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Biomedical subjects

Y Q Tang

Publications and source records attributed to Y Q Tang.

At least 19 recordsLinked to original sources
PubMed2002

Effect of neem seed extract on feeding, growth, survival, and reproduction of Diaprepes abbreviatus (Coleoptera: Curculionidae).

A commercially available neem seed extract, Neemix 4.5, containing 4.5% azadirachtin (AZA), was assessed for biological activity against the root weevil Diaprepes abbreviatus (L.), an important exotic insect pest of Florida citrus. Laboratory bioassays against neonatal and 3-wk-old larvae fed sliced carrot treated with Neemix produced dose-dependent larval mortality and reduced fresh weights among survivors of treatments. The weight response was greater than the mortality response for both larval age groups. Neonates treated with 45 mg/liter AZA weighed 60% less than those in the control after 4 wk. Three-week-old larvae treated with 45 mg/ liter AZA weighed 30% less than those in the control after 5 wk. When neonates were exposed to insect diet incorporated with Neemix, reductions in larval survival and weight were observed at concentrations as low as 4.8 mg/liter AZA after 6 wk. Larval growth was inhibited by >97% with 42.9 mg/liter AZA in the diet. A soil drench containing 30 mg/liter AZA reduced the survival and weight gain of neonates added to potted citrus and provided protection to the roots in a greenhouse experiment. A concentration of 90 mg/liter AZA was required to provide protection of citrus roots against 4-wk-old larvae. Reproductive effects were observed when adult weevils were fed foliage treated with Neemix. The numbers of larvae hatching per egg mass were reduced by 27% and 68% at 30 and 90 mg/liter AZA, respectively. These results suggest that Neemix should be further evaluated for use in integrated pest management (IPM) programs of citrus.

Animals↗
PubMed2001

Conformational adjustments of SNase R and its N-terminal fragments probed by monoclonal antibodies.

Two monoclonal antibodies specific for staphylococcal nuclease R (SNase R) (McAb2C9 and McAb1B8) were prepared and used to probe protein folding during peptide elongation, by measuring antibody binding to seven N-terminal fragments (SNR141, SNR135, SNR121, SNR110, SNR102, SNR79 and SNR52) of SNase R. Comparative studies of the conformations of the N-terminal fragments have shown that all seven fragments of SNase R have a certain amount of residual structure, indicating that folding may occur during elongation of the nascent peptide chain. We show that the binding abilities of the intact enzyme and its seven fragments to the monoclonal antibodies are not simply proportional to the length of the peptide chain, suggesting that there may be continuous conformational adjustment in the nascent peptide chain as new C-terminal amino acids are added. A folding intermediate close in structure to the native state but with structural features in common with SNR121 is highly populated in 0.6 M GuHCl, and is also formed transiently during folding.

Antibodies, Monoclonal↗
PubMed2000

Feigrisolides A, B, C and D, new lactones with antibacterial activities from Streptomyces griseus.

Four new lactone compounds, named feigrisolides A to D (1 to 4), have been isolated from Streptomyces griseus. The chemical structures were determined by detail analysis of their spectroscopic data and chemical transformations. Structurally, the feigrisolides A (1) and B (2) are hepta-lactones, feigrisolide C (3) and D (4) are 16-membered macrodiolides. Biological studies showed that feigrisolide B (2) exhibited strong antibacterial, as well as medium cyctotoxic, and antiviral activities. Feigrisolides A (1), C (3) and D (4) are medium inhibitors of 3alpha-hydroxysteroid-dehydrogenase (3alpha-HSD) inhibiting activity.

Anti-Bacterial Agents↗
PubMed1999

A cyclic antimicrobial peptide produced in primate leukocytes by the ligation of two truncated alpha-defensins.

Analysis of rhesus macaque leukocytes disclosed the presence of an 18-residue macrocyclic, tridisulfide antibiotic peptide in granules of neutrophils and monocytes. The peptide, termed rhesus theta defensin-1 (RTD-1), is microbicidal for bacteria and fungi at low micromolar concentrations. Antibacterial activity of the cyclic peptide was threefold greater than that of an open-chain analog, and the cyclic conformation was required for antimicrobial activity in the presence of 150 millimolar sodium chloride. Biosynthesis of RTD-1 involves the head-to-tail ligation of two alpha-defensin-related nonapeptides, requiring the formation of two new peptide bonds. Thus, host defense cells possess mechanisms for synthesis and granular packaging of macrocyclic antibiotic peptides that are components of the phagocyte antimicrobial armamentarium.

Amino Acid Sequence↗
PubMed1999

Isolation, characterization, cDNA cloning, and antimicrobial properties of two distinct subfamilies of alpha-defensins from rhesus macaque leukocytes.

Experiments to isolate and characterize rhesus macaque myeloid alpha-defensins (RMADs) were conducted. Seven RMAD peptides were isolated and sequenced, and the cDNAs encoding six of these peptides and one other alpha-defensin from bone marrow were also characterized. Four of the RMADs were found to be highly similar to human neutrophil alpha-defensins HNP-1 to HNP-3, while the remaining four peptides were much more similar to human enteric alpha-defensin HD-5. Two alpha-defensin pairs differed only by the presence or absence of an additional arginine at the amino termini of their mature peptides, indicative of alternate posttranslational processing. The primary translation products of RMAD-1 to -8 are 94- and 96-amino-acid prepropeptides that are highly similar to those of human alpha-defensins. Immunolocalization experiments revealed a granular cytoplasmic pattern in the cytoplasms of neutrophils, indistinguishable from the pattern observed after immunostaining of human myeloid alpha-defensins in polymorphonuclear leukocytes. Each of the purified peptides was tested for its in vitro activities against Staphylococcus aureus 502a, Listeria monocytogenes EGD, Escherichia coli ML35, and Cryptococcus neoformans 271A. Several of the peptides were microbicidal for the gram-positive bacteria and C. neoformans at defensin concentrations in the range of 2 to 5 microM. All of the peptides were bacteriostatic against E. coli, but none were bactericidal for this organism. This study is the first to characterize the sequences and activities of alpha-defensins from nonhuman primates, data that should aid in delineating the role of these peptides in rhesus macaque host defense.

Amino Acid Sequence↗
PubMed1999

A comparison of laparoscopic surgery and laparotomy in the treatment of ectopic pregnancy.

OBJECTIVES: To compare the laparoscopic approach with laparotomy in the treatment of ectopic pregnancy. The aim of this study was to evaluate the efficiency of laparoscopic surgery for ectopic pregnancies in China. METHOD: A retrospective analysis involving 142 patients with ectopic pregnancies was done. Seventy-two of the 142 patients were treated laparoscopically. RESULTS: In the laparoscopic group, the operating time and post-hospital stay were significantly shorter but the total cost was higher compared with the laparotomy group. CONCLUSION: Although the laparoscopic surgery for ectopic pregnancies is a new approach and it is not widely practiced in China; it has more advantages than open surgery and it has been well accepted by the surgeons and patients. It is a safe and feasible approach, but the rate of laparoscopic approach for ectopic pregnancy is still low in China when compared with the developed countries.

China↗
PubMed1997

Purification and in vitro activities of rabbit platelet microbicidal proteins.

Recent in vitro studies have demonstrated that rabbit platelets release a small, cationic antimicrobial protein in response to thrombin stimulation under physiological conditions (M. R. Yeaman, S. M. Puentes, D. C. Norman, and A. S. Bayer, Infect. Immun. 60:1202-1209, 1992). This observation prompted our present investigation, focused on determining the array of antimicrobial proteins contained within rabbit platelets and their in vitro activity against common bloodstream pathogens. A group of small (6.0- to 9.0-kDa), cationic proteins with in vitro antimicrobial activity was purified from whole and thrombin-stimulated rabbit platelets by gel filtration and reversed-phase high-performance liquid chromatography. Purified proteins in micromolar concentrations (10 to 40 microg/ml) exerted in vitro microbiostatic and/or microbicidal activities against Staphylococcus aureus, Escherichia coli, and Candida albicans in a dose-dependent manner. The antimicrobial activities of proteins purified from rabbit platelet acid extracts were generally inversely related to pH, with maximal activity observed at pH 5.5. In contrast, the predominant protein isolated from thrombin-stimulated rabbit platelets, though biochemically and microbiologically similar to proteins extracted by acid, exhibited antimicrobial activities which were modestly enhanced at pH 7.2 compared with pH 5.5. Amino acid compositional analyses in combination with molecular mass determinations suggest that the majority of these proteins are distinct molecules not derived from a single common precursor. Collectively, these data indicate that rabbit platelets contain proteins which exert potent in vitro antimicrobial activity against bacterial and fungal pathogens which commonly invade the bloodstream. Moreover, several of these proteins were released from platelets stimulated with thrombin under physiological conditions and exerted potent antimicrobial activities in physiological pH ranges. These observations support the hypothesis that platelets serve an important role in host defense against infection, via localized release of antimicrobial proteins in response to stimuli associated with tissue injury or microbial colonization.

Amino Acids↗
PubMed1995

Synthesis and characterization of indolicidin, a tryptophan-rich antimicrobial peptide from bovine neutrophils.

Indolicidin, a novel tryptophan-rich microbicidal tridecapeptide amide isolated originally from granules of bovine neutrophils, has been prepared by optimized manual and automated protocols of stepwise solid-phase synthesis with N alpha-9-fluorenylmethyloxycarbonyl (Fmoc) amino acid derivatives. Both standard polystyrene (PS) and polyethylene glycol-polystyrene (PEG-PS) graft supports were used in combination with handles that provide C-terminal peptide amides: 5-(4-Fmoc-aminomethyl-3,5-dimethoxyphenoxy)valeric acid (PAL) or 5-(9-Fmoc-aminoxanthen-2-oxy)valeric acid (XAL). Final deprotection/cleavage was carried out with reagent K, trifluoroacetic acid-phenol-water-thioanisole-1,2-ethanedithiol (82.5:5:5:5:2.5), or reagent B, trifluoroacetic acid-phenol-water-tri(isopropyl)silane (88:5:5:2), and related cocktails. Initial purities as high as 93% were obtained immediately following cleavage. In the largest-scale synthesis carried out, 0.8 g of HPLC-purified indolicidin (> 99% pure) was obtained, representing a 39% overall yield based on C-terminal Arg(Pmc) anchored to PAL-PS-resin. The main synthetic product, and some by-products, were characterized by analytical high-performance liquid chromatography (HPLC), sequencing, and fast atom bombardment mass spectrometry (FABMS). The antimicrobial potencies of natural and synthetic indolicidin, as determined by in vitro antibacterial and antifungal assays, were identical. Further, the reactivities of natural and synthetic peptides with anti-indolicidin antibody were indistinguishable.

Animals↗
PubMed1993

Purification, primary structures, and antibacterial activities of beta-defensins, a new family of antimicrobial peptides from bovine neutrophils.

A new family of cysteine-rich antimicrobial peptides from bovine neutrophils was isolated and characterized. Thirteen structurally homologous peptides were purified to homogeneity from a granule-rich cytoplasmic fraction of purified blood neutrophils. The complete sequences of the peptides were determined by a combination of enzymatic digestion, Edman degradation, and additional biochemical characterization of the carboxyl termini. The peptides are characterized by a highly cationic 38-42-residue chain which includes 6 invariantly spaced cysteines which form three disulfides. They share a highly conserved consensus sequence which is also found in a recently described epithelial antimicrobial peptide from bovine trachea. The in vitro antibacterial activities of the 13 neutrophil peptides, determined in assays using Staphylococcus aureus and Escherichia coli as test organisms, demonstrated that each peptide possessed antimicrobial activity, and that several were as active as the most potent neutrophil defensin, rabbit NP-1. Though the structural and functional attributes of the bovine neutrophil peptides are similar to those of defensins, the two peptide families are distinguished by their unique consensus sequences and additionally by differing tridisulfide motifs. We therefore propose that this new defensin-like antimicrobial peptide family be named beta-defensins.

Amino Acid Sequence↗
PubMed1993

Characterization of the disulfide motif in BNBD-12, an antimicrobial beta-defensin peptide from bovine neutrophils.

BNBD-12, a prototype beta-defensin peptide from bovine neutrophils, was chosen for determination of the disulfide motif in this family of tridisulfide antimicrobial peptides. Disulfide-containing fragments of BNBD-12 were generated by incubation with trypsin, and the amino acid composition of one tryptic fragment allowed for the assignment of one of the three disulfides. The remaining two disulfides, contained in a 16-residue tryptic oligopeptide, were characterized by amino acid analysis of fragments generated by a single round of Edman degradation which cleaved the Cys-Cys peptide bond present near the carboxyl terminus of BNBD-12. Cleavage of this bond produced two disulfide-containing oligopeptides, the compositions of which provided unambiguous assignments of the disulfides involved. The cystine motif in BNBD-12 differs from that of classical defensins, and indicates that the beta-defensins and defensins must have differently folded chains, though they share several functional properties.

Amino Acid Sequence↗
PubMed1993

Phyletic relationships of protein structures based on spatial preference of residues.

A structure-based scoring matrix MDPRE was derived from amino acid spatial preferences in protein structures. Sequence alignment and evolutionary studies by using MDPRE matrix gave similar results as those from ordinary sequence and structure alignments. It is interesting that a matrix derived from structure data solely could give comparable alignment results, strongly indicating the intimate connection between protein sequences and structures. The branch order and length from this approach were close to those obtained by a structure comparison method. Thus, by applying this structure-based matrix, the trees obtained should reflect evolutionary characteristics of protein structure. This approach takes advantage over a direct structure comparison in that (1) only a sequence and MDPRE matrix are needed, making it simple and widely applicable (especially in the absence of 3-dimensional protein structure data); (2) an established algorithm for sequence alignment and tree building could be employed, providing opportunities for direct comparison between matrices from different methodologies. One of the most striking features of this method is its capability to detect protein structure homologies when the sequence identities are low. This was well reflected in the given examples of the alignment of dinucleotide-binding domains.

Amino Acid Sequence↗
PubMed1992

Indolicidin, a novel bactericidal tridecapeptide amide from neutrophils.

A potent and structurally novel antimicrobial peptide was purified from the cytoplasmic granules of bovine neutrophils. Suspensions of Staphylococcus aureus and Escherichia coli were virtually sterilized by the peptide at a concentration of 10 micrograms/ml. The peptide was found to be comprised of 13 amino acids, 5 of which were tryptophan residues, and the carboxyl-terminal arginine was carboxamidated. The primary structure of the peptide, which we have named indolicidin, is H-Ile-Leu-Pro-Trp-Lys-Trp-Pro-Trp-Trp-Pro-Trp-Arg-Arg-NH2. The mole percent of tryptophan in indolicidin is the highest observed among known protein sequences. The multiple tryptophan residues presumably play an important role in the function of this unique antibiotic peptide.

Amino Acid Sequence↗
PubMed1992

The structural basis of the poor fibrin specificity of urokinase(I)--knowledge-based prediction of kringle structures of urokinase and its related proteins.

The Kringle-1 structure of plasminogen (PGK-1), the Kringle-2 structure of tissue plasminogen activator (PAK-2) and the Kringle structure of prourokinase (UKK) has been modeled on the basis of the three-dimensional structure of Kringle-1 of prothrombin (PTK-1) at 2.8 A resolution. The predicted three-dimensional structure of these Kringles shows that the binding site of PGK-1 is characterized by an apparent dipolar site, the polar parts of which are separated by a hydrophobic region. PAK-2 possesses the anionic center but has not a cationic binding center which might be provided by a guanidinium group from Arg-69 located adjacent to the Arg-71 position. UKK possesses neither the anionic binding center nor the cationic center which are probably the main reason for the poor fibrin specificity of urokinase.

Amino Acid Sequence↗
PubMed1990

Isolation, chemical and biological characterization of margaratensin, a neurotensin-related peptide from the skin of Rana margaratae.

A new neurotensin (NT)-related peptide, margaratensin, was obtained by Sep-Pak C18 and RP-HPLC from methanol extracts of the skin of Chinese frog Rana margaratae. The structure of the peptide has been determined to be Asp-Lys-Arg-Pro-Tyr-Ile-Leu-His-Glu, which is found to be homologous to the COOH-terminal sequence of NT, but has an extra His-Glu at the COOH-terminus. The synthetic preparation was shown to be indistinguishable from the native peptide during HPLC, amino acid analysis and bioassay. Margaratensin exhibited a hypotensive effect in the rat but the response was weaker than NT. The peptide could induce a potent and reproducible contractile activity on GPI which was different from xenopsin, another NT-related peptide from amphibian skin.

Amino Acid Sequence↗
PubMed1990

A case of heterotopic transplantation after bilateral traumatic above-knee amputations.

This paper describes a case in which a young woman's two lower limbs were crushed and amputated from the upper part of the thighs by a train. She was in serious hypovolemic shock at the time. With rapid infusion of intravenous fluids, she recovered from shock quickly, avoiding acute renal failure and ARDS. Heterotopic transplantation was performed. Two years later, the limb which had undergone heterotopic transplantation had partly restored function.

Adult↗
PubMed1990

Synthesis and biological activity of a new frog skin peptide, ranamargarin.

A new frog skin peptide, ranamargarin depicted as H-Asp-Asp-Ala-Ser-Asp-Arg-Ala-Lys-Lys-Phe-Tyr-Gly-Leu-Met-NH2' was synthesized by the conventional method. Comparisons of chemical and biological properties of both the synthetic and natural ranamargarins indicated that they were identical, so the chemical structure of ranamargarin was confirmed. Preliminary pharmacological study showed that ranamargarin was highly selective towards the SP-P subtype receptor.

Amino Acid Sequence↗