Automated reticulocyte counting--an evaluation of GEN-S, Cell-Dyn 3500 and Cell-Dyn 4000.
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Humans↗
Biomedical subjects
P H Yu
Publications and source records attributed to P H Yu.
Simultaneous determination of formaldehyde and methylglyoxal in urine: involvement of semicarbazide-sensitive amine oxidase-mediated deamination in diabetic complications.
The deamination of methylamine and aminoacetone by semicarbazide-sensitive amine oxidase (SSAO) produces formaldehyde and methylglyoxal, respectively, which have been presumed to be involved in diabetic complications. A high-performance liquid chromatography procedure using 2,4-dinitrophenylhydrazine (DNPH) as a derivatizing agent is developed to determine endogenous formaldehyde, methylglyoxal, malondialdehyde, and acetaldehyde. The devised DNPH method is sensitive enough to analyze aldehyde levels in urine. An increase in the excretion of formaldehyde, methylglyoxal, and malondialdehyde is confirmed in streptozotocin-induced diabetic rats. Following the chronic administration of methylamine, the urinary levels of both formaldehyde and malondialdehyde (a product from lipid peroxidation) are found to be substantially increased. A potent selective SSAO inhibitor, (E)-2-(4-fluorophenethyl)-3-fluoroallylamine hydrochloride (MDL-72974A), reduced the formation of formaldehyde, methylglyoxal, and malondialdehyde. The increase of the cytotoxic aldehyde levels as a result of increased SSAO-mediated deamination may occur in some pathological conditions.
Amine Oxidase (Copper-Containing)↗
Accumulation of biopolymers in activated sludge biomass.
In this study, activated sludge bacteria from a conventional wastewater treatment process were induced to accumulate polyhydroxyalkanoates (PHAs) under different carbon-nitrogen (C:N) ratios. As the C:N ratio increased from 20 to 140, specific polymer yield increased to a maximum of 0.38 g of polymer/g of dry cell mass while specific growth yield decreased. The highest overall polymer production yield of 0.11 g of polymer/g of carbonaceous substrate consumed was achieved using a C:N ratio of 100. Moreover, the composition of polymer accumulated was dependent on the valeric acid content in the feed. Copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] was produced in the presence of valeric acid. The 3-hydroxyvalerate (3HV) mole fraction in the copolymer was linearly related to valeric content in the feed, which reached a maximum of 54% when valeric acid was used as sole carbon source. When the 3HV U in the polymer increased from 0-54 mol%, the melting temperature decreased from 178 degrees to 99 degrees C. Thus, the composition, and hence the mechanical properties, of the copolymer produced from activated sludge can be controlled by adjusting the mole fraction of valeric acid in the feed medium.
Journal Article↗
Conversion of industrial food wastes by Alcaligenes latus into polyhydroxyalkanoates.
Broader usage of biodegradable plastics in packaging and disposable products as a solution to environmental problems would heavily depend on further reduction of costs and the discovery of novel biodegradable plastics with improved properties. As the first step in our pursuit of eventual usage of industrial food wastewater as nutrients for microorganisms to synthesise environmental-friendly bioplastics, we investigated the usage of soya wastes from a soya milk dairy, and malt wastes from a beer brewery plant as the carbon sources for the production of polyhydroxyalkanoates (PHA) by selected strain of microorganism. Bench experiments showed that Alcaligenes latus DSM 1124 used the nutrients from malt and soya wastes to biosynthesise PHAs. The final dried cell mass and specific polymer production of A. latus DSM 1124 were 32g/L and 70% polymer/cells (g/g), 18.42 g/L and 32.57% polymer/cell (g/g), and 28 g/L and 36% polymer/cells (g/g), from malt waste, soya waste, and from sucrose, respectively. These results suggest that many types of food wastes might be used as the carbon source for the production of PHA.
Journal Article↗
Performance of fibrous bed bioreactor for treating odorous gas. Scientific note.
A fibrous bed bioreactor was used for treatment of odorous volatile fatty acid (VFA). The effect of gaseous VFA (acetic, propionic, and butyric acids) mass loading on the bioreactor performance was investigated. The VFA degrading microbial culture was selected from activated sludge by the three VFAs using a shake-flask culture. The selected microorganisms were then immobilized in a biofilter using cotton fabric as packing material. In the biofiltration experiment, the inlet gas flow rates ranged from 1 to 4 L/min, the total VFA concentrations ranged from 0.10 to 0.43 g/m3, and the resulting total mass loadings of VFA studied ranged from 9.7 to 104.3 g/m3/h. At total mass loading of 104.3 g/m3/h, the VFA removal efficiency was 87.7%. Higher removal efficiencies (>90%) were achieved at mass loadings below 50.3 g/m3/h.
Journal Article↗
Modeling and optimization of enantioseparation by capillary electrochromatography.
Both electrophoretic and chromatographic transport mechanisms are combined in electrochromatographic separation. In this paper, we developed a model of enantioselectivity in capillary electrochromatography (CEC) which can be applied in the separation of both neutral and ionic compounds. The overall selectivity in enantioseparation is considered to be made up of two contributions: one is the intrinsic difference in formation constants of a pair of enantiomers, and the other is the conversion efficiency of the intrinsic difference into the apparent difference in the migration velocity. The model was illustrated through the chiral separation of (R)- and (S)-salsolinols. Under a positive electric field, enantioseparation of salsolinols was achieved on an ODS column with beta-cyclodextrin as a chiral mobile-phase additive. The experimental results are discussed in relation to the effect of separation parameters, such as the direction and size of electric field and properties of the stationary and mobile phases. It was demonstrated that if both electrophoretic and partitioning mechanisms produce positive effects, high overall selectivity in CEC can be obtained. For pressurized-driven electrochromatography, although the column efficiency is sacrificed due to the introduction of hydrodynamic flow, the increased selectivity significantly reduced the requirement of large column plate numbers for resolution.
Buffers↗
Deamination of methylamine and angiopathy; toxicity of formaldehyde, oxidative stress and relevance to protein glycoxidation in diabetes.
Semicarbazide-sensitive amine oxidase (SSAO) is located in the vascular smooth muscles, retina, kidney and the cartilage tissues, and it circulates in the blood. The enzyme activity has been found to be significantly increased in blood and tissues in diabetic patients and animals. Methylamine and aminoacetone are endogenous substrates for SSAO. The deaminated products are formaldehyde and methylglyoxal respectively, as well as H2O2 and ammonia, which are all potentially cytotoxic. Formaldehyde and methylglyoxal are cytotoxic towards endothelial cells. Excessive SSAO-mediated deamination may directly initiate endothelial injury and plaque formation, increase oxidative stress, which can potentiate oxidative glycation, and/or LDL oxidation and damage vascular systems. Formaldehyde is also capable of exacerbating advanced glycation, and thus increase the complexity of protein cross-linking. Uncontrolled SSAO-mediated deamination may be involved in the acceleration of the clinical complications in diabetes.
Amine Oxidase (Copper-Containing)↗
Accumulation of biodegradable copolyesters of 3-hydroxy-butyrate and 3-hydroxyvalerate in Alcaligenes eutrophus.
Biodegradable copolyesters of 3-hydroxybutyrate-co-3-hydroxyvalerate (3HB-3HV) were produced by Alcaligenes eutrophus in a two-staged process, namely growth stage and nitrogen-deficient polyester-accumulation stage. When C5 was used as the sole carbon source, the copolyester contained 43 mol % of 3HV. A range of copolyesters with 0-43 mol % of 3HV could be produced by using a medium containing different concentration ratios of butyric acid C4 and C5. Tm of PHB homopolymer was 177.6 degrees C and that of copolyester with highest 3HV mol fraction of 43% was 99.0 degrees C. C5 concentration in the medium could be an effective means to control the polymeric composition and mechanical properties of the copolyesters accumulated in A. eutrophus.
3-Hydroxybutyric Acid↗
Endogenous formaldehyde as a potential factor of vulnerability of atherosclerosis: involvement of semicarbazide-sensitive amine oxidase-mediated methylamine turnover.
The mouse is known to be highly resistant to atherosclerosis. However, some inbred mouse strains are vulnerable to atherosclerosis when they are fed a high-cholesterol, high-fat diet. Increased deamination of methylamine (MA) and the subsequent production of formaldehyde has been recently shown to be a potential risk factor of atherosclerosis. In the present study semicarbazide-sensitive amine oxidase (SSAO)-mediated MA turnover in C57BL/6 mouse, a strain very susceptible to atherosclerosis, has been assessed in comparison to a moderate, i.e. BALB/c, and resistant, i.e. CD1, mouse strains. Kidney and aorta SSAO activities were found to be significantly increased in C57BL/6 in comparison to BALB/c and CD1 mice. A significant increase of urinary MA and formaldehyde were detected in C57BL/6. [14C]MA following intravenous injection would be quickly metabolized by SSAO. The labeled formaldehyde product would cross link with proteins. C57BL/6 exhibits significantly higher labeled protein adducts than BALB/c and CD1 in response to [14C]MA. The results indicated that mice vulnerable to atherosclerosis possess an increased SSAO-mediated MA turnover. The increase of production of formaldehyde, possibly other aldehydes, may induce endothelial injury or be chronically involved in protein cross-linking and subsequent angiopathy.
Allyl Compounds↗
Deamination of methylamine and aminoacetone increases aldehydes and oxidative stress in rats.
Semicarbazide-sensitive amine oxidase (SSAO)-mediated deamination of methylamine and aminoacetone in vitro produces carbonyl compounds, such as formaldehyde and methylglyoxal, which have been proposed to be cytotoxic and may be responsible for some pathological conditions. An HPLC procedure was developed to assess different aldehydes, which were derivatized with 2,4-dinitrophenylhydrazine (DNPH). We have demonstrated in vivo deamination of methylamine and aminoacetone by examining the excretion of formaldehyde and methylglyoxal, respectively, in rats. Following chronic administration of methylamine, the urinary level of malondialdehyde (MDA), an end product of lipid peroxidation, was also found to be substantially increased. A selective SSAO inhibitor blocked the increase of MDA. The results support the idea that increased SSAO-mediated deamination of methylamine and aminoacetone can be a potential cytotoxic risk factor.
Acetaldehyde↗
Aliphatic N-methylpropargylamines: monoamine oxidase-B inhibitors and antiapoptotic drugs.
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Animals↗
Increase of formation of methylamine and formaldehyde in vivo after administration of nicotine and the potential cytotoxicity.
Methylamine is a constituent of cigarette smoke and the major end product of nicotine metabolism. Smoking or nicotine can induce the release of adrenaline, which is in turn deaminated by monoamine oxidase, also producing methylamine. We found that the urinary level of methylamine was significantly elevated following administration of nicotine (25 mg/Kg, i.p.). Semicarbazide-sensitive amine oxidase (SSAO) inhibitors further increased the excretion of methylamine induced by nicotine. Following administration of L-(-)-[N-methyl-3H]nicotine long-lasting irreversible radioactive adducts were detected in different mouse tissues and such adduct formation could be blocked by selective SSAO inhibitors. These adducts are probably cross-linked oligoprotein complexes cross-linked by formaldehyde. The findings support the idea that nicotine can enhance SSAO/methylamine-mediated increase of formaldehyde and oxidative stress and this could in part contribute the adverse effect of health associated with smoking.
Allyl Compounds↗
Aliphatic N-methylpropargylamines as potential neurorescue agents.
Several clinical investigations have indicated that R-deprenyl, a typical monoamine oxidas B inhibitor, delays the progression of Parkinson's and Alzheimer's disease. A number of aliphatic N-methylpropargylamines, such as R-2-hexyl-N-methylpropargylamines (R-2HxMP), have been found to be highly potent, irreversible, selective, MAO-B inhibitors both in vitro and in vivo. These aliphatic propargylamines do not affect noradrenaline of dopamine uptake and are chemically without an amphetamine moiety and therefore do not exhibit any amphetamine-like effects. They are capable of protecting mouse striatal dopamine neurons against MPTP-induced toxicity in the caudate, against MK-801-induced apoptosis in the retrosplenial cortex and against DSP-4-induced depletion of naradrenergic axons. They rescue hippocampal neurons in rodents following kainate-induced neuronal damage. They block the expression of heat shock protein (HSP70) and delayed c-Fos expression in hippocampal CA1 region as elicited by kainate. Confocal microscopy also revealed prevention of neuronal damage in hippocampal slices under hypoxia-hypoglycemia conditions. Aliphatic N-methylpropargylamines may be useful in the treatment of neurodegenerative disorders. The mechanism and site of action of the neurorescue effect of these propargylamines, however, remains to be established.
Journal Article↗
Impairment of methylamine clearance in uremic patients and its nephropathological implications.
The urinary levels of methylamine were analyzed by an HPLC/fluorometric method following derivatization of the amine with O-phthaldialdehyde (OPA). The excretion of methylamine in the uremic patients was found to be dramatically reduced. The impairment of clearance of methylamine explains why this amine was substantially increased in the serum of uremic patients. Increased deamination of methylamine would enhance formaldehyde and oxidative stresses, i.e. in the blood vessels, and cause vascular damage. This may be related to the increased risk of angiopathy associated with renal failure, and accelerate the progression of renal failure.
Deamination↗
Induction of preconvulsive behavior and Fos expression by dopamine-induced nigral lesion in the rat.
The substantia nigra pars reticulata (SNpr) has been proposed to play an important role in controlling the propagation and/or the generation of limbic seizures. Earlier work has shown that SN lesions have differential effects on seizure activity, suggesting that at least two discrete topographical regions mediate anticonvulsant or proconvulsant effects. The present investigation showed that exogenous dopamine (DA; 1.5-2.0 mumol) unilaterally injected into the anterior SNpr induced preconvulsive behavior (starting, immobilization, facial and mouth movements and wet-dog shakes). In addition, these rats showed Fos oncoprotein expression in the limbic system. These effects were observed in 90% of the rats with anterior SNpr DA injection. Rats with posterior SNpr injection did not show preconvulsive behavior nor Fos expression. These results show for the first time that unilateral DA lesion of the anterior portion of SNpr elicits Fos expression and preconvulsive behavior. In addition, the results suggest that lesion of the anterior and posterior regions of SNpr appear to exert different influences in the generation of preconvulsive behavior. The time course of behavior changes and Fos expression was also studied.
Animals↗
Dopamine- and L-beta-3,4-dihydroxyphenylalanine hydrochloride (L-Dopa)-induced cytotoxicity towards catecholaminergic neuroblastoma SH-SY5Y cells. Effects of oxidative stress and antioxidative factors.
Enhanced oxidative stress has been suggested to be involved in the degeneration of nigrostriatal dopaminergic neurons in Parkinson's disease. The high turnover rate of dopamine and/or unsequestered dopamine may cause an increase of formation of hydrogen peroxide via either oxidative deamination of dopamine by monoamine oxidase or autoxidation. Hydrogen peroxide would be converted to more toxic hydroxyl free radicals. L-beta-3,4-Dihydroxyphenylalanine hydrochloride (L-DOPA), the most useful drug in the symptomatic treatment of Parkinson's disease, has been considered to possess deteriorating degenerative side-effects. The catecholaminergic neuroblastoma SH-SY5Y cells were chosen to investigate the cytotoxic effect of dopamine and L-DOPA. Both dopamine and L-DOPA were found to be cytotoxic towards SH-SY5Y cells. Such toxic effects were accompanied by an increase of oxidative stress in the cell cultures and could be reversed effectively by catalase and to a lesser extent by superoxide dismutase. The non-enzymatic antioxidants L-ascorbic acid, glutathione, N-acetyl-L-cysteine, but not (+)-alpha-tocopherol, also completely protected SH-SY5Y cells against the cytotoxic effects induced by dopamine and L-DOPA. Antioxidative factors, namely free radical scavengers (including N-tert-butyl-alpha-phenylnitrone, salicylic acid, and D-mannitol) and a strong iron chelator, deferoxamine, however, did not protect the SH-SY5Y cells against dopamine and L-DOPA. The generation of reactive oxygen species and the resulting enhanced oxidative stress was clearly involved in the dopamine- and L-DOPA-induced cytotoxic effects. Hydrogen peroxide played the most important role related to cytotoxicity of dopamine and L-DOPA.
Ascorbic Acid↗
R(-)-deprenyl potentiates dopamine-induced cytotoxicity toward catecholaminergic neuroblastoma SH-SY5Y cells.
Autoxidation of dopamine or L-DOPA (3,4-dihydroxyphenylalanine) generates reactive oxygen species (ROS), i.e., hydrogen peroxide, superoxide, and hydroxyl radical, which are potentially cytotoxic. Increased formation of ROS has been proposed to be involved in the pathogenesis of many human diseases, including Parkinson's disease. Several reports suggest that R(-)-deprenyl (an MAO-B inhibitor and anti-Parkinsonian drug) may directly or indirectly exert antioxidant effects and thus protect neurons. We have assessed the toxic effects of dopamine and L-DOPA toward catecholaminergic neuroblastoma SH-SY5Y cells and whether R(-)-deprenyl and several structurally related compounds possess antioxidant effects in this system. The results show that both dopamine and L-DOPA are quite cytotoxic toward SH-SY5Y cells. R(-)-deprenyl rather than reducing this dopamine-induced toxicity actually enhances it. Structural analogues of R(-)-deprenyl, such as 4-methyldeprenyl, (-)-methylamphetamine, and clorgyline, exhibited similar effects. Some different MAO-B inhibitors, namely, the aliphatic N-methylpropargylamines, e.g., (+/-)-M-2-PP [N-(2-pentyl)-N-methylpropargylamine] and N-[2-hexyl]-N-methylpropargylamine, which can also protect and rescue neurons in several in vivo and in vitro models, did not exacerbate the cytotoxicity of dopamine. Neither R(-)-deprenyl nor (+/-)-M-2-PP affected the L-DOPA-induced cytotoxicity toward SH-SY5Y cells.
Antioxidants↗
Aminoguanidine inhibits semicarbazide-sensitive amine oxidase activity: implications for advanced glycation and diabetic complications.
Aminoguanidine, a nucleophilic hydrazine, has been shown to be capable of blocking the formation of advanced glycation end products. It reduces the development of atherosclerotic plaques and prevents experimental diabetic nephropathy. We have found that aminoguanidine is also quite potent at inhibiting semicarbazide-sensitive amine oxidase (SSAO) both in vitro and in vivo. The inhibition is irreversible. This enzyme catalyses the deamination of methylamine and aminoacetone, which leads to the production of cytotoxic formaldehyde and methylglyoxal, respectively. Serum SSAO activity was reported to be increased in diabetic patients and positively correlated with the amount of plasma glycated haemoglobin. Increased SSAO has also been demonstrated in diabetic animal models. Urinary excretion of methylamine is substantially increased in the rats following acute or chronic treatment with aminoguanidine. Urinary methylamine levels were substantially increased in streptozotocin (STZ)-induced diabetic rats following administration of aminoguanidine. The non-hydrazine SSAO inhibitor (E)-2-(4-fluorophenethyl)-3-fluoroallylamine hydrochloride (MDL-72974A) has been shown to reduce urinary excretion of lactate dehydrogenase (an indicator of nephropathy) in STZ-induced diabetic rats. Formaldehyde not only induces protein crosslinking, but also enhances the advanced glycation of proteins in vitro. The results support the hypothesis that increased SSAO-mediated deamination may be involved in structural modification of proteins and contribute to advanced glycation in diabetes. The clinical implications for the use of aminoguanidine to prevent glycoxidation have been discussed.
Amine Oxidase (Copper-Containing)↗