PubMed Health⌕ Search

Biomedical subjects

E F Zimmerman

Publications and source records attributed to E F Zimmerman.

At least 37 records · Page 2Linked to original sources
PubMed1984

Neuropharmacologic teratogenesis and neurotransmitter regulation of palate development.

Neuropharmacologic agents may be more teratogenic to human beings by perturbing neurotransmitter mechanisms that regulate embryonic development. There is evidence that neurotransmitters function in mouse palate development: Serotonin and acetylcholine stimulate and GABA inhibits shelf reorientation. Both serotonin and GABA have been measured in the palate and uptake systems monitored. Serotonin stimulates cell motility, protein carboxyl methylation, and cyclic GMP. Diazepam (Valium) could cause cleft palate by mimicking GABA. Genetic differences in both diazepam teratogenesis and in a GABAergic system of the mouse have been observed. If human beings were to show genetic differences in a GABAergic system, some pregnant women could be at high risk when treated with diazepam.

Abnormalities, Drug-Induced↗
PubMed1983

Involvement of GABA in palate morphogenesis and its relation to diazepam teratogenesis in two mouse strains.

Previous studies have indicated that serotonin and acetylcholine stimulate palate shelf reorientation. The present studies were undertaken to determine whether gamma-aminobutyric acid (GABA) functions as an inhibitory neurotransmitter in the palate and whether diazepam mimics GABA to inhibit shelf reorientation and cause cleft palate. First, it was shown that 10(-4) M GABA inhibits palate shelf reorientation in day 14.5 AJ embryos cultured for 2 hours. Anterior palate reorientation stimulated by 10(-5) M serotonin was decreased by GABA; 10(-5) M picrotoxin (GABA antagonist) stimulated anterior shelf reorientation and reversed the effect of GABA. Diazepam (10(-4) M) partially inhibited palate shelf reorientation and that stimulated by 10(-5) M serotonin. Diazepam (400 mg/kg) was administered to AJ mice at day 13.5 of gestation and embryos were cultured at day 14.5. The inhibition produced by diazepam was significantly reduced by 10(-5) M picrotoxin. The teratogenic effect of diazepam was compared with AJ and Swiss-Webster Vancouver (SWV) inbred strains. Diazepam produced greater clefting in SWV mice (57% net) than in the AJ (18% net) when compared to their water- and food-starved controls. The greater sensitivity of the SWV strain than the AJ strain to diazepam, as well as to GABA, was also observed in embryo culture. GABA (10(-5) M) markedly inhibited posterior palate reorientation and reversed the stimulation produced by bethanechol in SWV mice. The inhibitory effects of GABA on the posterior palate were partially reversed by picrotoxin. Furthermore, diazepam inhibited palate reorientation either when administered to the pregnant dam or added in embryo culture.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Serotonin regulation of palatal cell motility and metabolism.

Serotonin has been previously shown to stimulate palate reorientation. To elucidate the mechanism by which the neurotransmitter may be regulating palate morphogenesis, the effects of serotonin on cell motility and various metabolic reactions have been measured in vitro. To monitor cell motility, a chemotactic system was employed in which cultured palate mesenchymal cells in a modified Boyden chamber migrate toward the chemoattractant(s) in N-18 neuroblastoma conditioned medium. Serotonin stimulated cell motility and 10(-5) M was optimal with nearly 100% stimulation achieved. With N-18 conditioned medium diluted 1:100, serotonin stimulated cell motility 4.9-fold. Serotonin itself was not chemotactic but modulated cell movement in the presence of the chemoattractant. Protein carboxyl methylation was stimulated by serotonin about 100% at concentrations ranging from 3 X 10(-7) M to 3 X 10(-6) M in different experiments. The net stimulation may have been elicited by an indirect effect since serotonin also inhibited demethylation of protein methyl esters. Serotonin was shown to inhibit cyclic AMP in cultured palate cells: 10(-5) M agonist depressed levels to 19% of control in 3 h. Further, prostaglandin E1, which stimulated cyclic AMP levels, markedly inhibited cell motility in the chemotactic assay. Thus there is an inverse relationship between cyclic AMP levels and cell motility in fetal palate cells. Finally it was observed that serotonin stimulated cyclic GMP levels; 10(-5) M serotonin optimally stimulated cyclic GMP with a spike of stimulation (6.1-fold) within 30 sec. In summary, serotonin in palate cells stimulates both protein carboxyl methylation and cyclic GMP. Modulation of these reactions could be regulating cell motility and/or protein secretion, which in turn could function in palate reorientation.

Animals↗
PubMed1983

Palate cell motility and substrate interaction.

To elucidate the mechanism by which palate shelves reorient during embryogenesis, migration of palate mesenchymal cells has been studied employing various substrates. When palate explants were cultured in a hydrated collagen lattice, it was observed that bipolar spindle-shaped cells migrated out of each explant toward the other. These cells were aligned parallel to each other and to the fibrous tracks that formed. The cells appeared to move along and through the fibrous tracks. Cell migration was dependent on the presence of serum and fibronectin. The fibrous tracks viewed by phase microscopy were sensitive to collagenase. Scanning electron microscopy revealed that the collagen fibers of the hydrated lattice had coalesced into larger bundles. Pretreatment of explants with serotonin stimulated cell migration out of the explant into the hydrated collagen lattice. This effect was specific, since the antagonist methysergide blocked the stimulation produced by serotonin. Employing other substrates, it was noted that palate cells migrating out of double explants toward each other produced large wrinkles in a polysiloxane substratum. Similarly, cultured monolayer cells also produced wrinkles that disappeared as cells rounded up after trypsin treatment. Finally, monolayer cells pulled on and distorted collagen films when cultured on the substrate. It is concluded that migrating palate cells can interact with their substrate producing tractional forces. Serotonin-induced modulation of cell motility and its relationship to palate reorientation are discussed.

Animals↗
PubMed1982

Prenatal and postnatal development of protein carboxymethylation activity in the mouse.

The carboxymethylation of endogenous methyl-accepting proteins in intact cells of whole embryos decreased between days 9.5 and 11.5 of gestation and thereafter increased. This fluctuation was not due to a change in the level of protein carboxymethylase (PCM) which remained constant during this period. Embryonic PCM was located predominantly in the cytosol of the embryonic cells, as is the case in adult tissues. Brain PCM specific activity was the same as the rest of the body from gestational days 13.5 to 19.5, but thereafter underwent a two- to threefold increase so that by the end of weaning (about 30 days), it had reached the high adult level. This time course suggests that increasing PCM may be part of the brain maturation process occurring during the neonatal period.

Age Factors↗
PubMed1981

Palate morphogenesis. VI. Identification of stellate cells in culture.

Mesenchymal cells from the palate of mouse embryos at day 14.5 of gestation produce a minor population of stellate cells in culture. These cells are often bipolar and spindle-shaped with long cytoplasmic processes similar to neural-crest cells. Culturing of explants of palatal mesenchyme enriched for this type of cell. Stellate cells were the first to migrate from explants, followed by fibroblast-like cells and then by squamous cells. The majority of the cells in the explant were fibroblast-like. Squamous cells were present mostly in the anterior and mid-palate and least frequently in those from the posterior palate. They may represent tooth-germ epithelium. When pieces of palate were dissected out and cultured for enrichment of non-muscle contractile systems, most of the migrating cells were stellate. These may represent the highly migratory cells that are, in part, responsible for elevation of the palate shelf. Serotonin was measured in cultured mesenchymal cells from the palate. Its occurrence is consistent with regulation of movement of palate cells.

Animals↗
PubMed1981

Presence of serotonin in the palate just prior to shelf elevation.

Since serotonin and its antagonists affect shelf rotation in mouse embryo culture, experiments were carried out to determine whether a serotonergic system is present in the palate. Employing [3H]5-HT, day-14.5 embryos incorporated the monoamine into palates. Active uptake of [3H]5-HT was shown since excised palates incorporated 9-fold more radioactivity at 37 degrees C than at 4 degrees C. Synthesis of palatal serotonin was measured. Embryos were cultured in the presence of the serotonin precursor, [3H]5-HTP, and radioactive 5-HT was monitored in the palate by thin-layer chromatography. Furthermore, excised palates were incubated with [3H]5-HTP and radioactive 5-HT was measured. Incorporation was linear for about 6 h. In addition, another radioactive compound was detected which had the same Rf as the methylated derivative, 5-methoxytryptamine. Synthesis of this compound was appreciable, about 30% of that of serotonin. Levels of serotonin in the palate were measured by high pressure liquid chromatography. Palates at day 14.5 of gestation contained 0.40 ng serotonin/mg protein, which was greater than that of tongue (0.33), body (0.14) but less than that of brain (3.09). Serotonin in palate and other embryonic tissues increased with time of development. Dopamine levels in the palate and other tissues were also determined. The distribution of serotonin in the palate was analyzed by culturing day-14.5 embryos in the presence of [3H]5-HTP, and after aldehyde fixation, paraffin embedment and sectioning, autoradiography was performed. Grains were observed throughout the palate in cells of regions 2 and 3, internal mesenchyme, tooth germ, and epithelium. Surprisingly, the pterygopalatine nerve, maxillary nerve and pterygopalatine ganglion contained an appreciable concentration of grains. Thus, the presence of serotonin in the palate is consistent with the neurotransmitter playing a role in shelf elevation.

Animals↗
PubMed1980

Palate morphogenesis: II. Contraction of cytoplasmic processes in ATP-induced palate rotation in glycerinated mouse heads.

It has been previously shown that non-muscle contractile system(s) exist in mouse palate mesenchyme underlying the palatal epithelium before shelf rotation. In order to obtain evidence that the non-muscle contractile system(s) function to elevate the palate, glycerinated heads have been incubated with ATP. It was shown that 5 mM ATP and a 30 min incubation at 25 degrees C stimulated palate rotation optimally. Elevation of the anterior end of the palate was nearly complete (PSI = 3.90, p less than 10(-6)). Although rotation of the posterior end was significant (p less than 0.02), movement was limited (PSI = 1.70). Light microscopy of the palate revealed that ATP caused a marked condensation of the cytoplasmic processes of the mesenchymal cells. The contraction of the processes of the mesenchymal cells induced by ATP increased roughly with increased palate shelf rotation and was greater at the peripheral than at the internal mesenchyme. Cytochalasin B pretreatment at 40 microM completely blocked the ATP-induced rotation at the anterior end. The effect of other nucleotides on palate rotation was tested. GTP caused a significant stimulation of anterior shelf rotation (p less than 0.005), which was less than ATP, while ADP and CTP were ineffective. Low temperature (6 degrees C) prevented the ATP-induced shelf rotation. These results suggest that the non-muscle contractile cells in the mesenchyme play a role in palate elevation and that contraction of the actomyosin containing microfilaments supplies the motive force.

Actomyosin↗
PubMed1980

Palate morphogenesis. I. Immunological and ultrastructural analyses of mouse palate.

Midpalate was analyzed for the presence of nonmuscle contractile systems. The results indicate that increased amounts of actin and myosin are present in cells of regions 2 and 3. A localization of the contractile proteins in cellular projections (filopodia) and in the peripheral cytoplasm of the cell body was confirmed by indirect immunofluorescence studies, using antibodies directed against smooth muscle myosin and against skeletal muscle actin. Specificity of the immunofluorescence reactions was ascertained by immunoabsorption studies using purified myosin and actin. Electron microscopic observations of the mesenchymal cells in region 2 revealed 70A microfilaments along the cell periphery and packed in fliopodia-like projections which course between the cells. These cells, which surround a small ossification center, show no orientation, but extend up to the cranial base perichondrium and down into the shelf between the tongue side epithelium and the ossification center. The cells and projections are attached to each other by adherens and tight-like junctions, forming a putative cohesive contractile network. Putative contractile cells in region 3 are strikingly aligned perpendicular to the oral epithelium and extend one-third of the distance into the shelf. Projections from region 3 cells are contiguous with basement membrane material of the oral epithelium. Axonal bundles and single axons were commonly observed coursing through regions 2 and 3, often seen in close association with the mesenchymal cells. Both clear and dense-core vesicles were found in the axons and cells of these regions. The possible role of these putative nonmuscle contractile cells in palate morphogenesis is discussed.

Actins↗
PubMed1980

Palate morphogenesis. V. Effects of cholinergic agonists and antagonists on rotation in embryo culture.

Morphological studies have shown that the pterygopalatine ganglion in the day-14.5 mouse palatal shelf lies adjacent to the putative contractile system of region-2 cells in the posterior palate. It is of interest to learn whether the ganglion could influence rotation of the palate. Results of embryo culture experiments showed that acetylcholine appeared to play a role in posterior shelf rotation since cholinergic agents (pyridostigmine, bethanechol and carbachol) stimulated elevation of that end of the palate. To characterize the putative receptors mediating the effects of the cholinergic agonists on palate shelf elevation, muscarinic or nicotinic antagonists were introduced into the emrbyo culture system. Atropine, a muscarinic blocking agent, did not produce any significant effect on palate shelf rotation when tested in overnight and 2 h embryo cultures at 3 X 10(-5) M and 10(-4) M, respectively. Neither did atropine inhibit significantly the stimulation produced by 10(-8) M bethanechol, Thus, the cholinergic effect was probably not on muscarinic receptors of the contractile system. However, hexamethonium, a nicotinic antagonist, at 10(-6) M and 10(-4) M profoundly inhibited posterior shelf rotation to about 35% of the control value in a 2 h incubation. In addition, 10(-4) M hexamethonium inhibited posterior palate rotation to 11% of the control value after overnight culture. Furthermore, hexamethonium was able to reverse the stimulation of posterior rotation produced by carbachol. Partial inhibition of palate rotation by hexamethonium was also demonstrated when pregnant dams were injected with drug at doses approximately corresponding to 10(-6) and 10(-4) M. Hexamethonium treatment resulted in approximately 30% of the palates not completely rotated at day 15.5 compared to only 9.3% in the control. Hexamethoniuim also produced a significant increase in the palate gap and a comparable decrease in palate fusion. These effects were slightly greater at the posterior end of the palate. Thus, the cholinergic ganglion in the posterior palate may play a role in regulating shelf rotation at that end through a nicotinic pathway.

Acetylcholinesterase↗
PubMed1979

Palate morphogenesis. III. Changes in cell shape and orientation during shelf elevation.

The process of palate shelf elevation has been analyzed by light microscopy in mouse embryos cultured in vitro. The observations presented correlate changes in cell shape and orientation in the palate with the morphogenetic movement of the shelf. These studies suggest that in addition to any physical-chemical force elevating the shelf an active contraction of specific palate cells could also aid the process. Contribution to elevation could be derived from masses of contracting cells from the previously described non-muscle contractile systems in posterior (region 2) and mid-anterior (region 3) palate as well as other peripheral mesenchymal cells. Finally, elongation and contraction of the tongue side epithelial cells may also play a role in palate elevation.

Animals↗
PubMed1979

Palate morphogenesis. IV. Effects of serotonin and its antagonists on rotation in embryo culture.

Previous studies have localized non-muscle contractile systems in the posterior (region 2) and the anterior (region 3) ends of mouse palates at the time of shelf movement. In order to determine whether these contractile systems function in shelf rotation, effects of pharmacologic agents have been analyzed in embryo culture. First, it was shown that the posterior end of the palate rotates before the anterior end, and its rotation in culture was proportionally greater as development of the embryo progressed. Generally, the posterior end of the palate was more easily inhibited in embryo culture than the anterior end. Serotonin at 10(-8) M to 10(-5) M was shown to significantly stimulate rotation at the anterior end of the palate after 2 h in embryo culture. The effect on the posterior palate was less pronounced. To investigate further the role of this neurotransmitter on palate shelf rotation, serotonin antagonists were employed. Methysergide (10(-4) M) inhibited anterior shelf rotation to 12% of control values (P less than 0.005), while not significantly affecting the posterior end. Ergotamine (10(-6) M) significantly inhibited the stimulation induced by 10(-5) M serotonin (P less than 0.025). Cyproheptadine (10(-9) M) partially inhibited anterior and posterior shelf rotation in embryo culture. When injected into the pregnant dam, cyproheptadine partially inhibited shelf rotation and fusion. The palate was examined histologically after embryo culture. In the presence of 10(-4) M methysergide, the elongated contractile cells in region 3 at the anterior and midpalatal mesenchyme were prevented from rounding. Thus, serotonin may be regulating rotation of the anterior end of the palate by an effect on cell-mediated process.

Animals↗