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Biomedical subjects

Z Wu

Publications and source records attributed to Z Wu.

At least 55 records · Page 3Linked to original sources
PubMed2003

From pro defensins to defensins: synthesis and characterization of human neutrophil pro alpha-defensin-1 and its mature domain.

Human neutrophil alpha-defensins (HNPs) are small, cationic, Cys-rich antimicrobial proteins that play important roles in innate immunity against infectious microbes such as bacteria, fungi and enveloped viruses. Synthesized as inactive precursors in vivo (pre-proHNPs), HNPs are activated through proteolytic removal of the inhibitory pro-peptide required for subcellular sorting and correct folding. We seek to understand the molecular basis for the recognition between the 45-residue pro-peptide and the C-terminal functional domain. Here we described, total chemical synthesis of the 75-residue human neutrophil pro alpha-defensin-1 (proHNP1) via native chemical ligation. After oxidative folding, proHNP1 is cleaved by cyanogen bromide at the Met45-Ala46 peptide bond to release the mature form. The native disulfide connectivity in HNP1, i.e. Cys1-Cys6, Cys2-Cys4 and Cys3-Cys5, is verified by mass mapping of peptide fragments generated by proteolytic digestion and Edman degradation. Fluorescence spectroscopy studies and antimicrobial activity assays further support that synthetic proHNP1 and HNP1 are correctly folded. While largely unstructured in aqueous solution, the pro-peptide binds to HNP1 intermolecularly with an apparent Kd value of 6.2 microM at pH 7.4, confirming the mode of intramolecular inactivation of human alpha-defensin precursors.

Amino Acid Sequence↗
PubMed2003

Both fasting-induced leptin reduction and GH increase are blunted in Cushing's syndrome and in simple obesity.

BACKGROUND: Simple obesity and Cushing's syndrome (CS) are two clinical models of leptin hypersecretion coupled with GH hyposecretion. Fasting inhibits leptin while stimulating GH secretion in normal human subjects. OBJECTIVES: To clarify the effect of fasting on leptin and GH secretion in obesity and CS. PATIENTS AND PROTOCOL: We studied six women with CS [age 17-66 years; body mass index (BMI) 28.6 kg/m2], seven women with visceral obesity (OB; 20-41 years; BMI 42.9 kg/m2) and seven normal women (NS; 25-31 years; BMI 19.3 kg/m2). The effects of 36-h fasting on 8-h diurnal mean leptin, GH, insulin and glucose concentrations (mLEPTc, mGHc, mINSc and mGLUc) as well as on the IGF/IGFBP system were studied. RESULTS: Before fasting, mLEPTc in OB and in CS were similar and both were higher (P < 0.01) than in NS. OB and CS showed similar mGHc, which were lower (P < 0.05) than in NS. Fasting induced a reduction in mLEPTc that was significant in NS and CS (P < 0.04) but not in OB. The mLEPTc in OB and CS after fasting remained higher (P < 0.05) than in NS. After fasting, OB and CS showed no increase in mGHc, although this clearly increased (P < 0.02) in NS. IGF-I but not IGFBP-3 levels decreased in all groups (P < 0.05). Fasting reduced mINSc and mGLUc while increasing IGFBP-1 in all groups. After fasting, mINSc in OB and CS remained higher (P < 0.03) than in NS. CONCLUSIONS: Short-term fasting has less inhibitory effect on leptin and no stimulatory effect on GH secretion in patients with Cushing's syndrome as well as simple obesity. After fasting, insulin levels in hypercortisolaemic and also in obese patients remained higher than in normal subjects suggesting that hyperinsulinism could play a role in the altered response of leptin and GH to starvation in these conditions.

Adolescent↗
PubMed2003

Molecular cloning and expression of the full-length tropomyosin gene from Trichinella spiralis.

A clone, designated as TsTM, was selected from the cDNA library of newborn larvae (NBL) of Trichinella spiralis through immunoscreening against infected sera. The clone contained a cDNA transcript of 855 bp in length with a single open reading frame, which encoded 285-amino acids (33 kDa in the estimated molecular weight). A sequence analysis revealed that the clone TsTM encoded the full-length of tropomyosin gene. The phylogenetic analysis of the tropomyosin gene was in good agreement with the classical taxonomical position of T. spiralis. The fusion proteins encoded by the clone TsTM were produced in an Escherichia coli expression system and affinity purified, and the antibody was raised against the protein for the following studies. The antibody against the fusion protein positively bound to the hypodermal muscle layer in immunolocalization analysis, and the 35 kDa band in crude extracts of muscle larvae but not in excretory and secretory (ES) products on Western blots. The antigenicity of the clone TsTM was recognized by host mice but exhibited little species specificity.

Amino Acid Sequence↗
PubMed2003

Cholesterol, coronary heart disease, and stroke in the Asia Pacific region.

BACKGROUND: Cholesterol levels in many Asian countries are rising. Predictions of the likely effects of this on the incidence of cardiovascular diseases have mostly relied on data from Western populations. Whether the associations between total cholesterol and cardiovascular diseases are similar in Asia is not established. METHODS: The Asia Pacific Cohort Studies Collaboration (APCSC) is an individual-participant data meta-analysis of prospective studies from the Asia-Pacific region. Cox models were applied to the combined data from 29 cohorts to estimate the region-, sex-, and age-specific hazard ratios of major cardiovascular diseases by the fifths of total cholesterol. RESULTS: At baseline, the age/sex-adjusted mean value of total cholesterol was higher in Australia and New Zealand (ANZ) (5.52 +/- 1.05 mmol/l) than in Asia (4.87 +/- 1.05 mmol/l). During 2 million person-years of follow-up among 352 033 individuals, 4841 cardiovascular deaths were recorded. The association of total cholesterol with coronary heart disease and stroke was similar in Asian and ANZ cohorts. Overall, each 1-mmol/l higher level of total cholesterol was associated with 35% (95% CI: 26-44%) increased risk of coronary death, 25% (95% CI: 13-40%) increased risk of fatal or non-fatal ischaemic stroke, and 20% (95% CI: 8-30%) decreased risk of fatal haemorrhagic stroke. CONCLUSIONS: In both Asian and non-Asian populations in the Asia-Pacific region, total cholesterol is similarly strongly associated with the risk of CHD and ischaemic, but not haemorrhagic, stroke. Rising population-wide levels of cholesterol would be expected to contribute to a substantial increase in the overall burden of cardiovascular diseases in this region.

Adult↗
PubMed2003

Association between the GH receptor/exon 3 genotype and the level of exon 3-positive GH-binding protein in human serum.

OBJECTIVE: The human GH-binding protein (GHBP) is derived from the GH receptor (GHR) through proteolytic cleavage of its extracellular domain. Two isoforms of the GHBP exist, differing in the retention or exclusion of exon 3: E3(+)GHBP and E3(-)GHBP. Our study aimed to answer the questions whether the level of E3(+)GHBP in the serum correlates with the GHR exon 3 expression and whether or not the E3 genotype matches the mRNA expression pattern. METHODS: Since exon 3 retention/deletion can be detected at the protein level using epitope-specific antibodies, we were able to quantify the two isoforms by means of specific immunoassays in a total of 37 individuals. Additionally, these persons were also genotyped for exon 3 by genomic PCR and tested for GHR exon 3 mRNA expression by RT-PCR. RESULTS: We found a significant correlation between GHR exon 3 genotype and the ratio of E3(+)GHBP and E3(-)GHBP in the serum. Moreover, the genotype matched exactly the mRNA expression in fibroblasts and/or blood leukocytes in all samples investigated. The levels of E3(+)GHBP are more strongly correlated with body mass index, proinsulin and C-peptide than the levels of the E3(-) isoform. CONCLUSIONS: Our results show that the GHR exon 3 genotype is in accord with the type of GHBP isoforms found in the serum. Our data thus support the idea that the presence of exon 3-retaining and -excluding GHR/GHBP isoforms results from a genomic deletion rather than from alternative splicing.

Adolescent↗
PubMed2003

Molecular expression and characterization of a homologue of host cytokine macrophage migration inhibitory factor from Trichinella spp.

A homologue of cytokine macrophage migration inhibitory factor (MIF) from complementary DNA (cDNA) of Trichinella spiralis and Trichinella pseudospiralis was expressed in Escherichia coli and characterized. The sequence analysis indicated that the predicted amino acid sequence has an identity of 57 and 44% with the MIF of nematodes Trichuris trichiura and Brugia malayi respectively, and 41 and 40% with that of a human and a mouse, respectively. The identity in sequences of cDNA and amino acids between T. spiralis and T. pseudospiralis was 91 and 86%, respectively. Western blot analysis showed that anti-MIF antibodies positively stained proteins from the extracts of adult worms or muscle larvae migrating at about 12.5 kDa (3 isoforms with isoelectric point 5.23, 5.72, and 6.29). Semiquantitative reverse transcriptase-polymerase chain reaction revealed that the gene was expressed in various developmental stages, including in adult worms, newborn larvae, precyst muscle larvae, and postcyst muscle larvae, although there was difference in the expression level among these stages. The immunohistochemical analysis showed the MIF exists in the muscle cells of the body wall and some stichocytes of larvae. Histopathology of T. spiralis-infected muscles revealed an accumulation of mononuclear cells around the worms, and immunocytochemical staining showed these cells were not macrophages. Mononuclear cells, including macrophages, were, however, observed in cardiac muscles where the parasite did not encyst. Macrophages accumulated around the Sephadex beads transplanted in mice subcutaneously, but this accumulation was profoundly inhibited when the beads were pretreated with MIF recombinant protein.

Amino Acid Sequence↗
PubMed2003

Utilization of phosphorus in lactating cows fed varying amounts of phosphorus and forage.

The objective of this study was to determine the effect of dietary forage proportion and P content on fecal P excretion. Four dietary treatments were formed in a 2 x 2 factorial arrangement. The P content was 0.33 or 0.42%, and the forage proportion was 48 or 58% on a dry matter (DM) basis. The neutral detergent fiber content was 27 and 30% for the low and high forage diets, respectively. The P amount was varied by using monosodium phosphate, and the forage amount by changing the proportions of alfalfa silage and corn. The diets were fed to 44 midlactation Holsteins for 14 wk. Fecal P excretion was estimated using Cr marker and grab sampling. Dietary P content did not affect DM intake, milk yield, or milk composition. The P intake averaged 74 and 96 g/d and fecal P averaged 0.69 and 0.92% (DM basis) or 49 and 65 g/d for the low and high P diets, respectively. Thus, reducing dietary P from 0.42 to 0.33% resulted in approximately 25% less estimated fecal P excretion. Increasing dietary forage reduced milk yield (34.0 vs. 36.5 kg/d), but increased milk fat content (3.66 vs. 3.25%). Estimated apparent digestibility of P tended to decrease (31.1 vs. 36.6%) when the forage proportion increased, but most of the change occurred when the diets contained the low amount of P. Overall, the effect of forage proportion on estimated fecal P excretion was small when diets contained 48 or 58% forage, varied by alfalfa silage. Phosphorus intake has a much larger impact on fecal P excretion than forage proportion, and it does not seem necessary to adjust the dietary P content according to the forage proportion to provide the same amount of absorbed P.

Animals↗
PubMed2003

Phosphorus feeding levels and critical control points on dairy farms.

A viable and cost-effective approach to managing P on dairy farms is to minimize excess P in diets, which in turn leads to less excretion of P in manure without impairing animal performance. A questionnaire survey was conducted, coupled with on-site feed and fecal sample collection and analysis on dairy farms in New York, Pennsylvania, Delaware, Maryland, and Virginia. The purpose was to assess dietary P levels and to identify critical control points pertaining to P feeding management. Survey responses, 612 out of 2500 randomly selected farms, revealed a wide range of dietary P concentrations for lactating cows, from 3.6 to 7.0 g/kg of feed DM. The mean was 4.4 g/kg, which was 34% above the level recommended by the NRC for 27.9 kg milk/d, the mean milk yield in the survey. Higher P concentrations in diets were not associated with higher milk yields (n = 98, R2 = 0.057 for the survey farms; n = 92, R2 = 0.043 for farms selected for on-site sampling). However, higher dietary P led to higher P excretion in feces (n = 75, R2 = 0.429), with much of the increased fecal P being water soluble. Phosphorus concentrations in diet samples matched closely with P concentrations in formulated rations, with 67% of the feed samples deviating <10% from the formulations. On 84% of the survey farms, ration formulation was provided by professionals rather than producers themselves. Most producers were feeding more P than cows needed because it was recommended in the rations by these consultants. In conclusion, P fed to lactating cows averaged 34% above NRC recommendations; to reduce excess dietary P, ration formulation is the critical control point.

Animal Feed↗
PubMed2002

Molecular cloning and characterization of a novel protein of Trichinella pseudospiralis excretory-secretory products.

A novel excretory-secretory (ES) protein of Trichinella pseudospiralis was produced. A cDNA library was constructed from mRNA of muscle larvae at 30 days post infection (p.i.) and immunoscreened with the antibody against ES products. A clone, designated Tp22-3, contained a cDNA transcript of 815 bp in length with a single open reading frame which encoded 244-amino acids (28407 Da in the estimated molecular mass). A database search revealed that no sequences had a homology to this predicted protein. The recombinant protein was produced in an Escherichia coli expression system. Stage specific expression of this protein was suggested from the following experiments. An antibody against the recombinant protein could stain proteins migrating at about 28 kDa (which is the expected size from the sequence) on Western blotting of crude extracts or ES products from 30 days p.i. muscle larvae, but failed to stain any proteins in crude extracts from newborn larvae or 15 days p.i. muscle larvae. The antibody reacted to the stichocytes of larvae at 30 days p.i., but did not react to 15 days p.i. muscle larvae. The production of an mRNA transcript for Tp22-3 gene was restricted largely to the 30 days p.i. muscle larvae and adult worms.

Amino Acid Sequence↗
PubMed2002

Impact of experimental blockade of peripheral growth hormone (GH) receptors on the kinetics of endogenous and exogenous GH removal in healthy women and men.

Organs that respond to and metabolize GH are enriched in cognate high-affinity receptors. However, whether isologous receptors mediate the de facto access of ligand to cellular degradative pathways is not known. To address this query, we assessed the distribution and whole-body elimination kinetics of (endogenous and exogenous) GH before and after administration of a novel, potent, and selective recombinant human (rh) GH receptor antagonist peptide, pegvisomant. Sixteen healthy young adults (nine men and seven women) participated in a double-blind, prospectively randomized, within-subject cross-over study. The intervention comprised a single sc injection of placebo vs. a high dose of pegvisomant (1 mg/kg sc) timed 62 and 74 h before the overnight sampling and daytime infusion sessions, respectively. The half-life, metabolic clearance rate (MCR), and distribution volume of GH were quantitated by way of: 1) deconvolution analysis of serum GH concentration time series collected every 10 min for 10 h; 2) exponential regression analysis of the decay of GH concentrations after a 6-min iv pulse of rhGH (1 and 10 micro g/kg); 3) calculation of the MCR during constant iv infusion of rhGH (0.5 and 5.0 micro g/kg every 2 h); and 4) exponential fitting of the elimination time-course of GH concentrations following cessation of each constant infusion. Concentrations of GH and pegvisomant were measured in separate, noncross-reactive, two-site monoclonal, immunofluorometric assays. Pegvisomant concentrations averaged 4860 +/- 480 micro g/liter (+/-SEM) across the infusion interval, thus exceeding low steady state GH concentrations by 3000-fold. Inhibitory efficacy of the GH receptor antagonist peptide was affirmed by way of a 34% reduction in the serum total IGF-I concentration, i.e., from 257 +/- 37 (placebo) to 170 +/- 24 (drug) micro g/liter (P < 0.001); and a reciprocal 77% elevation of the (10-h) mean GH concentration, i.e., from 1.3 +/- 0.23 (placebo) to 2.3 +/- 0.42 (drug) micro g/liter (P = 0.003). ANOVA disclosed that prior administration of pegvisomant (compared with placebo) did not alter: 1) the calculated half-life (minutes) of secreted GH, which averaged 15 +/- 1.3 (placebo) and 14 +/- 0.69 (drug); 2) the half-time of disappearance (minutes) of an iv pulse of rhGH, 15 +/- 1.0 (placebo) and 13 +/- 0.5 (drug) (for the 10 micro g/kg dose); 3) the distribution volume (milliliters per kilogram) of rhGH, 59 +/- 6.2 (placebo) and 58 +/- 3.5 (drug); 4) the steady state GH concentration (micrograms per liter) attained during constant iv infusion of rhGH (at a rate of 5 micro g/kg every 2 h), 18.2 +/- 2.4 (placebo) and 18.3 +/- 2.3 (drug); 5) the half-life (minutes) of elimination of GH from equilibrium, 16 +/- 0.98 (placebo) and 16 +/- 1.8 (drug); and 6) the steady state MCR (liters per kilogram per day) of rhGH, 3.8 +/- 0.32 (placebo) and 3.5 +/- 0.31 (drug). In ensemble, the present data refute the a priori postulate that vascular-accessible GH receptors determine the in vivo pseudoequilibrium kinetics of GH disappearance in the human.

Adult↗
PubMed2002

Biological effects of hyperbaric oxygen on human severe periodontitis.

This paper reports the effects of Hyperbaric Oxygen (HBO2) in a controlled study of periodontitis in 24 patients. The patients received either HBO2 or no HBO2, and study teeth were divided into 4 groups based on treatment: 1-HBO2 therapy, 2-HBO2 + scaling, 3-scaling, 4-control. We measured indices of periodontal disease and gingival blood flow (GBF). The microorganisms in a periodontal pocket were stained and the percentage of straight rods (Rods), curved rods (Cur), fusiforms (Fusi) and spirochetes (Spiro) were observed. The numbers of anaerobic organisms were measured by routine anaerobic culture. Highly significant differences in Gingival Indices (GI), Sulcus Bleeding Indices (SBI), Probing Depth (PD), Attachment Loss (AL), Plaque Index (PLI), and GBF were seen in the HBO2, the HBO2 + Scaling and the Scaling Groups compared to the Control Group (P < 0.01). The number of subgingival anaerobes as well as the number of Rods, Cur, Fusi, and Spiro were reduced markedly in these three treatment groups. Statistically greater differences in clinical indices, GBF, subgingival anaerobe number and number of Rods, Cur, Fusi and Spiro were found by comparison of HBO2 + Scaling and HBO2 Groups, as well as between the HBO2 + Scaling and Scaling Groups, but no significant differences were observed in GI, SBI, PD, or AL between the HBO2 and Scaling Groups. In conclusion, HBO2 had beneficial therapeutic effects on severe periodontitis. HBO2 therapy combined with scaling and root planing was the most beneficial in the treatment of periodontitis. Clinical follow-up suggests that this treatment effect could last more than 1 year.

Adolescent↗
PubMed2001

The genome of the natural genetic engineer Agrobacterium tumefaciens C58.

The 5.67-megabase genome of the plant pathogen Agrobacterium tumefaciens C58 consists of a circular chromosome, a linear chromosome, and two plasmids. Extensive orthology and nucleotide colinearity between the genomes of A. tumefaciens and the plant symbiont Sinorhizobium meliloti suggest a recent evolutionary divergence. Their similarities include metabolic, transport, and regulatory systems that promote survival in the highly competitive rhizosphere; differences are apparent in their genome structure and virulence gene complement. Availability of the A. tumefaciens sequence will facilitate investigations into the molecular basis of pathogenesis and the evolutionary divergence of pathogenic and symbiotic lifestyles.

Agrobacterium tumefaciens↗
PubMed2001

Crystal structure of a cyclic form of bovine pancreatic trypsin inhibitor.

The crystal structure of a cyclic form of a mutant of bovine pancreatic trypsin inhibitor has been solved at 1.0 A resolution. The protein was synthesized by native chemical ligation and its structure is almost indistinguishable from the previously described recombinant form of the same mutant; however, the new loop containing the former termini became much better ordered.

Animals↗
PubMed2001

A fast Newton method for entropy maximization in statistical phase estimation.

A fast Newton method is presented for solving the entropy maximization problem in the Bayesian statistical approach to phase estimation. The method requires only O(n log n) instead of standard O(n3) floating point operations per iteration, while converging in the same rate as the standard Newton method. The method is described and related computational issues are discussed. Numerical results on simple test cases are also presented to demonstrate the behavior of the method.

Journal Article↗
PubMed2001

High-dose leptin activates human leukocytes via receptor expression on monocytes.

Leptin is capable of modulating the immune response. Proinflammatory cytokines induce leptin production, and we now demonstrate that leptin can directly activate the inflammatory response. RNA expression for the leptin receptor (Ob-R) was detectable in human PBMCs. Ob-R expression was examined at the protein level by whole blood flow cytometry using an anti-human Ob-R mAb 9F8. The percentage of cells expressing leptin receptor was 25 +/- 5% for monocytes, 12 +/- 4% for neutrophils, and 5 +/- 1% for lymphocytes (only B lymphocytes). Incubation of resting PBMCs with leptin induced rapid expression of TNF-alpha and IL-6 mRNA and a dose-dependent production of TNF-alpha and IL-6 by monocytes. Incubation of resting PBMCs with high-dose leptin (250 ng/ml, 3-5 days) induced proliferation of resting cultured PBMCs and their secretion of TNF-alpha (5-fold), IL-6 (19-fold), and IFN-gamma (2.5-fold), but had no effect on IL-4 secretion. The effect of leptin was distinct from, and additive to, that seen after exposure to endotoxin or activation by the mixed lymphocyte reaction. In conclusion, Ob-R is expressed on human circulating leukocytes, predominantly on monocytes. At high doses, leptin induces proinflammatory cytokine production by resting human PBMCs and augments the release of these cytokines from activated PBMCs in a pattern compatible with the induction of Th1 cytokines. These results demonstrate that leptin has a direct effect on the generation of an inflammatory response. This is of relevance when considering leptin therapy and may partly explain the relationship among leptin, proinflammatory cytokines, insulin resistance, and obesity.

Adult↗
PubMed2001

Photochemically enhanced binding of small molecules to the tumor necrosis factor receptor-1 inhibits the binding of TNF-alpha.

The binding of tumor necrosis factor alpha (TNF-alpha) to the type-1 TNF receptor (TNFRc1) plays an important role in inflammation. Despite the clinical success of biologics (antibodies, soluble receptors) for treating TNF-based autoimmune conditions, no potent small molecule antagonists have been developed. Our screening of chemical libraries revealed that N-alkyl 5-arylidene-2-thioxo-1,3-thiazolidin-4-ones were antagonists of this protein-protein interaction. After chemical optimization, we discovered IW927, which potently disrupted the binding of TNF-alpha to TNFRc1 (IC(50) = 50 nM) and also blocked TNF-stimulated phosphorylation of Ikappa-B in Ramos cells (IC(50) = 600 nM). This compound did not bind detectably to the related cytokine receptors TNFRc2 or CD40, and did not display any cytotoxicity at concentrations as high as 100 microM. Detailed evaluation of this and related molecules revealed that compounds in this class are "photochemically enhanced" inhibitors, in that they bind reversibly to the TNFRc1 with weak affinity (ca. 40-100 microM) and then covalently modify the receptor via a photochemical reaction. We obtained a crystal structure of IV703 (a close analog of IW927) bound to the TNFRc1. This structure clearly revealed that one of the aromatic rings of the inhibitor was covalently linked to the receptor through the main-chain nitrogen of Ala-62, a residue that has already been implicated in the binding of TNF-alpha to the TNFRc1. When combined with the fact that our inhibitors are reversible binders in light-excluded conditions, the results of the crystallography provide the basis for the rational design of nonphotoreactive inhibitors of the TNF-alpha-TNFRc1 interaction.

Antigens, CD↗
PubMed2001

Identification and determination of glucuronides and their aglycones in Erigeron breviscapus by liquid chromatography-tandem mass spectrometry.

A novel, speedy and reliable LC-MS-MS method for the search, identification and quantitation of O-glycosides and their aglycones from plant resources was established by analyzing the extract of Erigeron breviscapus. The extract was directly infused to a triple-quadrupole MS-MS and major glucuronides in the extract were screened out with high confidence by a neutral loss scan for the loss of a gluconic acid. The identity of these glucuronides and their aglycones was further confirmed with LC-MS-MS. In addition to scutellarin, apigenin 7-O-glucuronide, quercetin-3-O-glucuronide and their aglycones that were previously reported by others, we also confirmed by LC-MS-MS that remarkable amount of baicalin, an isomer of apigenin 7-O-glucuronide, presented in the extract of this plant, which had not been reported before. A satisfying quantitation of three glucuronides was also made by LC-MS-MS.

Asteraceae↗