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Biomedical subjects

T W Sadler

Publications and source records attributed to T W Sadler.

At least 73 records · Page 4Linked to original sources
PubMed1984

Zinc amelioration of cadmium-induced teratogenesis in vitro.

Mouse embryos were exposed to cadmium (5.35 micrograms/ml) for either 0.5h or 1h and then transferred to fresh serum for the duration of the experiment. Embryos exposed for 0.5h developed numerous malformations that were primarily localized to the craniofacial region. Embryos exposed for 1h to the same level of cadmium all failed to thrive. In a separate series of experiments zinc (10 micrograms/ml) was added 15 minutes prior to the addition of cadmium. Embryos treated with cadmium for 30 min. after the addition of zinc, resulted in 15 of 16 embryos developing normally. The second group of embryos treated for 1h after preincubation with zinc resulted in 93% of the embryos surviving after 48h, albeit malformed. These results suggest that: 1) Exposure time to a teratogen is a critical parameter to consider when designing in vitro experiments 2) zinc is effective in protecting embryos against cadmium induced teratogenesis and 3) the whole embryo culture system is effective in demonstrating biological interactions between agents.

Abnormalities, Drug-Induced↗
PubMed1983

Morphogenesis of median facial clefts in mice treated with diazo-oxo-norleucine (DON).

The morphogenesis of median facial clefts induced in mice by treatment with diazo-oxo-norleucine (DON) was studied. Following maternal treatment with 0.4 mg/kg DON on the 11th gestational day, 23.1% of fetuses recovered at the 18th day exhibited median facial clefts, which were characterized by a separation in the midline of normal midfacial components, i.e., the premaxilla, nasal bones, and nasal capsule. Malformed embryos could first be identified grossly 24 hr after DON administration by the presence of an abnormally wide separation between the two narrowed medial nasal processes. Evidence of cellular degeneration was observed in the mesenchyme of the nasal processes of DON-treated embryos 8 and 12 hr after treatment, but little or no pyknotic debris remained at 24 hr post-injection. Loss of cells due to cell death was reflected in decreased cell density observed in all areas of facial mesenchyme examined 24 hr after DON administration. It is suggested that DON-induced median facial clefts may be caused by a reduction in tissue volume, particularly in the midline, or by an interference with normal facial growth resulting in increased facial width and consequent failure of merging of the medial nasal processes.

Abnormalities, Drug-Induced↗
PubMed1983

A comparison of the in vivo and in vitro response of mammalian embryos to a teratogenic insult.

This study serves to further define the capabilities of the whole embryo culture system using the known teratogen, hydroxyurea (HU). An initial in vivo study was performed whereby day 9 pregnant mothers were injected i.p. with 300 mg/kg HU. Dams were sacrificed 2 days later and embryos were analyzed for malformations and total embryonic protein. In addition, the peak plasma value from injected dams was found to be approximately 300 micrograms/ml with a plasma half-life of 30 min. These values were then reproduced in the culture system with results noted in cultured embryos with respect to the types of malformations found. Additional in vitro experiments were performed varying both exposure time and drug level concentrations. Results indicate that both of these parameters are important considerations when designing in vitro experiments.

Abnormalities, Drug-Induced↗
PubMed1983

Effects of maternal diabetes on early embryogenesis. The role of insulin and insulin therapy.

Using the system of whole embryo culture the effects of insulin on early mouse embryogenesis were investigated. Three experimental approaches were employed in which (1) serum from diabetic rats receiving insulin therapy was used as culture medium; (2) insulin was added directly to serum collected from diabetic rats for use as culture medium; (3) insulin was added directly to medium (serum) collected from control rats. Mouse embryos were cultured in each of these media for 24 h and then evaluated for growth and malformations. The results demonstrated that insulin therapy was effective in reducing the incidence of malformations and growth retardation produced by serum from diabetic rats receiving no hormone supplement. However, addition of insulin directly to serum collected from diabetic rats was not effective in reducing the rate of abnormalities produced by this medium. Finally, addition of insulin at extremely high concentrations (10,000 muU/ml) produced no abnormal embryos. Thus, it appears that insulin therapy is successful in reducing malformation rates and that the hormone itself is not teratogenic in this system.

Animals↗
PubMed1983

Effects of maternal diabetes on early embryogenesis. Alterations in morphogenesis produced by the ketone body, B-hydroxybutyrate.

The present study used the whole embryo culture technique to determine the effects of the ketone body, B-hydroxybutyrate (B-OHB), on organogenesis in mouse embryos. Embryos of two stages (3-4 and 5-6 somites) were exposed for 24 h to a racemic mixture of D-L B-OHB at levels of 8, 16, or 32 mM/L. An abnormal pattern of development resulted, consisting of growth reduction and inhibition or delay of neural tube closure in the cranial and/or caudal regions of the embryo. These effects were dose- and age-dependent, such that younger embryos were more frequently affected than older ones, and increasing doses produced a higher rate of malformation. Growth reduction as evidenced by embryonic protein showed similar relationships. Histologic analysis of embryos exposed to 32 mM/L B-OHB for 24 h revealed numerous cytoplasmic "vacuoles" widespread throughout the neuroepithelium, mesenchyme, and ectoderm. Ultrastructurally, these "vacuoles" proved to be mitochondria that had undergone high-amplitude swelling with a loss of matrix density and few identifiable cristae. No other consistent ultrastructural changes were noted, and the mitochondria of control tissues displayed a typical orthodox configuration. While this study does not conclusively limit the effects to the D-form of B-OHB, possible relationships exist between the ultrastructural alterations, ketone body metabolism, and abnormal morphogenesis.

3-Hydroxybutyric Acid↗
PubMed1982

Actin distribution patterns in the mouse neural tube during neurulation.

With the use of antibodies to actin and indirect immunofluorescent techniques regions of increased actin concentration were demonstrated first in basal and later in apical areas of mouse neuroepithelial cells. These patterns of staining corresponded to shape changes observed in cranial neural folds as they initially elevated from the neural plate and later moved toward the midline.

Actins↗
PubMed1982

Whole embryo culture: a screening technique for teratogens?

Head-fold and early somite stages of mouse and rat embryos maintained in whole-embryo culture throughout much of the period of organogenesis demonstrate normal growth and morphogenesis. Embryos directly exposed to teratogens in the culture system and embryos cultured in serum from adult animals treated with toxic compounds develop congenital abnormalities that resemble malformations induced in vivo by these same agents. Furthermore, the defects are dose- and stage-dependent, such that higher doses produce a greater percentage of malformed embryos, and younger embryos are more susceptible than older ones. These results--together with the observations that 1) data are rapidly produced, 2) quantifiable endpoints can be measured in mammalian systems at costs considerably below those inherent in in vivo analyses, and 3) the potential exists for monitoring serum toxicity in humans and primates--suggest that the whole-embryo culture system may be useful as a screening technique for potentially teratogenic substances.

Animals↗
PubMed1981

Effects of vitamin A on endocardial cushion development in the mouse heart.

Retinoic acid (RA) (78mg/kg) administered to ICR mice on days 9.0,9.5 and 10.0 of pregnancy (plug day = day 1), resulted in cardiac malformations in 37.6% of the surviving fetuses, including transposition of the great arteries, ventricular septal defects, and double outlet right ventricle. Histological examination of the hearts of embryos observed 24 hours after in vivo or in vitro exposure to RA on day 9 revealed abnormalities in endocardial cushion tissue. The volume of the atrioventricular endocardial was reduced in treated embryos as was the ratio of the size of the cushions to the size of the heart. The endothelial layer of the atrioventricular endocardial cushions appeared to be unaffected by the retinoic acid, however, the mesenchymal cushion cells were significantly reduced in number when compared with controls. Labeling with [3H]-thymidine indicated that the mitotic activity of the mesenchymal cell population was significantly decreased while that of the endothelial cells was comparable to control levels. The extracellular matrix or cardiac jelly of the endocardial cushions also appeared to be affected by RA exposure, as shown by studies utilizing colloidal iron to stain GAGs, which revealed a decrease in the amount of stainable material in treated cushions. Two possible cause for the reduced thymidine index of the cushion mesenchyme are discussed, namely, a direct effect of RA on the mesenchymal cells or an indirect effect via the altered extracellular matrix of the cushion tissue.

Abnormalities, Drug-Induced↗
PubMed1981

Culture of mouse embryos during neurulation.

A comparison between static versus rotator culture systems and a variety of media (rat serum, new born calf serum, DMEM and Waymouth's) was made in an attempt to promote in vitro growth of mouse embryos from the beginning of neurulation (headfold stage) to the closure of the neural tube and formation of the limb buds (48 h). The results demonstrate that good development can be achieved for 48 h using a rotator system and that 80% of embryos cultured on rotators show growth and differentiation similar to that obtained for the same time period in vivo. Static cultures are less successful and embryos grown in this system show lower protein content and somite numbers than those maintained on rotators. Undiluted rat serum is superior to all other media tested and supports better growth and development as monitored by total protein and developmental abnormalities.

Animals↗
PubMed1979

Distribution of surface coat material on nasal folds of mouse embryos as demonstrated by concanavalin A binding.

3H-concanavalin A and the concanavalin A-horseradish peroxidase staining technique were used to study the distribution of surface coat material on the epithelium of the nasal folds and nasal groove of mouse embryos. In stages shortly before and during epithelial fusion concanavalan A stained or labeled material was present at apical surfaces of epithelial cells of the nasal groove and nasal folds. Silver grains, representing bound 3H-concanavalin A, were counted in defined areas of the nasal groove and presumptive fusion area in both anterior and posterior regions of the nasal folds. For both stages examined there was a significant increase in the amount of 3H-concanavalin A bound by presumptive fusion areas in posterior regions of the nasal folds as compared with anterior regions; i.e., the atact between the nasal folds. This finding is consistent with results from investigations of palatal shelf and neural fold fusion which suggest that increased synthesis of surface coat material is associated with adhesion and fusion of epithelial folds and shelves.

Animals↗
PubMed1979

Culture of early somite mouse embryos during organogenesis.

Early somite (2-4) mouse embryos were explanted and then maintained in culture for 24 or 48 h intervals. Various types of media were tested and it was determined that rat serum supported normal growth over a period of 48 h, based on total protein analysis and histological comparisons with in vivo specimens. Other media including fetal calf serum and fetal calf serum and Waymouth's (1:1) supported some growth, but did not equal the success of using rat serum alone. During the 48 h culture period in rat serum, embryos developed to stages indistinguishable from embryos maintained for a similar time in vivo.

Animals↗
PubMed1978

Distribution of surface coat material on fusing neural folds of mouse embryos during neurulation.

Fusing and non-fusing regions of neural folds from mouse embryos were examined during neurulation for the distribution of extracellular macromolecules (surface coats) prior to and at the time of closure. Ruthenium red staining of 10th day ICR/DUB mouse embryos was used to detect the distribution of surface coat material. Light microscopic examination of fusing and non-fusing regions in the midbrain, hindbrain, and spinal cord showed a consistent increase in ruthenium red positive material immediately prior to closure. Heavy deposits of positive staining material were present along apical neural fold borders and overlying ectoderm cells. This staining pattern was consistent in the three regions examined, but the pattern of initial contact between opposing neural folds differed. In mid- and hindbrain areas contact was initiated by overlying ectoderm, whereas in spinal cord regions contact was first established by neuroepithelial cells. Once contact between opposing neural folds was initiated a decrease in stainable material was observed.

Animals↗
PubMed1977

Ultrastructural alterations in neuroepithelial cells of mouse embryos exposed to cytotoxic doses of hydroxyurea.

Developing neuroepithelial cells from the cranial region of neural folds were examined at various intervals from 15 minutes to four hours after administration of teratogenic (250 mg/kg) or embryolethal (500 mg/kg) doses of HU to ICR/DUB mice on ninth day of gestation. Thirty percent of surviving fetuses showed extencephaly after the teratogenic dose. The initial ultrastructural change in some neuroepithelial cells occurred within 15 minutes to one hour after treatment with the teratogenic dose and involved a breakdown of polyribosomes into monosomes which were dispersed evenly in the cytosome. At one to two hours, condensation of the cytoplasm and chromatin was observed along with distorted nuclear shape. At two to four hours, cells exhibited extremely condensed cytoplasm and fragmentation of the cells occurred. The affected cells showed pyknotic nuclei and segregation of fibrillar and granular components of the nucleolus. In some nuclei, particularly after treatment with the higher dose of HU, a condensation of the nucleolus was observed. At this stage images were obtained which indicated that neighboring cells phagocytosed the cellular fragments derived from the HU affected cells.

Abnormalities, Drug-Induced↗