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Biomedical subjects

F M Sulzman

Publications and source records attributed to F M Sulzman.

At least 19 recordsLinked to original sources
PubMed1996

Life sciences space missions. Overview.

It has been known for many years that weightlessness induces changes in numerous physiological systems: the cardiovascular system declines in both aerobic capacity and orthostatic tolerance; there is a reduction in fluid and electrolyte balance, hematocrit, and certain immune parameters; bone and muscle mass and strength are reduced; various neurological responses include space motion sickness and posture and gate alterations. These responses are caused by the hypokinesia of weightlessness, the cephalic fluid shift, the unloading of the vestibular system, stress, and the altered temporal environment.

Animals↗
PubMed1995

Alterations in growth rate associated with a normally persisting circadian rhythm during spaceflight.

BACKGROUND: Biological clocks time many physiological parameters with periodicities close to 24 h; those which persist in the absence of environmental cues are circadian. An earlier shuttle experiment (STS-9) examined circadian pacemaker function and growth rate of Neurospora crassa and demonstrated damped rhythm amplitudes, increased variability in period lengths and altered growth rates. HYPOTHESIS: Postflight studies suggested that accelerative forces of launch could have induced rhythm alterations. Differences in growth rate may have been due to an alteration of metabolic rate. METHODS: Race tubes inoculated with bd or csp strains were flown aboard STS-32, exposed to ambient mid-deck temperatures throughout flight, and exposed to light only during marking procedures. Period, rhythm amplitude, and growth rate were determined and compared to orbital environmental controls (OES) and 25 degrees C ground controls (GC). RESULTS: Unlike the previous flight exposurement, the rhythm persisted quite normally. bd flight and OES cultures each displayed lengthened periods of a similar magnitude when compared to GC. The lengthened periods of csp flight cultures while longer than GC, were shorter than OES. Shuttle temperatures were relatively warm, however the increased period length in space was greater than predicted by the known Q10. Growth rates also increased substantially during flight, which could not be accounted for by thermal mechanisms alone. CONCLUSION: It is likely that some of the cultures may have entrained to the unexpected diurnal temperature variations; however, other cultures did not entrain, yet retained rhythmicity with increased periods. The results also suggest an increased metabolic rate during spaceflight.

Circadian Rhythm↗
PubMed1993

Effects of spaceflight on the musculoskeletal system: NIH and NASA future directions.

Prolonged bed rest, undertaken by volunteers or resulting from injury and disease, can impair bone and muscle function and structure; extended travel in space also induces these effects. Fluid shifts and disrupted fluid balance may also contribute to observed musculoskeletal aberrations in the weightless environment. Some molecular and cellular events involved in the loading and unloading of the musculoskeletal system are under neural and endocrine influence or control, whereas other events are influenced by local growth factors. Studies are in progress to develop interventions that preserve or improve musculoskeletal integrity in 1g. The NIAMS and NASA are interested in basic and clinical studies of the influence of microgravity on the musculoskeletal system. The interagency workshop results form the basis for new collaborative and cooperative research emphases for the biomedical community under a broad agreement between the National Institutes of Health and NASA.

Bone and Bones↗
PubMed1992

Thermoregulatory responses of rhesus monkeys during spaceflight.

This study examines the activity, axillary temperature (T(ax)), and ankle skin temperature (Tsk) of two male Rhesus monkeys exposed to microgravity in space. The animals were flown on a Soviet biosatellite mission (COSMOS 1514). Measurements on the flight animals, as well as synchronous flight controls, were performed in the Soviet Union. Additional control studies were performed in the United States to examine the possible role of metabolic heat production in the T(ax) response observed during the spaceflight. All monkeys were exposed to a 24-h light-dark cycle (LD 16:8) throughout these studies. During weightlessness, T(ax) in both flight animals was lower than on earth. The largest difference (0.75 degree C) occurred during the night. There was a reduction in mean heart rate and Tsk during flight. This suggests a reduction in both heat loss and metabolic rate during spaceflight. Although the circadian rhythms in all variables were present during flight, some differences were noted. For example, the amplitude of the rhythms in Tsk and activity were attenuated. Furthermore, the T(ax) and activity rhythms did not have precise 24.0 hour periods and may have been externally desynchronized from the 24-h LD cycle. These data suggest a weakening of the coupling between the internal circadian pacemaker and the external LD synchronizer.

Animals↗
PubMed1990

Nocturnal illumination does not necessarily stimulate the photoperiodic response, despite mimicking the effects of constant light on the circadian system in the male Syrian hamster.

In an effort to determine the inductive component(s) of photic input in long day seasonal breeders, adult male Syrian hamsters (Mesocricetus auratus) were exposed to one of nine lighting conditions for a duration of 10 weeks: a light-dark cycle of 14 hours of light followed by 10 hours of dark (LD 14:10, a long photoperiod); LD 10:14 (a short photoperiod); a high frequency light-dark cycle of 1 hour of light and 1 hour of dark (LD 1:1); a higher frequency light-dark cycle of 1 minute of light and 1 minute of dark (LD 1m:1m); constant light (LL); constant dark (DD); feedback lighting (LDFB; a condition that illuminates the cage in response to locomotor activity); a feedback lighting neighbor control (LDFB NC; the animal receives the same light pattern as a paired animal in LDFB, but has no control over it); or reverse feedback lighting (rLDFB; a condition that darkens an illuminated cage in response to locomotor activity). Exposure to LL, LD 1:1, LD 1m:1m, LDFB and rLDFB significantly and similarly lengthened the free-running period of the locomotor rhythm when compared to the period of animals in DD. The paired tests and accessory reproductive glands weights, spermiogenesis, seminiferous tubule diameter and serum concentrations of testosterone, prolactin, LH and FSH, suggest that LD 14:10, LL, LD 1:1, rLDFB and LDFB NC maintain reproductive function in the Syrian hamster, while LD 10:14, DD, LD 1m:1m and LDFB do not. It is known that as little as two 1-second pulses of light are stimulatory if coincident with the subjective night (17.22). Thus, it is not surprising that LD 1:1 is stimulatory. LD 1m:1m is not stimulatory, however, despite an identical quanta of light per 24 hours and similar phase relationship. It appears that mere light exposure during the subjective night is not necessarily reproductively inductive. It would also appear that behaviorally generated light-dark cycles can be (i.e., LDFB), but are not necessarily (i.e., rLDFB) inhibitory to the maintenance of the reproductive system in long day breeders. Furthermore, the lighting pattern derived from LDFB is stimulatory if given exogenously (i.e., LDFB NC). Although it is not understood why light exposure that is coincident with the subjective night (i.e., LD 1m:1m and LDFB) is not stimulatory in long day breeders, a possible hypothesis is that an internal coincidence model is involved in the photoperiodic response and that multiple transitions during the subjective night may cause a dissociation of internal oscillations which must be in phase for light to be stimulatory.

Animals↗
PubMed1985

Circadian rhythms of drinking and body temperature of the owl monkey (Aotus trivirgatus).

The rhythms of drinking and body temperature of 4 male owl monkeys (Aotus trivirgatus) were examined under conditions of LD 12:12 (L = 100 lx, D = 0.1 lx), DD (0.1 lx) and LL (100 lx). For all 4 monkeys, the circadian pattern expressed in LD 12:12 continued in DD, with a free-running period averaging 23.6 hr. In LL the circadian component of both rhythms decayed and, in one monkey, a low frequency pattern arose. In at least two aspects, masking and persistence, the owl monkey circadian timing system appears to be unlike that of its diurnal relative, the squirrel monkey. Circadian rhythms of owl monkeys also differ in some respects from those of other nocturnal mammals.

Animals↗
PubMed1985

Role of heat loss and heat production in generation of the circadian temperature rhythm of the squirrel monkey.

To study heat production and heat loss in determination of the daily body temperature rhythm, we examined colonic temperature, skin (tail, foot and abdomen) temperatures and oxygen consumption in chair-restrained squirrel monkeys maintained in isolation in an environmental chamber with a 24-hr light-dark cycle (LD 12:12), maintained at a constant thermoneutral temperature (26 degrees C). In all experiments repeated high amplitude (2 degrees C) diurnal rhythms in colonic temperature were observed. Heat loss, estimated from changes in skin temperature, also displayed a circadian rhythm, although there was considerable variation in waveform. On average, a rhythm in heat production, indicated by changes in the rate of oxygen consumption, was also present. However, a large degree of variability was seen in oxygen consumption, and in several cycles from various animals there were no observable 24-hr rhythms. The circadian body temperature rhythm is thus not simply a consequence of daily changes in metabolism, but rather a regulated response that involves both heat production and heat loss.

Animals↗
PubMed1985

Light effects on circadian timing system of a diurnal primate, the squirrel monkey.

We examined light effects on the circadian timing system of the squirrel monkey. A phase-response curve to 1-h pulses of light was constructed for the drinking rhythm of six animals. The phase-response curve was the same type as that exhibited by nocturnal rodents, with phase delays occurring early in the subjective night and phase advances late in the subjective night. The range of entrainment of 10 monkeys to days with 1 h light and x h dark was determined. Five monkeys used to generate the phase-response curve were also used in the range of entrainment determination. For short light-dark cycles the range of entrainment was smaller than that expected, with no monkey entraining to a day length of less than 23.5 h.

Animals↗
PubMed1983

Auditory entrainment of primate drinking rhythms following partial suprachiasmatic nuclei lesions.

In the absence of other environmental cycles, daily variations in auditory stimuli are normally not capable of entraining the circadian rhythms of drinking behavior in the squirrel monkey (Saimiri sciureus). However, the drinking rhythm appears to become entrainable by previously ineffective auditory cues after lesions are placed which destroy only the caudal portion of the hypothalamic suprachiasmatic nuclei. The results suggest specificity of function within the SCN and an increased influence of auditory stimuli in animals with impaired SCN function.

Acoustic Stimulation↗
PubMed1982

Circadian entrainment of the squirrel monkey by extreme photoperiods: interactions between the phasic and tonic effects of light.

To examine the role that the phasic and tonic aspects of the light-dark (LD) cycle play in entraining the circadian timing system of primates, squirrel monkeys (Saimiri sciureus) were exposed to 24 hr LD cycles in which the light duration (photoperiod) was varied from 1 sec to 23 hr. The monkeys were maintained in isolation and the circadian rhythm of drinking was monitored. The photoperiod was first gradually shortened until constant darkness was reached. Even in extremely short photoperiods of only one second of light per day, the drinking rhythm remained synchronized to the 24 hr period of the LD cycle. In the second set of experiments, the photoperiod was gradually lengthened until constant light was achieved. The drinking rhythm of all monkeys was synchronized by 21 hr photoperiods (LD 21:3), but free-ran in 23 hr photoperiods (LD 23:1) which provided a 1 hr dark pulse each day. The tonic effects of light may contribute to the difference between the ability to entrain to short versus long photoperiods. In constant darkness the free-running period was close to 24 hr, thus reducing the phase-resetting necessary to achieve entrainment to a 24 hr period by short light pulses. However, in constant light or in the long photoperiods which did not entrain (LD 23:1) the free-running period of the drinking rhythm was greater than 25 hr, thus requiring a much larger daily phase shift to achieve entrainment to a 24 hr period.

Animals↗
PubMed1981

Circadian rhythm of body temperature persists after suprachiasmatic lesions in the squirrel monkey.

Squirrel monkeys (Saimiri sciureus) demonstrate prominent circadian (approx 24 h) rhythms in many behavioral and physiological variables including drinking and body temperature. Both of these rhythms can be entrained by a 24-h light-dark cycle (LD 12:12) but will free-run with an endogenous period in a constantly illuminated (LL:600 lx) environment free of time cues. After radio-frequency lesions were placed stereotaxically in the suprachiasmatic nuclei (SCN) of five monkeys, the circadian rhythm of drinking behavior was disrupted when the monkeys were maintained in LL. However, the circadian rhythm in core body temperature in these animals persisted in LL with a significant circadian spectral component following destruction of the SCN. The SCN thus appear to be of fundamental importance for regulating the circadian organization of drinking; however, an oscillator located elsewhere in the squirrel monkey is capable of generating the core body temperature rhythm.

Acclimatization↗
PubMed1980

Renal responses to central vascular expansion are suppressed at night in conscious primates.

Renal and hemocynamic responses to central vascular volume expansion induced by 4 hr of continuous lower body positive air pressure (LBPP) were examined in conscious, chair-restrained squirrel monkeys in a light/dark (12:12) cycle. LBPP (30 mmHg) during both day (1200--1600) and night (0000--0400) induced similar 4 cmH2O stable increases in central venous pressure (P < 0.001), rises in heart rate of 25 beat/min (P < 0.001), and small transient elevations in mean arterial blood pressure. In contrast, while daytime LBPP induced a significant increase in urine flow (V) from 2.12 +/- 0.31 to 3.5 +/- 0.42 ml/h (P < 0.05), and sodium excretion (UNaV) from 71.1 +/- 14 to 271.2 +/- 37 mueq/h (P < 0.001), there was a marked nocturnal inhibition of the response to LBPP, with no significant increases in V or UNaV. Urine osmolality decreased by more than 50% at both times of pressure exposure; potassium excretion was not significantly affected by either exposure and drinking was suppressed during daytine LBPP. Comparisons of the time course and diurnal regulation of the urinary responses suggest that several separate efferent control pathways are involved.

Air Pressure↗
PubMed1979

Circadian control of thermoregulation in the squirrel monkey, Saimiri sciureus.

The characteristics and control of the circadian rhythms of core body temperature (colonic) and skin temperature (tail) were studied in chair-acclimatized squirrel monkeys (Saimiri sciureus). When animals were entrained to a light-dark cycle (12 h 600 lx; 12 h less than 1 lx) these two temperatures displayed prominent, reproducible, tightly coupled circadian rhythms. In contsant light of 600 lx, where no other effective circadian time cues were present, both temperature rhythms persisted with free-running periods. Within each animal, however, these rhythms were not as tightly coupled to one another as in LD. On occasion colonic and tail temperature rhythms free-ran with different circadian periods and some animals demonstrated "splitting" of the colonic temperature rhythm, with the colonic temperature rhythm displaying a bimodal pattern. These results suggest that the circadian rhythm of body temperature in primates is under the control of more than one potentially independent circadian oscillator.

Animals↗
PubMed1978

Thermoregulation is impaired in an environment without circadian time cues.

Squirrel monkeys synchronized to a 24-hour light-dark cycle show a prominent circadian rhythm in body temperature which is regulated against mild environmental cold exposures throughout the 24-hour day. However, cold exposures produce significant decreases in core body temperature when the circadian rhythms of the animal are free-running in the absence of environmental time cues. Effective thermoregulation appears to require the precise internal synchronization of the circadian timekeeping system.

Animals↗