Spacelab Life Sciences 1/STS-40

PAYLOAD PROFILE: SLS-1/STS-40

Mission Duration: 9 days

Date: June 5–14, 1991

Life Sciences Research Objectives
To study structural and functional changes that occur in the rat during microgravity exposure
To study the effect of microgravity on the development of gravireceptors and behavior of jellyfish
To evaluate the functionality of experiment hardware in the space flight environment

Life Science Investigations
Bone Physiology (SLS1-1, 2, 3, 4)
Developmental Biology (SLS1-5)
Endocrinology (SLS1-6, 7, 8)
Hardware Verification (SLS1-9, 10)
Hematology (SLS1-11, 12)
Immunology (SLS1-13, 14)
Metabolism and Nutrition (SLS1-15, 16, 17)
Muscle Physiology (SLS1-18, 19, 20, 21)
Neurophysiology (SLS1-22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
Pulmonary Physiology (SLS1-32)
Renal, Fluid, and Electrolyte Physiology (SLS1-33)

Organisms Studied
Rattus norvegicus (rat)
Aurelia aurita (jellyfish)

Flight Hardware
Ambient Temperature Recorder (ATR-4)
Animal Enclosure Module (AEM)
AEM Water Refill Box
Biotest Reuter Centrifugal Sampler (RCS)
General Purpose Transfer Unit (GPTU)
General Purpose Work Station (GPWS)
Jellyfish Kits and Kit Containers
Olympus 802 Camcorder
Refrigerator/Incubator Module (R/IM)
Research Animal Holding Facility (RAHF)
Small Mass Measuring Instrument (SMMI)


Mission Overview

The STS-40 mission was launched on the Space Shuttle Columbia on June 5, 1991. After a nine-day flight, Columbia landed at Edwards Air Force Base, California on June 14, 1991. The mission, managed by NASA Johnson Space Center, carried a crew of seven. Scientists from Russia, France, Germany, and Canada participated in the mission in the biospecimen sharing program. The mission was the first in which animals were allowed to float freely in microgravity outside of their cages and the first time jellyfish were flown in space.

The primary mission objective was to conduct the experiments in the Spacelab Life Sciences 1 (SLS-1) payload located within the Spacelab module. The goals of Ames Research Center (ARC) were to prove the functionality of the improved Research Animal Holding Facility (RAHF) and ensure that the RAHF and General Purpose Work Station (GPWS) maintained particulate containment relative to the Spacelab environment during all operations. Rats and jellyfish served as subjects for the seven experiments sponsored by ARC. Scientists sponsored by ARC also conducted 17 collaborative experiments with Russian scientists on rat tissue specimens. In addition, through the SLS-1 biospecimen sharing program, more than 6000 rat tissue samples were distributed to scientists from participating countries for supplementary studies.

Life Sciences Research Objectives

The primary objective of SLS-1 was to conduct two hardware verification tests. A Particulate Containment Demonstration Test (PCDT) was to verify that the integrated system of animal housing and transfer hardware functioned in microgravity, without contaminating the crew environment. Specifically, the test was designed to demonstrate that the RAHF and GPWS can contain solid particles down to 150 microns in size, that the GPWS can contain fluids, and that the General Purpose Transfer Unit (GPTU), hardware designed to transfer research subjects between the RAHF and GPWS, can maintain containment during transfer operations.

The Small Mass Measuring Instrument (SMMI) test was designed to verify functional stability of the instrument in microgravity and to give crew members some experience in operating the device. The SMMI was to be used to determine the mass of rodents and tissues on the SLS-2 mission, since conventional weight measurements are not possible in microgravity.

The requirements of the hardware test determined the number and habitation conditions of the rodents. Within these constraints, SLS-1 provided an opportunity to conduct many life sciences studies. The rat studies on SLS-1 were designed to examine the structural and functional changes that occur in response to space flight. Muscle experiments examined the adaptation of muscle tissue to microgravity. Hematology experiments examined changes in blood volume and cellular components and alterations in the process of blood cell formation. Studies of the vestibular system focused on changes in gravity receptors during exposure to microgravity and adaptation on return to the Earth's gravitational field. Calcium physiology studies were expected to clarify and expand on data from previous Cosmos biosatellite missions, which had shown that space flight causes a negative calcium balance, decreased bone density, and inhibited bone formation. Rats were flown in two cage configurations in order to compare the responses of singly housed and group-housed subjects.

The jellyfish development and behavior experiment had two objectives. One was to determine whether the asexually reproducing polyp form of jellyfish could metamorphose normally into the sexually reproducing ephyra form (Fig. 4). The other was to determine whether the development of gravity-sensing organs and swimming behavior are affected by microgravity.

Table 1
Figure 4. Aurelia aurita undergoes both asexual and sexual reproduction during its life cycle. Sessile polyps metamorphose into strobilae, which produce ephyrae by asexual budding. The ephyrae mature into medusae, which produce zygotes and reproduce sexually. Planula larvae that hatch from fertilized eggs eventually attach to a new substrate and develop into polyps.

Life Sciences Payload

Organisms
The rat experiments used 74 male specific pathogen free Sprague-Dawley rats (Rattus norvegicus). The flight group contained 29 rats, while the ground control groups contained 45 rats. At the time of launch, the rats weighed between 250 and 300 g and were nine weeks old.

Approximately 2400 moon jellyfish (Aurelia aurita) were flown in two groups. One group was in the polyp stage at launch, while the other was in the ephyra stage.

Hardware
The General Purpose Work Station (GPWS) was evaluated and verified in the PCDT using rodents and cages housed in the RAHF. The GPWS is a laboratory work bench and biohazard cabinet for experiment operations in the Spacelab. It provides containment of chemical vapors, liquids, and debris released within it during experiments, such as dissections or specimen fixation. The crew can perform various procedures inside the cabinet by inserting their arms into the gauntlets attached to ports at the front and right side of the cabinet. The gauntlets stop at the wrists, and crew members wear disposable surgical gloves after inserting their arms. A window on one side of the cabinet allows interface with the General Purpose Transfer Unit (GPTU), which facilitates rodent cage transfer from the RAHF to the GPWS. The GPTU has a frame with a sliding access door that interfaces with both the RAHF and the GPWS. A sock attached to the frame encloses the rodent cage during transfer. The GPTU is specifically designed to provide a second level of particulate containment.

A modified version of a commercial air sampling device, the Biotest Reuter Centrifugal Sampler (RCS), was used in the PCDT to collect released particulates for postflight analysis.

The Small Mass Measuring Instrument (SMMI) was tested to verify its calibration-maintenance capabilities and was used to measure the mass of rodents and tissue samples by use of inertial methods. While weight varies with gravitational force, mass remains constant. The weight equivalent 1 G conditions can be calculated using a simple mathematical formula.

Rats were housed in two habitat types: the Animal Enclosure Module (AEM) and the Research Animal Holding Facility (RAHF). The AEM is a self-contained animal habitat, storable in a Shuttle middeck locker, which provides ventilation, lighting, food, and water for a maximum of six adult rats. Fans inside the AEM circulate air through the cage, passively controlling the temperature. A filtering system controls waste products and odors. Although the AEM does not allow handling of contained animals, a clear plastic window on the top of the unit permits viewing or video recording. The Water Refill Box enables inflight replenishment of water.

The RAHF is a general use animal habitat designed for use in the Spacelab module. Animal-specific cage modules are inserted, as needed, to provide appropriate life support for rodents. Cages can be removed from the RAHF to accommodate inflight experiment procedures. The RAHF habitat consists of rodent cage assemblies, each of which carries two rats separated by a divider. The environmental control system actively controls temperature and passively controls humidity, carbon dioxide, and oxygen levels, and maintains particulate containment during cage removal. The feeding system supplies rodent food bars on a demand basis. The water system provides pressurized, regulated water to rodents. The waste management system collects urine and feces in a waste tray and neutralizes odor. The lighting system provides a controllable light cycle for the cages. Activity monitors in each cage record general movement using an infrared light source and sensor. The data system collects environmental and animal data that is passed on to the Spacelab data system for display, recording, and downlink to the ground.

Jellyfish Kits, placed in the Shuttle middeck, were used to maintain jellyfish during flight, measure the radiation dose, and apply fixative to specimens. Three of the four kits contained polyester bags with polyethylene lining, and the remaining kit contained polyethelene culture flasks, which allowed filming of the live specimens. Both bags and flasks were filled with artificial sea water and air. Kit #1 contained 18 bags, six of which contained radiation dosimeters. Kit #2 contained syringe/bag assemblies with one to three syringes of fixative attached. Kit #3 was used to hold the fixed specimens from Kit #2. Kit #4 contained the culture flasks.

The Refrigerator/Incubator Module (R/IM) maintained a constant temperature of 28 °C for the jellyfish. The R/IM is a temperature-controlled holding unit flown in the Shuttle middeck that maintains a cooled or heated environment. It is divided into two holding cavities and can contain up to six shelves of experiment hardware.

An Ambient Temperature Recorder (ATR-4) accompanied each AEM and the R/IM. The ATR-4 is a self-contained, battery-powered package that can record up to four channels of temperature data.


Table 1. Flight and Control Groups for SLS-1 Rodents. (Click to enlarge)

An Olympus 802 camcorder was used to film the jellyfish in flasks. The camcorder, an 8-mm commercial model with standard features, was mounted on a multiuse bracket assembly, which also held the jellyfish specimen flask at a fixed distance.

Operations

Preflight
Three days before launch, flight and control rat groups were selected based on health, behavioral, and experimental criteria. The flight rats were chosen for two groups: 10 housed in the AEM and 20 housed in the RAHF. Each flight group had a synchronous ground control counterpart with an identical number of rats and a basal control counterpart with half the number of rats (Table 1). For the bone experiment, the rats were injected with the markers calcein and demeclocycline. The hematology experiment required blood draws and injection of multiple radioisotopes.

The RAHF cages containing the flight subjects were loaded into the Spacelab about 29 hours before the flight. On the day of launch, a water lixit failed to function in one of the RAHF rodent cages. That cage was flown empty, resulting in a RAHF flight group of 19 rats. To allow for late loading at about 15 hours before launch, the AEMs were placed in the middeck rather than the Spacelab.

Two days before launch, 2478 jellyfish arrived at Kennedy Space Center in a portable incubator. The jellyfish were divided into 32 groups. Six groups of 25 jellyfish each were loaded into Kit #4 flasks for the jellyfish behavior experiment. The remaining 26 groups were placed in Kit #1 and Kit #2 for the developmental studies. One hundred polyps were placed in each of the 18 Kit #1 specimen bags, while 66 polyps were placed in the eight Kit #2 bags. Polyps in six Kit #1 and two Kit #2 specimen bags were treated with iodine or thyroxine, substances that induce metamorphosis, so that the jellyfish would metamorphose into strobilae during the flight. Six more groups of Kit #1 polyps were treated 24 hours before launch. Two Kit #1 groups remained untreated.

Inflight
For the PCDT, the crew emptied particulates consisting of food bar crumbs, rodent hair, and simulated feces (in the form of black-eyed peas) into two empty rodent cages in the RAHF by unsheathing particulate-filled balloons during the flight. The RCS was then placed in front of each cage to collect any released particulates. Fine mesh screens, on which particulates were captured, were stowed away for postflight analysis. Inflight results of the test showed high levels of containment, allowing the crew to transfer some of the rats to the GPWS from the RAHF. Also, rats were released to float freely within the GPWS, providing the crew and scientists on the ground the opportunity to observe animal behavior outside cages in microgravity. Though unplanned, this activity was vital in planning SLS-2 operations and predicting the animal reactions within the GPWS.

The crew also tested the function of the SMMI during the flight. They confirmed that the instrument was stable in microgravity and practiced making rodent and tissue measurements to be performed on SLS-2.

For the rat studies, light in the AEMs and RAHF was cycled at 12 hours of light and 12 hours of darkness. Temperature in the AEM was 27 to 32 °C and temperature in the RAHF was maintained at 252 °C. The crew observed and videotaped the rats in the RAHF and AEMs, refilled water in the AEMs, and performed feeder changeouts on the RAHF.

The crew performed various procedures to repair hardware malfunctions. Despite their efforts, some hardware units did not function as well as expected during the mission. Three of the RAHF activity monitors failed inflight, but food and water consumption data were used to determine that the animals were active. The RAHF drinking water pressure transducer failed on the fifth flight day. Water consumption data were not accurate because of variability in calibrating cage-by-cage delivery against the computer system.

The crew conducted several experiment operations on the jellyfish packages. These activities were conducted inside the GPWS for safety reasons, even though the Jellyfish Kits provide three containment layers of polyethylene. Eight hours after launch, the crew removed kit container #2 from the Refrigerator/Incubator Module and injected iodine into three specimen bags and thyroxine into three specimen bags in order to induce metamorphosis of the jellyfish polyps. One group of jellyfish ephyrae in flasks were videotaped on the second, third, and fourth flight days. Two other groups of jellyfish were videotaped on the fifth and sixth flight days. On the eighth day, the crew injected glutaraldehyde into six of the bags to fix the jellyfish and stored the bags in kit container #3 in the Spacelab Refrigerator.

Ground control studies for the jellyfish experiment included 32 groups of jellyfish, 14 of which formed a synchronous control. The remaining 18 groups formed a one-week delayed-synchronous control.

Postflight
Shortly after the Shuttle landed, the flight and control rats were removed from their habitats, weighed, and assessed for general health. They were then photographed and videotaped. Immediately after touchdown, 10 of the rats from the RAHF, five from the AEM, and their respective ground control counterparts were sacrificed. For the bone experiments, the remaining nine RAHF flight rats, five AEM flight rats, and ground control rats were given injections of tritiated proline and calcein. Blood was also drawn from these rats for the hematology experiment. The rats were sacrificed after they had been allowed to readapt to Earth gravity for nine days postflight.

A specially trained team conducted the postflight dissections. Ames Research Center involvement in the biospecimen sharing program included oversight of the laboratory facilities used by visiting Russian investigators, receipt of flight tissue samples, and coordination of shipment of samples to Russia and France.

A Delayed Flight Profile Test (DFPT) was conducted, beginning with the receipt of rats on June 6, 1991, at Kennedy Space Center using flight RAHF and flight AEM hardware. The DFPT simulated the SLS-1 mission timeline, the flight environmental conditions, including temperature, humidity, and light/dark cycles, and significant operational events, such as hardware maintenance and rodent handling. Noise, vibration, and acceleration profiles experienced during space flight were not simulated.

Results

Hardware
Both hardware tests verified the utility and functionality of the GPWS and the SMMI. The PCDT using the GPWS and the RAHF was successful. Postflight analysis of the screens collected revealed that particulate accumulation occurred during only one condition and on one screen at less than 50 microns in size. This particulate accumulation was due to the failure of the crew to adequately clean the interior backside of the GPWS front window, which led to the entrapment of material when the window was raised. Proper cleaning prevented a repeat condition during the second particulate release. The SMMI performance exceeded expectations and produced accurate measurements during all trials.

Rodents
Compared to the ground control rats, flight rats, upon landing, appeared be lethargic, to have reduced muscle tone, and to use their tails less as balancing aids. These effects were more noticeable in the rats housed in the AEMs than in those housed in the RAHF. Flight rats gained less weight during the flight period than did ground controls. There was no difference in body weight gain between rats housed in the RAHF and those housed in the AEM.

The hematology experiments showed that on the day of landing, the flight rats had fewer red and white blood cells than did ground controls, but their levels returned to normal by the ninth day postflight. Muscle studies indicated that functional and structural changes occurring in muscle tissue could impair the normal movement patterns involved in antigravity function and postural control. Housing type was found to affect some of the changes occurring in bone during space flight: singly housed animals were affected to a greater degree and showed slower recovery than group-housed animals. Research on gravity sensors indicated that rats were able to adapt to the microgravity environment better than anticipated. Results also indicated that metabolism, immune cell function, cell division, and cell attachment may be affected by microgravity.

Jellyfish
Jellyfish ephyrae that developed in microgravity were normal in most respects, although they showed hormonal changes while in space and abnormalities in swimming behavior after returning to Earth. Ephyrae that were flown after developing on Earth tended to show changes in their gravity-sensing organs. The swimming behavior of both ephyrae hatched on Earth and those that developed in microgravity showed that they had difficulty orienting themselves in space.

Additional Reading

Dalton, B.P., G. Jahns, J. Meylor, N. Hawes, T. N. Fast, and G. Zarow. Spacelab Life Sciences-1 Final Report. NASA TM-4706, August 1995.

NASA. STS-40 Press Kit, May 1991. Contained in NASA Space Shuttle Launches Web site: http://www.ksc.nasa.gov/shuttle/missions/missions.html.

Interview

Biospecimen Sharing and Tissue Archiving
an interview with Paul X. Callahan