Biomedical subjects

H C Sing

Publications and source records attributed to H C Sing.

16 recordsLinked to original sources

PubMed1993

Effects of catecholamine depletion on alertness and mood in rested and sleep deprived normal volunteers.

Alpha-methyl-para-tyrosine (AMPT), a tyrosine hydroxylase inhibitor, was used to evaluate the physiologic role of central nervous system catecholamines in modulating alertness and mood. Forty healthy males were randomized to one of four conditions: AMPT in a rested condition; AMPT plus 40.5 hours of total sleep deprivation; placebo plus sleep deprivation; or placebo in a rested condition. Repeated measures of alertness and mood revealed that treatment with AMPT or sleep deprivation increased sleepiness, and combined treatment produced greater sleepiness than either treatment alone. In contrast, although combined treatment with AMPT and sleep deprivation led to large increases in negative mood, neither treatment alone produced consistent mood changes. These findings are consistent with the view that sleep deprivation is associated with decreased functional catecholamine neurotransmission. Furthermore, mood effects following sleep deprivation plus AMPT suggest that catecholamines may be involved in mood changes during sleep deprivation.

Adult↗

PubMed1992

Selected problems of analysis and interpretation of the effects of sleep deprivation on temperature and performance rhythms.

One of the major methodological-analytic problems encountered by researchers in sleep deprivation involves the examination and analysis of the relationship between sleep loss and rhythmic influences on performance. The comparison of performance rhythms with physiological rhythms, e.g., body temperature, generated under the same conditions of sleep deprivation, has become an important means of testing for an endogenous source of the rhythmicity in the data and for clarifying the nature of the proposed oscillator system. Should the data sets be correlated before or after their separation into monotonic and rhythmic parts? Correlating the raw data without separating them into their components can yield negative results, while, in reality, some of the major underlying rhythms may be highly related. The example used in this chapter showed strong cross correlations of the circadian components of temperature and two performance tasks. Sleep deprivation is thus seen to interact with performance rhythms. This interaction is only revealed after the data are analyzed and broken into their component parts. This procedure leads to the conclusion that certain performance rhythms and temperature may share the same generating oscillators.

Body Temperature↗

PubMed1992

Sleep deprivation and impaired cognition. Possible role of brain catecholamines.

To assess the role of brain catecholamines in cognitive decline associated with sleep deprivation, 40 healthy male volunteers were randomized to conditions of total sleep deprivation or 40.5 h of rest. Within each sleep condition, subjects were further randomized to treatment with a 2-day regimen of placebo or alpha-methyl-para-tyrosine (AMPT), a catecholamine synthesis inhibitor. Cognitive performance was measured repeatedly over time using a computerized performance assessment battery. Treatment with AMPT or treatment with sleep deprivation increased sleepiness without producing marked or consistent deterioration in performance. By contrast, subjects who received both treatments reported greater sleepiness than those receiving either treatment alone, and developed severe cognitive impairment on a variety of tasks. These findings, along with previous evidence that catecholamine-enhancing drugs improve performance in sleep-deprived individuals, support the view that decline in cognitive performance during sleep deprivation may be mediated by brain catecholamines.

Adult↗

PubMed1991

Monotonic and rhythmic influences: a challenge for sleep deprivation research.

There are both monotonic and rhythmic factors in the patterns of change seen in physiological, psychological, and performance variables during sleep deprivation. These monotonic and rhythmic factors can be orthogonal, or they may interact with each other, with various task variables, or both. The importance of separating the rhythmic from the monotonic factors and of elucidating their interactions is discussed. Experimental methods and types of analysis appropriate to evaluating these factors are examined, with special emphasis on the complex demodulation time series analysis applied to group or individual subject data. The discussion is accompanied by data illustrations. It is suggested that sleep deprivation research should be designed so as to generate physiological and behavioral data that include information on both monotonic and rhythmic factors, the nature and extent of their interaction, and how they interrelate with systematically manipulated independent variables.

Arousal↗

PubMed1991

Identification and characterization of greater mood variance in depression.

OBJECTIVE: The authors sought to assess the quantity and quality of mood variation in depressed persons. METHOD: Using a visual analogue scale, they compared variation of mood in a group of patients (N = 9) with a DSM-III-R diagnosis of depressive disorder and in a group of nondepressed subjects (N = 9) over 12 consecutive hours. To quantify mood variation for each subject, the authors computed the standard deviation of each subject's 13 mood ratings on the visual analogue scale. To characterize the quality of mood variation within each subject, they plotted each subject's mood ratings as a function of time and applied complex demodulation to confirm cyclical patterns of mood variability (ultradian cycles). RESULTS: The depressed group demonstrated greater mood score variability over the course of the day. Both groups demonstrated ultradian cycles and circadian trends; however, the depressed group demonstrated ultradian cycles of significantly greater amplitude than the nondepressed group. CONCLUSIONS: Repeated assessments of mood at different times of the day may be necessary to obtain an accurate impression of a patient's mood state. Further, the mechanism of depressive disorders may include a deregulation of a normal oscillatory mood variation pattern.

Activity Cycles↗

PubMed1989

The effects of d-amphetamine on arousal, cognition, and mood after prolonged total sleep deprivation.

Thirty-six normal male subjects underwent total sleep deprivation for 48 hours, were then administered either placebo, 5, 10, or 20 mg of d-amphetamine, and sleep deprived for an additional 12 hours. Sleep deprivation produced a significant reduction in sleep latency, as well as marked decrements in cognitive performance and self-ratings reflecting vigor and fatigue. Amphetamine reversed these effects in a dose-related way but the pattern and persistence of the reversal varied across measures. After 20 mg, sleep latency normalized for several hours, but then declined. Behavioral effects tended to follow the pattern of sleep latency. On cognitive tasks, 20 mg produced a sustained return to normal performance in an attentional arithmetic task and a gradual improvement in a verbal reasoning task. The partial temporal dissociation among sleep latency, behavioral, and cognitive effects suggests that varying doses of amphetamine may have time-related differential neurochemical effects or that various dimensions of arousal and alertness may be differentially sensitive to amphetamine.

Adult↗

PubMed1989

Perceptual distortions and hallucinations reported during the course of sleep deprivation.

Subjects worked 30 to 45 min. of each hour for either 48 (n = 2) or 72 hr. (n = 8) without sleep. The frequency of reported visual task-related perceptual distortions and hallucinations showed both a linear increasing component and a strong circadian component. Perceptual distortions were most frequent in the late night-early morning hours (0400) and least frequent in the late afternoon-early evening hours (1600-2000).

Adolescent↗

PubMed1977

Determination of "true" serum creatinine by high-performance liquid chromatography combined with a continuous-flow microanalyzer.

We coupled a high-performance liquid chromatograph with a continuous-flow microanalyzer to produce a system for specifically determinig "true" creatinine in urine and serum specimens. A selective microbore pellicular cation-exchange column and a single eluting sodium citrate buffer are used to separate the noncreatinine but Jaffé-positive constituents from the creatinine in normal and experimental specimens. The effluent is analyzed continuously, on-line, the alkaline picrate complex being developed and measured in the microanalyzer. Physiological samples, reference standards, and internal control specimens are assayed in 6-min intervals subsequent to the initial injection. The relationship between concentration and peak are is linear for creatinine standards between 5 and 10 mg/liter. Specimen volumes ranging from 1 to 25 microliters, and containing creatinine in amounts exceeding 5 ng per injected sample, can be assayed with this system.

Chromatography, High Pressure Liquid↗

PubMed1975