bluuebunny/crossref_metadata_2025_split huggingface dataset:
Amelioration by leucovorin of methotrexate developmental toxicity in rabbits
Authors: DeSesso John M. , Goeringer Gerald C. 
Published: June 2005

AbstractMethotrexate (MTX) is lethal or teratogenic to embryos of all species tested. New Zealand white rabbit embryos are relatively resistant to the embryolethal effects of MTX. However, when pregnant does were injected iv with 19.2 mg MTX/kg on gestational day 12, virtually all surviving fetuses exhibited multiple malformations of the head, limbs, and trunk. MTX is a structural analogue of folic acid that competitively inhibits dihydrofolate reductase, thereby preventing formation of folinic acid and essentially stopping one carbon metabolism. One carbon metabolism is important in the synthesis of methionine, histidine, glycine, and purine bases that are required for the de novo synthesis of DNA. Presumably these metabolic effects of MTX relate directly to its mechanism of developmental toxicity. An ameliorative treatment has been tested utilizing iv injection of pregnant rabbits with leucovorin (LV), a close structural analogue of folinic acid (the product of the inhibited enzyme), at various times after MTX exposure. When LV was injected at times up to 24 hours after MTX, fewer malformed fetuses resulted and the incidence of specific malformations was reduced. When given at times up to 20 hours after MTX administration, LV virtually eliminated the grossly apparent effects of MTX at term. In the forelimb bud, MTX increased the extracellular space surrounding limb bud mesenchymal cells within 8–10 hours; this process continued through 16 hours and remained unabated by 24 hours. Mesenchymal cell nuclei became hyperchromatic and pyknotic during this time period. By 24 hours, a moderate amount of cellular debris was observed in the mesenchymal compartment of limb buds from approximately one‐third of the embryos examined. Endothelial cell nuclei of the limb bud vasculature did not exhibit the histopathological alterations observed in the mesenchymal cells. Limb buds from embryos injected with LV at times up to 6 hours after MTX were histologically normal. When LV treatment was delayed until 16 or 20 hours after MTX, mesenchymal nuclei regained normal appearance within 2 hours of treatment; further, the abnormally large intercellular space began to decrease during the next 4 hours. Cellular debris was not a prominent feature of limb buds from LV‐treated embryos examined at any time. Embryos from rabbits injected with LV at 24 hours after MTX exhibited either typical MTX‐induced lesions or a sequence of reparative events similar to those described for the 16 and 20 hour LV‐treated embryos. These results demonstrate that LV, administered up to 24 hours after MTX, is able to ameliorate the developmentally toxic effects of MTX seen in rabbits at term. Histological examination revealed that LV is able to reverse the early sequelae of MTX exposure in limb bud mesenchymal tissue.
Effects of prenatal exposure to methylazoxymethanol (MAM) on brain weight, hypothalamic cell number, pituitary structure, and postnatal growth in the rat
Authors: Rodier Patricia M. , Kates Barbara , White Wendy A. , Muhs Ann 
Published: June 2005

AbstractCongenital brain damage syndromes typically are described in terms of behavioral symptoms. Many brain functions are not reflected in behavior, however, and prenatal injury to the developing nervous system could alter these functions, as well. To test the hypothesis that prenatal brain injury can result in postnatal endocrine malfunction, rats were exposed in utero to 20 mg/kg of methylazoxymethanol acetate, a potent neuroteratogen, at two stages of gestation when different sets of growth‐controlling neurons of the hypothalamus are forming. The growth hormone releasing factor (GRF) neurons stimulate release of growth hormone from the somatotropes of the anterior pituitary, contributing to rapid growth in the period between weaning and puberty. The somatotropin release inhibiting factor (SRIF) neurons have the opposite effect on the pituitary and can inhibit the GRF cells directly. Growth of treated animals was monitored daily from birth to 40 days and compared to that of controls Treatment on the 14th day of gestation produced a small number of dwarf animals characterized by normal weight at birth and a sudden decrease in growth rate at the beginning of the fourth postnatal week that led to a body weight about 50% of normal. Treatment on day 16 yielded an acceleration of postnatal growth (significant in males). In each group, most treated animals were like controls in adult size and pattern of growth. As adults, both treatment groups demonstrated massive reductions in brain weight which characterized all the subjects, whether or not they exhibited growth anomalies. The animals treated on day 14 were confirmed to have a significant, selective reduction in growth hormone releasing factor neurons. Reductions were greatest in the middle and posterior levels of the GRF cell distribution, the regions forming most actively at the time of exposure. Unexpectedly, the same group also had increased numbers of periventricular SRIF neurons. Neither type of neurons was significantly altered in the later treatment group. Examination of pituitary structure indicated that dwarfs had very small pituitaries, with an immature pattern of somatotrope distribution, and giants had very large pituitaries, with some hypertrophy of somatotropes. The results suggest that endocrine anomalies which manifest themselves long after birth may originate as birth defects of the nervous system.
Effects of magnetic resonance imaging on eye development in the C57BL/6J mouse
Authors: Tyndall Donald A. , Sulik Kathleen K. 
Published: June 2005

AbstractAn investigation was undertaken to ascertain the potential teratogenicity of magnetic resonance imaging (MRI) fields. The C57BL/6J mouse was chosen as the experimental model with eye malformations (microphthalmia and morphologic anomalies) designated as the biological end point. This mouse strain is genetically predisposed to this type of malformation as a 10% spontaneous incidence occurs. Dams in groups of 15 were subjected to MRI imaging conditions on gestational day (Gd) 7 for 36 minutes to a spin‐echo T‐2‐weighted scan by using a 1.5 Tesla magnetic field and a radiofrequency (RF) field of 64 MHz. One group was exposed at the magnetic isocenter while another was exposed at the entrance to the magnet lumen. There was also a sham control group. The dams were sacrificed at Gd 14. Assessment of eye abnormality was determined by, (1) a veterinary ophthalmologist, (2) a computer‐based method comparing eye areas, and (3) a methodology combining both the above subjective and quantitative methods. MRI fields were found to produce malformation rates (15–37%) higher than controls (2–19% P⩽.05, Kruskal‐Wallis Test) for both isocenter and lumen entrance groups. The malformation rates and degree of statistical significance varied somewhat with analytical methodology and the unit of measure (right eye, left eye, or fetus). The results suggest for the first time the potential of MRI fields to produce developmental malformations in an animal model utilizing clinically realistic exposure conditions. (However, the reader is reminded that the mouse strain utilized in this investigation was genetically prone to malformations.)
Explaining certain human limb anomalies and the limb—hematopoiesis community of syndromes using a model of determination
Authors: Lubinsky Mark S. 
Published: June 2005

AbstractDisturbances of determination, the process of limitation of developmental potential, can cause structural as well as histologic anomalies. A polar coordinate model (PCM) developed from studies in animals, in which determination depends upon positional information arranged along polar coordinates, can be used to explain certain classes of human limb anomalies. Under the model, interference with this system primarily affects distal patterning. If the radial area is distal to the zone of polarizing activity in embryological development, as it appears to be, the PCM explains the teratologic equivalence of preaxial duplications and deficiencies in certain circumstances and the prevalence of ulnar dimelias in forearm duplications. Also, failures of hematopoiesis can be considered late problems with determination and may be markers for abnormalities of a determinative process that also has earlier developmental consequences. Abnormalities of retinoic acid morphogen receptors would be one possible mechanism. This would provide a rationale for the known association of postnatal hematologic problems with developmental anomalies preferentially affecting the radial area. Syndromes with limb and hematopoietic problems may well be a community of determinative disorders.
Lethal and teratogenic effects of long‐term low‐intensity radio frequency radiation at 428 MHz on developing chick embryo
Authors: Saito Kenichi , Suzuki Katsushi , Motoyoshi Shigekatsu 
Published: June 2005

AbstractExposure of developing chick embryos to 428 MHz radio frequency (RF) radiation at a power density of 5.5 mW/cm2 for more than 20 days resulted in embryolethal and/or teratogenic effects and delayed hatching. These adverse biological effects were not due to any thermal effect of the RF radiation. We have demonstrated teratogenicity in the chick embryo as a result of protracted low‐dose RF irradiation.
Developmental regulation for collagen II gene expression in transgenic mice
Authors: Bruggeman Leslie A. , Hou‐Xiang Xie , Brown Kenneth S. , Yamada Yoshihiko 
Published: June 2005

AbstractIn order to evaluate the involvement of the type II collagen regulatory sequences in development, we have injected a construct containing a toxin gene under the control of the rat type II collagen promoter and enhancer. The construct, pDAS10‐DTA, contained the diphtheria toxin A chain gene under the control of type II collagen sequences which had been used previously to target cartilagenous tissues in transgenics. Inspection of developing fetuses at various stages of gestation revealed a high number of aborted implants as well as abnormally developing fetuses. These abnormal fetuses were of small size, had shortened and underdeveloped limbs, cleft palates, and generally resembled a phenotype similar to chondrodystrophic mice. Histological comparisons of normal and abnormal fetuses indicated a reduced amount of extracellular matrix surrounding chondrocytes, and a disorganized appearance of the tissue. These results suggest that the expression of the toxin has occurred in chondrocytes and altered the survival and development of the transgenic mice. These results also indicate that the promoter and enhancer sequences contained in the transgene controlled the developmental expression of the type II collagen gene expression.
The effect of in vivo glutathione depletion with buthionine sulfoximine on rat embryo development
Authors: Hales Barbara F. , Brown Heather 
Published: June 2005

AbstractGlutathione is an abundant endogenous nucleophile whose depletion may have adverse effects on a number of cellular processes, including protein and DNA synthesis, amino acid transport, and detoxification of reactive electrophiles. Previous studies have indicated that a certain basal level of glutathione is essential for normal development in vitro in the whole rat embryo culture system. The objective of this study was to determine the effect of glutathione depletion with buthionine sulfoximine on the development of rat embryos in vivo. Timed pregnant Sprague‐Dawley rats were treated by gavage on days 10 and 11 of gestation with saline (control) or with L‐buthionine‐(S,R)‐sulfoximine (4 or 8 mmol/kg). Pregnancy outcome was assessed on day 12 or day 20 of gestation. The glutathione content of embryos and of maternal organs was measured on day 12. Glutathione concentrations were significantly decreased in the embryos and in maternal muscle and ovary but not in maternal liver and kidney. Glutathione depletion, when assessed on day 12 of gestation, was found to result in an increase in the numbers of dead and malformed embryos. Treatment with the higher dose of buthionine sulfoximine resulted in the death of 13.2% of the total implanted embryos; of the surviving embryos, 21.7% were malformed. There was also a significant decrease on day 12 after treatment with the higher dose of buthionine sulfoximine in the embryonic total morphological score, a measure of the developmental stage of the embryos (control, 57.7±1.0; 8 mmol/kg buthionine sulfoximine, 52.8±1.8). No significant effect of treatment with either dose of buthionine sulfoximine with respect to growth parameters was observed on day 12 of gestation. Interestingly, no significant effect of treatment with either dose of buthionine sulfoximine on numbers of pups, resorptions, malformations, or fetal weight was found in the litters examined on day 20 of gestation. Thus, after glutathione depletion with buthionine sulfoximine, an increase in malformations and developmental delay is found on day 12 of gestation; however the malformations observed in day 12 embryos apparently do not persist during later development.
Review of drug‐induced limb defects in mammals
Authors: Sanders Duane D. , Stephens Trent D. 
Published: June 2005

AbstractThe 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.
Critical period of rat development when sidedness of asymmetric body structures is determined
Authors: Fujinaga Masahiko , Baden Jeffrey M. 
Published: June 2005

AbstractWe recently reported that rat embryos cultured from the presomite stage in a medium containing the alpha‐1 adrenergic agonist, phenyl‐ephrine, have a high incidence of situs inversus. In the present study, we have determined more precisely the critical period of development when situs inversus is induced. Rat embryos were harvested at 8 AM on Day 9 of gestation (plug day = Day 0), and divided into different stages of development, namely, early, mid, and late primitive streak stages and early, mid, and late neural plate stages. They then were cultured in rotating bottles to which phenylephrine, 0.5 mM, was added for various durations. After 49 hr of culture, embryos were examined for general morphology including sidedness of the bulboventricular loop, tail, and chorioallantoic placenta. Phenylephrine increased the incidence of situs inversus above control when administered throughout culture from either the early neural plate stage or before, and when administered for 4 hr or more from the early neural plate stage. This increase was significant even at the mid and late primitive streak stages when the control incidence was high. Our results suggest that sidedness of asymmetric body structures is determined during the early neural plate stage. This period is well before the 6–8‐somite stage when morphological signs of body asymmetry first appear.
Heterogeneity of neural tube defects in europe: The significance of site of defect and presence of other major anomalies in relation to geographic differences in prevalence
Authors: Dolk H. , de Wals P. , Gillerot Y. , Lechat M. F. , Ayme S. , Cornel M. , Cuschieri A. , Garne E. , Goujard J. , Laurence K. M. , Lillis D. , Lys F. , Nevin N. , Owens J. , Radic A. , Stoll C. , Stone D. , Kate L. Ten 
Published: June 2005

AbstractIn the period 1980–1987, neural tube defects were two to three times more prevalent in populations covered by EUROCAT registries in the United Kingdom and Ireland (UKI) than in Continental Europe and Malta (CEM). 1864 NTD cases in a total population of 580,000 births in UKI and 455 cases in a population of 380,000 births in CEM were analysed to find if there were differences in the ratio of prevalence rates between UKI and CEM according to site of the defect and association with non‐central nervous system (CNS) anomalies. The prevalence rate ratio was high for anencephaly with accompanying spina bifida, iniencephaly, and upper spina bifida, and low for encephalocele, lower spina bifida, and anencephaly without other neural tube defects. There was a greater female excess for anencephaly with accompanying spina bifida, iniencephaly, and upper spina bifida than for other defects in both geographic areas. There was a female excess for encephalocele in UKI but a male excess in CEM. Certain sites (anencephaly with accompanying spina bifida, iniencephaly, and encephalocele) were more likely to have accompanying non‐CNS anomalies. The prevalence rate ratio of multiply malformed NTD was in general lower than for isolated NTD but showed the same pattern by site. The prevalence rate ratio was high for multiply malformed anencephaly with accompanying spina bifida, iniencephaly, and upper spina bifida. The sex ratio was similar between isolated and multiply malformed cases when site of the defect is taken into account. It is concluded that the geographic prevalence pattern and sex ratio differ according to site of NTD but do not differ substantially according to whether NTD is isolated or associated with non‐CNS anomalies.
Toxicity of sera from individuals with Chagas' disease to cultured rat embryos: Role of antibodies to laminin
Authors: Robbins Bertha , Klein Norman W. , Cavalcanti Hamilton 
Published: June 2005

AbstractIn previous studies antilaminin antibodies in the sera of immunized monkeys and rats were found to be toxic to cultured rat embryos. In order to extend these studies to humans, head‐fold stage rat embryos were cultured for 48 hours on ten different serum samples from individuals with Chagas' disease. All embryos (n = 20) cultured on these sera were found to be abnormal. Using ELISA, Western immunoblot, and indirect immunofluorescence it could be shown that antibodies in these sera reacted with laminin. That these antilaminin antibodies were, at least in part, responsible for the toxicity was indicated 1) by reduced cultured embryo toxicity for six of seven serum samples after pre‐absorption with purified laminin, 2) by demonostrating a relationship between the amount of affinity‐purified antilaminin IgG added to control serum for culture and the severity of embryo abnormalities seen at the end of culture, and 3) by the sera's failing to react with other basement membrane proteins, including type IV collagen, fibronectin, osteonectin, and heparan sulfate proteoglycan.
Immunohistochemical localization of chondroitin and heparan sulfate proteoglycans in pre‐spina bifida splotch mouse embryos
Authors: Trasler Daphne G. , Morriss‐Kay Gillian 
Published: June 2005

AbstractThe splotch (Sp) mutation on mouse chromosome I is a genetic model for the neural tube defects spina bifida and exencephaly. Embryos carrying Sp or its allele splotch‐delayed (Spd), have been shown to have delays in neural tube closure, and neural crest cell emigration, as well as a reduction in extracellular space around the neural tube. Pre‐spina bifida Sp and Spd embryos have abnormalities of notochord, mesoderm and neuroepithelial development. Chondroitin sulphate proteoglycans (CSPG) and heparan sulfate proteoglycans (HSPG) have been shown to play essential roles during neural tube closure and neural crest cell emigation and migration and thus might well be affected by the splotch mutation. Therefore, the effects of Sp and Spd on the temporal and spatial distributions of CSPG and HSPG were studied in pre‐spina bifida embryos cytogenetically identified as Sp/Sp (Spd/Spd), Sp/ + (Spd/+) or + / +. Immunohistochemical localization of CSPG by means of the CS‐56 monoclonal antibody showed that in Sp/Sp head sections, the neuroepithelial basement membranes stained more intensely at 5‐, 10‐, and 15‐somite stages, whereas similar staining was observed at 16‐ and 19‐somite stages compared with matched +/+ sections. In caudal sections Sp/Sp again showed a more intense stain for CSPG in the neuroepithelial basement membranes in all sections (except one comparison, in which staining was similar) from embryos of 14‐, 15‐, 16‐, and 19‐somite stages, compared to matched +/+ sections. Heterozygotes did not differ consistently from the mutant or the normal ( + / + ) embryos in CS‐56 stain intensity. Immunohistochemical staining with antibody to a basement membrane HSPG showed a more intense stain in the two Spd/Spd 10‐somite stage embryos tested than in matched +/+ embryos. It is suggested that the greater intensity of CSPG and HSPG staining in Sp and Spd mutant embryos compared to +/+ embryos could be caused by an altered sequence within the Sp gene locus that either directly disrupts the production or degradation of these and other molecules, or does so indirectly through its interaction with neural cell adhesion molecules.