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Biomedical subjects

C He

Publications and source records attributed to C He.

172 records · Page 10Linked to original sources
PubMed1990

On the application of least-squares refinement to complex structures--resolving enantiomorphous phase ambiguity.

A least-squares refinement procedure has been proposed for resolving enantiomorphous ambiguity of noncentrosymmetric structures containing heavy atoms in a centrosymmetric arrangement. During the least-squares refinement of a pseudo-centrosymmetric image containing both enantiomorphs, the temperature factors of atoms in one enantiomorph shift in the same direction, while those of the other shift in the opposite direction. Accordingly the true structure can be distinguished easily from its enantiomorph. Tests on four unknown structures have shown that the method is very powerful.

Chemical Phenomena↗
PubMed1989

Microsomal metabolism of the Z and E isomers of N-nitroso-N-methyl-N-n-pentylamine.

N-Nitrosomethyl-N-n-pentylamine was separated into its E and Z isomers by HPLC. When the metabolism was examined using microsomes isolated from uninduced Fischer 344 rats, it was found that, at a constant final concentration of 0.5 mM, the yield of formaldehyde produced increased as the proportion of the Z isomer rose. The yield of valeraldehyde, on the other hand, decreased with an increasing proportion of the Z isomer. Kinetic constants were determined for the metabolism of the two isomers. During the metabolism of the Z isomer, the Vmax was 2.2-fold higher for the formation of formaldehyde than that for the E. The Vmax for valeraldehyde was 2.0-fold lower during the metabolism of the Z isomer. The results indicate that the relative position of the nitroso group can have a profound effect on the metabolism of each side of this type of molecule.

Aldehydes↗
PubMed1989

Carnivora: primary structure of the hemoglobin from the spotted hyena (Crocuta crocuta, Hyenidae).

The primary structure of the alpha- and beta-chains of hemoglobin from spotted hyena (Crocuta crocuta, Hyenidae) is presented. The structure-function relationship is discussed. The separation of the chains directly from hemoglobin was performed by RP-HPLC. After tryptic digestion of the chains, the peptides were isolated by RP-HPLC. Amino-acid sequences were determined by Edman degradation in liquid- and gas-phase sequencers. The alignment of the tryptic peptides was made by homology with human and other Carnivora hemoglobins. The hemoglobin from spotted hyena (Crocuta crocuta) exhibits in its alpha- and beta-chains 22 and 20 exchanges, respectively, compared to human hemoglobin. In the alpha-chains, two alpha 1 beta 1-contacts are exchanged. In the beta-chains five exchanges involve one alpha 1 beta 1-contact, one alpha 1 beta 2-contact, one heme contact, and two 2,3-DPG-binding sites.

Amino Acid Sequence↗
PubMed1986

A cycling assay for the determination of mono(adenosine-5'-diphosphoribose)-protein bound conjugate levels in mouse tissues.

Adenosine-5'-diphosphoribose (ADPR) is quantitatively split into 5'-AMP and ribose phosphate by treatment with alkali at elevated temperature. The 5'-AMP is used to generate NAD through a series of enzyme-catalyzed reactions. The NAD is then determined with a cycling assay modified after E.L. Jacobson and M.K. Jacobson [(1976) Arch. Biochem. Biophys. 175, 627-634]. The specificity of this assay has been verified. With this method the levels of mono(ADPR)-protein bound conjugate in various mouse tissues have been determined.

Adenosine Diphosphate Ribose↗
PubMedDate not supplied

Application of high resolution two-dimensional polyacrylamide gel electrophoresis of polypeptides from cultured neonatal rat cardiomyocytes: regulation of protein synthesis by catecholamines.

High resolution two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) was applied to cultured neonatal rat heart muscle cells, incubated for 72 h at 37 degrees C in serum-free medium, either in the absence or in the presence of 0.1 microM norepinephrine. After silver staining, about 340 and 550 protein spots could be seen in cardiomyocytes, cultured either in the absence or presence of norepinephrine. Of these spots, 141 could be further characterized according to isoelectric point and molecular weight, with 71 protein spots being present under both conditions. In cells cultivated in presence of norepinephrine, 58 new protein spots appeared, whereas 12 spots disappeared, and 22 spots increased (whereas 3 spots decreased) in intensity. In comparison with 2-D PAGE of rat cardiomyocytes, the protein pattern of the intact heart of neonatal rats is incongruent. 2-D PAGE of polypeptides of cultured neonatal rat cardiomyocytes may be a suitable tool to study the regulation of protein synthesis by various stimuli with relevance to cardiac growth adaptation, inotropy and heart failure.

Animals↗
PubMedDate not supplied

Regulation of protein biosynthesis in neonatal rat cardiomyocytes by adrenoceptor-stimulation: investigations with high resolution two-dimensional polyacrylamide gel electrophoresis.

The role of alpha- and beta-adrenoceptor-mediated regulation of protein patterns in cultured neonatal rat cardiomyocytes was studied with high resolution two-dimensional polyacrylamide gel electrophoresis. Spontaneously beating neonatal rat cardiomyocytes were cultured for 72 h at 37 degrees C in serum-free medium, supplemented with either the catecholamine norepinephrine (0.1 microM), or with norepinephrine (0.1 microM) plus the alpha 1-adrenoceptor blocker prazosin (1 microM), or with neither of these substances. In transmission light, 105 protein spots could be seen in the lysates from control cells, 244 spots were identified in lysates from norepinephrine-treated cells, and 114 protein species were counted in the case of lysates from cardiomyocytes which had been cultured in the presence of norepinephrine plus prazosin. This experimental approach allows a clear classification of alpha- and non-alpha (probably beta)-adrenoceptor-mediated catecholamine effects on protein synthesis in cardiomyocytes. In comparison with previous experiments (Chang et al., Electrophoresis, this issue, pp. 748-754), less protein species were identified in the untreated control cardiomyocytes, as well as in the norepinephrine treated cells. The only actual modification in the experimental setup in these two series was the addition of dimethyl sulfoxide--a substance known for its repressive effect on oncoprotein expression--to the culture medium, as solvent for prazosin.

Animals↗
PubMedDate not supplied

Cell adhesion molecule expression in the sheep thymus.

Cell adhesion molecules are potential regulating factors in both prethymic and intrathymic T cell development. An experimental challenge has been the development of a large animal model that facilitates in vivo studies of both intrathymic development and lymphocyte migration. To extend earlier studies of thymic development, we have developed a panel of monoclonal antibodies (mAb) to a variety of sheep cell adhesion molecules. Immunohistochemistry was used to define mAb reactivity and flow cytometry was used to quantify expression of cell adhesion molecules within the thymus. To facilitate flow cytometry definition of cortical thymocytes, mAbs were developed to the sheep CD1 antigen. Dual parameter flow cytometry provided a phenotypic characterization of cell adhesion molecule expression on both CD1(+) and CD1(-) sheep thymocyte populations. These studies demonstrated significantly enhanced cortical thymocyte expression of three cell adhesion molecules: beta1 integrin (CD29), ICAM-2 and LFA-3. The beta1 integrin cell adhesion molecule was also expressed at higher levels on CD1(+) thymocytes in post-natal lambs as compared to adult sheep. These studies of thymocyte membrane molecule expression should facilitate future investigations of sheep intrathymic development and T lymphocyte immigration.

Animals↗
PubMedDate not supplied

Hyaluronan, heterogeneity, and healing: the effects of ultrapure hyaluronan of defined molecular size on the repair of full-thickness pig skin wounds.

The extracellular matrix macromolecule, hyaluronan, is thought to modulate wound healing. However, the molecular size of hyaluronan and contaminating associated proteins may be important determinants of these effects. We have examined the results of seven daily topical treatments of full-thickness skin wounds in pigs with ultrapure hyaluronan of defined molecular size. High molecular weight hyaluronan (>1000 kd) enhanced, whereas low molecular weight hyaluronan decreased, the rate of early wound contraction as compared with intermediate hyaluronan (molecular weight = 100 kd) and saline solution controls. Fracture strength at 21 days was reduced by high and intermediate molecular weight hyaluronan but not by low molecular weight hyaluronan. Wound perfusion, measured by means of a scanning laser-Doppler technique as a noninvasive indicator of angiogenesis, showed depression by high and intermediate molecular weight hyaluronan on day 3, but all forms of hyaluronan caused elevated blood flow on day 7. The architecture of granulation tissue in this wet healing model was highly organized, but no gross histologic differences were seen because of treatment. Different molecular species of hyaluronan have differential effects on contraction, angiogenesis, and the evolution of wound strength. Where hyaluronan is used as a treatment or vehicle for wounds, its precise composition should be specified.

Journal Article↗
PubMedDate not supplied

Effects of chronic wound fluid on the bioactivity of platelet-derived growth factor in serum-free medium and its direct effect on fibroblast growth.

The fate of biologically active proteins applied to chronic wounds is almost totally unknown. Growth factors may be degraded by proteases, which are produced by both inflammatory and skin cells and by resident bacteria. However, there has been little work on the effect of chronic wound fluid on the activity of growth factors. A bioassay method has been chosen to examine the effect of incubation of platelet-derived growth factor with chronic wound fluid from leg ulcers on the in vitro growth of human dermal fibroblasts. Human dermal fibroblasts were cultured in serum-free medium, and a dose-response curve for proliferation in response to platelet-derived growth factor was obtained. Wound fluid was collected under occlusive dressings from five patients with chronic leg ulcers. Platelet-derived growth factor was incubated with chronic wound fluid at 37 degrees C for 4 hours, and the reactions arrested by snap freezing. The resultant solutions were tested for their ability to promote fibroblast proliferation. A colorimetric assay was used to monitor changes in the platelet-derived growth factor mitogenicity. The results showed that, in our standard culture conditions, chronic wound fluid always stimulated fibroblast proliferation, and, in most cases, incubation of platelet-derived growth factor with chronic wound fluid increased the stimulation compared with that produced by platelet-derived growth factor or chronic wound fluid alone.

Aged↗