Behavior and reproduction of invertebrate animals during and after a long-term microgravity: space experiments using an Autonomous Biological System (ABS)

Aquatic invertebrate animals such as Amphipods, Gastropods (pond snails), Ostracods and Daphnia (water flea) were placed in water-filled cylindrical vessels together with water plant (hornwort). The vessels were sealed completely and illuminated with a fluorescent lamp to activate the photosynthesis of the plant for providing oxygen within the vessels. Such ecosystem vessels, specially termed as Autonomous Biological System or ABS units, were exposed to microgravity conditions, and the behavior of the animals and their reproduction capacity were studied. Three space experiments were carried out. The first experiment used a Space shuttle only and it was a 10-day flight. The other two space experiments were carried out in the Space station Mir (Shuttle/Mir mission), and the flight units had been kept in microgravity for 4 months. Daphnia produced their offspring during a 10-day Shuttle flight. In the first Mir experiment, no Daphnia were detected when recovered to the ground. However, they were alive in the second Mir experiment. Daphnia were the most fragile species among the invertebrate animals employed in the present experiments. All the animals, i.e., Amphipods, pond snails, Ostracods and Daphnia had survived for 4 months in space, i.e., they had produced their offspring or repeated their life-cycles under microgravity. For the two Mir experiments, in both the flight and ground control ecosystem units, an inverse relationship was noted between the number of Amphipods and pond snails in each unit. Amphipods at 10 hours after the recovery to the ground frequently exhibited a movement of dropping straight-downward to the bottom of the units. Several Amphipods had their legs bent abnormally, which probably resulted from some physiological alterations during their embryonic development under microgravity. From the analysis of the video tape recorded in space, for Ostracods and Daphnia, a half of their population were looping under microgravity. Such looping animals could be observed still at the end of the 4 month stay in space. No looping behavior was noted for Amphipods and pond snails.

Development of space-fertilized eggs and formation of primordial germ cells in the embryos of Medaka fish

In the second International Microgravity Laboratory (IML-2) mission in 1994, four small Japanese killifish (Medaka, Oryzias latipes) made a space travel of 15 days aboard a space shuttle. These four adult Medaka fish successfully mated in space for the first time among vertebrate animals. Moreover, the eggs they laid developed normally, at least in their external appearance, hatching as fry (baby fish) in space. Fish mated and laid eggs every day during the first week. Near the end of the mission most of the eggs had a well-developed body with two pigmented eyes. In total, 43 eggs were laid (detected), out of which 8 fry hatched in space, as truly 'space-originated' babies. A further 30 fry hatched within 3 days after landing. This is the normal hatching rate, compared with the ground-based data. Among the 8 space-originated fry, four were killed for histological sections, and germ cells at the gonadal region were counted for each fry. Their numbers were in the range of the germ cells of the normal control fry (ground-kept samples). Thus, as embryos developed normally in their external appearance, inside the embryos the formation of primordial germ cells took place normally in space, and their migration to the genital ridges was not hindered by microgravity. The two of the remaining space-originated fry have grown up and been creating their offspring in the laboratory. This proved that the primordial germ cells formed in space were also normal from a functional point of view. The four space-travelled adult fish re-started mating and laying eggs on the 7th day after landing and continued to do so every day afterward. Fertilization rate and hatchability of these eggs were as high as the eggs laid by the laboratory-kept fish. This fact implies that in gametogenesis of adult fish, there are no specific stages of germ cells extremely susceptible to microgravity.

Clinical course of conservatively managed rheumatoid arthritis patients with myelopathy

STUDY DESIGN

The clinical course of rheumatoid arthritis patients with myelopathy who do not undergo surgery was studied.

OBJECTIVES

To establish a more accurate prognosis for rheumatoid arthritis patients who do not undergo surgery.

SUMMARY OF BACKGROUND DATA

Cervical myelopathy has been reported in two thirds of rheumatoid arthritis patients with atlantoaxial dislocation. Atlantoaxial fusion, or occipitocervical fusion, is widely performed on these patients. However, several researchers reported serious complications from the surgery, including nonunion, worsening myelopathy, and high mortality. The natural course of disease in rheumatoid arthritis patients with myelopathy should be known before definitive treatments can be outlined.

MATERIALS AND METHODS

Twenty-one rheumatoid arthritis patients with myelopathy resulting from atlantoaxial dislocation were studied. Fourteen of the 21 cases were associated with upward migration of the odontoid process. All of these patients were recommended for surgery, but they refused. Patients were reviewed by direct examination yearly. Radiographic changes and clinical course, including the survival rate, were observed.

RESULTS

Atlantodental interval and Redlund-Johnell measurements deteriorated. The patients showed no neural improvement, and deterioration was found in 16 (76%) cases during follow-up. All patients became bedridden within 3 years of the onset of myelopathy. Seven of the 21 patients died suddenly for unknown reasons, 3 died of pneumonia, and 1 died of multiple organ failure. The three sudden-death cases showed progressive upward migration of the odontoid process. The cumulative probability of survival was 0% in the first 7 years after the onset of myelopathy.

CONCLUSIONS

The clinical results for rheumatoid arthritis patients with myelopathy treated without surgery are extremely poor. Surgical treatment is recommended for rheumatoid arthritis patients with myelopathy.

Explanations for a video version of the first vertebrate mating in space--a fish story

In 1994, Japanese killifish, Medaka (Oryzias latipes) mated, laid eggs, and had babies in space. This was the first successful mating behavior carried out in space by vertebrate animals. Recently, the author has edited a video tape, which contains the video images of the fish mating, development of eggs, swimming behavior of baby fish in space, and also scenes of various preparatory experiments on the ground. The video tape is available, without any charge when requested to the author (K. Ijiri). This paper explains for each scene of the video tape.

Primordial germ cells in the embryos of Medaka fish

In the second International Microgravity Laboratory (IML-2) mission in 1994, four small Japanese killifish (Medaka, Oryzias latipes) made a space travel of 15 days aboard a space shuttle. These four adult Medaka fish successfully mated in space for the first time among vertebrate animals. Moreover, the eggs they laid developed normally, at least in their external appearance, hatching as fry (baby fish) in space. Fish mated and laid eggs every day during the first week. Near the end of the mission most of the eggs had a well-developed body with two pigmented eyes. In total, 43 eggs were laid (detected), out of which 8 fry hatched in space, as truly 'space-originated' babies. A further 30 fry hatched within 3 days after landing. This is the normal hatching rate, compared with the ground-based data. Among the 8 space-originated fry, four were killed for histological sections, and germ cells at the gonadal region were counted for each fry. Their numbers were in the range of the germ cells of the normal control fry (ground-kept samples). Thus, as embryos developed normally in their external appearance, inside the embryos the formation of primordial germ cells took place normally in space, and their migration to the genital ridges was not hindered by microgravity. The two of the remaining space-originated fry have grown up and been creating their offspring in the laboratory. This proved that the primordial germ cells formed in space were also normal from a functional point of view. The four space-travelled adult fish re-started mating and laying eggs on the 7th day after landing and continued to do so every day afterward. Fertilization rate and hatchability of these eggs were as high as the eggs laid by the laboratory-kept fish. This fact implies that in gametogenesis of adult fish, there are no specific stages of germ cells extremely susceptible to microgravity.

Mini ecosystem in space--preliminary experiment on board STS-77

An enclosed ecosystem which is stable on Earth will behave differently when brought into space. Micro-gravity and radiation will affect the dynamics of material circulation or the activities of small creatures of the ecosystem. One series of space experiments aiming to address such issues was planned in the United States (It is termed as ABS--Autonomous Biological System) and Japanese group has been involved with cooperating with the analysis of the flight samples. Before the ecosystem will be on board Russian Space Station "Mir" later 1996 for 3 months, a preliminary flight was carried out in May 1996 on Space Shuttle (STS-77) for 10 days flight. It was the first of such experiments to fly one whole ecosystem in space.

The effect of pulsing electromagnetic field on bone ingrowth into a porous coated implant

Electromagnetic stimulation is known to promote bone formation in cases of fracture and pseudoarthrosis. The possibility of using electromagnetic field to promote bone ingrowth into a porous coated implant was investigated in this study using Japanese albino rabbits. A titanium implant coated with beads of 250-300 microns in diameter around a stem of 1.7 mm in diameter was inserted into the humerus cavity of a Japanese albino rabbit. The humerus was stimulated by pulsing electromagnetic fields at 2 Gauss, 10Hz, 25 microseconds for 14 days. The circumference of grown bone into the implant was measured, and calculated in area equivalent for determination of the area of new bone. Bone ingrowth was significantly promoted by consecutive 14 days. The result suggests that electromagnetic stimulation is useful for achieving further bone ingrowth into a porous coated implant.

Osteogenesis by pulsing electromagnetic fields (PEMFs): optimum stimulation setting

The optimum setting for electromagnetic stimulation was examined by histologically assessing the degree of osteogenesis at different settings of electromagnetic stimulation, and comparing alkaline phosphatase (ALP) activity in the bone marrow. For this experiment, an electromagnetic field generator manufactured by the Institute of Physical and Chemical Research was used. The intensity of the magnetic field was set at eight levels; 0.1, 0.2, 0.4, 1, 2, 4, 6 and 8 gauss (G). The frequencies used were 5, 10, 20, 50, 100 and 200 Hz. Pulse durations were 6, 12, 25, 50 and 100 micro sec. Significant ALP elevation and osteogenesis were observed at magnetic field intensities of 0.4, 1, and 2G. ALP activity did not differ between different frequencies. ALP activity at pulse durations of 25 and 50 micro sec were significantly higher than at the other pulse durations. The effect of electromagnetic stimulation on osteogenesis greatly depends on the intensity and pulse duration of the stimulation.

Parathyroid hormone therapy accelerates recovery from immobilization-induced osteopenia

Previous reports have shown that bone mass and architecture will partially recover by remobilization (RM) in immobilization (IM)-induced osteopenia. The aim of this study was to test whether PTH can accelerate the recovery during RM from the IM-induced osteopenia. Six-month-old Sprague-Dawley female rats were divided into aging and IM groups. The right hindlimb of rats was immobilized against the abdomen by elastic bandages for 18 weeks, then groups of rats were further IM or RM for 2, 10 and 20 weeks and given 30 or 80 micrograms hPTH (1-38)/kg/d s.c. Secondary spongiosa of proximal tibial metaphyses (PTM) were studied. Immobilization reduced the trabecular area, number and thickness at the first 18 weeks post IM, then plateaued. Ten weeks of RM restored 40% trabecular bone from IM controls due to thickening of the trabeculae. However, the trabecular area was still -14% and -13% lower than that of aging controls at 10 and 20 weeks. Two weeks of 30 micrograms PTH/kg/d in IM rats restored the bone to aging control levels, two weeks of 30 micrograms PTH/kg/d in RM rats and of 80 micrograms PTH/kg/d in both RM and IM rats added extra bone. Extending the treatment to 10 and 20 weeks, the same amount of total bone was added to both IM and RM rats. These findings indicate PTH is a powerful agent that can accelerate the recovery and add extra bone to osteopenic cancellous bone in both IM and RM rats.

Remobilization partially restored the bone mass in a non-growing cancellous bone site following long term immobilization

There is no report in the rat of the effects of remobilization (RM) in an adult bone site. The aim of this study was to determine whether complete recovery from IM-induced bone loss will occur in a non-growing bone site, the distal tibia. Seventy-five 6-month-old virgin Sprague-Dawley female rats were used in this study. Their hindlimbs were immobilized against the abdomen with bandages for 18 weeks, then remobilized for 2, 10 or 20 weeks. Distal tibial sections were analyzed in the former epiphysis, 0.3 mm proximal from the calcified cartilage, and in trabecular bone of the former metaphysis between 0.3 mm and 1.92 mm proximal to the former epiphysis. A significant bone loss occurred in both former epiphyseal and metaphyseal trabeculae at 18 weeks after IM. The lost bone was partially recovered at 10 weeks of RM, but the bone mass was still lower than in aging controls by the end of the study. The partial recovery was characterized by decreasing former epiphyseal bone porosity and thickening of former metaphyseal trabeculae with no effect on trabecular number. We concluded that both distal tibia regions only partially recovered, during 20 weeks of RM from the long time IM.

Adaptation of non-growing former epiphysis and metaphyseal trabecular bones to aging and immobilization in rat

No data exit for distal tibia (DT), a bone site with growth plate closure at 3 months of age and with very low trabecular bone turnover rate. The purpose of this study was to characterize the response of DT to aging and immobilization (IM) in 6 to 16.5 month-old female rats. One hundred and forty six 6 month-old Sprague-Dawley rats were divided into aging controls and right hindlimb immobilization (RHLI) groups. The right hindlimb was immobilized against the abdomen with elastic bandages. Rats were sacrificed serially from 6 to 16.5 months old at intervals of 2 to 8 weeks. The histomorphometric study was performed on areas of former epiphyseal and metaphyseal trabecular bone of DT. No changes on bone mass or architecture were found in aging controls throughout the study. There was a decrease in bone mass of the former epiphysis after 3.5 months of IM due to resorption exceeding formation. Then it reverted to the aging control level at 4 months post IM. At the former metaphyseal site, significant bone loss (-19%) was observed as early as two weeks after IM. The peak bone loss (-54%) was reached at 1.5 months after IM and plateaued thereafter. The bone loss was mainly due to the reduction of trabecular thickness although trabecular number decreased significantly after 3.5 months IM. These results suggest that both former epiphysis and metaphyseal trabecular bones in DT can quickly adapt by losing bone to immobilization.

Co-treatment of PGE2 and risedronate is better than PGE2 alone in the long-term treatment of ovariectomized-induced osteopenic rats

We studied the effects of prostaglandin (PGE2) and risedronate (Ris) alone or in combination in 3.5-month-old intact and ovx-induced osteopenic rat skeletons to determine whether PGE2 plus Ris was more anabolic than PGE2 alone. Six mg PGE2/kg/d and 5 micrograms Ris/kg/2x/wk alone or in combination were given to sham-ovx and ovx rats for 30 or 90 days beginning 60 days post operation. Secondary spongiosa of proximal tibial metaphyses (PTM) was studied. Ovariectomy (ovx) induced dramatic bone loss. Ris increased bone mass in sham-ovx rats and prevented further bone loss in ovx rats. PGE2 treatment for 30 days added extra bone in sham-ovx rats and no further increase after 90 days treatment. Thirty days of PGE2 alone treatment restored the bone mass in ovx rats to the level of sham-ovx rats, but the restored bone was partially lost by 90 days of treatment. Co-treatment for 30 days produced the same amount of bone mass in both sham-ovx and ovx rats as PGE2 alone did. However, unlike the PGE2 alone treated, co-treatment animals continued to form more bone for 90 days. The difference in tissue-level histomorphometry between co-treatment and PGE2 alone was that the former depressed the bone resorption and turnover. These findings indicated that the long-term administration of PGE2 alone cannot maintain or continue to add bone mass in ovx rats but that co-treatment of a PGE2 with an anti-resorptive or activation agent can resist the influence of the mechanostat induced bone loss as well as continue to add bone.

Fish mating experiment in space--what it aimed at and how it was prepared

The code name 'MEDAKA' was given to the fish experiment in the IML-2 (the second International Microgravity Laboratory), a Space-shuttle mission (STS-65) carried out in July 1994. Medaka is the Japanese name for a small fresh-water fish, Oryzias latipes. This experiment titled 'Mating behavior of the fish Medaka and development of their eggs in space' aimed to present data for designing the future fish-culture in space. The Medaka experiment accomplished its objectives to the point of 100%. The fish mated, laid eggs in space, and these eggs developed normally to hatching (coming out as a baby fish) under microgravity. Its success totally depended on selection of the four fish sent to space. This paper describes the aims of the IML-2 Medaka fish experiment and how it was prepared, together with a brief report on what were achieved in space.

Indomethacin inhibition of ossification induced by direct current stimulation

In this study, we sought to clarify the mechanism of ossification induced by direct current stimulation by analyzing changes in local blood flow and vascular permeability and by examining the involvement of chemical mediators. Changes in blood flow were studied with laser Doppler flowmetry, and vascular permeability was determined by microquantification. To examine the involvement of chemical mediators, we determined the effect on vascular permeability of histamine H1 and H2-receptor blockers and indomethacin. In addition, direct current stimulation was performed during administration of indomethacin to determine whether indomethacin inhibits electrically induced callus formation. Local blood flow remained unchanged in the control group and in the group receiving 5 microA of stimulation, but it increased in the groups receiving 10 and 50 microA. Vascular permeability increased in the 5 and 10 microA stimulation groups. This increase was not suppressed by histamine-receptor blockers, but it was suppressed by indomethacin. Two weeks of electrical stimulation without concomitant indomethacin treatment resulted in active callus formation around the needle electrode and in the vicinity of the endosteum; however, direct current stimulation during administration of indomethacin inhibited callus formation. The results suggest that these changes serve as microenvironmental factors that play an important role in the promotion of ossification and that a prostaglandin-mediated mechanism is involved in the promotion of ossification by direct current stimulation.

Comparison of operative results of lumbar disc herniation in manual laborers and athletes

The results of various surgical treatments for lumbar disc herniation in laborers and athletes were compared on the basis of the relative success of return to work and athletic activity. The rate of successful return to manual labor was the highest at 89% after spinal fusion, but no difference was observed between simple disc excision and percutaneous discectomy. Return to competitive sports was achieved at rate of 81% after percutaneous discectomy, and the time until return to sports activity was significantly shorter than after other procedures. In individuals whose lumbar region is expected to be subjected to great mechanical stress, it is important to take work needs and the special needs of athletes into consideration when selecting the surgical procedure.

Preoperative and postoperative magnetic resonance image evaluations of the spinal cord in cervical myelopathy

To evaluate the morphologic changes of the spinal cord in patients with cervical myelopathy due to cervical spondylosis and ossification of the posterior longitudinal ligament, the authors measured the thickness and signal intensity of the cervical cord with magnetic resonance imaging in healthy adults and patients with cervical myelopathy, and compared these findings. In patients with cervical myelopathy, the preoperative and postoperative magnetic resonance imaging findings were compared with the severity of myelopathy and postoperative results. In healthy adults, the anteroposterior diameter of the cervical cord was 7.8 mm at the C3 level and decreased at lower levels. In the patients with cervical myelopathy, the preoperative spinal anteroposterior diameter was significantly reduced at various levels corresponding to the stenosis site within the vertebral canal. In the group with ossification of the posterior longitudinal ligament, the minimal anteroposterior diameter of the cervical cord tended to decrease with increasing severity of myelopathy. However no relationship was observed between the two parameters in the cervical spondylotic myelopathy group. In the group with ossification of the posterior longitudinal ligament, surgical results were good when the postoperative anteroposterior diameter was increased, whereas in the cervical spondylotic myelopathy group there was no relationship between the two parameters. In the patients with myelopathy, a high intensity area was observed in about 40% of all patients before operation and about 30% after operation. However, the presence or absence of a high intensity area did not correlate with the severity of myelopathy or with surgical results in the group with ossification of the posterior longitudinal ligament and the cervical spondylotic myelopathy groups.

Changes with respect to time in the in vivo adsorption of plasma proteins onto artificial heart blood pumps

The distribution of adsorbed plasma proteins (albumin, IgG, and fibrinogen) on 10 artificial heart blood pumps coated with 2 segmented polyurethanes was evaluated quantitatively after long-term in vivo experiments with goats to determine how the adsorption of plasma proteins on the pumps was affected by the kinds of biomaterials used, and by the pumping duration. The adsorbed plasma proteins on the materials were determined quantitatively using the iodine-125 conjugated antibody method. Microscopically, the adsorbed plasma proteins were marked by the gold colloid conjugated antibody method, and analyzed using a field emission scanning electron microscope. The macroscopic results showed that: 1) the adsorbed plasma proteins on KP-13 were more evenly and finely distributed than those on Cardiothane; 2) with KP-13, the adsorption of IgG and albumin at the center of the pumps was significantly less than in the peripheral areas, and the adsorbed IgG and albumin decreased significantly as the pumping duration increased; 3) in contrast, the adsorbed fibrinogen increased significantly with time; and 4) with Cardiothane, the tendencies for adsorbed IgG and albumin to decrease, and for adsorbed fibrinogen to increase, were less significant than with KP-13. Microscopically, the gold colloids marking plasma proteins were found to not cover the whole of the surface, but were found scattered randomly or in clusters, with no relationship observed between the distributions of the three plasma proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

[Solid scintillator "Ready Cap" for measurement with a liquid scintillation counter--spectra and counting efficiencies for 15 different radionuclides]

"Ready Cap", a small plastic container coated with solid scintillator has recently been introduced (Beckman Instruments, Inc.). Pulse height spectra and counting efficiencies obtained with a liquid scintillator and Ready Cap using a liquid scintillator counter were compared for 15 different radionuclides. For radionuclides emitting low-energy beta-rays or characteristic X-rays, the spectra for Ready Cap shifted toward the higher energy side compared with the spectra for the liquid scintillator. This tendency was reversed for the nuclides emitting higher-energy beta-radiations (36Cl and 32P). Generally, counting efficiencies both in Ready Cap and in liquid scintillator increased with increase in the energy of beta- or X-rays. For some nuclides, Ready Cap gave higher counting efficiencies and for others it gave lower values than in the liquid scintillator. However, the differences were not large within each nuclide. The use of Ready Cap is recommended for measurements of radionuclides when liquid scintillation cocktails have no means of waste disposal under the present Japanese radioisotope regulation.

The circadian rhythm for the number and sensitivity of radiation-induced apoptosis in the crypts of mouse small intestine

Apoptosis is a mode of cell death involving nuclear pycnosis, cytoplasmic condensation and karyorrhexis. Changes in the number of apoptotic cells at various times (3-12 h) after a single dose of either 0.5 or 9.0 Gy given at 09.00, 21.00 or 03.00 h were studied in histological sections of small intestinal crypts of mice. The incidences of apoptosis were examined 3 or 6 h after irradiation at different times of day with different doses of gamma-rays ranging from 0.15 to 9.0 Gy. Survival curves were constructed from the dose-incidence curves for apoptosis, using the number of apoptotic cells after high doses (NM) as the maximum cell population size. The mean lethal doses (Do) for the dose range 0-0.5 Gy were calculated for each time of day. A circadian rhythm in both Do and NM values was detected, indicating that both the number and sensitivity of radiation-induced apoptosis were changing throughout the day. A possible explanation based on the cell-cycle states of the target cell population for apoptosis (presumably functional stem cells) was drawn. Most of the target cells were assumed to be in an extended G1 phase. Around 21.00 h a transition from G1 to S phase takes place in some of these cells (approximately seven or eight cells per whole crypt). The S phase then lasts till around 06.00 h. They may be at G2 and M around 06.00-09.00 h, and then they re-enter G1. The circadian rhythm for the number and sensitivity of the cells susceptible to apoptosis obtained in the present report agrees well with this pattern of cell-cycle phases of target cells.

Apoptosis (cell death) induced in mouse bowel by 1,2-dimethylhydrazine, methylazoxymethanol acetate, and gamma-rays

Apoptosis is a pattern of cell death involving nuclear pyknosis, cytoplasmic condensation, and karyorrhexis. The frequency of apoptosis after treatment with two colon carcinogens and radiation was studied in the crypts of five different portions of mouse bowel. When 1,2-dimethylhydrazine (DMH) was injected s.c., the earliest rise in apoptotic incidence after a high dose (200 mg/kg) was noted at 3 h in small intestine and at 6 h in large bowel. After i.p. administration of methylazoxymethanol (MAM) acetate, apoptotic cells were seen in large bowel after 3 h. When the plateau values attained after high doses of DMH were compared, many apoptotic cells were found in the lower part of the large bowel, whereas few such cells were observed in the small intestine and the upper part of the large bowel. This finding was reversed in the case of radiation-induced apoptosis. In the descending colon, a definite circadian rhythm in the apoptotic incidence was observed 6 h after injection of DMH or MAM acetate. Apoptosis showed a high incidence when these drugs were given between 2400 h and 0900 h, but a low incidence after administration between 1200 h and 2100 h. In the small intestine a rhythm was also noted for MAM acetate, but not significantly for DMH.

Cell death (apoptosis) in mouse intestine after continuous irradiation with gamma rays and with beta rays from tritiated water

Apoptosis is a pattern of cell death involving nuclear pycnosis, cytoplasmic condensation, and karyorrhexis. Apoptosis induced by continuous irradiation with gamma rays (externally given by a 137Cs source) or with beta rays (from tritiated water injected ip) was quantified in the crypts of two portions of mouse bowel, the small intestine and descending colon. The time-course change in the incidence of apoptosis after each type of radiation could be explained on the basis of the innate circadian rhythm of the cells susceptible to apoptotic death and of the excretion of tritiated water (HTO) from the body. For 6-h continuous gamma irradiation at various dose rates (0.6-480 mGy/h) and for 6 h after injection of HTO of various radioactivities (0.15-150 GBq per kg body wt), the relationships between dose and incidence of apoptosis were obtained. Survival curves were then constructed from the curves for dose vs incidence of apoptosis. For the calculation of the absorbed dose from HTO, the water content both of the mouse body and of the cells was assumed to be 70%. One megabecquerel of HTO per mouse (i.e., 40 MBq/kg body wt) gave a dose rate of 0.131 mGy/h. The mean lethal doses (D0) were calculated for gamma rays and HTO, and relative biological effectiveness values of HTO relative to gamma rays were obtained. The D0 values for continuous irradiation with gamma rays were 210 mGy for small intestine and 380 mGy for descending colon, and the respective values for HTO were 130 and 280 mGy, indicating the high radiosensitivity of target cells for apoptotic death. The relative biological effectiveness of HTO relative to 137Cs gamma rays for cell killing in both the small intestine and the descending colon in the mouse was 1.4-2.1.

Circadian rhythms in the incidence of apoptotic cells and number of clonogenic cells in intestinal crypts after radiation using normal and reversed light conditions

Variations in the number of radiation-induced morphologically dead or dying cells (apoptotic cells) in the crypts in the small intestine of the mouse have been studied throughout a 24-h period under a normal light regimen (light on, 07.00-19.00 h; light off, 19.00-07.00 h). A clear circadian rhythm was displayed in the apoptotic incidence 3 or 6 h after irradiation for each gamma-ray dose studied (range 0.14-9.0 Gy). The most prominent circadian rhythm was obtained after 0.5 Gy. The peak time of day for inducing apoptosis was 06.00-09.00 h, and the trough occurred at 18.00-21.00 h. Some mice were also transferred to a room with the light cycle reversed, and were irradiated on different days after the transfer. The apoptosis induced by 0.5 Gy or 9.0 Gy, or the number of surviving crypts (microcolonies) after 11.0 Gy or 13.0 Gy was examined. The transition point for reversal (i.e. the switch time from the normal-light pattern to the reversed-light pattern) of the circadian rhythm in apoptosis (after 0.5 Gy) occurred 7 days after the transfer and the rhythm was reversed by 14 days. The rhythm for crypt survival (i.e. for clonogenic cell radiosensitivity) was disturbed on 1 day and the transition point for reversal occurred 3 days after the transfer. The rhythm became reversed by 7 days. These observations are discussed in relation to the identity of clonogenic cells, (functional) stem cells, proliferating transit cells and the cells sensitive to small doses of radiation (i.e. hypersensitive cells) in the crypt.

Further studies on the response of intestinal crypt cells of different hierarchical status to eighteen different cytotoxic agents

Adult male mice were treated with one or two different doses of each of 18 different cytotoxic agents. They were sampled at various times (3-12h) thereafter, and the spatial distributions of cell death in the small intestinal crypts were studied. Dead or dying cells or cells carrying dead cell fragments were examined histologically, and all of these were recorded (for convenience as apoptotic fragments), relative to the cell position in the crypt. Thus, distributions of apoptotic fragments against cell position were determined. A regression analysis of the data obtained at different times after administration of each agent was undertaken and the position of the median of the spatial distribution of presumptive target cells was deduced for each cytotoxic agent. The accuracy of this median value was determined to be +/- 0.5 cell positions. From these median values, the different cytotoxic agents could be divided roughly into three groups: [3H]thymidine, isopropyl-methane-sulphonate, gamma-rays, bleomycin and adriamycin all have their median values (susceptible cells) at cell positions 4 to 6; bischlorethylnitrosourea, actinomycin D, cyclophosphamide and cycloheximide at cell positions 6-8; mechlorethamine, triethylenethiophosphoramide, vincristine, 5-fluorouracil, hydroxyurea and methotrexate at cell positions 8-11. The position of these medians was considered in relation to the killing of clonogenic cells. Preliminary studies on the distributions of dead cells after myleran, cis-platinum and heat (hyperthermia) were also reported. There is a general tendency for antibiotics and radiation to attack the lower cell positions in the crypt. Alkylating agents on the other hand have a somewhat broad spectrum of action. Antimetabolites and a microtubule dissociating agent act on higher cell positions. No difference could be detected between two different forms (sources) of actinomycin D. The changes in the yields of apoptotic and mitotic cells with time and the migration velocities of cells in the crypts carrying apoptotic fragments after exposure to cytotoxics are also presented.

The production of cloned fish in the medaka (Oryzias latipes)

The measurement of cellular DNA content by DNA microfluorometry revealed that medaka embryos that were fertilized with normal sperm and exposed to heat shock (41 degrees C for 3 min) or hydrostatic pressure (700 kg/cm2 for 10 min) at 85-95 min after insemination were tetraploid. Embryos fertilized with normal sperm and exposed to heat shock (41 degrees C for 2 min at 2-3 min after insemination) were triploid. These results suggest that heat shock or hydrostatic pressure at 85-95 min after insemination arrests the first cleavage, while heat shock at 2-3 min after insemination arrests the second meiotic division. Medaka clones have been produced by the following method: Eggs from orange-red or variegated variety were activated by UV-irradiated, genetically impotent sperm of wild-type fish (UV sperm). The haploid eggs obtained were diploidized by preventing the first cleavage with heat shock or hydrostatic pressure to produce homozygous females. Each of the two homozygous females was mated with vasectomized male in isotonic balanced salt solution to collect unfertilized eggs. The collected eggs were activated with UV sperm and converted from haploid to diploid by arrest of the second meiotic division with heat shock. Hatched fry of each homozygous diploid (all females) were fed with a methyltestosterone-containing diet (40 micrograms/gm diet) to produce sex-reversed males, which were mated with brood females, and thus two cloned lines were obtained.

The re-establishment of hypersensitive cells in the crypts of irradiated mouse intestine

Within 3-6 h of small doses of radiation (gamma-rays) the number of dead cells (apoptotic cells) in the crypts of the small intestine reaches peak values. These return to normal levels only after times later than 1 day. After higher doses elevated levels of cell death persist for longer times. The dead cells first occur most frequently at the lower positions of the crypt (median value for the distribution of apoptotic fragments is about cell position 6). At later times more dead cells are observed at higher positions. Two doses of radiation separated by various time intervals have been used to investigate when after irradiation the cell population susceptible to acute cell death is re-established. Dead cells were scored 3 or 6 h after the second dose. The yield of dead cells after two doses represents the sum of the dead cells produced by, and persisting from, the first dose and new apoptotic cells induced by the second dose. Since the temporal and dose-dependence aspects of the dead-cell yield after the first dose alone is known, the additional dead cells attributable to the second dose alone can be determined by subtraction. Within 1-2 days of small doses (0.5 Gy) the sensitive cells, recognized histologically as apoptotic cells, are re-established at the base of the crypt (around cell position 6). After higher doses (9.0 Gy) they are not re-established until about the fourth day after irradiation. Even in the enlarged regenerating crypts the sensitive cells are found at the same position at the crypt base. It has been estimated that the crypt contains five or six cells that are susceptible to low doses (0.5 Gy) (hypersensitive cells) and up to a total of only seven or eight susceptible cells that can be induced by any dose to enter the sequence of changes implicit in apoptosis. Between 4 and 10 days after an initial irradiation of 9.0 Gy the total number of susceptible cells increased from seven to eight to about 10 to 13 per crypt.

The recruitability and cell-cycle state of intestinal stem cells

Evidence is presented which suggests that the crypts of the small intestine contain at least two discrete but interdependent classes of stem cells, some with discrete cell kinetic properties and some with discrete radiation responses or radiosensitivities. Very low doses of X rays or gamma rays, or neutrons, kill a few cells in the stem cell regions of the crypt in a sensitive dose-dependent manner. Similar doses generate several different cell kinetic responses within either the clonogenic fraction or the cells at the stem cell position within the crypt. The cell kinetic responses range from apparent recruitment of G0 clonogenic cells into cycle, to a marked shortening of the average cell cycle of the cells at the stem cell position. It is suggested that the cell kinetic changes may be the consequence of the cell destruction.

Response of intestinal cells of differing topographical and hierarchical status to ten cytotoxic drugs and five sources of radiation

The spacial distribution of cell death among the epithelial cells lining the adult mammalian small intestinal mucosa at various times after a range of doses of 10 different drugs as well as after internal or external irradiation (beta particles from tritium, gamma- and X-rays and neutrons) has been recorded. Cell death, expressed as pycnosis or apoptosis, has been recorded for each cell position up the side of the crypts of the small intestine. The results, in the form of distributions of dead cells at each cell position, show that each of the various cytotoxic agents tends to act preferentially over a characteristic small range of cell positions. Since cell position is likely to be related to hierarchical cell position within a family tree or cell lineage, each agent tends to act with greatest efficiency on cells at a particular position within the lineage. Adriamycin and the various forms of radiation tend to kill cells preferentially at cell position 4-5 i.e. on cells very early in the lineage, probably stem cells. Isopropyl-methane-sulphonate, nitrogen mustard and possibly Actinomycin-D act on cell position 6-7, while 5-fluorouracil, Myleran, cyclophosphamide, and cycloheximide tend to kill cells at cell position 7-9. Vincristine and hydroxyurea are the 2 agents that exhibit a specificity for cells highest up the crypt, i.e. latest in transit population of the cell lineage by acting on cell positions 10 or 11. The data also suggest that normal healthy cells continue to migrate up the crypt and onto the villus in spite of considerable cell death and reduced cell production.

Hertwig effect caused by UV-irradiation of sperm of Oryzias latipes (teleost) and its photoreactivation

When sperm of the fish Oryzias latipes were irradiated with ultraviolet light and allowed to fertilize normal eggs, the so-called "Hertwig effect" was observed, with a dose-dependent decrease in survival rate at low doses (0-27 J . m-2) but a better survival rate at higher dose ranges. Illumination with visible light after fertilization (10-70 min after insemination) showed the existence of photoreactivation (PR), demonstrating that pyrimidine dimers are a lesion in sperm DNA that is mainly responsible for the UV-caused Hertwig effect. Genetic analysis, in which sperm from a wild-type of this fish was used, showed that, after UV-irradiation at the high dose range, male nuclei did not participate in embryonic development (a gynogenetic haploid condition). Embryos having only a maternal set of chromosomes could develop no further than stage 27. Only the visible light during the early part (until around 20-30 min after insemination, at 25 degrees C) of the single-cell stage was effective for PR; illumination thereafter was not.