ABSTRACT A fragment of quail notochord (20 somite stage) was implanted into a host chick embryo (25-30 somite stage) just lateral to the thoracic somites or into the intersomitic space. Around the implanted notochord, aggregates of rib-forming sclerotomal cells formed a large irregular mass of cartilage, resulting in segmental rib defects without any adverse effect on body wall muscle formation. This contrasted sharply with previous experimental studies in which abnormalities of other somite derivatives, in particular body wall muscles, were always associated with rib defects created by teratogenic agents, surgical treatment or by genetic means. These results suggest that migration of myogenic cells into the thoracic wall does not require the guidance of rib-forming sclerotomal cells or their products. Moreover, those myogenic cells can develop into three layers of thoracic wall muscles, independent of skeletal pattern formation.
ABSTRACT This study was designed to determine precisely the radiosensitive period in the development of ICR mouse embryos during which external malformations and growth retardation tend to occur. Female and male mice were placed together for only three hours to allow fairly precise identification of the time of conception. The pregnant mice were divided into 31 groups, which were irradiated in turn with 1.5 Gy gamma radiation at 6-hour intervals during the period of organogenesis. They were then observed on day 18 of gestation. Items recorded were intrauterine death, external malformations, sex ratio and fetal body weight. Death of the embryo/fetus, especially death in the early period of organogenesis, was most frequent in mice irradiated between days 6.75 and 8.25 of gestation, but there was no statistically significant difference in the frequency of early- and late-period deaths between irradiated and control groups. The types and frequencies of external malformations observed differed according to the exposure period. The most highly sensitive period for each malformation lasted no more than 12 hours. Reduction of fetal body weight was a good indicator of radiation effects, and was observed mostly in the groups irradiated between days 9.75 and 11.00 of gestation. The sex ratio was not affected by the period in which irradiation was performed.
ABSTRACT We report a patient with a lethal multiple pterygium syndrome. The patient was the first child born to a 28-year old mother. The family history was unremarkable; no consanguinity was reported. The patient was the product of a 37-week gestation by cesarian section, and admitted to our intensive care unit after resuscitation. He weighed 2,158 g, and measured 33cm (CHL). The patient had hydrops, cystic hygroma on the back of the neck, hypertelorism, a flat upturned nose, a highly arched cleft palate, micrognathia, low set ears and multiple pterygia. In addition, the finger showed slender and hypoplastic ridges and creases. The feet showed rocker-bottom deformities. Furthermore, the genitalia was normally formed male with bilateral cryptorchism. The spine showed scoliosis and lordosis with vertebral bony fusions, separations and reduced intervertebral spaces. The ribs were 11 pairs and gracile. The lung was hypoplastic, and the heart was small but normal in structure. Chromosomal examination revealed a normal male karyotype (46, XU). The infant died within two hours after birth. Gillin and Pryse-Davis (1976) described three female siblings with this early lethal disorder. This disorder was separated from other conditions associated with pterygia by Hall et al. (1982). At least 30 cases have been reported. However, this type of case seems to have not been reported in Japan. This disorder is considered autosomal-recessive, but in other report, X-linked recessive inheritance is proposed. Therefore, further studies are necessary in order to make a more precise etiology of this disorder.
ABSTRACT The pathogenesis of anorectal malformations has been discussed for more than 100 years, however, much remains to be elucidated. We studied the pathogenesis of high- type anorectal malformations induced by all-trans retinoic acid (all-trans RA) in mice. Pregnant females were injected intraperitoneally once with all-trans RA, suspended in corn oil (5 mg/ml), at a dose of 100 mgkg on day 9 of pregnancy. The all-trans RA-treated females were killed on one of days 10 to 18 of pregnancy. All fetuses examined on day 18 of pregnancy following in utero exposure to all-trans RA had anorectal malformations. In the affected male fetuses, the rectum was positioned away from the retroperitoneum toward the ventral side leading to the opening of the urethra just underneath the urinary bladder. Deficiency of the cloacal plate at the dorsal part was also observed in the affected embryos during days 10-1 1 of pregnancy. The cloacal plate is considered to bring the cloacal cavity to the anus, and thus the deficiency of the dorsal part may be the major cause of the high- type anorectal malformations.
ABSTRACT Cocaine (1 2.5 or 25 mgkg) was administered intraperitoneally to pregnant rats 15 min to 12 hr prior to Caesarean section on day 20 of gestation. The fetuses were immediately frozen and serially sectioned, and the diameter of their ductus arteriosus (DA) was calibrated. The DA was patent in all the fetuses examined and the DA caliber was not significantly different between the control and the cocaine-treated groups at any time interval after the cocaine dosing. It was concluded that cocaine has no constrictive effects on the fetal DA in the rat.
ABSTRACT The sensitive period and the dose-response characteristics for dexametha- sone-induced cleft palate and palatal slit in rats were examined. Pregnant rats were injected subcutaneously with dexamethasone in a single dose of 2-6 mgkg on one day between day 8 and 16 of the gestational period or once each day for two successive days (days 14 and 15 of gestation). All animals were euthanized on day 20 of gestation and the palatal condition of their fetuses was inspected after fixation under a dissecting micro- scope. The sensitive stage of palatal slit and cleft palate induction was determined and the dose-response relationship was analyzed by the loprobit transformation method. No maternal lethality was elicited in any of the treatment groups. High frequencies of palatal slit and cleft palate were induced when dexamethasone was administered as a single dose on any individual day from day 12 to day 14 of gestation. Omphalocele and general edema were also found to be significantly more frequent in the high-dose group treated on days 12-14 of gestation. All groups treated showed a reduction in fetal body weight. The response data for palatal slit and cleft palate after administration of dexamethasone fitted to similar linear regression slopes, suggesting a similarity in the underlying mechanisms for palatal slit and cleft palate induction in rats. ED50 values were 3.48 mgkg for palatal slit and 6.64 mgkg for cleft palate. These findings indicate that dexamethasone treatment is effective in inducing palatal slit and cleft palate in rats, as well as in mice.
ABSTRACT We have examined eleven cases of holoprosencephaly with special emphasis on the frontal proboscis. Although the nostril appears blind ended grossly, the proboscis has a single slender midline nostril lined with squamous mucosa containing numerous sebaceous glands. It is actually connected to a poorly formed but definite nasal cavity microscopically. The inner portion of the nostril tunnel is lined by olfactory mucosa containing numerous subjacent secretory glands. Despite the absence of olfactory bulbs and tracts the cartilaginous nasal capsule is identified along with abnormal nasal cavity. How- ever, the nasal capsule is hypoplastic, and has an aberrant nasal septum and no concha. In severe form of holoprosencephaly, i.e., cyclopia, the nasal capsule is noted above the level of the ethmoid plate, in which case the nasal cavity dose not communicate with nasopharynx because it is too distant from the hypoplastic maxilla. Therefore, choanal atresia is resulted. Although unique maxillary bone comprises the whole upper jaw, the failure of fusion between vomeronasal septum and palatal processes in holoprosencephaly results in abnormal maxillary bone which is characterized by a narrow palate without palatal arch form. Nevertheless, through serial microscopic sections we could find a space between the posterior maxilla and the sphenoid bone, which is composed of adipose tissue and is similar in shape to the nasal capsule. This space is thought to be made for the nasal capsule during early developmental period. The present study suggests that the frontal proboscis in holoprosencephaly is an undescended nose. In most cases it is connected to the aberrant nasal cavity which is located beneath the proboscis. The level of proboscis descends gradually toward normal nose position as the severity of holoprosencephaly de- creased from cyclopia, ethmocephaly, cebocephaly, to premaxillary agenesis.
ABSTRACT The internal structures of rat fetuses on day 18.0 of pregnancy were studied by magnetic resonance imaging in 1-mm sagittal slices. Each organ was represented as white to gray images different in tone according to the 'H proton content and the relaxation time. In solid organs, portions with high cell density were seen as white areas and those with low cell density as gray areas. In the tubular organs, the margins were imaged as white and the lumina as gray.