Yuwai Ng

Yuwai Ng
Hong Kong Baptist University · Centre for Child Development

About

55
Publications
4,342
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1,174
Citations
Citations since 2017
1 Research Item
394 Citations
20172018201920202021202220230204060
20172018201920202021202220230204060
20172018201920202021202220230204060
20172018201920202021202220230204060
Introduction
Skills and Expertise

Publications

Publications (55)
Article
Whole genome sequencing is increasing used in epidemiology, e.g. for tracing outbreaks of food-borne diseases. This requires in-depth understanding of pathogen emergence, persistence, and genomic diversity along the food production chain including in food processing plants. We sequenced the genomes of 80 isolates of Listeria monocytogenes sampled f...
Article
Full-text available
The human pathogenic bacterium Listeria monocytogenes is exposed to antibiotics both during clinical treatment and in its saprophytic life tyle. As one of the keys to successful treatment is continued antibiotic sensitivity, the purpose of this study was to determine if exposure to sublethal antibiotic concentrations would affect the bacterial phys...
Article
Phaeobacter inhibens belongs to the marine Roseobacter clade and is important as a carbon and sulfur metabolizer, a biofilm former and producer of the antibiotic tropodithietic acid (TDA). The majority of cultured strains have been isolated from marine aquaculture sites, however, their niche in the environment is to date unknown. Here, we report on...
Article
Full-text available
Listeria monocytogenes can cause the serious infection listeriosis, which despite antibiotic treatment has a high mortality. Understanding the response of L. monocytogenes to antibiotic exposure is therefore important to ensure treatment success. Some bacteria survive antibiotic treatment by formation of persisters, which are a dormant antibiotic-t...
Article
Full-text available
The purpose of the present study was to determine if the monoculture antifouling effect of several pigmented pseudoalteromonads was retained in in vitro mesocosm systems using natural coastal seawater and when the bacteria were embedded in paint used on surfaces submerged in coastal waters. Pseudoalteromonas piscicida survived on a steel surface an...
Article
Materials coated with aqueous fish protein extracts can reduce bacterial adhesion, but the mechanism behind the observed effect is not fully understood. In this study we explore the physicochemical properties of fish muscle protein adlayers on four substrates: gold, stainless steel, polystyrene and silicon dioxide. The aims were (i) to determine if...
Article
Full-text available
We isolated 16 antibiotic-producing bacterial strains throughout the central Arctic Ocean, including seven Arthrobacter spp. with almost identical 16S rRNA gene sequences. These strains were numerically rare, as revealed using 454 pyrosequencing libraries. Arthrobacter spp. produced arthrobacilins A to C under different culture conditions, but othe...
Article
Full-text available
The aims of this study were to determine if marine bacteria from Danish coastal waters produce antifouling compounds and if antifouling bacteria could be ascribed to specific niches or seasons. We further assess if antibacterial effect is a good proxy for antifouling activity. We isolated 110 bacteria with anti-Vibrio activity from different sample...
Conference Paper
Full-text available
Bacterial antagonism plays a key role in microbial interactions, being a competitive advantage but also mean of communication. Bacterial metabolites with antagonistic activity could also have biotechnological applications. Here, we isolated marine bacteria from high Arctic environments (84 to 89º N) using Marine Agar 2216, chitin agar, two low-nutr...
Article
Fermentation of raw fish is a common process in Asia for improvement of shelf life and safety, however, little is known about the survival of pathogenic bacteria in these products. Raw fish may be contaminated with Salmonella and Vibrio species. The purpose of this study was to determine survival and potential growth of Salmonella enterica serovar...
Article
Preconditioning of stainless steel with aqueous cod muscle extract significantly impedes subsequent bacterial adhesion most likely due to repelling effects of fish tropomyosin. The purpose of this study was to determine if other food conditioning films decrease or enhance bacterial adhesion to stainless steel. Attachment of Pseudomonas fluorescens...
Article
Cleaning and disinfection are essential steps in preventing contamination of foods with pathogenic and spoilage bacteria. The efficacy of cleaning and disinfection products differ depending on target bacteria and type of soiling. We evaluated the effectiveness of cleaning and disinfecting products against Listeria monocytogenes attached on food soi...
Article
Full-text available
Growth of Listeria monocytogenes in ready-to-eat fish products such as cold-smoked salmon is an important food safety issue. The objective of this study was to evaluate the antilisterial activity of potassium lactate (PL) in combination with sodium acetate (SA) or sodium diacetate (SDA) in cold-smoked salmon and to determine whether these compounds...
Article
Full-text available
Microbial adhesion and biofilm formation on surfaces pose major problems and risks to human health. One way to circumvent this problem is to coat surfaces (in this report stainless steel) with a non-toxic fish extract that generates an abiotic surface with less bacterial attachment than uncoated surfaces or surfaces coated with, for example, trypto...
Article
Full-text available
To study the importance of bacteriocin production for the antilisterial effect of a bacteriocinogenic Carnobacterium piscicola strain A9b on growth of Listeria monocytogenes in broth and cold-smoked salmon systems. Acriflavin treatment of strain A9b resulted in loss of bacteriocin production and of immunity to carnobacteriocin B2. Two plasmids pres...
Article
The microflora adhering to the processing equipment during production and after cleaning and disinfecting procedures was identified in four different processing plants. A total of 1009 microorganisms was isolated from various-agar plates and identified. A stepwise procedure using simple phenotypic tests was used to identify the isolates and proved...
Article
Full-text available
Carnobacterium piscicola strain A9b isolated from cold smoked salmon inhibits growth of the food-borne pathogen Listeria monocytogenes partly due to the production of a proteinaceous compound (L. Nilsson, L. Gram, and H. H. Huss. J. Food Prot. 62:336-342, 1999). The purpose of the present study was to purify the compound and describe factors affect...
Article
Cardiac Na+,K(+)-ATPase, the receptor molecule for digitalis glycosides, have isoforms with different intrinsic affinities for the glycosides. Expression of these isoforms are under developmental and hormonal regulation. Switching in isoforms to those with lower intrinsic affinity may decrease digitalis sensitivity of the heart. In addition to the...
Article
Some anti-malarials have deleterious effects upon the heart. The actions of two of these, chloroquine and quinacrine, were compared on isolated guinea-pig atria and Langendorff preparations to assess their effects on several calcium pools. Both compounds decreased developed tension in a concentration (chloroquine 10-100 microM; quinacrine 3-100 mic...
Article
We have shown previously that in the ferret heart there are two isoforms of Na+-K+-ATPase, alpha(+) and alpha, and that these isoforms undergo developmental changes. In the present study, we examine regulation of the isoenzymes by thyroid hormone, which is well known to increase activity of Na+-K+-ATPase in different tissue preparations. Ferrets we...
Article
Gossypol is an orally active male contraceptive with cardio-depressant side effects. To understand the mechanism of its cardiac actions, the interaction of gossypol with positive inotropic drugs was examined in isolated atrial muscle preparations obtained from guinea-pig heart. Gossypol delayed the onset of arrhythmias caused by digoxin. In the pre...
Article
Prednisolone-3,20-bisguanylhydrazone (PBGH), a steroid derivative, has been shown to inhibit Na+,K+-ATPase isolated from guinea-pig heart or kidney in concentrations significantly lower than those required to inhibit the enzyme obtained from other sources. Because Na+,K+-ATPases obtained from guinea-pig heart or kidney are predominantly of the alph...
Article
We have previously shown that gossypol has direct actions on isolated atrial muscle preparations. The possible mechanisms responsible for the transient positive and sustained negative inotropic effects of gossypol were examined under conditions that modify Ca2+ pools involved in contractile activation. In Langendorff preparations obtained from guin...
Article
We have previously reported that adult ferret hearts have high affinity and low affinity ouabain-binding sites in approximately equal abundance corresponding, respectively, to alpha(+) and alpha subunits of Na+,K+-ATPase. In the present study, possible changes in relative abundance of the two molecular forms of Na+,K+-ATPase during postnatal develo...
Article
In partially purified Na+-K+-adenosinetriphosphatase (ATPase) obtained from ferret heart, ouabain produced a monophasic inhibition curve; however, the curve spanned over 5 logarithmic units, indicating the presence of more than one classes of enzyme. [3H]ouabain binding studies revealed high-and low-affinity binding sites in approximately equal abu...
Article
In cardiac muscle isolated from most mammalian species, an elevation of extracellular K+ concentration decreases developed tension. This is explained from stimulation of the Na pump. In rat myocardium, however, developed tension increased when K+ concentration was raised from 3.5 to 9.5 mM, seemingly inconsistent with the above explanation. Activat...
Article
Gossypol, an orally active male contraceptive, has been reported to produce cardiotoxicity. In the present study, direct actions of gossypol on the heart muscle were examined using atrial muscle preparations isolated from guinea-pig heart. Gossypol (20-30 microM) produced a transient positive chronotropic effect in spontaneously beating right atria...
Article
Ventricular muscle of rat heart has two classes of receptors which are responsible for the positive inotropic effect of ouabain. Low affinity receptors are apparently related to Na+, K+-ATPase. To determine if high affinity receptors are also sarcolemmal Na+, K+-ATPase of muscle cells, their characteristics were examined. Binding of [3H]ouabain to...
Article
Positive inotropic effects of strophanthidin were compared with those of isoproterenol, BAY K 8644, grayanotoxin, veratridine, and monensin in electrically stimulated left atrial muscle preparations of guinea pig heart under conditions in which the calcium pool, playing a primary role in contractile activation, was altered. In concentrations that c...
Article
The direct effects of amiloride on myocardial contractility were examined in electrically stimulated left atrial muscle of guinea-pig heart. Amiloride (0.3 to 1.5 mM) produced a positive inotropic effect which, at higher concentrations, was followed by a decline in developed tension. These effects were not accompanied by contracture or arrhythmia a...
Article
During attempts to isolate and identify an endogenous ligand for the glycoside binding sites on Na+,K+-ATPase, bovine adrenal glands were found to contain a potent inhibitor of isolated Na+,K+-ATPase. The inhibitory principle was extracted from adrenal cortex, following homogenization in NaHCO3 solution and separation on a Sephadex G-10 column. The...
Article
Inhibition of Na,K-ATPase by cardiac glycosides is at least partially antagonized by K+. The kinetics of the antagonism, however, appear complicated because K+ is capable of reducing both association and dissociation rate constants for the glycoside-enzyme interaction. In order to better understand the effect of K+, inhibition of partially purified...
Article
The mechanisms responsible for the positive inotropic effect of phencyclidine were studied in isolated preparations of guinea pig and rat heart. In electrically paced left atrial muscle preparations, phencyclidine increased the force of contraction; rat heart muscle preparations were more sensitive than guinea pig heart muscle preparations. The pos...
Article
Percutaneous (pc) absorption, disposition, and excretion of 14C-MBOCA (4,4'-methylenebis(2-chloroaniline) ) were investigated in male beagle-type dogs by HPLC and compared to intravenously (iv) administered controls. Following application of 115 muCi MBOCA to a 25 cm2 area of the skin, no measurable radioactivity was detected in blood for the subse...
Article
A progesterone derivative, chlormadinone acetate, has been reported to inhibit isolated Na,K-ATPase, to increase intracellular sodium, to decrease the force of myocardial contraction and to antagonize the positive inotropic action of ouabain. Because several inhibitors of isolated Na,K-ATPase fail to interact with the sodium pump in intact cells, t...
Article
Characteristics of more than one class of ouabain receptors which appear to exist in ferret heart were examined. In isolated papillary muscle, 1 to 30 nM ouabain produced a positive inotropic effect in the presence of 5 ..mu..M propranolol and 2 ..mu..M phentolamine. Higher concentrations of ouabain (0.1 to 10 ..mu..M) produced an additional and pr...

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