Lectin teratogenesis. II: Demonstration of increased binding of concanavalin A to limb buds of rabbit embryos during the teratogenically sensitive period

The plant lectin concanavalin A (con A) causes malformations of rabbit embryos when 160 micrograms (in 40 microliter) are injected into the exocoelom on gestational days 12-15 but does not cause malformations on days 10-11. The purpose of this study was to investigate the mechanism for increased susceptibility of day 12-15 embryos to con A teratogenicity. Light microscopy of day 11 embryos 15-20 hr after treatment with con A revealed no observable difference from controls. Day 13 embryos at similar times exhibited limb buds with large areas that were denuded of ectoderm. Concurrent addition of alpha-methyl-D-mannoside (alpha MM), a specific inhibitor of con A, to the injection solution of day 13 embryos resulted in limb buds that appeared normal. The regions of con A binding to day 11 and day 13 embryos were visualized through epifluorescent microscopy of untreated embryos stained with fluorescein-labelled con A. Day 11 embryos exhibited moderate fluorescence on the surface of limb buds and the pericardial region. Day 13 embryos exhibited strong fluorescence of limb bud surfaces; the pericardial region remained moderately fluorescent. Addition of alpha MM to the incubation medium resulted in no fluorescence above background. Visualization of con A receptors was accomplished by ultrastructural analysis of forelimb buds stained with ferritin-labelled con A. Ferritin label was observed only on the surfaces of the ectoderm and was sparse over all regions of day 11 limb buds. In contrast, ferritin label was moderately heavy in all regions of the day 13 limb buds. No labelling occurred when the ferritin-labelled con A was preincubated with alpha MM. These observations indicate that the number of exposed con A receptors on limb buds of teratogenically sensitive embryos (day 13) is increased, compared with the number of exposed receptors on limb buds of younger, insensitive (day 11) embryos. The increased number of exposed con A receptors on limb buds during the teratogenically sensitive period provides not only increased binding of the lectin to sensitive embryos but also a potential mechanism for the anomalous attachment of distal regions of the limb buds to the body wall.

Morphogenesis of the secondary palate in mouse embryos with special reference to the development of rugae

Morphological studies of secondary palate formation, with special reference to the development of rugae, were carried out on Jcl:ICR mouse embryos. Three rugae were observed on the anterior part of the future oral surface of the vertically developing palatal shelves in 13-day embryos. Rugae increased in number as the development of the palatal shelves proceeded, and five to six prominent rugae were observed in 14-day embryos just prior to shelf elevation. The folding of these five to six rugae progressed in conjunction with the formation of a sharp, valley-like groove at the base of the anterior two-fifths of the vertical palatal shelves. As palatal shelves elevated, the groove disappeared gradually, and, accordingly, the folding of rugae loosened. In the groove region, the superficial epithelial cells were roundish, while the basal ones were elongated. Such characteristic features were no longer observed when the disappearance of the groove was completed. Eight rugae were observed on the future hard palate of 14-day embryos with already completed palatal fusion. An additional ruga was frequently found in 15-day embryos, and the pattern then was almost the same as that of an adult. Epithelial thickening and condensation at the rugae region, as well as mesenchymal condensation under the epithelium of the rugae, were confirmed in embryos both before and after elevation of the palatal shelves. There is a possibility that these structural characteristics observed in the epithelial and mesenchymal cells of the rugae and groove regions may be related to palatal shelf elevation.

Epicardial formation in embryonic chick heart: computer-aided reconstruction, scanning, and transmission electron microscopic studies

Epicardial formation in the embryonic chick heart from initial to final stages was revealed by means of computer-aided reconstructions based on serial resin sections for light microscopy, with further detailed observations using scanning and transmission electron microscopy. The origin of the epicardium was recognized as protrusions of mesothelial cell clusters on the right side of the external surface of the sinus venosus at 23 somites (stage 14+). These protrusions elongated to give rise to several villous processes, the tips of which eventually touched the dorsal wall of the embryonic heart at 30 somites (stage 17). Originating from these adhesion sites, mesothelial cells spread gradually onto myocardial cells in all directions to form a monolayered sheetlike cover. Thus, by stage 23, the ventricle was completely overlaid with epicardium, and blood-island-like structures appeared within the subepicardial layer. The atrium was not enveloped by epicardium until stage 25, and the extreme distal end of the bulbus cordis was reached by the advancing epicardium at stage 27. A chronological table of epicardial formation in the chick heart is presented.

Follow-up study of reconstructed auricle in microtia: comparison of the results of the rib cartilage framework and the silicone rubber framework methods

Plastic surgery for microtia had achieved fairly consistent good results since TANZER (Plast. Reconstr. Surg. 23: 1-15, 1959) and recently the modified methods have become popular. The authors did plastic surgery of auricles with the rib cartilage framework method from 1968 until 1986, and with the silicone rubber framework method from 1975 until 1986, and observed each postoperative course for 2 to 10 years. The operative results and the merits and the demerits of each method are reported here. The subjects were 49 ears for the rib cartilage framework method (17 of the former period, 1968-1977, and 32 of the latter, 1978-1986), and 20 ears for the silicone rubber framework method. The operation was performed in 3 stages according to the modified Tanzer's method. The results of operations were subjectively assessed as "satisfied," "fairly satisfied," "a little unsatisfied," and "unsatisfied." The results were as follows: 1) in the rib cartilage framework method, there were 21 satisfied cases (43%), 17 fairly satisfied cases (35%), and 5 unsatisfied cases (10%); 2) there were 8 satisfied cases (40%), 5 fairly satisfied cases (25%), and 6 unsatisfied cases (30%) in the silicone rubber framework method. From the aspect of postoperative management, the rib cartilage framework method is now better but the authors expect the silicone rubber framework method will be improved and used more extensively in the future.

Elevated expression of proto-oncogenes accompany enhanced induction of heat-shock genes after exposure of rat embryos in utero to ionizing irradiation

We have recently found that the effects of exposing rat embryos in utero to teratogens capable of producing cardiac anomalies were expressed later as enhanced induction of heat-shock proteins (hsp70 family) when embryonic hearts were cultured in vitro. However, it remained to be determined whether heat-shock proteins are induced in vivo after exposure to teratogens. The heat-shock response in some mammalian systems is known to be accompanied by elevated expression of proto-oncogenes. Using gene-specific DNA probes, we examined the levels of the expression (transcription) of heat-shock protein genes and two nuclear proto-oncogenes, c-fos and c-myc, in the embryos removed from irradiated pregnant mother rats 4 or 5 days after the irradiation. We found that the levels of expression in vivo of the hsp70 and c-myc genes in the irradiated embryos increased by approximately twofold as compared with those in the control. The expression in vivo of the c-fos gene was not detected in either the irradiated or non-irradiated embryos. After 0.5-hr incubation in vitro of the embryos, however, the expression of the c-fos gene in the irradiated embryos was highly enhanced whereas the control showed no changes. Although the exact functions of these gene products still remain obscure, the enhanced expression of hsp70 gene(s) and the nuclear proto-oncogenes observed in the present study may reflect repair of intracellular damages and/or regeneration of tissue by compensatory cell proliferation, processes that may disturb the normal program of organogenesis.

Golgi study on the homozygote (Ml/Ml) of macular mutant mouse

The macular mutant mouse shows X-linked recessive inheritance and its hemizygote (Ml/y) is considered to be an appropriate model of Menkes kinky hair disease (MKHD). In this study the homozygote (Ml/Ml) was bred by coupling CuCl2-treated Ml/y with Ml/+ and was clinically and neuropathologically examined. The Ml/Ml had white fur color and curly whiskers from day 3, showed ataxia and tonic seizure on day 8 and gradually lost weight after day 10. It died with severe emaciation around day 15. These clinical features were improved by CuCl2 injection. Quantitative analysis showed that the dendritic arborization of the pyramidal cell in the treated Ml/Ml was delayed on days 14, 20, 30, 45 and 90 in comparison with that of the age-matched +/y. In the cerebellum of the Ml/Ml on day 14, some of the Purkinje cells showed abnormal changes such as somal sprouts, spine-like structures on the surface of the soma and stem dendrites, thick stem dendrites, multiple focal swellings of the stem and distal dendrites, reduction in the size of dendritic trees and axonal focal swellings. These changes were gradually improved in the Ml/Ml with CuCl2 treatment after day 20, with the exception of the multiple focal swellings of the stem and distal dendrites. The dendritic focal swelling gradually decreased after day 45. These clinical and neuropathological features of the Ml/Ml are almost same as those of the Ml/y. In our mutant mouse, when the treated Ml/Ml is coupled with the treated Ml/y all offspring from the Ml/Ml are genetically Ml/y or Ml/Ml. Our study indicates that these fetal mice may be useful for studying the pathological and biochemical condition of prenatal MKHD.

Dendrites, dementia and the Down syndrome

Findings from a Golgi study of the visual cortex in patients with the Down syndrome were compared with those from neurologically normal, age-matched control subjects. The dendritic atrophy seen in childhood continued into adulthood, with a marked decrease in dendritic branching, dendritic length, and spine frequency in elderly adults with the Down syndrome. Subject more than 30 years old occasionally had degenerating pyramidal neurons in the cerebral cortex and degenerated pyramidal neurons and aspiny stellate cells, particularly in the temporal cortex. These dendritic abnormalities may be related to mental retardation in children and early dementia in older adults who have the Down syndrome. The genetic and extrinsic factors may be important determinants of Alzheimer type dementia in the Down syndrome.

Blastomere karyotyping and transfer of chromosomally selected embryos. Implications for the production of specific animal models and human prenatal diagnosis

A method is described that permits the generation of four isolated blastomeres after embryo splitting of murine four-cell eggs and the subsequent chromosomal analysis of one of the obtained 1/4-blastomeres. According to the karyograms obtained, embryos can be selected for reimplantation and furthermore triplicated via the embryo splitting procedure. By employing the described experimental setup, it is possible specifically to produce trisomy 16----2n aggregation chimeras as a postnatal model system of human Down's syndrome. The design can also be used for embryo sexing in stock farming and the selective reproduction of sexed farm animals via embryo transfer. Furthermore the application of blastomere karyotyping in human genetic counseling is discussed for the descendants of carriers of Robertsonian translocations. In addition the reported method could be employed for the genotypic identification of early homozygous embryonic stages from persons carrying frequent recessive mutations. The proposed design could, therefore, widen the spectrum of prenatal diagnosis.

Kabuki make-up (Niikawa-Kuroki) syndrome: a study of 62 patients

These 62 patients with the Kabuki make-up syndrome (KMS) were collected in a collaborative study among 33 institutions and analyzed clinically, cytogenetically, and epidemiologically to delineate the phenotypic spectrum of KMS and to learn about its cause. Among various manifestations observed, most patients had the following five cardinal manifestations: 1) a peculiar face (100%) characterized by eversion of the lower lateral eyelid; arched eyebrows, with sparse or dispersed lateral one-third; a depressed nasal tip; and prominent ears; 2) skeletal anomalies (92%), including brachydactyly V and a deformed spinal column, with or without sagittal cleft vertebrae; 3) dermatoglyphic abnormalities (93%), including increased digital ulnar loop and hypothenar loop patterns, absence of the digital triradius c and/or d, and presence of fingertip pads; 4) mild to moderate mental retardation (92%); and 5) postnatal growth deficiency (83%). Thus the core of the phenotypic spectrum of KMS is rather narrow and clearly defined. Many other inconsistent anomalies were observed. Important among them were early breast development in infant girls (23%), and congenital heart defects (31%), such as a single ventricle with a common atrium, ventricular septal defect, atrial septal defect, tetralogy of Fallot, coarctation of aorta, patent ductus arteriosus, aneurysm of aorta, transposition of great vessels, and right bundle branch block. Of the 62 KMS patients, 58 were Japanese, an indication that the syndrome is fairly common in Japan. It was estimated that its prevalence in Japanese newborn infants is 1/32,000. All the KMS cases in this study were sporadic, the sex ratio was even, there was no correlation with birth order, the consanguinity rate among the parents was not high, and no incriminated agent was found that was taken by the mothers during early pregnancy. Three of the 62 patients had a Y chromosome abnormality involving a possible common breakpoint (Yp11.2). This could indicate another possibility, i.e., that the KMS gene is on Yp11.2 and that the disease is pseudoautosomal dominant. These findings are compatible with an autosomal dominant disorder in which every patient represents a fresh mutation. The mutation rate was calculated at 15.6 X 10(6).

Extragonadal distribution of primordial germ cells in the early chick embryo

Chick primordial germ cells (PGCs), after separation from the endoderm in early embryonic development, temporarily circulate via the blood vascular system and finally migrate into the gonadal anlagen. It has been noted by some authors that some PGCs are present in extragonadal sites in some vertebrates. In the present study, we examined the distribution and localization of PGCs in extragonadal sites in the chick embryo. PGCs were identified by periodic acid-Schiff staining with light microscopy. In embryos at stages 20-24 (PGCs are in the settlement stage in the gonadal primordium), approximately 20% of the total number of PGCs were observed in extragonadal regions. Approximately 90% of these ectopic PGCs were found in the head, mainly in the mesenchyme surrounding the neural tube. Even at stage 14 when PGCs were usually circulating in the blood vessels, some of the PGCs had emerged from the blood vessels and were detected in the extragonadal site. This pattern of distribution of ectopic PGCs in the head area is probably attributed to the earlier, dominant development of the capillary network, and to the sluggish capillary blood flow in that region, which allows intravascular PGCs to escape into the tissue.

Reproductive toxicity tests: retrospect and prospect

1. The design of the classical three segment reproductive test for new drugs is described and the relative merits of the USA/EEC and the Japanese guidelines are discussed. 2. The importance of pharmacokinetic studies in the interpretation of teratology studies and extrapolation to humans is mentioned in relation to caffeine, sodium valproate and cyclophosphamide. 3. Changing ideas on the design of multi-generation studies are reviewed. 4. Recent developments in the fields of behavioural teratology, chemicals in breast milk and transplacental carcinogenesis are described.

Closure of the posterior neuropore in the vl mutant mouse

Alterations in the surface topography of cells in the apical neural folds of the posterior neuropore were analyzed by means of scanning electron microscopy in normal (+/+) and abnormal (vl/vl) embryos characterized by lumbosacral dysraphism. In early embryos (14-25 somites) surface features distinguishing the neuroepithelial cells, transitional zone cells, and surface ectoderm cells were similar in normal and abnormal embryos, as were the arrangement and configuration of filopodia and lamellipodia. However, in embryos with approximately 26-36 somites, the transitional zone of the abnormals showed a profusion of large blebs and excrescences along the entire length of the posterior neuropore. By 36 somites, the posterior neuropore was still variably open in the abnormals, in contrast to normal embryos in which no external opening could be detected. In view of the abnormalities associated with the transitional zone, it is possible that the underlying mechanism that results in lumbosacral spina bifida in this mutant may involve putative neural crest cells.

Fraser syndrome (cryptophthalmos-syndactyly syndrome): a review of eleven cases with postmortem findings

Detailed postmortem findings from 11 cases of probable Fraser (cryptophthalmos-syndactyly) syndrome are reported. Eight cases presented as neonatal deaths, one as a stillbirth, and there were 2 midtrimester fetuses. All of the cases had ocular, otic, digital, laryngeal, and renal abnormalities. Details of the pregnancies and sibship data are also reported. The possibility of prenatal diagnosis for this syndrome is discussed.

Teratogenic activity of lithium carbonate: an experimental update

The teratogenic potential of lithium carbonate was re-examined using mouse embryos as an experimental model. Externally it was found that, like many other psychoactive drugs, it exhibits a teratogenic activity that is confined to the development of the central nervous system. When administered intraperitoneally to pregnant females in doses ranging from 330 to 340 mg/kg at the very beginning of the ninth gestation day, i.e., during the critical period of the neural tube closure, it is embryotoxic, causes retardation of development, and induces the "neurotropic syndrome of malformations" comprising exencephaly, craniorachischisis, rachischisis, kinking of the spinal cord, and dilation of the fourth brain ventricle. Depending on the exact time of gestation when lithium carbonate is administered, the frequencies of exencephaly and spinal kinking after treatment 1 hour into the ninth day are compared with those after treatment 2 or 3 hours into the ninth day, incidence of exencephaly is increased at the later time and the incidence of spinal kinking is decreased.

Gross-structural defects in rats after acyclovir application on day 10 of gestation

Following three s.c. injections of acyclovir (100 mg acyclovir/kg) into rats on day 10 of pregnancy 19 litters were evaluated on day 21 of gestation and the effects were compared to the results obtained from controls (nine litters) which received the vehicle (0.1 N NaOH) only. The following results were obtained (treated group versus control group): 1) Implantations/litter: 11.2 +/- 1.3 versus 10.2 +/- 1.1; 2) resorptions/implantations: 27.7% versus 2.2%; 3) number of viable fetuses evaluated: 154 versus 90; 4) fetuses with anomalies of the skull: 78% versus 12%; 5) fetuses with anomalies of the vertebral column: 38% versus 13%; 6) gross-structural anomalies predominantly affected the skull and tail. The most frequently registered defects were: os tympanicum (smaller): 23%, os tympanicum (missing): 23%; missing tail: 7%; protruding tongue (15%); none of these defects were seen in the control fetuses. Postnatally we observed a high mortality rate among the offspring. From a total of 85 newborn (nine litters) we obtained 73 viable offspring (9.1 +/- 3.4); 81% of them had tail alterations. In the control group of eight litters (9.4 +/- 2.3) no tail alterations occurred. On day 21 postnatally 40 viable offspring were alive (mortality rate: 38.8%). Nearly all of these animals had visible alterations at multiple sites of their bodies; most frequently observed were: tail impairment, closed eyes, dragging hind-limbs, and urogenital alterations (e.g. testicular atrophy). These studies how for the first time that prenatal treatment with acyclovir induces gross-structural defects which persist postnatally.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of myometrial constriction in the induction of wavy ribs in rat fetuses

Furosemide, a loop diuretic, was orally administered to pregnant Crj: CD (SD) rats at a dose of 300 mg/kg once on day 16 of gestation. Cartilage bone double staining of day 17 fetuses revealed a delay in ossification. Characteristic rib deformities were not seen until day 18 of gestation. Concomitant with this observation were reductions in the amount of amniotic fluid, compared to controls, on day 18 of gestation and thereafter. When isoxsuprine HCl (2 mg/kg, b.i.d.), a uterine muscle relaxant, was additionally injected ip to pregnant rats on days 17-19 of gestation, the incidence of wavy ribs was significantly (P less than or equal to .05) less than that seen after treatment with furosemide alone. These observations indicate that the myometrial constriction plays a significant role in the induction of furosemide-induced wavy ribs.

Teratology study of Tween 60 in rats

The teratogenicity of Tween 60 was studied in Wistar rats. Pregnant rats were given Tween 60 at a dose of 0, 0.1, 1.0 or 10% in the diet from day 7 to day 14 of pregnancy. Daily intakes of Tween 60 were 99 mg/kg for the 0.1% group, 960 mg/kg for the 1.0% group and 7693 mg/kg for the 10% group. No change induced by Tween 60 was detected in the number, sex ratio and body weight of live fetuses. External, skeletal and internal examinations of the fetuses revealed no evidence of teratogenesis. It could be concluded that Tween 60 has no harmful effects on the prenatal development of the rat offspring at doses employed in the present study.

Embryotoxic effects of thalidomide-derivatives in the non-human primate Callithrix jacchus. I. Effects of 3-(1,3-dihydro-1-oxo-2H-isoindol-2-yl)-2,6-dioxopiperidine (EM12) on skeletal development

The response of pregnant marmosets (Callithrix jacchus) to the thalidomide derivative EM 12 was evaluated. EM 12 was selected for these studies because it is more active than thalidomide and is much more stable for hydrolysis. Skeletal gross structural abnormalities were observed when EM 12 was given to marmosets for 3-7 days during the period between days 49 and 60 post ovulation. Using the treatment schedule finally adapted in our laboratory, i.e. treatment during days 51-57 post ovulation, doses of 5 (or 10) mg EM 12/kg body wt induced the typical limb abnormalities known from man with an 80-100% certainty. In some animals we could observe the typical pattern of abnormalities even with doses as low as 1 mg EM 12/kg body wt. Abnormalities of the skeleton induced during this sensitive period are described. None of these (except some bifurcations of ribs) were seen in any of the ten litters (23 fetuses) serving as controls during the period of the study.

Embryotoxicity induced by alkylating agents: 5. Dose-response relationships of teratogenic effects of methylnitrosourea in mice

The teratogenic potency of the directly acting alkylating agent methylnitrosourea (MNU) was analysed in mice. Skeletal abnormalities were evaluated after treatment on either day 11 or 12 of pregnancy. Ectrodactyly was the predominant effect after treatment on day 11. Treatment on day 12 triggered especially double-sided microdactyly (method of analysis: measuring digit lengths). Litter variabilities were analysed using a new biometrical procedure. Using probit analysis, dose-response curves were computed from the experimental data obtained and the effective doses were calculated and compared with maternal toxicity. Low dose extrapolation was performed by use of various mathematical models which yielded very similar ED1/100 and ED1/1000 values.

Behavior of chick primordial germ cells moving toward gonadal primordium in vitro: scanning electron microscopic study

Primordial germ cells (PGCs) from embryonic chick blood were cultured in vitro and the cells being attracted by the gonadal primordium (germinal ridge; GR) were studied by scanning electron microscopy (SEM). Immediately after confirming PGC locomotion by 16-mm time-lapse filming or time-lapse video recorder under the microscope, PGCs in various phases of locomotion were prepared for SEM, and their locomotion was analyzed. With the thin collagen layer as a substrate, the sequence of the PGC locomotion was as follows: 1) The PGC produced a small pseudopodium. 2) This pseudopodium enlarged to the GR, and PGC-substrate contact was consolidated around the periphery of the pseudopodium, while the body of PGC remained detached from the substrate. 3) Finally, the PGC as a whole moved toward the GR, being trailed by the process. The locomotion of the PGC on the thick collagen layer as a three-dimensional substrate was as follows: 1) The PGC protruded a pseudopodium in the direction of the GR. 2) This pseudopodium elongated through the collagen network. 3) The tip of the pseudopodium swelled and the main body of the PGC flowed into the swelling portion, leaving a slender cytoplasmic tail. 4) The tail was finally incorporated into the leading part of the cell. This behavior of the PGC seemed to reflect the features of interstitial PGC in vivo.

Nonparenchymal liver cells and granulomas during lamprey biliary atresia

Transmission (thin sections and freeze-fracture replicas) and scanning electron microscopy were used to describe the nonparenchymal liver cells during the seven (1-7) stages of metamorphosis in the sea lamprey, Petromyzon marinus L., when bile ducts and canaliculi degenerate. The biliary atresia is accompanied by an increased diameter of fenestrae in the endothelium, an active phagocytosis by Kupffer cells in the sinusoids, and large lipid inclusions in perisinusoidal lipocytes (fat-storing or Ito cells). Plasma-like cells and foci of nonparenchymal cells (granulomas) are present in the liver interstitium during at least four stages of metamorphosis. The fenestrae in the sinusoidal wall are wider (up to 2.8-micron diameter) than normally reported for vertebrate livers but are likely a reflection of the morphogenetic and physiological events and consequences of the biliary atresia. Kupffer cells are involved in an extensive erythrophagocytosis, the storage of iron, and perhaps the incorporation of cellular components from hepatocytes. Lipocytes are the vitamin A-storing cells of the transforming liver and may be responsible for some perisinusoidal fibrosis. Granulomas are present during stages 3-6 and are focal areas where mononuclear leukocytes (lymphocytes and plasmalike cells), macrophages, and neutrophils have infiltrated the hepatic parenchyma. The function of the granulomas is not known; but their presence may be related to the porous nature of the sinusoidal wall, the tissue degeneration, and/or the physiological change (e.g., bile stasis) during biliary atresia.

Killing of preimplantation mouse embryos by main ingredients of cleansers AS and LAS

When main ingredients of cleansers, alcohol sulfate (AS) and linear alkylbenzene sulfonate (LAS), were applied to the dorsal skin of pregnant JCL:ICR mice during preimplantation period (days 0-2), significant numbers of embryos collected from the oviducts and uteri on day 3 showed severe deformity or remained at the morula stage. Most of abnormal embryos were fragmented or remained at the 1-8 cell stages, and they were either dead or dying. Even when these abnormal embryos were cultivated in the detergent-free medium, they were not recovered, while most growth-retarded embryos (morula) could grow and hatch with one or two days lag by the further in vitro cultivation. Similar results were observed with commercially obtained kitchen detergent and hair shampoo, although such embryocidal effects were not detected with natural soap and distilled water. Fertilized eggs may be specifically sensitive to synthetic detergents. Very low doses of X-rays also induced significant yields of abnormal embryos. Major difference between X-rays and detergents was that X-ray-induced abnormality appeared at the morula or blastocyst stage, while detergent-induced one did at the earlier stages.

Enhancement of methylmercury toxicity by L-cystine in cultured mouse blastocysts

Expanded mouse blastocysts incubated with 1 to 2 microM methylmercury (MeHg) in modified Eagle's basal medium (BME + AA), which contains amino acids, collapsed and degenerated within 24 h. In contrast, blastocysts incubated with the same concentration of MeHg in egg culture medium (ECM), which does not contain amino acids, survived and remained expanded as control embryos did. By systematically omitting each BME amino acid from BME + AA and adding each BME amino acid to egg culture medium, we determined that L-cystine (0.5 mM in BME + AA) was the component of BME + AA that was responsible for the enhancement of the toxicity of MeHg. The shortest incubation time during which the cystine-enhanced MeHg toxicity became irreversible was 2 h, and the addition of any of the neutral BME amino acids (except threonine) or non-BME neutral amino acids (alanine, glycine, or serine) during the 2 h incubation eliminated or reduced the cystine-enhanced MeHg toxicity. Basic amino acids (except histidine) were less effective in protecting embryos: Glutamine and lysine reduced the toxic effect only slightly, and arginine had no effect. DL-buthionine sulfoximine (7.5 mM), a specific inhibitor of glutathione, also reduced cystine-enhanced MeHg toxicity. It therefore appears that cystine enhances MeHg toxicity indirectly, at least in part, by stimulating the synthesis of cellular glutathione, which may in turn enhance MeHg transport. In the absence of cystine, 10 microM MeHg (2 h incubation) was necessary to cause the collapse and degeneration of all blastocysts treated.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of mouse trisomy 16 on expression of specific genes

We examined developmental changes in the relative activities of three different isozyme systems: aldolase, enolase and phosphoglycerate mutase, in tissues of fetal mice with trisomy 16 and of fetal euploid littermates. We wanted to determine whether morphological abnormalities such as reduced weight and size, which are generally observed in murine trisomy, are reflected at the molecular level. Following electrophoretic separation and subsequent measurement of relative activities of enolase isozymes in brain and phosphoglycerate mutase isozymes in heart, we found no significant differences between trisomy 16 fetuses and their euploid littermates. Synthesis of liver-specific aldolase was, however, delayed in trisomy 16 fetuses.

Approaches to defining the relationship of maternal and developmental toxicity

Maternal and developmental toxicities reported in the literature were examined in an attempt to define more clearly their relationship. Relationships were difficult to ascertain because maternal toxicity end points are not clearly defined, or even assessed, in every study. However, maternal toxicity accompanied by developmental toxicity is the most common outcome of in vivo testing. Approaches to define these associations have included assessment of acute maternal toxicity and teratogenicity; evaluation of maternal toxicity and its association to developmental toxicity in general, and to malformations, specifically; and examination of developmental variations, embryolethality, and altered growth. None has demonstrated an unequivocal relationship between specific maternal and developmental toxicities: Developmental disruption appears not to result unconditionally from maternal toxicity. Maternal "stress" appears to have some impact on development but resists further definition at this time. Variations in association may be due to the extent to which maternal homeostasis has been compromised. Several quantitative approaches to relating maternal toxicity and developmental toxicity in animal systems (ie, relative teratogenic index, adult/developmental toxicity ratio) may provide the most satisfactory means of evaluating developmental toxicity testing for assessment of hazard.

Prevention of polydactyly manifestation in Polydactyly Nagoya (Pdn) mice by administration of cytosine arabinoside during pregnancy

Male mice heterozygous for the dominant polydactyly gene Pdn (Polydactyly Nagoya) were crossed with normal or heterozygous females of the same strain. Pregnant females were treated with 5 mg/kg of cytosine arabinoside (Ara-C) on day 12 of gestation. The offspring were removed on day 18 of gestation and examined for external malformations, and the fore- and hindlimbs were examined by means of bone- and cartilage-stained cleared specimens. In +/+ x Pdn/+ matings, Pdn/+ fetuses, bearing preaxial polydactyly of the distal phalangeal type in the hindlimb and deformity of the 1st digit in the forelimb, were obtained in about 50% of the nontreated group. In treated fetuses, however, the incidence of polydactyly and deformity of the 1st digit decreased to 1.4 and 10.1%, respectively. Nontreated Pdn/Pdn fetuses exhibited preaxial polydactyly of the duplicated or triplicated metacarpal/metatarsal type both in the fore- and hindlimbs. In the treated Pdn/Pdn fetuses, the number of preaxial extra digits decreased in both limbs. Some hindlimbs of the treated Pdn/Pdn fetuses exhibited five metatarsals, normally. In the vitally stained specimens at 6 and 24 hours after injection of Ara-C, preaxial marginal necrotic zones (fMI) were observed in almost all of the treated embryos from +/+ x Pdn/+ matings. However, approximately half of the embryos did not exhibit fMI in the nontreated control group at the same stage. Those embryos deficient in fMI were regarded as Pdn/+. These findings indicated that a subteratogenic dose of Ara-C prevented the genetic expression of polydactyly in almost all Pdn/+ and some cases of Pdn/Pdn mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of prenatal X-irradiation on open-field behavior in rats: application of randomized fostering technique and mapping results

Sprague-Dawley (SD) rats were given X-irradiation (150 R) on Day 17 of gestation. After birth, all male pups were pooled once and then assigned randomly to irradiated mothers and control mothers. Offspring were administered an open-field test at about 7 weeks of age. The analysis was performed on the basis of two approaches: In the per subject approach, individual subject data (aggregation across Day 2 through Day 4) were treated as the basic unit of statistical analysis. In the per litter approach, double aggregation (aggregation across Day 2 through Day 4 for each subject and aggregation across subjects within each litter) was used. The per subject approach was slightly more sensitive as to the treatment effect, but it induced a reduction in the magnitude of eta squared. A principal component analysis was performed using eta squared together with those of several reference groups. Results were plotted on a map constructed from component scores. The characteristics of behavior in X-irradiated rats were very similar to those of the earlier stage of trials in terms of the location on the map. The postnatal maternal effect on open-field behavior was not serious and was adequately negligible in practice. A new fostering procedure was proposed and its advantages discussed.

Incidence of cleft lip and cleft palate in 39,696 Japanese babies born during 1983

To estimate the incidence of cleft lip and/or cleft palate among the Japanese, 39,696 Japanese babies born during the period from January 1, 1983 to December 31, 1983, were investigated. It was found that 65 babies (0.163%) had these abnormalities, and that the ratio of the birth of such babies was approximately one per 611 in the population. Of the 65 affected babies, 41.3% presented cleft lip (CL), 46.0% cleft lip and palate (CL/P), and 12.7% cleft palate (CP). These results suggest that the incidence of CL/P in the Japanese is higher than that observed among other races.

A recent survey of consanguineous marriages in Japan

A survey of consanguineous marriages in Japan was conducted on September 1 in 1983 through questionnaires. The total number of couples studied was 9,225 chosen from six widely different areas of Japan. The rates of first cousin marriages and of total consanguineous marriages for all areas are 1.6% and 3.9%, respectively. The mean inbreeding coefficient is 0.00134 for all areas of Japan. On the other hand, the rate of total consanguineous marriages was ten times higher in Fukue-Shi (7.9%) than in Asahikawa city area (0.78%). The rate of total consanguineous marriages is decreased with the marriage year in Japan, where the rate of first cousin marriages has changed remarkably.

Effects of methylmercury and mercuric chloride on preimplantation mouse embryos in vivo

This report compares the effects of methylmercuric chloride (MMC) and mercuric chloride (MC) on the development of mouse preimplantation embryos in vivo. Female mice were injected with a single intravenous dose of 0.5-20.0 mg Hg/kg MMC or 0.5-2.5 mg Hg/kg MC on day 0 of gestation. The embryos were recovered by flushing excised oviduct and uterus on day 3.5 of pregnancy, and were examined for abnormalities. In the groups treated with doses of 0.5 and 1.0 mg Hg/kg of both compounds, the rates of abnormal embryos were not significantly different from that in the control group. The 50% effective dose of MMC was twice as great as that of MC. With increasing dose, the difference became more obvious; the 80% effective doses differed by a factor of ten. The body weight of dams decreased in terms of the dose of mercury in MC-treated groups, but did not vary in MMC-treated groups. The sensitive developmental stage for mercury toxicities could not be determined clearly, although the high sensitivity was reported in the blastocyst stage in vitro. The embryos treated in vivo were less sensitive than those reported in vitro.

The DiGeorge anomaly as a developmental field defect

The DiGeorge "syndrome" is a characteristic malformation pattern involving craniofacial, cardiac, thymic, and parathyroid structures. Evidence is accumulating that the DiGeorge "syndrome" is actually not a syndrome, but a polytopic developmental field defect. We present evidence of causal heterogeneity of the DiGeorge anomaly. This heterogeneity will be discussed in the light of recent findings that indicate that the dysmorphogenetically reactive unit responsible for the phenotype of the DiGeorge anomaly is a population of cephalic neural crest cells.

Patterns of soleus muscle potentials to repetitive stimulation in young and aged rats

Muscle potentials were recorded in the soleus muscle of Wistar rats anesthetized with urethane or Nembutal. The time course of their changes induced by repetitive stimulation of sciatic nerves at 5 Hz for 10 min was compared for young and aged rats. When stimulation commenced, muscle potentials from young rats were somewhat facilitated, followed by slight depression below control values, and thereafter they were gradually potentiated. On the contrary, muscle potentials from aged rats were rapidly reduced, attaining plateau levels 2 min or so after the onset of repetitive stimulation at 5 Hz.

Errors of morphogenesis and inborn errors of immunity 20 years after the discovery of DiGeorge anomaly

The heuristic concept of "inborn errors of metabolism" was introduced more then 70 years ago and by analogy has prompted the more recent introduction of the term "inborn errors of immunity". It is now well recognized that many inborn errors of immunity can be considered inborn errors of metabolism. Typically, many forms of severe combined immunodeficiency result from adenosine deaminase deficiency, i.e., an inborn error of purine metabolism. On the other hand, errors of immunity are often associated with "errors of morphogenesis", resulting from an intrinsically abnormal developmental process (malformation), a secondary or extrinsic interference with originally normal development (disruption), or an abnormal organization of cells into tissues (dysplasia). Twenty years after the original description, the DiGeorge anomaly should be considered an inborn error of morphogenesis and immunity due either to disruption or less frequently to malformation. In other immunodeficiencies, such as ataxia telangiectasia, the morphologic and immunologic errors result from a dyshistogenesis, i.e., dysplasia. Also, true malformation syndromes, such as Down's syndrome, are consistently associated with immunodeficiency.