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Biomedical subjects

C H Li

Publications and source records attributed to C H Li.

At least 343 records · Page 19Linked to original sources
PubMed1978

Dissociation kinetics of tetra-S-carbamidomethylated plasmin-modified human somatotropin.

The dissociation of tetra-S-carbamidomethylated, plasmin-modified human somatotropin at 25 +/- 2 degrees C has been found to be a slow, exergonic equilibrium reaction; an equilibrium constant of 1.77 mol/L and a standard free energy of dissociation of -340 cal/mol have been calculated. The major products of the dissociation have been shown to consist of a monomeric form of the 51-residue carboxyl-terminal fragment and a trimeric form of the 134-residue amino-terminal fragment. The carboxyl-terminal fragment appears to be a random coil, while the amino-terminal fragment retains a considerable degree of secondary and tertiary structures.

Amino Acid Sequence↗
PubMed1978

Beta-endorphin is behaviorally active in rats after chronic intravenous administration.

Male Sprague-Dawley rats received 14 daily intravenous injections of saline or human beta-endorphin (2.5 mg/kg). Animals were given one-way active avoidance training on the eleventh day, and analgesia testing on the twelfth (tail-flick) and thirteenth (hot-plate) days. Beta-endorphin had no effect on the number of trials needed to reach the avoidance criterion, but significantly lengthened response latencies. Beta-endorphin had no analgesic effect in either test procedure.

Animals↗
PubMed1978

Passive immunization with an antibody to the beta-subunit of ovine luteinizing hormone as a method of early abortion--a feasibility study in monkeys (Macaca radiata).

Antiserum to the beta-subunit of ovine luteinizing hormone (oLH-beta) raised in monkeys (Macaca radiata) has been tested by a variety of criteria both in vivo and in vitro to establish its ability to neutralize oLH, hLH, and human chorionic gonadotropin (hCG). Passive administration of this antiserum caused inhibition of ovulation and termination of pregnancy in recipient monkeys as indicated by premature vaginal bleeding and a significant reduction in serum progesterone and estrogen levels. The results suggest that antiserum raised in monkeys against oLH-beta can neutralize monkey LH as well as monkey CG.

Abortion, Induced↗
PubMed1978

Appearance of beta-endorphin-like immunoreactivity in human ventricular cerebrospinal fluid upon analgesic electrical stimulation.

beta-Endorphin-like immunoreactivity in human ventricular cerebrospinal fluid was measured with a specific radioimmunoassay. The subjects were undergoing a surgical procedure for relief of chronic intractable pain. This procedure involved the focal stimulation of a medial thalamic site adjacent to the wall of the third ventricle. Samples were collected before and during the analgesic stimulation. No beta-endorphin-like immunoreactivity could be detected prior to stimulation, suggesting that baseline levels are below 25 fmol/ml of cerebrospinal fluid. Electrical stimulation led to substantial increases (13- to 20-fold) in immunoreactive material in every subject. These results suggest that beta-endorphin-like material can be released into the ventricular system and may contribute to the pain blockade that results from periventricular stimulation.

Analgesia↗
PubMed1978

Immunoreactivity and receptor binding of mixed recombinants of human growth hormone and chorionic somatomammotropin.

The behavior in six radioligand assays of the recombinant obtained by the noncovalent complementation of the reduced and carbamoylmethylated 134-residue amino-terminal fragment of human growth hormore with the reduced and carbamoylmethylated 51-residue carboxyl-terminal fragment of human chorionic somatomammotropin was compared to that of the analogous recombinant of the 133-residue amino-terminal fragment of human chorionic somatomammotropin and the 51-residue carboxyl-terminal fragment of human growth hormone. The determinants for the hepatic growth hormone receptor binding and for the lactogenic receptor binding of human growth hormone are on the amino-terminal fragments. The antigenic determinants for both a monospecific antiserum to human growth hormone and a monospecific antiserum to human chorionic somatomammotropin also are on the amino-terminal fragments of their respective antigens. The mixed recombinant of the amino-terminal fragment of human growth hormone with the carboxyl-terminal fragment of human chorionic somatomammotropin retains full radioimmuno- and radioreceptor activity after lyophilization.

Epitopes↗
PubMed1978

Noncovalent interaction of the NH2-terminal fragment of human somatotropin with the COOH-terminal fragment of human choriomammotropin to generate growth-promoting activity.

Complementation of the plasmin fragments of reduced-carbamoylmethylated (Cam) human somatotropin (hGH) with those of reduced-carbamoylmethylated human chorionic somatomammotropin (hCS) have been investigated. It was found that the recombinant obtained by noncovalent interaction of [Cys(Cam)53]hGH-(1-134) with [Cys(Cam)-165,182,189]hCS-(141-191) exhibits 50% growth-promoting activity and nearly full immunoreactivity. Complementation of [Cys(Cam)53]hCS-(1-133) with the COOH-terminal fragment of hGH generated lower growth-promoting and immunological activities.

Amino Acid Sequence↗
PubMed1978

Two fragments from fibrinolysin digests of ovine prolactin: characterization and recombination to generate full immunoreactivity.

The action of fibrinolysin (plasmin; EC 3.4.21.7) on ovine prolactin has been investigated. It was found that the enzyme selectively cleaves the bond between Met-53 and Ala-54. The two fragments, PRL-(1-53) and PRL-(54-199), have been purified and characterized. A recombinant molecule has been obtained by noncovalent interaction of PRL-(1-53) and PRL-(54-199). The recombined protein behaves nearly identically to the parent hormone in circular dichroism spectra and exclusion chromatography. The recombinant possesses full immunoreactivity, as revealed by gel double-diffusion and complement fixation. However, the recombined protein exhibits low prolactin activity in the pigeon crop-sac test.

Amino Acids↗
PubMed1978

Endorphins may function in heat adaptation.

Administration of the opiate antagonist naloxone to rats after acute or chronic heat exposure precipitates an increase in colonic temperature, an increase in escape attempts, and a decrease in body weight. These changes are accompanied by signs associated with hyperthermia such as salivation, diarrhea, and an abnormal extended posture. Although brain endorphin involvement is possible, hypophysectomy diminishes the intensity and magnitude of these naloxone effects, indicating that the naloxone effect in intact animals may be due to a functional antagonism of pituitary endorphins. These observations suggest that endorphins attenuate physiological responses to thermal and noxious stimuli triggered in common neuroanatomical pathways by heat.

Adaptation, Physiological↗
PubMed1978

Growth hormone modulation of murine erythroleukemia cell growth in vitro.

There are few studies showing a biological effect of growth hormone (somatotropin) on cell proliferation in vitro at physiological concentrations. We report here that Friend virus-infected erythroleukemia cells are responsive to growth hormone in vitro. Using a serum-free clonogenic assay we found as little as 0.1 ng of human growth hormone per ml caused a prominent stimulation of cell proliferation. Peak activity of human growth hormone occurred at 200 ng/ml, resulting in a 2-fold increase in cloning. Human chorionic somatomammotropin and the Cys(Cam)53-hGH(1-134) fragment of human growth hormone were also active, but a biologically inert oxidized human growth hormone had no growth-promoting effect in vitro. Cell proliferation was stimulated by insulin with peak potentiation occurring at 1 ng/ml, and prolactin had a demonstrable stimulatory effect between 50 and 100 ng/ml. These observations indicate that growth hormone and related polypeptides have a direct effect on the in vitro proliferation of erythroleukemia cells in the absence of serum. The results confirm a direct action of growth hormone on mammalian cells and suggest that pituitary hormones may affect leukemic cell growth.

Animals↗
PubMed1978

Isolation, characterization, and synthesis of a corticotropin-inhibiting peptide from human pituitary glands.

A corticotropin-inhibiting peptide (CIP) has been isolated from human pituitary extracts. It consists of 32 amino acids with a proposed sequence identical to residues 7--38 of corticotropin (ACTH). The peptide has been synthesized by the solid-phase method. The melanotropic activity of the peptide is estimated to be 30% of the potency of ACTH. It is devoid of corticosteroidogenic activity but is able to inhibit ACTH-stimulated corticosterone production in isolated rat adrenal cells.

Adrenocorticotropic Hormone↗