M arrest caused by actin disruption is a manifestation of the cell size checkpoint in fission yeast.

In budding yeast, actin disruption prevents nuclear division. This has been explained as activation of a morphogenesis checkpoint monitoring the integrity of the actin cytoskeleton. The checkpoint operates through inhibitory tyrosine phosphorylation of Cdc28, the budding yeast Cdc2 homolog. Wild-type Schizosaccharomyces pombe cells also arrest before mitosis after actin depolymerization. Oversized cells, however, enter mitosis uninhibited. We carried out a careful analysis of the kinetics of mitotic initiation after actin disruption in undersized and oversized cells. We show that an inability to reach the mitotic size threshold explains the arrest in smaller cells. Among the regulators that control the level of the inhibitory Cdc2-Tyr15 phosphorylation, the Cdc25 protein tyrosine phosphatase is required to link cell size monitoring to mitotic control. This represents a novel function of the Cdc25 phosphatase. Furthermore, we demonstrate that this cell size-monitoring system fulfills the formal criteria of a cell cycle checkpoint.

Actins↗
PubMed2000

Mechanical characterization of regenerated osseous tissue during callotasis and its related biological phenomenon.

The mechanical characteristics of the regenerated osseous tissue and osteoblastic activities during callotasis were studied using Chinese mountain goat as the animal model. Open osteotomy of the left tibiae was done in 24 goats. Distraction started 6 days after the operation with the rate of 1 mm per day for 4 weeks. The bone regeneration was monitored with serial X-ray films. The tension generated during distraction was measured with the strain gauges mounted on the distraction apparatus. The osteoblastic activities were monitored by measuring plasma bone specific alkaline phosphatase activity. The results showed that the average lengthening was 22.9 +/- 2.8 mm in each animal. The newly formed osseous tissue becomes stiffer during the course of distraction lengthening. The continuous evolution of the tensile behaviour of the newly formed osseous tissue correlates with the plasma bone specific alkaline phosphatase activities. The radiological appearance of a physis like structure took place at 12 mm lengthening. Its appearance corresponds to the changes in the tensile behaviour as well as the biological activities of the osteoblasts and may serve as a useful radiological marker in monitoring the process of callotasis in clinical practice.

Alkaline Phosphatase↗
PubMed2000

Experimental discordant hepatic xenotransplantation in the recipient with liver failure: implications for clinical bridging trials.

BACKGROUND: Clinical xenotransplantation might start with bridge-to-bridge trials. Situations where hyperacute rejection is avoided would provide opportunities for the initiation of bridging trials. Patients with liver failure have a diminished capacity to initiate antibody and complement-induced injury of xenogeneic endothelium. Hyperacute rejection of a liver xenograft manifests as a coagulopathy. We examined the ability of a recipient with liver failure to hyperacutely reject a liver xenograft in the dog-to-pig model in the immediate postoperative period. STUDY DESIGN: Liver failure in pigs was induced with galactosamine. Canine livers were transplanted into pigs with liver failure and into healthy pigs. The postoperative course was monitored for 1 hour for histologic changes in the xenograft, changes in platelet counts, and whole blood clotting with Sonoclot analysis. In vitro assays with pig serum and canine hepatic sinusoidal endothelial cells were used to assess the effect of liver failure on serum cytotoxicity and xenoreactive antibody levels. RESULTS: All untreated pig recipients of liver xenografts died from a coagulopathy. Recipients with liver failure manifested no signs of coagulopathy, and had minimal change in platelet counts or Sonoclot (Sienco Inc., Morrison, CO) tracings. Liver xenograft biopsies from recipients with liver failure showed no evidence of the tissue injury that characterized the biopsies of control recipients. Serum from pigs was less cytotoxic to the canine hepatic sinusoidal endothelium after induction of liver failure. The xenoreactive antibody levels and repertoire were similar in the pig serum before and after liver failure was induced. CH50 (total complement) levels were diminished in pigs after the induction of liver failure. CONCLUSIONS: Liver xenotransplantation used in bridging trials in recipients with liver failure might not face the barrier of hyperacute rejection.

Animals↗
PubMed1999

Mitotic separation of daughter cells in the human lymphoma B cell line Daudi involves L-selectin engagement and shedding.

BACKGROUND AND OBJECTIVE: A novel role for shedding of the surface molecule L-selectin has been proposed as an adjunctive phenomenon during cell detachment from marrow stroma or vessel endothelium. We wished to examine whether variations in expression of L-selectin on a lymphoma B cell line were linked to shedding. DESIGN AND METHODS: Mapping of L-selectin expression on the surface of Daudi lymphoma cells was performed by flow cytometry, fluorescence microscopy, and electron microscopy. Levels of shed L-selectin were evaluated by Western blotting of culture supernatants. Evaluation of cell cycle and proliferative activity was performed by flow cytometry. RESULTS: Large Daudi cells in S+G(2)/M phases were L-selectin positive, whereas small Daudi cells in G(0)/G(1) phase were L-selectin negative. During mitosis, L-selectin was distributed along the cleavage furrow, and gradually lost. Electron microscopy revealed that separating Daudi cells were negative for L-selectin on the entire surface, except minute aggregates of L-selectin within the cleavage furrow. Addition of agents known to interfere with the ligand-binding portion of L-selectin (sulfatides, MoAbs: Lam1.3 and TQ1) results in loss of L-selectin. Removal of L-selectin by digestion with chymotrypsin inhibits Daudi proliferation. The MoAb FMC46 did not interfere with proliferation. Proliferating Daudi cells produced large quantities of shed L-selectin. Inhibition of Daudi proliferation resulted in levels of shed L-selectin below the limit of detection. INTERPRETATION AND CONCLUSIONS: L-selectin is re-distributed on the cell surface of Daudi cells during the last phase of mitosis, in which plasma membrane invagination occurs between newly formed daughter cells. Shedding of L-selectin is involved in the cytokinesis of Daudi cells.

B-Lymphocytes↗
PubMed1996

Endoglin is a component of the transforming growth factor (TGF)-beta receptor complex of human pre-B leukemic cells.

Endoglin was first identified on a cell line derived from pre-B acute lymphoblastic leukemia. This 180-kDa homodimeric glycoprotein was then shown to be primarily expressed on endothelial cells and to bind the beta 1 and beta 3 isoforms of TGF-beta with high affinity. We now demonstrate that pre-B leukemic cells express a functional TGF-beta 1 receptor complex. The levels of mRNA for these receptors and for TGF-beta 1 were quantitated by PCR. HOON, G2, and NALM-6 cell lines express similar levels of mRNA for TGF-beta 1 and for TGF-beta receptor I (R-I) and receptor II (R-II). HOON cells express ten times more endoglin than G2 and NALM-6 cells, whereas all three cell lines have low levels of betaglycan relative to other cell types. The receptors were identified by affinity labeling with 125I-labeled TGF-beta 1, chemical cross-linking, and specific immunoprecipitation. Endoglin, R-II, and R-I were co-precipitated by Abs to either endoglin or R-II, indicating that these proteins are forming a receptor complex on leukemic cells; no betaglycan could be immunoprecipitated. The receptor complex is functional, as demonstrated by inhibition of proliferation of HOON cells (80%) and NALM-6 cells (60%) with 25 pM TGF-beta 1. Furthermore, the motility of HOON and NALM-6 cells on immobilized fibronectin, which appears to be alpha 4 beta 1-integrin mediated, was stimulated two- to threefold by TGF-beta 1. These results suggest that active TGF-beta 1 produced in the bone marrow microenvironment might stimulate the motility of normal pre-B cells and the peripheral dissemination of leukemic pre-B cells.

Activin Receptors, Type I↗
PubMed1995

Ectopic expression of human and feline CD9 in a human B cell line confers beta 1 integrin-dependent motility on fibronectin and laminin substrates and enhanced tyrosine phosphorylation.

Few molecules have been shown to confer cell motility. Although the motility-arresting properties of anti-CD9 monoclonal antibody (mAb) suggest the transmembrane 4 superfamily (TM4SF) member CD9 can induce a motorgenic signal, gene transfection studies have failed to confirm this hypothesis. We report here that ectopic expression of human CD9 (CD9h) and feline CD9 (CD9f) in the CD9-negative, poorly motile, human B cell line Raji dramatically enhances migration across fibronectin- and laminin-coated polycarbonate filters. Migration of Raji/CD9h and Raji/CD9f on either substrate was inhibited by the anti-CD9 mAb 50H.19 and by the anti-beta 1 integrin mAb AP-138. Migration of Raji/CD9h on laminin was potently inhibited by the anti-VLA-6 integrin mAb GoH3 and by the anti-VLA-4 integrin mAb 44H6, whereas migration of Raji/CD9h on fibronectin was inhibited only by mAb 44H6. Since CD9h-transfected Raji cells adhered to fibronectin as effectively as mock transfectants, expression of CD9 enhanced motility, but not adhesion. CD9-enhanced migration was inhibited by the protein tyrosine kinase inhibitor herbimycin A suggesting that tyrosine phosphorylation played a role in the generation of a motorgenic signal. Raji/CD9h transfectants adherent to fibronectin expressed 6-fold higher levels of phosphotyrosine than Raji. Raji/CD9f transfectants also phosphorylated proteins on tyrosine more effectively than Raji including a protein of 110 kDa which was phosphorylated on the motility-inducing substrates laminin and fibronectin, but not on bovine serum albumin. Our results support a role for CD9 in the amplification of a motorgenic signal in B cells involving beta 1 integrins and the activation of protein tyrosine kinases.

Animals↗
PubMed1993

The carboxy-terminal tail of the homeo domain protein alpha 2 is required for function with a second homeo domain protein.

The homeo domain protein alpha 2 from Saccharomyces cerevisiae has two roles in the a/alpha cell: With MCM1, alpha 2 turns off transcription of a-specific genes; with a1 (a second homeo domain protein), alpha 2 represses transcription of haploid-specific genes. From the carboxy-terminal side of the alpha 2 homeo domain extends an unstructured 22-amino-acid residue tail. In this paper we show that the carboxy-terminal tail of alpha 2 is required for formation of a stable a1/alpha 2-operator complex and is thus required for a1/alpha 2-mediated repression of transcription. In contrast, the tail is dispensable for alpha 2/MCM1-mediated repression. These results indicate that a short, unstructured tail mediates the interaction between two homeo domain proteins.

Base Sequence↗