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Biomedical subjects

J Yu

Publications and source records attributed to J Yu.

At least 361 records · Page 20Linked to original sources
PubMed1999

Electrochemical treatment of human KB cells in vitro.

Electrochemical treatment (ECT) of cancer is a promising new method by which direct current is delivered into tumor tissue to induce tumor regression. The purpose of this study is to evaluate the effectiveness of ECT on human cancer cells and to investigate the factors that affect ECT. The biological mechanisms of ECT in cancer treatment were also explored. Using human KB cells, ECT was found to delay cell growth by using 0.3 coulombs (C)/ml (1.5 C in 5 ml of culture medium; 3 V, 400 microA for 62.5 min). From the results of a colony-forming assay, it was clearly demonstrated that increasing the ECT dose decreases tumor cell survival. A cytotoxicity study, in which a methylene blue assay was used, determined that, for 2.5 x 10(5) cells in culture, the 1D50 was 0.68 C/ml. For a fixed dose of 0.6 C/ml (3 C in 5 ml), using higher current and shorter treatment time resulted in better cell survival. Time, therefore, is an important factor. When cell concentration was altered, the survival was higher for increased cell concentrations. A thymidine incorporation assay indicated that the amount of [3H]thymidine incorporated into DNA decreased as the ECT dose increased. After treatment with 1 C/ml (5 C in 5 ml; 3 V, 400 microA for 208.4 min), pH at the anode decreased to 4.53 and at the cathode increased to 10.46. These results indicate that ECT is effective for killing human KB cells in vitro and that the toxicity effect is related to charge, current, and treatment time. The effect of pH alteration on cells is one of the mechanisms of ECT.

Cell Division↗
PubMed1999

Functional and biochemical characterization of a novel human macrophage-derived negative regulator of haematopoiesis.

It is believed that haematopoiesis is regulated by both positive and negative signals derived from the marrow microenvironment, which includes macrophages. The identity and mechanism of action of the proteins mediating negative regulation is an area of active investigation. We report here the identification and initial characterization of a novel suppressor of early haematopoietic progenitors, designated NRH (for Negative Regulator of Haematopoiesis), isolated from the recently established human macrophage line 2MAC. The mechanism of NRH suppression appears to involve a marked decrease in the cycling of early progenitor cells. NRH activity was shown to be reversible and to correspond to an acidic, heparin-binding glycoprotein with a molecular weight of approximately 20 000 daltons ( approximately 20 kDa). By exploiting lectin specificity, hydrophobic interaction, and heparin affinity, we have developed a procedure for the rapid isolation of highly purified NRH from 2MAC-conditioned medium. By a number of functional and biochemical criteria, NRH appears to represent a novel macrophage-derived negative regulator of haematopoiesis which may have future application in certain clinical settings as a chemoprotectant of primitive haematopoietic cells.

Cell Line↗
PubMed1999

Food plant-delivered cholera toxin B subunit for vaccination and immunotolerization.

Developments in recombinant DNA technology have enabled molecular biologists to introduce a variety of novel genes into plant species for specific purposes. From crop improvement to vaccine antigen and antibody production, plants are attractive bioreactors for production of recombinant proteins, as their eukaryotic nature often permits appropriate post-translational modification of recombinant proteins to retain native biological activity. The autotrophic growth of plants requires only soil minerals, water, nitrogen, sunlight energy and carbon dioxide for the synthesis of constituent proteins. Furthermore, production of biologically active proteins in food plants provides the advantage of direct delivery through consumption of edible transformed plant tissues. The production of cholera toxin B subunit in potato plants and applications for prevention of infectious and autoimmune disease are explained in this contribution.

Animals↗
PubMed1999

Systemic effects of E-2078, a stabilized dynorphin A(1-8) analog, in rhesus monkeys.

RATIONALE: E-2078 ([N-methyl-Tyr1, N-methyl-Arg7, D-Leu8] dynorphin A(1-8) ethylamide) is a dynorphin A(1-8) analog with a reduced tendency to be biotransformed, when compared to the unmodified opioid peptide. E-2078 has been found to produce kappa-opioid agonist effects in vivo in rodents. OBJECTIVE: In the present studies, we investigated whether systemically administered E-2078 could produce kappa-agonist effects in rhesus monkeys, in tests of antinociception, diuresis and ethyl-ketocyclazocine (EKC) discrimination. METHODS: E-2078 (0.32-18 mg/kg, SC, IM or IV) was tested in the warm water (50 degrees, 55 degrees C) tail withdrawal assay of thermal antinociception. The diuretic effects of E-2078 (0.056-1.8 mg/kg, SC) were also compared to those of the kappa-agonist, U69,593 (0.01-0.32 mg/kg, SC). Lastly, the effects of E-2078 (0.1-3.2 mg/kg, SC or IV) were studied in rhesus monkeys trained to discriminate EKC (0.0056 mg/kg SC) from vehicle, in a food-reinforced operant procedure. RESULTS: E-2078 did not produce thermal antinociception in rhesus monkeys following SC or IM administration, up to the largest doses presently studied (i.e., 18 and 10 mg/kg, respectively). E-2078 caused thermal antinociception by the IV route, but this effect was not apparently mediated by kappa- or mu-opioid receptors, as shown by its insensitivity to quadazocine (1 mg/kg) pretreatment. However, SC E-2078 caused diuresis, and this effect was blocked by quadazocine pretreatment, consistent with mediation by kappa-opioid receptors. E-2078 generalized in EKC-discriminating monkeys, but only after the largest dose (3.2 mg/kg), and only following IV administration. CONCLUSIONS: The present studies suggest that systemically administered E-2078 can produce some kappa-receptor mediated effects in rhesus monkeys, but its profile of action is not identical to non-peptidic kappa-agonists following all routes of administration, or across all experimental situations.

Analgesics, Non-Narcotic↗
PubMed1999

The nucleotide sequence of a chinese isolate of wheat yellow mosaic virus and its comparison with a Japanese isolate. Brief report.

The nucleotide sequences of wheat yellow mosaic virus isolated in China were determined and compared with a Japanese isolate of the same virus. Results showed that the viral genome had 7629 nucleotides for RNA1 and 3639 nucleotides for RNA2, which shared 97. 1% and 94.6% of identities to the RNAs of Japanese isolate. The single open reading frames in RNA1 and RNA2 encoded polyproteins with 2407 amino acids and 903 amino acids respectively, from which ten proteins may be produced by autolytic cleavage processing as the Japanese isolate. Since the sequence of WYMV RNA1 showed identity of less than 70% with that of WSSMV, it is further confirmed that WYMV is a distinct species within Bymovirus.

Base Sequence↗
PubMed1999

Treatment of recurrent conjunctival papillomatosis with mitomycin C.

PURPOSE: To report an effective treatment for recurrent squamous papillomas of the conjunctiva with excision and application of mitomycin C. METHOD: Case report. RESULTS: A 5-year-old African-American girl with recurrent squamous papillomas of the right bulbar and palpebral conjunctiva was treated with multiple therapies, including excision, cryotherapy, and conjunctival injection of alpha-interferon; all therapies were followed by recurrence. After treatment with excision followed by intraoperative application of mitomycin C to the involved conjunctiva, the patient had no recurrence in a 30-month period. CONCLUSIONS: Excision with application of mitomycin C was successful in managing a case of squamous papillomatosis that was resistant to traditional therapy.

Antibiotics, Antineoplastic↗
PubMed1999

Growth during maintenance hemodialysis: impact of enhanced nutrition and clearance.

Growth of children during maintenance hemodialysis has been reported to be uniformly poor, with a mean annual loss of 0.4 to 0.8 SD in height. We adopted an intensive program of closely monitored energy and protein intake with dialysis urea clearances exceeding conventional recommendations. Twelve prepubertal or early pubertal children (aged 7 months to 14 years) were monitored for an average of 2.2 years (range 4 to 81 months) while receiving maintenance hemodialysis. These children received an average of 90.6% and 155.9% of their recommended energy and protein nutritional intake, respectively. With a prescribed urea clearance of 5 mL/kg/min, we achieved a mean single treatment urea clearance normalized for total body water of 2.00, a urea reduction ratio of 84.7%, and an average time of hemodialysis of 14.8 h/wk, all well beyond current guidelines. Over the course of dialysis treatment, the improvement in height SD score was+0.31 SD/y (+0.32 excluding the 2 children treated with recombinant human growth hormone). Normal growth was achieved without overt obesity and was associated with normal pubertal growth spurt. These findings suggest that the combination of increased dialysis and adequate nutrition can promote normal growth in children treated with long-term hemodialysis.

Adolescent↗
PubMed1999

Exercise intolerance in patients with chronic heart failure and increased expression of inducible nitric oxide synthase in the skeletal muscle.

OBJECTIVES: This study was designed to analyze the effect of iNOS on mitochondrial creatine kinase (mi-CK) expression and exercise capacity in chronic heart failure (CHF). BACKGROUND: The molecular mechanisms underlying exercise intolerance in CHF are still unclear. Expression of inducible nitric oxide synthase (iNOS) and reduced phosphocreatine resynthesis have been described in skeletal muscle of patients with CHF. However, it is unknown whether these phenomena are causally related to each other and to exercise tolerance. METHODS: Thirty-eight patients with CHF and 8 healthy controls (C) underwent bicycle ergospirometry and biopsy of the vastus lateralis muscle. Expression of iNOS was quantified by immunohistochemistry and reverse-transcriptase polymerase chain reaction, mi-CK by Western-blot. Intracellular presence of NO was confirmed by immunohistochemical quantification of nitrotyrosine (NT). To corroborate clinical findings, L6 rat skeletal myoblasts were incubated with sodium nitroprusside (SNP). RESULTS: Expression of iNOS was significantly increased in CHF (4.0+/-2.8 vs. 0.8+/-0.7% iNOS positive tissue area, p < 0.001 vs. C) and inversely correlated to maximal oxygen uptake (r=-0.65, p < 0.001). Intracellular NO-accumulation was confirmed by increased NT levels (13.5+/-8.5 vs. 2.0+/-1.7% NT-positive tissue area, p < 0.001 vs. C). Mi-CK was decreased in CHF (0.84+/-0.36 vs. 1.57+/-0.60, p < 0.001 vs. C). The inverse correlation seen between iNOS and mi-CK expression in patients (r=-0.68, p < 0.001) was reproduced in incubation experiments with SNP. CONCLUSIONS: Increased expression of iNOS in skeletal muscle of patients with CHF was inversely correlated with mi-CK expression and exercise capacity. Cell experiments confirmed a causal relationship via NO. These findings extend our knowledge of the pathophysiology of exercise intolerance in CHF.

Aged↗
PubMed1999

Synthesis and MAO-B substrate properties of 1-methyl-4-heteroaryl-1,2,3,6-tetrahydropyridines.

The parkinsonian inducing drug 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is bioactivated in a reaction catalyzed by the flavoenzyme monoamine oxidase B (MAO-B) to form the corresponding dihydropyridinium and subsequently pyridinium metabolites. As part of our ongoing studies to characterize the structural features responsible for this unexpected biotransformation, we have examined the MAO-B substrate properties of a variety of MPTP analogues bearing various heteroaryl groups at the 4-position of the tetrahydropyridinyl ring. The newly synthesized analogues are 4-(1-methylimidazol-2-yl)-, 4-(3-methylfuran-2-yl)-, 4-(3-methylthien-2-yl)-, 4-(3,4-dimethylpyrrol-1-yl)-, 4-(3-methylpyrrol-2-yl)-, and 4-(1,3-dimethylpyrrol-2-yl)-1-methyl-1,2,3,6-tetrahydropyridine. Except for the 4-(1-methylimidazol-2-yl) analogue, all compounds displayed good to excellent substrate properties. The 1-methyl-4-(3-methylfuran-2-yl) analogue is the most active member of this series with a kcat/Km value greater than 8,500 min(-1)mM(-1). The results of these studies are discussed in terms of catalytic pathways proposed for MAO-B.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1999

Synthesis and monoamine oxidase B substrate properties of 1-methyl-4-heteroaryl-1,2,3,6-tetrahydropyridines.

Six analogues of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine [MPTP, (1)] bearing various heteroaryl groups at C-4 were synthesized and examined for their monoamine oxidase B substrate properties. The C-4 substituents include the 1-ethylpyrrol-2-yl, 1-propylpyrrol-2-yl, 1-isopropylpyrrol-2-yl, 1-cyclopropylpyrrol-2-yl, 3-ethylfuran-2-yl and 3-ethylthien-2-yl groups. The results provide information concerning steric and polar interactions between the C-4 substituent and the active site of MAO-B that are transmitted to the position of oxidation at C-6 of the tetrahydropyridinyl moiety.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1999

DsbA: a protein-folding catalyst contributing to bacterial virulence.

DsbA, a periplasmic thiol:disulphide oxidoreductase, catalyses the folding of various factors, among which are virulence determinants or the components of type III secretory machinery. It is also necessary for intracellular survival and cell-to-cell spread of the intracellular pathogen Shigella flexneri.

Animals↗
PubMed1999

Repressor-AFLR interaction modulates aflatoxin biosynthesis in Aspergillus parasiticus.

Regulation of aflatoxin (AF) biosynthesis likely involves a complex interplay of positive- and negative-acting factors that are affected by physiological cues responsive to internal and external stimuli. These factors, presumably, modulate the expression of the AF pathway-specific regulatory gene, aflR, whose product, AFLR, a zinc cluster transcription factor, then turns on or off the transcription of other AF genes. To determine if the AFLR carboxyl region (AFLRC) interacts with positive- or negative-acting proteins, we fused the Aspergillus parasiticus aflR carboxyl coding region (aflRC) to the promoter of A. parasiticus nitrite reductase gene (niiA(p)::aflRC), and transformed it into A. parasiticus SRRC 2043. Transformants that contained two copies of niiA(p)::aflRC, one at the niaD locus and another at the aflR locus, overproduced AF precursors independent of the nitrogen source. The higher copy number of the integrated niiA(p)::aflRC correlated with increased production of AF precursors by the transformants as well as increased expression of both aflRC and native aflR in potato dextrose broth and A&M medium. Since aflRC does not encode a DNA-binding domain, the expressed AFLRC should not bind to the promoters of AF pathway genes and affect transcription directly. The results are consistent with AFLRC titrating out a putative repressor that interacts with AFLR under different growth conditions and modulates AF biosynthesis. This interaction also indirectly affects sclerotial development.

Aflatoxins↗
PubMed1999

The components of an inorganic physiological buffer for Penaeus chinensis.

Shrimp Penaeus chinensis, 5--8 cm in body-length were held in laboratory aquaria after collection from culture ponds at Laoshan in Qingdao in 1992. The osmotic pressure and the concentration of inorganic components of hemolymph in the shrimp were measured. The optimum pH and osmolarity of the buffer were determined from tests on primary cultures of hepatopancreatocytes in vitro. The results indicate that the hemolymph is homoiosmotic to 27 ppt seawater at 870 mOsm/L; osmotic regulation of shrimp is strong in low-salinity seawater, but weak in high-salinity seawater; the concentration of Mg(2+) ions in hemolymph is much less than that in seawater, while [K(+)] and [Ca(2+)] are much higher; hepatopancreatocytes in vitro have optimal survival at osmolarity range of 780-1, 100 mOsm/L and pH 6.5. Accordingly, an inorganic physiological buffer for P. chinensis (PPB, Penaeid Physiological Buffer) was prepared and contains NaCl, 23.0 g/L; K(2)SO(4), 1.1 g/L; CaCl(2), 1.6 g/L; MgSO(4).7H(2)O, 1.6 g/L; NaH(2)PO(4).2H(2)O, 0.35 g/L; NaHCO(3), 0. 05 g/L; pH 6.5; osmolarity, 867.9 mOsm/L. For storage of PPB, 4 stock buffers are made: 1) 10x PPB-A, which contains 230 g/L NaCl, 11 g/L K(2)SO(4), and 3.5 g/L NaH(2)PO(4).2H(2)O; 2) 40x PPB-B, which contains 64 g/L MgSO(4).7H(2)O; 3) 40x PPB-C, which contains 64 g/L CaCl(2); and 4) 100x PPB-D, which contains 50 g/L NaHCO(2). In order to increase the buffering capacity, PPB may be modified (to His-PPB), in which 5 g/L Histidine.HCl is used as the buffer reagent in place of NaH(2)PO(4) and NaHCO(3).

Animals↗