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Biomedical subjects

D T Greenwood

Publications and source records attributed to D T Greenwood.

18 recordsLinked to original sources
PubMed1992

Changes in wealth in the United States, 1962-1983: savings, capital gains, inheritance, and lifetime transfers.

"A simulation model is developed to account for observed changes in mean household wealth both overall and by age cohort over the 1962-1983 period in the United States. There are three major findings. First, capital gains are the major factor explaining overall wealth changes and account for 77% of the simulated growth in wealth over the entire period. Second, for cohorts under age 40, inheritance and inter vivos transfers dominate observed changes in wealth....Third, while differences in portfolio composition favored the younger cohorts over this period, such differences do not explain a large portion of the great variation in real wealth changes by cohort over the two decade period."

Age Factors↗
PubMed1990

Effects of beta 1- and beta 2-blockade on blood pressure and sympathetic responses to flight phobia stress.

Cardiovascular and sympathoadrenal effects of short-term oral treatment with beta 1-blockade (atenolol, 50 mg, administered two times) and beta 2-blockade (ICI 118,551, 50 mg, administered three times) were compared with placebo during actual flying in subjects with flight phobia (n = 34). beta 1-Blockade lowered resting blood pressure and heart rate and prevented a heart rate response but not a blood pressure response to this psychologic stress. beta 2-Blockade minimally lowered resting heart rate and prevented a heart rate response, but it failed to lower resting blood pressure or blood pressure response to the stress. Plasma epinephrine increased with all three treatments and more with beta 1-blockade than with placebo. Plasma norepinephrine decreased with administration of beta 2-blockade. Thus neither beta 1- nor beta 2-blockade prevents an increase in blood pressure during acute flight phobia stress. Increased plasma epinephrine seems to be the sympathetic variable that is closest related to this increase in blood pressure. Norepinephrine may be less consistently related to the blood pressure rise during flight phobia stress as shown by the decrease in plasma norepinephrine with administration of beta 2-blockade.

Administration, Oral↗
PubMed1990

Correlations between psychological and physiological responses to acute flight phobia stress.

Exposure of phobic subjects to real-life psychological stress may induce a high level of anxiety and be better than laboratory experiments for studies of physiological responses to psychological stress in human research. Therefore, by introducing natural psychological stress, i.e. actual flying in subjects with flight phobia (n = 23), the present study aimed at testing the hypothesis that there is, during mental stress, a direct relationship between the level of anxiety and the responses in the physiological variables blood pressure, heart rate and plasma catecholamines. Plasma adrenaline, heart rate, blood pressure and perceived anxiety measured by three different scales increased highly significantly during flight whereas plasma noradrenaline did not change. No direct relationship was found between the physiological and psychological variables. Thus, the physiological responses to natural psychological stress in terms of phobic anxiety may be definite, but the way the responses are related is less clear.

Adult↗
PubMed1982

Anticonvulsant and proconvulsant properties of viloxazine hydrochloride: pharmacological and pharmacokinetic studies in rodents and the epileptic baboon.

Viloxazine HCl is evaluated as an anticonvulsant in a wide range of rodent seizure models and in the epileptic baboon (Papio papio). In the maximal electroshock test, the oral ED50 for abolition of tonic extension was 9 mg/kg-1 after 30-min pretreatment (mouse) rising to 30 mg/kg-1 after 60 min (mouse and rat). Comparable ED50 values were also found for protection against tonic extension in the mouse induced by the administration of the chemical convulsants metrazole or 3-mercaptopropionic acid. In DBA/2 mice the ED50 for abolition of tonic extension during sound-induced seizures was 6.8 mg/kg-1 IP (30-min pretreatment). Pharmacokinetic studies in the mouse showed peak plasma levels to occur 30 min following oral doses, with a mean half-life of 58 min. The anticonvulsant plasma concentration was within 0.5 -- 1 microgram/ml-1. In the baboon, significant protection against photomyoclonic responses is observed 1 -- 2h after viloxazine (2.6 mg/kg-1 IV), during which period the plasma concentration was again 0.5-1 microgram/ml-1. After administration of approximately ten-times this latter dose level, i.e. 24 mg/kg-1 IV, a syndrome characterised by an abnormal EEG and, in some instances, seizure activity was observed.

Acoustic Stimulation↗
PubMed1982

Stereospecificity of behavioural effects of viloxazine in bulbectomized rats does not correlate with its 5-HT-releasing action in vitro.

The effects of the antidepressant drug viloxazine and its two optically active isomers on the passive avoidance learning deficit surgically induced in rats by bilateral bulbectomy have been determined. Fourteen consecutive daily injections of either the racemate or the S-isomer (2, 5 and 10 mg kg-1 i.p.) significantly improved the acquisition of avoidance behaviour. The R-isomer was devoid of such activity in this same dose range. The various isomeric species of viloxazine were also studied in vitro for their ability to induce a release of noradrenaline, dopamine and 5-hydroxytryptamine (5-HT) from rat brain slices. In agreement with previous reports, racemic viloxazine caused a concentration-dependent (10(-5)-10(-3 M) release of 5-MT without affecting any significant change in the release of either catecholamine. However, in contrast to the results of the behavioural studies, this phenomenon did not exhibit stereospecificity, all three isomeric forms being equally active. Thus, there is no simple relationship between viloxazine's behavioural activity in bulbectomized rats and its 5-HT releasing properties observed in vitro. The significance of these findings with respect to previously reported effects of the drug indicative of facilitation of central 5-HT mediated processes is discussed.

Animals↗
PubMed1979

A reward-reduction model of depression using self stimulating rats: an appraisal.

A potential model of depression using a "reward reduction" technique with intracranial self-stimulation (ICSS) has been suggested. A number of rats with electrodes chronically implanted in the medial forebrain bundle were trained on this paradigm. The model involved the use of progressively increasing fixed ratio (IFR) schedules. Two tricyclic antidepressants, imipramine and protriptyline, were administered. Neither of these drugs resulted in the response enhancement which had been predicted. Only d-amphetamine (0.5 mg/kg) produced the predicted "antidepressant" action. It was concluded that response instability made this test difficult to operate and that even animals with adequately stable baselines did not produce a response pattern which could be categorised as specifically antidepressant.

Amphetamine↗
PubMed1978

Effects of viloxazine, its optical isomers and its major metabolites on biogenic amine uptake mechanisms in vitro and in vivo.

Viloxazine hydrochloride (ICI 58,834, VIVALAN) a chemically novel antidepressant, shows selective inhibition of noradrenaline uptake into mouse heart in vivo and into rat brain in vitro. The noradrenaline uptake inhibitory activity resides primarily in one of the two optically active isomers, and it is suggested that in the conformation adopted for uptake by noradrenaline, the aryl and the amino groups are trans. In a comparison of in vivo and in vitro potency, tri- and tetracyclic antidepressants exhibit a good correlation. However, viloxazine possesses higher in vivo activity than would be expected from in vitro studies. The latter finding cannot be readily explained on the basis of known pharmacokinetic or metabolic factors.

Animals↗
PubMed1975

2-Aryloxymethyl-2,3,5,6-tetrahydro-1,4-oxazines, a new class of antidepressants.

Some 2-aryloxymethyl-2,3,5,6-tetrahydro-1,4-oxazines have been shown to possess marked antidepressant activity. The 1,4-oxazines were synthesized by lithium aluminum hydride reduction of the readily available 6-aryloxymethyl-2,3,5,6-tetrahydro-1,4-oxazin-3-ones. High antidepressant activity was associated with ortho substitution of the 2-phenoxymethyl group and with 1,4-oxazines devoid of 4-substituents.

Animals↗