Biomedical subjects

P H Yu

Publications and source records attributed to P H Yu.

At least 37 records · Page 2Linked to original sources

PubMed2000

Effect of the Hypericum perforatum extract on serotonin turnover in the mouse brain.

St. John's Wort, a traditional herbal medicine obtained from the extract of Hypericum perforatum, has been used in the treatment of mild depression. Its mechanism of action remains to be established. The present study confirmed that Hypericum extract exhibited very weak inhibitory activities towards MAO. Mouse brain MAO activities was unchanged following either acute or chronic treatment with Hypericum extract. 5-HIAA levels were found to be significantly increased in the cerebral cortex, hypothalamus, hippocampus and caudate 3 h after treatment with the Hypericum extract at a dose as low as 10 mg/Kg. An increase of 5-HT levels was also observed in hypothalamus and hippocampus. The increase of brain 5-HIAA was not further enhanced following chronic administration of the herb. The Hypericum extract significantly reduced the plasma tryptophan levels, the precursor of 5-HT. The action of Hypericum extract is consistent with the notion that serotonergic system is involved. The effect of Hypericum extract on the brain 5-HIAA and 5-FIT levels appeared to be quite different from the effect of classical 5-HT re-uptake blockers.

Animals↗

PubMed2000

A novel magnetite-immobilized cell process for heavy metal removal from industrial effluent.

The sorption and desorption of copper (II) (Cu[II]) ions from the wastewater by magnetite-immobilized cells of Pseudomonas putida 5-x with acidic pretreatment were studied. Pretreating cells with 0.6 N HCl was found to enhance greatly the adsorption capacity of biomass up to 85.6 mg/g and had no significant effect on the loss of P. putida 5-x cells during biosorbent pretreatment. The biosorption capacity to Cu2+ of magnetite-immobilized cells of P. putida 5-x harvested during various growth phases was also investigated. The experimental results illustrated that the adsorption capacity to Cu2+ of P. putida 5-x cultured in sulfate-limiting medium reached maximum during the late stationary growth phase or early death phase, and reached minimum during the log growth phase. The mechanism of copper sequestering by this type of biomass was studied via transmission electron microscopy. A degradation of the peptidoglycan layer of the cell wall was observed in the acidic pretreatment, but no further degradation appeared after the adsorption-desorption cycle. Cu(II) accumulated mostly on the surface of the cell walls and was effectively desorbed by the acidic treatment during the desorption process.

Adsorption↗

PubMed2000

Effect of food:microorganism ratio in activated sludge foam control.

Foaming is a common operational problem in activated sludge processes that often adversely affects the quality of the treated effluent. Overgrowth of the filamentous Nocardia spp. in the microbial ecosystem was previously identified as the cause of foaming. In the present study, the specific growth rate of Nocardia amarae was found to be much higher than that of nonfilamentous bacteria under food:microorganism (F:M) ratios lower than 0.5 mg of biological oxygen demand (BOD)/(mg of mixed liquor suspended solids [MLSS].d). This indicated that filamentous overgrowth may occur in normal activated sludge processes that are continually operated under the usual F:M range of 0.2-0.6 mg of BOD/(mg of MLSS.d). A novel two-component feast-fast operation (FFO) that capitalized on the sensitivity of filamentous bacteria to F:M ratio was designed to prevent and control foaming problems. The F:M ratio in the "feasting" aeration unit was 0.8 mg of BOD/(mg of MLSS.d) whereas that in the "fasting" aeration unit was 0.2 mg of BOD/(mg of MLSS.d). The FFO resulted in an overall process F:M ratio that still remained within the normal range, while avoiding prolonged exposure of the activated sludge ecosystem to an F:M ratio below 0.5 mg of BOD/(mg of MLSS.d). The FFO suppressed the overgrowth of filamentous bacteria without adversely affecting the organic treatment efficiency of the modified process.

Nocardia↗

PubMed2000

Construction of recombinant Escherichia coli strains for polyhydroxybutyrate production using soy waste as nutrient.

Construction and comparison of recombinant Escherichia coli strains harboring the polyhydroxybutyrate (PHB) operon from Ralstonia eutropha using vectors possessing different promotors, as well as the production of PHB from soy waste by the recombinant strain, are reported. The lac promotor was the most efficient on expression of the phb operon among the three promotors studied: i.e., lac promotor, T7 promotor and the normal sigma 70 promotor. The pKS/PHB was the most efficient plasmid for phb operon expression among the three plasmids used: i.e., pKS-, pAED4, and pJM9131. It was observed that isopropyl-beta-D-thiogalactopyranoside was not required for the induction of the expression of phb operon. The cell dry wt and polyhydroxyalkanoate content by E. coli XL-1 Blue (pKS/PHB) were 3.025 g/L and 27.83%, respectively.

Cupriavidus necator↗

PubMed2000

Design and performance of a fibrous bed bioreactor for odor treatment.

Biological processes have become popular for odor treatment. In this study, a novel fibrous bed bioreactor was applied for treatment of odorous gas. The column reactor was packed with spirally wound fibrous sheet material on which a consortium of microorganisms selected from activated sludge was immobilized. The first stage of this work comprised a preliminary study that aimed at investigating the feasibility of the fibrous bed bioreactor for treatment of odorous volatile fatty acids (VFAs). In this stage, the performance of a fibrous bed bioreactor at increasing mass loadings ranging from 9.7 to 104.2 g/(m3.h) was studied. VFA removal efficiencies above 90% were achieved at mass loadings up to 50.3 g/(m3.h). At a mass loading of 104.2 g/(m3.h), removal efficiency was found to be 87.7%. In the second stage of the work, the process was scaled up with design and operational considerations, namely, packing medium, process condition, and configuration selections. A trickling biofilter with synthetic fibrous packing medium was selected. It was operated under countercurrent flow of gas and liquid streams. The effects of inlet concentration and empty bed retention time on bioreactor performance were studied. The bioreactor was effective in treating odorous VFAs at mass loadings up to 32 g/(m3.h), at which VFAs started to accumulate in the recirculation liquid, indicating that the biofilm was unable to degrade all the VFAs introduced. Although VFAs accumulated in the liquid phase, the removal efficiency remained above 99%, implying that the biochemical reaction rate, rather than gas-to-liquid mass transfer rate, was the limiting factor of this process. The bioreactor was stable for long-term operation; no clogging and degeneration of the packing medium was observed during the 4-mo operation.

Bioreactors↗

PubMed2000

Effects of trace levels of copper, chromium, and zinc ions on the performance of activated sludge.

The effects of copper, chromium, and zinc ions, at trace levels, on the performance of a simulated activated sludge process were investigated. The results of batch adsorption experiments showed that the adsorption of copper, chromium, and zinc ions followed both the Langmuir and Freundlich isotherms. The presence of trace levels of these three metals not only reduced the adsorption rate of organic matters but also the chemical oxygen demand adsorption capacity (CAC) of the activated sludge. Metal ions competed with the organic substrate for adsorption binding sites on the surfaces of activated sludge bioflocs and reduced the CAC. Studies performed in a sequential batch reactor (SBR) showed that the presence of trace levels of heavy metal ions in wastewater affected the SBR performance to different extents depending on the hydraulic retention time (HRT). When the reactors were operated at short HRTs of 2.5 d or less, the presence of trace levels of heavy metal ions reduced substantially the CAC of activated sludge, which, in turn, affected significantly the performance of the SBR. However, under longer HRTs (e.g., 5 d), the heavy metal ions in the wastewater reduced the CAC but had no significant effect on the chemical oxygen demand removal efficiency.

Adsorption↗

PubMed2000

Microbial production of polyhydroxyalkanoates by bacteria isolated from oil wastes.

A Gram-positive coccus-shaped bacterium capable of synthesizing higher relative molecular weight (M(r)) poly-hydroxybutyrate (PHB) was isolated from sesame oil and identified as Staphylococcus epidermidis (by Microbial ID, Inc., Newark, NJ). The experiment was conducted by shake flask fermentation culture using media containing fructose. Cell growth up to a dry mass of 2.5 g/L and PHB accumulation up to 15.02% of cell dry wt was observed. Apart from using single carbohydrate as a sole carbon source, various industrial food wastes including sesame oil, ice cream, malt, and soya wastes were investigated as nutrients for S. epidermidis to reduce the cost of the carbon source. As a result, we found that by using malt wastes as nutrient for cell growth, PHB accumulation of S. epidermidis was much better than using other wastes as nutrient source. The final dried cell mass and PHB production using malt wastes were 1.76 g/L and 6.93% polymer/cells (grams/gram), and 3.5 g/L and 3.31% polymer/cells (grams/gram) in shake flask culture and in fermentor culture, respectively. The bacterial polymer was characterized by 1H-nuclear magnetic resonance (NMR), 13C-NMR, Fourier transform infrared, and differential scanning calorimetry. The results show that with different industrial food wastes as carbon and energy sources, the same biopolymer (PHB) was obtained. However, the use of sesame oil as the carbon source resulted in the accumulation of PHB with a higher melting point than that produced from other food wastes as carbon sources by this organism under similar experimental conditions.

Carbohydrate Metabolism↗

PubMed2000

Effect of C:N molar ratio on monomer composition of polyhydroxyalkanoates produced by Pseudomonas mendocina 0806 and Pseudomonas pseudoalkaligenus YS1.

Polyhydroxyalkanoates (PHAs) are biodegradable polymers produced by bacteria. In this study, the effect of C:N molar ratio on the monomer composition of PHAs was investigated, including medium chain length PHA produced by Pseudomonas mendocina 0806 and PHA blends consisting of monomers of 3-hydroxybutyrate and medium chain length hydroxyalkanoate produced by Pseudomonas pseudoalkaligenus YS1. It was observed that there were some fixed ranges of C:N molar ratio that affect the monomer composition of PHA independently of the substrate. For strain 0806, the ranges were C:N < 20, 20 < C:N < 200, and C:N > 200. The monomer composition was constant among these ranges when using glucose and octanoate as the sole substrate. For strain YS1, the ranges were C:N < 20, 20 < C:N < 45, and C:N > 45. These results are useful for controlling monomer composition in PHA production.

3-Hydroxybutyric Acid↗

PubMed2000

Optimal production of polyhydroxyalkanoates in activated sludge biomass.

Polyhydroxyalkanoates (PHAs) have been recognized as good candidates for biodegradable plastics, but their high price compared with conventional plastics has limited their use. In this study, activated sludge microorganisms from a conventional wastewater treatment process were induced, by controlling the carbon:nitrogen (C:N) ratio in the reactor liquor, to accumulate PHAs. In addition, an intermittent nitrogen feeding program was established to optimize the volumetric PHA productivity in a wastewater treatment process. The optimal overall polymer production yield of 0.111 g of polymer/g of carbonaceous substrate consumed was achieved under a C:N ratio of 96:1 by feeding nitrogen in the reactor liquor once every four cycles. At the same time, the amount of excess sludge generated from the wastewater treatment process was reduced by 22.9%.

Bacteria↗

PubMed2000

[Survey of susceptibility of anopheline vectors to insecticides in a malaria mesoendemic area, Hubei Province].

OBJECTIVE: To determine the susceptibility of Anopheles anthropophagus and Anopheles sinensis to deltamethrin and DDT in an area where different counter-measures had been adopted. METHODS: The mortality of the vectors was examined by using the standardised WHO test. RESULTS: The mortality for tentative diagnostic dose in An. anthropophagus to deltamethrin were 83.8%, 83.7% and 84.7%, respectively in the areas where impregnated net had been used for 1 year or 3 years and DDT residual spraying had been carried out for 3 years, suggesting that An. anthropophagus was an initially resistant group. The LT50 were 8.69, 7.48 and 9.87 min, respectively. The mortality for tentative diagnostic dose in An. sinensis to deltamethrin and DDT were 76.5%, 57.0% and 79.0%, respectively in three survey areas, suggesting that An. sinensis was a resistant group. The LT50 were 12.0, 15.4 and 11.2 min, respectively. The mortality for tentative diagnostic dose in An. sinensis to DDT was 95.8% in impregnated net area, suggesting that An. anthropophagus was an initially resistant group. The LC50 was 0.73%. The mortality for tentative diagnostic dose in An. sinensis to DDT was 44%, suggesting that An. sinensis was a highly resistant group. The LC50 was more than 4%. CONCLUSION: A substantial use of insecticides in the rice paddy field has resulted in resistance of An. sinensis, whereas no apparent resistance of An. anthropophgus has been found.

Animals↗

PubMed1999

Differential effects of staurosporine and retinoic acid on the vulnerability of the SH-SY5Y neuroblastoma cells: involvement of bcl-2 and p53 proteins.

Human catecholaminergic neuroblastoma cells (SH-SY5Y) have been widely used in different neurochemical investigations. Quite often these cells are induced to differentiation by various agents, such as staurosporine and retinoic acid. Interestingly, even though both staurosporine and retinoic acid induce similar morphological differentiation in SH-SY5Y cells, we found that these two groups of differentiated cells exhibited opposite vulnerability to harmful chemicals and physical insults. In the present study, cisplatin, 5-fluorouracil (5-FU), N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4), 6-hydroxydopamine (6-OHDA), and gamma-radiation were used to assess the tolerance of the differentiated cells. Cell viability was determined by 3-(4,5-dimethylthiazol-2yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. Staurosporine-treated SH-SY5Y cells were more sensitive to these toxic insults than the untreated controls. In contrast, retinoic acid-treated cells became more resistant to the same treatments. The expression of the proteins of the protooncogene Bcl-2 and the tumor suppressor gene p53 following staurosporine or retinoic acid treatment was assessed by Western blot and immunocytochemistry. Retinoic acid increased Bcl-2 and decreased p53 levels, whereas staurosporine decreased Bcl-2 and increased p53 levels. The opposite alteration of Bcl-2 (anti-apoptotic) and p53 (apoptotic) contents in SH-SY5Y cells with retinoic acid and staurosporine are attributed to the changes in cell vulnerability. These observations also indicate that caution should be taken when chemically induced differentiated neuroblastoma cells are to be used as an in vitro model for studying neuronal survival.

Benzylamines↗

PubMed1999

Translocation (12;17)(q13;q23) in de novo acute myeloid leukemia with trilineage myelodysplasia.

12q13 abnormalities have been reported to be associated with a variety of benign and malignant solid tumors. Recently, they have been shown to be a nonrandom karyotypic change in acute myeloid leukemia. We report a case of de novo acute myeloid leukemia with trilineage myelodysplasia showing t(12;17)(q13;q23) as the sole chromosomal abnormality. A review of the literature indicates that 12q13 translocation in acute myeloid leukemia is often associated with concomitant dysmyelopoietic changes. There is also evidence to suggest that 12q13 translocation occurs more frequently in acute myeloid leukemia with a prior history of mutagenic exposure or karyotypic indicators of secondary leukemia.

Acute Disease↗

PubMed1999

Mantle cell lymphoma in leukemic phase: characterization of its broad cytologic spectrum with emphasis on the importance of distinction from other chronic lymphoproliferative disorders.

BACKGROUND: Mantle cell lymphoma is a mature, virgin B-cell neoplasm characterized immunologically by a panB+, CD5+, CD23-, cyclin D1+ phenotype and genetically by t(11;14)(q13;q32) with overexpression of the cyclin D1 (bcl-1) gene. It usually presents as advanced stage disease, involving lymph nodes, spleen, bone marrow, and extranodal sites, particularly the gastrointestinal tract. However, frank leukemic presentation with high white cell counts is uncommon and can be difficult to distinguish from other chronic lymphoproliferative disorders. The aim of this study was to characterize the morphologic spectrum of leukemic mantle cell lymphoma. METHODS: During the period July 1994 through October 1998, 14 patients with mantle cell lymphoma in leukemic phase were diagnosed at the Department of Pathology, Queen Elizabeth Hospital, Hong Kong. The diagnosis of mantle cell lymphoma was based on histologic and immunocytochemical findings and was confirmed by cyclin D1 immunoreactivity in all cases. The clinical records and laboratory results were reviewed. Peripheral blood smears, bone marrow, and other tissue biopsies were examined, with particular attention to the cytologic features of the leukemic mantle cells. RESULTS: Mantle cell lymphoma in leukemic phase showed a very aggressive clinical course. Eight patients died at a mean of 13 months, and only 1 patient was disease free. Morphologically, the leukemic mantle cells exhibited a broad morphologic spectrum, with several cytologic patterns identified: 1) mixed small and medium-sized cells, 2) predominantly medium-sized cells, 3) predominantly large cells, and 4) giant cells. Despite variations in the size and nuclear shape, the leukemic mantle cells could usually be recognized by the nuclear irregularity and clefting, moderately dense but evenly distributed chromatin, small nucleoli, and scant cytoplasm. CONCLUSIONS: Recognition of the characteristic cytologic features of leukemic mantle cells can help to distinguish them from other chronic lymphoproliferative disorders. In contrast to the latter, the clinical course is aggressive and response to conventional chemotherapy is poor.

Aged↗

PubMed1999

MK-801-induced expression of Fos protein family members in the rat retrosplenial granular cortex.

The N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 has been shown to induce an acute Fos and Fos-related antigen (Fra) expression in the rat retrosplenial granular cortex (RSG), but the exact composition of the Fos protein family and their individual dynamic alterations are unknown. We examined this issue using immunocytochemistry and Western blot analysis with two antibodies that recognize, respectively, Fos and all the identified members of Fos protein family. Immunocytochemistry detected a rapid and transient expression of Fos proteins in some RSG neurons and a delayed and prolonged expression of Fra proteins in most RSG neurons following a single systemic MK-801 injection (1 mg/kg). Multiple MK-801 injections (i.e., ten consecutive injections once every other day; 1 mg/kg) produced a moderate Fra expression but failed to induce detectable Fos expression. Western blot analysis further showed a transient expression of 72-kDa Fos proteins following a single MK-801 injection and a prolonged expression of 46- and 43-kDa Fra proteins after either a single or multiple MK-801 administration. The delayed onset and prolonged expression of these Fra proteins suggest that they may be DeltaFosB. The possible relevance of these results to clinical psychotomimetic effects of the NMDA receptor antagonists phencyclidine and ketamine is discussed.

Animals↗

PubMed1999

A man with natural killer cell lymphoma showing 46,XX and deletion 6q.

Specific chromosomal abnormalities have been shown to be associated with certain types of leukemia and lymphoma. We and others have recently demonstrated del(6)(q21q25) as being strongly associated with natural killer cell lymphoma/leukemia. In this report, we describe a case of natural killer cell lymphoma with a clonal chromosomal abnormality of 46,X,-Y,+X,t(2;9)(q31;p24), del(4)(q21q25),del(6)(q21q23), and propose that the region 6q23 is probably an important site of genetic alteration in this group of tumors.

Adult↗

PubMed1999

Assessment of the deamination of aminoacetone, an endogenous substrate for semicarbazide-sensitive amine oxidase.

Methylglyoxal, a toxic aldehyde, has been reported to be increased in diabetes and has been claimed to be related to diabetic complications. Aminoacetone, an intermediate in the metabolism of threonine and glycine, has been proposed to be an endogenous substrate for semicarbazide-sensitive amine oxidase (SSAO). Methylglyoxal is the product. An HPLC procedure for the determination of SSAO activity toward aminoacetone in vitro is described. It was observed in previous assays that methylglyoxal formed via deamination of aminoacetone was quite unstable and led to erroneous results. o-Phenylenediamine (o-PD) was therefore employed for derivatization of methylglyoxal. o-PD does not affect SSAO activity and can be included in the enzyme reaction mixture for continuous trapping of methylglyoxal. This can avoid the loss of methylglyoxal during incubation. Deamination of aminoacetone by human umbilical artery SSAO was confirmed with this improved assay. The values of Km and Vmax, are 125.9 +/- 20.5 microM and 332.2 +/- 11.7 nmol/h/mg protein, respectively. Deamination of aminoacetone was nearly completely inhibited by 1 mM semicarbazide and 1 microM MDL-72974A, a potent selective SSAO inhibitor, whereas MAO inhibitors clorgyline (1 mM) and deprenyl (1 mM) had no inhibitory effect.

Acetone↗

PubMed1999

Sub-lethal effects of heavy metals on activated sludge microorganisms.

The effects of heavy metals, at sub-lethal concentrations, on activated sludge microbial ecosystem were investigated. Adsorption capacity and rate of copper, chromium, lead and zinc on microbial flocs were much faster than that of organic matters. Metals affected not only the adsorption rate of organic matters but also the COD adsorption capacity of the activated sludge. Effects of heavy metals, on wastewater treatment performance of a sequencing batch reactor were also studied. Metal-laden wastewater at sub-lethal levels affected the performance to different extents, depending on the hydraulic retention time. Metal ions acted as a strong competitor against the organic compounds for active sites on the bioflocs instead of acting as a toxic microbial inhibitor, thus hampering organic adsorption and affecting the COD removal efficiency under shorter HRTs.

Adsorption↗

PubMed1999

Inversion of selectivity of N-substituted propargylamine monoamine oxidase inhibitors following structural modifications to quaternary salts.

A number of N-substituted-propargylamines are well known mechanism-based MAO inhibitors. Clorgyline and deprenyl in fact represent archetypal MAO-A and MAO-B inhibitors respectively. In the present study several ring-substituted deprenyl structural analogues were synthesized and alterations of selectivity and potency towards MAO-A and MAO-B activities were found. When deprenyl and its structural analogues were further modified to their corresponding quaternary ammonium salts. i.e. by attaching either an extra propargyl or a methyl group to the nitrogen atom, the potency of inhibition of MAO-B activity was drastically reduced and inhibition of MAO-A activity substantially increased. Such a complete inversion of selectivity may be related to a hydrophilic and electrophilic region seemingly present only in the MAO-A but not in the MAO-B molecule. The results also suggest that at least three sites are required for the selectivity and mechanism-based action of an inhibitor towards MAO.

Amino Acid Sequence↗