Biomedical subjects

Jun Zhu

Publications and source records attributed to Jun Zhu.

At least 163 records · Page 9Linked to original sources

PubMed2003

A method for marker-assisted selection based on QTLs with epistatic effects.

A method for marker-assisted selection (MAS) based on quantitative trait loci (QTLs) with epistatic effects is proposed. The efficiency of such method is investigated by simulations under a wide range of situations. In the presence of epistasis, MAS generally yields longer persistence response than that based exclusively on additive or additive and dominance. Neglecting epistasis could result in considerable loss in response, and more pronounced at later generations. In addition to population size and trait heritability, genetic variance configurations play an important role in determining both the short- and long-term efficiencies of MAS. MAS using breeding values not only achieves higher response, but also tends to have smaller standard error than other methods in most cases. Errors in QTL detection cause distinct reductions in responses to MAS in most cases. It is thus concluded that verifications of putative QTL and its magnitude of effect and accurate map chromosome location are imperative to realize the potentials of MAS.

Epistasis, Genetic↗

PubMed2003

Influence of temperature and time on phosphorus removal in swine manure during batch aeration.

This study was conducted to investigate the effects of temperature and time on the mechanisms of phosphorus removal in swine manure during aeration. Removal of soluble orthophosphates significantly increased with aeration time and temperature. Successive significant ortho-P removals were observed between days one and nine but no significant additional removals were recorded thereafter. Removals were significantly higher at temperatures of 20 and 25 degrees C than at temperatures of 5, 10, and 15 degrees C and ranged between 22.9 to 31.0%. Insoluble inorganic phosphorus also changed significantly with aeration time and temperature and with a similar trend as soluble orthophosphates. The pH of the manure explained 92 and 87% of the content of insoluble inorganic phosphorus at lower temperatures (5, 10, 15 degrees C) and at higher temperatures (20, and 25 degrees C), respectively. Organic phosphorus and aerobes growth patterns were similar to that of soluble orthophosphates removal. The rapid growth of aerobes was most probably the principal factor behind a rapid soluble ortho-P removal above 15 degrees C. The contribution of inorganic phosphates to the removal of soluble orthophosphates was approximately 61% while that due to organic P was approximately 35%. Precipitation was found to be the principal mechanism governing removal of soluble ortho-P in swine manure during aeration treatments.

Air↗

PubMed2003

Settling characteristics of nursery pig manure and nutrient estimation by the hydrometer method.

The hydrometer method to measure manure specific gravity and subsequently relate it to manure nutrient contents was examined in this study. It was found that this method might be improved in estimation accuracy if only manure from a single growth stage of pigs was used (e.g., nursery pig manure used here). The total solids (TS) content of the test manure was well correlated with the total nitrogen (TN) and total phosphorus (TP) concentrations in the manure, with highly significant correlation coefficients of 0.9944 and 0.9873, respectively. Also observed were good linear correlations between the TN and TP contents and the manure specific gravity (correlation coefficients: 0.9836 and 0.9843, respectively). These correlations were much better than those reported by past researchers, in which lumped data for pigs at different growing stages were used. It may therefore be inferred that developing different linear equations for pigs at different ages should improve the accuracy in manure nutrient estimation using a hydrometer. Also, the error of using the hydrometer method to estimate manure TN and TP was found to increase, from +/- 10% to +/- 50%, with the decrease in TN (from 700 ppm to 100 ppm) and TP (from 130 ppm to 30 ppm) concentrations in the manure. The estimation errors for TN and TP may be larger than 50% if the total solids content is below 0.5%. In addition, the rapid settling of solids has long been considered characteristic of swine manure; however, in this study, the solids settling property appeared to be quite poor for nursery pig manure in that no conspicuous settling occurred after the manure was left statically for 5 hours. This information has not been reported elsewhere in the literature and may need further research to verify.

Animals↗

PubMed2003

Characteristics of MgxZn1-xO thin film bulk acoustic wave devices.

Piezoelectric thin film zinc oxide (ZnO) and its ternary alloy magnesium zinc oxide (MgxZn1-xO) have broad applications in transducers, resonators, and filters. In this work, we present a new bulk acoustic wave (BAW) structure consisting of Al/MgxZn1-xO/n(+)-ZnO/r-sapphire, where Al and n+ type ZnO serve as the top and bottom electrode, respectively. The epitaxial MgxZn1-xO films have the same epitaxial relationships with the substrate as ZnO on r-Al2O3, resulting in the c-axis of the MgxZn1-xO being in the growth plane. This relationship promotes shear bulk wave propagation that affords sensing in liquid phase media without the dampening effects found in longitudinal wave mode BAW devices. The BAW velocity and electromechanical coupling coefficient of MgxZn1-xO can be tailored by varying the Mg composition, which provides an alternative and complementary method to adjust the BAW characteristics by changing the piezoelectric film thickness. This provides flexibility to design the operating frequencies of thin film bulk acoustic wave devices. Frequency responses of devices with two acoustic wave modes propagating in the specified structure are analyzed using a transmission line model. Measured results show good agreement with simulation.

Acoustics↗

PubMed2003

Modeling the dependence between number of trials and success probability in beta-binomial-Poisson mixture distributions.

Beta-binomial models are widely used for overdispersed binomial data, with the binomial success probability modeled as following a beta distribution. The number of binary trials in each binomial is assumed to be nonrandom and unrelated to the success probability. In many behavioral studies, however, binomial observations demonstrate more complex structures. In this article, a general beta-binomial-Poisson mixture model is developed, to allow for a relation between the number of trials and the success probability for overdispersed binomial data. An EM algorithm is implemented to compute both the maximum likelihood estimates of the model parameters and the corresponding standard errors. For illustration, the methodology is applied to study the feeding behavior of green-backed herons in two southeastern Missouri streams.

Algorithms↗

PubMed2003

Agrobacterium bioassay strain for ultrasensitive detection of N-acylhomoserine lactone-type quorum-sensing molecules: detection of autoinducers in Mesorhizobium huakuii.

An ultrasensitive bioassay system for the detection of N-acylhomoserine lactones (AHLs) was constructed in Agrobacterium tumefaciens by using the T7 expression system to overproduce the AHL receptor TraR. This strain detected many diverse AHLs, some at extremely low concentrations. We used this strain to detect for the first time AHLs made by Mesorhizobium huakuii, which symbiotically fixes nitrogen in association with the legume Astragalus sinicus, a source of green manure throughout eastern Asia.

4-Butyrolactone↗

PubMed2003

A constitutively active variant of the quorum-sensing regulator LuxO affects protease production and biofilm formation in Vibrio cholerae.

Vibrio cholerae normally inhabits aquatic habitats but can cause a severe diarrheal illness in humans. Its arsenal of virulence factors includes a secreted hemagglutinin (HA) protease. An HA protease-deficient mutant of V. cholerae was isolated and designated E7946 mpc. E7946 mpc was found to contain a point mutation in the luxO quorum-sensing regulator. In accordance with this finding, E7946 mpc exhibits a defect in quorum sensing. The mutant luxO allele [luxO(Con)] produces a protein with a leucine-to-glutamine substitution at amino acid 104. Transfer of the luxO(Con) allele to an otherwise wild-type background was sufficient to eliminate HA protease expression; conversely, deletion of luxO(Con) from E7946 mpc restored protease activity. We demonstrate that LuxO(Con) constitutively represses the transcription of hapR, an essential positive regulator of HA protease. Interestingly, strains harboring luxO(Con) form enhanced biofilms, and enhanced biofilm formation does not appear to be dependent on reduced HA protease expression. Taken together, the results confirm the role of LuxO as a central "switch" that coordinately regulates virulence-related phenotypes such as protease production and biofilm formation.

Bacterial Proteins↗

PubMed2003

Examination of diverse toxin-coregulated pilus-positive Vibrio cholerae strains fails to demonstrate evidence for Vibrio pathogenicity island phage.

The major virulence factors of toxigenic Vibrio cholerae are cholera toxin, which is encoded by a lysogenic filamentous bacteriophage (CTXPhi), and toxin-coregulated pilus (TCP), an essential colonization factor that is also the receptor for CTXPhi. The genes involved in the biosynthesis of TCP reside in a pathogenicity island, which has been reported to correspond to the genome of another filamentous phage (designated VPIPhi) and to encode functions necessary for the production of infectious VPIPhi particles. We examined 46 V. cholerae strains having diverse origins and carrying different genetic variants of the TCP island for the production of the VPIPhi and CTXPhi in different culture conditions, including induction of prophages with mitomycin C and UV irradiation. Although 9 of 10 V. cholerae O139 strains and 12 of 15 toxigenic El Tor strains tested produced extracellular CTXPhi, none of the 46 TCP-positive strains produced detectable VPIPhi in repeated assays, which detected as few as 10 particles of a control CTX phage per ml. These results contradict the previous report regarding VPIPhi-mediated horizontal transfer of the TCP genes and suggest that the TCP island is unable to support the production of phage particles. Further studies are necessary to understand the mechanism of horizontal transfer of the TCP island.

Bacteriophages↗

PubMed2003

[Clinical features of 3798 perinatals suffering from syndromic neural tube defects].

OBJECTIVE: To investigate the patterns and associated malformations in neural tube defects (NTDs) cases. METHODS: From 1987 to 1995, hospital-based cluster sampling method was adopted for collecting data. During that period all live or still births with 28 weeks of gestation or more were assessed within 7 days after delivery. RESULTS: Three thousand seven hundred and ninety eight syndromic NTDs were identified, among which anencephaly, spina bifida and encephalocele were 997, 2394 and 407 respectively. 51.3% associated abnormalities of NTDs appeared in muscle and skeletal system, 19.6% in face, ear and neck, and 9.3% in urinary-genital system. Congenital talipes equinovarus, cleft lip with cleft palate, gastroschisis, talipes valgus, undescended testicle were frequently combined with NTDs. The most frequent association in schisis type of NTDs was NTDs accompanied by cleft lip with or without cleft palate (67.5%), followed by anencephaly with cleft palate (8.3%) and anencephaly with omphalocele (6.6%). Of all syndromic NTDs, the rate of low birth weight was 36.9%, of perinatal mortality was 71.2% and the ratio 33.1% patients were diagnosed prenatally. CONCLUSIONS: Approximately one third of NTDs may be associated with other system's malformation. Syndromic NTDs has a high perinatal mortality rate and a poor prognosis.

Abnormalities, Multiple↗

PubMed2003

[Epidemiological investigation of perinatals affected by transverse facial cleft in China].

OBJECTIVE: To study the epidemiological features of transverse cleft and its multiple congenital anomaly (MCA) patterns in China. METHODS: From 1987 through 1992, hospital-based cluster sampling method was adopted for collecting data. During that period all live or stillbirths with 28 weeks of gestation or more were assessed within 7 days after delivery. RESULTS: 94 cases of transverse facial cleft were identified among 4,489,692 births, so the prevalence rate of transverse facial cleft at birth was 0.21/10(4). The prevalence rates in urban areas and in rural areas were 0.20/10(4) and 0.23/10(4), respectively. And the rates in male and female births were both 0.21/10(4). 69 cases occurred with other malformations, among which the anomalies of ear were the most frequent association (53.6%). The perinatal fatality rate was 46.9%, a significant difference of fatality rate was found between isolated forms (16.0%) and associated forms of transverse facial cleft (58.0%). CONCLUSIONS: The prevalence rate of transverse facial cleft in China is more than the estimated rate. No significant differences are found between urban and rural areas, and between male and female births. Most of transverse facial clefts are associated forms, often as one feature of other syndromes.

China↗

PubMed2003

[Analysis of maternal mortality in China from 1996 to 2000].

OBJECTIVE: To study the trend and characteristics of maternal mortality in China from 1996 to 2000. METHODS: Population-based epidemiological survey in 116 monitoring units in China were used. RESULTS: Maternal mortality in China dropped by 17.1% from 63.9 per 100,000 live births in 1996 to 53.0 in 2000, in rural area dropped by 22.2% from 86.4 per 100,000 live births to 67.2, and in urban area only 1.0% from 29.2 per 100 000 live births to 28.9, the leading causes of maternal mortality in China are hemorrhage, preeolampsia/eclampsia and amniotic fluid embolism the maternal mortality due to hemorrhage in national level and rural level has declined by 33.8%, 34.9% respectively. CONCLUSION: The maternal mortality appears a declined trend on both the national and rural levels in China from 1996 to 2000, the maternal mortality due to hemorrhage dose also, bur the maternal mortality in urban area keeps unstable.

Cause of Death↗

PubMed2003

[Analysis of additive and AE interaction effects of QTLs controlling plant height, heading date and panicle number in rice (Oryza sativa L.)].

Plant height (PH), heading date (HD) and productive panicle number (PN) are important agronomic trait in rice. Appropriate plant height, heading date and panicle number are prerequisites for the desired high and stable yield level in rice breeding programs. A recombinant inbred line (RIL) population consisting of 304 individuals was derived from a cross between indica varieties Zhong156 and Gumei2, from which a linkage map consisting of 168 RFLP, SSLP, RAPD and RGA markers that distribute on all the 12 rice chromosomes was constructed, and covers 1447.9 cM of the rice genome. The parents and 304 F9 lines were grown in the paddy field in China National Rice Research Institute (CNRRI), Hangzhou, China in 2001. The experiments were carried out in two seasons followed a randomized complete block design. QTLMapper 1.01 was applied to detect QTLs and QTL x environment (QE) interaction for HD (heading data), PH (plant height) and PN (panicle number), and conditional mapping for PH and PN was performed as well. A total of 15 QTLs with significant additive effects were detected, among which 4 QTLs had significant QE interaction. Ten QTLs with additive x additive epistatic effects for PH, HD and PN were detected, among which none showed significant epistatisis x environment interaction. These QTLs explained 12.12%, 1.38% and 5.00% of the total phenotypic variance for PH, HD and PN, respectively, and contributions were generally lower due to the strong epistatic effects. In conditional QTL analysis, the numbers of QTLs showing significant additive and epistatic effects were 7 and 6 for PH, and 3 and 3 for PN, respectively. Among the QTLs having significant additive effects for PH, qPH7-2 showed both additive effects and QE interaction, qPH7-1 and qPH10 showed QE interaction only, and the remaining 4 QTLs showed additive effects only. Each of the 3 QTLs having significant additive effects for PN did not display significant QE interaction. No epistatic QE interactions was detected. In addition, conditional QTL analysis indicated that the expression of QTLs for PH and PN may vary depending on the QTLs for HD.

Breeding↗

PubMed2003

[The monitoring of cleft lip with or without cleft palate in China: 1996 - 2000].

OBJECTIVE: To describe the epidemiological features of cleft lip with or without cleft palate (CL +/- P) in Chinese perinatals. METHODS: From 1996 through 2000, hospital-based cluster sampling method was adopted for collecting data. During that period all live or still births with 28 weeks of gestation or more delivered in monitoring hospitals were assessed within 7 days after birth. RESULTS: The birth prevalence rates of cleft lip (CL) and of cleft lip with cleft palate (CLP) were 5.03/10,000, 8.97/10,000 respectively, then the rate of CL +/- P was 14.0/10,000. The prevalence rates in urban and rural area, in male and female births were 13.28/10,000 and 15.57/10,000, 16.06/10,000 and 11.40/10,000 respectively. Significant difference was found among maternal-age-specific prevalence rates, and the highest one was observed in >or= 35 maternal age group. 87.25% of CL +/- P was isolated forms. No secular trend was found during that period. The perinatal fatality rate of CL +/- P was 19.04%, and the rate in isolated forms was 12.69%, but the rate in syndromic CL +/- P was as high as 62.60%. CONCLUSIONS: No decline trend in prevalence rate of CL +/- P was observed during 1996 approximately 2000. Compared with prevalence rates of CL +/- P in some foreign countries, it was higher in China during same period.

Adult↗

PubMed2002

In vivo activation of cAMP signaling induces growth arrest and differentiation in acute promyelocytic leukemia.

Differentiation therapy for acute myeloid leukemia uses transcriptional modulators to reprogram cancer cells. The most relevant clinical example is acute promyelocytic leukemia (APL), which responds dramatically to either retinoic acid (RA) or arsenic trioxide (As(2)O(3)). In many myeloid leukemia cell lines, cyclic adenosine monophosphate (cAMP) triggers growth arrest, cell death, or differentiation, often in synergy with RA. Nevertheless, the toxicity of cAMP derivatives and lack of suitable models has hampered trials designed to assess the in vivo relevance of theses observations. We show that, in an APL cell line, cAMP analogs blocked cell growth and unraveled As(2)O(3)-triggered differentiation. Similarly, in RA-sensitive or RA-resistant mouse models of APL, continuous infusions of 8-chloro-cyclic adenosine monophosphate (8-Cl-cAMP) triggered major growth arrest, greatly enhanced both spontaneous and RA- or As(2)O(3)-induced differentiation and accelerated the restoration of normal hematopoiesis. Theophylline, a well-tolerated phosphodiesterase inhibitor which stabilizes endogenous cAMP, also impaired APL growth and enhanced spontaneous or As(2)O(3)-triggered cell differentiation in vivo. Accordingly, in an APL patient resistant to combined RA-As(2)O(3) therapy, theophylline induced blast clearance and restored normal hematopoiesis. Taken together, these results demonstrate that in vivo activation of cAMP signaling contributes to APL clearance, independently of its RA-sensitivity, thus raising hopes that other myeloid leukemias may benefit from this therapeutic approach.

Animals↗

PubMed2002

bis-Azaaromatic quaternary ammonium analogues: ligands for alpha4beta2* and alpha7* subtypes of neuronal nicotinic receptors.

A series of bis-nicotinium, bis-pyridinium, bis-picolinium, bis-quinolinium and bis-isoquinolinium compounds was evaluated for their binding affinity at nicotinic acetylcholine receptors (nAChRs) using rat brain membranes. N,N'-Decane-1,12-diyl-bis-nicotinium diiodide (bNDI) exhibited the highest affinity for [(3)H]nicotine binding sites (K(i)=330 nM), but did not inhibit [(3)H]methyllycaconitine binding (K(i) >100 microM), indicative of an interaction with alpha4beta2*, but not alpha7* receptor subtypes, respectively. Also, bNDI inhibited (IC(50)=3.76 microM) nicotine-evoked (86)Rb(+) efflux from rat thalamic synaptosomes, indicating antagonist activity at alpha4beta2* nAChRs. N,N'-Dodecane-1,12-diyl-bis-quinolinium dibromide (bQDDB) exhibited highest affinity for [(3)H]methyllycaconitine binding sites (K(i)=1.61 microM), but did not inhibit [(3)H]nicotine binding (K(i)>100 microM), demonstrating an interaction with alpha7*, but not alpha4beta2* nAChRs. Thus, variation of N-n-alkyl chain length together with structural modification of the azaaromatic quaternary ammonium moiety afforded selective antagonists for the alpha4beta2* nAChR subtype, as well as ligands with selectivity at alpha7* nAChRs.

Aconitine↗

PubMed2002

Analysis of genetic effects of major genes and polygenes on quantitative traits. II. Genetic models for seed traits of crops.

Genetic models for quantitative seed traits with effects of several major genes and polygenes, as well as their GE interaction, were proposed. Mixed linear model approaches were suggested for analyzing the genetic models. Monte Carlo simulations were conducted to evaluate unbiasedness and efficiency for estimating fixed effects and variance components of the embryo and the endosperm models, including effects of a major gene from an unbalanced modified diallel mating design with nine parents, respectively. Simulation results showed that estimates of generalized least squares (GLS) were unbiased and efficient, while those of ordinary least squares (OLS) were almost as good as GLS. Minimum norm quadratic unbiased estimation (MINQUE) could obtain unbiased estimates of the variance components. It was also suggested that precision of MINQUE estimation would be improved with augmentation of experimental size. Data from a modified diallel design in upland cotton ( Gossypium hirsutum L.) were used as a worked example to illustrate the parameter estimation.

Journal Article↗

PubMed2002

Mitochondrial toxin inhibition of [(3)H]dopamine uptake into rat striatal synaptosomes.

Administration of the mitochondrial inhibitors malonate and 3-nitropropionic acid (3-NP) to rats provides useful models of Huntington's disease. Exposure to these inhibitors has been shown to result in increased extracellular concentrations of striatal dopamine (DA), which is neurotoxic at high concentrations. The cause of this increase is unknown. The purpose of this study was to determine whether mitochondrial inhibition alters dopamine transporter (DAT) function. Striatal synaptosomes were incubated in the presence of several structurally unrelated inhibitors of mitochondrial Complexes I, II, and IV, and [(3)H]DA uptake was measured. Although all of the toxins inhibited [(3)H]DA uptake, there was a large variation in their inhibitory potencies, the rank order being rotenone>>cyanide>azide>3-NP>>malonate. Examination of the kinetic parameters of [(3)H]DA uptake revealed that inhibition was due to a reduction in maximum velocity (V(max)), with no change in affinity (K(m)). The addition of either ATP or of ADP plus P(i) to synaptosomes treated with 3-NP, or of the reactive oxygen species spin trap alpha-phenyl-N-tert-butyl nitrone to synaptosomes exposed to either malonate or cyanide failed to prevent mitochondrial toxin-induced inhibition of DAT function. The lack of effect of high energy substrates or of a free radical scavenger suggests that the mechanism by which extracellular DA is increased by several mitochondrial toxins involves factors other than mitochondrial ATP production or oxidative stress. Taken together, the results suggest that one mechanism whereby mitochondrial toxins increase extracellular concentrations of DA is via interaction with the DAT at a site other than the substrate site, i.e. noncompetitive inhibition of the DAT.

Animals↗

PubMed2002

Quorum-sensing regulators control virulence gene expression in Vibrio cholerae.

The production of virulence factors including cholera toxin and the toxin-coregulated pilus in the human pathogen Vibrio cholerae is strongly influenced by environmental conditions. The well-characterized ToxR signal transduction cascade is responsible for sensing and integrating the environmental information and controlling the virulence regulon. We show here that, in addition to the known components of the ToxR signaling circuit, quorum-sensing regulators are involved in regulation of V. cholerae virulence. We focused on the regulators LuxO and HapR because homologues of these two proteins control quorum sensing in the closely related luminous marine bacterium Vibrio harveyi. Using an infant mouse model, we found that a luxO mutant is severely defective in colonization of the small intestine. Gene arrays were used to profile transcription in the V. cholerae wild type and the luxO mutant. These studies revealed that the ToxR regulon is repressed in the luxO mutant, and that this effect is mediated by another negative regulator, HapR. We show that LuxO represses hapR expression early in log-phase growth, and constitutive expression of hapR blocks ToxR-regulon expression. Additionally, LuxO and HapR regulate a variety of other cellular processes including motility, protease production, and biofilm formation. Together these data suggest a role for quorum sensing in modulating expression of blocks of virulence genes in a reciprocal fashion in vivo.

Animals↗