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Biomedical subjects

Y Zhou

Publications and source records attributed to Y Zhou.

At least 415 records · Page 23Linked to original sources
PubMed1999

Microdissection and microcloning of rye (Secale cereale L.) chromosome 1R.

Chromosome 1R was microdissected and collected from mitotic metaphase spreads of rye (Secale cereale L.) by using glass needles. The isolated chromosomes were amplified in vitro by Sau3A linker adaptor-mediated polymerase chain reaction (PCR). After amplification, the presence of rye-specific DNA was verified by Southern hybridization. The second-round PCR products from five 1R chromosomes were cloned into a plasmid vector to create a chromosome-specific library, which produced approximately 220,000 recombinant clones. Characterization of the microclone library showed that the 172 clones evaluated ranged in size from 300-1800 bp with an average size of 950 bp, of which approximately 42% were medium/high copy and 58% were low/unique copy clones. Chromosome in situ hybridization confirmed that the PCR products from microdissected chromosomes originated from chromosome 1R, indicating that many chromosome 1R-specific sequences were present in the library.

Base Sequence↗
PubMed1999

Fluoxetine impairs the CYP2D6-mediated metabolism of propafenone enantiomers in healthy Chinese volunteers.

OBJECTIVE: To determine the effect of 20 mg/day fluoxetine on the pharmacokinetics of propafenone enantiomers and CYP2D6 activity by phenotyping with dextromethorphan. METHODS: Nine healthy Chinese volunteers (seven men and two women) were included in a two-phase study. Dextromethorphan (20 mg) was given before and after subjects took 20 mg/day fluoxetine for 10 days, and the dextromethorphan metabolic ratio was calculated to determine CYP2D6 phenotype. Pharmacokinetic studies of propafenone enantiomers after a single oral 400 mg dose before and after pretreatment with 20 mg/day fluoxetine for 10 days were also conducted in these subjects. Reversed-phase HPLC with precolumn derivatization was used to determine enantiomeric concentrations of propafenone in plasma. RESULTS: Mean CYP2D6 dextromethorphan metabolic ratios before and after fluoxetine therapy were 0.028 +/- 0.031 and 0.080 +/- 0.058, respectively (P = .001), indicating that a strong inhibition of CYP2D6 by fluoxetine activity was observed in Chinese subjects. Propafenone metabolism was also impaired significantly after fluoxetine treatment. The elimination half-life, peak concentration, and area under the curve from 0 hours to infinity of two enantiomers after fluoxetine therapy were significantly increased compared with those at baseline (P < .01), whereas oral clearance decreased from 75.01 +/- 17.69 L/h to 49.36 +/- 8.62 L/h for S-propafenone (P = .005) and from 107.62 +/- 33.82 L/h to 70.60 +/- 12.42 L/h for R-propafenone (P = .027). In addition, fluoxetine increased the peak concentration of S-propafenone by 39% and that of R-propafenone by 71% (P < .05). A significant increase of the time to reach peak concentration was observed only in the R-enantiomer and not in the S-enantiomer of propafenone after fluoxetine therapy. There were no differences in the percentage changes of PR and QRS intervals before or after fluoxetine pretreatment at the time observed (P > .05). CONCLUSION: We conclude that fluoxetine may cause significant inhibition of the CYP2D6 activity as determined by dextromethorphan phenotyping. This inhibition impairs the metabolism of propafenone enantiomers in Chinese subjects. Caution must be exercised when fluoxetine and propafenone are coadministered to avoid potential toxicity.

Administration, Oral↗
PubMed1999

Neuroautoantibody immunoreactivity in relation to aging and stress in apolipoprotein E-deficient mice.

Progressive disruption of both the neuroendocrine and immune systems has been correlated with age-associated pathogenesis in patients with Alzheimer's disease and in mice lacking apolipoprotein E (ApoE). In this study, we examined neuroautoimmune and neuroendocrine activities in relation to aging and stress in ApoE-deficient mice. An elevated level of autoantibodies against brain antigens was found in sera from ApoE-deficient mice compared to that of wild-type mice as early as 7-8 weeks of age. However, there was no significant difference between the two genotypes at this age in the effect of stress on serum corticosterone or autoantibody titers. Higher titers of autoantibodies were observed in approximately 12-week-old ApoE-deficient mice, especially in those exposed to chronic stress. Based on Western analysis, sera from ApoE-deficient mice showed a strong immunoreactivity with approximately 78 kDa and approximately 40 kDa brain abundant polypeptides, approximately 58 kDa non-brain tissue abundant antigen, and others of approximately, 80-82 kDa in both the brain and non-brain tissues. Immunofluorescence confocal microscopy showed that the major cellular components recognized by the autoimmune sera from ApoE-deficient mice were associated with neuronal cell nuclei and fiber-like structures in different regions of the brain, including the frontal cortex, lateral cortex and hippocampus. These results suggest that neuroautoimmunity associated with the aging process and exposure to chronic stress may be involved in early development of neurodegeneration in mice with ApoE-deficiency.

Aging↗
PubMed1999

Effects of growth hormone and pair-feeding on leptin mRNA expression in liver and adipose tissue.

Previous research has reported that elevations in circulating growth hormone (GH) levels in meat-type chickens depresses feed intake (FI) more than 30%. It is known that the product of the obese gene, leptin, functions to regulate FI and energy expenditure. To investigate the effect of GH on leptin gene expression, broiler chickens were infused with recombinant chicken GH. To separate any secondary effects of a GH-induced reduction in FI on leptin expression, groups of birds were pair-fed to an average level of voluntary intake similar to GH-treated birds, but received no GH treatment. GH treatment induced a dose-dependent increase in liver leptin gene expression, as measured by reverse transcriptase-polymerase chain reaction, whereas leptin expression in adipose tissue was unchanged. Conversely, in chickens pair-fed (feed-restricted) there was a decrease in leptin gene expression in both tissues. These results provide evidence of a direct effect of GH on leptin gene expression, which is independent of any effects on intake attributable to GH-treatment, and suggest differential regulation of leptin expression between adipose tissue and liver. The results of these experiments provide the first evidence of a relationship between GH and leptin in domestic birds.

Adipose Tissue↗
PubMed1999

New insights into the mechanism and actions of growth hormone (GH) in poultry.

Despite well documented anabolic effects of GH in mammals, a clear demonstration of such responses in domestic poultry is lacking. Recently, comprehensive dose-response studies of GH have been conducted in broilers during late post-hatch development (8 to 9 weeks of age). GH reduced feed intake (FI) and body weight gain in a dose-dependent manner, whereas birds pair-fed to the level of voluntary FI of GH-infused birds did not differ from controls. The reduction in voluntary FI may involve centrally mediated mechanisms, as hypothalamic neuropeptide Y protein and mRNA were reduced with GH, coincident with the maximal depression in FI. Growth of breast muscle was also reduced in a dose-dependent manner. Circulating IGF-I was not enhanced by GH, despite evidence that early events in the GH signaling pathway were intact. A GH dose-dependent increase in circulating 3,3',5-triiodothyronine(T3) paralleled decreases in hepatic 5D-III monodeiodinase activity, whereas 5'D-I activity was not altered. This confirms that a marked hyperthyroid response to GH occurs in late posthatch chickens, resulting from a decrease in the degradative pathway of T3 metabolism. This secondary hyperthyroidism would account for the decreased skeletal muscle mass (52) and lack of enhanced IGF-I (53) in GH-treated birds. Based upon these studies, it is now evident that GH does in fact have significant effects in poultry, but metabolic responses may confound the anabolic potential of the hormone.

Animals↗
PubMed1999

A dynamically regulated 14-3-3, Slob, and Slowpoke potassium channel complex in Drosophila presynaptic nerve terminals.

Slob is a novel protein that binds to the carboxy-terminal domain of the Drosophila Slowpoke (dSlo) calcium-dependent potassium (K(Ca)) channel. A yeast two-hybrid screen with Slob as bait identifies the zeta isoform of 14-3-3 as a Slob-binding protein. Coimmunoprecipitation experiments from Drosophila heads and transfected cells confirm that 14-3-3 interacts with dSlo via Slob. All three proteins are colocalized presynaptically at Drosophila neuromuscular junctions. Two serine residues in Slob are required for 14-3-3 binding, and the binding is dynamically regulated in Drosophila by calcium/calmodulin-dependent kinase II (CaMKII) phosphorylation. 14-3-3 coexpression dramatically alters dSlo channel properties when wild-type Slob is present but not when a double serine mutant Slob that is incapable of binding 14-3-3 is present. The results provide evidence for a dSlo/Slob/14-3-3 regulatory protein complex.

14-3-3 Proteins↗
PubMed1999

Effect of lidocaine on improving cerebral protection provided by retrograde cerebral perfusion: a neuropathologic study.

OBJECTIVE: To determine whether lidocaine can improve the neuropathologic results in canine brains after retrograde cerebral perfusion (RCP). DESIGN: Randomized, blinded, experimental study. SETTING: University animal laboratory. PARTICIPANTS: Mongrel dogs. INTERVENTIONS: Fourteen mongrel dogs were placed on 120 minutes of hypothermic (20 degrees C) RCP. Following the RPC, they then resumed cardiopulmonary bypass and rewarming for 60 minutes. In the lidocaine group (n = 8), lidocaine was administered continuously; in the control group (n = 6), normal saline was administered. Cerebral perfusion fixation was performed at the end of the experiment. MEASUREMENTS AND MAIN RESULTS: The number of ischemic cells in 200 neurons was counted in the parietal cortex, CA1 sector of the hippocampus, CA3 sector of the hippocampus, ventral posterolateral nucleus of the thalamus, and Purkinje cells of the cerebellar cortex. Those in the parietal cortex, CA1 sector of the hippocampus, and ventral posterolateral nucleus of the thalamus were significantly less in the lidocaine group than in the control group (25.8+/-17.3 v 53.7+/-12.0; p < 0.01; 17.0+/-8.5 v 54.7+/-22.1; p < 0.01; and 16.9+/-17.8 v 49.7+/-28.4; p < 0.05, respectively). The total number of ischemic cells in the five examined regions was also significantly less in the lidocaine group than in the control group (89.5+/-19.4 v 219.5+/-45.5; p < 0.01). CONCLUSION: Continuous lidocaine significantly alleviated the ischemic neuropathologic injury after RCP and thus possibly improved cerebral protection.

Anesthetics, Local↗
PubMed1999

Comparative study of photophysical properties of isomeric tetrapyridyl- and tetra-(N-hexadecylpyridiniumyl) porphyrins.

Photophysical properties (absorption spectra, fluorescence spectra, lifetimes and quantum yields) were studied for the three isomers of tetrapyridylporphyrins (TPyPs) in CHCl3 and tetra-(N-hexadecylpyridiniumyl) porphyrins (TC16PyPs) in CHCl3, CH3OH and Triton X-100 micelle solution. While the ground-state and excited-state properties are very similar for the three isomers of neutral TPyP, significant differences exist among the isomers of amphiphilic TC16PyP. Amphiphilic porphyrins bearing hydrophilic pyridinium and hydrophobic long-chain alkyl groups are characterized by reduced fluorescence quantum yields, biexponential fluorescence decay, and appreciable aggregation in nonpolar solvents. The observed biexponential fluorescence decay of amphiphilic porphyrins can be interpreted in terms of mixing of the S1 and a close-lying CT state in which an electron is transferred from the porphyrin core to the electron-deficient pyridinium group.

Isomerism↗
PubMed1999

Studies of diffusional release of a dispersed solute from polymeric matrixes by finite element method.

This paper presents systematic analyses by the finite element method of release kinetics of a dispersed solute from various matrixes (i.e. , slab, sphere, cylinder, and convex tablet), with or without boundary-layer resistance, into a finite or an infinite external volume. In the case of sink conditions, the numerical results agree well with the existing analytical solutions. For the problems of solute release into a finite external volume, where the analytical solutions are not available, this work has provided numerical solutions of the differential equations describing the release kinetics, moving boundaries, and concentration profiles. This work has also revealed the dependence of release kinetics on the initial solute loading, the external volume, and the boundary-layer thickness. The method presented here can describe the entire process of diffusional release before and after the dispersed solute has been dissolved without the pseudo steady-state assumption and it is applicable to both small and large ratio of initial solute loading to the solute solubility in the matrix.

Algorithms↗
PubMed1999

Characterization of AMPA receptors on isolated amacrine-like cells in carp retina.

In amacrine-like cells freshly dissociated from crucian carp (Carassius auratus) retina, we recorded whole-cell responses to rapid application of glutamate and kainate. Currents induced by glutamate, but not kainate, usually showed extremely rapid desensitization, and the mean time constant for the decay of the responses to 10 mM glutamate was 2.77 ms. N-methyl-D-aspartate (NMDA) failed to induce any current even with coapplication of glycine and removal of extracellular Mg2 +. 1-(4-aminophenyl)-3-Methylcarbamyl-4-methyl-7,8-methylenedioxy-3, 4-dihydro-5H-2,3-benzodiazepine (GYKI 53655), a selective alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor antagonist, was found to completely block glutamate-induced currents, suggesting that the glutamate receptors on these cells are AMPA preferring. The value of EC50 for glutamate and kainate was determined to be 2.73 mM and 97.5 microM, respectively. Noise analysis of fluctuation of whole-cell currents induced by kainate of different concentrations indicated that the mean conductance of the AMPA receptor channels was 5.70 pS. Splice variant analysis of the AMPA receptors was also conducted by comparing the effects of cyclothiazide, a flip receptor-preferring modulator and 4-[2-(phenylsulphonylamino)ethylthio]-2,6-difluoro-phenoxyaceta mide (PEPA), a flop receptor-preferring modulator, on glutamate-induced responses. PEPA was much more potent than cyclothiazide at these receptors with a EC50 of 17.3 microM. The mean ratio of the potentiation by PEPA versus cyclothiazide (P/C ratio) was 4.39. These modulatory effects of cyclothiazide and PEPA were rather similar to those obtained at AMPA receptors assembled from flop variants expressed in Xenopus oocytes, suggesting that the AMPA receptor of the carp amacrine cells may predominantly consist of the flop splice variants.

Alternative Splicing↗
PubMed1999

Neuronal nitric oxide synthase in the neural pathways of the urinary bladder.

Nitric oxide (NO) is a unique biological messenger molecule. It serves, in part, as a neurotransmitter in the central and peripheral nervous systems. Neurons containing NO have been identified histochemically by the presence of nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) reactivity or immunohistochemically by the antibody for neuronal NO synthase (n-NOS). Previous histochemical or pharmacological studies have raised the possibility that NO may play an important role in the neural pathways of the lower urinary tract. There is also considerable evidence to suggest that n-NOS is plastic and could be upregulated following certain lesions in the lower urinary tract. The present review summarises the distribution of n-NOS containing neurons innervating the urinary bladder and the changes of the enzyme expression in some experimentally induced pathological conditions.

Animals↗
PubMed1999

Degenerative changes of afferent neurons in the lumbosacral dorsal root ganglia following complete urethral obstruction in guinea pigs.

OBJECTIVE: The ultrastructural changes in the bladder afferent neurons were examined in the guinea pig following acute complete urethral obstruction. MATERIAL AND METHODS: Complete urethral ligation was carried out in nine guinea pigs under anaesthesia and the animals were sacrificed at 12, 24 and 48 h postoperatively. Three sham-operated animals were sacrificed at 48 h postoperatively as controls. The dorsal root ganglia (DRG) at L6, S1 and S2 spinal segments of the animals in each group were removed and processed for electron microscopic study. RESULTS: In the control groups, all the DRG neurons at L6-S2 segments appeared normal. At 12 h after urethral ligation, a few neurons in the DRG at various segments showed signs of structural changes, notably the mitochondria. Mitochondrial swelling was more pronounced at 24 h, and by 48 h most of them became vacuolated and lysed. It was estimated by semiquantitative study that 18.6% and 22% of DRG neuronal profiles at 24 and 48 h, respectively, displayed severe mitochondrial swelling and vacuolation. CONCLUSIONS: The observed degenerative changes in DRG neurons following complete urethral obstruction may be a cellular reaction in response to the axonal injury elicited by bladder overdistension. This may account for alterations in visceral sensation in patients with acute urinary retention.

Acute Disease↗
PubMed1999

Estimating maximum concentrations for open path monitoring along a fixed beam path.

Researchers have applied open path optical sensing techniques to a variety of workplace and environmental monitoring problems. Usually these data are reported in terms of a path-average (or path-integrated) concentration. When assessing potential human exposures along a beam path, this path-average value is not always informative, since concentrations along the path can vary substantially from the beam average. The focus of this research is to arrive at a method for estimating the upper-bound in contaminant concentrations over a fixed open beam path. The approach taken here uses a statistical model to estimate an upper-bound concentration based on a combination of the path-average and a measure of the spatial variability computed from point samples along the beam path. Results of computer simulations and experimental testing in a controlled ventilation chamber indicate that the model produced conservative estimates for the maximum concentration along the beam path. This approach may have many applications for open path monitoring in workplaces or wherever maximum concentrations are a concern.

Humans↗
PubMed1999

On the design of the coronary arterial tree: a generalization of Murray's law.

Murray's law has been generalized to provide morphometric relationships among various subtrees as well as between a feeding segment and the subtree it perfuses. The equivalent resistance of each subtree is empirically determined to be proportional to the cube of a subtree's cumulative arterial length (L) and inversely proportional to a subtree's arterial volume (V) raised to a power of approximately 2.6. This relationship, along with a minimization of a cost function, and a linearity assumption between flow and cumulative arterial length, provides a power law relationship between V and L. These results, in conjunction with conservation of energy, yield relationships between the diameter of a segment and the length of its distal subtree. The relationships were tested based on a complete set of anatomical data of the coronary arterial trees using two models. The first model, called the truncated tree model, is an actual reconstruction of the coronary arterial tree down to 500 microm in diameter. The second model, called the symmetric tree model, satisfies all mean anatomical data down to the capillary vessels. Our results show very good agreement between the theoretical formulation and the measured anatomical data, which may provide insight into the design of the coronary arterial tree. Furthermore, the established relationships between the various morphometric parameters of the truncated tree model may provide a basis for assessing the extent of diffuse coronary artery disease.

Arteries↗
PubMed1999

Delivery rates after in-vitro fertilization following bilateral salpingectomy due to hydrosalpinges: a case control study.

This retrospective case-control study assessed the impact of bilateral salpingectomy due to uni- or bilateral hydrosalpinges on the outcome of in-vitro fertilization (IVF) in a large consecutive series of patients. The effect of bilateral salpingectomy due to hydrosalpinges on pregnancy outcome was compared in 139 patients (263 cycles) and 139 age-matched controls with tubal infertility without hydrosalpinges (296 cycles). The delivery rates per initiated cycle as well as the implantation rates were equal in the two groups (21.7 versus 21.6% and 19 versus 21%). The number of embryos, the cleavage stage, and the embryo morphology score were equal in the two groups. Among 92 patients treated with 182 IVF cycles who underwent salpingectomy between 1.5 and 5 years prior to their first IVF cycle, the delivery and the implantation rates were 22.5 and 20.5% respectively. Of the patients with salpingectomy after an average of 1.7 failed IVF cycles and who re-entered the IVF programme 3 and 6 months subsequent to surgery, 47 were treated with 83 IVF cycles. The live birth and the implantation rates after surgery in this group were 20.5 and 20% respectively. It is concluded that bilateral salpingectomy due to hydrosalpinges restores a normal delivery as well as implantation rate after IVF treatment compared to controls. A favourable outcome is also found in patients operated on after repeated IVF failures. Furthermore, a normal live birth rate as well as a high implantation rate is maintained for at least three IVF cycles subsequent to surgical treatment.

Adult↗
PubMed1999

A Danish national cohort of 730 infants born after intracytoplasmic sperm injection (ICSI) 1994-1997.

This national cohort study included all clinical pregnancies obtained after intracytoplasmic sperm injection (ICSI) registered in Denmark between January 1994 and July 1997 at five public and eight private fertility clinics. Laboratory and clinical data were obtained from the fertility clinics. The couples answered a questionnaire regarding the pregnancy and the health of the child (response rate 94%). Data validation was carried out through discharge charts. The mean age of the women was 32.1 years. In 84.2% of couples, male factor was the main reason for performing ICSI, and in 4.8% epididymal spermatozoa were used. The mean number of embryos replaced was 2.3 (range 1-3) and in 95% of cases fresh embryos were transferred. Only 183 women (28.5%) underwent prenatal diagnosis, resulting in 209 karyotypes with seven (3.3%) chromosome aberrations. Six major chromosomal abnormalities (2.9%) and one inherited structural chromosome aberration (0.5%) were found, but no sex chromosome aberrations. The frequency of multiple birth, Caesarean section rate, gestational age, preterm birth, and birth weight were comparable with previous studies. The perinatal mortality rate was 13.7 per 1000 children born with a gestational age of 24 weeks or more. In 2.2% (n = 16) of the liveborn infants, and in 2.7% (n = 20) of all infants, major birth defects were reported by the parents. Minor birth defects were found in nine liveborn infants (1.2%). In conclusion, the results of this study on outcome of ICSI pregnancies are in line with earlier reports, except that no sex chromosome abnormalities were found.

Adult↗
PubMed1999

Nature of the energy transfer process in compressible turbulence.

Using a two-point closure theory, the eddy-damped-quasinormal-Markovian approximation, we have investigated the energy transfer process and triadic interactions of compressible turbulence. In order to analyze the compressible mode directly, the Helmholtz decomposition is used. The following issues were addressed: (1) What is the mechanism of energy exchange between the solenoidal and compressible modes, and (2) is there an energy cascade in the compressible energy transfer process? It is concluded that the compressible energy is transferred locally from the solenoidal part to the compressible part. It is also found that there is an energy cascade of the compressible mode for high turbulent Mach number. Since we assume that the compressibility is weak, the magnitude of the compressible (radiative or cascade) transfer is much smaller than that of the solenoidal cascade. These results are further confirmed by studying the triadic energy transfer function, the most fundamental building block of the energy transfer.

Journal Article↗