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Biomedical subjects

D Chang

Publications and source records attributed to D Chang.

At least 289 records · Page 16Linked to original sources
PubMed1980

Interaction of somatomedin-C with an antibody directed against the synthetic C-peptide region of insulin-like growth factor-I.

Insulin-like growth factor-I is a human plasma peptide with strong structural homology to human prosinsulin. This peptide has been classified as a somatomedin on the basis of its biological actions and growth hormone dependence. We have generated an antibody to the synthetic 12 amino acid C-peptide region of insulin-like growth factor-I and used it to compare three somatomedin preparations to insulin-like growth factor-I. We also compared these somatomedin preparations to insulin-like growth factor-I using the standard SM-C RIA. We conclude that insulin-like growth factor-I and somatomedin-C behave identically in these two RIA's and are very similar if not identical molecules.

Amino Acid Sequence↗
PubMed1979

Biochemical parameters of normal rabbit serum.

An attempt was made to establish the normal range of 27 different parameters in the serum of 45 healthy, purebred, New Zealand White rabbits (3-5 kg). The reproducibility of the results was acceptable. Sensitive isoenzyme patterns (LDH, CK) could change, however, significantly if different methods were used in the bleeding procedure. Isoenzyme patterns (LDH and CK) of rabbit sera were different from that of human sera. All obtained results were compared with earlier data sporadically published in literature on rabbits.

Animals↗
PubMed1979

Regulation of the interaction of purified human erythrocyte AMP deaminase and the human erythrocyte membrane.

The binding of purified human erythrocyte AMP deaminase to human erythrocyte membranes and the effect of binding on enzyme catalytic activity was investigated. AMP deaminase binds preferentially and specifically to the cytoplasmic surface of the erythrocyte membrane. The binding is saturable, reversible, and responsive to alterations of pH, of ionic strength, and of ATP and AMP concentrations. A limited number (approximately equal to 2.2 X 10(4) per erythrocyte) of apparently homogeneous high affinity (Ka approximately equal to 2.6 X 10(7) M-1) binding sites is present. The stability of purified and endogenously bound AMP deaminase is markedly improved by the interaction with the membrane, whereas the catalytic activity of AMP deaminase is sharply reduced. AMP deaminase displaces membrane bound glyceraldehyde 3-phosphate dehydrogenase in roughly a dose-response manner. No evidence for binding of AMP deaminase to spectrin or band 3 (the G3PD binding protein) was found in sucrose gradients, however. The interaction of AMP deaminase with the erythrocyte membrane may play an important role in the regulation of cellular adenine nucleotide metabolism.

AMP Deaminase↗
PubMed1978

Indirect vascular actions of (Gln4)-neurotensin in canine adipose tissue.

The vasoconstrictor action of the tridecapeptide (Gln4)-neurotensin has been studied in subcutaneous adipose tissue in the inquinal region of anesthetized dogs. Close intra-arterial infusion of (Gln4)-neurotensin, 30--120 pmol X kg-1 b.wt. X min-1, elicited similar vasoconstrictions in the adipose tissue on the infusion side and on the contralateral side. This suggests that (Gln4)-neurotensin must enter the general circulation before it can elicit vasoconstriction. Removal of parts of the gastrointestinal tract did not change the vasoconstrictor response. Thus, there is no indication of release of vasoactive substances from the gastrointestinal tract by (Gln4)-neurotensin. Infusion into the portal vein elicited the same vasoconstriction in adipose tissue as the same dose administered i.v. It is suggested that the vasoconstrictor action in adipose tissue is not caused by (Gln4)-neurotensin per se. Instead, vasoactive substance(s) may be formed from (Gln4)-neurotensin.

Adipose Tissue↗
PubMed1977

Sample derivatization and structure analysis by field desorption mass spectrometry. Peptide methylation-methanolysis.

Analysis by field desorption mass spectrometry of reaction product mixtures produced by treatment of peptides with methanol and hydrogen chloride augments significantly structural data derived by direct field desorption mass spectrometry analysis of the peptides. Analyses of data obtained by three peptides, beta-Ala-HisOH, p-Glu-Ser-GlyOH and Glu-Ser-Gly-AspOH are used for illustration. Data from field desorption mass spectrometry of peptide methylation-methanolysis product mixtures are used to (a) distinguish [M]+- from [M + H]+ in peptide field desorption mass spectrometry spectra, (b) ascertain the number of carboxyl groups present in a peptide, (c) identify a pyro-glutamyl N-terminus and (d) derive peptide sequence information. Definitive assignments of ion relationships are facilitated by use of methanol and deuteromethanol in paired experiments.

Mass Spectrometry↗
PubMed1977

Thymosin alpha1: isolation and sequence analysis of an immunologically active thymic polypeptide.

The amino acid sequence of a biologically active polypeptide isolated from calf thymus, termed thymosin alpha1, has been determined. Thymosin alpha1 is a heat stable, highly acidic molecule composed of 28 amino acid residues. This peptide is one of several present in thymosin fraction 5 that may participate in the regulation, differentiation and function of thymus-dependent lymphocytes (T cells). A nomenclature for the family of polypeptides present in thymosin fraction 5 is suggested.

Amino Acid Sequence↗
PubMed1977

Actions of neurotensin and (Gln4)-neurotensin on isolated tissues.

The actions of neurotensin and (Gln4)-neurotensin have been investigated on a number of isolated tissues. They were ineffective in contracting the guinea pig vas deferens, the rabbit aortic strip or the frog rectus abdominis muscle in concentrations up to 0.24 micron. Neurotensin and (Gln4)-neurotensin relaxed the rat duodenum at fairly high concentrations (24 nM). The guinea pig ileum contracted in response to increasing doses, although the maximum response were only one half that caused by histamine. Tachyphylaxis was observed at dose intervals of less than 12 minutes, but this tachyphylaxis did not inhibit responses to acetylcholine, histamine, 5-HT or to DMPP, suggesting that the neurotensins may act at specific receptor sites. They contracted the rat fundus strip at concentrations of 0.24 nM and higher. The neurotensins and 5-HT were approximately equipotent on this tissue, although the maximum responses was about 80% of that to 5-HT. The contractions of the rat fundus strip could not be blocked by atropine, hexamethonium, methysergide, morphine or by 7-OH-THC. These data indicate that neurotensin and (Gln4)-neurotensin are equipotent as far as smooth muscle stimulating activity is concerned. Of those organs tested, the rat fundus strip seems to be the most suitable one for studies concerning structure-activity relationships.

Acetylcholine↗
PubMed1977

Inhibition of gastric and intestinal motor activity in dogs by (Gln4) neurotensin.

The action of (Gln4)-neurotensin was studied on the spontaneous motor activity in isolated canine fundic, antral and intestinal pouches. All pouches had been prepared more than 6 months prior to the experiments. Spontaneous motor activity was recorded for at least 1 h before the Gln4)-neurotensin was infused i.v. for 30 min in doses ranging between 6.3 and 100 ng X kg-1 X min-1. In the vagally denervated fundic pouches (Gln4)-neurotensin inhibted motor activity in doses above 25 ng X kg-1 X min-1. The vagally innervated antral pouches were more sentitive than the vagally denervated fundic pouches to the action of (Gln4)-neurotensin. Thus motor inhibition was induced by doses as low as 6.3 ng X kg-1 X min-1. The effect of (Gln4)-neurotensin on motor activity in intestinal pouches was inconsistent. Inhibition was seen in 1 out of 7 expts. The present results show that the gastric motor activity is the most sensitive function to (Gln4)-neurotensin so far studied.

Animals↗