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Biomedical subjects

T Lee

Publications and source records attributed to T Lee.

At least 415 records · Page 23Linked to original sources
PubMed1977

11,12-Secoprostaglandins. 3. 8-Alkylthio(sulfinyl and sulfonyl)-12-hydroxyalkanoic acids and related compounds.

A series of 8-alkylthio(sulfinyl and sulfonyl)-12-hydroxyalkanoic acids which embody structural features of 11,12-secoprostaglandins was synthesized and evaluated for their ability to mimic the E series prostaglandins in stimulating cAMP formation in the mouse ovary and in binding to the rat lipocyte prostaglandin receptor. A key member of the series, 8-methylsulfonyl-12-hydroxyheptadecanoic acid, markedly stimulated cAMP formation at reasonable pharmacological concentrations, shows significant affinity for a prostaglandin receptor, and effectively inhibits antigen-induced lymphocyte transformation. In contrast, this compound is not a substrate for 15-hydroxyprostaglandin dehydrogenase, the major prostaglandin-metabolizing enzyme.

Animals↗
PubMed1977

Cerebral dopamine agonist properties of some 2-aminotetralin derivatives after peripheral and intracerebral administration.

A series of variously N-substituted 2-aminotetralins having OH groups at 5 and 6 and at 6 and 7 positions, as well as nonoxygenated systems, has been evaluated for central dopaminergic effects. Stereotypical behavioral effects (sniffing, compulsive gnawing, and hyperactivity) produced by direct intracerebral administration of some of the agents were shown to differ strikingly from responses resulting from peripheral administration. The centrally mediated responses of hyperactivity and sterotypical gnawing-biting head and limb movements were shown to be separable in some test compounds. An improved route to 2-aminotetralin systems has been utilized for some of the compounds, which involves Pummerer rearrangement and cyclization of beta-keto sulfoxides and reductive amination of beta-tetralones with a NaBH4-carboxylic acid complex.

2-Naphthylamine↗
PubMed1977

Prostaglandin isosteres. 1. (8-Aza-, 8,10-diaza-, and 8-aza-11-thia)-9-oxoprostanoic acids and their derivatives.

A series of novel (8-aza-, 8,10-diaza-, and 8-aza-11-thia)-9-oxoprostanoic acids has been synthesized and evaluated for their ability to mimic the E series prostaglandins in stimulating cAMP formation in the mouse ovary and in binding to the rat kidney plasma prostaglandin receptor. 7-[2-(3-Hydroxyoctyl)-1,1,4-trioxo-3-thiazolidinyl]heptanoic acid markedly stimulates cAMP formation at reasonable pharmacological concentrations and avidly binds to the rat kidney prostaglandin receptor.

Animals↗
PubMed1977

Conformational requirements for dopamine-induced vasodilation.

The availability of a series of semi-rigid analogs of dopamine and epinine has made it possible to investigate the conformational requirements for action on dopamine and beta2-adrenergic vascular receptors. The analogs were screened for dopamine-agonist action by intra-arterial injections into the renal vascular bed and for beta2-adrenergic activity by similar injections into the femoral vascular bed in dogs pretreated with phenoxybenzamine. 2-Amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene (A-6,7-DTN) and its N-methyl derivative (analogous to the trans beta rotamer of dopamine) exhibited pronounced dopamine-agonist activity and minimal beta2-adrenergic activity. In contrast, the semi-rigid analog of the trans alpha rotamer of dopamine (2-amino-5,6-dihydroxy-1,2,3,4-tetrahydronaphthalene; A-5,6-DTN) and its N-methyl derivative exerted pronounced beta2-adrenergic activity but were inactive as dopamine agonists.6,7-Dihydroxytetrahydroisoquinoline, a semi-rigid analog of the cis beta rotamer of dopamine, did not produce renal vasodilation. These results indicate that a conformation of dopamine similar to that found in A-6,7-DTN is required for dopamine-vascular activity, while the conformation found in A-5,6-DTN is preferred for interaction with beta2-adrenergic receptors.

Animals↗
PubMed1977

Third system for neutral amino acid transport in a marine pseudomonad.

Uptake of leucine by the marine pseudomonad B-16 is an energy-dependent, concentrative process. Respiratory inhibitors, uncouplers, and sulfhydryl reagents block transport. The uptake of leucine is Na+ dependent, although the relationship between the rate of leucine uptake and Na+ concentration depends, to some extent, on the ionic strength of the suspending assay medium and the manner in which cells are washed prior to assay. Leucine transport can be separated into at least two systems: a low-affinity system with an apparent Km of 1.3 X 10(-5) M, and a high-affinity system with an apparent Km of 1.9 X 10(-7) M. The high-affinity system shows a specificity unusual for bacterial systems in that both aromatic and aliphatic amino acids inhibit leucine transport, provided that they have hydrophobic side chains of a length greater than that of two carbon atoms. The system exhibits strict stereospecificity for the L form. Phenylalanine inhibition was investigated in more detail. The Ki for inhibition of leucine transport by phenylalanine is about 1.4 X 10(-7) M. Phenylalanine itself is transported by an energy-dependent process whose specificity is the same as the high-affinity leucine transport system, as is expected if both amino acids share the same transport system. Studies with protoplasts indicate that a periplasmic binding protein is not an essential part of this transport system. Fein and MacLeod (J. Bacteriol. 124:1177-1190, 1975) reported two neutral amino acid transport systems in strain B-16: the DAG system, serving glycine, D-alanine, D-serine, and alpha-aminoisobutyric acid; and the LIV system, serving L-leucine, L-isoleucine, L-valine, and L-alanine. The high-affinity system reported here is a third neutral amino acid transport system in this marine pseudomonad. We propose the name "LIV-II" system.

Amino Acids↗
PubMed1976

Reaction of N-(3-pyrene)maleimide with thiol groups of reticulocyte ribosomes.

The reaction of N-(3-pyrene)maleimide with thiol groups of rabbit reticulocyte ribosomes offers a possible fluorescent probe for studying ribosomal structure and conformation. At relatively low concentrations of N-(3-pyrene)maleimide a group of 30-40 readily reactive sulfhydryl residues is derivatized. The major ribosomal proteins containing these thiol groups are identified as S2 + S3, S5, S7, S8, S29, S31, S32, L1, L5, L6, L10 + L14, L15, L18 + L19, and L36. Ribosomal activity, as measured by the nonenzymic binding of phenylalanyl-tRNA and polyphenylalanine synthesis, is inhibited by this degree of reaction with N-(3-pyrene)maleimide. The inhibition is relieved by the prior binding of polyuridylic acid to the ribosomes while the extent of derivatization by N-(3-pyrene)-maleimide is diminished only slightly. The average relative polarization of the fluorescence of the ribosomal bound N-(3-pyrene)maleimide changes significantly with the degree of derivatization of ribosomal thiol groups or with the binding of polyuridylic acid, indicating the value of such a fluorescent thiol-derivatizing agent as a probe of ribosomal structure.

Animals↗
PubMed1976

Dopamine/neuroleptic receptors in basal hypothalamus and pituitary.

In order to determine whether the basal hypothalamus or the pituitary (or both) is the likely locus of action of the tuberoinfundibular (TI) dopamine neurons, these regions were examined for dopamine and neuroleptic receptors. High affinity receptors for haloperidol and dopamine were found in the rat pituitary while none were detected in rat basal hypothalamus. The relative ability of two neuroleptics, chlorpromazine and haloperidol, to displace (3H)haloperidol from the receptor in monkey pituitary is similar to that for rat striatum. The lack of receptors capable of binding (3H)haloperidol or (3H)dopamine in the basal hypothalamus strongly suggests that the TI neurons do not produce postsynaptic effects in this region. The pituitary receptors for (3H)haloperidol and (3H)dopamine have the characteristics of a functional system. The presence of neuroleptic/dopamine receptors in the pituitary and lack of such receptors in the basal hypothalamus supports the hypothesis that dopamine may act directly as a prolactin release inhibiting factor (PIF) rather than releasing PIF from adjacent nerve terminals in the median eminence.

Animals↗
PubMed1975

Antipsychotic drugs: direct correlation between clinical potency and presynaptic action on dopamine neurons.

Neuroleptic (antipsychotic) drugs inhibited the electrically stimulated release of [3-H] dopamine from rat striatal slices. The concentrations for 50 percent inhibition (ranging from 11.5 nanomolar for spiroperidol to 800 nanomolar for thioridazine) correlated closely with the average daily dosages of 25 neuroleptic drugs used clinically for schizophrenia. The correlation includes butyrophenones, phenothiazines, reserpine, pimozide, clozapine, and (plus)- butaclamol. Clinically inactive isomers [trans-thiothixene, trans-flupenthixol, and (minus)-butaclamol] required 20 to 1000 times higher concentrations than the active isomers to inhibit release. Compared to the inhibition of [3-H] dopamine release, much higher neuroleptic concentrations were needed to inhibit the electrically stimulated release of other neurotransmitters--[3-H] acetylcholine, [3-H-a1 (gamma-aminobutyric acid). The neuroleptic drugs may block the presynaptic coupling between impulse and neurosecretion.

Acetylcholine↗