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Biomedical subjects

Y Tan

Publications and source records attributed to Y Tan.

At least 181 records · Page 10Linked to original sources
PubMed1994

Relative efficiency of leucocyte removal procedures for the production of leucocyte-poor red cell concentrates assessed by flow cytometry.

Flow cytometry was used to: (1) determine residual leucocyte numbers in red cell suspensions following the range of leucocyte depletion procedures used in our organisation, and (2) to characterize phenotypically the leucocytes using direct immunofluorescence with monoclonal antibodies to cell surface receptors. Under the conditions used, a lower limit of detection of 2.5 leucocytes per microliter (equivalent to 3.43 log10 or 99.96% removal) could be achieved. Filtration through polyester filters was found to remove up to > 99.96% of the initial leucocytes; however, a significant differential efficacy was observed between filters from different manufacturers even when filters with similar costs were compared. The order of filter brands with respect to leucocyte removal found was Pall BPF4 = Erypur Optima G-O > Sepacell R500 > Pall RC50. Phenotyping revealed that increasing filtration efficacy was associated with a preferential removal of lymphocytes; conversely, a second filtration over one brand of filter allowed proportionately more lymphocytes to pass through compared with the first filtration. A saline wash following filtration removed a further 0.5% of the initial leucocyte content, and was associated with a preferential loss of granulocytes. Freeze-thawing the red cell suspension removed fewer leucocytes (96.3%) than did filtration (98.74% to > 99.6%) or filtration followed by washing (99.22%), and also led to preferential loss of granulocytes. Flow cytometry provides a reliable tool for the quality control of leuco-depleted red cells, and allows a qualitative assessment of the residual leucocytes. This information is of value in choosing procedures aimed at decreasing the risk of alloimmunisation and post-transfusion reactions.

Cell Separation↗
PubMed1994

Fibroblast growth factor and cyclic AMP (cAMP) synergistically activate gene expression at a cAMP response element.

Growth factors and cyclic AMP (cAMP) are known to activate distinct intracellular signaling pathways. Fibroblast growth factor (FGF) activates ras-dependent kinase cascades, resulting in the activation of MAP kinases, whereas cAMP activates protein kinase A. In this study, we report that growth factors and cAMP act synergistically to stimulate proenkephalin gene expression. Positive synergy between growth factor- and cAMP-activated signaling pathways on gene expression has not been previously reported, and we suggest that these synergistic interactions represent a useful model for analyzing interactions between these pathways. Transfection and mutational studies indicate that both FGF-dependent gene activation and cAMP-dependent gene activation require cAMP response element 2 (CRE-2), a previously characterized cAMP-dependent regulatory element. Furthermore, multiple copies of this element are sufficient to confer FGF regulation upon a minimal promoter, indicating that FGF and cAMP signaling converge upon transcription factors acting at CRE-2. Among many different ATF/AP-1 factors tested, two factors, ATF-3 and c-Jun, stimulate proenkephalin transcription in an FGF- or Ras-dependent fashion. Finally, we show that ATF-3 and c-Jun form heterodimeric complexes in SK-N-MC cells and that the levels of both proteins are increased in response to FGF but not cAMP. Together, these results indicate that growth factor- and cAMP-dependent signaling pathways converge at CRE-2 to synergistically stimulate gene expression and that ATF-3 and c-Jun regulate proenkephalin transcription in response to both growth factor- and cAMP-dependent intracellular signaling pathways.

Activating Transcription Factor 2↗
PubMed1994

Activating transcription factor-3 stimulates 3',5'-cyclic adenosine monophosphate-dependent gene expression.

Activating transcription factor-3 (ATF-3) is one member of a large family of leucine zipper transcription factors which bind to promoters responsive to cAMP and phorbol ester at the related cAMP (CRE) and phorbol ester response elements. We report here that ATF-3 is coexpressed with the neuropeptide precursor proenkephalin in human neuroblastoma SK-N-MC cells. Cotransfection experiments indicate that activation of proenkephalin gene expression by ATF-3 is dependent upon both the catalytic subunit of the cAMP-dependent protein kinase and the CRE-2 element. The CRE-2 element is essential for second messenger-inducible expression and is known to bind AP-1-like transcription factors. ATF-3 expressed in bacteria or from rabbit reticulocyte lysates binds to the proenkephalin CRE-2 element as a homodimer and as a heterodimer with Jun-D, another activator of proenkephalin transcription. ATF-3 stimulates binding of Jun-D to the proenkephalin CRE-2 element and acts synergistically with Jun-D to induce proenkephalin gene expression. Sequential immunoprecipitations of ATF-3 from SK-N-MC cells expressing proenkephalin indicate that ATF-3 is complexed with Jun-D in vivo and that both proteins are highly phosphorylated. Together, our results suggest that ATF-3 may play an important role in the regulation of gene expression by cAMP-dependent intracellular signaling pathways.

Activating Transcription Factor 3↗
PubMed1994

[The value of nuclear morphometry in analysing heterogeneity of grade-II colorectal adenocarcinomas].

A nuclear morphometric analysis was performed on the histologic sections of 39 grade-II, 17 grade-I and 8 grade-II colorectal adenocarcinomas. The parameters selected were nuclear area, nuclear perimeter, nuclear volume and standard deviation of nuclear area. The results showed that grade-II colorectal adenocarcinomas were a group of heterogeneous tumours and they could be divided into various subgroups by nuclear morphometry so that their biological behaviour could be better reflected.

Adenocarcinoma↗
PubMed1993

Ubiquitins revisited: further examples of within- and between-locus concerted evolution.

Ubiquitin genes provide a model for studying the effects of concerted evolution on the evolution of a family of short repeated sequences. Previous work has demonstrated the occurrence of within-locus concerted evolution and raised the question of the effectiveness of between-locus concerted evolution for ubiquitin repeats. In this study comparative analysis of additional nucleotide sequences of ubiquitin tandem repeats provides further details of within-locus concerted evolution. Moreover, the availability of multiple polyubiquitin loci and ubiquitin fusion loci within a species makes possible the detection of between-locus concerted evolution. These data indicate that concerted evolution is an effective force for homogenizing repeats between, as well as within, loci.

Animals↗
PubMed1993

Trial of oral physostigmine in amyotrophic lateral sclerosis.

We evaluated a double-blind, placebo-controlled, and double-crossover trial of oral physostigmine salicylate for a 9-month period in 13 of 25 patients with sporadic amyotrophic lateral sclerosis (ALS). A large dropout rate of 48% was secondary to eight deaths and four exclusions attributed to the incapability to swallow the tablets (physostigmine) and capsules (lecithin) or to attend the clinic. Parameters used for assessment of the drug efficacy included body weight, ALS score, Jamar grip strength, forced vital capacity, and maximum voluntary ventilation. It revealed slight benefit in reduced loss of grip strength compared with the pretrial and placebo periods. However, the rates of decline for body weight, ALS score, forced vital capacity, maximum voluntary ventilation, and megascore did not differ significantly between the pretrial, placebo, and physostigmine periods. We therefore concluded that overall no significant alteration in the clinical course was gained by oral physostigmine therapy in the 13 patients with ALS who were included in this study.

Administration, Oral↗
PubMed1993

Field evaluation of bednets impregnated with deltamethrin for malaria control.

Trials were undertaken in a hypoendemic area of malaria in an area bordering Vietnam, in Napo County of Guangxi Zhuang Autonomous Region, China. The aim was to compare the relative cost effectiveness of DDT residual spraying and of bednets impregnated with deltamethrin in the malaria control program. The trials were divided into three subgroups: (1) two farming areas and one coal mining area with a total population > 20,000, where the trial consisted of mass bednets impregnated with deltamethrin 15 mg/m2 net surface once a year, (2) one farming area with a population of approximately 3,600 where DDT residual spraying at 2g/m2 was carried out twice a year in May and August; (3) one farming area and one coal mining village with a population of > 4,000 were used as a control. The malaria vector population consisted mainly of Anopheles minimus and An. anthropophagus with a small contribution from An. sinensis. After bednets were impregnated with deltamethrin the mosquitos resting on the surface of the bednets decreased significantly, although there was less effect on the total vector population. The results showed that malaria incidence decreased significantly both in areas where impregnated bednets were used and in areas where residual spraying was undertaken. The positive IFAT rates of residents who slept under impregnated bednets decreased significantly in farming areas, especially in that area where bednet impregnation as a vector control measure had been undertaken for two years, but there was no change in the IFAT rate in DDT sprayed or control areas.(ABSTRACT TRUNCATED AT 250 WORDS)

Bedding and Linens↗
PubMed1992

Diuretic efficiency of furosemide during continuous administration versus bolus injection in healthy volunteers.

Furosemide delivery rate in the nephron has been reported to be one of the major determinants of diuretic response. In a randomized, crossover double-blind study in eight healthy volunteers, we tested this hypothesis by comparing continuous intravenous infusion of furosemide (infusion rate, 4 mg/hr) during 8 hours after administration of an intravenous loading dose of 8 mg (total dose, 40 mg) with an intravenous bolus injection of 40 mg furosemide. During the study days subjects were rehydrated with isovolumetric amounts of fluid. Mean total urinary volume (Vur), sodium (UNa), potassium, and chloride excretion after 8 and 24 hours were significantly greater after treatment with continuous furosemide infusion when compared with bolus injection, whereas total urinary furosemide excretion showed no differences (Vur bolus versus Vur infusion, 5270 versus 6770 ml/8 hours; UNa bolus versus UNa infusion, 314 versus 430 mmol/8 hours; both p less than 0.001). These findings strongly support the concept of the furosemide delivery rate into the nephron as a determinant of diuretic efficiency.

Adult↗
PubMed1992

Cloning, expression, and nucleotide sequence of a lipase gene from Pseudomonas fluorescens B52.

In this study, we report the cloning and expression of lipase gene from Pseudomonas fluorescens B52, a psychrotrophic spoilage bacterium isolated from refrigerated raw milk. Sequence analysis revealed one major open reading frame of 1,428 nucleotides that was predicted to encode a protein with a molecular weight of 50,241. The predicted enzyme was found to contain an amino acid sequence highly homologous to the putative substrate-binding domain present within all lipases examined to date.

Amino Acid Sequence↗
PubMed1992

Absorption of high dose furosemide (frusemide) in congestive heart failure.

To investigate the influence of the presence of oedema on the pharmacokinetics and pharmacodynamics of furosemide (frusemide) we selected 9 hospitalised patients (mean age 70.3 years, range 59 to 84 years) with severe congestive heart failure (NYHA III to IV) and an assessed amount of peripheral oedema of at least 5 kg. In these patients the absorption of a single oral dose of furosemide 250 mg was studied when their heart failure was decompensated and again, after intensive therapy, when it was clinically compensated. The mean (+/- SEM) weight loss after clinical treatment was 12.0 +/- 2.2 kg. Individual furosemide plasma concentration-time curves could be fitted adequately to a 1-compartment model with 1 first-order absorption and elimination process, in which absorption took place in 2 parts with different lag times. Comparing the decompensated state with the compensated state we did not find significant differences in pharmacodynamics, absorption half-life, elimination half-life, time to peak serum concentration, peak serum concentration itself and area under the plasma concentration-time curve. However, the relative amount of furosemide absorbed in the first fraction was significantly increased after compensation. We conclude that the presence of massive oedema in patients with congestive heart failure has a minor influence on the pharmacokinetics and pharmacodynamics of high dose oral furosemide.

Administration, Oral↗
PubMed1992

Regulation of opioid gene expression: a model to understand neural plasticity.

The recent finding that neurotransmitters and drugs that affect neurotransmission have important influences on gene expression suggests that drug-induced alterations in gene expression may underlie many long-term effects of addictive drugs, for example, dependence and drug-seeking behaviors. These long-term adaptive responses to opiate drugs have been particularly difficult to understand at a mechanistic level. Data presented here indicate that the gene encoding the opioid precursor proenkephalin is highly regulated by neural activity, second-messenger pathways, and PKA. These observations raise the possibility that drugs of abuse (e.g., opiates acting through opiate receptors) may act at the genetic level to modulate the expression of endogenous opiates and that these effects may underlie one component of the brain's long-term adaptive response to exogenous opiates. The transgenic animals described above can be used to investigate opiate drug-induced changes in proenkephalin gene expression, allowing rapid analysis of changes in proenkephalin gene expression in highly restricted populations of neurons in a fashion previously impossible. In addition, by analyzing the effects of specific enhancer mutations on tissue-specific and transsynaptic regulation of proenkephalin expression, transgenic models will permit mechanistic investigations within the intact nervous system that cannot otherwise be undertaken. Investigation of mechanisms underlying this process requires the analysis of intracellular signaling pathways, responsive DNA regulatory elements, and the transcription factors transducing synaptic signals into gene regulation. In the studies described herein, we demonstrate that AP-1 complexes consisting of different Jun proteins differentially regulate proenkephalin transcription at the CRE-2 element. c-Jun constitutively activates proenkephalin transcription, whereas JunD activates in a fashion completely dependent on the activation of second-messenger pathways and the cAMP-dependent PKA. JunB alone has no effect on proenkephalin gene expression, yet this molecule effectively blocks activation mediated by JunD and, hence, may act as a repressor. These data are consistent with a model (figure 4) in which preexisting JunD mediates the rapid cAMP-dependent activation of the proenkephalin enhancer, whereas IEGs such as JunB or c-Fos mediate the protein synthesis-dependent inactivation. Because c-Jun activates proenkephalin transcription constitutively, induction of c-Jun may lead to a further and prolonged activation of proenkephalin gene expression. Hence, the ratio of c-Jun to JunB induction may determine whether proenkephalin is repressed or further activated.

Animals↗
PubMed1991

cAMP-dependent regulation of proenkephalin by JunD and JunB: positive and negative effects of AP-1 proteins.

We demonstrate that JunD, a component of the AP-1 transcription factor complex, activates transcription of the human proenkephalin gene in a fashion that is completely dependent upon the cAMP-dependent protein kinase, protein kinase A. Activation of proenkephalin transcription by JunD is dependent upon a previously characterized cAMP-, phorbol ester-, and Ca(2+)-inducible enhancer, and JunD is shown to bind the enhancer as a homodimer. Another component of the AP-1 transcription complex, JunB, is shown to inhibit activation mediated by JunD. As a homodimer JunB is unable to bind the enhancer; however in the presence of c-Fos, high-affinity binding is observed. Furthermore, JunD is shown to activate transcription of genes linked to both cAMP and phorbol ester response elements in a protein kinase A-dependent fashion, further blurring the distinction between these response elements. These results demonstrate that the transcriptional activity of an AP-1-related protein is regulated by the cAMP-dependent second-messenger pathway and suggest that JunD and other AP-1-related proteins may play an important role in the regulation of gene expression by cAMP-dependent intracellular signaling pathways.

1-Methyl-3-isobutylxanthine↗
PubMed1991

Effects of high erucic acid rapeseed oil on fatty acid oxidation in rat liver.

The effects of high erucic acid rapeseed oil (HER) on fatty acid oxidation in rat liver compared with low erucic acid rapeseed oil (LER) were studied. Weanling male SD rats were fed diets containing 20% HER or LER for 1 week or 4 weeks, or 5% HER diet for 4 weeks. The hepatic oxidation capacity of butyric acid or palmitic acid was determined by titrating the propanone produced by their oxidation. The results showed that feeding HER to rats led to an increase in the weight of liver and a decrease in the hepatic oxidation capacity of palmitic acid. Hepatic oxidation of butyric acid was not influenced by the intake of HER. The inhibitory action of HER on the oxidation of long-chain fatty acids probably resulted from the incorporation of erucic acid into mitochondrial membranes, interfering the fatty acyl-CoA transferring system on the membranes, but not from the beta-oxidation enzyme system in mitochondria being directly inhibited.

Animals↗
PubMed1991

[The role of transmission electron microscopy played in diagnosis of knotty tumors].

Eight cases were reported in order to elucidate the important role of electron microscopy (EM) played in diagnosis of knotty tumors. The diagnosis of tumors made by light microscopy (LM) could be confirmed, corrected or eliminated with EM, and the types and histogenesis of tumors could be decided more accurately with EM than with LM. But EM has its inherent limitations, so it is emphasized that diagnosis made by EM must rest on solid basis of LM, and sometimes EM should be combined with other methods, such as histochemistry and immunohistochemistry.

Child↗