Search PubMed⌕ Search

Biomedical subjects

K H Chu

Publications and source records attributed to K H Chu.

At least 37 records · Page 2Linked to original sources
PubMed2001

cDNA cloning and molecular identification of the major oyster allergen from the Pacific oyster Crassostrea gigas.

BACKGROUND: Shellfish is one of the most common food allergens. Despite the recent cloning and molecular identification of the major heat stable crustacean allergens in shrimp, lobster and crab, there have been no similar studies on molluscs to which a significant portion of populations allergic to shellfish are also hypersensitive. Recent biochemical evidence suggests that tropomyosin is also an allergen in molluscs, but data on the molecular cloning, nucleotide sequencing, expression and IgE binding to mollusc tropomyosin are lacking. OBJECTIVE: This study was undertaken to clone, identify and determine the primary structure of a major IgE-reactive mollusc allergen in oyster at the DNA and protein level. METHODS: We constructed an expression cDNA library from the Pacific oyster Crassostrea gigas. This library was screened for IgE binding clones using sera from 15 subjects with a well-documented history of type I hypersensitivity reactions to oysters. An IgE reactive clone was selected and sub-cloned into plasmids for nucleotide sequence determination and expression in E. coli. RESULTS: We identified a 1.3-kb cDNA designated as Cra g 1.03. Expression of Cra g 1.03 in plasmid vector pGEX produced a 59-kDa recombinant fusion protein reactive to the IgE antibodies from patients with oyster allergies but not non-allergic controls. Cra g 1.03 has an open reading frame of 233 amino acids and demonstrates marked similarity in amino acid composition and peptide sequence with mollusc and crustacean tropomyosins. Absorption of oyster allergic sera with Cra g 1.03 totally removed IgE reactivity to oyster extract. Moreover, absorption of allergic sera with recombinant shrimp tropomyosin (Met e 1), lobster tropomyosin (Pan s 1) and crab tropomyosin (Cha f 1) removed most of the IgE reactivity to Cra g 1.03. CONCLUSION: Cra g 1.03 is the first oyster allergen identified at the molecular level. Nucleotide and amino acid comparison shows that this protein is the oyster tropomyosin.

Allergens↗
PubMed1999

Evaluation of toxic effects of aeration and trichloroethylene oxidation on methanotrophic bacteria grown with different nitrogen sources.

In this study we evaluated specific and nonspecific toxic effects of aeration and trichloroethylene (TCE) oxidation on methanotrophic bacteria grown with different nitrogen sources (nitrate, ammonia, and molecular nitrogen). The specific toxic effects, exerted directly on soluble methane monooxygenase (sMMO), were evaluated by comparing changes in methane uptake rates and naphthalene oxidation rates following aeration and/or TCE oxidation. Nonspecific toxic effects, defined as general cellular damage, were examined by using a combination of epifluorescent cellular stains to measure viable cell numbers based on respiratory activity and measuring formate oxidation activities following aeration and TCE transformation. Our results suggest that aeration damages predominantly sMMO rather than other general cellular components, whereas TCE oxidation exerts a broad range of toxic effects that damage both specific and nonspecific cellular functions. TCE oxidation caused sMMO-catalyzed activity and respiratory activity to decrease linearly with the amount of substrate degraded. Severe TCE oxidation toxicity resulted in total cessation of the methane, naphthalene, and formate oxidation activities and a 95% decrease in the respiratory activity of methanotrophs. The failure of cells to recover even after 7 days of incubation with methane suggests that cellular recovery following severe TCE product toxicity is not always possible. Our evidence suggests that generation of greater amounts of sMMO per cell due to nitrogen fixation may be responsible for enhanced TCE oxidation activities of nitrogen-fixing methanotrophs rather than enzymatic protection mechanisms associated with the nitrogenase enzymes.

Ammonia↗
PubMed1999

Seafood allergy: tropomyosins and beyond.

Hypersensitive reactions to seafood is one of the most common food allergies. Despite years of intensive studies, the reasons why some people are allergic to seafood is still unclear. The growing demand for seafood and the subsequent increasing risk of seafood allergy in the population at large make it important to elucidate the molecular basis of seafood allergy and identify the seafood allergens at the molecular level. Here, we discuss the clinical symptoms, physiological mechanisms, current findings of the immunological and molecular basis of shellfish allergy as well as future directions for the prevention of shellfish allergy. Interestingly, identified seafood allergens belong to a group of muscle proteins, namely the parvalbumins in codfish and tropomyosin in crustaceans. In addition, there is strong immunological evidence that tropomyosin is a cross-reactive allergen among crustaceans and mollusks. The molecular cloning, expression and biochemical characterization of seafood allergens will continue to provide valuable tools in the further understanding of the mechanisms of seafood allergy as well as the future development of immunomodulation regimen.

Allergens↗
PubMed1998

Molecular and immunological characterization of shellfish allergens.

Shellfish (crustaceans and mollusks) have long been known as a common cause of allergic reactions to food. Like other food allergies, the allergic reactions to shellfish involve IgE-mediated Type I hypersensitivity. Biochemical and molecular studies have documented the major shrimp allergen is the muscle protein tropomyosin. Subsequent molecular cloning studies on lobsters and crabs have characterized this protein as the common allergen in crustaceans. There has also been strong immunological evidence that tropomyosin is a cross-reactive allergen among crustaceans and mollusks. This is further confirmed by recent studies on the identification of allergens in squid and abalone. The advances in the characterization of shellfish allergens will not only enhance our understanding on the physiological basis of shellfish allergy but also lay the groundwork for the development of diagnostic and therapeutic design in food allergies.

Allergens↗
PubMed1998

Identification and molecular characterization of Charybdis feriatus tropomyosin, the major crab allergen.

BACKGROUND: Crab sensitivity is one of the most common seafood allergies. However, to date, there has been no report on the molecular characterization of crab allergens and no comparative analysis with other seafood allergens. OBJECTIVE: This study was undertaken to clone, identify, and determine the primary structure of a major IgE-reactive molecule in crab. METHODS: We constructed an expression cDNA library from a common crab, Charybdis feriatus. This library was then screened with the use of sera from subjects with a well-documented history of type I hypersensitivity reactions upon ingestion of crab. An IgE-reactive clone was chosen and subcloned into plasmids for nucleotide sequence determination and expression in Escherichia coli. RESULTS: We identified a 1-kb cDNA designated as Cha f 1. Expression of Cha f 1 produces a 34-kd recombinant protein reactive to the IgE antibodies from patients with crab allergies but not from control subjects. Cha f 1 has an opening reading frame of 264 amino acids and demonstrates marked homology to the shrimp tropomyosin Met e 1. Absorption of allergic sera with Cha f I removes IgE reactivity to crab extract. Moreover, absorption of allergic sera with recombinant shrimp Met e 1 tropomyosin removes IgE reactivity to Cha f 1. CONCLUSIONS: This 34-kd protein, designated as Cha f 1, is the first identified major allergen of crab. Nucleotide and amino acid comparison shows that this protein is the crab tropomyosin. The molecular basis of shrimp and crab allergy is readily demonstrated at the nucleotide and amino acid level.

Allergens↗
PubMed1998

Effect of nitrogen source on growth and trichloroethylene degradation by methane-oxidizing bacteria.

The effect of nitrogen source on methane-oxidizing bacteria with respect to cellular growth and trichloroethylene (TCE) degradation ability were examined. One mixed chemostat culture and two pure type II methane-oxidizing strains, Methylosinus trichosporium OB3b and strain CAC-2, which was isolated from the chemostat culture, were used in this study. All cultures were able to grow with each of three different nitrogen sources: ammonia, nitrate, and molecular nitrogen. Both M. trichosporium OB3b and strain CAC-2 showed slightly lower net cellular growth rates and cell yields but exhibited higher methane uptake rates, levels of poly-beta-hydroxybutyrate (PHB) production, and naphthalene oxidation rates when grown under nitrogen-fixing conditions. The TCE-degrading ability of each culture was measured in terms of initial TCE oxidation rates and TCE transformation capacities (mass of TCE degraded/biomass inactivated), measured both with and without external energy sources. Higher initial TCE oxidation rates and TCE transformation capacities were observed in nitrogen-fixing mixed, M. trichosporium OB3b, and CAC-2 cultures than in nitrate- or ammonia-supplied cells. TCE transformation capacities were found to correlate with cellular PHB content in all three cultures. The results of this study suggest that the nitrogen-fixing capabilities of methane-oxidizing bacteria can be used to select for high-activity TCE degraders for the enhancement of bioremediation in fixed-nitrogen-limited environments.

Ammonia↗
PubMed1998

Molecular identification of the lobster muscle protein tropomyosin as a seafood allergen.

Crustaceans are a major cause of seafood allergy. Recent studies have identified tropomyosin as the major allergen in shrimp. However, such data are lacking in other crustaceans. In the present study lobster allergens were identified and characterized by molecular cloning, sequencing, and expression. An IgE-reactive complementary DNA clone of 2 kilobase pairs (kb) was identified by screening an expression library of the spiny lobster Panulirus stimpsoni using sera from subjects with crustacean allergy. Expression and sequencing of this clone showed that it has an opening reading frame of 274 amino acids, coding for a 34-kDa protein designated as Pan s I. In addition, we expressed the fast muscle tropomyosin from the American lobster Homarus americanus and found that this protein, coined Hom a I, was also recognized by IgE from patients with crustacean allergies. The deduced amino acid sequences of Pan s I and Hom a I, which are the first identified lobster allergens, show significant homology to shrimp tropomyosin. Sera from subjects with crustacean allergies, when preabsorbed with recombinant proteins Pan s I or Hom a I, lost their IgE reactivity to muscle extract of P. stimpsoni and H. americanus. Preincubation of crustacean allergy sera with the recombinant shrimp tropomyosin Met e I also removed their IgE reactivity to lobster muscle extracts. The results suggest that patients with allergic reactions to crustaceans have common and possibly cross-reactive IgE-reactive epitopes in lobster and shrimp.

Allergens↗
PubMed1997

Assessment of sediment toxicity using different trophic organisms.

The main aim of the present project is to study the feasibility of using different trophic organisms for evaluating the toxicity of dredged sediments arising in Hong Kong. A total of eight sediment samples (duplicate samples collected from four selected sites: Kowloon Bay, Tsing Yi,Chek Lap Kok, and Double Haven) of Hong Kong coastal waters were analyzed for the total concentrations of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn, total organic carbon, acid volatile sulfides, simultaneously extracted metals, redox potential, and 12 organic micropollutants. The sediment elutriates were also analysed for the various metal concentrations, as well as contents of ammonia-N, nitrate, total sulfide, sulfate, and total organic carbon. Elutriate Sediment Toxicity Tests (ESTT) were also conducted, using two microalgae (Skeletonema costatum, a diatom and Dunaliella tertiolecta, a flagellate), juvenile shrimp (Metapenaeus ensis) and juvenile fish (Trachinotus obtaus). Two commercially available tests using bacteria (Microtox Test and Toxi-Chromotest) also were employed to test both the solid phase and elutriates of the sediments. The results of Microtox test on the solid phase, and bioassay tests using diatom on the sediment elutriate, especially the former, were correlated significantly (p < 0.05) with a number of physico-chemical properties of sediments and elutriates. It is recommended that a combination of a liquid-phase bioassay using diatom and a solid-phase bioassay using Microtox test should be used for screening a large number of sediment samples. However, the presence of ammonia in the sediments containing a high content of organic matter seemed to interfere the detection of contamination impacts.

Animals↗
PubMed1997

Effects of the insect growth regulator (S)-methoprene on survival and reproduction of the freshwater cladoceran Moina macrocopa.

This study examines the acute and chronic effects of the insecticide (S)-methoprene on the survival and reproduction of the freshwater cladoceran Moina macrocopa. In laboratory toxicity tests, the 24- and 48-h LC50 values for (S)-methoprene were 0.51 and 0.34 mg litre(-1), respectively. Survival, longevity and fecundity were reduced at 0.05 mg litre(-1) and higher concentrations. At 0.005 and 0.01 mg litre(-1), longevity and fecundity increased slightly as compared to control animals. If environmental concentrations of methoprene do not exceed 0.05 mg litre(-1), as is generally the case, application of this insecticide is unlikely to induce detrimental effects on natural cladoceran populations. The stimulatory effect of very low levels of methoprene on reproductive performance is consistent with the hypothesis of a regulatory role of juvenile hormone-like compounds in crustacean reproduction.

Journal Article↗
PubMed1996

IgE reactivity against a cross-reactive allergen in crustacea and mollusca: evidence for tropomyosin as the common allergen.

BACKGROUND: Although cross-reactivity between mollusks and other crustaceans in shrimp-sensitive subjects has been reported, the mechanism of this allergenic cross-reactivity has not been studied in detail. OBJECTIVE: To investigate this cross-reactivity in vitro, we have taken advantage of a complementary DNA that expresses tropomyosin, the immunodominant shrimp allergen. METHODS: Serum IgE from nine patients with known anaphylaxis to shrimp and five normal volunteers were analyzed by immunoblotting against 13 distinct crustaceans and mollusks. As additional antigens, muscle preparations were isolated from grasshopper, cockroach, fruit fly, chicken, and mouse. RESULTS: Sera from all patients, but not control subjects, reacted specifically with a 38 kd protein in all crustaceans and mollusks studied. In addition, 8 of 9 sera from patients, but from none of the normal control subjects, recognized proteins of various other molecular weights among the mollusk extracts studied. The 38 kd protein was identified as tropomyosin and was shown to share immunodominant epitopes among all species of crustaceans and mollusks tested by specific absorption studies. Moreover, sera from all nine subjects with shrimp allergy demonstrated IgE reactivities against grasshopper, cockroach, and fruit fly but not chicken or murine muscle. CONCLUSION: The allergic epitopes on tropomyosin are conserved among invertebrates including not only shellfish but also insects. This latter observation suggests that persons sensitive to shrimp should undergo further study for potential cross-reactive inhalant or ingested insect sensitivity.

Allergens↗
PubMed1994

Cloning, expression, and primary structure of Metapenaeus ensis tropomyosin, the major heat-stable shrimp allergen.

Shrimp is a common cause of seafood hypersensitivity. To study the mechanism of seafood hypersensitivity at the molecular level, we have determined the primary structure of the major heat-stable allergen of shrimp by cloning, expression, nucleotide sequencing, and amino acid sequence determination of an IgE-reactive cDNA clone, Met e I, isolated from a Metapenaeus ensis expression library in lambda gt 11. We first constructed a cDNA library from the shrimp M. ensis in lambda gt 11. We then screened the library with sera from patients with hypersensitivity reactions to shrimp and identified a positive IgE-reactive clone, designated as Met e I. This cDNA was purified to homogeneity and subsequently expressed in the plasmid pGEX. Serum antibodies from patients with shrimp allergy demonstrated positive IgE reactivity by immunoblotting to a protein encoded by the clone Met e I; sera from nonallergic control subjects were not reactive. The nucleotide sequence of this cDNA clone revealed an open reading frame of 281 amino acid residues, coding for a protein of 34 kd. Comparison of the Met e I amino acid sequence with the Genbank database showed that Met e I is highly homologous to multiple isoforms of tropomyosin.

Allergens↗
PubMed1987

Collagenase chemonucleolysis via epidural injection. A review of 252 cases.

Since 1975, collagenase has been injected into 252 herniated intervertebral discs for treatment of sciatica. Highly purified preparations of Chinese collagenase were extracted from Clostridium histolyticum CH 1093 in lyophylized form, which had a specific collagenolytic activity. It had a wide margin of safety as proven by repeated experiments in dogs by means of intradiscal, extradural, intradural, and intravenous injections. One hundred to two hundred units of collagenase dissolved in 5 ml of normal saline was injected epidurally in front of the line joining posterior vertebral body margins. The basic assumption is that the injected enzyme digested the nucleus pulposis. Symptoms disappeared or improved gradually within three to eight weeks. The total success rate was about 77%. For recurrent cases of those with less than satisfactory results, reinjections were performed without any visible antigenic reactions or neurologically adverse effects.

Adult↗
PubMed1986

Colonization of the gut of the blue crab (Callinectes sapidus) by Vibrio cholerae.

Attachment of Vibrio cholerae to the mucosal surface of the intestine is considered to be an important virulence characteristic. Vibrio cholerae, an autochthonous member of brackish water and estuarine bacterial communities, also attaches to crustacea, a significant factor in multiplication and survival of V. cholerae in nature. The ability of V. cholerae to attach to the gut wall of the blue crab (Callinectes sapidus) was examined, and attachment was observed only in the hindgut and not the midgut of crabs, confirming a requirement for chitin in the attachment of V. cholerae to invertebrate and zooplankton surfaces. The new finding of attachment of V. cholerae to the hindgut of crabs may be correlated with the epidemiology and transmission of cholera in the aquatic environment. The crab model may also prove useful in elucidating the mechanism(s) of ion transport in crustacea.

Animals↗
PubMedDate not supplied

Does race or socioeconomic status predict adverse outcome after out of hospital cardiac arrest: a multi-center study.

OBJECTIVE: To assess whether socioeconomic status (SES) or race is associated with adverse outcome after an out-of-hospital cardiac arrest (OHCA). METHODS: A convenience sample of OHCA of presumed cardiac origin from seven suburban cities in Michigan, 1991-1996. Median household income (HHI), utilizing patient home address and 1990 census tract data, was dichotomized above and below 1990 state median income. Patient race was dichotomized as black or white. Outcome was defined as survival to hospital discharge (DC). Multiple logistic regression and Pearson's chi2 values were used for analysis. RESULTS: Of 1317 cases with complete data for analysis, the average age was 67.3 +/- 16.0, 939 (71.1%) were white, 587 (44.4%) arrests were witnessed (WIT), and 65 (4.9%) were DC alive. There was no significant difference between races with respect to WIT arrests, V(T)/V(F) arrest rhythms, and a small difference in EMS response interval. Whites were more likely to be above median HHI (57.1 vs. 26.2%, P < 0.001). Adjusted odds ratios for predictors of survival were WIT arrest (OR = 3.76, 95% CI (1.7, 8.2)), V(T)/V(F) (OR = 8.74, 95% CI (3.7, 10.8), but not race (OR = 0.68, 95% CI (0.3, 1.4)) or SES (OR = 1.51, 95% C1 0.8, 2.8). CONCLUSION: In this population, neither race nor SES was independently associated with a worse outcome after OHCA.

Black or African American↗