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Biomedical subjects

P V Ramachandran

Publications and source records attributed to P V Ramachandran.

11 recordsLinked to original sources
PubMed2002

Imaging spectrum of bronchial carcinoid--a case of central bronchial obstructing lesion.

Here one case of bronchial carcinoid is reported, which presented as intrabronchial obstructing lesion with sequelae. Carcinoid syndrome is quite uncommon with bronchial carcinoids and x-ray or CT usually gives non-specific appearances. Still, the relatively younger age group of patients and presence of obstructing lesions in major bronchi with features like extraluminal extension and mucoid impactions are helpful signs. However, a few instances of carcinoid mimics do occur during imaging studies, like other types of intrabronchial tumours and long standing foreign bodies.

Adult↗
PubMed2001

An exceptional hydroboration of substituted fluoroolefins providing tertiary alcohols.

[reaction--see text] A rare hydroboration-oxidation providing tertiary-alcohols has been achieved in the case of 1,1,2-perfluoroalkyl(aryl)ethylenes. The hydroboration of substituted perfluoroalkyl(aryl)ethylenes with dichloroborane reveals that the regioselectivity does not entirely depend on the electronics of the fluoroolefins.

Journal Article↗
PubMed2001

Efficient intramolecular asymmetric reductions of alpha-, beta-, and gamma-keto acids with diisopinocampheylborane.

[figure: see text] alpha-, beta-, and gamma-Keto acids are reduced with diisopinocampheylborane at room temperature to the corresponding hydroxy acids with predictable stereochemistry in very high ee. The gamma-hydroxy acids produced were conveniently cyclized to the corresponding lactones. This provides a simple synthesis of 4-hexanolide, a component of the pheromone secreted by the female dermestid beetle Trogoderma glabrum.

Animals↗
PubMed2001

Asymmetric synthesis of umuravumbolide.

[figure: see text] This first asymmetric synthesis of enantiopure desacetylumuravumbolide and umuravumbolide via asymmetric reduction, allylboration, and ring-closing metathesis confirms their revised structures and configurations. A convenient procedure to upgrade the enantiopurity of alpha,beta-acetylenic alcohols is also described.

Catalysis↗
PubMed1996

Effect of acute and chronic fluoxetine on extracellular dopamine levels in the caudate-putamen and nucleus accumbens of rat.

Recent studies indicate that an increase in serotonergic (5-HT) activity in the nucleus accumbens (NAc) produces an increase in dopamine (DA) release, providing a possible mechanism for the involvement of DA in the therapeutic action of selective serotonin reuptake inhibitor (SSRI) antidepressants. However, acutely administered fluoxetine (2.5, 5.0, or 10.0 mg/kg, i.p.) failed to elevate extracellular levels of DA, or its metabolites in the NAc or caudate-putamen (CP). In fact, the highest dose produced a small (20%) decrease in DA levels in the NAc. Extracellular levels of the 5-HT metabolite 5HIAA were consistently decreased at all doses of fluoxetine in both structures. Since SSRIs generally require several weeks of treatment to be effective clinically, a second experiment examined the effect of chronic administration of fluoxetine. Chronic (21 day) daily treatment with 5 mg/kg had no effect on NAc basal levels of DA, DA metabolites, or 5HIAA, relative to a saline-treated control group. Finally, pretreatment with fluoxetine appeared to slightly enhance the elevation of NAc DA induced by an injection of cocaine (10 mg/kg, i.p.), an effect that was not quite significant (P < .06). In conclusion, the 5-HT-induced facilitation of NAc DA neurotransmission described in the literature may not be relevant to the therapeutic action of fluoxetine.

Animals↗
PubMed1995

Effect of a chiral 4-alkyl substituent in hallucinogenic amphetamines.

The potency of hallucinogenic amphetamine derivatives of the 1-(2,5-dimethoxy-4-alkylphenyl)-2-aminopropane type drops dramatically when the length of the 4-alkyl substituent exceeds propyl or when the substituent is branched. This investigation was directed toward evaluating changes in behavioral and biochemical pharmacology resulting from introducing chirality into the 4-alkyl group of such analogues. Two diastereoisomeric derivatives of this class containing a 4-(R or S)-2-butyl substituent, 11a,b, respectively, were studied. A slight but nonsignificant potency difference in d-lysergic acid diethylamide tartrate (LSD)-like discriminative stimulus properties and equal affinity for [125I]-(R)-(2,5-dimethoxy-4-iodophenyl) isopropylamine-labeled serotonin 5-HT2A/C radioligand-binding sites were observed. Thus, the portion of the receptor that interacts with the 4-alkyl substituent on hallucinogenic amphetamines does not present a highly asymmetric environment to the ligand. However, since both test drugs had higher binding affinity but lower LSD-like behavioral potency than the prototype compound with a 4-methyl group ((2,5-dimethoxy-4-methylphenyl)isopropylamine, 2), 11a,b may differ in their receptor agonist efficacy from more behaviorally active compounds such as 2.

Amphetamines↗