Search PubMed⌕ Search

Biomedical subjects

Q Zhu

Publications and source records attributed to Q Zhu.

At least 307 records · Page 17Linked to original sources
PubMed1989

[Quantification of pulmonary to systemic flow ratio (Qp/Qs) in children with patent ductus arteriosus by echocardiography].

The assessment of left-right ductal shunting flow in 35 children with PDA by 2-DCE with 35 normal children as a control was shown in the study. A close relationship was demonstrated between the grade of the diastolic negative contrast at the distal ends of the pulmonary artery and Q p/Qs. The diastolic negative contrast effect of 2-DCE could be used as a new important index in the assessment of left-to-right ductal shunting flow. Four parameters which were closely correlated with Qp/Qs were selected from 8 parameters by the stepwise multilinear regression procedure. The 4 parameters were grade II DNCE, LVPWER, grade I DNCE, LADR. A regression equation which was capable of assessing Q p/Qs noninvasively in children with PDA was derived from the 4 parameters. The accuracy of calculation of Qp/Qs by the regression equation was 80%.

Adolescent↗
PubMed1989

[Luteinized unruptured follicle syndrome].

In a group of 109 infertile women, 180 cycles were monitored with B type ultrasound, BBT and cervical scoring. The incidence of LUF in stimulated cycles was 31.8%, significantly higher than that in spontaneous cycles (10.1%). During the follicular phase, no difference was found between the LUFS and normal ovulatory cycles as to follicular growth curve, maximal diameter of dominant follicle and the cervical scores. Therefore prediction of the LUFS is difficult. 63.6% of the LUF patients had recurrences, and high incidence of abnormality (70.6%) in their non-LUF cycles. 7 of the 14 patients with LUFS were originally diagnosed as unexplained infertility. It suggests that LUFS is of particular importance in the group of women with unexplained infertility.

Adult↗
PubMed1988

Chemical crosslinking of glycoproteins on the envelope of herpes simplex virus.

A base-reversible, 13-A homo-bifunctional chemical crosslinking reagent, bis[2-(succinimidooxycarbonyloxy)ethyl]sulfone (BSOCOES), was tested for its ability to crosslink the herpes simplex virus type 1 glycoproteins associated with the envelope of purified virions. The crosslinked proteins were fractionated and analyzed by immunoblotting, immunoprecipitation, and two-dimensional polyacrylamide gel electrophoresis using monospecific antisera to detect the glycoproteins, gB and gC. Each of the glycoproteins exhibited distinct patterns of crosslinking. Monomers of gB were crosslinked and appeared as a high-molecular-weight complex. No apparent intermediates were observed between the gB monomer and the high-molecular-weight complex. Analysis of the components in the gB high-molecular-weight complex suggests that gB represents the major component and exists as a high-molecular-weight oligomer on viral envelopes under native conditions. In contrast, gC was cross-linked at a much lower efficiency and a number of components at intermediate molecular weights were detected. Initial studies on crosslinked products that were detectable with anti-gC antibody suggest that one of these products represents a gC dimer.

Blotting, Western↗
PubMedDate not supplied

Conformational analysis of the dipeptide taste ligand L-aspartyl-D-2-aminobutyric acid-(S)-alpha-ethylbenzylamide and its analogues by NMR spectroscopy, computer simulations and X-ray diffraction studies.

A dipeptide taste ligand L-aspartyl-D-2-aminobutyric acid-(S)-alpha-ethylbenzylamide was found to be about 2000 times more potent than sucrose. To investigate the molecular basis of its potent sweet taste, we carried out conformational analysis of this molecular and several related analogues by NMR spectroscopy, computer simulations and X-ray crystallographic studies. The results of the studies support our earlier model that an L-shape molecular array is essential for eliciting sweet taste. In addition, we have identified an aromatic group located between the stem and the base of the L-shape, which is responsible for enhancement of sweetness potency. In this study, we also assessed the optimal size of the essential hydrophobic group (X) and the effects of the chirality of the second residue toward taste.

Aminobutyrates↗
PubMedDate not supplied

Highly potent side chain-main chain cyclized dermorphin-deltorphin analogues: an integrated approach including synthesis, bioassays, NMR spectroscopy and molecular modelling.

Our continuing efforts to study structure-activity relationships of peptide opioids have resulted in the synthesis of a series of cyclic opioids related to dermorphins and deltorphins. The biological activities of the compounds have been determined and the conformational analyses carried out using 1H-NMR spectroscopy and molecular modelling. The three compounds in the series Tyr-c[D-Orn-Phe-Ala], Tyr-c[D-Lys-Phe-Ala], and Tyr-c[A2bu-Phe-Ala-Leu] are cyclized via a lactam bridge from the side-chain of the residue at the second position with the carboxyl terminus of each compound. The molecules incorporate 12-, 13- and 14-membered rings, respectively. They include a phenylalanine at the third position which is a distinguishing characteristic of dermorphins and deltorphins. The guinea pig ileum and mouse vas deferens assays show that the compounds are highly active at both mu- and delta-opioid receptors. The compounds are all highly effective antinociceptive agents as measured by the intrathecal rat hot plate test. Conformational analyses of the molecules indicate that they can adopt topochemical arrays required for bioactivity at both mu- and delta-receptors which explains their high activity in both guinea pig ileum and mouse vas deferens in vitro assays. The results support our models for mu- and delta-receptor activity for constrained peptide opioids.

Amino Acid Sequence↗
PubMedDate not supplied

Sweet and bitter taste: structure and conformations of two aspartame dipeptide analogues.

The synthesis and X-ray diffraction analysis of two dipeptide taste ligands have been carried out as part of our study of the molecular basis of taste. The compounds L-aspartyl-D-alpha-methylphenylalanine methyl ester [L-Asp-D-(alpha Me)Phe-OMe] and L-aspartyl-D-alanyl-2,2,5, 5-tetramethylcyclopentanyl ester [L-Asp-D-Ala-OTMCP] elicit bitter and sweet taste, respectively. The C-terminal residues of the two analogues adopt distinctly different conformations in the solid state. The aspartyl moiety assumes the same conformation found in other dipeptide taste ligands with the side-chain carboxylate and the amino groups forming a zwitterionic ring with a conformation defined by psi, chi 1 = 157.7 degrees, -61.5 degrees for L-Asp-D-Ala-OTMCP and 151.0 degrees, -68.8 degrees for L-Asp-D-(alpha Me)Phe-OMe. In the second residue, a left-handed helical conformation is observed for the (alpha Me)Phe residue of L-Asp-D-(alpha Me)Phe-OMe with phi 2 = 49.0 degrees and psi 2 = 47.9 degrees, while the Ala residue of L-Asp-D-Ala-OTMCP adopts a semi-extended conformation characterized by dihedral angles phi 2 = 62.8 degrees and psi 2 = -139.9 degrees. The solid-state structure of the bitter L-Asp-D-(alpha Me)Phe-OMe is extended: while the crystal structure of the sweet L-Asp-D-OTMCP roughly adopts the typical L-shaped structure shown by other sweeteners. The data of L-Asp-D-(alpha Me)Phe-OMe are compared with those of its diastereoisomer L-Asp-L-(alpha Me)Phe-OMe. Conformational analysis of the two taste ligands in solution by NMR and computer simulations agrees well with our model for sweet and bitter tastes.

Aspartame↗
PubMedDate not supplied

Isonucleosides incorporating universal bases.

Enantiomeric isodideoxynucleosides of the (S,S) and (R,R) families with the universal base, imidazole-4-carboxamide as the nucleobase, were synthesized as biological mimics of anti-HIV active D- and L-related isodideo-xyadenosines. In vitro anti-HIV evaluation in CEM cells of these target compounds showed that they were inactive. Further antiviral studies are in progress.

Aminoimidazole Carboxamide↗
PubMedDate not supplied

Synthesis, crystal structure and conformation in solution of four stereoisomeric cyclo-lanthionine derivatives.

The synthesis of the four stereoisomeric cyclo-lanthionine derivatives: [formula: see text] (where AlaL denotes one end of the lanthionine unit) was carried out on a Kaiser-oxime resin starting from orthogonally protected lanthionine units. The peptide ring was prepared in 79-85% yield via amide bond formation by utilizing the method of peptide cyclization on an oxime resin (PCOR). The crystal and molecular structures of the protected cyclic dipeptides have been determined by X-ray diffraction techniques. The two cyclic lanthionine derivatives with chiralities of [R,S] and [S,R] crystallized in the orthorhombic space group P2(1)2(1)2(1) and the [R,R]- and [S,S]-cyclo-lanthionine derivatives in the monoclinic space group C2. The structures were solved by direct methods and refined to an R factor of 0.0368-0.0573. The ring amide bonds in all four compounds are cis, while the urethane group is trans and extended. The NMR spectra of the four stereoisomers in DMSO-d6 were used to determine their conformation in solution. The analysis of the NMR data with constrained distance geometry search showed the same conformational features in solution as in the crystalline state.

Alanine↗
PubMedDate not supplied

Estimation of tendon moment arms from three-dimensional magnetic resonance images.

New three-dimensional (3D) magnetic resonance imaging (MRI) methods for measuring the tendon moment arm were created and were evaluated on the tendon moment arm of the flexor digitorum profundus at the third metacarpophalangeal joint. Using an open magnet MRI system and a hand holder, a series of static images were acquired at four joint angles and analyzed using specially created computer programs. Three methods were evaluated: (1) a 3D tendon excursion method that extended the method of Landsmeer; (2) a 3D geometric method whereby the moment arm was the perpendicular distance between the joint axis of rotation and the tendon path, and (3) a two-dimensional (2D) geometric method whereby single image slices were analyzed. Repeating the imaging and measurement processes, the 3D tendon excursion method was more reproducible (6% variation) than the 3D geometric method (12%), and both were much more reproducible than the 2D geometric method (27%). By having three operators analyze a single set of image data, we found that the precision of the 3D tendon excursion method was much less affected by segmentation error than the 3D geometric method. With the 3D imaging methods, tendon bowstringing and a displacement of the joint center of rotation toward the dorsal side of the hand were evident, leading to as much as a 60% increase in moment arm with joint flexion. Because of the dependence on flexion and variation between subjects, we recommend patient-specific measurements for target applications in functional neuromuscular stimulation interventions and tendon transfer surgery.

Analysis of Variance↗
PubMedDate not supplied

Stereological evaluation of mouse prostate development.

A stereological study of the development of the mouse prostate was undertaken between the second week of postnatal life and maturity. The aim was to quantify the progressive changes in the size and areal density of the ventral prostate gland components during development. Male mice were studied at weekly intervals from days of life 15 to 49 for organ and body weights, ductal branching, diameters of ventral prostate ducts and lumen and volume densities of epithelium, lumen, and stroma. Ductal branch-tip numbers were maximal at 35 days of age, while prostate weights increased linearly with age and did not reach a plateau at 49 days. Prostatic glandular and luminal diameters both showed a continuous increase until day 49. At 5 weeks of age, there was a decrease in the volume density of prostatic epithelium accompanied by a simultaneous increase in the volume density of the lumen. This study indicates that prostate-branching morphogenesis is complete by the fifth week in mice but that further growth of the prostate continues due to the increase in ductal dimensions. Qualitatively, the ventral prostate in mice is fully mature by 5 weeks, and this histological maturity coincides with the completion of branching morphogenesis.

Animals↗