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Biomedical subjects

Z Liu

Publications and source records attributed to Z Liu.

At least 1,081 records · Page 60Linked to original sources
PubMed1995

Development of bovine embryos in KSOM with added superoxide dismutase and taurine and with five and twenty percent O2.

To further define requirements for embryo development without the assistance of complex media, serum, or coculture, the effects of 5% and 20% O2 concentrations, superoxide dismutase (SOD) (experiment 1), and taurine (experiment 2) were tested in a single culture medium (KSOM modified with 2.5 mM HEPES). Bovine embryos were produced in vitro maturation (IVM) and in vitro fertilization (IVF) of oocytes. After fertilization, embryos were cultured in 5% O2:5% CO2:90% N2 at 30 degrees C for the first 40-44 h; then embryos with 4 to 8 cells were cultured in different treatments for another 6 days. Percentage development subsequently was based on this number. In experiment 1, more blastocysts were produced in 5% O2:5% CO2:90% N2 (37%) than in 20% O2:5% CO2:75% N2 (18%; p < 0.01). Blastocyst development with 0, 300, and 600 U/ml of SOD, respectively, was 26%, 26%, and 30% (p > 0.05). In experiment 2, more blastocysts were formed in 5% O2 (39%) than in 95% air (30%; p < 0.05). Also, with 20% O2 and 0, 7, and 14 mM taurine in the medium, blastocyst formation was 18%, 35%, and 36% (p < 0.05). However, in 5% O2, 7 and 14 mM taurine was not beneficial (p = 0.99), as 39% blastocysts were formed with no taurine. In conclusion, results from both experiments demonstrated that 5% O2 was superior to 20% O2 for development of IVM/IVF bovine embryos. SOD had no effect in either 5% or 20% O2. However, 7 mM and 14 mM taurine counteracted the negative effect of 20% O2.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Demonstration of tissue-specific promoters in nonprimate species that express aromatase P450 in placentae.

Conversion of androgens to estrogens is catalyzed by aromatase P450 (P450arom; the product of the CYP19 gene). Regulation of tissue-specific expression of P450arom in humans is due, in part, to alternative transcriptional start sites that arise as a consequence of the use of granulosa cells and placental tissue from cows, horses, and pigs (ungulates) in order to determine whether these species, like the human, utilize tissue-specific promoters to drive P450arom expression. The majority of transcripts in the placenta have 5'-termini that differ from those in the ovary upstream of a common site of divergence, indicative of a splice junction. The use of tissue-specific promoters by the bovine CYP19 gene would produce these results, as it does in the case of the human CYP19 gene. A bovine genomic library was then screened with probes that hybridize to ovary- or placenta-specific transcripts. Two clones of approximately 15 kb each in length were isolated; one hybridized with the ovary-specific sequence and the other hybridized with the placenta-specific sequence. Whereas the former sequence was contiguous with the downstream sequence containing the translational start site, the latter was identical only with the sequence of the placental transcripts upstream of the putative splice junction, indicating that this was the distal sequence. Bovine and human ovary-specific genomic sequences share 77% bp identity, while bovine and human placenta-specific sequences demonstrated only 39% bp identity. These results mirror those obtained in comparisons of human, bovine, equine, and porcine ovarian and placental RACE cDNA 5'-termini.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Evidence for a role of cytochrome P450 2D6 and 3A4 in ethylmorphine metabolism.

Ethylmorphine is metabolised by N-demethylation (to norethylmorphine) and by O-deethylation (to morphine). The O-deethylation reaction was previously shown in vivo to co-segregate with the O-demethylation of dextromethorphan indicating that ethylmorphine is a substrate of polymorphic cytochrome P450(CYP)2D6. To study further the features of ethylmorphine metabolism we investigated its N-demethylation and O-deethylation in human liver microsomes from eight extensive (EM) and one poor metaboliser (PM) of dextromethorphan. Whereas N-demethylation varied only two-fold there was a 4.3-fold variation in the O-deethylation of ethylmorphine, the lowest rate being observed in the PM. Quinidine, at a concentration of 1 microM, inhibited O-deethylation in microsomes from an EM, but was unable to do so in microsomes from the PM. The immunoidentified CYP2D6 and CYP3A4 correlated with the rates of O-deethylation (r = 0.972) and N-demethylation (r = 0.969), respectively. We conclude that the O-deethylation of ethylmorphine is catalysed by the CYP2D6 in human liver microsomes consistent with previous findings in healthy volunteers.

Adult↗
PubMed1995

A novel amber mutation in a beta zero-thalassaemia gene (beta 37TGG-->TAG), with direct detection by mapping the restriction fragments in amplified genomic DNA.

A novel amber mutation, a G to A substitution at the second position of codon 37 in the beta-globin gene that changes the tryptophan coding triplet (TGG) to a termination codon (TAG), was found in a Chinese beta-thalassaemia carrier. The mutant gene creates an additional Dde I recognition site and eliminates the Ava II site, so this point mutation can be directly identified by restriction enzyme analysis.

Adult↗
PubMed1995

Biodegradation of naphthalene in aqueous nonionic surfactant systems.

The principal objective of this study was to quantify the bioavailability of micelle-solubilized naphthalene to naphthalene-degrading microorganisms comprising a mixed population isolated from contaminated waste and soils. Two nonionic surfactants were used, an alkylethoxylate, Brij 30 (C12E4), and an alkylphenol ethoxylate, Triton X-100 (C8PE9.5). Batch experiments were used to evaluate the effects of aqueous, micellized nonionic surfactants on the microbial mineralization of naphthalene and salicylic acid, an intermediate compound formed in the pathway of microbial degradation of naphthalene. The extent of solubilization and biodegradation under aerobic conditions was monitored by radiotracer and spectrophotometric techniques. Experimental results showed that surfactant concentrations above the critical micelle concentration were not toxic to the naphthalene-degrading bacteria and that the presence of surfactant micelles did not inhibit mineralization of naphthalene. Naphthalene solubilized by micelles of Brij 30 or Triton X-100 in liquid media was bioavailable and degradable by the mixed culture of bacteria.

Bacteria↗
PubMed1995

Unidirectional motility of Escherichia coli in restrictive capillaries.

In a 6-microns capillary filled with buffer and in the absence of any chemotactic stimuli, Escherichia coli K-12 cells swim persistently in only one direction. This behavior of E. coli can be simply explained by means of the length and relative rigidity of their flagella. Single-cell motility parameters--swimming speed, turn angle, and run length time--were measured. Compared with the motility parameters measured in bulk phase, turn angle was influenced because of the effect of the geometrical restriction.

Chemotaxis↗
PubMed1995

Role of interleukin-6 in T-cell activation during primary and secondary infection with Listeria monocytogenes.

Injection of recombinant interleukin-6 (IL-6) into mice enhances recovery from infection with Listeria monocytogenes. In this study, the role of IL-6 during primary and secondary Listeria infection was further tested. Neutralization of IL-6 by polyclonal antibody exacerbated primary infection and significantly delayed gamma interferon production by cultured spleen cells. In contrast, administration of anti-IL-6 antibody at the time of secondary infection did not affect the recovery of mice from infection or gamma interferon production, showing that activated T cells are not dependent on IL-6.

Animals↗
PubMed1995

Action of insulin on Na(+)-K(+)-ATPase and the Na(+)-K(+)-2Cl- cotransporter in 3T3-L1 adipocytes.

The Na(+)-K(+)-ATPase presents several different isoforms of its alpha- and beta-subunits. We detected alpha 1- and beta 1-mRNA transcripts and polypeptides in 3T3-L1 fibroblasts; during differentiation into adipocytes, alpha 1-mRNA decreased, alpha 2-mRNA was induced, beta 1-mRNA dropped to undetectable levels, and beta 2-mRNA was never expressed, suggesting that 3T3-L1 adipocytes may express an unidentified Na(+)-K(+)-ATPase beta-subunit isoform. Insulin rapidly increased ion pump activity [ouabain-sensitive 86Rb+(K+) uptake] in 3T3-L1 fibroblasts and adipocytes without changing the plasma membrane concentration of alpha 1- or alpha 2-subunits as determined by subcellular membrane fractionation and immunoblotting or by [3H]ouabain binding to intact cells. Monensin, which raises the concentration of intracellular Na+, increased Na(+)-K+ pump activity, and no further stimulation was achieved with insulin. The stimulation of the pump by insulin was reduced by bumetanide, an inhibitor of the Na(+)-K(+)-2Cl- cotransporter, and was prevented by omission of extracellular Cl-. Insulin increased both ouabain-sensitive and bumetanide-sensitive 86Rb+(K+) uptake. These results suggest that insulin activation of the Na(+)-K(+)-ATPase in 3T3-L1 adipocytes is mediated by an elevation in intracellular Na+ that is likely the consequence of Na(+)-K(+)-2Cl- cotransporter activation.

Adipocytes↗
PubMed1995

Mapping of the gene for hormone sensitive lipase (LIPE) to chromosome 19q13.1-->q13.2.

Free fatty acids are the major source of fuel for mammals, and hormone sensitive lipase (LIPE) plays a critical role in lipid metabolism by mobilizing free fatty acids from stored triglycerides. We have identified and sequenced a partial cDNA for LIPE. Cosmids were identified by hybridization and mapped to 19q13.1-->q13.2 by FISH. Direct sequence analysis of a 1 kb segment of cosmid 26710 identifies a dinucleotide repeat in an intron upstream of exon 8 of human LIPE. This marker was heterozygous 82% of the time with 12 alleles (166-190 bp) detected in 122 chromosomes. The most likely order for this gene is: qter-[D19S178/LIPE]-(3 cM)-D19S47-(1 cM)-D19S190-RYR1-cen.

Alleles↗
PubMed1995

The role of complement in experimental bullous pemphigoid.

Bullous pemphigoid (BP) is a blistering skin disease associated with an IgG autoimmune response directed against the ectodomain of the hemidesmosomal protein, BP180. An animal model of BP has recently been developed by our laboratory based on the passive transfer of rabbit antimurine BP180 antibodies into neonatal BALB/c mice. The experimental animals develop a blistering disease that reproduces all of the key immunopathological features of BP. In the present study we have investigated the role of complement in the pathogenesis of subepidermal blistering in the mouse model of BP. We demonstrate the following. (a) Rabbit anti-murine-BP180 IgG was effective in inducing cutaneous blisters in a C5-sufficient mouse strain, but failed to induce disease in the syngeneic C5-deficient strain; (b) neonatal BALB/c mice, pretreated with cobra venom factor to deplete complement, became resistant to the pathogenic effects of the anti-BP180 IgG; (c) F(ab')2 fragments generated from the anti-BP180 IgG exhibited no pathogenic activity in the mouse model; and (d) histologic evaluation of the skin of mice described in points b and c above showed minimal or no neutrophilic cell infiltration in the upper dermis. Thus, anti-BP180 antibodies trigger subepidermal blistering in this BP model via complement activation. This experimental model of BP should greatly facilitate future studies on the pathophysiology of autoantibody-mediated diseases of the dermal-epidermal junction.

Animals↗
PubMed1995

Revascularization of a salvage supraglottic laryngectomy. Preliminary report.

After supraglottic laryngectomy, particularly if there has been a large preoperative dose of radiotherapy, significant ischemia at the suspension anastomosis site may ensue. Neovascularization may play a major role in the healing of this salvage horizontal laryngectomy anastomosis. We have analyzed the process of angiogenesis and neovascularization from a fascial flap in a case of salvage supraglottic laryngectomy.

Adult↗
PubMed1995

Control of insulin-like growth factor-II/mannose 6-phosphate receptor gene transcription by proximal promoter elements.

The insulin-like growth factor-II/cation-independent mannose 6-phosphate receptor (IGF-II/MPR) is a multifunctional protein that binds IGF-II and ligands containing a mannose 6-phosphate recognition marker. Recent studies have shown that this receptor plays a critical role in mammalian development, and that its expression is controlled by both epigenetic and tissue-specific factors. Our laboratory has cloned the 93-kilobase mouse gene and characterized its 48 exons. In this report we describe the structure and function of the IGF-II/MPR gene promoter. To study promoter function, a series of chimeric plasmids linking different segments of IGF-II/MPR 5' flanking DNA to the reporter gene, firefly luciferase, were transiently transfected into HepG2 and C3H 10T1/2 cells. Promoter activity was orientation-specific and was maximal (550- to 4250-fold above promoterless control) with a plasmid containing 266 base pairs (bp) of IGF-II/MPR DNA. The fusion gene accurately directed transcription as measured by ribonuclease protection assay using RNA extracted from transfected cells. DNA-protein binding studies by in vitro DNase I footprinting revealed an extended 54-bp footprint within the proximal promoter that contained two E-boxes and potential binding sites for transcription factors Sp1, NGF-IA, and related proteins. Gel mobility shift experiments with double-stranded oligonucleotides containing this region gave rise to several specific DNA-protein complexes, and the addition of specific antibodies indicated that proteins antigenically related to Sp1 and c-Myc were components of one or more of these bands. Deletion of this 54-bp segment led to an 8-fold decline in promoter activity, and its transfer to a heterologous promoter stimulated gene expression by nearly 7-fold. Mutational analyses indicated that each E box contributed to more than half of the enhancer's activity. These results define a strong minimal IGF-II/MPR promoter of no more than 266 bp and identify a 54-bp enhancer within this promoter fragment. Our observations thus represent a first step toward characterizing the developmental, epigenetic, and tissue-specific factors that control IGF-II/MPR gene expression.

Amino Acid Sequence↗
PubMed1995

LEUNIG regulates AGAMOUS expression in Arabidopsis flowers.

LEUNIG was identified in a genetic screen designed to isolate second-site enhancer mutations of the floral homeotic mutant apetala2-1. leunig mutations not only enhance apetala2, but by themselves cause a similar but less-pronounced homeotic transformation than apetala2 mutations. leunig flowers have sepals that are transformed toward stamens and carpels, and petals that are either staminoid or absent. In situ hybridization experiments with leunig mutants revealed altered expression pattern of the floral homeotic genes APETALA1, APETALA3, PISTILLATA, and AGAMOUS. Double mutants of leunig and agamous exhibited a phenotype similar to agamous single mutants, indicating that agamous is epistatic to leunig. Our analysis suggests that a key role of LEUNIG is to negatively regulate AGAMOUS expression in the first two whorls of the Arabidopsis flower.

Arabidopsis↗
PubMed1995

The Caenorhabditis elegans heterochronic gene pathway controls stage-specific transcription of collagen genes.

In Caenorhabditis elegans, the terminal differentiation of the hypodermal cells occurs at the larval-to-adult molt, and is characterized in part by the formation of a morphologically distinct adult cuticle. The timing of this event is controlled by a pathway of heterochronic genes that includes the relatively direct regulatory gene, lin-29, and upstream genes lin-4, lin-14 and lin-28. Using northern analysis to detect endogenous collagen mRNA levels and collagen/lacZ reporter constructs to monitor collagen transcriptional activity, we show that the stage-specific switch from larval cuticle to adult cuticle correlates with the transcriptional activation of adult-specific collagen genes and repression of larval-specific collagen genes. Heterochronic mutations that cause precocious formation of adult cuticle also cause precocious transcription of the adult-specific collagen genes, col-7 and col-19; heterochronic mutations that prevent the switch to adult cuticle cause continued expression of the larval collagen gene, col-17, in adults and prevent adult-specific activation of col-7 or col-19. A 235 bp segment of col-19 5' sequences is sufficient to direct the adult-specific expression of a col-19/lacZ reporter gene in hypodermal cells. These findings indicate that the heterochronic gene pathway regulates the timing of hypodermal cell terminal differentiation by regulating larval- and adult-specific gene expression, perhaps by the direct action of lin-29.

Animals↗
PubMed1995

Radiofrequency catheter ablation for atrioventricular node reentry tachycardia with multiple slow atrioventricular node pathways.

Catheter ablation was attempted in 2 patients with atrioventricular node reentry tachycardia which showed fast, intermediate and slow anterograde atrioventricular node pathways. Radiofrequency currents were applied within a restricted area of the tricuspid annulus between the His bundle and the ostium of the coronary sinus where presumed slow pathway potentials were identified. Elimination of both the intermediate and the slow pathways, with preservation of anterograde and retrograde fast pathway conduction, was achieved in both patients.

Aged↗
PubMed1995

Comparison of the end-tidal arterial PCO2 gradient during exercise in normal subjects and in patients with severe COPD.

We undertook the present study with the following objectives: (1) to compare the difference between the end-tidal and the arterial carbondioxide concentration (P[ETa] CO2) gradients at rest and during exercise in normal subjects and patients with COPD; and (2) to analyze the factors contributing to this gradient. We studied seven normal subjects and seven patients with COPD using a symptom-limited exercise test on a cycle ergometer. Our results show that the P(ET-a)CO2 increased progressively as the individuals went from rest to higher workloads in both the normal group and in the COPD group. The P(ET-a)CO2 in patients with COPD both at rest (-3.24 +/- 2.78 mm Hg) and during exercise (1.03 +/- 2.23 mm Hg) is significantly lower than that in normal individuals at rest (1.84 +/- 3.68 mm Hg) and during exercise (10.3 +/- 6.5 mm Hg) (p < 0.01). However, the slope for the relationship between the P(ET-a)CO2 and the workload is actually significantly steeper in the patients with COPD. Although the P(ET-a)CO2 correlated significantly with the workload in both normal subjects (r = 0.63, p < 0.001) and patients (r = 0.55, p < 0.005), the P(ET-a)CO2 was much more closely correlated with the ratio of dead space to tidal volume (VD/VT) (r values of -0.86 and -0.77, respectively). Moreover, when multiple regression analysis was performed, addition of any other physiologic measure (eg, oxygen consumption [VO2], carbon dioxide production [VCO2], minute ventilation [VE], or workload) as a second independent variable after the VD/VT did not improve the correlation. This indicates that the correlation between the P(ET-a)CO2 and the workload is probably related to the dependence of the VD/VT on the workload. The PaCO2 in normal subjects and in the COPD group correlated significantly with the partial pressure of end-tidal carbon dioxide (PETCO2). Using multiple regression analysis, with the PaCO2 as the dependent variable and the PETCO2 (along with other physiologic measures) as the independent variables, we found that the standard error of the estimate was still above 2.1 mm Hg in normal subjects and in patients with COPD. We conclude that (1) during exercise, the P(ET-a)CO2 in normal subjects and in patients with COPD increases significantly, (2) the P(ET-a)CO2 gradient is more closely correlated with the VD/VT than any other physiologic variable, and (3) changes in the PETCO2 during exercise are not correlated closely with changes in the PaCO2.

Adult↗