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Biomedical subjects

B T Ho

Publications and source records attributed to B T Ho.

At least 55 records · Page 3Linked to original sources
PubMed1981

Depression, antidepressants, and plasma DBH.

Plasma levels of dopamine-beta-hydroxylase (DBH) were determined in 16 unmedicated patients with major depressive episodes (nonpsychotic) and in an equal number of normal subjects, before and after 4 weeks of treatment with tricyclic antidepressants. Some eight patients were treated with amitriptyline, and the remainder received desipramine. The controls remained medication free during the entire experimental period. Degrees of depression were quantified before and after treatment with the Hamilton Rating Scale of Depression (HRSD). There were no significant differences between the depressed patients and the controls on levels of DBH. Similarly, there were no within-group, pre-posttreatment differences on the enzyme levels in either group. Pre- and posttreatment HRSD scores did not correlate with corresponding plasma DBH levels. Plasma levels of amitriptyline, nortriptyline (product of amitriptyline in the body), and desipramine at the end of 4 weeks of treatment also failed to correlate with the enzyme levels.

Adult↗
PubMed1981

Periaqueductal gray neurons response to microiontophoretically injected morphine in naive and morphine-dependent rats.

The attempt of this study was to investigate the direct effects of increasing doses of morphine on the neuronal activity of the periaqueductal gray in morphine-naive and morphine-dependent rats. The microiontophoresis technique was used for this purpose. The four different responses induced by morphine exhibited dose-related patterns. Naloxone antagonized these responses in about 40% of the cases. Differences were found in the sensitivity of the neurons of morphine between naive and morphine-dependent rats. The phenomena of acute tolerance, chronic tolerance and dependence have been found. The results of this study indicate the presence of different neural populations in the periaqueductal gray in relation to their response to morphine, supporting the notion that subpopulations of opiate receptors exist within this brain area.

Animals↗
PubMed1981

Incidence of retinal detachments following extracapsular cataract extractions. A prospective study.

This is a preliminary report on a prospective study designed to determine the incidence of retinal detachment following planned extracapsular cataract extractions. The population consists of 454 eyes with a mean follow-up period of 23 months. The incidence of detachment is much lower than that reported for intracapsular extractions. The most significant finding to date is the importance of maintaining the posterior capsule and the vitreous face intact. The incidence of detachment when this is accomplished in normal eyes is 0.9%. The overall incidence of this complication in the entire series is 1.50%. The reported disadvantage of maintaining the posterior capsule is the 40% to 50% incidence of a secondary cataract. In this series, the incidence is 11%. The factors responsible for this low figure are enumerated.

Cataract Extraction↗
PubMed1981

Catecholamines and monoamine oxidase activity in anxiety.

Levels of platelet monamine oxidase activity, state anxiety and trait anxiety were quantified twice in 20 drug-free subjects with generalized anxiety and an equal number of healthy drug-free controls at 4-week intervals. Fifteen subjects in each groups also had plasma epinephrine and norepinephrine measured. The index group received relaxation training during the interval between the two evaluation sessions. Post-relaxation training values for monoamine oxidase, epinephrine, norepinephrine and the anxiety levels were found to be significantly lower than the pre-treatment values for the index group. No significant changes were seen in the control group values. For the index group, catecholamine levels and monoamine oxidase activity were seen to correlate significant before and after relaxation training.

Adult↗
PubMed1981

Human brain monoamine oxidase: one molecular entity-multiple binding sites?

Monoamine oxidase (MAO) of human brain cortex was partially characterized by using different substrates and inhibitors. Two Km values were calculated for each of the three substrates tested, i.e., phenethylamine (PEA) benzylamine (BA) and 5-hydroxtryptamine (5-HT). Clorgyline and 5-HT, both known as MAO-A occupants, were able to abolish the second (high) Km deamination of PEA. 5-HT, while non-competitively inhibiting the deamination of low BA concentrations, competitively inhibited the deamination of high concentrations of this type B substrate. The kinetics of 5-HT deamination showed positive cooperation which indicates the involvement of subunits in the enzyme structure. The ability of some phospholipids to change the enzyme behaviour was considered as indication that these molecules might play a role in determining the ratio between the so-called A and B types of MAO, and in the regulation of the enzyme's activity.

Binding Sites↗
PubMed1981

Anxiety and platelet MAO levels after relaxation training.

The authors measured platelet MAO activity with phenylethylamine and tryptamine substrates in a group of 20 subjects with chronic anxiety before and after they underwent relaxation training. Levels of anxiety were quantified using a self-rating scale. Posttreatment values for anxiety and enzyme activity were significantly lower than pretreatment values. Anxiety and enzyme activity levels were not significantly correlated at any stage of the study.

Adult↗
PubMed1980

The discriminative stimulus properties of 2,5-dimethoxy-4-methylamphetamine (DOM): differentiation from amphetamine.

Rats were trained in a two-lever operant procedure to discriminate either 1.0 mg/kg (+)amphetamine or 1.5 mg/kg DOM from saline. Rats trained to discriminate DOM from saline showed generalization with the DOM training condition when tested with mescaline or 2,5-dimethoxy-4-ethylamphetamine (DOET), but not when tested with (+)amphetamine or methylphenidate. Both isomers of DOM generalized with racemic training compound, the (-)isomer being more potent. The DOM stimulus was completely blocked by the serotonin (5-HT) antagonists cinanserin and methysergide, but not by the peripheral 5-HT antagonist xylamidine nor the dopamine antagonist haloperidol. Rats trained to discriminate (+)amphetamine from saline generalized with the amphetamine training condition when tested with methylphenidate but not when tested with mescaline, DOET, racemic DOM, or either isomer of DOM. The amphetamine stimulus was blocked by pretreatment with haloperidol but not by cinanserin, methysergide, or xylamidine. The results show that, despite their structural similarity, amphetamine and DOM induce pharmacologically distinct stimuli.

DOM 2,5-Dimethoxy-4-Methylamphetamine↗
PubMed1980

Effects of acute and chronic administration of phencyclidine on tyrosine hydroxylase activity in rat striatum.

Following a single dose of phencyclidine (PCP) striatal tyrosine hydroxylase (TH) activity was decreased 42% 15 min after PCP administration, but returned toward baseline levels by 45 min post-drug. Twenty-four hours after the 30th dose of PCP, TH activity remained depressed when compared to the chronic slaine controls. TH activity was not further depressed 15 or 45 min after the 31st dose of PCP.

Animals↗
PubMed1980

Amphetamine discrimination: onset of the stimulus.

Rats were trained to discriminate 1.0 mg/kg (+)-amphetamine sulfate from saline in a two-lever operant procedure. The normal injection-to-session interval was fifteen minutes. When tested with amphetamine immediately after intraperitoneal injection, rats initially responded on the lever paired with saline in training, but quickly shifted to the lever paired with amphetamine in training. When tested with saline immediately after immediately after injection, animals responded appropriately for the saline treatment throughout the extinction test. The results show that (+)-amphetamine exerts discriminative response control within five minutes of intraperitioneal injection.

Animals↗
PubMed1980

Catechol-O-methyltransferase and catecholamines in anxiety and relaxation.

Levels of anxiety, plasma epinephrine and norpinephrine, and red blood cell (RBC) catechol-O-methyltransferase (COMT) activity were measured before and after 4 weeks of relaxation training in a group of 15 drug-free, anxious subjects and at a similar interval in a group of 15 drug-free, healthy controls. The index group showed significant decreases in levels of anxiety and plasma epinephrine and norepinephrine after treatment. No changes were observed in the control values. RBC COMT did not show any significant differences in activity between the index and control groups and between the pre- and posttreatment values. Similarly, COMT activity levels failed to correlate with levels of anxiety and catecholamines before or after treatment. These findings indicate that anxiety is unlikely to have an effect on RBC COMT activity, whereas it has a direct effect on plasma catecholamines.

Adult↗
PubMed1980

MAO, DBH and COMT: the effect of anxiety.

Anxiety, a common accompaniment of depression, can be a source of confusion in affective disorder research. The present study examined the effect of anxiety on platelet monoamine oxidase, RBC catechol-0-methyltransferase, and serum dopamine-beta-hydroxylase-enzymes frequently implicated in affective disorders. Levels of anxiety, plasma catecholamines and the enzymes mentioned above were quantified in groups of anxious subjects and mentally and physically healthy controls. Anxious subjects were found to have significantly higher levels of blood plasma catecholamines and platelet monoamine oxidase. significant positive correlations were demonstrated between plasma catecholamines and platelet monoamine oxidase, while significant inverse correlations were found between trait anxiety and COMT, norepinephrine and DBH, and COMT and DBH

Adult↗