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Biomedical subjects

M Lis

Publications and source records attributed to M Lis.

At least 73 records · Page 4Linked to original sources
PubMed1977

Morphine-like activity of sheep beta-lipotropin and of its tryptic fragments.

Sheep beta-lipotropin (beta-LPH) (sequence 1-91) was selectively cleaved with trypsin after blocking the epsilon-amino groups of lysine with citraconic anhydride. The resulting peptides were purified by a combination of cation-exchange chromatography and high-voltage electrophoresis. The purified fragments were then tested for their morphine-like activity in the mouse vas deferens bioassay. The active peptides were 61-91 and 61-80 were about as active as the synthetic methionine-enkephalin, and in turn these were about 100 times more active than beta-LPH itself. The inhibition of electrically stimulated mouse vas deferens by these peptides is reversed by naloxone, and suggests a competitive character of interaction. It is thus concluded that the active core for the morphine like activity in the mouse vas deferens bioassay is the fragment 61-65 of beta-LPH.

Amino Acid Sequence↗
PubMed1977

Primary structure and morphine-like activity of human beta-endorphin.

The complete amino acid sequence of human beta-endorphin was obtained by automatic sequencing of a sulfonyl isothiocyanate derivative of this peptide, in combination with peptide mapping of a tryptic digest of the native molecule. It was found to be identical with the carboxy-terminal portion 61-91 of human beta-lipotropin (beta-LPH). The morphine-like activity of beta-endorphin is comparable both in the mouse vas deferens bioassay and in the opiate receptor binding assay. However, beta-LPH is not active up to concentrations of 10(-6) M.

Amino Acid Sequence↗
PubMed1977

Effect of clofibrate treatment on chronic hyperlipidemia induced by an ACTH-producing tumor.

Plasma triglyceride and cholesterol levels were significantly increased in rats bearing an MtT-F4 tumor for 31-41 days. Addition of clofibrate at a dose of 30 mg kg-1 to the diet of rats bearing the tumor resulted in the complete elimination of the tumor effect on the plasma triglycerides, and to a great extent prevented the rise in the plasma cholesterol.

Adrenocorticotropic Hormone↗
PubMed1977

Dependence of tonin activity in rat submaxillary gland on growth hormone and testosterone.

Tonin, an enzyme present in rat submaxillary gland, converts angiotensin I to angiotensin II and is able to form angiotensin II directly from renin substrates. This enzyme was previously shown to be different from renin, tissue isorenins, and angiotensin I converting enzyme. The specific activity of tonin in rat submaxillary gland increases with the age of the animal and is much higher in male than in female rats; this sex difference is apparent from 60 to 70 days of age. There is a sharp drop of tonin activity in hypophysectomized animals, whereas adrenalectomy, thyroidectomy, and gonadectomy have have little effect. The marked increase in tonin activity was observed in animals bearing MtT-F4 transplantable tumors known to produce ACTH, prolactin, and growth hormone. Tonin specific activity in hypophysectomized male rats is restored to control levels by combined treatment with growth hormone and testosterone. Prolactin alone or in combination with testosterone, as well as transplanted pituitaries, has no effect in hypophysectomized animals. There is a significant specific binding of 125I-labeled growth hormone to isolated membranes of rat submaxillary gland.

Age Factors↗
PubMed1977

Immunohistochemical localization of beta-lipotropic hormone in the pituitary gland.

Identification of the beta-lipotropic hormone (beta-LPH)-producing cells in several species, including man, was performed with the technique involving use of the unlabeled antibody and peroxidase-antiperoxidase complex. Serial paraffin and ultrathin sections were treated for detection of both beta-LPH and ACTH at the light and electron microscopic levels. It was clearly shown that beta-LPH could be found only in the corticotropic cells located in the pars intermedia and pars distalis of all species studied. At the electron microscope level, it could be established that beta-LPH is contained in all the secretory granules of positive cells. These results suggest that beta-LPH is stored in the same secretory granules as ACTH and that both hormones are released together during granule extrusion.

Animals↗
PubMed1977

Effect of somatostatin on growth hormone release by MtT-F4 rat pituitary tumor in vitro.

Fluoride-stimulated adenylate cyclase is demonstrated inisolated tumor cells of transplantable rat pituitary tumor MtT-F4 in vitro. The intracellular cyclic adenosine 3':5'-monophosphate is lowered in the cells incubated in the presence of synthetic somatostatin. Contrary to the findings reported for normal pituitary, however, the immunoreactive growth hormone release does not change when either somatostatin or phosphodiesterase inhibitors are present in the incubation medium. The presence of dibutyryl cyclic adenosine 3':5'-monophosphate (5 mM) in the incubation medium does not change the rate of growth hormone release by isolated tumor cells.

Adenylyl Cyclases↗
PubMed1976

In vitro biosynthesis of gamma-lipotropic hormone.

Sheep gamma-lipotropic hormone (gamma-LPH) is a pituitary polypeptide made of 58 amino acids and is formed of the first 58 residues of beta-lipotropic hormone (beta-LPH). The C-terminal portion (41-58) of gamma-LPH is identical with the structure of beta-melanophore-stimulating hormone (beta-MSH). We hypothetized in 1967 that beta-LPH could be the biological precursor of beta-MSH and that gamma-LPH could be an intermediate compound. We demonstrated in 1974 that beta-LPH is actively synthesized in the bovine pituitaries. We now studied the biosynthesis of gamma-LPH by monitoring the incorporation of radioactive amino acids in beef pituitary slices. We separated gamma-LPH from the other radioactive proteins with a method previously described. We characterized the radioactive proteins by ion-exchange chromatography, gel filtration and polyacrylamide gel electrophoresis. Our results show that radioactive gamma-LPH was actively synthesized. This gamma-LPH has all the chemical characteristics of nonradioactive gamma-LPH. However, in the conditions used, we were unable to demonstrate biosynthesis of beta-MSH. These results suggest that gamma-LPH is biosynthesized more slowly than beta-LPH and that the conversion into beta-MSH, if it exists, is a slow or subactive process in the species studied.

Animals↗
PubMed1976

Isolation of a new lipolytic-melanotropic peptide from human pituitary glands.

A new peptide having both lipolytic and melanotropic properties has been isolated from human pituitary glands. It has a molecular weight around 11,000, an amino acid composition different from the known lipolytic-melanotropic hormones, and an isoelectric point of 8.5. Although it is not entirely pure, there is no doubt that it differs from other known lipolytic-melanotropic substances in its total lack of methionine and tryptophan and its unusually high content of lysine and histidine. It has a melanocyte-stimulating hormone activity of 19 units/mug. As a lipolytic agent it is active with rabbit adipocytes, only slightly active with human cells and inactive with adipocytes from the rat.

Alanine↗
PubMed1975

Changes of endocrine properties of a transplantable, multihormonal, pituitary tumor (MtT-F4) after hypophysectomy of host rats.

The transplantable rat pituitary tumor MtT-F4 failed to grow in rats hypophysectomized at the time of transplantation, but did grow in thyroxine-treated hypophysectomized rats. In the latter rats, the tumor did not stimulate the adrenals to the same extent as in control rats. When the tumor did not stimulate the adrenals to the same extent as in control rats. When the tumor cells were isolated and incubated in vitro, those from hypophysectomized thyroxine-treated rats released much less ACTH into the incubation medium than the tumor cells from control rats. They also released significantly less growth hormone than tumor cells from intact, intact thyroxine-treated, and thyroidectomized thyroxine-treated rats. Prolactin release by the isolated tumor cells in vitro was the same in all groups studied. The results suggest that the hypophysectomy and thyroxine treatment of the host rat might selectively influence the production of hormones by the MtT-F4 transplantable rat pituitary tumor.

Adrenal Glands↗
PubMed1975

Multipotent lipotropic hormones. In search of a pituitary cell producing multipotent LPH.

The affinity for antiserum to the multipotent lipotropic hormone (beta-LPH) was tested by immunohistochemical staining of all known cell types in normal and certain abnormal mouse, rat, and human pituitaries. Results indicate that beta-LPH has ACTH, MSH, LH and StH(GH) immunologically cross-reacting determinants. Affinities of anti-LPH for TtH and MtH (prolactin) were not detected in normal pituitaries, but thyrotropic tumor cells reacted with anti-LPH. Absorption experiments confirm that the single polypeptide hormone of the pituitary, beta-LPH, is coded for ACTH and MSH activities. The multi-functional hormone, LPH probably is secreted by the adrenotropes. In addition to ACTH and MSH, it probably contains other antigenic and biologic determinants. Some of these may accentuate its lipotropic activities; others may be incidental. These are points calling for further correlated structural, biologic, and immunologic investigations.

Adrenocorticotropic Hormone↗