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K K Sulik

Publications and source records attributed to K K Sulik.

At least 37 records · Page 2Linked to original sources
PubMed1995

Teratogenicity of low doses of all-trans retinoic acid in presomite mouse embryos.

This study was designed to examine the developmental dose response for all-trans retinoic acid (TRA) administered at presomite stages in mouse embryos. Previous studies using hamsters [Shenefelt (1972) Teratology 5:103-118] have shown that developmental stages corresponding to those present early on gestational day (GD) 7 in mice are most sensitive to retinoid-induced teratogenesis. Our preliminary studies showed that at this treatment time, gavage dosages of 7.5 mg/kg maternal body weight administered to C57B1/6N mice, an inbred strain, resulted in severe craniofacial malformations representing the holoprosencephaly, aprosencephaly spectrum. Additionally, in an outbred mouse strain, CD-1, exencephaly was induced by dosages of 2.5 mg/kg TRA and above. Readily detectable abnormalities of the eyes, including anophthalmia and severe microphthalmia and iridial colobomata, were induced by even lower doses cf TRA in the C57B1/6N strain. Incidences of micro/anophthalamia were 6.7%, 8.1%, 12.9%, and 32.4% at 0, 0.313, 0.625, and 1.25 mg/kg, respectively. The dosages required to induce significant incidences of exencephaly (2.5 mg/kg) and severe ocular abnormalities (1.25 mg/kg) on GD 7 in mice are approximately 50-100-fold less than those that are commonly used to examine the teratogenicity of this compound at later developmental stages in this species. The trend toward an increase in the incidence of severe ocular malformations at the lowest dose examined and the fact that subtle ocular malformations were not taken into account for this study suggest that even lower dosages may be effective.(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormalities, Drug-Induced↗
PubMed1995

Ethanol-induced teratogenesis: free radical damage as a possible mechanism.

To investigate the possibility of a free radical mechanism for ethanol-induced teratogenesis, gestational day 8 mouse embryos were exposed for 6 hr in whole embryo culture to a teratogenic dosage of ethanol alone (500 mg%) or in conjunction with an antioxidant, superoxide dismutase (SOD; 300 U/ml). For subsequent analysis, some embryos were examined at the end of this 6-hr period, while others were removed to control medium and cultured for an additional time period. Ethanol exposure resulted in increased superoxide anion generation and increased lipid peroxidation (as noted 6 hr after initial ethanol exposure) and in excessive cell death (as noted 12 hr after initial exposure) in the embryos. Following a total of 36 hr in culture, a high incidence of malformation, including failure of the anterior neural tube to close in 63% of the ethanol-exposed embryos, was noted. The ethanol-induced superoxide anion generation, lipid peroxidation, excessive cell death, and dysmorphogenesis were diminished in embryos co-treated with SOD, suggesting that the teratogenicity of ethanol is mediated, at least in part, by free radical damage.

Abnormalities, Drug-Induced↗
PubMed1995

Zinc deficiency causes apoptosis but not cell cycle alterations in organogenesis-stage rat embryos: effect of varying duration of deficiency.

Zinc deficiency is teratogenic in all species in which it has been examined. Zinc is an essential component of enzymes involved in DNA synthesis and cell proliferation, and may play an as yet undetermined role in apoptosis. To further our understanding of the role of zinc in normal development, we examined cell death and cell cycle parameters in embryos of pregnant rats fed a zinc-deficient diet for 2 to 10 days (0.5 microgram zinc/g diet; zinc-adequate diet was 25 micrograms zinc/g). To elucidate sensitive periods of development and susceptible cell populations, dams were fed the zinc-deficient diet from gestation day 1, 3, 7, or 9 and killed on day 11. Embryos were examined for morphology and developmental stage. From each litter, 2-3 embryos were stained with Nile blue sulfate (NBS) to visualize cell death, 3 embryos were frozen for flow cytometric cell cycle analysis and cell counts, and selected embryos were preserved for histological examination. Dams fed the zinc-deficient diet for more than 3 days reduced their food intake through gestation day 8 but increased food intake on day 9. Maternal plasma zinc dropped to 10-25% of control levels in the zinc-deficient groups. Zinc deficiency from gestation day 1 or 3 resulted in two categories of affected litters on day 11. One category had embryos which were morphologically normal but displayed extensive NBS staining in the visceral arches, neural tube, and somites. The second category had developmentally retarded or maldeveloped embryos which showed little NBS staining. Zinc deficiency from gestation day 7 produced cell death in the posterior dorsal midline in the area of premigratory neural crest cells, which was confirmed by histological examination. Zinc deficiency from gestation day 9 did not affect morphology or NBS staining. Percentages of cells in the G0/G1, S, and G2M phases of the cell cycle on gestation day 11, determined by flow cytometry, were similar to controls in all groups. This study shows that as few as 4 days of maternal zinc deficiency can produce excess embryonal cell death, and that neural crest cells may be particularly sensitive.

Animals↗
PubMed1994

Cell death and cell cycle perturbation in the developmental toxicity of the demethylating agent, 5-aza-2'-deoxycytidine.

DNA methylation is a probable mechanism for regulating gene expression, and alterations in methylation may significantly affect embryonic development. We administered the cytidine analogue 5-aza-2'-deoxycytidine (dAZA), a specific and potent demethylator of DNA, to pregnant mice to determine its teratogenicity and effects on embryonic cell death and cell cycle. Groups of females were dosed intraperitoneally on gestation day 10 with doses of 0.05-3 mg/kg dAZA and killed at 4, 8, or 28 hr later. Two embryos per litter were immediately stained with Nile blue sulfate (NBS) to identify areas of cell death; the remaining embryos were frozen and stored for subsequent flow cytometric (FCM) analysis of the cellular DNA synthetic cycle in limb buds. A dose-related accumulation of cells in the S and G2/M phases was observed at 4 and 8 hr after maternal dosing. S-phase accumulation was the most sensitive indicator of effect; a dose-related increase in the percentage of hindlimb bud cells in S-phase was evident at all dosages 4 hr after maternal dosing. By 28 hr postdosing, a normal cell cycle phase distribution was observed at doses of < 0.3 mg/kg. However, cell cycle perturbations persisted at higher dosages. NBS staining demonstrated increased cell death in areas of rapid cell division, indicative of replication-associated cytotoxicity, at doses of > or = 0.1 mg/kg. Observation of litters from additional dams killed at term revealed that at dosages of > or = 0.3 mg/kg, cleft palate and hindlimb defects were significantly elevated. In addition, above 0.3 mg/kg, fetal weight was significantly decreased.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Cloacal and urogenital abnormalities induced by etretinate in mice.

Etretinate, a synthetic retinoid, is a potent teratogen. It has previously been shown that acute exposure of gestational day 8 (equivalent to human week 4 post-fertilization) C57BL/6J mouse embryos to this retinoid results in a spectrum of abnormalities that are recognized as constituting caudal regression (dysgenesis). These defects, which include spina bifida, imperforate anus, genitourinary anomalies, omphalocele and limb anomalies, result from a major insult to the primitive streak, that is the gastrulation process. Developmental stages present early on gestational day 9 in mice represent the final stages during which the primitive streak contributes to the trunk of the embryo and, therefore, the last opportunity for abnormalities within the realm of caudal regression to be induced. In fact, acute etretinate exposure on gestational day 9 resulted in anal and urethral atresia, bladder and ureteral dilatation, and tail deficiencies as observed in 251 near-term fetuses in this study. To examine in further detail the gestational day 9 etretinate induced urogenital and anal abnormalities and their pathogenetic basis, analyses were conducted using scanning electron microscopy, light microscopy, antegrade cystourethrograms and a vital staining technique as early as 6 hours following maternal drug administration. It appears that diminution of the caudal cell populations, including those of and those surrounding the cloaca, at this critical stage of embryogenesis accounts for the observed phenotype. We propose that anal and urethral atresia temporally represents the end of the caudal regression (dysgenesis) syndrome.

Abnormalities, Drug-Induced↗
PubMed1993

Pathogenesis of craniofacial and body wall malformations induced by ochratoxin A in mice.

Ochratoxin A (OA), a mycotoxin commonly found in soils and on moldy food such as cereal grains, is a potent teratogen. The present investigation was designed to examine the teratogenicity of OA administered acutely at early post-implantation stages in mice, with particular emphasis on the pathogenetic basis of induced malformations. Maternal OA administration on gestational day (GD) 7 or 8 resulted in excessive amounts of cell death in selected cell populations. After a single dose of 2-4 mg/kg, excessive cell death was notable within 6 hours, and persisted to 36 hours post-treatment. As observed in GD 14 or 18 fetuses, the spectrum of induced craniofacial malformations included exencephaly, midfacial clefting, cleft lip, as well as hypotelorism, and synophthalmia associated with holoprosencephaly. Body wall defects involved either the abdominal wall alone, or in combination with the thoracic wall, resulting in partial or complete exposure of the viscera. Potential mechanisms for OA-induced selective cell killing are discussed.

Abnormalities, Drug-Induced↗
PubMed1993

Postulated mechanisms underlying the development of neural tube defects. Insights from in vitro and in vivo studies.

In recent years, use of animal models has resulted in acquisition of a significant amount of new information regarding normal and abnormal neural tube development. Studies of mutant and of teratogen-exposed mice are complementary, with each providing insights that promise to advance our understanding of the other. Analysis of teratogen-exposed embryos is best suited for identifying susceptible developmental stages and vulnerable populations. Advances in molecular genetics, with the ability to identify gene products, their cell/tissue location, and, potentially, to understand their function, will make naturally occurring as well as man-made mutants invaluable for understanding the heterogeneous mechanisms that underly NTDs.

Animals↗
PubMed1992

Experimental fetal alcohol syndrome: proposed pathogenic basis for a variety of associated facial and brain anomalies.

Acute teratogenic exposure of C57Bl/6J mouse embryos to ethanol in vivo results, within 12 hours of initial insult, in excessive cell death in selected cell populations. The patterns of excessive cell death observed following exposure of gestational day 8 embryos (late presomite--approximately 5 somite pair stages) vary somewhat temporospatially, but primarily involve the cell populations at the rim of the anterior neural plate. The cell death patterns appear to be pathogenically correlated with subsequently observed malformations including exencephaly (anencephaly), arhinencephaly, pituitary dysplasia, bilateral or unilateral cleft lip, maxillary hypoplasia, and median facial deficiencies and clefts. The association of these brain and facial malformations in this model, and perhaps in humans, may be accounted for by early insult to the selected cell populations identified in the current investigation.

Abnormalities, Drug-Induced↗
PubMed1992

Pathogenesis of ethanol-induced limb reduction defects in mice.

Acute administration of dosages of 2.5, 2.8, or 2.9 g/kg of ethanol to pregnant C57BL/6J mice on gestational day 9 1/4 resulted in major malformations of the forelimb including postaxial ectrodactyly, preaxial syndactyly, and reduction defects involving intermediate digits. The incidence and severity of these defects was positively correlated with dosage. Sidedness of the defects was also dose-dependent. In affected embryos, excessive amounts of cell death were notable within 5-9 hr of treatment initiation in selected cell populations. Cell death was primarily distributed in two regions of the developing limb bud--a ventrodistal ectodermal cell population (apical ectodermal ridge) and a proximal mesenchymal cell population. The patterns of cell death observed appear to be pathogenically related to the limb defects noted at later stages. In particular, it would appear that the deficiencies in the apical ectodermal ridge resulting from ethanol-induced cell death can account for virtually all the subsequent limb defects.

Abnormalities, Drug-Induced↗
PubMed1992

Patterns of ethanol-induced cell death in the developing nervous system of mice; neural fold states through the time of anterior neural tube closure.

Vital staining and routine histological analyses of mouse embryos 12 h after acute maternal ethanol administration (2.9 g/kg) illustrated that selected neuronal cell populations are killed. At the time of treatment, embryos had 5-15 somite pairs, corresponding to the developmental stages occurring in humans during the fourth week of post-fertilization; i.e. when neural folds are present and neural tube fusion begins. Affected cell populations in embryos having 6-26 somite pairs (up to the stage of anterior neuropore closure) were in discrete locations in the alar and basal plates of the rhombencephalon, in the otic placode/vesicle, and in the regions of the epibranchial placodes, olfactory placodes and trigeminal ganglion. The potential basis for the vulnerability of these cell populations to ethanol-induced cell death is discussed. Our understanding of the scope of ethanol-induced CNS damage is dependent upon further defining ethanol-sensitive cell populations at all stages of CNS development.

Animals↗
PubMed1992

Characterization of the upper urinary tract anatomy in the Danforth spontaneous murine mutation.

Absence or maldevelopment of the ureteral bud is thought to represent the final pathophysiological pathway resulting in renal anomalies ranging from agenesis to duplication. Little is known about the events preceding anomalous or absent ureteral bud formation. We describe the renal and ureteral anomalies found in a spontaneous murine mutation associated with a short tail: the Danforth or Sd mutation. Thirteen heterozygous pairs of mice were mated. Of 57 near-term progeny 40 had short tails. Microdissection revealed both kidneys and ureters in 35%, neither kidneys nor ureters in 27.5%, absence of the left kidney and ureter in 10%, absence of the right kidney and ureter in 7.5%, and absence of 1 or both kidneys associated with a blind-ending ureter in 20% of the mice. Scanning electron microscopy of gestational day 12 fetuses revealed unilateral or bilateral absence of the metanephros in some embryos, including some with a ureteral bud. Thus, primary absence of the metanephros may have a role in renal agenesis. Additional findings suggest that compensatory renal hypertrophy occurs in utero in the fetuses with unilateral renal agenesis. The morphological abnormalities involving the kidneys in the Sd mutation may represent an excellent model to study the pathophysiology of renal agenesis and mechanisms of normal renal development.

Animals↗
PubMed1992

Pathogenesis of retinoid-induced hindbrain malformations in an experimental model.

Among the findings associated with the human Retinoic Acid Embryopathy are hindbrain defects including the Arnold-Chiari malformation. The human Arnold-Chiari malformation (ACM) is a malformation complex where the cardinal feature is herniation of the caudal hindbrain into the vertebral column; it is frequently accompanied by lumbosacral myelorachischisis and hydrocephalus. Mice exposed to all-trans-retinoic acid or etretinate on day 8.25 of pregnancy, produce offspring with hindbrain herniation and caudal lumbosacral myelorachischisis in addition to a variety of other craniofacial and caudal malformations. Several experimental animals were observed to lack the caudal myelorachischisis proving that this lesion is not required to generate hindbrain herniation. We provide evidence that the cranial malformations, including hindbrain herniation, result from primary damage to the neural crest and the rhombencephalon. The vulnerability of these sites appears to be correlated with the presence of normal physiological cell death. While these experimental animals differ in many respects from the typical human Arnold-Chiari malformation, they may provide some insight into the pathogenesis of the latter.

Abnormalities, Drug-Induced↗
PubMed1991

Relationship of cell death to cyclophosphamide-induced ocular malformations.

C57BL/6J mice were used to study the ocular teratogenic effects of cyclophosphamide administered to pregnant females on d 9 of pregnancy at a dose of 5 mg/kg body weight. Nile blue staining demonstrated increased cell death at the base of the optic stalk, in the optic vesicle, and in the perivesicular mesenchyme in treated embryos. Malformations studied at gestational d 11 and 16 by light and scanning electron microscopy included microphthalmos, microphakia, and aphakia and were predictable based upon patterns of increased cell death. These anomalies are similar to those reported with exposure to ethanol or isotretinoin on gestational d 7.

Animals↗
PubMed1991

Effects of magnetic resonance imaging on eye development in the C57BL/6J mouse.

An 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 less than or equal to .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 remained that the mouse strain utilized in this investigation was genetically prone to malformations).

Animals↗
PubMed1991

Pathogenesis of ethanol-induced hydronephrosis and hydroureter as demonstrated following in vivo exposure of mouse embryos.

Urinary tract abnormalities have been noted to occur in 10-27% of individuals diagnosed as having Fetal Alcohol Syndrome. Among a wide range of functional and structural abnormalities, renal agenesis/hypoplasia, hydronephrosis, and ureteropelvic obstruction feature most prominently. This study was designed to examine the pathogenesis of ethanol-induced urinary tract abnormalities in a mouse model. C57Bl/6J mice were acutely exposed to two doses of ethanol (2.9 g/kg IP) administered 4 hours apart beginning on gestational day (GD) 9, hour 4. This resulted in an incidence of 40.7% urinary tract anomalies among GD18 fetuses. With the exception of duplicate ureter, urinary tract abnormalities consisted exclusively of hydroureter/hydronephrosis. Examination of GD13-17 fetuses revealed that the first grossly detectable differences in the urinary tracts of control vs. affected specimens occurred on GD16 and initially only involved ureteral changes. Hydronephrosis was first detected on GD17. A contributing factor to the development of hydronephrosis appears to be the abnormal location of the ureterovesicle junction which commonly involves duplicate ureteral lumens with resultant functional obstruction to urine flow at the distal end of the ureter. Study of the early pathogenetic changes which appear to result in the urinary tract malformations observed involved utilization of scanning electron microscopy, vital dye (Nile blue sulphate) staining of whole embryos, and analysis of histological sections. These studies revealed that 12 hours following initial maternal ethanol exposure, embryos have excessive amounts of cell death localized in the region of the developing mesonephric duct just proximal to the cloaca. Also affected were premigratory neural crest cells located just proximal to the posterior neuropore. We conclude that excessive amounts of ethanol-induced cell death in these selectively vulnerable populations could account for the subsequently observed urinary tract malformations.

Abnormalities, Drug-Induced↗
PubMed1990

Phenotypic characterization of the transgenic mouse insertional mutation, legless.

In this report, we describe the dysmorphologic phenotype associated with the transgenic insertional mutation legless. This autosomal recessive, perinatally lethal mutation results in an interesting pleiotropic array of congenital malformations. The phenotype of the legless mutation in homozygous perinatal mutants is compared to wild-type nontransgenic and heterozygous siblings. Skeletal, craniofacial, and visceral malformations are characterized. We have observed by skeletal analysis a consistent loss of distal hindlimb structures, as well as the loss of distal forelimb structures with a predilection for the preaxial side of the developing forelimb. Craniofacial malformations commonly observed appear to represent a range of severity of affect, with the mildest manifestation evident as apparently shallow lateral clefts of the upper lip and mild midfacial clefts accompanied by clefts of the secondary palate. At the severe end of the spectrum, the midline clefts of the face (and secondary palate) are very wide, with obvious accompanying frontonasal encephaloceles and overt lateral clefts of the upper lip. Examination of the mutant brain has demonstrated marked defects in the anterior structures, particularly the olfactory lobes and cerebrum, in greater than 90% of the brains studied. Observation of the internal viscera has identified transposition of thoracic and abdominal organs in approximately 50% of the mutant offspring. The limb, head, and visceral defects were not observed in the wild-type nontransgenic or heterozygous siblings. Transgenic insertional mutations leading to congenital malformations are useful because the transgene sequence may serve as a tag to facilitate molecular retrieval. Analysis of the flanking DNA sequences will allow the identification of the interrupted gene. A complete description of the mutant phenotype will assist in the understanding of this genetic locus.

Animals↗
PubMed1990

Cyclophosphamide teratogenesis: evidence for compensatory responses to induced cellular toxicity.

Cyclophosphamide (CP) administered ip to pregnant mice on day 10 of gestation (day of plug = day 0) is teratogenic (exencephaly, cleft palate, and limb malformations) at 20 mg/kg and embryolethal at higher doses. In the present study, CP was administered at 1, 5, 10, or 20 mg/kg on day 10 of gestation. Embryos were removed at 8 and 28 hr postdosing, and two embryos from each litter were immediately stained with Nile blue sulfate (NBS) to identify areas of cell death. The remaining embryos were frozen and forelimb buds subsequently removed for flow cytometric (FCM) analysis of the cellular DNA synthetic cycle. Additional litters were examined near term (day 17) for morphological abnormalities; these data were correlated with embryonic toxicity as detected by NBS staining and FCM analysis. Only the highest dose produced malformations. In marked contrast, a dose-related increase in the percentage of limb bud cells in the S (DNA synthetic) phase of the cell cycle was detectable at all doses. Inhibition of DNA synthesis was detected at all doses 8 hr post exposure and persisted through 28 hr for doses greater than or equal to 10 mg/kg. NBS staining indicated increased cell death in the alar plate of the neural tube 28 hr after exposure to 10 mg/kg CP and generally increased cell death in areas of rapid cell proliferation throughout the embryo at 20 mg/kg. The absence of an overt teratogenic response at dose levels that produced significant perturbation of the cell cycle indicates that a measure of embryonic damage can be compensated for or repaired. The implications of these findings for the existence of thresholds in developmental toxicity are discussed.

Animals↗