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Biomedical subjects

R C Frecker

Publications and source records attributed to R C Frecker.

At least 19 recordsLinked to original sources
PubMed1993

Lack of effect of cimetidine on cigarette smoking.

The efficacy of cimetidine as a treatment that could reduce smoking in heavily dependent smokers has been determined. In a randomised, double-blind, double-crossover experiment, 43 heavy smokers were divided into two groups, one receiving cimetidine 400 mg orally three times a day, and the other receiving placebo for two weeks followed by the alternative treatment (placebo or cimetidine). No significant difference in the mean alveolar carbon monoxide, nicotine or cotinine levels was found between the two treatment groups compared to baseline. Since the alveolar carbon monoxide level reflects the intensity of smoking behaviour, the results suggest that no change in smoking behaviour occurred in the subjects. Contrary to our previous findings that cimetidine decreased the total body clearance of nicotine by 30% in a population of non-smokers, in the heavily dependent smokers, cimetidine did not appear to alter nicotine elimination. One possible explanation for the discrepancy is that tobacco smoking is known to induce nicotine metabolism and the induction might have offset any effect of cimetidine on nicotine elimination. Cimetidine does not appear to be a useful treatment leading to a reduction or cessation of cigarette smoking.

Carbon Monoxide↗
PubMed1991

Development and evaluation of two automated methods for quantifying human muscle sympathetic nerve activity.

The microneurographic technique of directly recording muscle sympathetic nerve activity (SNA) in conscious humans was developed over 20 yr ago, but analysis and quantification of the resultant mean voltage neurogram has been largely by visual inspection by a trained observer. Two computer-assisted methods were developed to quantitate these bursts of efferent activity: peak detection, and ECG R-wave-triggered burst averaging. Peak detection was optimized using statistical techniques; burst averaging was compared to both the manual technique and to the peak detection method. Burst averaging was found to be the superior method because of its speed, consistency, and objectivity.

Action Potentials↗
PubMed1991

The Fagerström Test for Nicotine Dependence: a revision of the Fagerström Tolerance Questionnaire.

We examine and refine the Fagerström Tolerance Questionnaire (FTQ: Fagerström, 1978). The relation between each FTQ item and biochemical measures of heaviness of smoking was examined in 254 smokers. We found that the nicotine rating item and the inhalation item were unrelated to any of our biochemical measures and these two items were primary contributors to psychometric deficiencies in the FTQ. We also found that a revised scoring of time to the first cigarette of the day (TTF) and number of cigarettes smoked per day (CPD) improved the scale. We present a revision of the FTQ: the Fagerström Test for Nicotine Dependence (FTND).

Adolescent↗
PubMed1990

Effect of cimetidine and ranitidine on the hepatic and renal elimination of nicotine in humans.

In a randomized, double-blind, cross-over experiment, 6 healthy consenting male subjects were administered cimetidine 600 mg or ranitidine 300 mg or placebo p.o. q12h x 2 days. Nicotine bitartrate was administered i.v. on day 2 (1 microgram/kg/min) x 30 min. After cimetidine mean nicotine total and metabolic clearances were decreased by 30% and 27% while after ranitidine the clearances were decreased by 10% and 7% respectively. Since smokers regulate their smoke intake based in large part on their nicotine blood levels these results suggest that the diminished nicotine total clearance in the presence of cimetidine could be important in assisting smoking reduction or cessation.

Adult↗
PubMed1990

End-point nystagmus and ocular drift: an experimental and theoretical study.

End-point nystagmus (EPN) and ocular drift during eccentric fixation were investigated in five normal subjects. All had EPN during prolonged eccentric fixation, two had sustained EPN within a few seconds of fixating an eccentric target. Our data show that the occurrence of EPN was determined by the velocity of slow phase ocular drift. Drift velocities greater than 1 deg/sec elicited sustained EPN or fatigue EPN while drift velocities lower than 0.3 deg/sec did not elicit EPN. Slow phase drift velocity increased with eccentricity and fixation duration and decreased with visual feedback. Computer simulations and theoretical analysis suggest that the reduction in drift eye movement velocity during fixation of a visible target, as compared to drift eye movement velocity during attempted fixation of a remembered target in darkness, is mainly due to the smooth pursuit system.

Adult↗
PubMed1989

Self-selected blocking of vents on low-yield cigarettes.

Blockers of vents in ultra-low-yield cigarettes had higher levels of carbon monoxide (CO) and salivary cotinine than did nonblockers. None of the blockers reported that they blocked vents. Exposure differences seemed not to be due simply to vent blocking, but also to be the result of syndromes of heavier (blocking, more cigarettes per day, and starting earlier in the morning) or lighter smoking (not blocking, fewer cigarettes per day, and starting later in the morning). The results are interpreted in light of the boundary model. Cigarette smoking and brand selection should be studied as they occur naturally, as well as in experimentally contrived studies.

Adult↗
PubMed1989

Measuring the heaviness of smoking: using self-reported time to the first cigarette of the day and number of cigarettes smoked per day.

Two simple self-report measures have been used to assess the heaviness of smoking, 'number of cigarettes per day' (CPD) and 'time to the first cigarette of the day' (TTF). Little attention, however, has been given to the precise method of scoring this information. Using biochemical indicators of heaviness of smoking (alveolar carbon monoxide and cotinine), we explore the optimum data transformations for regression analysis and categorical analysis. We suggest a four category scoring scheme for both time to the first cigarette of the day (less than or equal to 5, 6-30, 31-60 and 61+ min) and average daily consumption of cigarettes (1-10, 11-20, 21-30, 31+ cigarettes) as the most powerful and practical categorical scoring of these variables. Due to possible ceiling effects on biochemical measures, we suggest using logarithmic transformations of CPD or TTF for regression or correlation analyses.

Adolescent↗
PubMed1985

Power spectra for ocular drift and tremor.

Eye position during fixation has been measured without contact and the power spectrum of drift and tremor eye movements has been estimated. In the 0-40 Hz frequency range power declines with frequency roughly as 1/f2. In the 40-100 Hz frequency range the dominant spectral component is a broad spectral peak with a peak amplitude of about 6 arc sec. The shape of the broad spectral peak is dependent on the fixation direction. A model that explains qualitatively the shape of the power spectra function is presented. It is suggested that tremor eye movements are by-products of the clock-like firing of motor neurons.

Eye Movements↗
PubMed1984

Precise non-contacting measurement of eye movements using the corneal reflex.

Using a real-time, analog, zero-crossing technique, it is possible to locate the centre of the corneal reflex of a collimated infra-red beam accurately. Performance at tracking horizontal eye movements in this manner is similar to contact lens techniques. System noise is less than 30 are sec; dynamic range is 30 arc sec to 36 deg; linearity is 2%; data are currently sampled at 1 kHz; velocity resolution, for a velocity bandwidth of 125 Hz, is 2 deg/sec. With automatic acquisition of the corneal reflex, the subject can be set up for measurement within a 1 min time period. Recordings of residual eye movements of fixation and of a wide range of saccades are comparable with previous findings. Post-saccadic oscillations can be resolved for all sizes of saccades. The amplitude-peak-velocity characteristic of saccades is illustrated.

Blinking↗