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D W Robertson

Publications and source records attributed to D W Robertson.

100 records · Page 6Linked to original sources
PubMed1981

Interaction of a high affinity anti-estrogen (alpha-[4-pyrrolidinoethoxy]phenyl-4-hydroxy-alpha'-nitrostilbene, CI628M) with uterine estrogen receptors.

The polar metabolite of the anti-estrogen alpha-[4-pyrrolidinoethoxy]phenyl-4-methoxy-alpha'-nitrostilbene (CI628), that is selectively accumulated by the nuclear estrogen receptor in vivo, is identified as the corresponding free phenol (alpha-[4-pyrrolidinoethoxyl]phenyl-4-hydroxy-alpha'-nitrostilbene (CI628M) and has been prepared in high specific activity tritium-labeled form to study its interaction with the rat uterine estrogen receptor. CI628M has an affinity for the cytosol receptor that is comparable to that of estradiol (Kd (CI628M) = 0.16 nM; Kd (estradiol) = 0.28 nM), and the binding of these two compounds is mutually competitive. Dissociation of the CI628M complex with the estrogen receptor is somewhat slower than that of the estradiol complex, and prewarming the complexes at 28 degrees C causes a characteristic decrease in the rate of dissociation. On low salt sucrose gradients, the CI628M and estradiol cytoplasmic receptor complexes both sediment as 8S species; their sedimentation profiles on high salt gradients are somewhat different, however. While the estradiol receptor complex shows mainly a 4.6S species that shifts to a 5.8S species upon warming, the unwarmed CI628M complex is predominantly 5.8S and becomes somewhat more disperse upon warming. Under high salt conditions, there is a progressive shift of the 4.6S to the 5.8S species as cytosol concentration increases; the CI628M complex shows a greater tendency to form the more rapidly sedimenting form at all cytosol concentrations. After in vivo injection of [3H]CI628M, the uterine nuclear receptor sediments as a characteristic 5S species. Cytosol receptor complexes with estradiol and CI628M, maintained at 0 degrees C, show very little binding to ATP-Sepharose, while after warming, 50-60% of both complexes are bound by the resin. Both complexes also show similar elution profiles from DNA-cellulose columns; however, the extent of binding of the [3H]CI628M receptor complex to the column is consistently only 40-50% that of the estradiol receptor complex. These results indicate that the properties of the uterine estrogen receptor complexed with estradiol and with the high affinity anti-estrogen CI628M are very similar. The differences observed in the behavior of the CI628M cytosol receptor complex on high salt sucrose gradients and on DNA-cellulose columns, though quantitative rather than qualitative, may be indicative of differences in receptor properties that are important to the antagonist activity of this compound.

Animals↗
PubMed1981

Tamoxifen aziridines: effective inactivators of the estrogen receptor.

Two analogs of the antiestrogen tamoxifen, which bear a chemically reactive aziridine function in place of the dimethylamino group, bind to the estrogen receptor from rat uterus and from MCF-7 human breast cancer cells and appear to react irreversibly with the receptor at the estrogen binding site, in a time-and concentration-dependent fashion. BEcause these compounds are effective receptor inactivators in uterus and breast cancer cells, they should prove to be useful probes for investigating the role of receptor in regulating cellular responses to estrogen and in studying the dynamics of estrogen receptor synthesis and turnover.

Animals↗
PubMed1979

Antiestrogens and antiestrogen metabolites: preparation of tritium-labeled (+/-)-cis-3-[p-(1,2,3,4-tetrahydro-6-methoxy-2-phenyl-1-naphthyl)phenoxyl]-1,2-propanediol (U-23469) and characterization and synthesis of a biologically important metabolite.

The Upjohn antiestrogen (+/-)-cis-3-[p-(1,2,3,4-tetrahydro-6-methoxy-2-phenyl-1-naphthyl)phenoxy]-1,2-propanediol (2b, U 23469) has been prepared in tritium-labeled form by reduction of an unsaturated dihydronaphthalene precursor with carrier-free tritium gas over a palladium catalyst followed by alkylation with 3-iodo-1,2-propanediol. After extensive chromatographic purification, the final material was obtained with a specific activity of 13 Ci/mmol and a radiochemical purity of 94%. In vivo studies with immature rats show that [3H]2b is slowly converted to a more polar metabolite that is selectively accumulated in the nuclear fraction of the uterus where it is bound to the estrogen receptor. Chromatographic comparisons indicate that this metabolite is the demethylated analogue 2c, a compound that has an affinity for estrogen receptor more than 300 times greater than that of 2b. These studies suggest that the demethylated analogue 2c may be a biologically important metabolite of 2b that is involved in the action of this antiestrogen.

Animals↗
PubMedDate not supplied

Pharmacology of LY201409, a potent benzamide anticonvulsant.

LY201116 [4-amino-N-(2,6-dimethylphenyl)benzamide], an effective anticonvulsant in several animal models, is rapidly metabolized by N-acetylation in rats, mice and monkeys. In an attempt to preclude metabolic N-acetylation sterically, we investigated LY201409, an analogue possessing two methyl groups ortho to the 4-amino substituent. This structural modification successfully altered the metabolic pathway, and LY201409 displayed potent anticonvulsant activity. LY201409 antagonized maximal electroshock (MES)-induced seizures with ED50 values of 16.2 and 4.2 mg/kg after oral administration to mice and rats, respectively. The compound did not effectively antagonize seizures induced by a variety of chemical convulsants in rats, but did block pentylenetetrazol-induced seizures in mice. Thus, among the classic anticonvulsants, the profile of phenytoin most closely resembles that of LY201409. Studies conducted with the rotorod and horizontal screen assays in mice and behavioral studies in rats suggested that doses of LY201409 that produced CNS side-effects such as sedation or ataxia were well separated from the anti-MES doses. LY201409 was a potent, dose-dependent potentiator of hexobarbital-induced sleeping time in mice. Oral administration of 6.0 mg/kg led to a 372% increase in sleep time relative to control values. Although LY201409 is a potent and effective anticonvulsant, it is also one of the most potent potentiators of hexobarbital-induced sleep time yet described.

Animals↗
PubMedDate not supplied

Pharmacological effects of enantiomers of 4-amino-N-(alpha-methylbenzyl)benzamide, a chemically novel anticonvulsant.

LY 188544,S,R-4-amino-N-(alpha-methylbenzyl) benzamide, and its two stereoisomers are structurally novel anticonvulsants. The anticonvulsant profile of LY 188544 after intraperitoneal administration to mice was determined in standard anticonvulsant tests: maximal electric shock (MES), strychnine tonic-extensor, and threshold tests using pentylenetetrazol, picrotoxin, and bicuculline. In this series of tests, LY 188544 had good activity in the MES test and some activity in the three threshold tests. Thus, its profile of activity was most similar to that of phenobarbital, and less similar to that of phenytoin and carbamazepine. After oral administration to mice and rats, LY188544 was effective in the MES test, but did not provide complete protection in the threshold pentylenetetrazol test. When the individual stereoisomers, LY188545 (S isomer) and LY188546 (R isomer), were evaluated after oral administration, LY188545 was 2.2 times more potent than LY188546 against MES-induced seizures. However, when evaluated after intravenous administration, the potency difference was only 1.1. LY188546 was the least toxic in terms of neurological impairment. All compounds had good protective indexes (ratio between doses for neurological impairment and doses for anticonvulsant efficacy in the MES test). LY188545 and LY188546 potentiated hexobarbital sleeping time after acute administration but not after chronic (4-day) administration. Tolerance did not develop to the effects of LY188546 on MES or neurological impairment after 4 days of administration. These results suggest that LY188546 is a chemically novel anticonvulsant with a promising pharmacological profile.

Animals↗
PubMedDate not supplied

Nasal resistance during wakefulness and sleep in normal man.

Previously, we reported an increase in supralaryngeal resistance during sleep in normal man. Since nasal resistance is known to fluctuate over a wide range of circumstances, we hypothesized that the increase in supralaryngeal resistance observed was due to an increase in nasal resistance. Therefore, the purpose of this investigation was to examine changes in total and unilateral nasal resistance in five normal, adult males during wakefulness, Stage 2 (non-REM) sleep and REM sleep. Transnasal pressure and flow were measured for each side of the nose. Resistance was calculated from the slope of the linear portion of the transnasal pressure-flow relationship. During wakefulness and sleep, resistance was substantially higher on one side of the nose or unilateral total occlusion was present. This high resistance fluctuated from side to side during sleep. The transition of high resistance from side-to-side occurred rapidly. On turning to either side, the side of the nose with the high resistance was not necessarily the gravitationally-dependent side. Total nasal resistance did not change significantly during sleep. We concluded that 1) resistance on one side of the nose is usually considerably higher than the other side, 2) this high resistance side alternates during sleep as well as wakefulness, 3) since this alteration occurs rapidly and is not dependent on gravity, reflexes are likely involved and 4) changes in total nasal resistance were not responsible for the increased supralaryngeal resistance we have observed during sleep.

Adult↗
PubMedDate not supplied

Comparison of indolidan analog binding sites of drug antibody and sarcoplasmic reticulum with inhibition of cyclic AMP phosphodiesterase.

Dihydropyridazinone(DHP) derivatives such as indolidan are positive inotropic agents that show inhibition of cyclic AMP phosphodiesterase(PDE) activity. Indolidan inhibition is selective for PDE3 among the seven PDE gene families. DHP derivatives and related analogs have been used to define critical regions of the active site of PDE3 isoforms and radiolabeled analogs have been used to define indolidan sarcoplasmic reticulum (SR) receptor sites. We report here studies comparing the structure-activity relationships (SAR) for PDE3 inhibition with indolidan binding to two types of sites: canine SR and a monoclonal antibody derived against indolidan conjugated to a hemocyanin. SR and monoclonal antibody binding both fit singlesite, high affinity models (IC50 = 1.2 and 62 nM) that were near 52 and 360 times that of SR PDE3. Indolidan and thirteen analogs showed similar competition with either SR 3H-LY186126 binding or SR PDE3 inhibition. Antibody binding maintained selectivity but showed a different rank order potency for SR binding. Indole ring C3 methylation increased and DHP ring C4' methylation decreased indolidan monoclonal antibody binding while both substitutions increased SR binding. These studies support the hypothesis that SR PDE3 is a cardiotonic receptor site in myocardial membranes and indicate that models of the structural features of binding sites derived from inhibitor data alone could produce models with limited topography relative to the natural ligand.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMedDate not supplied

Metabolism of the prodrug DEGA (N-(2,6-dimethylphenyl)-4-[[(diethylamino)acetyl]amino]benzamide) to the potent anticonvulsant LY201116 in mice. Effect of bis-(p-nitrophenyl)phosphate.

In mice, the diethylglycineamide analogue of LY201116, DEGA (N-(2,6-dimethylphenyl)-4-[[(diethylamino)acetyl]amino]benzamide), is metabolized by consecutive N-deethylations for form MEGA and GA; the monoethylglycineamide and glycineamide analogues of LY201116, respectively. All of these compounds are in turn hydrolyzed to form LY201116 [4-amino-N-(2,6-dimethylphenyl)benzamide]. LY201116 is N-acetylated to form the N-acetyl metabolite, NAC. NAC is also deacetylated to reform LY201116. All of the above compounds inhibit maximal electroshock-induced seizures (MES) in mice. After oral administration, the potencies of these compounds were similar at their time of peak anticonvulsant effect. However, the MES ED50 values for the above compounds 5 min after iv dosing were 43, 13, 2, and 0.5 mg/kg for DEGA, MEGA, GA, and LY201116, respectively. Similar plasma levels of LY201116 were produced in mice 5 min after iv dosing with the respective ED50 values of the above compounds, which suggested that all of the compounds produced their anticonvulsant effects via LY201116. The in vivo metabolism of DEGA and MEGA but not GA to LY201116 was inhibited by the acylamidase inhibitor bis-(p-nitrophenyl) phosphate (BNPP). Mice predosed with BNPP were not protected by DEGA and MEGA from MES-induced seizures and the plasma samples contained little or no LY201116. The metabolism of GA to LY201116 was not inhibited by BNPP, and GA was an active anticonvulsant in BNPP-pretreated mice. The apparent iv potency of DEGA increased dramatically with time after dosing, again suggesting time-dependent, metabolically mediated liberation of the more potent anticonvulsant LY201116.

Animals↗