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Biomedical subjects

C Chun

Publications and source records attributed to C Chun.

14 recordsLinked to original sources
PubMed2005

Trivalent inactivated influenza vaccine safety in children: assessing the contribution of telephone encounters.

We assessed the contribution of telephone medical care encounters to surveillance of adverse events (AE) following trivalent influenza vaccination in children age 6 months to 17 years. We used retrospective, self-controlled, case-series analysis to estimate adverse event incidence rate ratios for post-vaccination risk intervals relative to 15-28 days prior to vaccination. We confirmed possible vaccination reactions by medical record abstraction. Detection of 10 of 20 elevated incidence rate ratios required telephone data. We conclude that telephone encounters substantially contribute to the detection of possible influenza vaccination reactions, primarily local injection site and systemic reactions.

Adolescent↗
PubMed2005

Incidence of herpes zoster, 1997-2002.

We estimated age-specific herpes zoster (HZ) incidence rates in the Kaiser Permanente Northwest Health Plan (KPNW) during 1997-2002 and tested for secular trends and differences between residents of two states with different varicella vaccine coverage rates. The cumulative proportions of 2-year-olds vaccinated increased from 35% in 1997 to 85% in 2002 in Oregon, and from 25% in 1997 to 82% in 2002 in Washington. Age-specific HZ incidence rates in KPNW during 1997-2002 were compared with published rates in the Harvard Community Health Plan (HCHP) during 1990-1992. The overall HZ incidence rate in KPNW during 1997-2002 (369/100,000 person-years) was slightly higher than HCHP's 1990-1992 rate when adjusted for age differences. For children 6-14 years old, KPNW's rates (182 for females, 123 for males) were more than three times HCHP's rates (54 for females, 39 for males). This increase appears to be associated with increased exposure of children to oral corticosteroids. The percentage of KPNW children exposed to oral corticosteroids increased from 2.2% in 1991 to 3.6% in 2002. Oregon residents had slightly higher steroid exposure rates during 1997-2002 than Washington residents. There were significant increases in HZ incidence rates in Oregon and Washington during 1997-2002 among children aged 10-17 years, associated with increased exposure to oral steroids.

Adolescent↗
PubMed2001

Pancreatic cancer cell-derived vascular endothelial growth factor is biologically active in vitro and enhances tumorigenicity in vivo.

Vascular endothelial growth factor (VEGF) is a potent angiogenic stimulator that acts by binding to high-affinity transmembrane receptors. Although both VEGF and its receptors are overexpressed in human pancreatic ductal adenocarcinoma (PDAC), this malignancy is not generally considered to be highly vascular. It is not known, therefore, whether the abundance of VEGF in PDAC is biologically relevant. To address this issue, we measured the angiogenic effects of pancreatic cancer cell-derived VEGF in an in vitro endothelial cell proliferation assay and characterized the consequences of suppressing VEGF expression on pancreatic tumor growth in an athymic nude mouse model. We found that human pancreatic cancer cell lines secrete large quantities of biologically active VEGF into conditioned medium (CM). Stable transfection of an anti-sense VEGF(189) (AS-VEGF(189)) expression construct into PANC-1 pancreatic cancer cells resulted in decreased VEGF expression and secretion, a decreased capacity of the resultant CM to enhance endothelial cell proliferation and a significant attenuation of tumor cell proliferation in vitro. Furthermore, when injected into athymic nude mice, AS-VEGF(189)-expressing cells exhibited an 80% decrease in tumor growth compared with control cells. These results support the hypothesis that VEGF promotes pancreatic cancer growth in vivo and suggest that anti-VEGF therapy may be useful in the treatment of this disease.

Animals↗
PubMed1999

Identification of a Drosophila brain-gut peptide related to the neuropeptide Y family.

A neuropeptide F (NPF) was isolated from the fruit fly, Drosophila mellanogaster, based on a radioimmunoassay for a gut peptide from the corn earworm, Helicoverpa zea. A partial sequence was obtained from the fly peptide, and a genomic sequence coding for NPF was cloned after inverse polymerase chain reaction and shown to exist as a single genomic copy. The encoded, putative prepropeptide can be processed into an amidated NPF with 36 residues that is related to invertebrate NPF's and the neuropeptide Y family of vertebrates. In situ hybridization and immunocytochemistry showed that Drosophila NPF was expressed in the brain and midgut of fly larvae and adults.

Amino Acid Sequence↗
PubMed1998

Intracanopy lighting of cowpea canopies in controlled environments.

Traditional designs for plant-growth lighting in space life support systems irradiate tops of closed foliar canopies while canopy understories are light limited. "Intracanopy lighting," a technique whereby plants are allowed to grow up and around multiple layers of low-intensity lamps that irradiate interior portions of canopies, can potentially enhance productivity while reducing overall energy consumption. Intracanopy lighting of cowpea (Vigna unguiculata L. Walp) was optimized by varying stand densities and lining growth compartments with light-scattering or reflective films. Yield rates using intracanopy lighting were less than those obtained with traditional lighting strategies. However, yield efficiencies and energetic conversion efficiencies, parameters that put edible yield in terms of inedible biomass, energetic, spatial, and temporal penalties, indicate intracanopy lighting is more efficient in crop production. Single-leaf photosynthetic rates indicate all leaves participate in net carbon gain regardless of age and position within a canopy.

Biomass↗
PubMed1997

Dynamic optimization of CELSS crop photosynthetic rate by computer-assisted feedback control.

A procedure for dynamic optimization of net photosynthetic rate (Pn) for crop production in Controlled Ecological Life-Support Systems (CELSS) was developed using leaf lettuce as a model crop. Canopy Pn was measured in real time and fed back for environmental control. Setpoints of photosynthetic photon flux (PPF) and CO2 concentration for each hour of the crop-growth cycle were decided by computer to reach a targeted Pn each day. Decision making was based on empirical mathematical models combined with rule sets developed from recent experimental data. Comparisons showed that dynamic control resulted in better yield per unit energy input to the growth system than did static control. With comparable productivity parameters and potential for significant energy savings, dynamic control strategies will contribute greatly to the sustainability of space-deployed CELSS.

Air Conditioning↗
PubMed1997

Environmental modification of yield and nutrient composition of 'Waldmann's Green' leaf lettuce.

Leaf number, dry weight, and nutrient composition of Lactuca sativa L. cv. Waldmann's Green leaves were compared following 9 days of treatment in a controlled environment room under various combinations of photosynthetic photon flux (PPF:350 vs 800 micromoles m-2 s-1), atmospheric CO2 level (ambient vs 1500 micromoles mol-1), and single-strength (1X:15 mM) vs double-strength (2X:30 mM) nitrogen (N) as NO3- alone or as NH4(+) + NO3- (1:5 molar ratio). CO2 enrichment greatly enhanced leaf number under all PPF and N conditions, but increased leaf dry weight only at high PPF. Conditions favoring high photosynthesis enhanced leaf starch content 3-fold, and protein content increased as much as 64% with 2X NH4(+)+NO3-. Free sugar content was 6 to 9% of leaf dry weight for all treatment combinations, while fat was 1.5 to 3.5%. Ash content varied from 15 to 20% of leaf dry weight. Modified controlled environments can be used to enhance the nutritional content as well as the yield of crops to be used for life support in space-deployed, self-sustaining human habitats. Leaf lettuce is a useful model crop for demonstrating the potential of nutritional value added by environmental manipulation.

Biomass↗
PubMed1996

Dynamic control of photosynthetic photon flux for lettuce production in CELSS.

A new dynamic control of photosynthetic photon flux (PPF) was tested using lettuce canopies growing in the Minitron II plant-growth/canopy gas-exchange system. Canopy photosynthetic rates (Pn) were measured in real time and fedback for further environment control. Pn can be manipulated by changing PPF, which is a good environmental parameter for dynamic control of crop production in a Controlled Ecological Life-Support Systems CELSS. Decision making that combines empirical mathematical models with rule sets developed from recent experimental data was tested. With comparable yield indices and potential for energy savings, dynamic control strategies will contribute greatly to the sustainability of space-deployed CELSS.

Biomass↗
PubMed1987

Combined radiotherapy and chemotherapy with bleomycin and methotrexate for advanced inoperable head and neck cancer: update of a Northern California Oncology Group randomized trial.

Between 1978 and 1984, the Northern California Oncology Group (NCOG) conducted a randomized trial to study the efficacy of combined radiotherapy (RT) and chemotherapy (CT) for stage III or IV inoperable head and neck cancer. One hundred four patients were randomized to receive: (1) RT alone, or (2) RT plus CT. RT consisted of 7,000 cGy to the involved areas and 5,000 cGy to uninvolved neck at 180 cGy/fraction, five fractions/wk. CT consisted of bleomycin, 5 U intravenously (IV), twice weekly during RT, followed by bleomycin, 15 U IV, and methotrexate, 25 mg/m2 IV weekly for 16 weeks after completion of RT. Fifty-one patients in the RT alone group and 45 in the combined treatment group were evaluable. The local-regional complete response (CR) rate was 45% v 67% (P = .056); the 2-year local-regional control rate, including salvage surgery, was 26% v 64% (P = .001); and the incidence of distant metastasis was 24% v 38% (P greater than .25), for the RT alone and RT plus CT groups, respectively. The relapse-free survival curves were significantly different (P = .041), favoring the combined treatment. However, the survival curves were not significantly different (P = .16). Patient compliance to maintenance CT was poor. Bleomycin significantly increased the acute radiation mucositis, although the difference in late normal tissue toxicity was not statistically significant. Thus, bleomycin and concurrent RT produced a more favorable CR rate, local-regional control rate, and relapse-free survival, but the difference in survival was not statistically significant.

Adult↗
PubMed1982

Influence of the original disease, race, and center on the outcome of kidney transplantation.

The low graft survival rate in black recipients (36 +/- 2% at 1 year) as compared with the graft survival rate in white recipients (48 +/- 1%) might be secondary to a higher incidence of vascular lesions, inducing hypertensive disease, in blacks than in whites. The relative frequency of malignant hypertension in black recipients was six times that of white recipients, and recipients with malignant hypertension had a significant lower graft survival rate (43 +/- 2%) than recipients with glomerulonephritis (54 +/- 1%). In addition, patients with vascular lesions (diabetes, malignant hypertension, and glomerulonephritis) showed significantly lower graft survival rates in black than in white recipients, in contrast to patients with primary tubular or interstitial lesions (polycystic kidneys and pyelonephritis), who showed similar graft survival rates in blacks and whites. Only a small fraction of this racial effect could be traced back to the higher incidence of Lewis-negative phenotypes in black recipients and a similar beneficial effect of transfusions, on graft survival, was observed in both black and white recipients. The effects of graft survival of age (6%), race (9%), and transfusions (18%) were significant in good (A) and poor (B) centers. No overlap between A and B centers was observed for any of these three parameters when analyzed separately. However, when the cumulative effects of these three risk parameters were analyzed together a partial overlap appeared, i.e., higher graft survival rates were observed in low-risk recipients that received transplants in B centers than in high-risk recipients that received transplants in A centers. Consequently, the selection of the recipient may play a role in the overall results of different transplantation units, leading to their classification into A or B centers, but cannot explain all of the differences between A and B centers.

Actuarial Analysis↗
PubMed1980

Combined effects of HLA matching and age in renal transplantation.

Recipient age and matching for the HLA-A and B antigens each influence the graft survival rate of cadaver kidney transplants by approximately 10%. These two factors are cumulative and have a combined effect of nearly 20%. Thus, other factors that have a relatively weak influence on graft success may have a combined effect that makes their clinical consideration highly relevant.

Adolescent↗
PubMed1980

The Lewis system and kidney transplantation.

A significant effect of Lewis antigens on cadaver kidney graft survival was found in 1,300 North American transplants. Lewis-negative recipients had a graft survival rate that was 8% lower than that of Lewis-positive recipients (P = 0.05). This effect of Lewis antigens was enhanced in patients at a high failure risk as determined by age, race, or transplant center. In patients older than 30 years, the effect of Lewis was 14% (P = 0.07), in non-Caucasians 12% (P = 0.07), in all grafts performed at centers with less than 50% overall 1-year graft survival 12% (P = 0.03), and in non-Caucasians that received transplants in centers with less than 50% overall graft survival it was 18% (p = 0.01). These data confirm previous results on the role of Lewis as a histocompatibility system in renal transplantation; furthermore, they demonstrate that the influence of Lewis is larger in patients at high risk.

Adult↗