A test of generalizability of cardiovascular reactivity using a controlled ambulatory procedure.

This study tested the hypothesis that reports of poor generalizability of cardiovascular reactivity measured in the laboratory to changes observed during everyday life are due to a lack of standardization of activities and position (sitting, standing) in the latter situation. Thirty-seven subjects engaged in reactivity testing, and then in a 4-hour series of standardized activities outside the laboratory (controlled ambulatory phase), accompanied by the experimenter, on each of 2 days. The controlled ambulatory activities included alphabetizing, an editing task, a brisk walk, solving word puzzles, and eating lunch. Two measures of field variability were examined: the standard deviation and the root mean square of successive differences, of all ambulatory measurements. Associations between laboratory changes scores and measures of field variability were poor (highest r = .23). We conclude that evidence for generalizability of reactivity change scores remains poor, and cannot be solely attributed to the uncontrolled nature of activities in the field.

A test of reproducibility of blood pressure and heart rate variability using a controlled ambulatory procedure.

OBJECTIVE: To determine whether the previously reported poor reproducibility of blood pressure variability measured by ambulatory blood pressure monitoring (ABPM) is due to the uncontrolled nature of physical and mental activity during the monitoring period. DESIGN: ABPM was performed on two separate days during which subjects performed identical activities, accompanied by the experimenter. Thus, activity and posture were controlled, both within and between subjects. Two measures of variability were used: SD and the root-mean-square of successive differences (RMSSD). METHODS: Thirty-seven subjects participated. Each engaged in a series of activities, such as walking outdoors, editing and alphabetizing tasks, and eating lunch, while wearing an A & D 2420 ambulatory blood pressure monitor which took measurements at 5-min intervals. Measures of variability were computed within each session. RESULTS: Contrary to previous reports, reproducibility was moderately high for blood pressure, with significant correlations between SD and between RMSSD for systolic and diastolic blood pressure. Heart rate reproducibility was less good. CONCLUSIONS: Lack of standardization of activities from one occasion to another is a major reason for the poor reproducibility of blood pressure variability when measured using ABPM. Even when activities are standardized, however, the reproducibility of blood pressure variability is still only moderate and may limit the ability of researchers to detect associations between ABPM variability and other measures.

Efficacy of brief, intense light exposure for treatment of winter depression.

A high-intensity fluorescent lighting system, tilted downward toward the head, and emitting negligible levels of ultraviolet radiation, was tested under two random crossover protocols in winter-depressed patients: 30-minute sessions at (a) 3,000 lux vs. 10,000 lux in early morning, and (b) morning vs. evening sessions at 10,000 lux. Judgment of clinical remission was based jointly on relative and absolute score improvements on a Structured Interview Guide for the Hamilton Depression Scale--Seasonal Affective Disorder Version (SIGH-SAD) and a set of supplementary atypical-vegetative items. Data are presented for 24 subjects who showed relapse upon withdrawal. An overall remission rate of 75 percent was found for morning light at 10,000 lux. The rates for evening light (25%) and 3,000 lux morning light (19%) were significantly lower. The remission rate for morning light treatment of 10,000 lux for 30 minutes approximately equalled 2,500 lux treatment for 2 hours (data from our earlier studies), suggesting a reciprocity between dosing dimensions of intensity and duration. No pathological changes were revealed by ophthalmological examinations given after 2 to 6 weeks of daily treatment.

Phenylpropanolamine and amphetamine disrupt postprandial satiety in rats.

Two tests of the behavioral specificity of the anorectic effects of amphetamine (AM) and phenylpropanolamine (PPA) were done. Intraperitoneal injections of each drug reduced the size of condensed milk test meals in 30-min pellet-deprived rats. The dose-response relations in semi-log coordinates were linear and parallel, but AM (ED50, 2.0 +/- 0.1 mumol/kg) was about ten times more potent than PPA (ED50, 24.6 +/- 0.1 mumol/kg). Periprandial behaviors were observed using a time-sampling technique. Both AM and PPA disrupted the normal behavioral sequence of postprandial satiety throughout their anorectic ranges, but they did so differently. AM increased postprandial exploratory behavior, decreased or eliminated resting, and, at larger doses, elicited stereotypy. In contrast, PPA inhibited both grooming and exploration, and increased resting. The drugs' effects on water intake were tested in 17-hr water-deprived rats. AM's adipsic effect (ED50, 2.3 +/- 0.1 mumol/kg) was similar to its anorectic effect. PPA also inhibited drinking, although slightly less potently (ED50, 56.6 +/- 0.1 mumol/kg) than it did feeding. Thus, under conditions maximizing the anorectic potencies of systemically administered AM and PPA in rats, both drugs inhibited feeding nonspecifically rather than by eliciting normal postprandial satiety.

Combined injection potentiates the satiety effects of pancreatic glucagon, cholecystokinin, and bombesin.

Pancreatic glucagon (PG), cholecystokinin (CCK), and bombesin (BBS) were injected individually and in combination before nondeprived rats were offered condensed milk test meals. Peptide doses that were individually below the threshold for reliable inhibition of meal size (0.15 microgram/kg CCK, 0.75 microgram/kg BBS, 100 micrograms/kg PG) combined to inhibit meal size 19-40%. The inhibitions produced by combinations including CCK were 16-21% more than the sum of the inhibitions elicited by individual injections. This indicates a potentiation of inhibition. In contrast, when peptide doses were increased, the inhibitory effects of the combinations were similar to the sum of the individual injections. None of the peptide treatments disrupted the normal behavioral sequence of postprandial satiety, and they did not reliably affect water intake in water-deprived rats. We conclude that exogenous CCK, BBS, and PG can interact to potentiate postprandial satiety.