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Digital anomalies of mouse limbs induced by treatment with urethan in vitro.

The effects of urethan on ICR/JCL mouse limbs were examined in forelimbs of day-11 embryos cultured in concentrations of 0, 50, and 100 mug/ml for one to four days, and in forelimbs of day-12 embryos and in fore- and hind limbs of day-13 embryos in 0, 10, 50, and 100 mug/ml for one to four days. Urethan did not cause digital malformations on day-11 limbs but induced syndactyly in day-12 forelimbs and polydactyly in day-12 forelimbs and day-13-fore- and hind limbs. The polydactyly may have been due to effects on mesenchymal cells producing localized cell proliferation, whereas syndactyly may have been due to effects on precartilage cells, resulting in excess migration of mesenchymal cells toward the digits, leaving the connective tissue at the interdigital space to develop inadequately.

Abnormalities, Drug-Induced↗

Patterns of combined limb malformations.

Seven different limb malformations types were defined in 544 affected newborns, apparently free from other anomalies, obtained from a series of 297,299 livebirths. These seven malformation types were: polydactyly, limb reduction, brachydactyly, symphalangy, syndactyly and split hand/foot. One anomaly type was present in 472 newborns (1.58/1,000) and two or three in 72 (0.24/1,000). The observed combinations of two or three limb malformation types cannot be explained as chance association. Therefore, a common etiopathogenic mechanism has to be considered when two or more limb malformation types are combined in a given individual. The most frequent observed combinations were: reduction-brachydactyly, reduction-syndactyly, brachydactyly-syndactyly, polydactyly-syndactyly, and reduction-brachydactyly-syndactyly. Based on affected limb distribution, sex ratio, and familial recurrence rates, it is suggest that a reduction anomaly is the primary component in all tested combinations while syndactyly tends to be a secondary one when combined with any other limb anomaly type.

Abnormalities, Multiple↗

Limb development in mouse embryos. II. Reduction defects, cytotoxicity and inhibition of DNA synthesis produced by cytosine arabinoside.

Various morphological and biochemical parameters were used to study the mode of interference by cytosine arabinoside (Ara-C) in critical phases of embryonic limb development. Inhibition of embryonic DNA synthesis occurred immediately after injection of Ara-C into the mother. The inhibition was dose-dependent and was substantial even after the nonteratogenic dose (2 mg/kg) of Arc-C. The pattern of limb bone deficiencies in Ara-C treated fetuses was specific for each developmental stage at which the treatment was given; the site of affect moved distalwards along the limb as the development advanced. The teratogenic dose was cytotoxic to mesenchymal cells with a high proliferation rate but did not affect others such as the future cartilage cells in which the rate of proliferation was lower. The existence of this differential susceptibility at each stage of development, together with information about the pattern of bone defects at the same stage, permitted us not only to define with some precision the cellular basis of origin of limb defects but also to infer the relative level of cell differentiation pertaining to each successive stage. Deoxycytidine, if injected simultaneously with and at doses eight times larger than Ara-C, afforded virtually complete protection against teratogenic effects. Deoxycytidine also prevented cell death in the limbs of Ara-C treated embryos. However, a dramatic increase in the frequency of polydactyly was found in the protected fetuses. The fact that the frequency of ectrodactyly in the protected fetuses decreased in inverse proportion to the frequency of polydactyly strengthened the notion that there may be a common cellular basis underlying these two types of digital defects. Striking changes were found in the structure of AER at 24 hours after Ara-C treatment; it was abnormally thickened into a gland-like structure and its inner edge facing the mesenchyme thickened into a gland-like structure and its inner edge facing the mesenchyme was thrown into several folds. This may constitute a response to impairment in the underlying mesenchyme with which AFR has long been considered to have an interdependent relationship.

Animals↗

Teratogenic effect of N-methyl-N'-nitro-N-nitrosoguanidine in mice.

The teratogenic effect on the mouse fetus of a potently mutagenic and carcinogenic agent, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), was studied. Pregnant mice were injected on one of gestation days 7-12 with an intraperitoneal dose of 40, 60 or 80 mg/kg of MNNG, and fetuses were examined on day 18 of gestation. Various malformations affecting the brain, face, vertebra, rib and limb appeared in high frequency. Brain malformations were the most predominant; hydrocephalus, hydromicrocephaly and microcephaly appeared in sequence with developmental stages of treatment, although exencephaly occurred infrequently. Cleft palate, sometimes associated with microglossia and micrognathia, and vertebral anomalies including tail defect were observed following almost every gestation-day treatment. Long-bone defects of fore- and hindlimbs were also predominant. Polydactyly, ectrodactyly and microdactyly frequently occurred together in the fore- or hindlimbs or both in sequence with treatment stages. Ectrodactyly and microdactyly appeared with greater frequency on the left than on the right in both fore- and hindlimbs, but polydactyly and long-bone defects appeared bilaterally.

Abnormalities, Drug-Induced↗

Threatened abortion, hormone therapy and malformed embryos.

Causal relations between maternal genital bleeding, supportive hormone therapy and external malformations of the embryos were investigated with special reference to the critical period of organogenesis. This was done using morphological and obstetrical data obtained by Nishimura and his associates from 667 undamaged embryos derived from induced abortions whose mothers had genital bleeding in early pregnancy. In addition, data from 90 embryos with polydactyly and 38 with limb reductions in the Nishimura collection were used for case history studies. Evidence was presented to demonstrate that, for major malformations such as CNS anomalies, cleft lip, polydactyly and limb reductions, maternal genital bleeding was not a cause but a consequence of the conception of an abnormal embryo. No indication was revealed that exogenous female hormones currently used in Japan for preventing miscarraiges could produce major malformations recognizable at the embryonic stage, including limb reductions, nor salvage the severely malformed embryos. This does not however mean to exclude the possible relationship of progestogens/estrogens intake during early pregnancy with an increased incidence at birth of certain internal and/or external malformations. It was suggested that most, if not all, of the minor anomalies observed at certain embryonic stages are kinds of normal variants without any functional impairment of embryonic development.

Abnormalities, Drug-Induced↗

Review of drug-induced limb defects in mammals.

The objective of this paper was to illustrate the spectrum of possible limb malformations in mammals resulting from drug exposure. A bibliography of 171 papers from 20 journals was generated from which pertinent data (drug used, limb defects reported, predominant defect location) were tabulated. These data should provide a basis for predictions about types of defects that might be expected in further studies and for judging postulated drug-induced human limb defects. However, direct extrapolation to humans is inappropriate. The following trends were observed: 1) Distal limb defects (autopod) are almost twice as common as proximal limb defects (stylopod and zygopod). 2) Ectrodactyly is the single most common type of limb defect, accounting for over half of the autopod defects. 3) Ectrodactyly is almost twice as common in the hindlimb as in the forelimb. 4) Postaxial ectrodactyly is over twice as common as preaxial ectrodactyly in the forelimb, but preaxial ectrodactyly is four times more common in the hindlimbs. 5) Polydactyly occurs with approximately equal frequency in forelimbs and hindlimbs, and preaxial polydactyly is most common in both fore and hindlimbs. 6) Polymelia (supernumerary limbs) occurred in one case, and may have been a spurious result. 7) Either transverse hemimelia is greatly underreported in teratology studies or it essentially does not occur. We have concluded that, at least in some cases, acetazolamide, adenine, 1,7-dimethylxanthine, and xanthine derivative aminophylline, retinoic acid, acetoxy-methyl-methylnitrosamine, aspirin, and cadmium can all cause unilateral defects.

Abnormalities, Drug-Induced↗

Paired-related homeobox genes cooperate in handplate and hindlimb zeugopod morphogenesis.

The closely related homeobox genes prx-1 and prx-2 are expressed in lateral plate and limb bud mesoderm, but targeted inactivation of these genes failed to demonstrate a limb phenotype. Here we report that mice carrying compound mutations in prx-1 and prx-2 have severe limb deformities. In the forelimb autopod, pre- and postaxial polydactyly were found most commonly, but also syndactyly, oligodactyly, and abnormal digit placement affecting posterior elements were observed. In the hindlimb, preaxial polydactyly with variable expressivity was seen in all cases. Extreme distal digit duplications were seen in both the fore- and hindlimbs. prx-1; prx-2 double-mutant mice also displayed extreme shortening and impaired ossification of the hindlimb zeugopods. Integrity of the forelimb apical ectodermal ridge was abnormal as determined by expression of FGF8 and BMP4. Expression of msx-1 and msx-2, markers for BMP signaling pathways, was absent in regions of the posterior handplates, while expression of Shh and patched was unaffected. The mutant phenotypes were dosage dependent, since prx-1 -/-; prx-2 +/- mice also displayed severe limb abnormalities. These data suggest that prx-1 and prx-2 cooperatively regulate handplate and hindlimb zeugopod morphogenesis through BMP-mediated signaling pathways.

Animals↗

Teratogenic interactions between methylmercury and mitomycin-C in mice.

Pregnant mice were given p.o. various nonteratogenic doses (0, 2.5, 5 and 10 mg/kg) of methylmercuric chloride on day 9 of pregnancy, and then injected i.p. with a teratogenic dose (4 mg/kg) of mitomycin-C on day 10. Major malformations produced by mitomycin-C alone were cervical rib and vertebral anomaly, polydactyly of the hindlimb and tail anomaly. Combined treatment significantly increased the incidence of these malformations, showing the dose-effect relationship of methylmercury, whereas methylmercury alone is known not to produce such malformations. When mitomycin-C treatment alone was performed on day 9.5 of pregnancy, only vertebral anomalies increased in incidence. Therefore, mitomycin-C teratogenicity in terms of the manifestation of cervical rib, polydactyly and tail anomaly, but not vertebral anomaly, was suggested to be enhanced by methylmercury. A considerable number of foetuses showed cleft palate involvement following combined treatments, but not by either chemical alone. Cleft palate is known to be a major malformation in mice that is caused by methylmercury, and mitomycin-C also induces cleft palate. Therefore, the two chemicals might have affected foetuses additively and thereby induced cleft palate.

Abnormalities, Drug-Induced↗

The acrocallosal syndrome.

The acrocallosal syndrome is characterized by peculiar facies, polydactyly of the hands and/or feet, and agenesis of the corpus callosum. Two unrelated 4-month-old boys with consanguineous parents are reported. Both exhibited the main features of the syndrome, but neither of them had partial reduplication of halluces. Consequently, pre-axial polydactyly of the feet is not considered to be a constant feature of the acrocallosal syndrome. The similarity of the acrocallosal syndrome to Greig syndrome is discussed, but it appears unlikely that the two syndromes are identical. Consanguinity in both cases is a strong argument in favour of a recessive mode of inheritance.

Agenesis of Corpus Callosum↗

The Smith-Lemli-Opitz syndrome. A detailed pathological study as a clue to a etiological heterogeneity.

An analysis of 33 autopsied cases with the Smith-Lemli-Opitz syndrome (including 8 cases from our practice) is presented. Polydactyly in dead SLOS children was found in 51% (17/33) of cases and occurred significantly more often in this group than in the whole group of SLOS (20-22%). Certain morphological differences in the type of renal, cerebral, pulmonary and pancreatic anomalies indicate the existence of two phenotypically similar SLOS: 1) with polydactyly; 2) without it. The presented data initiate SLOS heterogeneity.

Abnormalities, Multiple↗

Roentgenologic features of the Meckel syndrome.

The Meckel syndrome is an autosomal recessive lethal malformation syndrome. The main features are multicystic dysplastic kidneys, microcephaly with occipital encephalocele and polydactyly. This paper describes 6 new cases, with special reference to skeletal findings in postmortem total body radiographs. Microcephaly with an occipital bone defect and encephalocele or hydrocephaly [1/6], short upper extremities, bell-shaped thorax with abdominal distension and postaxial polydactyly in the hands and feet were constant findings in these cases.

Abnormalities, Multiple↗

Coronal and sagittal clefts in skeletal dysplasias.

Objective. To assess the role of coronal and sagittal vertebral clefts in diagnosing skeletal dysplasias. Material and Methods. A search in the database at the International Skeletal Dysplasia Registry revealed 40 different diagnoses in which coronal or sagittal clefts were present, the major groups being: atelosteogenesis, chondrodysplasia punctata, dyssegmental dysplasia, Kniest dysplasia and short rib polydactyly syndrome. We reviewed all firm cases with both AP and lateral films of the spine in these major groups (n = 143), with patients' ages ranging from 20 weeks of gestation up to 26 years of age. Results. Ninety-four percent of all clefts were found in children less than 1 year of age, mainly located in the thoracolumbar region. Fifty-six percent of the clefts were observed in boys. Coronal clefts were more common than sagittal clefts. Clefts were most frequently observed in atelosteogenesis (88%), followed by chondrodysplasia punctata (79%), dyssegmental dysplasia (73%), Kniest dysplasia (63%) and short rib polydactyly syndrome (53%). Conclusion. Vertebral clefts are of major diagnostic value in the groups mentioned above, especially before 1 year of age. The search did not come up with new entities in which vertebral clefts are of major diagnostic value.

Adolescent↗

Skeletal abnormalities of hands and feet in Laurence-Moon-Bardet-Biedl (LMBB) syndrome: a radiographic study.

OBJECTIVE: To identify radiological changes of the hands and feet in a large group of patients with Laurence-Moon-Bardet-Biedl syndrome. DESIGN: Postero-anterior views of hands and feet were obtained and analysed. PATIENTS: The material consists of 43 Scandinavian patients with the syndrome (24 males and 19 females; age 3 weeks to 57 years, median 23 years at the time of radiological examination). RESULTS AND CONCLUSIONS: Polydactyly of the hands and feet is one of the main criteria. This was noted clinically in 33 of 43 patients, but all but 3 had been operated on before this radiological study. Remnants of the extirpated finger or toe noted as exostoses, additional joint surfaces of duplication were found in half the hands and feet, while the remainder showed no radiological changes. Other features found were short, broad bones and flat joint surfaces of the metacarpophalangeal or metatarsophalangeal joints. We also found a high frequency of short or long ulna in relation to the radius and Madelung deformity of the wrist in several patients. Thus, the radiographs showed several non-specific normal variations besides remnants or postoperative changes after polydactyly.

Adolescent↗

A novel locus for Meckel-Gruber syndrome, MKS3, maps to chromosome 8q24.

Meckel-Gruber syndrome (MKS), the most common monogenic cause of neural tube defects, is an autosomal recessive disorder characterised by a combination of renal cysts and variably associated features, including developmental anomalies of the central nervous system (typically encephalcoele), hepatic ductal dysplasia and cysts, and polydactyly. Locus heterogeneity has been demonstrated by the mapping of the MKS1locus to 17q21-24 in Finnish kindreds, and of MKS2 to 11q13 in North African-Middle Eastern cohorts. In the present study, we have investigated the genetic basis of MKS in eight consanguineous kindreds, originating from the Indian sub-continent, that do not show linkage to either MKS1 or MKS2. We report the localisation of a third MKS locus ( MKS3) to chromosome 8q24 in this cohort by a genome-wide linkage search using autozygosity mapping. We identified a 26-cM region of autozygosity between D8S586 and D8S1108 with a maximum cumulative two-point LOD score at D8S1179 ( Z(max)=3.04 at theta=0.06). A heterogeneity test provided evidence of one unlinked family. Exclusion of this family from multipoint analysis maximised the cumulative multipoint LOD score at locus D8S1128 ( Z(max)=5.65). Furthermore, a heterozygous SNP in DDEF1, a putative candidate gene, suggested that MKS3 mapped within a 15-cM interval. Comparison of the clinical features of MKS3-linked cases with reports of MKS1- and MKS2-linked kindreds suggests that polydactyly (and possibly encephalocele) appear less common in MKS3-linked families.

Abnormalities, Multiple↗

Apoptotic degeneration in the arhinencephalic brain of the mouse mutant Pdn/Pdn.

The homozygotes of a mouse strain with genetic polydactyly (Polydactyly Nagoya, Pdn) exhibit arhinencephaly and various brain malformations. In the present experiment, abnormal apoptotic degeneration in the arhinencephalic brain of Pdn/Pdn embryos and newborns was investigated immunohistochemically and by molecular genetic techniques. Polyclonal antibody against single-stranded DNA detected the nuclei of programmed dying cells (apoptotic cells) specifically in the interdigital necrotic zone of the normal mouse limb plate on day 14 of gestation. We used this antibody against single-stranded DNA to investigate the apoptotic degeneration in Pdn/Pdn brain. Abnormal apoptosis was observed in the infralimbic cortical plate, hypothalamus and periventricular thalamus on day 0 after birth in Pdn/Pdn brains. The TRPM-2 gene, which has been considered to mediate apoptosis, was expressed in the developing normal and Pdn/Pdn brains. TRPM-2 gene expressions in the brain stem and cerebellum of arhinencephalic Pdn/Pdn fetuses and newborns were higher than those of +/+ littermates. From these facts, it was suggested that the abnormal apoptosis caused a large amount of cell loss in the arhinencephalic mouse brain, and this cell loss induced the expansion of the ventricle, followed by the hydrocephaly.

Animals↗

Cerebral malformations in Carpenter syndrome.

The inherited forms of craniosynostosis can be divided into 4 groups: isolated craniosynostosis, craniosynostosis with syndactyly, craniosynostosis with polydactyly and syndactyly, and craniosynostosis with other somatic abnormalities. Acrocephalopolysyndactyly or Carpenter syndrome consists of craniosynostosis, short fingers, soft tissue syndactyly, preaxial polydactyly, congenital heart disease, hypogenitalism, obesity, and umbilical hernia. As many as three-fourths of the patients have some degree of intellectual impairment. The etiology of mental retardation in this syndrome has not been explored. A patient is reported with the features of Carpenter syndrome who has profound developmental delay and cerebral malformations demonstrated by magnetic resonance imaging and computed tomography. Because mental retardation is not an invariable feature of this syndrome or other craniosynostosis syndromes, neuroradiologic examination may help in predicting the intellectual outcome in these patients.

Acrocephalosyndactylia↗

Characteristics of the limb malformations induced by maternal exposure to cadmium in the mouse.

Single doses of 2,3,4,6,8,10, and 15 mg/kg of cadmium chloride were administered (SC) to groups of MF1 mice on one of days 7 to 12 of gestation. Fetuses collected on day 18 were observed for limb malformations, and alizarin red-S stained skeletons were examined for their skeletal bases. Ectrodactyly, postaxial polydactyly, syndactyly, brachydactyly, adactyly, phocomelia, meromelia, and malrotation of the limbs were detected in a significant number of fetuses. Days 7 to 10 were greatly susceptible for induction of these malformations. Postaxial ectrodactyly was more frequent in the forepaws, and sidedness was not significant. Preaxial ectrodactyly preferentially affected the left hindpaws in the 9th-day treatment group. Postaxial polydactyly was predominently right sided and mostly involved the forepaws. Day 8 was particularly susceptible for induction of adactyly. Malrotation of the limbs together with edema and caudal narrowing resulted in a 'penguin-like' appearance. Ossification of the long bones, the carpals, tarsals, and phalanges were affected. Even those limbs that were not externally malformed had skeletal dysgenesis. Limb buds examined histologically at midgestation showed scanty and poorly organized mesenchyme, extensive elaboration of marginal sinsus, reduced thickness of the apical ectodermal ridge (AER), and discontinuous basement membrane. It is speculated that such histologic alterations at early stages of development could have contributed to the defective morphogenesis of limbs in this animal model.

Abnormalities, Drug-Induced↗

Role of maternal dietary antioxidant supplementation in murine placental and fetal limb development.

Methylnitrosourea (MNU) is a multisystem teratogen that damages proliferating cells through macromolecule alkylation and generation of reactive oxygen species (ROS). Murine dams exposed to MNU midgestation produce offspring with distal limb malformations, an outcome reduced by maternal immune stimulation. Immunostimulatory effects of antioxidant therapy may in part explain this improved birth outcome. The present study hypothesizes that placental, rather than fetal, damage from excessive ROS may contribute to MNU-induced embryopathy. Fetal limbs and placentas were examined in immunotolerant CD-1 and immunosensitive C57BL/6N mice exposed to MNU, dietary antioxidant butylated hydroxytoluene (BHT), or both. MNU increased fetal resorptions and incidence of syndactyly, oligodactyly, polydactyly, and interdigital webbing, and decreased fetal size in both mouse strains. BHT reduced syndactyly and oligodactyly in both strains, and reduced polydactyly in C57BL/6N mice. Increased webbing in MNU and MNU+BHT groups likely represented maturational delay. Placentas from CD-1 and C57BL/6N MNU-exposed dams demonstrated decreased trophoblasts and increased necrosis of endothelium. Similar to distal limb defects, placental damage was reduced in mice receiving MNU+BHT. These results suggest that placental damage and fetal defects caused by MNU are in part ROS-mediated, and reduced distal limb defects following MNU+BHT may be related to improved placental integrity and function.

Alkylating Agents↗