Modification by Light of 24-Hour Activity of White Rats

The 24-hour rhythm of running activity of white rats originates from a light-cycle and can be reversed by illuminating at night rather than by day. If continuous light is used, the activity phase of the rhythm remains 8-12 hours in length but shows a regular, constant and definite amount of alteration or delay in the time of starting so that the activity block travels around the clock. Behavior modification such as this should be called a photoperiodic response. In the present studies the photoperiodic data were: (1) the delay in time of starting activity for rats in continuous light was 3/4 hour per day, and their activity traveled around the clock in 16 days; (2) during the progress of a reversal of the 24-hour solar light cycle, when light fell on the activity block there was a regular delay of 3 hours/day, only until the activity block again fell in darkness; (3) finally with a 16-hour light cycle of 8 hours of illumination and 8 hours of darkness, the delay was continuous at 1 hour a day. By raising rats with no cycle of nursing or other regular environmental influences, further evidence was obtained for the inheritance of what seems to be an activity rhythm of about 12 hours of activity and 12 hours of inactivity

Physiological Research in Northern Alaska

Review physiological field research from 1881, citing the scientists and their studies. At the Naval Arctic Research Lab at Barrow there have been projects on blood analysis, nutritional data, energy and fat metabolism, temperature regulation, animal navigation, eye physiology, reproductive physiology of arctic and temperate zone animals, and measurement of time by animals. Techniques, such as the insertion of radio-capsules in bears and foxes, are illustrated and future research needs for data on man and animals discussed

Human Skin Temperature and Biological Clocks: A Laboratory Exercise for Physiology Students

A simple laboratory experiment is described, consisting of taking the mean temperature between two fingers of human subjects. The results from comparing male and female students is presented. The change in skin temperature over four hours is documented, to demonstrate the importance of doing standardized experiments at the same time of day

Notes on Comparative Tolerance of Some Iowa Turtles to Oxygen Deficiency (Hypoxia)

Six species of Iowa turtles (including pharyngeal water-pumpers and non-pumpers) were tested for resistance to anoxia. Five species of juveniles were included in the series. With the exception of Trionyx, adult aquatic turtles tolerated hypoxia longer than juveniles of the same species. Some terrestrial species were as tolerant as some aquatic species. Maximum tolerance time submerged (18° to 19°C) was 56 hours for an equatic species, Chrysemys picta, whereas that of a terrestrial species, Terrapene ornata, was 12 hours

Bradycardia of the Polar Bear

For several years two male polar bears have been studied by long-life implanted physiological radio capsules at the Naval Arctic Research Laboratory, at Point Barrow. One of the siblings has consistently been larger than the other. A regular measurement has been the resting heart rate; for this we used the lowest heart rate obtained during night-time sleep. Night-time sleep is used because different heart rate levels are obtained during day-time sleep and night-time sleep. The two bears, during the continuous light of the summer, sleep regularly from about 11 PM until 9:00 AM; occasionally short bouts of sleep occur around early afternoon. Sleeping heart rates have been obtained throughout the lifetime of these two individuals. For example, during the summer of 1971, the larger polar bear, Irish (310 kg), had mean resting heart rates of 54 ±2 SD b/m (N=12); in 1972 at 332 kg his rate was 48 ±5 SD b/m (N=12); the smaller bear in 1971, at 286 kg, had a lower sleeping heart rate (50 ±5 SD b/m). ... A technique for demonstrating bradycardia (rapid slowing of heartbeat) in marine mammals was developed by Irving and Scholander, namely instrumenting the animal and training it to place its head under water. We decided to try this technique with the larger of the polar bears (Irish). The bear was separated from its companion, deprived of food and water overnight, and then recorded during three routine situations: 1) during high activity time; 2) during the filling of the water tub (approximately 300 litres) and 3) during feeding time. Heart rates were taken by the stopwatch every 15 seconds. ... Head immersion and diving bradycardia were evident for periods lasting up to 2 minutes; during that time the animal appeared to be searching for food at the bottom of the tub. Although diving bradycardia was evident (rate reduced 10 per cent to 72 b/m), it is apparent that there was much more bradycardia during the period of eating (reduced 20 per cent to 60 b/m). This slow rate during eating was remarkably close to the sleeping heart rate. One might have expected the heart rate to go up during the excitement of feeding. Also, competition for the food was not entirely lacking; the companion polar bear in the adjoining cage was constantly reaching through the bars as it attempted to obtain some of the food. One might have expected this activity to increase the excitement. We have found no other reference to bradycardia during feeding

Distribution and Habitat of the Red Squirrel, Tamiasciurus hudsonicus, in the North Central States

A survey of the distribution and habitat of the red squirrel (Tamiasciurus hudsonicus) was conducted in northern Iowa, southern Minnesota, and Wisconsin. The results indicate that the present range of the red squirrel in Iowa covers the north central counties of the state, and is considerably smaller than that given in earlier surveys. The Iowa red squirrel lives in immature hardwood forests near rivers and lakes. If mature trees arc present, they are used for nesting and caching food. The preferred foods of the Iowa red squirrel are the black walnut (Juglans nigra) and the butternut (Juglans cinerea). In Wisconsin and southern Minnesota the red squirrel usually inhabits coniferous forests

Overlapping of Ranges of Eastern and Western Hognose Snakes in Southeastern Iowa

Overlapping of ranges of the eastern hognose snake (Heterodon platyrhinos Latreille) and the western hognose snake (Heterodon nasicus nasicus Baird and Girrard) is reported from a sand prairie in Muscatine County, Iowa

Radiative Heat Loss from Skin to Cold Glass Windows

Today institutional rooms of many types have single large glass window panes measuring as large as 3.0 meters by 2.5 meters; animal colonies are maintained near these windows in winter, office workers sit by them and thinly clad patients on littercarts are placed beside them. Even though both local air and wall temperature may be 22°C, human subjects beside the windows in winter feel cold because body heat is radiated to the glass which acts as a heat sink. An experiment was conducted during two Iowa winters with measurements of temperatures of outside air, room, wall, undraped glass window, drape-covered window and skin to determine radiated heat loss and to assess the effects of a radiation shield (drape). The glass could be as low as 2°C. Results showed greater protection to the skin by the drape as the weather became colder, although the glass temperature did not change with the weather as much as was expected. Using a standardized room for calculations, we showed that if a person moved from a back wall to a position beside the glass window, he would increase his total heat loss by 32 percent

Some Factors Influencing the Life Span of Golden Hamsters

The golden hamster has found increased use as a laboratory animal over the last two decades. It is of particular interest because it hibernates although its periods of dormancy are short compared to those of other hibernators (1). The complete spectrum of physiological norms should be determined for this common animal just as they were for the laboratory rat. In the list of normal values for the hamster there is little published information on life span (2). This paper will present records of life spans of 126 hamsters kept under controlled laboratory conditions. Approximately 43% of the colony were maintained with a daily light cycle in a coldroom (6 ± 2 ° C.) for about 4 months each winter. Other conditions of the experiment have been described earlier in detail (1). For the purposes of this analysis the cold-exposed group was treated as a homogenous population, in spite of the fact that some of the animals hibernated. This combining of animals was due to the fact that there was such variation in the total duration of hibernation over the winter periods. Some hamsters hibernated for one day, others were in hibernation for a total of 95 days. The systematic pattern of results justifies this approach to this analysis. To be specific, the data treated in this paper look as if cold-exposure with or without hibernation produced the same effects upon the animals, in most respects. Furthermore, the hibernators were distributed nearly equally among four groups of cold-exposed animals. Later analyses will attempt to consider the influence of hibernation as a separate factor. We will ref.er in this report only to the cold-exposed group: this means a mixed group of males and females of two strains of animals, most of which were coldexposed 4 months, but a few of which received only 3 months of cold-exposure at 6° C. and a few weeks at 16° C. About 12 of the males and 10 of the females hibernated for variable periods of time

A Multiple Point Recorder for Small Animal Locomotor Activity

This recorder is intended to simplify the assessment of data gathered from photoelectric actometers registering total locomotor movements. The information is presented automatically in two forms: (1) a curve of total activity over a 24 hour period, (2) a bar graph of the activity in each 30 minute time interval. A further trace is used to enable the time of onset of bursts of activity to be judged with reasonable accuracy. A particular advantage lies in the fact that the recording pens are stationary, making it possible to plot the outputs from several activity counters across the whole width of the recording paper. Standard electrical components which are easily available are used throughout the equipment