The teratogenic potential of alkoxy acids in post-implantation rat embryo culture: structure-activity relationships

Alkoxy acids are the active metabolites of teratogenic glycol ethers. To examine the relationship of chemical structure to embryotoxicity, the effects of 6 acids on the development of 9.5-day rat embryos over 48 h in culture were studied. Methoxyacetic acid (MAA) and ethoxyacetic acid (EAA) (5 mM) were growth-retarding and induced gross structural defects, with MAA being more effective. n-Propoxyacetic acid (n-PAA) and n-butoxyacetic acid (n-BAA) (5 mM) were markedly less embryotoxic and produced only minor anomalies. Thus, the activities of these substituted acetic acids decreased with the increase in the length of the alkoxy chain. 3-Methoxypropionic acid (3-MPA) and 4-methoxybutyric acid (4-MBA) (5 mM) were much less active than MAA and induced only minor defects. Therefore in this series: RO(CH2)nCOOH, an increase in the value of n caused a greater reduction in embryotoxicity than did an increase in chain length of the alkyl group R.

12-O-Tetradecanoyl-phorbol-13-acetate (TPA) induced congenital kidney defects and embryomortality in the CD-1 mouse

CD-1 Mice were treated with daily intraperitoneal injections of 10 or 100 micrograms/kg 12-O-tetradecanoyl-phorbol-13-acetate (TPA) on pregnancy days 8, 9 and 10 or 11, 12 and 13 (early and late organogenesis). By the same regimen, the LD50 for TPA was about 450 micrograms/kg. TPA treatment induced embryomortality, fetal malformation and reduced fetal weight, generally in a dose-related manner. TPA treatment (100 micrograms/kg) was markedly more embryolethal on days 11-15 (68%/litter) than in early organogenesis (18%/litter). Renal malformations were observed in all treatment groups at a low incidence (about 5% of live fetuses) and in no case was the total incidence of malformations greater than 10%. There was little correlation between indications of maternal toxicity and the adverse outcomes of pregnancy, suggesting that TPA has direct embryotoxic effects. The relatively low incidence of anomalies is considered a paradox in light of the potent effects of TPA on cellular processes critical to embryogenesis.

Comparative effects of cathepsin inhibitors on rat embryonic development in vitro. Evidence that cathepsin D is unimportant in the proteolytic function of yolk sac

The effects of two proteinase inhibitors, leupeptin and pepstatin on the development of 9.5-day rat conceptuses in vitro has been studied. All cultures were of 48 h duration and the inhibitors were present throughout the entire period. When pepstatin was added to the culture medium (5-25 micrograms/ml) conceptuses developed and grew to an extent that did not differ from untreated controls. However, leupeptin (1-4 micrograms/ml) caused severe growth retardation and abnormal development of conceptuses. The effects of the two inhibitors on the hydrolysis of 125I-labelled BSA and haemoglobin by homogenates of 10.5-day yolk sac indicated the biochemical basis for the differential toxic effects of the two inhibitors on development. Leupeptin was highly inhibitory of the degration of both substrates whereas pepstatin caused no inhibition of 125I-labelled BSA hydrolysis, and only a slight inhibition of haemoglobin hydrolysis. These observations demonstrate that cathepsin D, a lysosomal aspartic proteinase that is specifically inhibited by pepstatin is not involved in yolk-sac-mediated protein utilization by early organogenesis-phase conceptuses and that lysosomal cysteine proteinases, specifically inhibited by leupeptin, are of paramount importance in this yolk sac function.

Comparative effects of cathepsin inhibitors on rat embryonic development in vitro. Evidence that cathepsin D is unimportant in the proteolytic function of yolk sac

The effects of two proteinase inhibitors, leupeptin and pepstatin on the development of 9·5-day rat conceptuses in vitro has been studied. All cultures were of 48 h duration and the inhibitors were present throughout the entire period. When pepstatin was added to the culture medium (5–25 μg/ml) conceptuses developed and grew to an extent that did not differ from untreated controls. However, leupeptin (l–4 μg/ml) caused severe growth retardation and abnormal development of conceptuses.

The effects of the two inhibitors on the hydrolysis of 125I-labelled BSA and haemoglobin by homogenates of 10·5-day yolk sac indicated the biochemical basis for the differential toxic effects of the two inhibitors on development. Leupeptin was highly inhibitory of the degration of both substrates whereas pepstatin caused no inhibition of 125I-labelled BSA hydrolysis, and only a slight inhibition of haemoglobin hydrolysis.

These observations demonstrate that cathepsin D, a lysosomal aspartic proteinase that is specifically inhibited by pepstatin is not involved in yolk-sac-mediated protein utilization by early organogenesis-phase conceptuses and that lysosomal cysteine proteinases, specifically inhibited by leupeptin, are of paramount importance in this yolk sac function.

The teratogenicity of methoxyacetic acid in the rat

Intraperitoneal (i.p.) administration of methoxyacetic acid (MAA) to rats on Day 8, 10, 12 or 14 of pregnancy was embryolethal and teratogenic. Skeletal anomalies, hydrocephalus and dilatation of the kidney pelvis were the most common malformations. Embryonic response to MAA varied with gestational age and with dosage (0.1 to 2.5 mmol/kg). These actions are similar to those previously reported for 2-methoxyethanol (ME) and dimethoxyethyl phthalate (DMEP). Embryos were also examined on Day 12, 48 h following i.p. administration of 2.5 mmol/kg MAA. Abnormalities were comparable to those previously observed following MAA treatment of rat conceptuses in culture. These data support the conclusion that MAA is the proximal teratogenic metabolite of ME and DMEP.

Effects of dimethoxyethyl phthalate, monomethoxyethyl phthalate, 2-methoxyethanol and methoxyacetic acid on post implantation rat embryos in culture

The secondary metabolite of dimethoxyethyl phthalate (DMEP), methoxyacetic acid (MAA), but neither the diester nor either of its primary metabolites, monomethoxyethyl phthalate (MMEP) and 2-methoxyethanol (ME), interferes with normal growth and development of organogenesis phase rat embryos in culture. These in vitro observations suggest that the teratogenicity of DMEP in vivo is due to enzymic cleavage of the diester to ME, followed by oxidation of the latter to MAA in the maternal compartment.

Tumor promoter actions on rat embryonic development in culture

The many embryonic and developmental features associated with tumor promotion have prompted us to investigate the effects of a series of phorbol esters and related diterpene tumor promoters on mammalian embryogenesis. A culture system which supports the normal development of 10.4 day organogenesis-phase rat conceptuses was utilized. In this system, 12-O-tetradecanoylphorbol-13-acetate (TPA), a potent Stage I and II promoter, disrupted the morphology and function of the embryonic visceral yolk sac (dose required to affect 50% of conceptuses, 18 nM). The effect was characterized by an abnormal, progressive separation of the two cellular layers of the yolk sac, but cellular differentiation appeared to be uninterrupted. Parallel log dose-response lines for this effect were produced by phorbol-12,13-dibenzoate (dose required to affect 50% of conceptuses, 200 nM) and phorbol-12,13-diacetate (dose required to affect 50% of conceptuses, 300 nM) which are consistent with structure-activity relationships for other promotional actions of these compounds. In addition, the weak Stage I promoter, 4-O-methyl-12-O-tetradecanoylphorbol-13-acetate, produced identical effects but was 1400 times less potent than was TPA, while mezerein, a potent Stage II promoter, was as potent as was TPA. These observations support the hypothesis that embryonic cells may be differentially sensitive to early- and late-stage promoters. Ethylphenylpropiolate, a nonpromoting hyperplastic agent in mouse skin, had no effect on yolk sac morphology or function at its maximum solubility (1.85 mM). Yolk sac disruption by TPA was potentiated by heat inactivation (56 degrees, 30 min) or 0.45-micron filtration of the culture medium. A more advanced stage of yolk sac development was less sensitive to TPA disruption since 11.4 day conceptuses, which were cultured for 30 hr, developed identical lesions, but TPA was at least 5-fold less potent. Thus, the tumor promoter-induced lesions of the rat yolk sac have some features consistent with late-stage tumor promotion and do not appear to be associated with general toxicity, hyperplasia, or alterations in cellular differentiation. We postulate that rat conceptuses maintained in vitro may provide an important model system for the study of the proposed mechanisms involved in chemical tumor promotion.

12-O-tetradecanoylphorbol-13-acetate actions on macromolecular synthesis, ornithine decarboxylase, and cellular differentiation of the rat embryonic visceral yolk sac in culture

We have reported previously that 12-O-tetradecanoylphorbol-13-acetate (TPA) disrupts the morphology and functional development of the rat embryonic visceral yolk sac (VYS) maintained in a whole-embryo culture system. The TPA-mediated disruption of the VYS is characterized by the abnormal progressive separation of the cellular layers that comprise the VYS and appears to be related to late-stage promotion. The present study further characterizes this effect of TPA on the VYS of rat conceptuses in vitro. VYS ornithine decarboxylase levels were not induced but rather were initially depressed by TPA treatment. There was no major effect of TPA treatment on VYS hemoglobin content, as measured by absorbance at 414 nm and polyacrylamide gel electrophoresis. Changes in VYS hemoglobin synthesis during the culture period, measured by [14C]leucine incorporation with subsequent autoradiography, was likewise not a major effect of TPA treatment. VYS DNA synthesis and VYS RNA synthesis, measured by [3H]thymidine and [3H]uridine incorporation, respectively, were unchanged by TPA treatment. VYS protein synthesis, measured by [3H]leucine incorporation, was initially increased by TPA treatment but returned to control values by the end of the culture period. This increase in [3H]leucine incorporation was not due to a TPA-mediated change in the secretory function of the VYS. The data suggest that the tumor promoter-induced disruption of the VYS is not associated with cellular proliferation, ornithine decarboxylase induction, or alterations in differentiation. Effects on the cell surface, altering cell-cell interactions and/or communication might best explain these actions of TPA.

Evaluation of a human hepatoma cell line as a target cell in genetic toxicology

A cell line derived from a human hepatoblastoma, HepG2, was examined for its ability to activate cyclophosphamide (CY) to a genotoxic form. Metabolism of CY to genotoxic product(s) was determined by the induction of sister-chromatid exchanges (SCE). The dose-dependent response pattern in HepG2 was compared to the patterns obtained by three other mammalian cell lines. HepG2 and a rat hepatoma cell line, H4-II-E, show similar dose-dependent increases of induced SCE, whereas non-hepatic-derived fibroblast lines show little or no CY-induced SCE. Microsomal enzyme activities characteristic of cytochromes P450 and P448 and epoxide hydrolase were examined in the two hepatoma cell lines and compared to levels in rat liver microsomal preparations. Although no cultured cell line can be a universal surrogate for in vivo metabolism, we propose that HepG2 may be useful to determine in a qualitative manner whether human cells possess the ability to activate a chemical to a genetically damaging form.

Chain length dependency of fatty acid and carbamate binding to serum albumin

The binding interactions of bovine serum albumin (BSA) with the unbranched fatty acids (FA) pentanoate (five-carbon chain length: C5) up to nonanoate (C9), and the carbamates n-methyl carbamate (equivalent to C3) up to n-hexyl carbamate (equivalent to C8) were examined using an ultrafiltration technique. A single, high-affinity site was observed for each of the FA, with an increasing number of secondary sites with increasing chain length. From binding affinity and competition data, there appear to be distinct albumin sites for the short-chain (less than or equal to C7) and the medium-chain (greater than or equal to C8) FA. Published data suggest that the medium-chain FA site is one of the major drug-binding sites on human serum albumin (HSA) or BSA, the indole/benzodiazepine site. Competition between the FA and warfarin for BSA or HSA binding was studied by ultrafiltration and fluorescence methods and suggests that the short-chain FA site may lie in the same region as a second major drug-binding site, the large warfarin-binding area. Thermodynamic parameters of the FA-BSA interactions are suggestive of primary binding being a combination of electrostatic and hydrophobic binding and secondary binding being purely hydrophobic in nature. Carbamate interactions with BSA show several primary sites and also suggest a disparity between the binding of ligands of less than or equal to 7 and greater than or equal to 8 in total length, but there was no evidence of competition between FA and carbamates. A model is proposed to explain these observations, which includes the suggestion that several classes of hydrophobic binding areas exist, each of which is specific for ligands of a restricted range of chain lengths.

Developmental patterns of ornithine decarboxylase activity in organogenesis phase rat embryos in culture and in utero

Ornithine decarboxylase activity was measured during organogenesis in rat embryos grown in utero and whole rat conceptuses maintained in an in vitro culture system. Ornithine decarboxylase levels in vivo showed a distinct peak at embryonic age 10.5 d. Despite identical morphology, protein content, crown rump length and numbers of somites cultured embryos displayed a different developmental pattern and possessed less than half the ODC activity of that in vivo. The data suggest that the normal embryonic programming of ODC activity is significantly altered by the culture environment and that further biochemical comparisons of embryos growing in utero and in vitro may be required to evaluate properly the applicability of this technique to detailed studies of teratogenesis and developmental biology.

The relative teratogenic index and teratogenic potency: proposed components of developmental toxicity risk assessment

Teratogenicity tests should provide answers to three questions: (1) Can the agent induce developmental defects? ("teratogenic potential"); (2) What are the effective doses? ("teratogenic potency"); and (3) Are effective doses below adult toxic doses? ("teratogenic hazard"). The answers to (2) and (3) should be quantitative in nature, but there are no accepted parameters to express these properties. In this paper we propose parameters for the description of teratogenic potency and hazard in quantitative terms. Derivation and calculation of the parameters are illustrated by the analysis of adult lethality and teratogenicity data of eight structurally related anhydrides and imides, following testing in the CD-1 mouse. Teratogenicity was evaluated following treatment on Days 8-10 of gestation, using an average of four dose groups per compound and at least 10 dams per group. Adult lethality was estimated following a similar 3-day dosage schedule with an average of 6 dose groups per compound and at least 8 animals per group. Dose-response relationships of teratogenicity were fitted to a probit model from which tD50 (median effective dose), and other effective doses were computed. It is proposed that tD05, as a minimum teratogenic dose, best represents teratogenic potency. In this study, potency ranged from 0.17 mmol/kg/day for phenytoin to 5.2 mmol/kg/day for ethosuximide. In order to measure teratogenic hazard a ratio between adult toxic (lethality was chosen as the most appropriate measure) and teratogenic responses was made. Since the dose-response slopes of lethality and teratogenicity were different, a simple ratio between median effective doses could not be used. It is shown that a ratio of LD01 to tD05 provides a "Relative Teratogenic Index" (RTI) which reflects the teratogenic hazard of a test agent. The following RTI values (LD01/tD05) were computed in this study: phthalic anhydride, 0.9; phensuximide, 1.0; succinic anhydride, 1.0; ethosuximide, 1.2; phenytoin, 1.6; phenacemide, 3.3; trimethadione, 4.0; and sodium valproate, 4.1. For these data, tD05 and RTI clearly represent the differing teratogenic potencies and hazards of the tested compounds. it is suggested that these parameters may be useful in comparative teratogenicity studies and may be valuable components of developmental toxicity risk assessment.

Immunoglobulin expression by human B lymphocytes clonally transformed by Epstein Barr virus

Epstein Barr virus (EBV) immortalizes human B lymphocytes, resulting in long-term lymphoblastoid cell lines. To date, such cell lines have typically been derived by suspension culture of mixed mononuclear cells, infected in vivo or in vitro with EBV. We have derived 208 lymphoblastoid lines by clonal transformation of peripheral blood lymphocytes from 3 neonates, 3 normal adults, and 1 patient with systemic lupus erythematosus (SLE), utilizing colony formation in agarose and then separate propagation of the colonies in liquid medium. A total of 180 lines have been analyzed for expression of cytoplasmic and/or secreted immunoglobulin isotypes. Such analysis reveals that 167 (92%) of the lines are monoclonal with respect to isotype expression. All clonally derived lines from neonates produce only IgM. Most clonal transformants from normal adults also produce IgM (81%), but clones producing IgG (16%) or IgA (3%) were also found. Clonal transformation of lymphocytes from the SLE patient revealed a shift in isotype expression, with increased numbers of IgG-secreting clones (48%) and IgA-secreting clones (13%). The data support the use of EBV-mediated clonal transformation as a probe for the analysis of states of isotype differentiation among circulating B cells, and as a method for deriving immortalized, monoclonal human B cell lines.

Prospects for human monoclonal antibodies: a critical perspective

Monoclonal antibodies have proved useful in detecting antigenic variation at single determinant sites on complex antigens, a fact which seems to have engendered a common misperception that a monoclonal antibody is necessarily a "monospecific" agent. Yet there exists considerable evidence that individual antibody molecules are multispecific in their binding capabilities, and that the amount of functional and genetic redundancy in mammalian immune systems may be quite large. The implications of this data for the future of monoclonal antibodies are emphasized, along with a brief review of present progress toward human monoclonal antibodies.

Immunoglobulin expression by human B lymphocytes clonally transformed by Epstein Barr virus

Epstein Barr virus (EBV) immortalizes human B lymphocytes, resulting in long-term lymphoblastoid cell lines. To date, such cell lines have typically been derived by suspension culture of mixed mononuclear cells, infected in vivo or in vitro with EBV. We have derived 208 lymphoblastoid lines by clonal transformation of peripheral blood lymphocytes from 3 neonates, 3 normal adults, and 1 patient with systemic lupus erythematosus (SLE), utilizing colony formation in agarose and then separate propagation of the colonies in liquid medium. A total of 180 lines have been analyzed for expression of cytoplasmic and/or secreted immunoglobulin isotypes. Such analysis reveals that 167 (92%) of the lines are monoclonal with respect to isotype expression. All clonally derived lines from neonates produce only IgM. Most clonal transformants from normal adults also produce IgM (81%), but clones producing IgG (16%) or IgA (3%) were also found. Clonal transformation of lymphocytes from the SLE patient revealed a shift in isotype expression, with increased numbers of IgG-secreting clones (48%) and IgA-secreting clones (13%). The data support the use of EBV-mediated clonal transformation as a probe for the analysis of states of isotype differentiation among circulating B cells, and as a method for deriving immortalized, monoclonal human B cell lines.

Quantitation of rat embryonic development in vitro: a morphological scoring system

In order to realize the maximum potential of whole-embryo culture techniques, definitive parameters must be developed for the quantitative estimation of embryonic growth and development. An objective scoring system has been devised which provides a precise measure of morphological development. Examination of rat conceptuses from dams on pregnancy days 10, 11, 12, and 13 (sperm positive = day 1) led to the selection of 17 morphological features for use in the system. Up to six developmental stages of each feature were defined and assigned scores of 0 to 5. The numerical total of scores for an individual embryo is taken as the overall morphological score (MS). The system was applied prospectively to 103 Sprague-Dawley rat conceptuses aged 9 to 12.7 days (0 = time of copulation). The variation of score with embryonic age (EA, days) was highly linear: MS = 202.28 + 20.932 EA (R2 = 0.991). Thus, the morphological score can be used to compute apparent embryonic age, and the calculated standard error of prediction is +/- 2.2 hrs. The number of somites (SN) was also found to vary linearly with age over this period: SN = -126.23 + 13.217 EA (R2 = 0.982), and could be used to estimate development. However, the standard error for prediction of apparent embryonic age is greater (+/- 3.1 hours) than that for morphological score, and this single feature will not necessarily reflect overall development. Several parameters were examined as estimates of embryonic growth, as distinct from development. Yolk sac diameter, crown-rump length, and head length were found to vary with EA as quadratic functions over this time. Total embryonic protein increased logarithmically with EA and was considered to be the most suitable measure of embryonic growth. Use of the morphological scoring system in embryo culture experiments provides a precise index of embryonic development, aids the detection of retardation or dysmorphogenesis of specific primordia, and allows a quantitative comparison of development and growth.

Gram-negative sepsis in neonates: a nursery outbreak due to hand carriage of Citrobacter diversus

An outbreak of Citrobacter diversus infections occurred in a newborn nursery at a 350-bed community hospital during September and October 1978. Two infants developed sepsis and meningitis and nine additional infants had asymptomatic umbilical colonization. These infants did not differ from control, noncolonized infants with respect to numerous clinical and environmental variables. Surveillance cultures failed to implicate an environmental source for the Citrobacter. However, cultures of nursery personnel identified a hand-carrier whose removal eliminated neonatal colonization with C diversus and decreased the number of isolates of certain other enteric bacteria found on umbilical stumps. Factors implicated in the perpetuation of the carrier state in this nurse included marked dermatitis from repeated hand washing and hand care practices involving the overnight use of plastic gloves and nutritive hand cream. The mode of transmission within the nursery appeared to be from nurse's hands to infant's umbilicus. Use of triple dye on umbilical stumps and chlorhexidine hand washing preparations did not eliminate this cycle. Surgical manipulation of colonized umbilical stumps may have been responsible for illness in two infants.

Ethanol embryotoxicity: direct effects on mammalian embryos in vitro

Exposure to ethanol retards growth and differentiation in cultured rat embryos during organogenesis. The development of untreated embryos is indistinguishable from growth in utero. These data suggest that the hypoplastic features of children born to chronically alcoholic mothers are due, at least in part, to a direct action of ethanol, which causes reduced embryonic cellular proliferation early in gestation.

Binding of coumarin anticoagulants to human and bovine serum albumin. Circular dichroism studies

The interaction of acenocoumarin, coumachlor, phenprocoumon, and warfarin with human and bovine serum albumin was investigated by ultracentrifugation and circular dichroism measurements. Although all four drugs generate extrinsic Cotton effects when bound to human and bovine serum albumin, large differences in the signs and the intensities of the Cotton effects are observed. The differences in the induced Cotton effects suggest differential molecular binding mechanisms.

Response of the human eye to laser irradiation of the iris

Irradiation of the iris of glaucoma patients with either a ruby or an argon laser caused no obvious disruption of the blood-aqueous barrier (as visualised by fluorescein angiography), in contrast to a sudden and pronounced effect in the rabbit eye. Only a low and variable increase in intraocular pressure occurred in the human subjects after the laser irradiation in comparison with a consistently high rise of ocular tension in the rabbit. This investigation indicates that the human eye is much less responsive to injury.

Effect of pilocarpine on visual acuity and on the dimensions of the cornea and anterior chamber

The effect of pilocarpine on visual acuity and on the dimensions of the cornea, anterior chamber, and lens were studied in two groups of subjects. Significant changes in ocular tension, corneal curvature, anterior chamber depth, and lens anterior radius were found in a group of 55 glaucomatous eyes as a result of pilocarpine treatment, but there was no change in corneal thickness. Out of 102 glaucomatous eyes 78 became relatively myopic, and this appears to be due to changes in the dimensions of the lens of the eye similar to those occurring in accommodation, as a result of the effect of the drug on the ciliary muscle. The effect of pilocarpine on anterior chamber depth, area, and volume was studied in 125 eyes using a photographic method, and a significant reduction in the dimensions of the anterior chamber was observed as a result of the administration of pilocarpine. A significant correlation between depth and volume was also noted and the implications of this are discussed.

Superficial lines and associated disorders of the cornea

In a clinical classification of fine superficial corneal lines, we recognized five major types of line: mare's tail lines, fibrillary lines, fingerprint lines, lacunar dystrophy or map-like changes, and tram lines. The fingerprint lines were further classified into several subgroups. There was a relationship between certain lines, in particular, fingerprint lines and lacunar dystrophy or map-like change with the occurrence of Cogan's microcystic dystrophy and recurrent erosion.

Haemoglobin catabolism: the role of ferrihaems in studies of the degradation pathway

The importance of ferrihaem aggregation in studies of haemoglobin catabolism is assessed in the light of recent work. Experimental evidence is put forward suggesting that monomeric ferrihaems are degraded much more readily than dimeric species. This may offer an alternative explanation for the apparent ;apoprotein catalysis' recently observed.

Iridotomy with a ruby laser

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