Biomedical subjects

V K Wong

Publications and source records attributed to V K Wong.

At least 19 recordsLinked to original sources

PubMed2004

Achieving 99.9% proton spin-flip efficiency at higher energy with a small RF dipole.

We recently used a new ferrite rf dipole to study spin flipping of a 2.1 GeV/c vertically polarized proton beam stored in the COSY Cooler Synchrotron in Jülich, Germany. We swept the rf dipole's frequency through an rf-induced spin resonance to flip the beam's polarization direction. After determining the resonance's frequency, we varied the frequency range, frequency ramp time, and number of flips. At the rf dipole's maximum strength and optimum frequency range and ramp time, we measured a spin-flip efficiency of 99.92+/-0.04%. This result, along with a similar 0.49 GeV/c IUCF result, indicates that, due to the Lorentz invariance of an rf dipole's transverse integralBdl and the weak energy dependence of its spin-resonance strength, an only 35% stronger rf dipole should allow efficient spin flipping in the 100 GeV BNL RHIC Collider or even the 7 TeV CERN Large Hadron Collider.

Journal Article↗

PubMed2003

First spin flipping of a stored spin-1 polarized beam.

We recently studied spin flipping of a 270 MeV vertically polarized deuteron beam stored in the Indiana University Cyclotron Facility Cooler Ring. We adiabatically swept an rf solenoid's frequency through an rf-induced spin resonance and observed its effect on the deuterons' vector and tensor polarizations. After optimizing the resonance crossing rate and maximizing the solenoid's voltage, we measured a vector spin-flip efficiency of 94.2%+/-0.3%. We also found striking behavior of the spin-1 tensor polarization.

Journal Article↗

PubMed2003

The use of alefacept in the treatment of psoriasis.

Alefacept (AMEVIVE or LFA#TIP, Biogen) is the newest effective systemic therapy for chronic plaque psoriasis and was approved by the US FDA in January 2003. Clinical studies have shown that alefacept, given via weekly IM or IV injections for 12 weeks, was well tolerated, with no reported serious adverse events. Most significantly, it was found that alefacept provides a long-lasting remittive effect. These findings support the use of alefacept as a viable treatment of psoriasis, without the toxicities associated with some of the current systemic treatments available.

Adjuvants, Immunologic↗

PubMed2001

99.6% spin-flip efficiency in the presence of a strong Siberian snake.

We recently studied the spin-flipping efficiency of an rf-dipole magnet using a 120-MeV horizontally polarized proton beam stored in the Indiana University Cyclotron Facility Cooler Ring, which contained a nearly full Siberian snake. We flipped the spin by ramping the rf dipole's frequency through an rf-induced depolarizing resonance. By adiabatically turning on the rf dipole, we minimized the beam loss. After optimizing the frequency ramp parameters, we used 100 multiple spin flips to measure a spin-flip efficiency of 99.63+/-0.05%. This result indicates that spin flipping should be possible in very-high-energy polarized storage rings, where Siberian snakes are certainly needed and only dipole rf-flipper magnets are practical.

Journal Article↗

PubMed2001

Transcriptional activity of the promoter region of rat frizzled-related protein gene.

Frizzled-related protein (Frp) is a new family of secreted proteins involved in tumorigenesis and Wnt-signaling pathway. Previous study has shown that rat Frp (rFrp) gene was found to be differentially expressed in Rat 6 fibroblast cell line overexpressing p53(val135) (R6#13-8). The rFrp gene was otherwise silent in normal parental Rat 6 cells. To elucidate the molecular basis of the transcriptional activation of rFrp, we have isolated and analyzed a 2-kilobase pair promoter region of the rFrp gene. Mapping of transcription initiation sites of rFrp showed the existence of multiple initiation sites. Transfection studies of serial deletion constructs in both Rat 6 and CHOK1 cell lines revealed that the region from -202 to -144 contains cis-acting elements essential for the efficient transcription of rFrp. This work provides a transcriptional regulation basis for Frp and gives insight into its implication in tumorigenesis.

Amino Acid Sequence↗

PubMed2000

Immunogenicity of a Haemophilus influenzae type b-tetanus toxoid conjugate vaccine when mixed with a diphtheria-tetanus-acellular pertussis-hepatitis B combination vaccine.

BACKGROUND: Combination vaccines are urgently needed to reduce the number of injections given to young children. The aim of the study was to evaluate the safety and immunogenicity of a combination vaccine that contains diphtheria and tetanus toxoids and acellular pertussis antigens (DTaP), recombinant hepatitis B surface antigen (HepB) and Haemophilus influenzae type b (Hib) polysaccharide conjugated to tetanus toxoid (PRP-T). METHODS: Four hundred five infants were randomized equally to three groups and immunized at 2, 4 and 6 months of age with: (1) DTaP/HepB vaccine used to reconstitute lyophilized PRP-T vaccine and administered as a single injection; (2) DTaP/HepB vaccine and PRP-T vaccine administered as two separate injections; or (3) DTaP, HepB and PRP-T vaccines administered as three separate injections. Safety was closely monitored, and blood specimens were obtained to assess antibody responses to each vaccine antigen. RESULTS: All study vaccines were well-tolerated, and the rates of systemic and injection site reactions were similar between groups. After the third dose the geometric mean antibody concentrations to Hib were significantly lower in subjects in Group 1 (1.63 microg/ml) compared with subjects in Groups 2 and 3 (6.26 and 6.15 microg/ml, respectively; P < 0.0001). Subjects with antibody concentrations <1.0 microg/ml after the third dose responded well to a booster dose of Hib conjugate vaccine given at 11 to 15 months of age (41 of 44 with anti-PRP > or = 1.0 microg/ml). Differences between groups for antibody responses to the other vaccine components were not clinically significant. CONCLUSIONS: Infants given a combined DTaP/ HepB/PRP-T vaccine experienced a significantly lower antibody response to the PRP-T component than infants given PRP-T vaccine as a separate injection. However, the immune response to a booster dose of Hib conjugate vaccine indicated the presence of immunologic memory.

Antibodies, Bacterial↗

PubMed1997

Bilateral Candida parapsilosis endophthalmitis.

We describe a patient with bilateral, delayed endophthalmitis who underwent bilateral pars plana vitrectomy, total capsulectomy, intraocular lens exchange, intravitreal injection of amphotericin B, and oral fluconazole therapy. The long-term inflammation resolved, and vitreous cultures from both eyes yielded Candida parapsilosis. Histopathologic examination revealed sequestered yeast forms in the capsular bags.

Aged↗

PubMed1997

Retinal venous occlusive disease.

Occlusions of the retinal venous system are the second most common retinal vascular disease after diabetic retinopathy. Patients present with sudden vision loss or may be asymptomatic. Retinal vein occlusions are classified into branch or central occlusions. Laser photocoagulation and vitreoretinal surgical techniques are used to treat the complications of macular edema, neovascularization, vitreous hemorrhage and retinal detachment.

Aged↗

PubMed1996

Safety and immunogenicity of a serogroups A/C Neisseria meningitidis oligosaccharide-protein conjugate vaccine in young children. A randomized controlled trial.

OBJECTIVE: To assess the safety and immunogenicity of a bivalent serogroups A/C meningococcal oligosaccharide-protein conjugate vaccine compared with the licensed meningococcal polysaccharide vaccine. DESIGN: Randomized controlled trial. STUDY POPULATION: Ninety healthy 18- to 24-month-old children who were seen at a southern California Kaiser Permanente clinic. INTERVENTIONS: Vaccination with either the meningococcal conjugate vaccine (at 1 of 2 dosages) or the polysaccharide vaccine, with 2 doses given 2 months apart. MAIN OUTCOME MEASUREMENTS: Immune response to each vaccine dose as determined by measurement of serogroup-specific total antibodies by enzyme-linked immunosorbent assay (ELISA) and by assessment of serum bactericidal activity. RESULTS: Both vaccines appeared to be safe, and nearly all children responded with greater than 4-fold increases in antibody levels. The 2 dosages of the conjugate vaccine induced similar antibody responses; therefore, the data for the 2 conjugate vaccine groups were combined. Following 2 doses, ELISA antibody levels against group C meningococcus were significantly higher in conjugate vaccine recipients than in polysaccharide vaccine recipients (16.66 microg/mL vs. 8.31 microgm/mL; P<.001), but antibody levels against group A were not significantly different 22.75 microg/mL vs 21.24 microg/mL; P=.70). The serum bactericidal assays showed striking differences between the conjugate and polysaccharide vaccine groups. Geometric mean serum bactericidal titers were significantly higher in conjugate vaccine recipients (755.6 vs 37.6 for group A, P<.001; 3197.9 vs 11.4 for group C, P<.001). CONCLUSIONS: The immune response induced by this meningococcal oligosaccharide-protein conjugate vaccine was qualitatively different from that induced by the polysaccharide vaccine, and the antibodies it elicited provided greater functional activity.

Antibodies, Bacterial↗

PubMed1996

Children hospitalized for varicella: a prevaccine review.

OBJECTIVES: To describe varicella complications in healthy and previously ill children hospitalized for varicella and to explore trends in group A beta-hemolytic streptococcus complications of varicella. METHODS: A retrospective record review of children hospitalized for varicella between January 1, 1990, and March 31, 1994, was conducted in nine large acute care hospitals in Los Angeles County, California. RESULTS: We identified 574 children hospitalized for varicella in study hospitals during the 4.25-year study period (estimated risk of hospitalization, approximately 1 in 550 cases of varicella); 53% of the children were healthy before the onset of varicella and 47% were previously ill with underlying cancers or other chronic illnesses. Children were hospitalized for treatment of complications (n = 427, 74%) or for prophylactic antiviral therapy or observation (n = 147, 26%). Systems involved in complications included skin/soft tissue (45%), neurologic (18%), respiratory (14%), gastrointestinal (10%), and hematologic, renal, or hepatic (8% or less). The mean age of children with skin/soft tissue infections was 2.7 years (range < 1 to 16 years) compared with 4.7 years (< 1 to 18 years) for other complications. Children with skin/soft tissue and neurologic complications were more often previously healthy (p < 0.05), whereas those with respiratory complications were more often previously ill (p < 0.001). Hospitalizations for skin/soft tissue infections increased during the study period. The proportion of complications as a result of group A beta-hemolytic streptococcus infection increased from 4.7% before 1993 to 12.2% for the remainder of the study period (p = 0.02). CONCLUSIONS: Prior health status was predictive of the type of complications experienced by children with varicella requiring hospitalization. Our data suggest a recent increase in skin/soft tissue complications of varicella requiring hospitalization and an increase in the proportion of complications related to group A beta-hemolytic streptococcus. Wide-scale vaccine use should reverse this trend and reduce the overall impact of varicella on both healthy and previously ill children.

Adolescent↗

PubMed1996

Comparative safety and immunogenicity of two recombinant hepatitis B vaccines given to infants at two, four and six months of age.

OBJECTIVES: To evaluate the relative safety and immunogenicity of the two recombinant hepatitis B vaccines licensed in the United States with doses recommended for routine immunization of low risk infants and a schedule that corresponds with routine pediatric visits. METHODS: Healthy infants were immunized at 2, 4 and 6 months of age with hepatitis B vaccine manufactured by either SmithKline Beecham (Engerix-B, 10 micrograms/dose, n = 228) or Merck and Co. (Recombivax HB, 2.5 micrograms/dose, n = 200). Adverse reactions were ascertained by parental reports and interviews and by review of medical records. Antibody concentrations to hepatitis B surface antigen (anti-HBs) were measured in sequential serum specimens by enzyme immunoassay. RESULTS: Adverse reactions were mild and the rates were not significantly different between the two groups. After the first and second doses the rates of seropositivity (> or = 10 mIU/ml) and seroprotection (> or = 10 mIU/ml) were significantly higher in infants given SmithKline Beecham vaccine (P < 0.01). After the second and third doses infants given SmithKline Beecham vaccine also had significantly higher geometric mean anti-HBs concentrations compared with those given Merck vaccine (348.0 mIU/ml vs. 66.9 and 1914.8 mIU/ml vs. 514.8 mIU/ml, respectively, P < 0.001). Nevertheless after the third dose 99% of infants in both vaccine groups achieved seroprotective antibody concentrations. CONCLUSIONS: Both recombinant hepatitis B vaccines were safe and immunogenic when administered concurrently with other pediatric vaccines at 2, 4 and 6 months of age, but earlier protective responses were observed with the SmithKline Beecham vaccine than with the Merck vaccine.

Consumer Product Safety↗

PubMed1995

Effect of neonatal immunization with diphtheria and tetanus toxoids on antibody responses to Haemophilus influenzae type b conjugate vaccines.

We randomly assigned 150 newborn infants to receive diphtheria and tetanus toxoids (DT) or Hib oligosaccharide conjugate (HbOC) at birth to determine whether exposure to the Haemophilus influenzae type b (Hib) conjugate vaccines' carrier proteins would enhance immune responses to subsequent administrations of HbOC or PRP-tetanus toxoid conjugate (PRP-T) at 2, 4, and 6 months of age. Their antibody responses were compared with those of 100 children immunized with HbOC or PRP-T beginning at 2 months of age. No serious adverse reactions were associated with neonatal vaccination. Administration of HbOC at birth did not lead to earlier or higher antibody levels. Newborn immunization with DT did not prime children for enhanced antibody responses. Moreover, Hib antibody levels were lower in DT-primed children than in children immunized beginning at 2 months of age. Diphtheria antibody levels, but not tetanus antibody levels, were also lower in children immunized with DT at birth. We conclude that neonatal immunization with Hib conjugate vaccines is not a means to provide earlier protection against invasive Hib disease. Newborn DT administration does not enhance subsequent antibody responses to Hib conjugate vaccines, and may lead to suppression of Hib and diphtheria antibody responses.

Antibodies, Bacterial↗

PubMed1995

Enhanced antibody responses in infants given different sequences of heterogeneous Haemophilus influenzae type b conjugate vaccines.

To evaluate the safety and immunogenicity of differing sequences of heterogeneous Haemophilus influenzae type b (Hib) conjugate vaccines, we randomly assigned 300 infants to one of six vaccination schedules. At 2, 4, and 6 months of age, subjects were given single or heterogeneous vaccines: Hib polysaccharide (PRP) conjugated to mutant diphtheria toxin (HbOC), PRP conjugated to outer-membrane protein of Neisseria meningitidis (PRP-OMP), or PRP conjugated to tetanus toxoid (PRP-T). No serious reactions were attributable to immunization with heterogeneous vaccines, and there were few significant differences in the rates of minor adverse reactions among groups. PRP-OMP was the only vaccine that induced an antibody response after the first dose, but significant booster responses were not seen after the second and third doses. Subjects given PRP-T vaccine responded well after two doses, but three doses of HbOC vaccine were needed for an equivalent antibody response. All the Hib vaccine schedules evaluated were immunogenic, and schedules initiated by PRP-OMP vaccine at 2 months of age, followed by two doses of either HbOC or PRP-T vaccine at 4 and 6 months of age, induced the highest antibody levels after each dose. Such schedules may be the best for protecting infants and children who are at greatest risk of having invasive Hib disease, such as American Indian children.

Aging↗

PubMed1994