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J L Luborsky-Moore

Publications and source records attributed to J L Luborsky-Moore.

10 recordsLinked to original sources
PubMed1979

Specific binding of prostaglandin F2 alpha to membranes of rat corpora lutea.

Prostaglandin F2 alpha (PGF2 alpha) binds specifically to a partially purified membrane preparation from rat corpora lutea. The high affinity, low capacity binding component asa a Kd = 4.7 nM and has a capacity of 0.38 pmol/mg protein. Binding kinetics were temperature-dependent with an association rate constant of 2.5 x 10(5) 1/mol-sec and a dissociation rate constant of 4.3 x 10(-4) sec-1 at 22 degrees C. Little competition for binding was shown by other prostaglandins and prostaglandin metabolites; the PGF2 alpha analogue ICI 81008 (16-m-trifluoromethylphenyl-prostaglandin F2 alpha) showed a binding affinity similar to that of PGF2 alpha. The specific binding of PGF2 alpha to luteal cell membranes was confirmed by electron microscopy using a ferritin--PGF2 alpha conjugate. Ferritin--PGF2 alpha was found predominantly on luteal cell surfaces; little binding occurred on other types of cells present. These data demonstrate specific binding of PGF2 alha to rat luteal membranes. It is suggested that the luteolytic action of PGF2 alpha in the rat may be receptor-mediated.

Animals↗
PubMed1979

Action of gonadotropin-releasing hormone and its superactive analogues on the anterior pituitary: the mechanism of release and synthesis of gonadotropins.

The role of prostaglandins (PG), their active intermediates or the adenylcyclase-cyclic AMP system for gonadotropin release and/or synthesis was evaluated by administering gonadotropin-releasing hormone (Gn-RH) and its superactive analog to normal and aspirin-treated rats. Serum LH levels, anterior pituitary malondialdehyde (MDA) content and cyclic AMP (cAMP) levels were followed. The pituitaries stimulated with Gn-RH or its superactive analog yielded more MDA and cAMP than the controls. Stimulation of the pituitary with the releasing hormones, after aspirin treatment, yielded 40--70% less MDA and lower LH values than the nontreated animals. The cAMP levels were not significantly lowered by the aspirin treatment. These studies suggest that the activation of the PG biosynthesis and the adenyl-cyclase-cyclic AMP system are not sequential but 2 separate physiological events. The active PG intermediates may only be responsible for the release of LH. It is not clear whether the activation of cAMP initiates also the processes preparatory to the synthesis of LH in the endoplasmic reticulum. In vivo studies in rats showed that the analogs (I and II) were 30 times more potent and had a more prolonged action on the pituitary (3 h) than Gn-RH. Ultrastructural studies on the anterior pituitary after hypophyseal stalk portal vessel infusion of Gn-RH and the analog (I and II) provided ample morphological evidence for both Gn-RH and analog induced gonadotropin-release and synthesis. The prolonged action of the superactive analog (I and II) on the gonadotrophs was also indicated by ultrastructural studies.

Animals↗
PubMed1979

Mechanisms of PGF2 alpha action in functional luteolysis.

The luteolytic action of PGF2 alpha appears to be due to loss of gonadotropin support of corpus luteum function. This "chemical hypophysectomy" produced by PGF2 alpha in the rat has several components: 1. A rapid block of gonadotropin uptake in vivo by an unexplained mechanism. 2. A rapid and direct block of adenylate cyclase activation by the LH receptor complex in isolated luteal cells. 3. An eventual loss of LH receptor binding activity produced by inhibition of prolactin action.

20-alpha-Dihydroprogesterone↗
PubMed1978

Stimulation of gonadotrophs by pituitary portal vessel infusion of superactive LH-RH analogues: an ultrastructural study.

LH-RH or its superactive analogues were infused into pituitary portal vessels of adult male rats for 1 min; pituitaries were then fixed for routine electron microscopy 1 min, 30 min and 3 h after infusion. A maximal increase of granule release at 2 min. and a maximal increase in synthetic activity (i.e., dilated cisternae of rough endoplasmic reticulum (RER) and Golgi apparatus (GA)) at 30 min, occurred in gonadotrophs in response to both LH-RH and the superactive analogues, but not to saline infusion. Only gonadotrophs from analogue infused pituitaries showed a high level of exocytosis and protein synthesis at 3 h. In addition, the superactive analogues typically stimulated formation of large vacuoles of RER at 30 min and 3 h that resembled those seen in "signet ring" cells following castration. Radioimmunoassay (RIA) values of serum LH supported these observations. The results of this study provide morphological evidence for a prolonged action of the superactive analogues of LH-RH on both gonadotropin secretion and synthesis under physiological conditions.

Animals↗
PubMed1976

Localization of catecholamines in the eyes and other tissues of Aplysia.

A green fluorescence indicative of catecholamines (CA) was localized in the secondary cells (nonreceptor neurons), neuropile and optic nerve of the eye and other tissues in Aplysia by using the formaldehyde-induced fluorescence method for the demonstration of biogenic amines. The specificity of the induced fluorescence was confirmed by its absence in tissue not exposed to formaldehyde vapor, relatively rapid decay upon exposure to UV light and its chemical reduction by sodium borohydride. The fluorescence was greatly reduced in eyes treated with reserpine (depletes serotonin and catecholamines). Furhter confirmation that the green fluorescence in the eye was due to a CA and not to serotonin was obtained by showing that it was decreased or eliminated by alpha-methyl-para-tyrosine (an inhibitor of catecholamine synthesis), increased by incubation in dopamine and exhibited a peak emission (470 nm) characteristic of CA fluroescence. CA fluorescence was also observed in the neuropiles of the cerebral, pedal, pleural and parieto-visceral ganglia and in cells in the pedal ganglion, statocyst, mantle, anterior tentacles and siphon. The finding of CA in secondary neurons of the eye was unusual since CA-containing cells have not been observed in other gastropod eyes. The distribution of CA in Aplysia, in tissue other than the eye, is similar to that of other gastropod molluscs.

Animals↗
PubMed1975

Ultrastructural observation of anterior pituitary gonadotrophs following hypophysial portal vessel infusion of luteinizing hormone-releasing hormone.

Luteinizing hormone-releasing hormone (LHRH) (50 ng) was infused with a microcannula into hypothalamo-hypophysial stalk portal vessels of adult male rats. Anterior pituitaries were prepared for electron microscopy at 1, 5, 10, 15, 30 and 60 minutes after infusion. Granule release (exocytosis) from gonadotrophs was stimulated within one minute. Evidence of increased protein synthesis began at 5-10 minutes but was not maximal until 15 minutes. The majority of new granules appeared in the Golgi apparatus at 15 and 30 minutes. This study provides morphological evidence for LHRH-induced hormone and synthesis release under physiological conditions.

Animals↗