PubMed Health⌕ Search

Biomedical subjects

R W Colburn

Publications and source records attributed to R W Colburn.

At least 37 records · Page 2Linked to original sources
PubMed1989

The differentiation of NSAIDs and prostaglandin action using a mechanical visceral pain model in the rat.

In order to determine the role of peripheral prostanoids in a newly developed mechanical visceral pain model, several NSAIDs were studied. Systemic acetylsalicylic acid and mefenamic acid, in doses known to produce cyclooxygenase inhibition, produced limited or no analgesia using a duodenal distension model and a behavioral scale for assessment. In contrast, indomethacin at 1 mg/kg, a dose 1/100th of the highest dose of the above compounds, had a marked analgesic effect in the visceral pain model (32% of control response). These data suggest that a duodenal distension stimulus does not have a peripheral prostaglandin E2-mediated nociceptive mechanism. Furthermore, the results obtained with indomethacin support an alternate, possibly central nonprostanoid visceral antinociceptive action.

Acetates↗
PubMed1986

Transport of long-chain fatty acids in Escherichia coli. Evidence for role of fadL gene product as long-chain fatty acid receptor.

Transport of long-chain fatty acids (LCFA) across the cytoplasmic membrane of Escherichia coli requires functional fadL and fadD genes. The fadD gene codes for an acyl-CoA synthetase (fatty acid: CoA ligase (AMP forming] which has broad chain length specificity and is loosely bound to the cytoplasmic membrane. The fadL gene codes for a 43,000-dalton cytoplasmic membrane protein which, acting by an unknown mechanism, is needed specifically for LCFA transport. As a first step to define the role of the fadL gene product, studies were performed to determine if it functions as a LCFA receptor. The LCFA-binding activity was quantitated in intact cells in the absence of LCFA transport by comparing the binding of LCFA in fadD fadL and fadD fadL+ strains. These studies revealed that (i) fadD fadL+ strains bind 6-fold more LCFA than fadD fadL strains; (ii) fadD fadL strains harboring a plasmid containing the fadL gene bind 16-fold more LCFA than fadD fadL strains harboring only the plasmid vector; and (iii) the fadL-specific LCFA-binding activity is regulated by the fadR gene and catabolite repression. Studies with fadL strains harboring fadL plasmids containing in vitro constructed deletions indicate that mutations which alter the physical properties of the 43,000-dalton fadL gene product also affect fadL gene product-specific LCFA-binding activity. Overall, these studies suggest that one role of the fadL gene product in the LCFA transport process is to sequester LCFA at sites in the cell membrane for transport.

Bacterial Proteins↗
PubMed1986

Effect of aging and endurance training on tissue catecholamine response to strenuous exercise in Fischer 344 rats.

The purpose of the present investigation was to determine the catecholamine response in various tissues to a bout of strenuous exercise in young, adult, and old Fischer 344 rats. Further, to study the effect of endurance training on this response, animals from each age group underwent ten weeks of treadmill running at 75% of their functional capacity. On completion of the training program, all animals demonstrated significant increases (P less than 0.05) in VO2max and endurance capacity. At rest or immediately after an acute bout of strenuous exercise, animals were killed, and the heart, liver, kidney, and adrenals were removed for subsequent catecholamine analysis. Resting cardiac catecholamine levels declined significantly with age. In response to an acute exercise bout, epinephrine (E) levels in the heart were greatly reduced with age averaging 141.8, 62.3, and 21.7 ng/g for the 6-, 15-, and 27-month-old untrained group, respectively. The 15- and 27-month-old trained animals demonstrated significantly higher E levels (33% and 91%) than controls. A similar trend was found for norepinephrine (NE) content in the heart in response to acute exercise, with a marked reduction occurring with advancing age (904.6, 580.1, and 400.8 ng/g heart for 6-, 15-, and 27-month-old untrained groups, respectively). Again, training induced a greater NE response in the older trained animals compared to age-matched controls. In contrast, adrenal catecholamine levels showed a tendency to increase with age. It was concluded that when challenged with strenuous physical stress, cardiac catecholamine content is markedly diminished with age. Further, ten weeks of endurance training can attenuate this functional decline.

Adrenal Glands↗
PubMed1984

Influence of age and cold stress on plasma catecholamine levels in rats.

We measured arteria plasma concentrations of norepinephrine (NE) and epinephrine (E) in pentobarbital-anesthetized 3- and 24-month-old male F344 rats in basal (control) conditions and following acute cold exposure (6 h at 4 degrees C). Basal levels of circulating NE and E were also determined in 3- and 24-month-old Sprague-Dawley animals. Basal NE did not change between 3 and 24 months of age in either strain of rat, whereas older animals of both strains had significantly higher basal plasma E concentrations compared to younger counterparts. Cold exposure increased plasma NE approximately 100 pg . ml-1 above respective basal levels in 3- and 24-month-old F344 rats, suggesting no age-related differences in sympathetic nervous system reactivity to cold stress. Plasma E in young cold-stressed F344 animals was elevated approximately 336 pg . ml-1 (287%) over basal levels, and approximately 370 pg . ml-1 (155%) over basal levels in older animals, resulting in cold-induced circulating E concentrations of 515 +/- 90 pg . ml-1, and 1040 +/- 122 pg . ml-1 in 3- and 24-month-old animals, respectively. Thus, arterial plasma E concentration in older rats is significantly elevated, both in basal conditions and in response to acute cold stress, suggesting enhanced adrenal medullary activity with advancing age.

Adrenal Medulla↗
PubMed1981

Efficient extraction and mass spectrometric assay of serotonin in biological fluids.

A gas chromatographic mass spectrometric assay for serotonin (5-hydroxytryptamine) has been developed. Serotonin is acylated in homogenized biological media, efficiently extracted into ethyl acetate, and further derivatized with pentafluoropropionic anhydride. Mass spectral characterization of derivatized serotonin using electron and positive or negative chemical ionization indicates that electron ionization mass spectrometry is useful for serotonin assay in most biological fluids and tissues, but that electron capture negative chemical ionization is required for samples containing less than 1-2 ng (cerebrospinal fluid). An assay limit of 10 pg per sample has been established. Examples of applications for the assay of serotonin in human platelets, rat spinal cord, and monkey cerebrospinal fluid are presented.

Animals↗
PubMed1979

Distribution and excretion in the rat and monkey of [82Br] bromocriptine.

Radiolabeled bromocriptine was administered to rats and monkeys and its tissue distribution, rate of excretion and metabolism were determined. In both species, [82Br]bromocriptine is predominantly concentrated in the liver, metabolized and then excreted through bile. Extractable free drug is undetectable in blood after 30 min. After 2 hr, the estimated concentration of free drug in rat brain is 2 x 10(-8) M. Terminal phase half-lives of radiolabel excretion were 2.9 days for the rat and 27.3 days for the monkey. The retained organically bound 82Br is present in a form more polar than bromocriptine.

Animals↗
PubMed1976

Localization of triiodothyronine in nerve ending fractions of rat brain.

Radioactive triiodothyronine reaching the rat brain after intravenous administration is rapidly and selectively taken up in the nerve ending fraction. A concentration gradient of radioactivity from brain cytosol to synaptosomes is observed at 5 min, increases linearly over the first hour, and is maintained for at least 10 hr. Radioactivity in the synaptosomes is due to triiodothyronine (90%) plus a single unidentified metabolite (10%). Approximately 85% of the synaptosomal radioactivity is released by osmotic disruption of the particles. The process of selective uptake, concentration, and retention of triiodothyronine in nerve terminals of the rat brain may be related to the sympathomimetic and behavior-altering effects of the thyroid hormones.

Animals↗