Effect of low-level laser therapy on seminiferous epithelium: a systematic review of in vivo studies.

Laser therapy has proved effective in the treatment of different tissue injuries but little is known about its effect on the testis. The aim of this review was to synthesize research on the in vivo effect of low-level laser therapy on the seminiferous epithelium. A search was performed in the PubMed/Medline, Scopus, Web of Science, and LILACS databases. The initial search retrieved 354 references, and five articles that met the eligibility criteria were selected. In general, the studies showed that laser therapy exerted a positive effect on the germ cell population; however, there was considerable variation in the laser parameters, as well as in the experimental models and methods of tissue analysis used. In conclusion, further studies determining the biostimulation parameters of laser therapy in the testis are necessary in order to provide a basis for the possible application of this technique to the restoration of the human seminiferous epithelium and consequent treatment of some male reproductive disorders.

[Comparative analysis of ionizing radiation and xenobiotics influence on spermatogenic epithelium and dominant lethal mutations output in laboratory animals].

The study covered state of spermatogenic epithelium and dominant lethal mutations output in mice of BALB/c and CBA lines, subjected to total gamma-irradiation and in Wistar rats after intraperitoneal injection of potassium bichromate (K2Cr2,O7) in small and sublethal doses. The BALB/c line mice under low irradiation dose (0.25 Gy) demonstrated stimulation effect on spermatogenic epithelium, but in the CBA line mice no such effect was seen. Both mice lines under irradiation of 0.25 Gy and 1.0 Gy demonstrated increase in pathologic sperm counts and in percentage ofpreimplantation embryonal death. In rats, injection of potassium bichromate in doses of 0.028 mg/kg and 2.8 mg/kg increased number of micronuclear spermatids, larger pathologic sperm counts and percentage of postimplantation deaths. Thus, lower general embryonal deaths under radiation exposure is due to preimplantation embryonal deaths, under exposure to 6-valent chromium--is due to postimplantation losses.

Protection of spermatogenesis against gamma ray-induced damage by granulocyte colony-stimulating factor in mice.

The radioprotective effects of granulocyte colony-stimulating factor (GCSF) were further investigated with respect to the testicular system. Recombinant human GCSF (100 µg kg(-1) body weight/day) was administrated to male C3H/HeN mice by subcutaneous injection for three consecutive days before pelvic irradiation (5 Gy) and histopathological parameters were assessed at 12 h and 21 days post-irradiation (pi). The GCSF protected the germ cells from radiation induced- apoptosis (P < 0.01 vs. irradiated group at 12 h pi). GCSF remarkably attenuated radiation-induced reduction in testis weight, seminiferous tubular diameter, seminiferous epithelial depth and sperm head count in the testes (P < 0.05 versus irradiated group at 21 days pi). Repopulation index and stem cell survival index of the seminiferous tubules were increased in the GCSF-treated group when compared with the radiation group (P < 0.01). The frequency of abnormal sperm in the GCSF group was lower than that in the irradiated group at 21 days pi (P < 0.01). The decrease in the sperm count and in sperm liability in the epididymis caused by irradiation was counteracted by GCSF. The present study suggests that GCSF protects from radiation-induced testicular dysfunction via an anti-apoptotic effect and recovery of spermatogenesis.

Selection against spermatozoa with fragmented DNA after postovulatory mating depends on the type of damage.

BACKGROUND: Before ovulation, sperm-oviduct interaction mechanisms may act as checkpoint for the selection of fertilizing spermatozoa in mammals. Postovulatory mating does not allow the sperm to attach to the oviduct, and spermatozoa may only undergo some selection processes during the transport through the female reproductive tract and/or during the zona pellucida (ZP) binding/penetration. METHODS: We have induced DNA damage in spermatozoa by two treatments, (a) a scrotal heat treatment (42 degrees C, 30 min) and (b) irradiation with 137Cs gamma-rays (4 Gy, 1.25 Gy/min). The effects of the treatments were analyzed 21-25 days post heat stress or gamma-radiation. Postovulatory females mated either with treated or control males were sacrificed at Day 14 of pregnancy, and numbers of fetuses and resorptions were recorded. RESULTS: Both treatments decreased significantly implantation rates however, the proportion of fetuses/resorptions was only reduced in those females mated to males exposed to radiation, indicating a selection favoring fertilization of sperm with unfragmented DNA on the heat treatment group. To determine if DNA integrity is one of the keys of spermatozoa selection after postovulatory mating, we analyzed sperm DNA fragmentation by COMET assay in: a) sperm recovered from mouse epididymides; b) sperm recovered from three different regions of female uterine horns after mating; and c) sperm attached to the ZP after in vitro fertilization (IVF). Similar results were found for control and both treatments, COMET values decreased significantly during the transit from the uterine section close to the uterotubal junction to the oviduct, and in the spermatozoa attached to ZP. However, fertilization by IVF and intracytoplasmatic sperm injection (ICSI) showed that during sperm ZP-penetration, a stringent selection against fragmented-DNA sperm is carried out when the damage was induced by heat stress, but not when DNA fragmentation was induced by radiation. CONCLUSION: Our results indicate that in postovulatory mating there is a preliminary general selection mechanism against spermatozoa with low motility and fragmented-DNA during the transport through the female reproductive tract and in the ZP binding, but the ability of the ZP to prevent fertilization by fragmented-DNA spermatozoa is achieved during sperm-ZP penetration, and depends on the source of damage.

Role of L-carnitine in the prevention of seminiferous tubules damage induced by gamma radiation: a light and electron microscopic study.

The present study, we hypothesized that L-carnitine can minimize germ-cell depletion and morphological features of late cell damage in the rat testis following gamma (gamma)-irradiation. Wistar albino male rats were divided into three groups. Control group received physiological saline 0.2 ml intraperitoneally (i.p.), as placebo. Radiation group received scrotal gamma-irradiation of 10 Gy as a single dose plus physiological saline. Radiation + L-carnitine group received scrotal gamma-irradiation plus 200 mg/kg i.p. L-carnitine. L-carnitine starting 1 day before irradiation and 21 days (three times per week) after irradiation. Testis samples of the all groups were taken at day 21, 44 and 70 post-irradiation. All samples were processed at the light and electron microscopic levels. Morphologically, examination of gamma-irradiated testis revealed presence of marked disorganization and depletion of germ cells, arrest of spermatogenesis, formation of multinucleated giant cells, and vacuolization in the germinal epithelium. The type and extent of these changes varied at different post-treatment intervals. The damage was evident at the 21st day and reached maximum level by the 44th day. By day 44 post-irradiation, the changes were most advanced, and were associated with atrophied seminiferous tubules without germ cells, the increase in the number and size of vacuolizations in germinal epithelium, and the absent multinucleated giant cells due to spermatids had completely disappeared. The increase in nucleus invaginations, the dilatation of smooth endoplasmic reticulum cysternas and the increase in the number and size of lipid droplets in the Sertoli cells were determined at the electron microscopic level. In conclusion, L-carnitine supplementation during the radiotherapy would be effective in protecting against radiation-induced damages in rat testis, and thereby may improve the quality of patient's life after the therapy.

Depletion of the spermatogonia from the seminiferous epithelium of the rhesus monkey after X irradiation.

In unirradiated testes large differences were found in the total number of spermatogonia among different monkeys, but the number of spermatogonia in the right and the left testes of the same monkey appeared to be rather similar. During the first 11 days after irradiation with 0.5 to 4.0 Gy of X rays the number of Apale spermatogonia (Ap) decreased to about 13% of the control level, while the number of Adark spermatogonia (Ad) did not change significantly. A significant decrease in the number of Ad spermatogonia was seen at Day 14 together with a significant increase in the number of Ap spermatogonia. It was concluded that the resting Ad spermatogonia are activated into proliferating Ap spermatogonia. After Day 16 the number of both Ap and Ad spermatogonia decreased to low levels. Apparently the new Ap spermatogonia were formed by lethally irradiated Ad spermatogonia and degenerated while attempting to divide. The activation of the Ad spermatogonia was found to take place throughout the cycle of the seminiferous epithelium. Serum FSH, LH, and testosterone levels were measured before and after irradiation. Serum FSH levels already had increased during the first week after irradiation to 160% of the control level. Serum LH levels increased between 18 and 25 days after irradiation. Serum testosterone levels did not change at all. The results found in the rhesus monkey are in line with those found in humans, but due to the presence of Ad spermatogonia they differ from those obtained in non-primates.

Repopulation of the seminiferous epithelium of the rhesus monkey after X irradiation.

Repopulation of the seminiferous epithelium became evident from Day 75 postirradiation onward after doses of 0.5, 1.0, and 2.0 Gy of X rays. Cell counts in cross sections of seminiferous tubules revealed that during this repopulation the numbers of Apale (Ap) spermatogonia, Adark (Ad) spermatogonia, and B spermatogonia increased simultaneously. After 0.5 Gy the number of spermatogonia increased from approximately 10% of the control level at Day 44 to 90% at Day 200. After 1.0 and 2.0 Gy the numbers of spermatogonia increased from less than 5% at Day 44 to 70% at Days 200 and 370. The number of Ad and B spermatogonia, which are considered to be resting and differentiating spermatogonia, respectively, already had increased when the number of proliferating Ap spermatogonia was still very low. This early inactivation and differentiation of a large part of the population of Ap spermatogonia slows down repopulation of the seminiferous epithelium of the primates. By studying repopulating colonies in whole mounts of seminiferous tubules various types of colonies were found. In colonies consisting of only A spermatogonia, 40% of the A spermatogonia were found to be of the Ad type, which indicates that even before the colony had differentiated, 40% of the A spermatogonia were inactivated into Ad. Differentiating colonies were also found in which one or two generations of germ cells were missing. In some of those colonies it was found that the Ap spermatogonia did not form any B spermatogonia during one or two cycles of the seminiferous epithelium, while in other colonies all Ap spermatogonia present had differentiated into B spermatogonia. This indicates that the differentiation of Ap into B spermatogonia is a stochastic process. When after irradiation the density of the spermatogonia in the epithelium was very low, it could be seen that the populations of Ap and Ad spermatogonia are composed of clones of single, paired, and aligned spermatogonia, which are very similar to the clones of undifferentiated spermatogonia in non-primates.

Variation in the sensitivity of the mouse spermatogonial stem cell population to fission neutron irradiation during the cycle of the seminiferous epithelium.

Dose-response studies of the radiosensitivity of spermatogonial stem cells in various epithelial stages after irradiation with graded doses of fission neutrons of 1 MeV mean energy were carried out in the Cpb-N mouse. These studies on the stem cell population in stages IX-XI yielded simple exponential lines characterized by an average D0 value of 0.76 +/- 0.02 Gy. In the subsequent epithelial stages XII-III, a significantly lower D0 value of 0.55 +/- 0.02 Gy was found. In contrast to the curves obtained for stem cells in stages IX-III, the curves obtained in stages IV-VIII indicated the presence of a mixture of radioresistant and radiosensitive stem cells. In stage VII, almost no radioresistant stem cells appeared to be present and a D0 value for the radiosensitive stem cells of 0.22 +/- 0.01 Gy was derived. Previously, data were obtained on the size of colonies (in number of spermatogonia) derived from surviving stem cells. Combining these data with data from the newly obtained dose-response curves yielded the number of stem cells, per stage and with the specific radiosensitivities, present in the control epithelium. In stages IX-XI, there are approximately 6 stem cells per 1000 Sertoli cells with a radiosensitivity characterized by a D0 of 0.76 Gy, which corresponds to one-third of the As population in these stages. (The As spermatogonia are presumed to be the stem cells of spermatogenesis.) IN stages XII-III, there are approximately 12 stem cells per 1000 Sertoli cells with a radiosensitivity characterized by a D0 of 0.55 Gy, which roughly equals the number of A single spermatogonia in these stages. These calculations could not be made for stages IV-VIII since no simple exponential lines were obtained for these stages. In view of the pattern of the proliferative activity of the spermatogonial stem cells during the epithelial cycle, it appears that the stem cell population is most radiosensitive during the period when the majority of these cells are in G0 phase, most resistant when the cells are stimulated again into proliferation, and of intermediate sensitivity during active proliferation.

Nonrandom distribution of mouse spermatogonial stem cells surviving fission neutron irradiation.

Colony formation by surviving spermatogonial stem cells was investigated by mapping pieces of whole mounted tubuli at intervals of 6 and 10 days after doses of 0.75 and 1.50 Gy of fission neutron irradiation. Colony sizes, expressed in numbers of spermatogonia per colony, varied greatly. However, the mean colony size found in different animals was relatively constant. The mitotic indices in large and small colonies and in colonies in different epithelial stages did not differ significantly. This finding suggests that size differences in these spermatogenic colonies are not caused by differences in growth rate. Apparently, surviving stem cells start to form colonies at variable times after irradiation. The number of colonies per unit area varied with the epithelial stages. Many more colonies were found in areas that during irradiation were in stages IX-III (IX-IIIirr) than in those that were in stages IV-VII (IV-VIIirr). After a dose of 1.50 Gy, 90% of all colonies were found in areas IX-IIIirr. It is concluded that the previously found difference in repopulation after irradiation between areas VIII-IIIirr and III-VIIIirr can be explained not by differences in colony sizes and/or growth rates of the colonies in these areas but by a difference in the number of surviving stem cells in both areas. In area XII-IIIirr three times more colonies were found after a dose of 0.75 Gy than after a dose of 1.50 Gy. In area IV-VIIirr the numbers of colonies differed by a factor of six after both doses. This finding indicates that spermatogonial stem cells are more sensitive to irradiation in epithelial stages IV-VII than in stages XII-III. In control material, spermatogonia with a nuclear area of 70-110 micron2 are rare. However, especially 6 days after irradiation, single cells of these dimensions are rather common. These cells were found to lie at random over the tubular basement membrane with no preference for areas with colonies. It is concluded that the great majority of these cells were not or do not derive from surviving stem cells. These enlarged cells most likely represent lethally injured cells that will die or become giant cells (nuclear area greater than 110 micron2).

A small-scale anatomic model for testicular radiation dosimetry for radionuclides localized in the human testes.

UNLABELLED: The testis is a radiosensitive tissue. It contains a large number of lobules, which in turn are composed of convoluted seminiferous tubules. The epithelium inside each tubule consists of a complex mosaic of supporting cells and germ cells of different sizes and degrees of maturation. These cells are known to have diverse sensitivity to radiation, those with the highest sensitivity being the spermatogonia, which form part of the basal cell layer, and those with the lowest sensitivity being the mature sperm cells closest to the lumen of the tubule. For many years, the internal dosimetry community has discussed the need for improvements to bring about more detailed, cell-level testicular dosimetry. This paper presents a small-scale dosimetry model for calculation of S factors for several different source-target configurations within the testicular tissue. METHODS: A model of the testis was designed in which the lobules were approximated by a cross-section of seminiferous tubules arranged in a hexagonal pattern, with interstitial tissue between them. The seminiferous tubules were divided into concentric layers representing spermatogenic development in the seminiferous epithelium. S factors were calculated for electrons, photons, α-particles, and for (18)F, (90)Y, (99m)Tc, (111)In, (125)I, (131)I, (177)Lu, and (211)At using Monte Carlo simulations. RESULTS: For electrons with low energies the range was small, compared with the diameter of the seminiferous tubules, resulting in high energy deposition close to the source, whereas for higher electron energies more uniform energy deposition was seen, as expected. The same trend was seen for low-energy photons, whose mean free paths are small, compared with the diameter of the seminiferous tubules, resulting in high energy deposition close to the source, whereas for higher photon energies the location of the activity in the testis is less important. CONCLUSION: The model presented in this paper is a simplification of the organized chaos that constitutes the structure of the actual testis. However, it provides a relevant, small-scale anatomic model to help us understand the significance of the heterogeneity of radioactivity in this important radiosensitive tissue.

Effects of phototherapy on newborn rat testicles.

Phototherapy is the most widespread treatment for lowering bilirubin concentration in neonates. In the routine, phototherapy has some side effects including skin eruption, fluid loss, abdominal distention, mild hemolysis and mild thrombocytopenia. The aim of the study was to investigate the possible mutagenic and gametocidal side effects of 72 h continuous phototherapy on the rat testicle. We observed decreases in spermatogonia numbers per tubule (S/T values), tubular fertilization index (TFI) and sperm sertoli cell index (SSCI), which are the most reliable methods in estimating future fertility potential, due to sensitivity to phototherapy. The differences between study and control groups for S/T, TFI and SSCI values were statistically significant (p = 0.008, p = 0.02 and p = 0.004, respectively). There were significant differences in seminiferous tubule diameters between the control and study groups (p < 0.005), but no significant difference in DNA index values between the control (0.66 +/- 0.12) and study (0.59 +/- 0.05) groups (p > 0.05). As a conclusion, phototherapy seems to have some side effects on the newborn rat testicle. Further studies with larger groups, designed for investigation of the effects of phototherapy on seminiferous tubules, may give more beneficial results.

In vivo study to evaluate the protective effects of amifostine on radiation-induced damage of testis tissue.

OBJECTIVE: To investigate the early protective effects of amifostine against radiation-induced damage on rat testis tissue. METHODS: Eighty adult male Wistar rats were randomized to 4 groups: Saline solution was given to group A for control, 200 mg/kg amifostine (WR-2721) to group B, a single fraction of 6 Gy local irradiation to testes in group C and 200 mg/kg amifostine 15-30 min before 6 Gy testicular irradiation to group D. Animals were sacrificed 3 weeks after treatment and their testes were removed for macroscopic, microscopic and ultrastructural histopathological examination. RESULTS: The weights, widths and lengths of testes in the last 3 groups had decreased significantly when compared with the control group, but the decrease in widths after irradiation was found to be significantly less only in the amifostine plus radiation group. There was a significant reduction of testis weights in relation to the individual body weights in the irradiated testes compared with the other groups (p < 0.005), while there was no significant change of testis weight/total body weight ratio in amifostine plus irradiation group. Spermatogonium A and primary spermatocyte counts were also less in the treatment groups, and primary spermatocyte numbers were significantly higher in amifostine plus radiation group when compared with radiation alone group (p < 0.005). Pretreatment with amifostine reduced the decrease of primary spermatocyte counts by a factor of 1.28. Electron microscopic analysis did not show any cytotoxic effect of amifostine alone, and furthermore, ultrastructural findings were normal with the addition of amifostine prior to irradiation, though there was damage in the radiation exposure group. CONCLUSION: Amifostine when given alone by itself appears to cause adverse alterations in testis tissue; however, it has a radioprotective effect on spermiogenetic cells when used prior to radiation.

Quantitative and qualitative changes of the seminiferous epithelium induced by Ga. Al. As. (830 nm) laser radiation.

BACKGROUND AND OBJECTIVES: Low level laser radiation stimulates both nucleic acid synthesis and cellular proliferation in E. coli, Hela tumor cells, fibroblasts, lymphocytes, and thyroid cells. It has been introduced as a therapeutic modality; nevertheless few studies have been carried out to determine the effects of laser radiation on the testes or spermatogenesis. The aim of this study was to determine the quantitative and qualitative changes of the seminiferous epithelium after Ga. Al. As. (830 nm) laser radiation. STUDY DESIGN/MATERIALS AND METHODS: The left testes of Sprague-Dawley rats were daily exposed to laser light for 15 days; so the cumulative doses used 28.05 and 46.80 J/cm(2) in two experimental groups. Sampling carried out 24 hours after the last treatment and samples were processed for LM and TEM study. RESULTS: The number of germ cells specially the pachytene spermatocytes and elongated spermatids increased after 28.05 J/cm(2) laser radiation. Ultrastructural features of germ and Sertoli cells in this group were similar to that of control; while laser irradiation at 46.80 J/cm(2) had a destructive effect on the seminiferous epithelium such as dissociation of immature spermatids and evident ultrastructural changes in them. CONCLUSIONS: The findings confirmed the existence of a biostimulatory threshold of applied laser energy and the importance of determining it for clinical applications. Moreover, it was revealed that low doses of laser light have a biostimulatory effect on the spermatogenesis and may provide benefits to the patients with oligospermia and azoospermia.

[Quantitative characteristics of radiation injury of the spermatogenic epithelium and the rate of its recovery after exposure to fast neutrons and gamma-radiation]. / Kolichestvennaia kharakteristika radiatsionnogo porazheniia v spermatogennom épitelii i skorosti ego vosstanovleniia pri vozdeistvii bystrykh neitronov i gamma-izlucheniia.

The paper submits the results of studies on the kinetics of spermatogenous epithelium cell number after exposure to fast neutrons (60-300 cGy) and gamma-radiation (200-600 cGy). It was shown that a relative decrease in the quantity of spermatocytes is determined by an exponential dose-response curve with D0 of 35 and 120 cGy for neutrons and gamma-radiation respectively. For spermatides and spermatozoa a single D0 value of 20 and 55 cGy was obtained for neutrons and gamma-radiation respectively. As the radiation dose increases the recovery process in the epithelium is substantially decelerated. The equation T1/2 = T1/2(0)e0.0009D well describes the dependence of the half-recovery period T1/2 upon the equivalent dose.

Response of the seminiferous epithelium to scattered radiation in seminoma patients.

Semen and blood samples were obtained, at 3-month intervals over 12 to 28 months, from patients who underwent subdiaphragmal radiation after orchidectomy for seminoma testis. Before radiotherapy a mean (+/- SE) semen volume of 4.7 +/- 0.5 ml, a mean sperm count of 44.4 +/- 13.5 x 10(6)/ml, a mean percentage of motile cells of 20.3 +/- 5.2, a mean percentage of morphologically normal spermatozoa of 13.4 +/- 5.4, a mean percentage of swollen sperm of 39.6 +/- 7.4, and a mean serum follicle-stimulating hormone (FSH) value of 8.3 +/- 1.2 mIU/ml was found. The mean testicular dose from scatter was 62 +/- 5 cGy (range, 34 to 95 cGy). Sperm counts between 0 and 2.75 x 10(6)/ml were seen at 6.8 +/- 0.6 months and recovery to values greater than 2.25 x 10(6)/ml at 11.8 +/- 0.8 months after the start of radiation. Peak FSH values of 19.2 +/- 1.6 mIU/ml were obtained at 6.7 +/- 0.9 months after the start of irradiation. After recovery mean semen volume was 3.9 +/- 0.4 ml, mean sperm count 34.6 +/- 5.6 x 10(6)/ml, the mean percentage of motile cells 42.5 +/- 6.0, the mean percentage of swollen sperm 58.7 +/- 6.8, and the mean percentage of spermatozoa with normal morphology 23.4 +/- 5.1. Only motility was significantly different (P less than 0.01) from pretreatment values. The elevation of FSH values with time after start of radiotherapy reflected the toxicity to spermatogenesis but no correlation was found between peak FSH levels and scattered radiation dose. Also, neither the time from start of radiotherapy to sperm count nadir or recovery nor the time to peak FSH levels was significantly correlated with radiation dose.

Response of the seminiferous epithelium of the mouse exposed to low dose high energy (HZE) and electromagnetic radiation.

This study was undertaken to observe the response of a rapidly dividing cell population (spermatogonial) to Helium and Argon ions as compared to x-rays. Low doses (below 100 rads) were used to more nearly simulate radiation encountered during space missions. The methods used proved compatible for both light and electron microscope studies. The average relative biological effectiveness (RBE) for Helium ions is 1, while Argon is twice as effective in killing spermatogonial cells. Part of this mixed population of cells exhibits a higher sensitivity to radiation below 15 rads. Quantitation of the radiation effects by counting the necrotic cells is not feasible because of their rapid removal, therefore all measurements were done using the surviving fraction (S/So) of spermatogonial cells.

Comparative investigations on cytogenetic effects of X-irradiation on the germinal epithelium of male mice and Chinese hamsters.

In one short-term-experiment and one long-term-experiment spermatogonia of mice and Chinese hamsters were compared for their sensitivity of X-ray induced chromosome aberrations. Short-term-experiment: Six hours after varying doses of X-rays the spermatogonia of both species were analysed and the number of induced chromatid breaks determined. At the dose range from 25-125 R the number of induced chromatid breaks per cell per roentgen is 0.01 in mice. In Chinese hamsters this value is 0.0072. The frequencies of chromatid breaks were studied in both species after a single dose of 100 R until 48 h p.i. The frequency in mice decreased more slowly than in hamster spermatogonia. After 12 h p.i. the ratio breaks in mice cells: breaks in hamster cells was 3.5:1, after 24 h this ratio was 5.2:1 after 48 h both frequencies were on the same level. Long-term-experiment: Analysis of spermatogonia and primary spermatocytes has been done 5 weeks after irradiation of the mice and 2, and 4 months after irradiation of the Chinese hamsters. The number of observed reciprocal translocations turned out to be higher in spermatogonial mitoses than in diakinesis-metaphases I in each animal. The conclusion is drawn for mice that a selection against abnormal cells is taking place already during pre-meiosis. In hamster pre-meiosis, the results are only indicative for a similar effect.

Continuous gamma-irradiation of rats: dose-rate effect on loss and recovery of spermatogenesis.

Male Sprague Dawley rats were continuously irradiated at a dose-rate of either 5 or 7 cGy/day, up to a total dose of 900 cGy. Changes in spermatogenesis with irradiation and the recovery of the testis during 33 weeks after irradiation were studied. No clear dose-rate effect with testicular weight occurred. During the irradiation time, increased dose and dose-rate induced a decrease in A spermatogonia and preleptotene spermatocyte number. In our experimental conditions germ cell production did not plateau, as shown by the increasing number of tubular cross sections devoid of germ cells beyond 500 cGy. The recovery of seminiferous epithelium occurred essentially within nine weeks. It was not dose-rate dependent and was still incomplete after 33 weeks. This lack of recovery might be due to limited compensatory division ability of the stem cells. Clusters of Sertoli cells were observed in the lumen of the seminiferous tubules; impaired function of these cells could also prevent the complete recovery of the seminiferous epithelium. By 16 weeks after the end of irradiation 67% of 5 cGy/day irradiated rats and 34% of 7 cGy/day irradiated rats recovered fertility.