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Biomedical subjects

K E Light

Publications and source records attributed to K E Light.

At least 37 records · Page 2Linked to original sources
PubMed1985

Alteration of dopamine metabolism in different brain regions of the rabbit by estradiol and tamoxifen.

Tamoxifen citrate, a mixed estrogen agonist-antagonist, and estradiol 17-beta administered separately for 14 days significantly reduced dopamine and dihydroxyphenylacetic acid in the cortex and hypothalamus regions of the brain in immature female rabbits. In addition to these areas, estradiol also reduced dopamine and dihydroxyphenylacetic acid in the striatum but tamoxifen treatment significantly reduced only dihydroxyphenylacetic acid concentration in the striatum. When estradiol and tamoxifen were injected together, dopamine and dihydroxyphenylacetic acid concentrations were reduced only in the cortex. Specific binding of [3H]spiperone to dopamine receptors was significantly increased by both estradiol and tamoxifen in the hypothalamus but only tamoxifen increased dopamine binding in the striatum. A low dose of tamoxifen, either alone or in combination with estradiol, increased uterine weight, but a higher dose of tamoxifen was neither an estrogen agonist nor antagonist. These studies indicate that estradiol and tamoxifen alter dopamine metabolism in the various regions of brain differentially. The estrogen agonist activity of tamoxifen does not correspond to antidopaminergic action of estradiol in the striatum.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1985

Characterization of (3H)-spiperone binding to alpha 1-adrenergic receptors in a smooth muscle cell line.

Although (3H)-spiperone has been demonstrated to interact at both dopamine (D2) and serotonin (S2) receptors, it remains a popular choice for characterization of the D2-receptor using both in vitro and in vivo and in vivo assay techniques. Using a clonal smooth muscle cell culture line (DDT1 MF-2), which has previously viously been characterized as possessing alpha 1- and beta 2-adrenergic receptors, we have found that (3H)-spiperone also has a significant affinity for alpha 1-adrenergic receptors. Our results are consistent with other literature reports which have suggested that spiperone may interact at alpha 1-receptors and we have characterized this interaction. We have also found an additional, high affinity binding site for spiperone on these cells which may represent a D2 - receptor. Characterization of this high-affinity site has been difficult since it is present in very low density. We conclude that (3H)-spiperone binds with high affinity to at least three known neurotransmitter receptor sites: D2-dopamine, S2-serotoninn and alpha 1-adrenergic. The binding to the alpha 1-adrenergic receptor exhibits stereospecificity and a considerable degree of similarity in pharmacological profile to the D2-dopamine receptor.

Animals↗
PubMed1984

Altered calcium concentration and rabbit atrial H1-receptors.

Rabbit atria were incubated in various concentrations of calcium (0.9, 1.8 and 3.6 mM) and then homogenized and histamine H1-receptors analysed by radioligand binding using (3H)-pyrilamine. Only atria incubated in 3.6 mM calcium showed an alteration in (3H)-pyrilamine binding. In these tissues the Kd of H1-receptors for (3H)-pyrilamine was increased suggesting a decrease in the affinity of the H1-receptor. That this decreased affinity is due to altered calcium concentrations was demonstrated by showing that no change in histamines' chronotropic effects were produced by decreasing the sodium concentration to produce the same calcium/sodium ratio compared to high calcium alone. We conclude that calcium has effects directly on H1-receptor affinity and appears to produce a decrease in the ability of histamine to bind.

Animals↗
PubMed1984

Central and peripheral receptors in guinea-pigs exposed to simulated high altitude.

Guinea-pigs, chronically exposed to simulated high altitude of 6000 m, showed alterations in some, but not all, neurotransmitter-receptor systems. Thus, peripheral (cardiac) beta-adrenergic receptors were decreased in numbers (Bmax) with an increased affinity although no alterations in endogenous cardiac norepinephrine content were found. In contrast, H1-histamine receptors in the guinea-pig ventricle and brain showed no changes in Bmax or affinity. Dopamine receptors of the caudate nucleus showed no differences between control and altitude-exposed guinea-pigs, although previous reports demonstrated a significant increase (19%) in the content of endogenous dopamine of the caudate. Thus, chronic exposure to simulated high altitude altered beta-adrenergic receptors so that they were more sensitive to small ligand concentrations and less sensitive to large ligand concentrations.

Altitude↗
PubMed1984

Low-load prolonged stretch vs. high-load brief stretch in treating knee contractures.

This study was designed to compare the results of a traditional method of stretching knee flexion contractures by high-load brief stretch (HLBS) with the results of an experimental method of prolonged knee extension by skin traction, low-load prolonged stretch (LLPS). End range of passive knee extension was measured by standard goniometry. Subjects were 11 nonambulatory residents of a nursing home who had demonstrated gradually progressive bilateral knee contractures. Each subject served as his or her own control with one lower limb receiving LLPS and the other limb receiving HLBS and passive range of motion (PROM). Sequential medical trials were used as the clinical research design. Whether comparing the LLPS limb PROM measurements pretreatment and posttreatment (p less than or equal to .05) or the HLBS to the LLPS limb PROM recordings posttreatment (p less than or equal to .05), the results demonstrated a preference for LLPS in the treatment of knee contractures in the immobile nursing home resident.

Aged↗
PubMed1983

Alterations in CNS amine levels by acclimatization to hypobaric hypoxia.

Rabbits were acclimatized to simulated high altitude (SHA) (hypobaric hypoxia) at 6000 M (350 torr) on alternate days for 70 days. The norepinephrine levels of the midbrain were lower in the acclimatized animal compared to the controls (p less than 0.06) and 3,4 dihydroxyphenylacetic acid (DOPAC) was significantly higher (p less than 0.04) in the striatum of control than in the test animals. The mean dopamine (DA) levels in the striatum of the test animals were higher than the controls. The ratio of DOPAC/DA was 2.0 for the controls and 0.4 for the SHA brains which suggests reduced dopamine turnover in the striatum of the SHA rabbits. Rats acclimatized in the same manner did not show any difference in the NE or DA levels between the control and SHA animals, possibly the result of species differences.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1982

Differential activity of enantiomers of amphetamine in rats.

Administration of single doses of d-amphetamine (0.5-4.0 mg/kg i.p.) to adult, male rats produced the expected dose-related increases in spontaneous motor activity. This effect was reduced by pretreatment with alpha-methylparatyrosine (alpha MT) and virtually unaffected by pretreatment with pargyline or parachlorophenylalanine (PCPA). Single doses of l-amphetamine (0.25-8.0 mg/kg) evoked an initial decrease in activity followed by increased activity of smaller magnitude than that caused by the d-isomer. The depressant effects of the l-isomer were prolonged by pretreatment with alpha MT, and abolished by pretreatment with pargyline or PCPA.

Amphetamine↗
PubMed1981

Alterations in norepinephrine and dopamine content in selected brain areas of guinea pigs adapted to simulated high altitude.

The alterations in brain content of norepinephrine (NE) and dopamine (DA) were studied in guinea pigs adapted to simulated high altitude (hypobaric hypoxia) equivalent to 5500 meters. The animals were adapted for 46 days over a period of 82 days to a pressure of 375 mm Hg. The animals were then killed and the following brain parts dissected: cerebellum, neocortex, caudate head/basal forebrain, diencephalon/rhinencephalon, and brain stem. NE and DA content were analyzed by high pressure liquid chromatography with electrochemical detection by a technique described. Results showed a significant increase of NE and DA in neocortex; a significant increase of DA but not NE in caudate/basal forebrain, and a significant decrease of NE and not DA in diencephalon/rhinencephalon.

Acclimatization↗
PubMed1981

Elevation of serum and ventricular norepinephrine content in the diabetic rat.

Experimental diabetes was induced in rats by IV administration of 65 mg/kg streptozotocin. After 12 days, the rats were anesthetized with ether; the hearts were excise and perfusion washed. The atria and basilar portion of ventricle were freeze clamped, weighed and assayed for content of norepinephrine (NE), epinephrine (E) and dopamine (DA) using high pressure liquid chromatography with electrochemical detection. The serum concentration and adrenal content of NE, E and DA were also assayed. Results showed a significant increase in NE and DA in diabetic rat ventricles compared to control. The serum concentration of NE was significantly increased in diabetics while E showed no change.

Adrenal Glands↗
PubMed1979

Liberation of histamine by compound 48/80, tolazoline, betahistine and burimamide from isolated spontaneously beating guinea pig and rabbit atrial pairs.

Tolazoline, betahistine, burimamide and compound 48/80 release histamine from isolated guinea pig atria resulting in histamine concentrations that stimulate H2-receptors. Tolazoline, burimamide and 48/80 also release histamine from rabbit atria but do not result in histamine concentrations that will stimulate either H1- or H2-receptors. However, betahistine (which does not release histamine from rabbit atria) and tolazoline stimulate the rabbit atrial chronotropic response by releasing catecholamines.

Animals↗
PubMed1979

Depressive action of clonidine on guinea pig and rabbit atrial pairs.

The effects of clonidine, a compound used clinically as a centrally active antihypertensive, were studied on isolated, spontaneously beating atria of rabbit and guinea pig. In rabbit atria clonidine induces a marked depression of spontaneous chronotropic activity which was not altered by pretreatment with atropine, and not completely reversed by washing. In guinea pig atria, clonidine alone induces a very small increase in rate. A significant decrease in rate however is unmasked when tissues are pretreated with metiamide (H2-antagonist). Since both rabbit and guinea pig atria contain histamine receptors the lack of a positive chronotropic response in rabbit atria suggests that clonidine has no direct H2-receptor activity. The small positive response obtained with guinea pig atria which can be blocked by metiamide suggests that clonidine can act indirectly by releasing endogenous histamine stores from this tissue. Clonidines direct action appears to be a significant depression of both rabbit and guinea pig atrial chronotropic activity.

Animals↗
PubMedDate not supplied

Tolerance to ethanol-induced hypothermia in adult rats following postnatal ethanol exposure.

Rat pups of both genders were treated during the entire postnatal brain growth spurt (postnatal days 1-20) with ethanol (EE) utilizing an intragastric intubation technique. Two other groups of pups included isocaloric vehicle and handled control pups. Beginning on postnatal day 43 (TD1), and every seventh day subsequently (TD's 2, 3 and 4), the rats received an intraperitoneal dose of 2.2 g/kg ethanol. Their body temperatures were recorded at 0, 30, 60 and 90 minutes postinjection by use of a rectal probe. On the six days between measurements of ethanol-induced hypothermia, all rats were administered a daily dose of ethanol by intragastric intubation. Body growth of male and female pups was inhibited throughout the early treatment period. Body growth of adult females, but not males, was also depressed on TD's 1 and 2. Basal body temperature of EE male rats was selectively depressed at TD2, compared to the other groups. Although all groups showed tolerance to ethanol-induced hypothermia by TD2, there was a significant difference between males and females. Specifically, EE female rats showed a greater degree of tolerance when compared to EE males or control females.

Animals↗