Different Days Of Gestation Research Articles

The effect of cigarette smoking on first-trimester crown-rump length.

Does cigarette smoking impact the embryonic growth rate in the first trimester? This is a retrospective multicentre observational study of 2912 pregnancies. Women who presented to the early pregnancy and perinatal ultrasound units between 2010 and 2019 were included in the study. The data collected included the following: smoking status, the crown-rump length (CRL) of the pregnancy at the first ultrasound that showed an embryonic heart rate, the gestation in days and the CRL at another ultrasound up to the nuchal translucency scan and the gestation in days. Additional demographic data included the following: age, weight, height, parity and mode of delivery.Of the 2912, complete smoking and demographic data were available for 657 pregnancies. One hundred and thirty-seven (26.3%) were smokers, and 520 (73.7%) were not. The rate of change of smokers vs non-smokers between two CRLs and two different days of gestation was calculated. The Wilcoxon rank sum test with continuity correction was used for statistical analysis. This gives a value of W = 31,940 and a P-value = 0.06. There is a slight shift in location for the smokers; however, it is not statistically significant. The insignificance may be due to the general large variance in growth rate. The impact of cigarette smoking on embryonic growth rate detected by CRL in the first trimester is statistically insignificant.

Effect of coumestrol on the histological feature of ovary of pups of F1 generation delivered from exposed mothers at different days of gestation

Phytoestrogens are the plant substances, which are structurally and functionally similar to steroids and produce estrogenic effects. It is well established that phytoestrogens when administered orally caused remarkable effects on the reproductive organs in females. It is also known that female rats, which consume more phytoestrogen for longer period, suffer from sterility. In the present study, efforts have been made to assess the effect of coumestrol on reproductive organs when exposed in uteroin mother and its effects on the development of postnatal pups.The administration of coumestrol during different days of pregnancy induced remarkable changes in the histological features of ovary of female rats of F1generation even at the age of 6 months.

Pregnancy upregulates angiotensin type 2 receptor expression and increases blood flow in uterine arteries of rats.

Normal pregnancy is associated with decreased uterine vascular contraction and increased blood flow even though angiotensin II (AngII) levels are increased. AngII not only activates the angiotensin type 1 receptor (AT1R) to mediate vasoconstriction but also angiotensin type 2 receptor (AT2R) to cause vasodilation. We hypothesized that upregulation of AT2R expression and function accounts for increased uterine artery blood flow during pregnancy. Virgin, pregnant (at different days of gestation) and post-partum Sprague-Dawley rats were used to determine uterine artery hemodynamics using micro ultrasound and plasma angiotensin II levels by ELISA. Isolated uterine arteries were examined for AT1R and AT2R expression and isometric contraction/relaxation. Plasma AngII levels were steady up to mid-pregnancy, increased as pregnancy advanced, reaching a peak in late pregnancy, and then restored to pre-pregnant levels after delivery. The pattern of increase in AngII levels mirrored a parallel increase in uterine blood flow. AT1R expression did not change, but AT2R expression increased during pregnancy correlating with uterine blood flow increase. Treatment with the AT2R antagonist PD123319 reduced uterine arterial blood flow. Vasoconstriction to angiotensin II was blunted in pregnant rats. Treatment with PD123319 caused greater enhancement of AngII contraction in pregnant than virgin rats. Ex vivo exposure of estradiol to uterine arterial rings dose dependently upregulated AT2R expression, that was inhibited by estrogen receptor antagonist. These results demonstrate that elevated AngII levels during gestation induce an increase in uterine blood flow via heightened AT2R-mediated signaling. Estrogens appear to directly upregulate uterine vascular AT2R independent of any endogenous factors.

Expression of FABP7 in mouse placenta tissue and human trophoblast HTR-8/Svneo cells

To detect the expression of FABP7 in the placenta of pregnant mice and in HTR-8/Svneo cells. Real-time PCR and immunofluorescence were used to detect FABP7 mRNA and protein expressions in the uterine and placental tissue of pregnant mice at different days of gestation. FABP7 expression was also detected in cultured HTR-8/Svneo cells using immunofluorescence assay. The mice were treated with E2, P4 or their combination for 6 and 24 h and Fabp7 mRNA level in the uterus was detected with real-time PCR. At 7.5-10.5 days of gestation, the pregnant mice showed positive expressions of Fabp7 mRNA in the uterus and placenta, and FABP7 protein was detected in the decidualized cells and trophoblast giant cells. The expressions of FABP7 were detected at both the mRNA and protein levels in cultured HTR-8/Svneo cells. In mice treated with P4 alone or with E2+P4 for 6 and 24 h, the expression level of Fabp7 mRNA was upregulated in the uterus. Fabp7 upregulation was observed in mice at 24 h following E2 treatment but not at 6 h. FABP7 is expressed in trophoblast giant cells and decidual cells in the placental tissue of mice and in cultured HTR-8/Svneo cells, suggesting the involvement of FABP7 in placental development and in maintenance of pregnancy. E2 and P4 can regulate the expression of FABP7 in mouse uterus.

Real-Time Monitoring of Placental Oxygenation during Maternal Hypoxia and Hyperoxygenation Using Photoacoustic Imaging.

PurposeThis preclinical study aimed to evaluate placental oxygenation in pregnant rats by real-time photoacoustic (PA) imaging on different days of gestation and to specify variations in placental oxygen saturation under conditions of maternal hypoxia and hyperoxygenation.Material and methodsPlacentas of fifteen Sprague-Dawley rats were examined on days 14, 17, and 20 of pregnancy with a PA imaging system coupled to high-resolution ultrasound imaging. Pregnant rats were successively exposed to hyperoxygenated and hypoxic conditions by changing the oxygen concentration in inhaled gas. Tissue oxygen saturation was quantitatively analyzed by real-time PA imaging in the skin and 3 regions of the placenta. All procedures were performed in accordance with applicable ethical guidelines and approved by the animal care committee.ResultsMaternal hypoxia was associated with significantly greater decrease in blood oxygen saturation (ΔO2 Saturation) in the skin (70.74% ±7.65) than in the mesometrial triangle (32.66% ±5.75) or other placental areas (labyrinth: 18.58% ± 6.61; basal zone: 13.13% ±5.72) on different days of pregnancy (P<0.001). ΔO2 Saturation did not differ significantly between the labyrinth, the basal zone, and the decidua. After the period of hypoxia, maternal hyperoxygenation led to a significant rise in oxygen saturation, which returned to its initial values in the different placental regions (P<0.001).ConclusionsPA imaging enables the variation of blood oxygen saturation to be monitored in the placenta during maternal hypoxia or hyperoxygenation. This first preclinical study suggests that the placenta plays an important role in protecting the fetus against maternal hypoxia.

Intestinal development of bovine foetuses during gestation is affected by foetal sex and maternal nutrition.

We aimed to evaluate the effects of maternal nutrition (MN) and foetal sex on the intestinal development of bovine foetuses throughout different days of gestation (DG). Forty-four multiparous, dry Holstein × Gyr cows with average initial body weight of 480±10kg were fed the same diet of either restricted feeding at 1.15% of body weight (CO, n=24) or fed adlibitum (overnourished, ON, n=20). Six cows from CO group and five cows from ON group were slaughtered at 139, 199, 241 and 268 DG, and foetuses were necropsied to evaluate the intestinal development. The mass, length and density of foetal intestines were not affected by MN (p≥0.260). An interaction between MN and DG was observed for the villi length of jejunum (p=0.006) and ileum (p<0.001). Villi length of jejunum and ileum was higher (p<0.10) in foetuses from ON-fed cows than in foetuses from CO-fed cows at 139 DG. However, at 199 DG, the villi length of jejunum and ileum of foetuses from CO-fed cows was higher than in foetuses from ON-fed cows. Despite these differences, MN did not affect the villi length of jejunum and ileum at 268DG (p>0.10). Female foetuses had greater small intestine mass (p=0.093), large intestine mass (p=0.022), small intestine mass in proportion to body mass (p=0.017) and large intestine mass in proportion to body mass (p<0.001) than male foetuses. Female foetuses had also longer small intestine (p=0.077) and greater small intestine density (p=0.021) and villi length of jejunum (p=0.001) and ileum (p=0.010) than males. We conclude that MN affects the pathway for the development of foetal villi length throughout the gestation in bovine foetuses without changing the final villi length. Female foetuses had higher intestinal mass, density and villi length than males during the foetal phase in bovines.

Decidual endothelium, Notch1 and TGFβ, gatekeepers for Treg accumulation at the maternal-fetal interface.

Decidual endothelium, Notch1 and TGF β , gatekeepers for Treg accumulation at the maternal–fetal interface

Effects of day of gestation and feeding regimen in Holstein × Gyr cows: I. Apparent total-tract digestibility, nitrogen balance, and fat deposition

This study investigated how feeding regimen (FR) alters apparent total-tract digestibility, performance, N balance, excretion of purine derivatives, and fat deposition in Holstein × Gyr cows at different days of gestation (DG). Forty-four pregnant multiparous Holstein × Gyr cows with an average initial body weight of 480±10.1 kg and an initial age of 5±0.5 yr old were allocated to 1 of 2 FR: ad libitum (AL; n=20) and maintenance level (ML; n=24). Maintenance level was considered to be 1.15% of body weight on a dry matter (DM) basis and met 100% of the energy requirements, whereas AL provided 190% of total net energy requirements. Data for hot and cold carcass dressing, fat deposition, average daily gain, empty body gain, and average daily gain without the gravid uterus were analyzed as a 4×2 factorial design. Intake, apparent total-tract digestibility, N balance, urinary concentration of urea, and purine derivatives data were analyzed as repeated measurements taken over the 28-d period (122, 150, 178, 206, 234, and 262 d of gestation). Cows were individually fed a corn silage-concentrate based diet composed of 93% roughage and 7% concentrate (DM basis) as a total mixed ration. Pregnant cows were slaughtered on 4 different DG: 139 (n=11), 199 (n=11), 241 (n=11), and 268 d (n=11). Overall, DM intake decreased as DG increased. This decrease observed in DM intake may be associated with the reduction in ruminal volume caused by the rapid increase in fetal size during late gestation. We observed an interaction for DM and organic matter apparent total-tract digestibility between FR and DG; at 150, 178, and 206 d of gestation, ML-fed cows had greater DM and organic matter apparent total-tract digestibility values than AL-fed cows. Rib fat thickness, mesentery, and kidney, pelvic, and heart fat were greater in AL-fed than in ML-fed cows at all DG, with the exception of rib fat thickness on d 139. Ad libitum-fed cows excreted more N in their feces and urine compared with ML-fed cows. Pregnant cows that were fed at maintenance had greater digestibility during some DG, excreted less N in feces and less N and urea in urine, and deposited less fat in the body. We therefore recommend ML (1.15% of body weight with 93% of roughage) as a FR for pregnant dry cows; however, during the last month of gestation, AL seems to be the most appropriate FR to avoid loss of body weight.

Effects of Pregnancy and Lactation on Iron Metabolism in Rats.

In female, inadequate iron supply is a highly prevalent problem that often leads to iron-deficiency anemia. This study aimed to understand the effects of pregnancy and lactation on iron metabolism. Rats with different days of gestation and lactation were used to determine the variations in iron stores and serum iron level and the changes in expression of iron metabolism-related proteins, including ferritin, ferroportin 1 (FPN1), ceruloplasmin (Cp), divalent metal transporter 1 (DMT1), transferrin receptor 1 (TfR1), and the major iron-regulatory molecule—hepcidin. We found that iron stores decline dramatically at late-pregnancy period, and the low iron store status persists throughout the lactation period. The significantly increased FPN1 level in small intestine facilitates digestive iron absorption, which maintains the serum iron concentration at a near-normal level to meet the increase of iron requirements. Moreover, a significant decrease of hepcidin expression is observed during late-pregnancy and early-lactation stages, suggesting the important regulatory role that hepcidin plays in iron metabolism during pregnancy and lactation. These results are fundamental to the understanding of iron homeostasis during pregnancy and lactation and may provide experimental bases for future studies to identify key molecules expressed during these special periods that regulate the expression of hepcidin, to eventually improve the iron-deficiency status.

Pregnancy-associated glycoprotein (PAG) concentration in plasma and milk samples for early pregnancy diagnosis in Lacaune dairy sheep

In the present study, four RIA systems (RIA-1 to -4) based on two antisera raised against ovine pregnancy-associated glycoproteins (ovPAGs), combined with an ovine or a bovine PAG tracer were used to measure PAG concentrations in plasma and milk samples of dairy ewes. Blood and milk samples were collected on different days of gestation: 0, 18, 20, 22, 25, 28, 32, 42, and 49. From day 20 onward, the PAG in plasma could be detected in all pregnant ewes using the four RIA systems. By using milk, except for RIA-1, the other systems showed a sensitivity of 100% from day 28 of gestation onward. In plasma, PAG concentrations were higher in multiple than in single pregnancies, while no clear relationship was observed in milk. In conclusion, milk is a good alternative to plasma for early pregnancy diagnosis in sheep from day 28 to day 42.

Analysis of Circulating DNA Distribution in Pregnant and Nonpregnant Dairy Cows1

Circulating nucleic acids (CNAs) are free-floating, cell-free DNA and RNA molecules in the circulation of healthy and diseased humans and animals. The aim of this study was to identify differences in CNA distribution in serum samples from multiparous pregnant (n = 24) and nonpregnant (n = 16) dairy cows at different days of gestation (Days 0, 20, and 40). A modified serial analysis of gene expression procedure was used to generate concatemerized short sequence tags from isolated serum DNA. A total of 6.1 × 10(6) tags were recovered from analyzed samples (n = 40). Significant differences between the pregnant and nonpregnant groups were detected in chromosomal regions, protein-coding sequences, and single genes (P < 0.05). Approximately 23% (1.4 × 10(6) tags) of the total sequence pool were present exclusively in the analyzed serum samples of pregnant cows. Of these tag sequences, seven originated from genomic regions and 13 from repetitive elements. Comparative BLAST analysis identified the repetitive tags as BovB (non-long terminal repeat retrotransposons/long interspersed nuclear elements), Art2A, BovA2, and Bov-tA2 (short interspersed nuclear elements). To our knowledge, this is the first study to comprehensively characterize the circulating, cell-free DNA profile in sera from pregnant and nonpregnant cows across early gestation.

The Relationship Between the Positive Identification of the Embryo Proper in Equine Pregnancies Aged 18-28 Days and its Future Viability: A Field Study

Early embryonic loss (EEL) negatively affects the reproductive efficiency of equine reproduction. A sign of future EEL is when the embryo proper (EP) fails to develop within the embryonic vesicle after 30 days of gestation. The earlier the identification of impending EEL, the earlier the mare can be rebred to allow a second chance of pregnancy. The objectives of this study were to determine the percentage of embryonic vesicles with a visible EP at 18-28 days of gestation and to study the association between the presence/absence of the EP at different days of gestation and the future viability of the pregnancy. A total of 1,256 pregnancies were identified and followed by transrectal B-mode ultrasonography 12-45 days post ovulation in mares of the same Thoroughbred farm. The identification of the EP was attempted once during days 18-28. Pregnancy reconfirmation was performed on days 35-45. The percentage of vesicles with an EP increased gradually from days 18 (2.8%) to 21 (86.9%) (P < .05). From day 20 onward, the EEL rate of mares with vesicles without an EP was significantly higher (P < .05) than that of vesicles with a positive identification of an EP. In conclusion, the EP of the equine vesicle can be identified reliably with B-mode ultrasonography in the majority of mares (>71%) on day 20 of gestation. The lack of a positive identification of an EP from day 20 onward is associated with a higher EEL rate.

Changes in the biochemical composition of fetal fluids and maternal blood serum during different days of gestation in cattle

The aim of this study was to determine the values of some metabolites, ions, and enzymes in maternal blood serum and fetal fluids in relation to gestation day in cattle. Gravid uteri of cattle were collected after slaughter. The allantoic and amniotic fluids as well as maternal blood samples were collected. Fetal ages were determined according to crown–rump length by applying the age estimation formula that previously was presented for cattle. The pregnancies were divided according to gestation days into four groups: 0–50, 51–100, 101–150, and 151–200 days. With the progress of pregnancy, the biochemical levels of fetal fluids and maternal serum changed as follows: there was a rise of total protein, urea, creatinine, and alkaline phosphatase values in fetal fluids and serum; the levels of glucose in maternal serum and potassium in fetal fluids increased; cholesterol, triglyceride, phosphorus, and sodium contents of fetal fluids and serum decreased; the concentrations of glucose and calcium in fetal fluids, lactate dehydrogenase (LDH) in serum and allantoic fluid, potassium in serum, and aspartate aminotransferase (ASAT) in amniotic fluid and serum dropped. The values of LDH in amniotic fluid, ASAT in allantoic fluid, alanine aminotransferase in amniotic and allantoic fluids, and calcium in maternal serum remained unchanged.

Quantitative Changes of Sialoadhesin and CD163 Positive Macrophages in the Implantation Sites and Organs of Porcine Embryos/Fetuses During Gestation

Porcine reproductive and respiratory syndrome virus (PRRSV) crosses the placenta most easily in the last third of gestation. Further, PRRSV does not replicate in preimplantation embryos but does replicate in postimplantation embryos and fetuses. In the present study, it was aimed to find an explanation for these observations by localization and quantification of the macrophages carrying two entry mediators that play a crucial role in PRRSV replication, sialoadhesin (Sn) and CD163, in the implantation sites and organs of embryos/fetuses during gestation. Uterus and embryos or organs (liver, spleen, lungs) from fetuses were obtained from pregnant PRRSV negative sows at different days of gestation (20–35, 50–60, 70–80, 114) and the Sn+ and CD163+ macrophages were quantified. In endometrium and placentas, two macrophage subsets were observed: Sn−CD163+ and Sn+CD163+. The highest number of Sn+ and CD163+ macrophages was counted at 114days of gestation. In the mid-gestation fetal placentas (50–60days of gestation), most CD163+ macrophages were Sn negative. The number of Sn+ and CD163+ macrophages in organs increased during gestation. In the liver, the Sn+ and CD163+ macrophages were most abundant (Sn+: 8.1–48.7%; CD163+: 22.0–55.0%); the lowest number of Sn+ and CD163+ macrophages was observed in the lungs (Sn+: 0–15.2%; CD163+: 4.0–19.3%). Double immunofluorescence staining revealed three macrophage subsets in the spleen: Sn+CD163−, Sn−CD163+ and Sn+CD163+; and two macrophage subsets in the lungs: Sn−CD163+ and Sn+CD163+. In the liver, due to physiological presence of biotin, the double immune-fluorescence staining could not be performed. The present results show clear changes in the quantity of Sn+ and CD163+ macrophages in the placentas and organs of embryos/fetuses during gestation which most probably have a physiological basis. The absence of Sn on macrophages in the fetal placenta at mid-gestation might explain the difficulty for PRRSV to spread transplacentally at this stage of gestation.

Tissue-specific distribution of the androgen receptor (AR) in the porcine fetus

The aim of this study was to investigate androgen receptor (AR) expression in developing porcine fetuses. The localization of AR was examined on embryos obtained at different days of gestation: days 18, 32, 50, 71, 90 post coitum (p.c.), and in the several tissues collected from the newborn piglets of both sexes. AR expression was first observed on day 32 p.c. in the mesonephron region. RT-PCR did not show AR mRNA on day18 p.c., but the message was present starting from day 32. In the male differentiating gonads and in the male genital ducts AR protein was present at 50, 71 and 90 days of gestation. AR protein was also detected in the cords of stromal cells within the medulla of the ovary and in stromal cells investing the oogonial nests. Pregranulosa cells on day 90 of gestation and on day 1 post partum (p.p.) immunolabelled positively for AR. In the kidney, a number of AR-positive tubules were visible while the mesenchyme in the kidney was AR-negative. Immunoreactive AR was detected predominantly in the nuclei of epithelial cells of the budding component at different stages of gestation of porcine lung. The presence of AR during gestation in non-gonadal tissues suggests a role of androgen in these tissues.

Aminiotic Fluid and Intrauterine Growth Restriction in a Gastroschisis Fetal Rat Model

Fetuses with digestive anomalies such as gastroschisis may present intrauterine growth restriction (IUGR) and shortened intestines. Objective: The aim of this study was to assess the influence caused by amniotic fluid (AF) in intestinal length and somatic growth in an experimental gastroschisis fetal model at two distinct gestational ages. Material and Method: Fetal rats were operated according to Correia-Pinto on 2 different days of gestation: day 18.5 (group I) and day 19.5 (group II). Each group was divided into three sub-groups: fetuses with gastroschisis (G), control (C) and sham(S). Body measurements and histological analysis were done. Result: Body measurement analysis showed: average body weight (g) in group I was G = 5.32, C = 5.68, S = 5.86; group II was G = 5.32, C = 5.80, S = 5.66. Average intestine weight (g) in group I was G = 0.283, C = 0.238, S = 0.231; group II was G = 0.272, C = 0.231, S = 0.233. Average intestine length (mm) in group I was G = 125, C = 216, S = 209; group II was G = 148, C = 226, S = 226. Histological analysis showed a decrease in the number and size of the intestinal microvillae and a light edema of serosa. Conclusion: Gastroschisis had a direct correlation with IUGR and the time of exposure of the fetuses to AF had no influence on body weight in gastroschisis fetuses but did interfere with intestinal length.

Distinct neural precursors in the developing human spinal cord.

Both embryonic and adult central nervous system have been shown to contain multipotent neural stem cells, but it is not yet clear whether they consist of a single or distinct populations of neural precursors. Since embryonic human neural precursors, particularly in the spinal cord, have not been extensively characterized, we have studied their behaviour at different days of gestation and in different culture conditions. Depending on dissociation and culture conditions, neurospheres which contain nestin- and vimentin-positive or only vimentin-positive neural precursors can be isolated. Whereas the former can be isolated only at early developmental stages, the latter appear to be present at all the stages examined, between 45 and 89 days of gestation. Furthermore, comparison of the effect of FGF, EGF and the two factors in combination on colony formation shows an additive effect of the two growth factors, indicating the existence of more than one type of neural precursor. Overall our results suggest that the human spinal cord contains distinct and dynamic populations of neural precursors which are developmentally regulated.

Dynamics of betaig-h3 mRNA expression during pregnancy in the uterus and the placenta of the mouse: a possible regulatory factor for trophoblastic invasion.

Changes in the betaig-h3 gene expression levels in the uterus during different reproductive stages and those in the placenta on different days of gestation in the mouse were examined by Northern blot analysis. The levels of betaig-h3 expression rose steeply from the baseline level at proestrus to the maximum at estrus and then declined rapidly from 1st day of diestrus onward. During pregnancy, high levels of betaig-h3 mRNA were detected in the uterus on Day 4 of gestation, when the trophoblastic invasion of the implanted blastocysts was very active. In the pseudopregnant uterus, the betaig-h3 expression levels exhibited the same patterns as those in the pregnant uterus, although the levels were much lower at all stages than those in the pregnant uterus. In the placenta, the betaig-h3 expression levels gradually increased from Day 7 onward and peaked on Day 18 of gestation. In situ hybridization analysis of the pregnant uterine tissues revealed that the luminal as well as the glandular epithelium expressed betaig-h3 mRNA at high levels. In the placenta, high levels of betaig-h3 transcripts were detected in the decidual cells and the giant trophoblast cells. These findings suggest that betaig-h3 might play a role in regulating the invasiveness of trophoblast cells during implantation and placentation of hemochorial type when extensive trophoblastic invasion of the endometrium takes place.

Nitric oxide synthases in pregnant rat uterus.

The conversion of [14C]arginine into [14C]citrulline as an indicator of nitric oxide synthesis was studied in uteri isolated from rats on different days of gestation, after labour and during dioestrus. Nitric oxide synthesis was present in uterine tissues isolated at each stage of gestation and also in tissues collected during dioestrus and after labour. Expression of neuronal nitric oxide synthase was not detectable at any of the stages studied. Endothelial nitric oxide synthase was present at all the stages studied, but there was a significant increase on day 13 of gestation and a decrease thereafter, with the lowest expression recorded on the day after labour. Inducible nitric oxide synthase expression in rat uteri increased substantially during pregnancy, with the highest expression on day 13 of gestation; expression decreased at term and after labour. The changes in expression of inducible nitric oxide synthase were coincident with the changes in nitric oxide synthase activity in uteri treated with aminoguanidine. Thus, these findings indicate that an increase in expression of inducible nitric oxide synthase in the uterus may be important for maintenance of uterine quiescence during pregnancy and its decrease near the time of labour could have an effect on the start of uterine contractility.

Apoptosis in mouse fetuses from dams exposed to T-2 toxin at different days of gestation

T-2 toxin (2 mg/kg b.w.) was orally inoculated to pregnant mice at gestational day (GD) 8.5, 9.5, 10.5, 11.5, 12.5, 13.5, 14.5, 15.5 and GD 16.5, respectively, and the fetuses were examined 24 hours later. The number and region of pyknotic or karyorrhectic cells varied according to inoculation date. In the GD 13.5-subgroup, a moderate to high number of pyknotic or karyorrhectic neuronal cells were observed in the central nervous system, peri-ventricular zone to subventricular zone, and pyknosis or karyorrhexis were also observed in a small number of chondroblasts and chondrocytes. In the GD 16.5-subgroup, a moderate to high number of pyknotic or karyorrhectic cells were observed in the thymus and renal subcapsular parenchyma. The nuclei of these pyknotic or karyorrhectic cells were strongly stained by the terminal deoxy nucleotidyl transferase (TdT)-mediated dUTP-digoxigenin nick end labeling method widely used for the in situ detection of apoptotic nuclei. In addition, a few fetuses from dams which were given T-2 toxin at GD 13.5 or GD 14.5 and killed at GD 17.5 showed skeletal abnormalities such as wavy ribs and short scapula. From the present findings and the well known fact that T-2 toxin readily crosses the rat placenta, it seems that T-2 toxin-induced apoptosis in the developing mouse fetuses might be a direct effect of T-2 toxin on fetuses.