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F Welsch

Publications and source records attributed to F Welsch.

At least 55 records · Page 3Linked to original sources
PubMed1986

Karyotype, growth, and cell cycle analysis of human embryonic palatal mesenchymal cells: relevance to the use of these cells in an in vitro teratogenicity screening assay.

Human embryonic palatal mesenchyme (HEPM) is an established cell line that is presently under investigation as an in vitro prescreening assay used to determine the teratogenic potential of chemicals. We describe here general growth characteristics, karyotype, and cell cycle analysis of these cells. HEPM cells had plating efficiencies of less than 95% and displayed notable contact growth inhibition following an exponential growth phase that lasted for approximately 6 days. These cells had the diploid karyotype of a female human embryo. The chromosomal complement showed no dramatic change between passage 5 and 14. Flow cytofluorometry analysis using bromodeoxyuridine (BrdU) pulse labeling and a direct immunofluorescence anti-BrdU FITC probe revealed that the total cell cycle transit time was approximately 22 hr: the duration of G1 was 12.2 hr, S was 6.1 hr, and G2-M lasted for 3.7 hr. The results indicate that HEPM cells met the criteria regarding karyotype stability that were assumed by the National Toxicology Program of the USA.

Bromodeoxyuridine↗
PubMed1985

Brain cholinergic, behavioral, and morphological development in rats exposed in utero to methylparathion.

The purpose of this study was to determine the effects of subchronic administration of the organophosphate methylparathion (MPTH) during gestation on behavior and development of brain cholinergic neurons in the offspring. Pregnant rats received daily po doses of MPTH from Day 6 through Day 20 of gestation at doses causing no (1.0 mg/kg) or minimal (1.5 mg/kg) visible signs of maternal toxicity. Acetylcholinesterase (AChE) and choline acetyltransferase (CAT) activities, and [3H]quinuclidinyl benzilate (QNB) binding to muscarinic receptors, were determined in several brain regions at 1, 7, 14, 21, and 28 days postnatal age and in maternal brain at Day 19 of gestation. Prenatal exposure to 1.5 mg MPTH/kg reduced AChE and increased CAT activity in all brain regions at each developmental period and in maternal brain. Similar exposure to 1.0 mg MPTH/kg caused a significant but smaller and less persistent reduction in AChE activity but no change in brain CAT activity of the offspring. Both doses of MPTH decreased the Bmax of 3H-QNB binding in maternal frontal cortex but did not alter the postnatal pattern of 3H-QNB binding. In parallel studies, prenatal exposure to MPTH did not affect a variety of behaviors. However, cage emergence, accommodated locomotor activity, and operant behavior in a mixed paradigm were impaired in rats exposed to 1.0 but not to 1.5 mg/kg MPTH. No morphological changes were observed in hippocampal or cerebellar tissue. Thus, subchronic prenatal exposure to MPTH altered postnatal development of cholinergic neurons and caused subtle alterations in selected behaviors of the offspring.

Acetylcholinesterase↗
PubMed1985

Effects of acute or chronic polychlorinated biphenyl ingestion on maternal metabolic homeostasis and on the manifestations of embryotoxicity caused by cyclophosphamide in mice.

Diets of mice contained Aroclor 1254 (PCBs; 0, 1, 10 or 100 ppm). Some groups ingested PCBs beginning on gestation day (gd) 6 (vaginal plug positive day = gd 0) and continuing throughout pregnancy (acute exposure). Others were put on PCBs 90 days before mating and continued (chronic exposure) until all animals were sacrificed on gd 18. None of the PCBs diets had adverse effects on offspring. Chronic ingestion of 100 ppm reduced the conception rate. All chronic and acute 100 ppm pregnant mice had significantly altered ratios of liver to body weight. The aim of the different pretreatment regimens was to affect to variable degrees metabolism of cyclophosphamide (CPA). Bioactivation in the dam's liver is a prerequisite for embryotoxic effects in mice. Two doses of CPA were selected that caused malformations in 21.6% (10 mg/kg) or 93.4% (16 mg/kg) of the fetuses when injected on gd 11. The interaction (enhancement, no effect, attenuation) between acute or chronic PCBs and CPA could thus be examined. Double stained fetal limbs and their bone lengths were evaluated. The observations were correlated with cytochrome P-450, the levels of which were elevated in all 100 ppm groups. The activities of enzymes coupled to this hemoprotein family were induced in maternal liver in an exposure mode and PCBs concentration-dependent manner. Body burdens of PCBs in dams and fetuses were related to diet levels in acutely, but not in chronically treated animals. Placental transfer of radioactivity from ring-labelled 14C-CPA, measured in control and 100 ppm chronic mice, was not significantly affected by PCBs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Developmental phase-specific and dose-related teratogenic effects of ethylene glycol monomethyl ether in CD-1 mice.

Several animal species have shown a teratogenic response to inhaled or ingested ethylene glycol monomethyl ether (EGME). The present study examined the developmental phase specificity and dose-response characteristics of EGME-induced embryotoxicity. Pregnant CD-1 mice (vaginal plug positive day = gestation Day [gd]0) received multiple or single doses of EGME by gavage between gd 7 and 14. Fetuses were examined on gd 18 for external and skeletal malformations. EGME was not maternally toxic after multiple doses of 250 mg/kg or a single administration of up to 500 mg/kg. EGME induced embryotoxicity as manifested by reduced gd 18 fetal weights and increased resorptions. The observed malformations were specifically related to the developmental stage at the time of exposure. Exencephaly resulted after EGME exposure between gd 7 to 10 whereas paw anomalies (syndactyly, oligodactyly, and stunted digit No. 1) predominated during later stages of development. Paw anomalies were maximal after administration on gd 11, and forepaws exhibited greater susceptibility than hindpaws. The no observed effect dose for the induction of digit malformations after a single administration of EGME on gd 11 was 100 mg/kg. At 175 mg EGME/kg digit anomalies were induced without any concurrent reduction in fetal body weight while at 250 mg/kg and above, digit anomalies occurred concurrently with reduced fetal body weight.

Abnormalities, Drug-Induced↗
PubMed1985

Placental transfer and developmental toxicity of 2,2',4,4',5,5'-hexabromobiphenyl in B6C3F1 mice.

The 2,2',4,4',5,5' congener of hexabromobiphenyl (HBB) is the major constituent (55%) of a polybrominated biphenyl mixture that accidentally entered the human food chain through livestock feed. The embryotoxicity of HBB in B6C3F1 conceptuses was examined by adding 0, 100, 300, 500, 750, or 1000 ppm of HBB to the diet of pregnant C57BL/6J mice impregnated by C3H males. The females consumed HBB feed from Gestation Day (gd) 6 through 15. Pregnancy rates of plug-positive mice were adversely affected at greater than 300 ppm HBB (0 ppm = 77%, 100 = 73%, 300 = 55%, 500 = 49%, 750 = 42%, 1000 = 33%). Some pregnant dams died at dosages of 750 ppm (2 of 8). Body weight gain among the 300-ppm dams was reduced only on gd 15, indicating maternal toxicity, but it was indistinguishable from controls on gd 17. In the conceptuses HBB caused cleft palate and a cystic lesion in the region of the cerebellum at concentrations greater than or equal to 300 ppm. The nature of the cystic abnormality observed grossly could not be accurately defined, but it was probably in the meninges and was not associated with the brain ventricular system. In some HBB-exposed fetuses there were minor abnormalities of brain development, which were probably indicative of developmental delay rather than direct toxic effects on differentiation of specific regions of the brain. Thus, HBB affected embryonal development adversely only at exposure concentrations which caused toxicity in dams.

Administration, Oral↗
PubMed1985

Effects of a teratogen on [3H]uridine nucleotide transfer between human embryonal cells and on gap junctions.

Intercellular communication (IC) mediated by gap junctions (gj) occurs during embryonal development and appears to be important for normal differentiation through the exchange of morphogenetic signalling substances. Disruption of IC by chemicals may induce abnormal development resulting from failed cell-cell interactions. It was established in the present study that genotypically normal human embryonal palate mesenchyme (HEPM) cells displayed IC in cell culture and that the transfer of [3H]uridine nucleotides was inhibited by the potent embryotoxin and teratogen 12-O-tetradecanoyl-phorbol-13-acetate (TPA). IC was mediated by gj which were revealed by freeze-fracture and electron microscopy. Quantitative morphometric analysis showed that inhibition of IC by TPA coincided with a significant reduction in the number of gj. The observations suggest that inhibition of IC by the teratogen TPA may be one among the many mechanisms believed to be responsible for the induction of abnormal development by chemical teratogens.

Cell Communication↗
PubMed1985

Effects of 6-thioguanine on communication competence and factors affecting reversibility of phorbol ester inhibition in V79 cells measured by the metabolic cooperation assay and by dye coupling.

One assay used to study the role of intracellular communication in tumor promotion examines chemically-induced inhibition of metabolic cooperation between 6-thioguanine (6-TG) sensitive (HGPRT+) V79 Chinese hamster cells in co-culture with 6-TG resistant (HGPRT-) cells. In the present study metabolic cooperation and Lucifer Yellow dye coupling were applied to detect intercellular communication. HGPRT+ cells were still communication competent when pre-incubated with 6-TG for up to 48 h before HGPRT- cells were plated. In both assays the phorbol esters 12-O-tetradecanoylphorbol-13-acetate (TPA) and phorbol-12,13-dibutyrate (PDBu) inhibited intercellular communication completely at 1 ng/ml. Using 6-TG metabolic cooperation, extensive washing of cells failed to reverse the inhibition caused by 100 ng TPA/ml after exposure for as little as 1 h. However, the effect of PDBu was completely eliminated if the drug was removed within 24 h. Complete blockade of dye coupling by 1, 10 or 100 ng TPA/ml was reversible after washing only at 1 ng/ml. Cells cultured in the presence of these TPA concentrations displayed significant reversal of dye coupling inhibition after 40 h. The results indicate that the onset of communication competence impairment between V79 cells by 6-TG is much slower than hitherto implied. Failure of intercellular communication to recover even from short exposure to 100 ng TPA/ml appears to be attributable to its lipophilic nature. Not enough TPA can be removed by washing to overcome its potent inhibitory action. These observations indicate that the physicochemical properties of a chemical must be taken into consideration before making judgements about the duration of inhibition.

Animals↗
PubMed1984

Effect of subchronic administration of methyl parathion on in vivo protein synthesis in pregnant rats and their conceptuses.

Pregnant rats received daily po doses of the organophosphate methyl parathion (MPTH) from Day 6 through Day 15 or 19 of gestation at doses causing no (1.0 mg/kg) or minimal (1.5 mg/kg) signs of maternal toxicity. Following the dose of MPTH on Day 15 or 19, in vivo protein synthesis was measured 0.5, 1.0, and 2.0 hr after sc injection of L-[1-14C]valine at a dose of 5 microCi/mmol/100 g body wt. The specific activity of [14C]valine in the free amino acid pool and protein bound pool was significantly reduced in various regions of maternal brain and in maternal viscera, placenta, and whole embryos (Day 15), and in fetal brain and viscera (Day 19). The inhibitory effect of MPTH on net protein synthesis was dose dependent, greater on Day 19 than 15 of gestation and more pronounced in fetal than in maternal tissues.

Animals↗
PubMed1984

Inhibition of metabolic cooperation between Chinese hamster V79 cells by structurally diverse teratogens.

Cell-cell communication through chemical messengers is a fundamental event required for the differentiation of embryonal cells. Interference with this process by xenobiotics may disrupt embryogenesis. Chinese hamster cells (V79) which display a specific form of cell-cell communication called metabolic cooperation were cultured in the presence of structurally diverse chemical teratogens. Among them were 12-O-tetradecanoyl-phorbol-13-acetate (TPA), diphenylhydantoin (DPH), warfarin, and a series of monoalkyl ethers of ethylene glycol with alcohol chain lengths from methyl to butyl. Sodium saccharin and ascorbic acid were examined to represent two chemicals which have been thoroughly tested for teratogenic effects in laboratory animals and cause no birth defects. Recovery of 100 6-thioguanine-resistant V79 (6-TGr) cells in coculture with 400,000 6-thio-guanine-sensitive V79 (6-TGs) cells in the presence of 6-thioguanine (6-TG) and the chemical agent was measured. In amounts that neither interfered with colony forming ability nor caused cytostasis when 100 6-TGr cells were plated alone, all of the substances except for saccharin and vitamin C increased the number of surviving 6-TGr cells in a concentration-related manner. The recovery was increased by the presence of TPA (to 100% by 4 ng/ml), DPH (from 26% at 91 microM to 43% at 274 microM), warfarin (from 15.5% at 162 microM to 44.5% at 487 microM) and to variable extents by all five glycol ethers. The most efficacious in the latter group of compounds was the isopropyl ether which raised 6-TGr recovery from 8% at 0.017 M to 66% at 0.087 M. Based on the evidence accumulated by previous studies involving TPA, we postulate that the teratogens employed inhibited metabolic cooperation. These observations suggest that V79 cells may be suitable to study inhibition of cell-cell communication as a mechanism of teratogenesis.

Animals↗
PubMed1984

Inhibition of intercellular communication between normal human embryonal palatal mesenchyme cells by teratogenic glycol ethers.

Cell-cell communication, possibly through gap junctions, is a fundamental event for the differentiation of embryonal tissues. Chemical substances which can interfere with this process may be able to disrupt embryogenesis. We have examined the response of a normal diploid human embryonal palatal mesenchymal (HEPM) cell line to glycol ethers. These cells have gap junctions whose function in cell-cell communication was inhibited by a model teratogen. Potential HEPM donor cells (2000 to 4000) were pulse labeled with 3H-uridine (10 microCi/mL; 3 hr) and then cocultured for 3 hr with 200,000 to 400,000 potential recipient cells in the absence or presence of 2-methoxyethanol (ME; 0.13-0.30 M) or 2-isopropoxyethanol (IPE; 0.05-0.1 M). Computer-assisted quantitative autoradiography was applied to assess the effects on metabolic cooperation. Although this phenomenon was inhibited by ME, the effect was probably not attributable to interference with gap junction-mediated transfer of labeled nucleotides but rather to the lack of formation of gap junctions resulting from cytotoxicity and poor physical contact between cells. The inhibition obtained with IPE was apparently not due to adverse effects on HEPM cells as judged by light microscopy and cell counts of recipients surrounding a given donor. The results suggest that HEPM cells are suitable to study disruption of cell-cell communication as a mechanism responsible for teratogenesis and offer the unique possibility to apply human embryonal cells. However, care has to be taken to assess potential cytotoxicity of xenobiotics, and further refinement of the criteria to detect adverse effects is required.

Autoradiography↗
PubMed1983

Release of acetylcholine from fragments of human term placenta and effects of the choline acetyltransferase inhibitor (2-benzoylethyl)trimethylammonium iodide.

Intact tissue from human term placenta contained 102 +/- 17 (n = 8) nmoles of acetylcholine (ACh)/g fresh tissue when analyzed by pyrolysis gas chromatography (GC). Free-hand dissection followed by extensive washing led to reductions of tissue ACh content (57 +/- 11 nmoles/g; n = 5) presumably as a result of release into the bathing medium. Presence or absence of physostigmine as an anticholinesterase agent in all solutions used had no significant effect on the ACh content of intact fragments immediately after dissection. Upon incubation at 37 degrees C a new steady state ACh concentration was established within 40-50 min (177 +/- 14 nmoles/g; n = 11) which reflected the content typical for purified villus. ACh was released continuously in amounts linearly related to incubation time up to 80 min, the longest time point examined. When the incubation volume was doubled there was an apparently immediate significant effect on release of ACh. Thereafter liberation of ACh continued at the rate observed prior to the volume perturbation. The stable choline acetyltransferase inhibitor (2-benzoylethyl)trimethylammonium (BETA) inhibited the enzyme rapidly and almost completely in tissue fragments. The drug affected the rate of ACh release significantly 40 min after addition to the bathing solution. At the same time it led to a depletion of the total ACh content that could be extracted from human placenta fragments.

Acetylcholine↗
PubMed1981

Human fetal membranes: investigations on membrane potentials and membrane 24Na permeability in vitro and the possible involvement of acetylcholine.

Amnion, chorion and amniochorion from human term placentae were mounted as a membranous partition in a suitable chamber. The existence of membrane potentials was investigated, but no evidence for their generation was seen either in control Earle's buffer or subsequent to the addition of 100 microM acetylcholine (ACh). Sodium movement was measured under isosmotic conditions by assessing the rate of radiosodium exchange down its radioactivity gradient. These measurements revealed that sodium exchange was independent of membrane orientation, occurred by diffusion and was unresponsive to the addition of ACh.

Acetylcholine↗
PubMed1981

Acetylcholine in human term placenta: tissue levels in intact fragments after inhibition in vitro of choline acetyltransferase and relationship to [14C]alpha-aminoisobutyric acid uptake.

Choline acetyltransferase (ChAc), the enzyme catalysing the biosynthesis of acetylcholine (ACh) in the non-innervated human placenta, was rapidly and persistently inhibited by (2-benzoylethyl)trimethylammonium (BETA) when the drug was applied to intact tissue fragments. This inhibition (50 per cent at congruent to 0.4 mmol/1 BETA) was coupled to a concomitant reduction in the active uptake against a concentration gradient of the nonmetabolizable amino acid alpha-aminoisobutyric acid (AIB). The reduction of AIB accumulation (50 per cent at congruent to 0.1 mmol/1 BETA) was temporally related to inhibition of ChAc. These effects suggest that AIB uptake by the human placenta and ACh biosynthesis catalysed by ChAc are related. Measurements of total ACh content in tissue samples treated in parallel with those destined for ChAc and AIB uptake determinations revealed that BETA (3 mmol/1) significantly reduced the ACh levels by 35 to 50 per cent. This drug concentration caused almost complete inhibition of ChAc and blockade of AIB accumulation.

Acetylcholine↗
PubMed1980

Acetylcholine in human placenta. Identification by pyrolysis gas chromatography/mass spectrometry and tissue levels following different modes of delivery.

Extracts from human term placentae were analyzed by pyrolysis gas chromatography (GC) combined with mass spectrometry. The only choline ester of carbonic acid whose presence could be unequivocally established was acetylcholine (ACh). The mass spectrum of its demethylated tertiary derivative dimethylaminoethyl acetate (nor-ACh) agreed entirely with that of authentic pyrolyzed ACh. The concentrations of ACh were determined in placentae obtained after vaginal or Caesarean delivery to investigate the claim that the latter resulted in tissue with higher concentrations of ACh-like activity presumably because ACh was not expended during labor and delivery. No differences inACh content were found with GC analysis. The ACh concentrations were 102 +/- 17 (n=8) nmoles/g fresh tissue (vaginal delivery) vs. 105 +/- 16 (n=6) nmoles/g (Caesarean section). The fetal membranes (amnion and chorion) and the umbilical cord contained no ACh under the analytical conditions with a limit of sensitivity of 200 pmoles ACh.

Acetylcholine↗
PubMed1980

Effects of acetylcholine on the clearance of [3H]-antipyrine in bilaterally perfused lobules of human term placenta.

Single isolated lobules from human term placenta were bilaterally perfused with a balanced salt solution. The clearance of [3H]-antipyrine from the maternal to the fetal circulation was measured in an oper perfusion circuit (no recycling). Acetylcholine (ACh, 10 and 100 microM) was added to the maternal perfusate to examine the hypothesis that ACh may control permeability and transport processes across the placental membranes. ACh reduced the flow- and diffusion-limited clearance of [3H]-antipyrine in a reversible manner. Similar effects were obtained with physostigmine (eserine, 10 and 100 microM), an inhibitor of choline ester hydrolyzing enzymes, and ACh acted synergistically on this clearance reduction.

Acetylcholine↗