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H W Zhou

Publications and source records attributed to H W Zhou.

13 recordsLinked to original sources
PubMed2006

Study of metabolites from the degradation of polycyclic aromatic hydrocarbons (PAHs) by bacterial consortium enriched from mangrove sediments.

The PAH metabolites produced during degradation of fluorene, phenanthrene and pyrene by a bacterial consortium enriched from mangrove sediments were analyzed using the on-fiber silylation solid-phase microextraction (SPME) combining with gas chromatography-mass spectrometry (GC-MS) method. Seventeen metabolites at trace levels were identified in different PAH degradation cultures based on the full scan mass spectra. In fluorene degradation cultures, 1-, 2-, 3- and 9-hydroxyfluorene, fluorenone, and phthalic acid were detected. In phenanthrene and pyrene degradation cultures, various common metabolites such as phenanthrene and pyrene dihydrodiols, mono-hydroxy phenanthrene, dihydroxy pyrene, lactone and 4-hydroxyphenanthrene, methyl ester, and phthalic acid were found. The detection of various common and novel metabolites demonstrates that SPME combining with GC-MS is a quick and convenient method for identification as well as monitoring the real time changes of metabolite concentrations throughout the degradation processes. The knowledge of PAH metabolic pathways and kinetics within indigenous bacterial consortium enriched from mangrove sediments contributes to enhance the bioremediation efficiency of PAH in real environment.

Bacteria↗
PubMed2005

Isolation of PAH-degrading bacteria from mangrove sediments and their biodegradation potential.

Surface sediment samples were collected from seven mangrove swamps in Hong Kong SAR with different degrees of contamination. The total concentrations of 16 PAHs in these sediments ranged from 169.41 to 1058.37 ng g(-1) with the highest concentration found in Ma Wan and the lowest in Kei Ling Ha Lo Wai mangrove swamp. In each swamp, three bacterial consortia were enriched from sediments using phenanthrene (Phe) as the sole carbon and energy source, and individual bacterial colony showing Phe degradation was isolated and identified by 16S rDNA gene sequence. The consortia enriched from Sai Keng and Ho Chung sediments had highest ability to degrade mixed PAHs in liquid medium, with 90% Phe and Fla (fluoranthene) degraded in 7 days. On the other hand, Kei Ling Ha Lo Wai-enriched consortia degraded less than 40% Phe and Fla. Pyrene (Pyr) was hardly degraded by the consortia enriched from sediments. Bacterial isolates, namely Rhodococcus (HCCS), Sphingomonas (MWFG) and Paracoccus (SPNT) were capable to degrade mixed PAHs (Phe + Fla + Pyr). Their degradation percentages could be lower, comparable or even higher than their respective enriched consortia, depending on the consortium and the type of PAH compounds. These results suggest that PAH-degrading bacteria enriched from mangrove sediments, either as a mixed culture or as a single isolate could be used for PAHs bioremediation.

Bacteria↗
PubMed2004

Recovery of function in osteoarthritic chondrocytes induced by p16INK4a-specific siRNA in vitro.

OBJECTIVE: To demonstrate the roles of p16(INK4a) in the senescence of human chondrocytes and the progression of osteoarthritis (OA). METHODS: Immunohistochemistry and reverse transcriptase polymerase chain reaction (RT-PCR) were performed to examine p16(INK4a) expression in fetal, normal age-matched and OA cartilage, and Western blot was used in primary cultured chondrocytes from different origins. To explore a functional p16(INK4a) knockdown in OA chondrocytes, the primary cultured cells were treated with p16(INK4a)-specific small interfering ribonucleic acids (siRNAs). Expression of p16(INK4a), p14(ARF) and p53 was observed by Western blot and RT-PCR. The phosphorylation status of pRb, senescence-associated beta-galactosidase (SA-beta-gal), cell G1/S transition and cell proliferation were studied by Western blot, histological staining, 3H-thymidine incorporation and cell counts respectively. Expression of the collagen I, collagen II and aggrecan genes was measured by semiquantitative RT-PCR. To establish the response of chondrocytes to cytokines, cells were treated with transforming growth factor-beta1 (TGF-beta1) or interleukin-1alpha (IL-1alpha) and examined for incorporation of 3H-thymidine, 3H-proline and 35S-sulphate respectively. RESULTS: A significant increase of p16(INK4a) was detected in OA chondrocytes compared with normal age-matched and fetal chondrocytes (P<0.01) in vivo and in vitro. Treated with p16(INK4a)-specific siRNAs, OA chondrocytes displayed a significant decrease in p16(INK4a) expression with an increase of phosphorylated pRb, but no alteration of p14(ARF) and p53 expression, followed by decreases of senescent features and increases in the expression of some chondrocyte-specific genes and overall repair capacity. CONCLUSIONS: p16(INK4a) is instrumental in the senescence of human articular chondrocytes or OA. The reduction of p16(INK4a) by RNA interference (RNAi) contributed to the recovery of osteoarthritic chondrocytes, suggesting that p16(INK4a) may be a viable future therapeutic candidate.

Aged↗
PubMed2001

Digestion of selected foods by Yunnan snub-nosed monkey Rhinopithecus bieti (Colobinae).

Three digestion trials were conducted to quantify aspects of digestive physiology in the Yunnan snub-nosed monkey Rhinopithecus bieti, a foregut fermenter that feeds primarily on lichens. Mean retention time (MRT, the average time plastic markers spent in the animal) had a mean estimate of 47 hr (n = 3) with high variability between trials (standard deviation = 17 hr). Recently captured animals, presumably with gut flora and digestive physiology close to wild animals, had a longer retention time than did long-term captives, although lack of standardization across trials (such as in activity level) confounds analysis. Apparent digestibilities for dry matter (71-80%) were in line with other studies of colobine digestion, but fall below those of ruminant ungulates feeding on lichens. Fecal analysis accurately determined the relative proportions of leaves vs. lichens in diets; mature leaves and lichens were not nutritional equivalents but appeared to be physiological equivalents in terms of digest passage. Fecal analysis does not, however, accurately determine the relative proportions of food types with different digestibilities, such as fruit vs. leaves.

Animals↗
PubMed2001

Effects of acrylamide on creatine kinase from rabbit muscle.

The mechanism of inhibition of creatine kinase (CK) by acrylamide (Acr) has been examined (in vitro). Within the concentration range of 0 to 1 M, Acr markedly inhibited CK and depleted the protein thiols. Both inactivation and thiol depletion were time- and Acr concentration-dependent. Addition of dithiothreitol (DTT) did not reactivate CK inactivated by Acr. However, CK with 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) pre-blocked thiols can be reactivated by DTT after incubation with Acr. The transition-state analogue also had a significant protective effect on CK against Acr inhibition. We conclude that thiol alkylation is a critical event in inactivation of CK by Acr. Furthermore, Acr binding to CK changed its surface charge, which may be the same effect for the toxicity of Acr towards other proteins.

Acrylamide↗
PubMed2000

Pectin esterase, polygalacturonase and gel formation in peach pectin fractions.

Peaches (Prunus persica cv. Hermoza) were stored at 0C in regular air (RA) or in controlled atmosphere (CA 10% CO2, 3% O2) for 4 weeks and then ripened for 4 days at 20 degrees C. Woolliness developed in the regular air stored fruit while the controlled atmosphere stored fruit ripened normally. In the woolly fruit symptoms of the disorder were greater in the inner mesocarp than in the outer. Polygalacturonase (PG) and pectin esterase (PE) activities differed in the outer and inner mesocarp of the affected fruit. PG activity was low and PE activity was high in the inner mesocarp of the woolly fruit during ripening relative to the outer mesocarp, while in the healthy fruit, activities were similar in both areas. Cell wall fractions of water-soluble, CDTA-soluble and carbonate-soluble pectins were prepared from freshly harvested peaches and incubated with PE and PG from ripe peaches at different ratios. Only the CDTA-soluble fraction formed a gel with peach enzymes, and the rate of gelation increased with increasing amounts of PE relative to PG. Both water-soluble and CDTA-soluble pectin fractions formed gels with commercial PE (extracted from orange peel). The PE extracted from peaches was stable when stored at 0 degrees C for 9 days, while PG activity was stable only for 1 day. We suggest that PE, acting on pectins in the cell wall in vivo may cause gel formation and that the CDTA-soluble polymers have the capacity to bind apoplastic water and create the dry appearance observed in woolly fruit.

Carboxylic Ester Hydrolases↗
PubMed1992

[Pharmacokinetic analysis of enterohepatic circulation of piroxicam in rabbits].

The concentration (c)-time (t) curves of piroxicam showed double peaks following iv 10 mg dose to 4 rabbits. A new mathematical model of enterohepatic circulation was proposed to explain this double-peak phenomenon and showed good agreement with data. This model provides not only the common pharmacokinetic parameters: T1/2 = 1.12 +/- 0.32 h, V1 = 0.64 +/- 0.12 L, AUC = 34.7 +/- 7.8 micrograms.h-1.ml-1, but also the parameters of enterohepatic circulation of piroxicam: the cycling amount of drug Db = 3.9 +/- 1.4 mg, reabsorption fraction Fb = 0.50 +/- 0.04, reabsorption rate constant Ka = 2.55 +/- 0.50 h-1. It is indicated in this study that enterohepatic circulation results in a 20% average increase of the effective amount of piroxicam.

Animals↗
PubMed1990

[Population kinetic program for Michaelis-Menten elimination].

The microcomputer program, PKP-ME (population kinetic program for Michaelis-Menten elimination), is presented to estimating population pharmacokinetic parameters of drug obeying Michaelis-Menten kinetics and predicting individual pharmacokinetic parameters. A data set consisting of 69 steady-state phenytoin concentration-dosage pairs from 44 out-patients was analyzed with the present program. Five population kinetic parameters and their standard deviations were given by PKPME. The capability predicting individual phenytoin dosage was assessed by the retrospective analysis of data of 44 patients and the prospective analysis of 15 patients. A good correlation existed between predicting dose and actual dose. Population correlation coefficient was equal to 0.99 at P = 0.05.

Epilepsy↗
PubMed1989

Search for deep slabs in the Northwest Pacific mantle.

A residual sphere is formed by projecting seismic ray travel-time anomalies, relative to a reference Earth model, onto an imaginary sphere around an earthquake. Any dominant slab-like fast band can be determined with spherical harmonic expansion. The technique is useful in detecting trends associated with high-velocity slabs beneath deep earthquakes after deep-mantle and near-receiver effects are removed. Two types of corrections are used. The first uses a tomographic global mantle model; the second uses teleseismic station averages of residuals from many events over a large area centered on the events of interest. Under the Mariana, Izu-Bonin, and Japan trenches, the dominant fast bands are generally consistent with seismicity trends. The results are unstable and differ from the seismicity trend for Kurile events. The predominant fast band for most deep earthquakes under Japan is subhorizontal rather than near vertical. We find little support for the deep slab penetration hypothesis.

Journal Article↗