Use of urinary renal biomarkers to evaluate the nephrotoxic effects of melamine or cyanuric acid in non-pregnant and pregnant rats

Although traditional assessments of renal damage detect loss of kidney function, urinary renal biomarkers are proposed to indicate early changes in renal integrity. The recent adulteration of infant formula and other milk-based foods with melamine revealed a link between melamine ingestion and nephropathy. Thus, the effects of melamine and related analogs (e.g., cyanuric acid) should be assessed in other potentially sensitive groups. We evaluated whether urinary Kim-1, clusterin, and osteopontin could detect the effects of high doses of melamine or cyanuric acid in pregnant and non-pregnant female rats gavaged with 1000 mg/kg bw/day for 10 days. We demonstrate that these biomarkers can differentiate the severity of effects induced by melamine or cyanuric acid. All melamine-treated animals experienced adverse effects; however, pregnant rats were most sensitive as indicated by increased SCr, BUN, and kidney weights, decreased body weight, and presence of renal crystals. These effects coincided with elevated urinary biomarker levels as early as day 2 of exposure. One cyanuric acid-treated rat displayed effects similar to melamine, including increased urinary biomarker levels. This work illustrates that these biomarkers can detect early effects of melamine or cyanuric acid crystal-induced nephropathy and further supports the use of urinary protein immunoassays as a powerful, non-invasive method to assess nephrotoxicity.

Acute toxicity of sodium arsenite in a complex food matrix

Acute toxicity of a single oral dose of sodium arsenite (As), administered in half and half cream (HH), was assessed in male and non-pregnant female rats (0.41, 4.1, 41.0 and 410.0mg/kg body weight) and pregnant rats (0.41, 4.1 and 41.0mg/kg body weight). Control rats received deionized water alone, HH alone or 41.0mg/kg As in deionized water (41 mg/kg As-water). Male and non-pregnant rats were monitored for 14 consecutive days post-dosing. Pregnant rats, dosed on gestation day 10 (GD-10), were monitored until fetuses were collected on GD 20. High mortality (100%) was observed in male and non-pregnant female rats exposed to 410.0mg/kg As-HH. Low mortality (25%) was observed in non-pregnant female rats exposed to 41 mg/kg As-water. No mortality was observed in other control or treated groups. Reduced female fetal numbers were observed in the 41 mg/kg As-water group but not in the other control groups. Developmental effects were not observed in the controls or the As-HH treatment groups. In conclusion, As toxicity was not reduced when a high dose (410 mg/kg) was administered in HH however, at lower doses (41 mg/kg), HH reduced acute As oral toxicity in the female and developing fetus.

Effects of oral androstenedione on phospholipid fatty acids, ATP, caspase-3, prostaglandin E(2) and C-reactive protein in serum and livers of pregnant and non-pregnant female rats

Androstenedione, a steroidal dietary supplement taken to enhance athletic performance, could affect serum and liver lipid metabolism, induce liver toxicity or alter inflammatory response depending on dose and duration of exposure. Pregnancy could further exaggerate these effects. To examine this, mature female rats were gavaged with 0, 5, 30 or 60 mg/kg/day androstenedione beginning two weeks prior to mating and continuing through gestation day 19. Non-pregnant female rats were gavaged over the same time frame with 0 or 60 mg/kg/day androstenedione. Serum was collected and livers were removed from dams on gestation day 20 and from non-pregnant rats after 5 weeks of treatment. Androstenedione had no effect on serum total cholesterol, triglycerides or HDL-cholesterol, but significantly decreased C-reactive protein in pregnant rats and prostaglandin E(2) in serum of both pregnant and non-pregnant rats. There were treatment related decreases in liver ATP and, to a lesser degree, caspase-3 and no change in alkaline phosphatase of pregnant female rats. Androstenedione decreased docosahexaenoic acid in both serum and liver phospholipids of pregnant female rats. In conclusion, oral androstenedione did not result in overt hepatotoxicity in pregnant female rats, but produced modest changes in lipid metabolism and may impair regeneration of injured hepatic cells or tissue.

Effects of oral androstenedione on steroid metabolism in liver of pregnant and non-pregnant female rats

It is unknown whether androstenedione, a steroidal dietary supplement taken to enhance athletic performance, can affect physiological hormone levels by altering liver enzyme activities that metabolize steroid hormones. Altered hormone levels could be especially devastating during pregnancy. Mature female rats were gavaged with 0, 5, 30 or 60 mg/kg/day androstenedione beginning two weeks prior to mating and continuing through gestation day 19. Non-pregnant female rats were gavaged over the same time frame with 0 or 60 mg/kg/day androstenedione. Livers were removed from dams on gestation day 20 and from non-pregnant rats after five weeks' treatment. Liver microsomes were incubated with 200 microM testosterone, and the reaction products were isolated and analyzed by HPLC. In pregnant rats, formation of 6alpha-, 15beta-, 7alpha-, 16beta-, and 2beta-hydroxytestosterone was increased significantly vs. control at the highest dose level only. Formation of 6beta-hydroxytestosterone increased significantly at both the 30 and 60 mg/kg/day dose levels. In non-pregnant rats, 60 mg/kg/day androstenedione significantly increased formation of 15beta-, 6beta-, 16beta-, and 2beta-hydroxytestosterone. The data suggest that high oral doses of androstenedione can induce some female rat liver cytochromes P450 that metabolize steroid hormones and that the response to androstenedione does not differ between pregnant and non-pregnant female rats.

Developmental effects of serum from flaxseed-fed rats on cultured rat embryos

Gestation day 9.5 rat embryos were cultured for 45 h in serum obtained from pregnant rats that had been fed throughout gestation with either a control diet (based on the AIN-93 formulation), a diet supplemented with flaxseed (20% or 40%, w/w), or a diet supplemented with de-fatted flaxseed ("flaxseed meal", 13 or 26%, w/w). The embryos were fixed in neutral formalin at the end of culture. Overall growth and development was assessed, and the presence of abnormalities was noted. A significant inhibition of growth (as determined by crown-rump length) relative to control was observed in embryos cultured in serum from rats fed the 20% flaxseed diet. The incidence of spontaneous heart inversions was increased significantly in the embryos cultured in serum from the 20% flaxseed and 26% flaxseed meal fed rats. The incidence of flexion defects was increased significantly in embryos cultured in serum from 20% flaxseed-fed rats. The lack of an apparent dose response in any of the statistically significant effects suggests that the observed anomalies were chance occurrences unrelated to the treatment group from which serum was obtained. It is therefore concluded that diets high in flaxseed or flaxseed meal do not result in serum factors that are directly embryotoxic to organogenesis-staged rat embryos. This finding is consistent with the findings of a parallel in vivo rat teratology study where no significant embryotoxicity attributable to flaxseed exposure was observed.

Developmental toxicity of sodium fluoride measured during multiple generations

Sodium fluoride (NaF) has been used to fluoridate drinking water in the United States since the mid 1940s. Because of the lack of reliable studies on the multigeneration effects of the compound, NaF (0, 25, 100, 175 or 250 ppm in drinking water) was given to rats continuously during three generations. Parental (F0) generation rats were treated for 10 weeks and mated within groups. At gestation day 20, caesarean sections were performed and eight F0 females per group and their litters (F1) were observed for implant status, fetal weight and length, sex and morphological development. The remaining F0 females (29-32 per group) were allowed to litter. F1 offspring (36 of each sex per group) were mated within groups, and caesarean sections were performed at gestation day 20. The F1 females and their litters (F2) were observed for implant status, fetal weight and length, sex and morphological development. In addition, F2 fetuses were evaluated for internal (soft-tissue) and skeletal development. Decreased fluid consumption for F0 and F1 dams at 175 and 250 ppm was attributed to decreased palatability of the solution. No dose-related effects in feed consumption or mean body weight gain were observed in either F0 or F1 females. Numbers of corpora lutea, implants, viable fetuses and fetal morphological development were similar in all groups. No dose-related anomalies in internal organs were observed in F2 fetuses. Ossification of the hyoid bone of F2 fetuses was significantly decreased at 250 ppm. Because of the decreased ossification of the hyoid bone, 250 ppm is considered the effect level.

Multigenerational evaluation of sodium fluoride in rats

Since the mid 1940s, fluoride has been added to tap water in American communities in an effort to reduce the incidence of dental caries in the population. When the levels of fluoride in drinking water were tested and set, water was the only measurable source of fluoride for most communities. Now, adults and children ingest fluoride with foods and beverages prepared with fluoridated water, and they are exposed to fluoride-containing dental products. As a result, exposure to fluoride is greater than had been anticipated. In the early 1990s, the existing reproductive studies were reviewed in several reports and were considered to be inadequate to determine potential reproductive or developmental hazards. The effects of sodium fluoride ingestion at 0, 25, 100, 175 or 250 ppm in drinking water measured in rats throughout three generations are reported here. Feed and fluid consumption, body weights and clinical signs were recorded at regular intervals. Decreased fluid consumption observed at 175 and 250 ppm was attributed to decreased palatability and did not affect reproduction. No cumulative effects were observed in the three generations. Mating, fertility and survival indices were not affected. Organ-to-body-weight ratios and organ-to-brain weight ratios were not affected. Sodium fluoride up to 250 ppm did not affect reproduction in rats.

Testing the potential of flaxseed to affect spermatogenesis: morphometry

Quantitative information was collected on male reproductive effects of maternal and postnatal dietary exposure to flaxseed (20 or 40%), flaxmeal (13 or 26%) or standard NIH AIN-93 feed (0% flaxseed control). Measurements were made on the testes of F1 generation males rats (1) whose mothers were exposed to the diets designated above, and (2) who, after weaning, were placed on the same diet as their mothers for an additional 70 days. The seminiferous tubules comprised 86%, 84%, 84%, 84% and 85% of the total testis volume while the interstitial space comprised 12%, 14%, 14%, 14%, 13% of the total testis volume for the 0% flaxseed/flaxmeal, 20% flaxseed, 13% flaxmeal, 40% flaxseed and 26% flaxmeal groups, respectively. Statistically significant decreases in the absolute volume of the seminiferous tubules were observed in the 20% and 40% flaxseed-treated groups when these groups were compared to controls. Borderline statistically significant differences were also observed when Sertoli cell nucleolar number per tubular cross-section were compared in the 13% flaxmeal and 20% flaxseed treatment groups. These effects were not considered biologically significant because other parameters of male reproductive function appeared normal. Overall, the quantitative information obtained suggests that exposure to flaxseed/flaxmeal at the doses used in the present study does not adversely affect testis structure or spermatogenesis in the rat.

The effect of maternal exposure to flaxseed on spermatogenesis in F(1) generation rats

Pregnant Sprague-Dawley rats were exposed to a flaxseed (20 or 40%), flaxmeal (13 or 26%) or standard NIH AIN-93 (0% flaxseed control) diet throughout gestation and until their offspring were weaned. After weaning, F(1) generation males were placed in the same diet treatment groups as their mothers for 70 days. Statistically significant differences were not observed between either low-dose or high-dose flaxseed and flaxmeal-treated animals and the 0% flaxseed control animals for testis weights, homogenization resistant spermatid counts, daily sperm production rates, epididymal weights, seminal vesicle weights, seminiferous tubule fluid testosterone concentrations and the percentage of sperm abnormalities. The following statistically significant differences were observed when treated groups and the 0% flaxseed control groups were compared: (1) increases in serum LH in the 20% and 40% flaxseed treatment groups and in serum LH and testosterone in the 26% flaxmeal treatment group; (2) increases in the cauda epididymal weight from the 20% and 40% flaxseed groups; (3) increases in cauda epididymal sperm numbers/g epididymis from the 20% and 40% flaxseed and the 13% and 26% flaxmeal treatment groups; (4) a decrease in prostatic weight from the 20% flaxseed and 13% and 26% flaxmeal treatment groups. Prostate weight in the 40% flaxseed treatment group was lower but not statistically significantly different than the 0% flaxseed control group. Histological effects on spermatogenesis were not observed in either the control group, flaxmeal or the flaxseed treated groups.

The effect of vomitoxin (Deoxnivalenol) on testicular morphology, testicular spermatid counts and epididymal sperm counts in IL-6KO [B6129-IL6 [TmlKopf] (IL-6 gene deficient)] and WT [B6129F2 (wild type to B6129-IL6 with an intact IL-6 gene)] mice

The potential of vomitoxin (VT) to affect testicular morphology and testicular and epididymal sperm counts was assessed in three strains of mice: IL-6KO [B6129-IL6 (tmlKopf) (IL-6 gene deficient)], WT [B6129F2 (wild type to B6129-IL6 with an intact IL-6 gene)] and B6C3F1 mice in a 90-day feeding study. The treated mice received VT at a concentration of 10 ppm in their diet. The body weight of VT-treated animals was significantly reduced compared with control animals. Slight changes, not statistically significant, were observed in relative testis weight and testicular spermatid counts. Histological changes were not apparent in the testes of VT-treated animals. The diameter of the seminiferous tubules, the height of the seminiferous epithelium and the number of Sertoli cell nucleoli per cross-sectioned seminiferous tubule in the VT-treated groups were not significantly different from their respective untreated controls. The IL-6KO and B6C3F1 VT-treated mice had significantly reduced cauda epididymal weights compared with their respective controls. These changes were not attributed to decreased sperm counts and this finding suggests that VT may exert an adverse affect on the epididymis.

Food and Drug Administration proposed testing guidelines for developmental toxicity studies. Revision Committee. FDA Guidelines for Developmental Toxicity and Reproduction, Food and Drug Administration

The Food and Drug Administration (FDA) is the agency responsible for ensuring that the direct food additives and color additives used in food in the United States are safe for all consumers. In 1982, in an effort to provide guidance concerning appropriate tests, the FDA issued Toxicological Principles for the Safety Assessment of Direct Food Additives and Color Additives Used in Food, commonly known as the Redbook. The Redbook included detailed guidelines for testing the effects of direct and indirect food and color additives on mothers and their developing fetuses. Based on refinements in safety assessment and risk evaluation as well as expansion of knowledge concerning the metabolism and pharmacokinetics of food and color additives, the need to revise and update the 1982 document became apparent. In 1993, Redbook II in draft form was made available for public comment. Since then, test end points and developmental landmarks have been refined. The latest proposed guidelines for developmental toxicity studies are provided here.

Food and Drug Administration proposed testing guidelines for reproduction studies. Revision Committee. FDA Guidelines for Developmental Toxicity and Reproduction, Food and Drug Administration

In the United States, the Food and Drug Administration (FDA) is the agency responsible for ensuring that the direct food additives and color additives used in food are safe for all consumers. In order to determine the safety of these additives for consumption, appropriate information and results from a series of tests must be made available to the agency. In 1982, in an effort to provide guidance to the food industry concerning the appropriate tests for the determination of safety, the FDA issued the Toxicological Principles for the Safety Assessment of Direct Food Additives and Color Additives Used in Foods, commonly referred to as the Redbook. In 1993, based on the expansion of technology and the use of food additives, as well as the refinement of the scientific criteria for establishing safety, the FDA updated its guidelines and issued the draft Redbook II. Since Redbook II was issued, additional refinements have been made in the procedures for the multigeneration reproduction study and for the assessment of effects on male reproduction. The latest proposed guidelines for multigeneration studies are provided here.

Light microscopic observations on the reproductive tract of the male sand rat, Psammomys obesus

The anatomy of the reproductive tract of the male sand rat, Psammomys obesus, was examined by light microscopy. Histologically, the reproductive tract is similar to other rodent species. Seminiferous tubules in the 1-month-old sand rat do not contain a tubular lumen but Sertoli cells, spermatogonia and spermatocytes are present. A full complement of germ cells is present in the seminiferous tubules by 2.5 months and spermatogenesis is well established. The interstitial space is not well defined until 2.5 months when cell types typical of most rodent species are observed. The epididymis is not noticeably segmented into lobules. An epididymal lumen is not observed until 2.5 months. Cauda epididymal sperm are not observed in the 1 or 2.5-month-old animals and cauda epididymal sperm counts from the 7.5 and 12.5-month-old animals are highly variable. The epididymis, proximal and middle regions of the vas deferens, seminal vesicles and prostate display morphological and histological characteristics similar to other rodent species. The distal end of the vas deferens is not expanded to form an ampulla.

Testing the potential of sodium fluoride to affect spermatogenesis: a morphometric study

This study provides quantitative information on the effect of sodium fluoride (NaF) on the testes of F1 generation male rats exposed in utero and during lactation to NaF at one of four concentrations (25, 100, 175, 250 ppm). At weaning, the F1 generation males were exposed to NaF in their drinking water for 14 weeks, after which time testicular tissues were perfusion-fixed with glutaraldehyde and observed after being embedded in plastic. The seminiferous tubules comprised 89%, 87%, 88%, 88% and 88% of the total testis volume while the interstitial space occupied 9.3%, 11.2%, 10.2%, 9.8% and 9.9% of the total testis volume for the 0, 25, 100, 175 and 250 ppm NaF treatment groups, respectively. Statistically significant differences between control and NaF-treated rats were not observed with respect to absolute volume of the seminiferous tubules, interstitial space, Leydig cells, blood vessels boundary layer, lymphatic space, macrophages, tubular lumen or absolute tubular length and absolute tubular surface area, mean Sertoli cell nucleoli number per tubular cross-section, mean seminiferous tubule diameter and the mean height of the seminiferous epithelium. A statistically significant decrease in the absolute volume and volume percent of the lymphatic endothelium was observed in the 175 and 250 ppm NaF-treated groups and in the testicular capsule in the 100 ppm NaF-treated groups. The significance of this finding is unknown at the present time. Overall, the quantitative information obtained suggests that exposure to NaF at the doses used in the present study does not adversely affect testis structure or spermatogenesis in the rat.

Effects of fumonisin B1 in pregnant rats. Part 2

The developmental toxicity of purified fumonisin B1 (FB1), a mycotoxin from the common corn fungus Fusarium moniliforme, was examined in Charles River rats. Pregnant rats were dosed orally on gestation days 3-16 at 0, 6.25, 12.5, 25 or 50 mg FB1/kg body weight/day. FB1 was not teratogenic at the doses tested. At 50 mg/kg, maternal toxicity (inappetence, emaciation, lethargy, death, resorption of entire litters) and foetal toxicity (increased number of late deaths, decreased foetal body weight, decreased crown rump length, increased incidence of hydrocephalus, increased incidence of skeletal anomalies) were seen. The foetal toxicity observed at 50 mg/kg may be related to maternal toxicity. Histopathological evaluation of tissues from dams of control and all treated groups revealed dose-related toxic changes in kidney and liver tissues. Acute toxic tubular nephrosis was seen in kidneys from all treated groups. Hepatocellular cytoplasmic alteration and individual cellular necrosis of the liver was seen in the two high-dose groups. Sphinganine (Sa) and sphingosine (So) were measured in day-17 adult and foetal tissues. Dose related increases in Sa/So ratios were seen in maternal liver, kidney, serum and brain, but there was no effect on foetal liver, kidney and brain. These data suggest that FB1 does not cross the placenta and further suggest that the observed foetal toxicity is a secondary response to maternal toxicity.

Effects of fumonisin B1 in pregnant rats

Fumonisin B1 (FB1), the major mycotoxin from Fusarium moniliforme, has been implicated as a causative agent in several animal and human diseases. Despite animal toxicity studies and human epidemiological studies of FB1, knowledge of its reproductive effects is scarce. In this study, one of a series of proposed studies that will allow extrapolation to humans, pregnant rats were given oral doses of 0, 1.875, 3.75, 7.5 or 15 mg FB1/kg on gestation days 3 16. Caesarean sections were performed on day 17 or 20, and maternal condition, implantation efficiency, foetal viability and foetal development were measured. Dose-related decreases in overall feed consumption and body weight gain were seen, but only the feed consumption decrease at 15 mg/kg, and the decreased body weight gain at 15 mg/kg on days 0-17 were statistically significant. Foetal body weights at day 17 were similar in control and treated groups; but in day-20 foetuses, female weight and crown-rump length were significantly decreased at 15 mg/kg. FB1 was not teratogenic at the doses tested, and no dose-related effects were seen in either skeletal or soft-tissue development. In day-17 animals, maternal and foetal brain, liver and kidney tissues, and maternal serum were preserved to study the levels of sphinganine (Sa), sphingosine (So), and the Sa/So ratios. Dose-related increases were seen in Sa/So ratios in maternal livers, kidneys and serum. Sa/So ratios of maternal brains were not affected, nor were those of foetal kidneys, livers or brains.

Testing the potential of sodium fluoride to affect spermatogenesis in the rat

The potential of sodium fluoride (NaF) to affect spermatogenesis and endocrine function was assessed in P and F1 generation male rats. Male and female experimental rats received sodium fluoride in their drinking water at one of four concentrations (25, 100, 175, 250 ppm). P generation male and female rats were exposed to sodium fluoride in their drinking water for 10 wk and then males were mated to females within the same treatment groups. Reproductive tissues were collected from P generation male rats after approximately 14 wk of treatment. Pregnant females (P) were exposed to sodium fluoride via their drinking water through gestation and lactation. F1 generation weanling male rats remained within the same treatment groups as their parents. F1 generation male rats were exposed to sodium fluoride in their drinking water for 14 wk, at which time reproductive tissues were collected. Dose-related effects were not observed within the P and F1 treatment groups in testis weights, prostate/seminal vesicle weights, non-reproductive organ weights, testicular spermatid counts, sperm production per gram of testis per day, sperm production per gram of testis, LH, FSH or serum testosterone concentrations. Histological changes were not observed in testicular tissues from either the P or F1 generation. We conclude that prolonged exposure to sodium fluoride in drinking water at the doses administered in this study does not adversely affect spermatogenesis or endocrine function in the P and F1 generation male rats.

Is Leydig cell steroidogenic function affected by the germ cell content of the seminiferous tubules?

The effect of testicular germ cell content on Leydig cell steroidogenic function in vivo in adult rats was examined. Three experimental paradigms were used to effect germ cell changes. First, a vitamin A-depletion/repletion regimen was used to achieve synchrony at different stages of the cycle of the seminiferous epithelium and thus produce testes with widely differing germ cell contents. Second, long term vitamin A depletion was used to effect germ cell, but not Leydig cell, loss. Third, Leydig cells and germ cells first were eliminated from the testes of adult rats by the administration of ethane 1,2-dimethane sulfonate (EDS) along with testosterone- and estradiol-filled Silastic capsules; Leydig cells were then restored to the germ cell-depleted testes by removal of the luteiniging hormone (LH)-suppressing capsules. Serum, interstitial fluid, and seminiferous tubule fluid testosterone concentrations did not differ between rats in which at least 70% of the seminiferous tubules contained germ cells at stages VII-VIII or at stages XII-III of the cycle. The capacity of the testes of these rats to produce testosterone, assessed by their in vitro perfusion with maximally stimulating LH, also showed no differences despite the differences in germ cell content. Elimination of germ cells throughout the testes by long term vitamin A depletion also did not affect the steroidogenic function of the testes. Finally, the steroidogenic function of Leydig cells restored to germ cell-depleted testes was indistinguishable from that of germ cell-containing controls. These results, taken together, provide evidence supporting the contention that the germ cell content of the testis has little or no effect on testicular steroidogenic function.

Effect of intratesticular injection of sodium fluoride on spermatogenesis

The potential of sodium fluoride to affect spermatogenesis in the rat was assessed by intratesticular injection. Experimental rats' left testis was injected with sodium fluoride (50, 175 and 250 ppm) in vehicle (0.9% physiological saline); control testes were injected with vehicle. The right testis served as a non-injected control. Testicular tissues collected 'at' and 'distal to' the injection site and from the non-injected control testes were evaluated microscopically 24 hr and 1, 2 and 3 wk post-injection. Testicular tissues obtained at and distal to the injection site in all fluoride-injected groups resembled tissues collected from corresponding areas in the controls. Seminiferous tubule damage observed in both the vehicle-injected control testes and the fluoride-injected testes but not in the non-injected testes was attributed to injection trauma. Polymorphonuclear leucocyte infiltration was observed 24 hr post injection only at the injection site in the vehicle- and fluoride-injected groups. Leydig cells were unaffected. Leucocyte infiltration with seminiferous tubule damage was not considered to be a fluoride treatment-related effect because it was observed in both vehicle- and fluoride-injected testes. The results demonstrate that the rat is not adversely affected by direct exposure to fluoride at levels 200 times greater than those under normal conditions.

Developmental toxicity of orange B when given to rats by gavage

The pyrazolone dye Orange B was given by gavage to pregnant Osborne-Mendel rats throughout gestation. Dose levels of 0, 15, 30, 100, 200, 400, or 700 mg/kg body weight were given daily. On gestation day 20, the females were killed and cesarean sections were performed. Feed consumption and maternal weight gain were not affected. No dose-related changes were seen in maternal clinical findings, implantations, fetal viability, or fetal size (weight and length). No compound-related effects were seen in sternebral development. No dose-related effect was seen in the incidence of skeletal variations in fetuses or in the number of litters containing fetuses with skeletal variations. Skeletal development, as measured by the average number of ossified vertebrae, was similar in all groups. No compound-related effects were seen in soft-tissue development.

Developmental toxicity of sodium fluoride in rats

Despite the chronic exposure of the US population to fluoridated drinking water since the 1940s, existing studies have been judged inadequate to determine any potential reproductive or developmental hazard. This study was conducted to determine the effects of sodium fluoride (NaF) on foetal development. Sperm-positive female rats were given 0, 10, 25, 100, 175 or 250 ppm NaF daily throughout gestation. They were dosed by drinking water to mimic human exposure to fluoridated water. No dose-related behavioural changes or maternal clinical signs were noted. Fluid consumption by females in the 175- and 250-ppm groups was significantly less than that of the control females. Because of this decreased fluid consumption, the daily amount of NaF ingested (0, 1.4, 3.9, 15.6, 24.7 and 25.1 mg/kg body weight) was less than expected at the two high levels. Feed consumption decreased significantly at 250 ppm, and body weights of pregnant females reflected feed consumption trends. The mean number of viable foetuses per female in all treated groups was similar to that of the control group. The significant decrease in the mean number of implants per litter in the 250-ppm group is probably linked to the lower mean number of corpora lutea in this group. The occurrence of in utero deaths was similar in the control and treated groups. Foetal growth (in terms of foetal body weight and crown-rump length) was not affected by NaF, despite the fact that the dams in the 250-ppm group ate significantly less feed and drank significantly less fluid. There was no dose-related increase in the number of external anomalies in foetuses due to NaF ingestion. At the doses given, NaF had no effect on the development of specific bones, including sternebrae. A significant increase was seen in the average number of foetuses with three or more skeletal variations in the 250-ppm group; the number of litters with foetuses with three or more skeletal variations was increased in the 250-ppm group also, but the increase was not significant. There was no dose-related effect of NaF on the incidence of soft tissue variations.

Regional cellular heterogeneity and DNA synthetic activity in rat ventral prostate during postnatal development

Previous studies have provided evidence that the rat ventral prostate grows primarily, if not exclusively, at its distal tips. However, as yet there have been no analyses in which individual cells in defined regions of the prostatic ductal system have been resolved and quantified. Moreover, the possibility that the prostate might grow differently at different times of postnatal development has received little attention. Our objectives were to identify and quantify the proliferating epithelial and stromal cells in defined regions of the rat ventral prostate during its postnatal development. To this end, 3H-thymidine was administered in vivo to rats of ages 10-60 days. A dissection technique was then used by which the distal, intermediate, and proximal segments of the prostatic ductal system were physically isolated from each other without removing the stromal tissue. Longitudinal sections of these segments were examined for cellular composition and DNA synthetic activity. Regional heterogeneity with respect to cell composition and cell proliferation was seen. In rats of all ages, DNA synthetic activity was seen in epithelial and stromal cells throughout the prostate, rather than only in the distal segment. At Days 10 and 20, significantly higher percentages of epithelial and stromal cells were labeled in the distal than in the proximal segments; but at Days 45 and 60, the percentages of labeled epithelial and stromal cells in the distal, intermediate, and proximal segments were similar. Thus, in all segments, and at all ages, substantial labeling was seen throughout the prostate. These data suggest that the prostate grows in both length and width throughout postnatal development, reminiscent of the growth of a tree.

Reversal of long-term LH deprivation on testosterone secretion and Leydig cell volume, number and proliferation in adult rats

The purpose of this study was to determine whether Leydig cell volume and function could recover fully from long-term LH deprivation upon restoration of endogenous LH secretion, and whether the restoration of LH would elicit a mitogenic response, i.e. stimulate Leydig cell proliferation or affect Leydig cell number per testis. LH secretion was inhibited by treating adult rats with testosterone and oestradiol-filled (TO) silicone elastomer implants (16 weeks), and was restored by removing the implants. Changes in serum concentrations of LH and FSH, LH-stimulated testosterone secretion by testes perfused in vitro, Leydig cell volume and number per testis, average Leydig cell volume and Leydig cell [3H]thymidine incorporation were measured at weekly intervals following implant removal. The TO implants inhibited (P less than 0.01) LH secretion, but serum concentrations of FSH were not significantly different (P greater than 0.10) from control values. After implant removal, serum LH returned to control values within 1 week, whereas serum FSH increased twofold (P less than 0.01) and returned to control values at 4 weeks. LH-stimulated in-vitro testosterone secretion was inhibited by more than 99% in TO-implanted rats, but increased (P less than 0.01) to 80% of control values by 8 weeks after implant removal. The total volume of Leydig cells per testis and the volume of an average Leydig cell were 14 and 19% of control values respectively, after 16 weeks of TO implantation (P less than 0.01), but returned to 83 and 86% of controls (P greater than 0.10) respectively, by 6 weeks after implant removal. Leydig cell proliferation ([3H]thymidine labelling index) was low (less than 0.1%) in both control and TO-implanted rats, increased (P less than 0.01) fivefold from 1 to 4 weeks after implant removal and then declined to control values at 6 weeks. The increase in Leydig cell [3H]thymidine incorporation was mimicked by treating TO-implanted rats with exogenous LH, but not FSH. Leydig cells were identified in both the interstitium and the lamina propria of the seminiferous epithelium. The proportion of Leydig cell nuclei in the lamina propria was 30-fold greater (P less than 0.01) at 1 and 3 weeks after implant removal (3%) compared with that for control and TO-implanted rats (0.1%). Total Leydig cell number per testis was marginally but not significantly (P = 0.06) decreased in rats treated with TO implants for 16 weeks when compared with controls (18.4 +/- 2.2 vs 25.4 +/- 1.2 x 10(6)).(ABSTRACT TRUNCATED AT 400 WORDS)

Does ethane 1,2-dimethanesulphonate (EDS) have a direct cytotoxic effect on the seminiferous epithelium of the rat testis?

The authors examined the possibility that ethane 1,2-dimethanesulphonate (EDS) has a cytotoxic effect on spermatogenesis that is not secondary to androgen withdrawal resulting from the well known cytotoxic effect of EDS on Leydig cells. Adult male rats were implanted with polydimethylsiloxane (PDS) capsules containing testosterone (T) and estradiol (E), and were simultaneously injected with EDS. The PDS-TE implants, by inhibiting luteinizing hormone (LH) production, prevented Leydig cells from repopulating the testis and clamped testosterone within the seminiferous tubules at increasing concentrations relative to implant size. In rats that received EDS alone, the number of advanced spermatids per testis was significantly reduced by 2 weeks, but within 8 weeks returned to the numbers maintained in vehicle-injected control rats or in vehicle-injected rats that received testosterone- and estradiol-filled capsules of 24 cm and 0.1 cm, respectively (PDS-24TE). Surprisingly, in rats that received an EDS injection plus PDS-24TE implants, the number of advanced spermatids per testis was significantly reduced at 8 weeks and severe seminiferous tubule atrophy occurred despite the fact that the testosterone concentration was sufficient to quantitatively maintain spermatogenesis in vehicle-injected rats. In rats injected with EDS and implanted with 24 cm testosterone but not estradiol-filled capsules (PDS-24T), the advanced spermatid number per testis was significantly higher than that in the EDS plus PDS-24TE rats, but significantly lower than that in control rats. These results suggest that EDS may have a cytotoxic effect on the seminiferous epithelium that is independent of the elimination of Leydig cells, and the EDS and estradiol act synergistically to exert a profound toxic effect on spermatogenesis.

Restoration of spermatogenesis by exogenously administered testosterone in rats made azoospermic by hypophysectomy or withdrawal of luteinizing hormone alone

The major objective of the studies presented herein was to compare the extent to which exogenously administered testosterone is able to restore spermatogenesis in adult rats made azoospermic by withdrawal of all pituitary hormones (hypophysectomy for 4 weeks) vs. withdrawal of LH alone [testosterone- and estradiol-filled (TE) polydimethylsiloxane implants of 2.5 and 0.1 cm, respectively, for 8 weeks]. In hypophysectornized (Hypox) rats, serum LH and FSH were both undetectable; in the rats that received TE implants, serum LH was undetectable, but FSH was unaffected compared to control values. Seminiferous tubule fluid testosterone concentrations were reduced significantly from their control values of 60-65 to 1.4-1.7 ng/ml in the azoospermic Hypox and TE rats. These rats then received testosterone-filled implants of 4, 12, 18, or 24 cm and were killed 2 months later. In both the Hypox and TE rats, seminiferous tubule fluid testosterone concentrations rose linearly with increasing capsule sizes, and with each of the implant sizes, these concentrations did not differ significantly between the Hypox and TE rats. This made it possible for the first time to examine the effects of comparable intratesticular testosterone concentrations on the numbers of advanced spermatids per testis that could be restored in the azoospermic testes of rats lacking all pituitary factors vs. those lacking only LH. The results that we present demonstrate that the numbers of restored advanced spermatids were consistently and significantly lower in Hypox than in TE rats despite equivalent seminiferous tubule fluid testosterone concentrations. These results provide quantitative conclusive evidence to support the contention that pituitary factors in addition to LH are required for the quantitative restoration of spermatogenesis in the adult rat testis.

Retinal cysts in the eye of the Asian musk shrew, Suncus murinus, (Mammalia, Insectivora)

The development of retinal cysts in the eye primordia of Suncus murinus embryos was studied. Retinal infoldings were first identified in the 17.5-day-old embryo (crown rump length--CRL = 6.3 mm). At this time, the apex of the developing retinal fold could be identified attached to the lens. The pigmented epithelium did not take part in the formation of the cyst. The retinal fold closed, to form a cyst, by day 23 of embryonic development (CRL = 14.0 mm). The newly formed retinal cyst remained continuous with the retina and extended toward the lens where it attached to the lens epithelium. Retinal cysts had an oval, bilaterally symmetrical shape and a narrow lumen, which, lined by the internal limiting membrane, occasionally contained cellular debris. The dimensions of the cysts were usually 100 to 150 microns (diameter) by 200 to 250 microns (length). Retinal cysts appeared in 45 per cent of the embryos examined.

To what extent can spermatogenesis be maintained in the hypophysectomized adult rat testis with exogenously administered testosterone?

In a previous study it was demonstrated that spermatogenesis can be maintained quantitatively with exogenously administered testosterone in adult intact rats that lack LH. The studies described herein were designed to examine the extent to which spermatogenesis can be maintained quantitatively with exogenously administered testosterone in adult rats that lack all pituitary hormones. Adult male rats were hypophysectomized and testosterone was administered at the time of hypophysectomy via sustained release polydimethylsiloxane (PDS) capsules of increasing lengths. We used the PDS capsules to clamp testosterone at defined concentrations within the seminiferous tubule fluid over a 2- to 3-month treatment period. Mean testis weights and advanced spermatid numbers per testis stabilized by 8 weeks of testosterone treatment regardless of testosterone dose. Both testis weight and advanced spermatid number responded to testosterone dose, reaching plateaus of 1.2 g and 170 x 10(6) per testis, respectively. These values were 60% of, and significantly less than, the respective control values. This result was in striking contrast to the results of our previous study of LH-suppressed intact rats, in which exogenously administered testosterone resulted in testis weights and advanced spermatid numbers that plateaued at values not significantly different from those in controls. These different effects of testosterone in intact and hypophysectomized rats occurred despite the fact that the seminiferous tubule fluid testosterone concentrations achieved in the hypophysectomized rats (up to 25 ng/ml) were greater than the minimal testosterone concentration found previously to be required to maintain spermatogenesis quantitatively in LH-suppressed intact rats (13 ng/ml). Taken together, these results demonstrate clearly that intratesticular testosterone doses that are as high as or higher than those that maintain spermatogenesis quantitatively in intact rats lacking LH fail to maintain spermatogenesis quantitatively in rats lacking all pituitary hormones.

Restoration of advanced spermatogenic cells in the experimentally regressed rat testis: quantitative relationship to testosterone concentration within the testis

We examined the effect of exogenously administered testosterone (T) on the quantitative restoration of advanced spermatogenic cells in adult rat testes rendered azoospermic by treating rats with polydimethylsiloxane (PDS) implants of T and estradiol (E). Experimental rats received PDS-TE implants for an initial 8-week period; control rats received empty implants. By 8 weeks of PDS-TE treatment, rats became severely oligospermic, and the T concentration within the seminiferous tubule fluid (STF) was reduced approximately 80% (from 57.8 ng/ml in controls to 9.6 ng/ml). After the initial 8-week PDS-TE treatment, PDS-TE implants were removed from one group of rats; a second group of PDS-TE-implanted rats received an additional PDS-T implant of 24 cm. Eight weeks after the removal of PDS-TE implants or the implantation of additional T, testis weight and numbers of advanced spermatogenic cells were restored to those of control rats. The STF T concentration 8 weeks after the removal of PDS-TE implants also was restored to that in control rats. In contrast, the STF T concentration increased to only 40% of control values in the rats that received an additional T implant. Despite this 60% reduction in T concentration compared to the control value, advanced spermatogenic cell number was restored to a value indistinguishable from that of intact controls. These observations indicate that spermatogenesis can be quantitatively restored in PDS-TE-implanted rats with exogenously administered T, and moreover, that this restoration does not require the high T concentration found in the STF of intact control rats.

Spermiogenesis in the bullfrog (Rana catesbeiana): a study of cytoplasmic events including cell volume changes and cytoplasmic elimination

The process by which spermatid cytoplasmic volume is reduced and cytoplasm eliminated during spermiogenesis was investigated in the bullfrog Rana catesbeiana. At early phases of spermiogenesis, newly formed, rounded spermatids were found within spermatocysts. As acrosomal development, nuclear elongation, and chromatin condensation occurred, spermatid nuclei became eccentric within the cell. A cytoplasmic lobe formed from the caudal spermatid head and flagellum and extended toward the seminiferous tubule lumen. The cytoplasmic lobe underwent progressive condensation whereby most of its cytoplasm became extremely electron dense and contrasted sharply with numerous electron-translucent vesicles contained therein. At the completion of spermiogenesis, many spermatids with their highly condensed cytoplasm still attached were released from their Sertoli cell into the lumen of the seminiferous tubule. There was no evidence of the phagocytosis of residual bodies by Sertoli cells. Because spermatozoa are normally retained in the testis in winter and are not released until the following breeding season, sperm were induced to traverse the duct system with a single injection of hCG. Some spermatids remained attached to their cytoplasm during the sojourn through the testicular and kidney ducts; however, by the time the sperm reached the Wolffian duct, separation had occurred. The discarded cytoplasmic lobe (residual body) appeared to be degraded with the epithelium of the Wolffian duct. It was determined that the volume of the spermatid was reduced by 87% during spermiogenesis through a nuclear volume decrease of 76% and cytoplasmic volume decrease of 95.3%.

Spermiogenesis in the bluegill (Lepomis macrochirus): a study of cytoplasmic events including cell volume changes and cytoplasmic elimination

The process involved in the reduction of both nuclear and cytoplasmic volume was investigated in the bluegill (Lepomis macrochirus), a teleost fish. Young spermatids contained centrally positioned nuclei which, with time, moved toward the cell surface to become eccentrically positioned. Chromatin condensation was initiated from a region near the implantation fossa, whereas at the opposite pole of the nucleus an area sparse in heterochromatin (clear area) was noted. The nuclear membrane lying adjacent to the clear area dissolved and subsequently reformed, yielding a nucleus with a reduced volume. During this process, packets of cytoplasm surrounded by a double membrane were formed along the future midpiece. The packets of cytoplasm migrated toward the cell surface, protruded from the surface, and were extruded into the spermatocyst lumen. These structures, termed residual bodies, were subsequently endocytosed, accumulated into large phagocytic vacuoles, and eventually degraded by the nearby Sertoli cell. When the spermatocyst ruptured, spermatozoa containing sparse cytoplasm were released into the excurrent duct system. During spermiogenesis, both the nuclear and cytoplasmic volumes decreased substantially (80%, 92% respectively) leading to an overall 87% reduction in total cell volume.

Spermiogenesis in the red-ear turtle (Pseudemys scripta) and the domestic fowl (Gallus domesticus): a study of cytoplasmic events including cell volume changes and cytoplasmic elimination

Nuclear and cytoplasmic volume changes as well as the elimination of residual spermatid cytoplasm were investigated in the red-ear turtle (Pseudemys scripta) and the rooster (Gallus domesticus). Nuclei of newly formed spermatids which were originally centrally located became eccentrically located within the cell in both species. Shortly thereafter the nuclear pole of the spermatid was found situated within deep crypts of a Sertoli cell. The cytoplasm of elongating spermatids was displaced along the nonacrosomal region of the nucleus and the proximal flagellum. In both species sheetlike Sertoli cell processes indented spermatid cytoplasm adjacent to the nucleus and appeared to segregate small packets of the cytoplasm. In the turtle, these packets of cytoplasm were separated from the spermatid. In both the turtle and rooster, a portion of the spermatid cytoplasm was displaced forward over the acrosomal region of the spermatid to resemble a hood. As spermatids were transported to the seminiferous tubular lumen, cytoplasmic lobes which projected forward of the spermatid head were formed by preferential flow of cytoplasm into one aspect of the cytoplasmic hood. In both species, at sperm release the cytoplasmic lobe was disengaged from the spermatid head to form a large residual body that was internalized and degraded within the Sertoli cell. Medium-sized cytoplasmic lobes were pinched from the head and neck region of the turtle and rooster spermatids, respectively. In the turtle, small-sized mitochondrial-rich cytoplasmic fragments budded from the caudal head and midpiece of the spermatids and were phagocytosed by the Sertoli cell. Thus, cytoplasmic elimination occurred through 1) segregation of cytoplasmic packets by Sertoli penetrating processes (turtle), 2) elimination of large and medium-sized residual bodies from the head (turtle and bird), and 3) budding of small mitochondrial-rich cytoplasmic fragments from the region of the midpiece (turtle). In the turtle a 79% reduction in total cell volume occurred during spermiogenesis which was the result of an 84% cytoplasmic reduction and a 78% nuclear reduction. During spermiogenesis, the rooster lost 97% of its total cell volume due to a 97% cytoplasmic volume change and a 96% nuclear volume change.

Germ cell-somatic cell relationships: a comparative study of intercellular junctions during spermatogenesis in selected non-mammalian vertebrates

Specialized germ cell-somatic cell relationships were surveyed in the testis of species representative of four classes of non-mammalian vertebrates. Desmosome-like junctions were present in all classes studied. In the teleost fish studied (bluegill; Lepomis macrochirus), small, infrequent desmosomes, seen between the spherical cyst cells and spermatocytes, were characterized by poorly represented subsurface densities. In the bullfrog (Rana catesbeiana), similar desmosome-like junctions were found between cyst cell processes and spermatocytes. Reptilian (turtle; Pseudameys scripta) desmosome-like junctions between Sertoli cells and germ cells were heterogeneous and more numerous than those junctions found in fish and amphibians. In general, the reptilian desmosome-like junctions were extensive structures displaying 10 nm filaments associated with the Sertoli cell component of the junctions. Regions within the desmosome where the two plasma membranes converged suggested that gap junctions were a component of the desmosome-like junctions. "Desmosome-gap" junctions persisted in turtle spermatids for sometime after nuclear elongation had commenced. In birds (chicken; Gallus domesticus), "desmosome-gap" junctions, similar to those seen in turtles were described between both spermatocytes and Sertoli cells, and spermatids and Sertoli cells. These junctions were frequently lined by saccules of endoplasmic reticulum. The presence of gap junctions suggest the evolution of mechanisms for somatic cell-germ cell communication although more species should be examined to confirm this hypothesis.

A comparative study of Sertoli cell ectoplasmic specializations in selected non-mammalian vertebrates

Ectoplasmic specializations (ES) facing spermatids were studied in species representative of four classes of non-mammalian vertebrates (Pisces--bluegill; Amphibia--bullfrog; Reptilia--red eared turtle; Aves--domestic chicken). ES was not seen in the bluegill but was present in all other species studied. In the frog, turtle, and chicken, ES did not resemble its mammalian counterpart and could only be characterized by the presence of 6 nm filaments (presumedly actin) within the somatic cell facing the head region of elongating spermatids. ES filaments were sparse in the frog and were sometimes associated with more deeply situated endoplasmic reticulum. Turtle ES filaments were abundant and encircled the acrosomal region of the spermatid head and were delimited by fenestrated saccules of endoplasmic reticulum. In the chicken, ES filaments were prominent but less abundant than in the turtle. Six nanometer filaments of the chicken ES appeared in a tangled mass and were not associated with clearly defined endoplasmic reticulum. In the three species where ES was found, it first developed as spermatids became entrenched within the surrounding somatic cell. Neither cell elongation, nuclear elongation, or movement of the nucleus to the cell surface was synchronized with the onset of ES development. That ES development was seen concomitant with spermatid entrenchment and spermatid orientation suggested a role for ES in these processes. This hypothesis was further strengthened by observations in the fish where ES was lacking and where spermatid entrenchment within the somatic cell, did not occur. The study also supported the hypothesis that ES acts as a cytoskeletal mantle to which other cytoskeletal elements within the cell interact to affect the position of elongate spermatids within the epithelium. The dissolution of ES prior to spermiation and concomitant loss of a close relationship between cells suggests that ES is also related to somatic cell-germ cell adhesion and therefore plays an important role in the spermiation process.

Comparative study of cytoplasmic elimination in spermatids of selected mammalian species

In the transformation of a spermatid into a spermatozoon, cytoplasmic loss occurs, allowing the sperm to swim unhindered. Cytoplasmic loss takes place via elimination of the residual body and through structures known as tubulobulbar complexes. A determination of cytoplasmic loss in several species was undertaken by using high-resolution electron microscopic morphometric techniques. During the period that tubulobulbar complexes are present, an average 53% cytoplasmic loss was recorded for five species (guinea pig, 48.8 +/- 6.2% (SEM); monkey, 60.3 +/- 4.3%; opossum, 54.5 +/- 4.4%; rabbit, 46.9 +/- 2.7%; and rat, 55.7 +/- 4.9%), whereas there was essentially no loss or gain in cytoplasm during the same period for round spermatids. Surprisingly, during spermatid elongation an approximate 36% loss of cytoplasm was also recorded for five species (guinea pig, 50.1 +/- 6.3%; monkey, 30.0 +/- 15.4%; opossum, 25.4 +/- 9.0%; rabbit, 42.4 +/- 8.6%; and rat, 34.9 +/- 11.9%), which is only partially (approximately 60%) accounted for by fluid pumping from the nucleus during nuclear condensation. A densification of the cytoplasm of elongate spermatids, as compared with round spermatids, suggests fluid is also pumped from the elongating spermatid cytoplasm. Fluid loss from germ cells may contribute to the seminiferous tubule fluid, a fluid previously thought to be solely of Sertoli-cell origin.