Biomedical subjects
Publications and source records attributed to Hui Zheng.
A blood film slide taken from a patient previously diagnosed as vivax malaria in Mojiang County, Yunnan Province, showing atypical forms. The ring forms had multinuclei, and the late trophozoites trended to form band. The schizonts and gametocytes were somewhat alike to Plasmodium vivax. PCR amplification confirmed that the patient was infected by P. knowlesi.
The hydroxylase component (MMOH) of the soluble form of methane monooxygenase (sMMO) isolated from Methylosinus trichosporium OB3b catalyzes both the O2 activation and the CH4 oxidation reactions at the oxygen-bridged dinuclear iron cluster present in its buried active site. During the reaction cycle, the diiron cluster forms a bis-mu-oxo-(Fe(IV))2 intermediate termed compound Q (Q) that reacts directly with methane. Many adventitious substrates also react with Q, most at a relatively slow rate. We have proposed that Q reacts preferentially with CH4 because the sMMO regulatory component MMOB induces a size selective pore into the MMOH active site as the two components form a complex. Support for this proposal has come through the observation of a nonlinear Arrhenius plot for the CH4 oxidation, presumably due to a shift in rate-limiting step from substrate binding at low temperature to C-H bond cleavage at high temperature. Reactions of all substrates other than CH4 fail to exhibit a break in the Arrhenius plot because binding is always rate limiting in the temperature range explored. Here we show that it is possible to induce a break in the Arrhenius plot for the ethane reaction with Q by using an MMOB mutant termed DBL2 (S109A/T111A) in which residues at the MMOH-MMOB interface are reduced in size. We hypothesize that this increases the ethane binding rate and shifts the Arrhenius breakpoint into the observable temperature range. As a result of this shift, the kinetic and activation parameters of the C-H bond breaking reaction for both methane and ethane can be observed using the DBL2 mutant. A 2H-KIE is observed for both substrate oxidation reactions when using DBL2, whereas only CH4 oxidation exhibits an effect when using wild type MMOB, consistent with the C-H bond cleaving reaction becoming at least partially rate limiting for ethane. Analysis of the temperature dependence of the 2H-KIE for ethane and methane for reactions using both mutant and wild type forms of MMOB suggests that quantum tunneling plays a significant role in methane oxidation but not ethane oxidation.
Presenilins (PS1/PS2) regulate proteolysis of beta-amyloid precursor protein (betaAPP) and affect its intracellular trafficking. Here, we demonstrate that a PS1-interacting protein, phospholipase D1 (PLD1), affects intracellular trafficking of betaAPP. Overexpression of PLD1 in PS1wt cells promotes generation of betaAPP-containing vesicles from the trans-Golgi network. Conversely, inhibition of PLD1 activity by 1-butanol decreases betaAPP trafficking in both wt and PS1-deficient cells. The subcellular localization of PLD1 is altered, and PLD enzymatic activity is reduced in cells expressing familial Alzheimer's disease (FAD) PS1 mutations compared with PS1wt cells. Overexpression of wt, but not catalytically inactive, PLD1 increases budding of betaAPP-containing vesicles from the trans-Golgi network in FAD mutant cells. Surface delivery of betaAPP is also increased by PLD1 in these cells. The impaired neurite outgrowth capacity in FAD mutant neurons was corrected by introducing PLD1 into these cells. The results indicate that PLD1 may represent a therapeutic target for rescuing compromised neuronal function in AD.
Alzheimer's disease (AD) and related dementing disorders having cognitive manifestations represent an increasing threat to public health. In the present study, the effects of a memory enhancing NLPR tetra-peptide (MEP), huperzine A (Hup A), or a combination of the two on the cognitive abilities of brain-lesioned mice were evaluated and compared with tacrine in the passive avoidance and Y-water maze tests for the acquisition and retention aspects of cognitive functions. MEP at microg kg(-1) doses, and Hup A or tacrine at mg kg(-1) doses significantly reversed the cognition deficits induced by scopolamine. For acquisition ability, it was observed that mice administered with MEP (4.0 microg kg(-1)) spent less time escaping onto the platform in the water maze than those treated with tacrine (1.5 mg kg(-1)); whereas for memory retention, tacrine-administration resulted in a higher step-through latency in mice at the tested dose regime. In addition, co-administration of MEP (2.0 microg kg(-1)) and Hup A (0.1 mg kg(-1)) exhibited an additive effect resulting in considerable improvements in both acquisition and retention abilities of brain-lesioned mice. The results demonstrated that MEP was highly efficient in the rescue of cognitive abilities of brain-lesioned mice and in particular, the effective doses of MEP were about two orders of magnitude lower than that of tacrine, a therapeutic currently used in the treatment of AD. Moreover, MEP and Hup A were effective at reduced doses when the two were co-administered, providing a rationale for their combined usage in the treatment of cognitive deficits.
Although U.S. prison inmates have higher rates of HIV infection than the general population, most inmates are not routinely tested for HIV infection at prison entry. The study objective was to implement a routine, voluntary HIV testing program in a Massachusetts county prison. During admission, inmates were given group HIV pre-test counseling and were subsequently offered private HIV testing. This intervention was compared to a control period during which HIV testing was provided only upon inmate or physician request. Between November 2004 and April 2005, 1,004 inmates met inclusion criteria and were offered routine, voluntary HIV testing. Of these, 734 (73.1%) accepted, 2 (0.3%) were HIV-infected, and 457 (45.5%) had been tested for HIV in the previous year. The testing rate of 73.1% was significantly increased from the rate of 18.0% (318 of 1,723) during the control period (p<0.001). Among the inmates tested for HIV in the prior year, 78.2% had received their last HIV test in the prison setting. Careful attention should be paid to prevent redundancy of testing efforts in the prison population. Implementing a routine HIV testing program among prison inmates greatly increased testing rates compared to on-request testing.
We reconstituted bilayer nuclear membranes, multilayer membranes, and organelles from mixtures of Xenopus laevis egg extracts and demembranated Xenopus sperm nuclei. Varying proportions of the cytosolic and vesicular fractions from the eggs were used in the reconstitution mixtures. A cytosol:vesicle ratio of 10:1 promoted reassembly of the normal bilayer nuclear membrane with inserted nuclear pore complexes around the decondensed Xenopus sperm chromatin. A cytosol:vesicle ratio of 5:1 caused decondensed and dispersed sperm chromatin to be either surrounded by or divided by unusual multilayer membrane structures with inlaid pore complexes. A cytosol:vesicle ratio of 2.5:1 promoted reconstitution of mitochondria, endoplasmic reticulum networks, and Golgi apparatus. During reassembly of the endoplasmic reticulum and Golgi apparatus, vesicular fragments of the corresponding organelles fused together and changed their shape to form flattened cisternae, which were then stacked one on top of another.
Baicalin, a naturally occurring flavonoid, was previously reported to exert anxiolytic-like effects in the Vogel conflict test. In the present study, the anxiolytic effects of baicalin alone and in combination with other anxiolytics were tested in mice using the elevated plus-maze (EPM). Baicalin treatment (7.5 - 30 mg/kg) significantly increased entries into and time spent in open arms, indicative of an anxiolytic-like effect. Motor-depressive and myorelaxant side effects commonly associated with anxiolytics were not observed with baicalin at effective anxiolytic doses in the hole-board and horizontal wire tests, respectively. Co-administration of baicalin (3.75 mg/kg) with dl-tetrahydropalmatine ( dl-THP; 0.25 mg/kg), an anxiolytic-hypnotic alkaloid, both at sub-effective doses, induced an additive effect resulting in considerable anxiolysis. Similarly, an additive anxiolytic-like effect was observed with baicalin (3.75 mg/kg) and diazepam (DZ; 0.5 mg/kg). Results obtained from this study demonstrate the potential of baicalin as a candidate anxiolytic and its possible application in multidrug therapy. Abbreviations. BZS:benzodiazepine-binding site EPM:elevated plus-maze DZ:diazepam GABA (A):type A gamma-aminobutyric acid dl-THP: dl-tetrahydropalmatine.
PURPOSE: Treatment information collected by cancer registries can be used to monitor the provision of guideline-recommended chemotherapy to colorectal cancer patients. Incomplete information may bias comparisons of these rates. We developed statistical methods that combine data from a registry and physicians' records to assess hospital quality. DATA: From California Cancer Registry data, we selected all patients (n=12,594) newly diagnosed with stage III colon cancer or stage II or III rectal cancer from 428 hospitals during the years 1994 to 1998. To assess rates and predictors of underreporting of chemotherapy, we surveyed physicians treating 1449 of these patients from 98 hospitals during the years 1996 to 1997. METHODS: Using Bayesian statistical models, we imputed unobserved treatments. We studied the impact of underreporting on provider profiling by comparing rankings, estimates, and credible intervals based only on registry data to those incorporating physician survey data. RESULTS: Analyses that account for incompleteness of reporting yielded wider credible intervals for provider profiles than those that ignored such incompleteness. Among the 109 (25%) hospitals in the highest quartile of chemotherapy rates according to the registry data, 16 were not so classified when incomplete reporting was taken into account. With the more comprehensive model, 12 hospitals could be identified that ranked in the top quartile with probability>0.90. CONCLUSION: Estimates of adjusted hospital chemotherapy rates based solely on cancer registry data overstate the precision of assessments of hospital quality. Using additional information from a physician survey and applying rigorous statistical models, better inferences can be drawn about provider quality.
Oculocutaneous albinism (OCA) is a complex genetic disease with great clinical heterogeneity. Four different types of OCA have been reported to date (OCA1, OCA2, OCA3, and OCA4). OCA4 was firstly reported in a Turkish OCA patient. The gene responsible for OCA4 is the human homologue of the mouse underwhite (uw) gene, which encodes the mem-brane-associated transporter protein (MATP). MATP gene is located on chromosome 5p13.3 and is divided into 7 exons and 6 introns. MATP gene is transcriptionally modulated by MITF, and encodes a protein of 530 amino acids. There are at least 18 pathologic mutations and 8 non-pathologic polymorphisms have been found.
Stereoselective transformation of Baylis-Hillman acetates 1 into corresponding (Z)-allyl iodides 2 has been achieved by treatment of 1 with samarium triiodide in THF. Remarkable rate acceleration of samarium triiodide-mediated iodination of 1 was found when ionic liquid 1-n-butyl-3-methyl-imidazolium tetrafluroborate ([bmim]BF(4)) was used as reaction media in stead of THF. This novel approach proceeds readily at 50 degrees C within a few minutes to afford (Z)-allyl iodides 2 in excellent yields. A mechanism involving stereoselective iodination of the acetates of Baylis-Hillman adducts by samarium triiodide is described, in which a six-membered ring transition state played a key role in the stereoselective formation of 2.
OBJECTIVE: Mutation analysis and prenatal gene diagnosis for the mutated tyrosinase (TYR) gene in two families with oculocutaneous albinism type I (OCA1). METHODS: To define the fetus genotypes and gene mutation sites, the PCR and sequencing techniques were applied to amplify and analyze the regions of exon, exon-intron and promoter of TYR gene in probands and their parents of 2 families. RESULTS: The patient or proband of family 1 showed as a compound heterozygote with mutants R278X and 929insC. However, the fetus did not get any one of the two mutations, and so was with a normal genotype and phenotype. The parents of proband in family 2 were heterozygous with IVS4+ 3A>T or G253E respectively, but their fetus was heterozygous only with IVS4+3A>T but without G253E, and so was a carrier as his father. CONCLUSION: In the mainland of China, the prenatal gene diagnosis of OCA1 is reported for the first time.
Crystallization of calcium oxalate (CaOxa) was investigated in the presence of sodium tartrate (Na2 tart) of different concentration in a gel system by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. It was found that in the presence of a low concentration of Na2tart (0.01 mol x L(-1)), calcium oxalate monohydrate (COM) is the dominant crystal phase. The percentage of calcium oxalate dihydrate (COD) is less than 5%. In the XRD pattern the main diffraction peaks are (101), (020), and (202) planes of COM crystals. In the FTIR spectrum, the main asymmetric carbonyl stretching band nu(as) (COO-) and the metal-carboxylate stretch nu(s) (COO-) of COM occur at 1 618 and 1 317 cm(-1), respectively. With the concentration of Na2 tart increasing to 0. 10 and 0. 50 mol x L(-1), the percentage of COD crystals increases to 10% and 50%, respectively, and the surface area of COM crystals decreases. The diffraction peaks that assigned to the (200), (211), (411), and (213) planes of COD crystals become stronger and stronger. The temperature can influence the modulation of Na2 tart in terms of the phase composition and morphology of CaOxa crystals. As the temperature decreases, the percentage of COD increases. At a higher temperature beyond 47 degrees C, COM is the dominant phase; but COM is dominant when the temperature is lower than 27 degrees C. The nu(as) (COO-) and nu(s), (COO-) of COD crystals occur at 1 647.6 and 1 327.7 cm(-1), respectively.
Mercury is an unnecessary element for human body, and it can exist in several physical and chemical forms in the environment. All forms of mercury have toxic effects in a number of organs, especially in the neural system and kidney. Now, with its extensive use in the industry and life, people pay more attention on the health effects which are caused by mercury. In order to know more about it and to make further study in the future, this review will make a summarize on the toxicity and its mechanism of mercury.
OBJECTIVE: To confirm the diagnosis of a human case with atypical vivax-malaria from Yunnan Province by molecular technique. METHODS: DNA was extracted from blood films of unidentified sample, and of four known Plasmodium species (P. vivax, P. falciparum, P. knowlesi, and P. cynomolgi). A DNA-based diagnosis with the polymerase chain reaction (PCR) method targeting the small subunit ribosomal RNA (SSU rRNA) genes of genus- and species-specific (two human malaria species and P. knowlesi) was introduced. RESULTS: The PCR amplification with primer pair specific for P. knowlesi produced a single fragment of 150 bp. Sequence analysis showed that the amplified fragment was identical to the sequence of P. knowlesi. CONCLUSION: The patient was naturally infected with P. knowlesi.
OBJECTIVE: To identify the recombinant aldolase (ALD) of Plasmodium falciparum, and to develop monoclonal antibodies (McAbs) against the recombinant ALD. METHODS: ALD gene was amplified by PCR from genomic DNA of FCC1/HN strain, and expressed in E. coli DH5 alpha. BALB/c mice were immunized with the recombinant ALD of P. falciparum via celiac injection for 3 times with 2 weeks interval. Three days after a booster injection, spleen cells of the immunized mice were used for producing McAbs. The immune serum was tested by IFAT and Western blotting. RESULTS: BALB/c mice immunized with purified aldolase protein developed strong immune response to the antigen, and the titer of specific antibody reached 1:10(5) in all immune sera after the third immunization. Moreover, immune sera specifically recognized the cultured P. falciparum. Western blotting showed that the immune sera recognized specifically a Mr 41000 band of crude malaria antigen. No cross-reaction with human red cells was detected. Seven positive hybridoma cell lines were obtained after 3 rows of selection. All the McAbs' subclasses belong to IgG1. IFAT showed that only 4 McAbs could recognize the cultured P. falciparum. CONCLUSION: Plasmodial aldolase has been successfully expressed and purified, and the established hybridoma cell lines can secrete McAbs specific to the aldolase of P. falciparum.
OBJECTIVE: To investigate gene mutations of a consanguineous family with two oculocutaneous albinism (OCA) patients. METHODS: Genomic DNA was prepared from peripheral leukocytes. All of the exons and flanking introns of P gene and TYR gene were PCR-direct-sequenced. Hha I restriction fragment length polymorphism in codon 787 of the P gene was studied in the family and 102 unrelated normal Chinese individuals. RESULTS: Although no mutations were found in TYR gene, a missense mutation A787T was found in P gene. Two patients of the family were both homozygous for A787T. Their parents and brother were heterozygous for the mutation. The mutation was not observed among 102 normally pigmented subjects. CONCLUSION: The A787T mutation is not a common polymorphism among normal Chinese and it seems most likely to be a pathological OCA2 mutation. This is the first report on the study of gene diagnosis in Chinese OCA2 patients.
Presenilins (PS) are required for gamma-secretase cleavage of multiple type I membrane proteins including the amyloid precursor protein and Notch and also have been implicated in regulating intracellular protein trafficking and turnover. Using genetic and pharmacological approaches, we reveal here a unique function of PS in the pigmentation of retinal pigment epithelium and epidermal melanocytes. PS deficiency leads to aberrant accumulation of tyrosinase (Tyr)-containing 50-nm post-Golgi vesicles that are normally destined to melanosomes. This trafficking is gamma-secretase-dependent, and abnormal localization of Tyr in the absence of PS is accompanied by the simultaneous accumulation of its C-terminal fragment. Furthermore, we show that the PS1M146V familial Alzheimer's disease mutation exhibits a partial loss-of-function in pigment synthesis. Our results identify Tyr and related proteins as physiological substrates of PS and link gamma-secretase activity with intracellular protein transport.
Alzheimer's disease is cytopathologically characterized by loss of synapses and neurons, neuritic amyloid plaques consisting of beta-amyloid (Abeta) peptides, and neurofibrillary tangles consisting of hyperphosphorylated tau protein in susceptible brain regions. Abeta, which triggers a cascade of pathogenic events including tau phosphorylation and neuronal excitotoxicity, is proteolytically derived from beta-amyloid precursor protein (APP); the pathological and physiological functions of APP, however, remain undefined. Here we demonstrate that the level of tau phosphorylation in cells and brains deficient in APP is significantly higher than that in wild-type controls, resulting from activation of cyclin-dependent kinase 5 (CDK5) but not glycogen synthase kinase 3, the two major tau kinases. In addition, we show that overexpression of APP or its non-amyloidogenic homolog amyloid precursor-like protein 1 suppresses both basal and stress-induced CDK5 activation. The ectodomain of APP, sAPPalpha, is responsible for inhibiting CDK5 activation. Furthermore, neurons derived from APP-deficient mice exhibit reduced metabolism and survival rates and are more susceptible to excitotoxic glutamate-induced apoptosis. These neurons also manifest significant defects in neurite outgrowth compared with neurons from the wild-type littermates. The observed neuronal excitotoxicity/apoptosis is mediated through a mechanism involving CDK5 activation. Our study defines a novel neuroprotective function for APP in preventing tau hyperphosphorylation via suppressing overactivation of CDK5. We suggest that CDK5 activation, through a calcium/calpain/p25 pathway, plays a key role in neuronal excitotoxicity and represents an underlying mechanism for the physiological functions of APP.