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Biomedical subjects

R C Murphy

Publications and source records attributed to R C Murphy.

At least 235 records · Page 13Linked to original sources
PubMed1978

Mass spectrometric measurement of catecholamine turnover in rat hypothalamus after long-term L-dopa infusion.

To test the effect of L-dopa on norepinephrine turnover in rat hypothalamus, we gave steady-state, long-term (19-hour) infusions of L-dopa to conscious, restrained rats. After 19 hours, infusions were switched to identical doses of 2,5,6-trideutero-L-dopa (D3-L-dopa) and production of D3-dopamine and D3-norepinephrine was followed at intervals thereafter. Animals were sacrificed and their hypothalami were dissected and divided into left and right halves. Using gas chromatography-mass spectrometry, we measured isotopic enrichment with one side of the hypothalamus and, after the addition of deuterated internal standards, determined total concentration of dopamine and norepinephrine in the other half of the same hypothalamus. Maximal steady-state enrichment by a given dose of D3-L-dopa was determined by 19-hour infusions of D3-L-dopa alone. Results show that total dopamine production is proportional to dopa dose. Norepinephrine synthesis, on the other hand, proceeds at a constant rate that is independent of dopa dose or dopamine concentration and which is similar to the endogenous rate reported by others using tracer techniques.

Animals↗
PubMed1977

The normal occurrence of octopamine in the central nervous system of the rat.

An enzymatic assay for octopamine capable of detecting 50 pg of amine was developed and used to study the distribution of octopamine in regions of the rat central nervous system. The presence of octopamine in the rat pineal organ was confirmed by mass spectrometry; Administration of a monoamine oxidase inhibitor and of tyramine led to increases in CNS octopamine levels while the administration of reserpine intraperitoneally or 6-hydroxydopamine intraventricularly led to decreases in octopamine levels. The results suggest that in the mammalian CNS octopamine is present in neural structures where it may be involved in synaptic function.

Animals↗
PubMed1976

Isocratic separation of some purine nucleotide, nucleoside, and base metabolites from biological extracts by high-performance liquid chromatography.

Separation of ATP, ADP, AMP, adenine, adenosine, cAMP, ITP, IDP, IMP, hypoxanthine, inosine, cIMP, the guanine series, NAD, NADPH, xanthine, 3-methylxanthine, theobromine, theophylline, and caffeine was accomplished using high-performance liquid chromatography with a microparticulate reversed-phase column. Under isocratic conditions all compounds could be eluted with reasonable resolution and retention time. Quantitation by peak height for several of the compounds was used to the 10-ng level.

Adenine Nucleotides↗
PubMed1975

On the development of the lymphoid follicles of the bursa of Fabricius.

The structural features of the development of the bursa of Fabricius in white Leghorn chick embryos are depicted at carefully timed intervals during embryogenesis, with emphasis on the sequence of events between the ninth and twelfth days of incubation. The direction and character of the migration of lymphoid cell precursors and granulocytes from the intravascular space to intraepithelial sites, where the formation of the primitive lymphoepithelial nodule takes place, is demonstrated. The mechanism of the mode of migration of these cells through the stromal epithelial interface is described and illustrated with electron micrographs and their role in the development of the primitive lymphoid follicles is described and discussed.

Animals↗
PubMed1975

Bladder explosions during transurethral surgery.

Gases liberated during transurethral electrosurgery are common to all tissues with hydrogen produced in high concentration. We postulate that the majority of hydrogen is derived from electrolysis of intracellular water. Only with the addition of outside oxygen does the gaseous mixture become potentially explosive.

Electrolysis↗
PubMed1975

The separation and identification of dopamine 3-O-sulfate and dopamine 4-O-sulfate in urine of Parkinsonian patients.

A method is described for the isolation and measurement of dopamine 3-O-sulfate and dopamine 4-O-sulfate. The sulfate isomers of dopamine were synthesized chemically by the reaction of dopamine with sulfuric acid. The isomers were isolated by anion-exchange column chromatography and the identities of the two isomers were confirmed by gas chromatography coupled with mass spectrometry. A method is described for the assay of the two isomers by high-pressure liquid chromatography. When Parkinsonian patients were treated with 4.0 g/day of L-dopa, the amount of dopamine 3-O-sulfate excreted in the urine was 19.6 times that of dopamine 4-O-sulfate. When untreated Parkinsonian patients received tracer quantities of 3H-L-dopa either intravenously or orally, 3H-dopamine 3-O-sulfate was the predominant isomer but the amounts were only 3 times those of the 4-isomer. Greater quantities of both isomers were excreted when 3H-L-dopa was given orally as compared to intravenous administration. Since dopamine 3-O-sulfate is the predominant sulfate isomer, it is concluded that sulfate conjugation of dopamine could possibly compete with 3-O-methylation in determining the resultant conjugated product.

Administration, Oral↗
PubMed1971

Absolute configuration of Cecropia juvenile hormone.

The absolute configuration of the predominant Cecropia hormone, methyl 12,14-dihomojuvenate, has been determined to be methyl (E,E)-(10R,11S)-(+)-10,11-epoxy-7-ethyl-3,11-dimethyl-2, 6-tridecadienoate (I). The less abundant hormone, methyl 12-homojuvenate, can be presumed by analogy to have the corresponding 3,7,11-trimethyldienoate structure (II). The assignment has been established with microamounts of substance by applying Horeau's method to the glycol derivative (III) of the hormone.The course of the perchloric acid-catalyzed epoxide ring opening of I was checked by conducting the conversion in (18)O-labeled water. It has been ascertained that the configuration at the secondary hydroxyl group of the resulting III remained unchanged. On the other hand, the hydration proceeded with a surprisingly high rate of cis opening.

Animals↗