Biomedical subjects

J M DeSesso

Publications and source records attributed to J M DeSesso.

30 records · Page 2Linked to original sources

PubMed1987

Maternal factors in developmental toxicity.

The maternal organism provides the developing embryo with its physical environment, nutrients, and a mechanism for eliminating metabolic wastes. Since the physiological state of the pregnant female affects her ability to provide those requirements for the developing embryo, it is not surprising that there are maternal factors that can affect the wellbeing of the embryo. Extremes of maternal age in both humans and animals have been implicated in growth retardation, as well as autosomal trisomies. The influence of maternal size on fetal size is more pronounced among larger species with longer gestation periods such as humans and domestic animals. A clear relationship between the parity of the mother and potential developmental toxicity in humans has not been established due to the confounding influences of maternal age. Among laboratory rodents, however, it appears that offspring of multiparous animals are at increased risk of developmental toxicity. A variety of infectious agents, particularly viruses, have either been demonstrated or implicated as causes of developmental toxicity. In addition, hyperthermia is a possible confounding factor inherent with maternal infection. Although under experimental conditions hyperthermia is teratogenic in laboratory animals, a causative role for transient hyperthermia, which occurs during febrile states concomitant with infections, cannot be clearly established. Chronic maternal vascular disease states including essential hypertension, heart disease, or diabetes mellitus are likely to contribute to uteroplacental insufficiency and developmental toxicity. Poor maternal nutrition among humans contributes to growth retardation, but not to malformations. The production of "abnormal" maternal antibodies, such as are present in Rh incompatibility, can cause fetal wastage. An important maternal factor in humans is uteroplacental insufficiency, which can occur in normal states like twinning, as well as in abnormal conditions including reduced placental size, chronic maternal hypoxia, or uterine ischemia. Although all these maternal factors can contribute to developmental toxicity, they do not necessarily occur as isolated events. Some developmental toxicants exert deleterious effects within both the embryo and the maternal system.

Animals↗

PubMed1981

Effects of hydroxyurea on hemodynamics of pregnant rabbits: a maternally mediated mechanism of embryotoxicity.

Hydroxyurea is a cytotoxic agent used in the management of chronic granulocytic leukemia. This compound is teratogenic and embryolethal in various animal species, and has been widely used in experimental studies aimed at understanding the possible mechanisms of drug-induced malformations. Previous studies from our laboratory have demonstrated that maternal subcutaneous injections of hydroxyurea produce immediate circulatory alterations in rabbit embryos similar to those observed subsequent to uterine artery occlusion. The present study was designed to investigate the possibility that the embryolethal and teratogenic properties of hydroxyurea might be due to alterations in maternal hemodynamics, i.e., constriction of the uterine vasculature, resulting in exposure of the embryo to uterine ischemia at critical stage of in utero development. This study demonstrates that hydroxyurea significantly alters blood pressure and heart rate and produces significant uterine vasoconstriction. The resulting reductions in uterine blood flow (77%) elicited by hydroxyurea may be associated with its immediate embryotoxicity.

Abnormalities, Drug-Induced↗

PubMed1981

Comparative ultrastructural alterations in rabbit limb-buds after a teratogenic dose of either hydroxyurea or methotrexate.

Early changes in rabbit limb-bud fine structure subsequent to maternal administration of either hydroxyurea (750 mg HU/kg) or methotrexate (19.2 mg MTX/kg) on gestational day 12 have been analyzed in order to identify the morphologic sites of teratogenic action. Forelimb-buds were examined at 15 minutes to 32 hours posttreatment for ultrastructural alterations. HU caused early dispersion of ribosomes, condensation of nuclei, segregation of the granular portion of the nucleoli, and eventual fragmentation of mesenchymal cells. As a consequence of the extensive mesenchymal cellular death, the intercellular space among the remaining viable cells was increased. Cellular debris from fragmented cells was seen phagocytized within cells and in the intercellular space. In contrast, MTX caused an increase in cytoplasmic lipid, angular contours of nuclei, but relatively little cellular death. The most prominent change was a disruption of the normal mesenchymal architecture characterized by greatly increased intercellular space and a consequent reduction in the number of intercellular junctions. Nearly normal cytoarchitecture was restored by 32 hours. It was concluded that the primary morphologic sites of action are indeed different. Nevertheless, MTX and HU shared a common denominator since both caused disruption of intercellular contacts and possible breakdown of intercellular communication: HU through cytolethality, and MTX via disruption of intercellular junctions. This latter phenomenon may help to explain the similarities in limb defects caused by these two drugs.

Animals↗

PubMed1981

Amelioration of teratogenesis. I. Modification of hydroxyurea-induced teratogenesis by the antioxidant propyl gallate.

Hydroxyurea (HU) is a potent teratogen which caused 100% embryotoxic effects in New Zealand white rabbits when injected sc on gestational day 12. These included a high percentage of resorptions and severe craniofacial, trunk and limb deformities of all survivors. Co-treatment of pregnant animals with the phenolic antioxidant propyl gallate (PG) resulted in amelioration of the embryotoxicity. Various amounts of PG (362-906 mg/kg) and HU (600-750 mg/kg) were eigher injected simultaneously or mixed together for periods of time up to 45 min. The extent of amelioration was dependent upon the amount of PG, although the highest dose of PG caused maternal toxicity. Simultaneous injections of HU and PG were not as efficacious as mixture of the two chemicals prior to injection. The length of time which the HU and PG mixture was allowed to stand prior to injection had no effect on the extent of amelioration. The protective action of PG resulted in significant linear reductions in both resorptions and specific malformations with increasing doses of PG. Histologic analysis of HU and HU-PG embryos disclosed that HU produced rapid cell death in the mesenchymal compartment of the embryo, particularly in the limb-buds, beginning at 2 h after treatment. Cell debris increased in amount until 8 h and remained extensive at 16 h. In contrast, HU-PG delayed the onset for cell death until 8 h. Nevertheless, at 16 h, the amount of cell debris in the limb-buds was appreciable. Thin layer chromatography (TLC) of HU-PG solution revealed no breakdown products or intermediate compounds suggesting that HU and PG do not react chemically. The presence of HU within both HU and HU-PG treated embryos was confirmed by TLC of embryonic sonicants. In contrast, TLC of embryonic extracts revealed PG only in HU-PG embryos. Light microscopy of other embryos from those same litters demonstrated extensive cell debris in the HU embryos but not in HU-PG embryos. It is suggested that the delay in onset of HU cytotoxicity is caused by the antioxidant properties of PG acting within the embryos, and that this may account for the amelioration of HU teratogenesis by PG.

Abnormalities, Drug-Induced↗

PubMed1981

Comparative studies on acetazolamide teratogenesis in pregnant rats, rabbits, and rhesus monkeys.

Acetazolamide produces a characteristic forelimb reduction deformity when administered to pregnant rodents. Past studies indicated that non-rodent species (rabbit and monkey) are resistant to this effect. The present studies confirmed this fact and demonstrated that transport of acetazolamide into the rabbit embryo was similar to that in sensitive rat embryos. In monkeys, however, the concentrations of acetazolamide within maternal plasma and embryo were much lower than in rats. Carbonic anhydrase activity was also measured since inhibition of this enzyme is the primary pharmacologic effect of acetazolamide. Again the rabbit embryo had carbonic anhydrase specific activity levels similar to that of the rat. Monkey embryos, on the other hand, contained negligible levels of enzyme activity during the presumed sensitive period of development. Thus the resistance of monkey embryos to acetazolamide teratogenesis may be due to low carbonic anhydrase activity and/or the small amount of drug reaching the embryo. No basis for the resistance of rabbit embryos to acetazolamide teratogenesis was uncovered.

Acetazolamide↗

PubMed1980

Cardiovascular alterations in rabbit embryos in situ after a teratogenic dose of hydroxyurea: an in vivo microscopic study.

The early cardiovascular (CV) responses of New Zealand white rabbit embryos in situ subsequent to maternal SC injection with hydroxyurea (HU) were analyzed by in vivo microscopic methods. Laparotomies were performed on gestational day 12, and the gravid uteri were exteriorized. The embryos were exposed by careful incisions of the uterine wall and reflection of the extraembryonic membranes. Temperature, water, and electrolyte homeostasis were maintained throughout all procedures. Maternal injection with HU at a teratogenic level (750 mg HU/kg) caused alterations in the embryonic CV system as early as 2 minutes post-treatment. Typically, within 4 minutes the embryonic craniofacial region responded with dilations of the anterior cardinal vein (ACV) and its tributaries. The ensuing pathological events included petechial hemorrhages and hematomas in the forebrain, postocular region, mandibular and nasal processes, and apparent collapse of the vasculature in the forelimb bud. Many embryos exhibited pericardial hemorrhage within 9 minutes. The most severely affected embryos displayed cardiac tamponade and stasis of blood flow through the cardiac chambers. In contrast, control embryos, which received either no drug treatment of SC injection of saline at various osmolarities and pH's, demonstrated none of the CV changes reported above, even after 120 minutes. Low doses of HU (500 mg/kg) produced only ACV dilations in some embryos by 30 minutes. Histologic analysis of HU embryos confirmed the in vivo microscopic observations. The drastic CV derangements exhibited by many embryos may be one of the causes for the high resorption rates associated with the treatment. Furthermore, since teratogenic doses of HU produce immediate hemorrhages and hematomas in the embryos in the same craniofacial areas which are later deformed in the term fetus, it is possible that the teratogenic action of this drug may be related to the initial vascular embryopathies.

Animals↗

PubMed1980

Differential embryonic cardiovascular responses to acute maternal uterine ischemia: an in vivo microscopic study of rabbit embryos with either intact or clamped umbilical cords.

The effects of acute episodes of maternal uterine ischemia on the cardiovascular system of New Zealand white rabbit embryos were studied by in vivo microscopic methods. On gestational day 12, gravid uteri were surgically externalized, and the walls of the implantation sites were carefully incised and reflected to reveal the embryos. Throughout all procedures, temperature, water, and electrolyte homeostasis were preserved. The embryos within each litter were divided into two groups: 1) two randomly selected embryos whose umbilical cords were clamped, and 2) the remaining embryos of the litter whose umbilical cords were uncompromised. Uterine ischemia was induced by clamping all uterine arterial and venous channels. Occlusion of the maternal uterine vessels produced severe uterine cyanosis within 1-2 min. The embryos whose umbilical cords were not clamped exhibited severe cardiovascular derangements beginning within 3-4 min. In contrast, the embryos whose umbilical cords were clamped (thereby interrupting both umbilical and vitelline circulations) had no observable cardiovascular alterations. The absence of effects in embryos with clamped umbilical cords suggests that acute episodes of hypoxia are well tolerated by young embryos. In contrast, the rapid appearance of cardiovascular derangements after interruption of maternal uterine circulation in embryos with unclamped umbilical cords emphasizes the idea that even brief intervals of uterine ischemia are deleterious to the rabbit embryo.

Animals↗

PubMed1979

Lectin teratogenesis: defects produced by concanavalin A in fetal rabbits.

Concanavalin A (con A) is teratogenic to rabbit embryos during gestational days 12--15. Intracoelomic injections of 40 microliter con A solution (4 microgram/microliter) were performed on rabbit embryos during gestational days 10--15. Control embryos received either 40 microliter of saline, sham injection or no treatment. Con A caused increased fetal resorptions on days 10 and 11, but malformation levels did not differ from controls. On days 12--15, con A produced craniofacial, trunk and limb anomalies. The highest percentage of malformation occurred on day 14. The defects were classified into four groups: (1) malformations of limbs including paw and digital dysplasias as well as fusions of the limbs to the head or body wall; (2) "closure" defects such as umbilical hernia, encephalocoele, exencephaly or ectopia cordis; (3) "contracture" defects such as club paws, extended knees, or clenched digits, which exhibited normal osseous and cartilaginous skeletons; and (4) miscellaneous, non-specific anomalies including fused or dysplastic sternebrae or ribs. Histologic analysis of selected 12-day embryos 4 to 18 hours post-injection was performed to ascertain potential sites of teratogenic action. At 12 hours ectodermal necrosis was observed in the limb buds adjacent to the apical ectodermal ridge. By 18 hours, the ectoderm had eroded, exposing the basal lamina to the amniotic fluid. Focal areas of mesenchymal necrosis were observed in association with the ectodermal erosion. The potential roles of amniocentesis and limb bud repair in the genesis of the malformations are discussed.

Abnormalities, Drug-Induced↗

PubMed1979

Cell death and free radicals: a mechanism for hydroxyurea teratogenesis.

Hydroxyurea is a drug which causes birth defects in a variety of animals. Its pharmacologic actions include rapid killing of proliferating cells and profound inhibition of the synthesis of DNA. The mechanism whereby hydroxyurea produces teratogenesis is unresolved although it is related to the pharmacologic actions. Careful reading of the scientific literature discloses several putative mechanisms for the teratogenic action of hydroxyurea, which account for the inhibited synthesis of DNA, but do not explain the rapid onset of cell death. This paper presents a hypothesis that hydroxyurea causes rapid cell death through the initiation of uncontrolled free radical chain reactions. In vitro biochemical experiments have demonstrated the ability of compounds containing a hydroxylamine group (such as hydroxyurea) to form H2O2 and intermediate free radicals in biological fluids. Free radicals propagate themselves through chain reactions and can react swiftly and indiscriminately with the macromolecules quickly by inactivating enzymes, cross-linking DNA, and altering membrane functions through lipid auto-oxidation. Preliminary experiments utilizing an antioxidant to counteract the free radical effects appear to support the hypothesis that the rapid cell death is caused by aberrant free radical reactions.

Animals↗

PubMed1977

Drug-induced limb dysplasias in fetal rabbits.

Pregnant New Zealand White rabbits were treated on gestation day 12 with 19.2 mg/kg methotrexate (MTX), 750 mg/kg hydroxyurea (HU), or 1,500 mg/kg acetazolamide. Rabbits were killed either 2-32 hours posttreatment for histological analysis of embryos or at day 29 for gross and skeletal examination of fetuses. tmtx produced cleft palate, hydrocephalus, and fore- and hindlimb reduction defects. Histological analysis revealed pyknosis and edema in mesenchymal tissues at four to eight hours following treatment. The apical ectodermal ridges (AER) of treated embryos permanently lost their characteristic pseudostratified organization. By 32 hours the limb buds had regained their normal appearance except for the AER. HU affected all fetuses with skull and facial anomalies as well as severe reduction deformities of all limbs. Histologically HU-treated embryos had numerous, basophilic, intercellular granules (presumably cell debris) which appeared within two to four hours in the limb bud mesenchyme, neural tube, and dorsal root ganglion. The architecture of the AER was unchanged. Acetazolamide produced bilateral retarded ossification or possible aplasia of the first metacarpal and talus in nearly 80% of fetuses. Microscopic examination disclosed no apparent alterations in limb-bud morphology. Methyl green-pyronin Y staining called attention to green intracellular droplets within the endoderm of the trachea and bronchi at two hours posttreatment. It was concluded that the three drugs do not produce limb dysplasias by a common teratogenic mechanism.

Abnormalities, Drug-Induced↗

PubMedDate not supplied

Bendectin.

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Abnormalities, Drug-Induced↗

PubMedDate not supplied

An assessment of the developmental toxicity of inorganic arsenic.

A critical analysis of the literature base regarding the reproductive and developmental toxicity of arsenic compounds, with emphasis on inorganic arsenicals, was conducted. The analysis was stimulated by the great number of papers that have purported to have shown an association between exposure of pregnant laboratory animals to arsenic compounds and the occurrence of offspring with cranial neural tube defects, particularly exencephaly. For the most part, the literature reports of arsenic developmental toxicity in experimental animals are inadequate for human risk assessment purposes. Despite the shortcomings of the experimental database, several conclusions are readily apparent when the animal studies are viewed collectively. First, cranial neural tube defects are induced in rodents only when arsenic exposure has occurred early in gestation (on Days 7 [hamster, mouse], 8 [mouse], or 9 [rat]). Second, arsenic exposures that cause cranial neural tube defects are single doses that are so high as to be lethal (or nearly so) to the pregnant animal. Third, the effective routes of exposure are by injection directly into the venous system or the peritoneal cavity; even massive oral exposures do not cause increases in the incidence of total gross malformations. Fourth, repetition of similar study designs employing exaggerated parenteral doses is the source of the large number of papers reporting neural tube defects associated with prenatal arsenic exposure. Fifth, in five repeated dose studies carried out following EPA Guidelines for assessing developmental toxicity, arsenic was not teratogenic in rats (AsIII, 101 micromol/kg/d, oral gavage; 101 micromol/m3, inhalation), mice (AsV, 338 micromol/kg/d, oral gavage; est. 402 micromol/kg/d, diet), or rabbits (AsV, 21 micromol/kg/d, oral gavage). Data regarding arsenic exposure and adverse outcomes of pregnancy in humans are limited to several ecologic epidemiology studies of drinking water, airborne dusts, and smelter environs. These studies failed to (1) obtain accurate measurements of maternal exposure during the critical period of organogenesis and (2) control for recognized confounders. The lone study that examined maternal arsenic exposure during pregnancy and the presence of neural tube defects in progeny failed to confirm a relationship between the two. It is concluded that under environmentally relevant exposure scenarios (e.g., 100 ppm in soil), inorganic arsenic is unlikely to pose a risk to pregnant women and their offspring.

Abnormalities, Drug-Induced↗