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Biomedical subjects

J M Lauder

Publications and source records attributed to J M Lauder.

At least 55 records · Page 3Linked to original sources
PubMed1993

Serotonin and cardiac morphogenesis in the mouse embryo.

The possible involvement of the neurotransmitter serotonin (5-HT) and its binding protein (SBP) in cardiac morphogenesis was studied using mouse whole embryo culture (together with immunocytochemistry or 3H-thymidine autoradiography) and a cell migration assay. Embryos were cultured before and during the period of endocardial cushion formation, embryonic (E) days 9-12, in the presence of 5-HT, the monoamine oxidase (MAO) inhibitor nialamide, or an uptake inhibitor (fluoxetine or sertraline). For the migration assay, cells from the outflow tracts of E12 embryos were dissociated and placed in a chemotaxis chamber together with different concentrations of 5-HT. E9 embryos cultured in the presence of 10 microM 5-HT and nialamide exhibited intense 5-HT immunoreactivity (5-HT IR) throughout the myocardium. This staining was greatly diminished by fluoxetine, sertraline, or the absence of nialamide. As morphogenesis proceeded, myocardial staining in embryos exposed to 5-HT became restricted to developing endocardial cushion forming regions and was more completely blocked by uptake inhibitors. No evidence for 5-HT synthesis by myocardium was found at any age studied using the precursor L-tryptophan. SBP was present in endocardial cushions in cultured and uncultured embryos. 3H-thymidine autoradiography demonstrated that both fluoxetine and sertraline inhibited proliferation of cardiac mesenchyme, endocardium, and myocardium. These effects were most pronounced when exposure began at E9 (prior to cushion formation). Dose-dependent effects of 5-HT on migration of outflow tract cells were also observed. Taken together, these results suggest that 5-HT may play a role in cardiac morphogenesis during endocardial cushion formation.

1-Naphthylamine↗
PubMed1993

Prenatal expression of 5-HT1C and 5-HT2 receptors in the rat central nervous system.

The expression of mRNAs for two 5-HT receptors (5-HT1C, 5-HT2) has been investigated by evaluating in situ hybridization in the prenatal rat CNS. At Embryonic Day 14 (E14), the highest signal for 5-HT1C was found in the choroid plexus, while the marginal/intermediate (m/i) zones of the midbrain, brain stem (including monoaminergic groups), and spinal cord also displayed label. By E18-21 a number of more rostral regions contained transcript, including the hippocampus (CA1), in addition to more intense signal in midbrain, brain stem, and spinal cord. Expression in the choroid plexus appeared to peak between E16-E18, although considerable hybridization signal remained at E21. 5-HT2 transcripts were also detected at E14. Label was present in m/i zones of the midbrain and in a number of other areas. In comparison to 5-HT1C, 5-HT2 mRNA was distributed over a wider rostral-caudal extent at this age. As with 5-HT1C mRNA, signal increased over rostral and brain stem areas at late gestational ages with significant labeling appearing in the olfactory bulb, cerebellum, cortical plate and subplate, hippocampus (dentate gyrus), and monoaminergic nuclei. 5-HT1C and 5-HT2 receptor transcripts were also present over the meninges at E16 and may represent transient expression of these receptors. These expression patterns in the embryonic rat brain, in conjunction with previous evidence indicating that 5-HT can act as a differentiation signal for target neurons, suggests that prenatal 5-HT receptors are positioned to play a role in the prenatal development of the CNS.

Animals↗
PubMed1993

Serotonin and morphogenesis. Transient expression of serotonin uptake and binding protein during craniofacial morphogenesis in the mouse.

This study describes the timecourse of expression of low-affinity serotonin uptake sites in the developing craniofacial region of the mouse embryo. Whole mouse embryos were incubated in the presence of various serotonergic compounds followed by immunocytochemical localization of serotonin (5-HT) and its binding protein. In the gestational day 9 embryo (3-5 somites), 5-HT uptake was observed in the myocardium of the heart, the visceral yolk sac and foregut. A specific and transient pattern of 5-HT uptake was observed in the hindbrain neuroepithelium from day 9.5-11, where it was localized in rhombomeres 2-5 in the day 9.5 embryo. By day 10, when rhombomeres were no longer evident, uptake was present in the dorso-lateral neuroepithelium surrounding the fourth ventricle (rhombic lip; cerebellar anlage). Uptake of 5-HT was initially observed in the surface epithelium of the craniofacial region at day 10 (20-25 somites) and was greatly increased at day 11. The invaginating lens, nasal placode epithelium and otocyst also took up 5-HT at day 11. During these stages a 45 kD serotonin-binding protein (SBP) was expressed in craniofacial mesenchyme, and became progressively restricted to regions subjacent to epithelial uptake sites. These staining patterns were shown to be specific for 5-HT and SBP by their absence in embryos stained using preabsorbed antisera. The timecourse of these patterns are correlated with critical events in craniofacial morphogenesis including (1) onset of inductive epithelial-mesenchymal interactions, (2) invagination and fusion of placodal structures, (3) presence of rhombomeres, and (4) regions of low proliferative activity.

Animals↗
PubMed1993

In situ localization of tenascin mRNA in developing mouse teeth.

Tenascin is a large extracellular-matrix glycoprotein found in developing connective tissue. A cDNA probe to mouse tenascin, mTN2, was used to determine the cellular origins of this molecule in the murine tooth germ by in situ hybridization. At embryonic day 19, a hybridization signal significantly greater than background was detected with mTN2 in the subodontoblastic layer of the dental mesenchyme and in the inner enamel epithelium of the enamel organ. At postnatal day 1, a signal was detected over pre-odontoblasts and the strata intermedium and externum. No tenascin mRNA was detected in odontoblasts or the stellate reticulum at either age, and hybridization in ameloblasts was not significantly greater than background at postnatal day 1. Thus, much of the tenascin found throughout developing teeth appears to be synthesized by pre-odontoblasts and the inner enamel epithelium, the two populations of cells destined to generate mineralized matrix.

3T3 Cells↗
PubMed1993

Neurotransmitters as growth regulatory signals: role of receptors and second messengers.

In the adult nervous system, neurotransmitters act as chemical mediators of intercellular communication by the activation of specific receptors and second messengers in postsynaptic cells. This specialized role may have evolved from more primitive functions in lower organisms where these substances were used as both intra- and intercellular signalling devices. This view derives from the finding that a number of 'classical' neurotransmitters are present in primitive organisms and early embryos in the absence of a nervous system, and pharmacological evidence that these substances regulate morphogenetic activities such as proliferation, differentiation, cell motility and metamorphosis. These phylogenetically old functions may be reiterated in the developing nervous system and in the humoral functions of neurotransmitters outside the nervous system. This review will provide evidence for this hypothesis based on the commonality of signal transduction mechanisms used in primitive organisms, early embryos and non-neuronal cells, and relate these relationships to the functions of neurotransmitters in the developing nervous system. This discussion has generally been limited to neurotransmitters where non-neuronal functions have been studied and information regarding the involvement of receptors and second messenger pathways is available.

Animals↗
PubMed1993

p59fyn in rat brain is localized in developing axonal tracts and subpopulations of adult neurons and glia.

Expression of the c-fyn proto-oncogene was analysed in the developing and adult rat brain by subcellular fractionation and immunocytochemistry using polyclonal antibodies specific for its protein product (p59fyn). Immunoperoxidase staining revealed widespread localization of p59fyn in developing axonal tracts throughout the fetal (E18) rat brain. fyn immunoreactivity was not observed in most axon-rich regions of the adult brain, but continued to be expressed at elevated levels in the adult olfactory and vomeronasal systems. At other sites in the adult rat brain, fyn immunoreactivity was restricted to cell bodies of neuronal subpopulations, especially those in brain stem and hypothalamic nuclei, and to subpopulations of glial cells along axonal tracts in the medulla, optic nerve and white matter of the spinal cord. In the peripheral nervous system, fyn staining was also prominent in Schwann cells. Subcellular fractionation of fetal and adult rat brain confirmed the immunocytochemical localization, demonstrating an enrichment of p59fyn in membranes from a fetal brain fraction containing nerve growth cones, and lower levels in adult brain where there was only a small enrichment in synaptosomal membranes. The developmental regulation of p59fyn suggests that the fyn tyrosine kinase may serve separate cellular roles in axonal growth and specialized functions of mature neurons and glia.

Animals↗
PubMed1992

Serotonin promotes region-specific glial influences on cultured serotonin and dopamine neurons.

To test the hypothesis that glia mediate interactions between embryonic serotonergic (5-HT) neurons and dopamine neurons, we studied the effects of 5-HT in co-cultures of E14 raphe neurons of mesencephalic dopamine neurons and radial glia/astrocytes derived from the same (homotypic) or opposite (heterotypic) brain region using a dose (10(-5) M) that would produce 5-HT uptake into glial cells as well as activate 5-HT receptors. Morphometric analysis of 5-HT and tyrosine hydroxylase (TH) immunoreactive neurons revealed regional differences in the effects of 5-HT (and nialamide) on survival, cell soma size, and dendrite-like neurite outgrowth in neuronal-glial co-cultures. In general, 5-HT had more significant effects on both types of monoamine neuron when they were cultured with mesencephalic glia (GSN). Stimulatory effects of 5-HT on growth of TH neurons in GSN cultures suggest that developing raphe axons, which reach the mesencephalon during the early differentiation of these neurons, may enhance the influence of local glial-derived trophic factors. Likewise, the promotion of 5-HT neuronal survival in these cultures suggests that glial factors in the mesencephalon may contribute to the support of 5-HT neurons in addition to the influences of raphe glia. The inhibitory effects of 5-HT on neurite outgrowth by raphe neurons in GSN co-cultures indicates enhanced sensitivity of these neurons to the inhibitory effects of 5-HT in the presence of mesencephalic glia. The region-specific effects of 5-HT and nialamide in glial co-cultures suggest that raphe and mesencephalic glia may express different capacities for 5-HT uptake, receptors, and/or monoamine oxidase (MAO) activities. These characteristics could be important for the specificity of growth-regulatory influences of glial cells on the development of brain monoamine neurons.

Animals↗
PubMed1992

S-100 beta and insulin-like growth factor-II differentially regulate growth of developing serotonin and dopamine neurons in vitro.

To study the phenotypic specificity of S-100 beta and insulin-like growth factor II (IGF-II) for developing monoamine neurons, serotonin (5-HT) neurons from the embryonic day 14 (E14) rostral raphe or dopamine (TH) neurons from the substantia nigra/ventral tegmental area were cultured for 3 days in vitro (3 DIV) in the presence of these factors. Neuronotrophic effects were analyzed by computer-assisted morphometry of 5-HT and TH-immunoreactive neurons. S-100 beta and IGF-II differentially regulated the growth of 5-HT and TH neurons but did not affect their survival. S-100 beta significantly increased several parameters of neurite outgrowth by 5-HT neurons but inhibited the spatial extent (field area) of TH neurites. IGF-II promoted growth of cell bodies of both phenotype, but only stimulated neurite outgrowth by TH neurons. S-100 beta and IGF-II differentially affected the number of GFAP immunoreactive cells from raphe and substantia nigra, but these effects did not correlate with the specificity of neuronotrophic effects. S-100 beta and IGF-II immunoreactivities were expressed in glial cultures derived from the same brain regions, raising the possibility that these factors have autocrine effects on glia as well as paracrine actions on neurons. The results of this study suggest that specificity of neurotrophic factors for particular embryonic neurons may be correlated with their neurotransmitter phenotype.

Animals↗
PubMed1992

Serotonin as a regulator of craniofacial morphogenesis: site specific malformations following exposure to serotonin uptake inhibitors.

During craniofacial development in the mouse embryo (days 9-12 of gestation; plug day = day 1), transient expression of serotonin (5-HT) uptake in epithelial structures of this region correlates with critical morphogenetic events (Lauder et al., '88; Shuey, '91; Shuey et al., '89, '92). The purpose of the present investigation was to assess the possible functional significance of these uptake sites by examination of patterns of dysmorphology following exposure of embryos to selective 5-HT uptake inhibitors. Exposure of mouse embryos in whole embryo culture to sertraline, at a concentration (10 microM) which produced no evidence of general embryotoxicity, caused craniofacial malformations consistent with direct action at 5-HT uptake sites. Two other 5-HT uptake inhibitors, fluoxetine and amitriptyline, produced similar defects. The critical period of sertraline exposure occurred on days 10-11. The observed craniofacial defects were associated with decreased proliferation and extensive cell death in mesenchyme located 5-6 cell layers deep from the overlying epithelium. In contrast, the subepithelial mesenchymal layers showed normal or elevated levels of proliferation. From these results it appears that inhibition of 5-HT uptake into craniofacial epithelia may produce developmental defects by interference with serotonergic regulation of epithelial-mesenchymal interactions important for normal craniofacial morphogenesis.

1-Naphthylamine↗
PubMed1992

Ontogeny of glucagon messenger RNA in the rat pancreas.

The synthesis of proglucagon mRNA was studied in rat pancreas from day 11 of fetal gestation (E11) to maturity. Proglucagon mRNA was first detected on E11, the time that the pancreatic bud forms in developing rats. The synthesis of proglucagon mRNA and its translation product at this early time point in pancreatic development suggests an early differentiation of A cell function. Between E17 prenatally and day 10-14 postnatally, pancreatic proglucagon mRNA abundance was higher than in adult pancreas. Regulation of the abundance of pancreatic proglucagon mRNA therefore appears to underlie the previously documented increases in serum and pancreatic glucagon immunoreactivity in the late fetal and perinatal periods. By day 20 postnatally, pancreatic proglucagon mRNA declined to levels found in adult pancreas. Prenatally between E17 and E21, changes in proglucagon mRNA abundance did not parallel previously reported developmental changes in relative mass of proglucagon-producing pancreatic A cells. This suggests that changes in proglucagon mRNA abundance during these times may be attributed to changes in proglucagon gene transcription or proglucagon mRNA stability per cell. In contrast between E21 and maturity, changes in proglucagon mRNA abundance paralleled previously reported changes in relative A cell mass, suggesting no major changes in proglucagon gene transcription or mRNA stability per cell during these times.

Animals↗
PubMed1991

Serotonin and nialamide differentially regulate survival and growth of cultured serotonin and catecholamine neurons.

In this morphometric analysis of immunoreactive serotonin (5-HT) and tyrosine hydroxylase (TH) neurons in culture, 5-HT and the MAO inhibitor nialamide influenced the survival, cell body size and neurite outgrowth of embryonic day 14 (E14) 5-HT neurons after treatment from 1-3 days in vitro (DIV), but did not significantly affect E14 or E15 TH neurons of either the noradrenergic or dopaminergic phenotype. These treatments had minimal effects on 5-HT neurons derived from E15 embryos. The stimulatory effects of 5-HT on survival and somal growth of E14 5-HT neurons was in contrast to its inhibitory effects on neurite outgrowth, suggesting trophic and inhibitory autoregulation of different cellular compartments of developing 5-HT neurons. The decreased sensitivity of E15 5-HT neurons to these treatments, despite similar viability and growth of these neurons in control cultures, suggests the existence of a critical period for this regulation during the initial period of serotonergic neurogenesis when these neurons are forming the bilateral B4-9 raphe complex. The lack of significant effects of 5-HT on TH neurons suggests differential sensitivities of 5-HT and TH neurons to developmental regulation by this neurotransmitter.

Animals↗
PubMed1991

An atlas of the prenatal mouse brain: gestational day 14.

A prenatal atlas of the mouse brain is presently unavailable and is needed for studies of normal and abnormal development, using techniques including immunocytochemistry and in situ hybridization. This atlas will be especially useful for researchers studying transgenic and mutant mice. This collection of photomicrographs and corresponding drawings of Gestational Day (GD) 14 mouse brain sections is an excerpt from a larger atlas encompassing GD 12-18. In composing this atlas, available published studies on the developing rodent brain were consulted to aid in the detailed labeling of embryonic brain structures. C57Bl/6J mice were mated for 1 h, and the presence of a copulation plug was designated as GD 0. GD 14 embryos were perfused transcardially with 4% paraformaldehyde in 0.1 M phosphate buffer and embedded in paraffin. Serial sections (10 microns thickness) were cut through whole heads in sagittal and horizontal planes. They were stained with hematoxylin and eosin and photographed. Magnifications were 43X and 31X for the horizontal and sagittal sections, respectively. Photographs were traced and line drawings prepared using an Adobe Illustrator on a Macintosh computer.

Animals↗
PubMed1990

Neuronal-glial interactions: complexity of neurite outgrowth correlates with substrate adhesivity of serotonergic neurons.

To study the interactions between neurons of known transmitter phenotype and non-neuronal cells of glial or fibroblastic origin, serotonergic (5-HT) neurons were tested for their strength of adhesion and neurite outgrowth patterns on substrates of astrocytes or fibroblasts using a cell adhesion assay for transmitter-identified neurons, and morphometry of immunocytochemically stained neurons in dissociated cell cultures. Both the strength of adhesion and the rate and complexity of neurite outgrowth by 5-HT neurons were significantly greater on substrates of astrocytes compared to fibroblasts. These results provide evidence that 5-HT neurons can interact selectively with glia via cell surface determinants, and that this process may be important for the development of complex (dendrite-like) neuritic arbors. The methods developed in this study will be useful for future studies of interactions between transmitter-identified neurons and glial cells during ontogeny of the embryonic brain.

Animals↗
PubMed1990

Development of neurotransmitter systems in the mouse embryo following acute ethanol exposure: a histological and immunocytochemical study.

Acute maternal ethanol administration to C57B1/6J mice on gestational day 7 (GD7) results in facial and brain abnormalities similar to those reported in human fetal alcohol syndrome (FAS). Using this model, we assessed the damage to brain structures using histological methods and changes in developing neurotransmitter systems with immunocytochemistry. Cholinergic neurons in the forebrain were stained with a monoclonal antibody to choline acetyltransferase (ChAT). Catecholaminergic neurons in the midbrain and serotoninergic neurons in the hindbrain were stained with polyclonal antisera to tyrosine hydroxylase (TH) and serotonin (5-HT), respectively. Forebrain deficiencies, including loss of midline structures (olfactory bulbs, midline septation, medial septal area) and deficits in lateral and dorsal regions (neostriatum and cerebral cortex) were found in both GD14 embryos and GD18 fetuses. In severely affected offspring, complete loss of the septal region resulted in conjoined lateral ventricles and a reduction in the thickness of the ventricular zone surrounding the single ventricle, as well as a severe loss of ChAT neurons which would normally be located in this territory. However, no consistent changes were seen in the distribution or size of TH or 5-HT neuronal cell groups in the midbrain and hindbrain. These differences in effects on specific neurotransmitter systems reflect the fact that the forebrain is most severely affected by early ethanol administration, whereas the hindbrain is relatively spared. Such differential effects could produce an imbalance in developing neurotransmitter systems in the embryonic and fetal brain, which could explain some of the functional deficits observed in children with FAS.

Abnormalities, Drug-Induced↗
PubMed1990

Ontogeny of the serotonergic system in the rat: serotonin as a developmental signal.

The serotonergic system is an early forming component of the CNS circuitry, beginning its development on gestational days 11-12 in the rat. Owing to its early presence in the embryonic nervous system, 5-HT has been proposed to act as a developmental signal for receptive cells. In vivo and in vitro evidence that 5-HT can influence both biochemical and morphological differentiation of raphe neurons and receptive target cells suggests that this neurotransmitter may have an organizing function in the developing nervous system which involves effects on neurite outgrowth and other aspects of neuronal differentiation, including synaptogenesis. Such functions may be mediated by a variety of 5-HT receptors located on both neuronal and non-neuronal cells. The apparent function of 5-HT as a differentiation signal in the developing nervous system raises important issues regarding the use of psychoactive serotonergic drugs by pregnant women, since these drugs may act as neural teratogens in the unborn child.

Aging↗
PubMed1989

Ontogeny of cholinergic neurons in the mouse forebrain.

The development of cholinergic neurons in the mouse forebrain was studied by immunocytochemistry with a monoclonal antibody to choline acetyltransferase (ChAT), the rate-limiting enzyme for acetylcholine synthesis. Since this antibody stained dividing cells in ventricular germinal zones as well as differentiating neurons, likely routes of migration could be inferred on the basis of the location of immunoreactive (IR) cells at different gestational ages. Germinal zones for cholinergic cells were observed in all ventricular zones of the forebrain with the ventral zones generating the earliest cells by gestational day 13.5 (GD13.5). On GD14, ChAT IR cells were visible in the germinal zones of the eye, olfactory ventricle, anterior horn, and dorsolateral aspect of the lateral ventricle, lateral ganglionic eminence, ventro- and dorsolateral third ventricle, and in the pineal anlage (epiphysis). ChAT IR neurons continued to develop in these and additional germinal zones on GD15, including the medial, dorsal, and dorsomedial walls of the lateral ventricle, and the medial and dorsal ganglionic eminence. On GD16, ChAT IR neurons were located in the prelimbic, pyriform, and parietal cortices and the lamina terminalis, and a cluster of IR cells was observed in the ventricular zone of the caudatopallial angle. On GD17-18, neurons in the anterior olfactory nucleus, olfactory tubercle, horizontal and vertical nucleus of the diagonal band, and medial septal nucleus stained more darkly and were multipolar, whereas immature bipolar neurons appeared to continue their migration into the hippocampus and along major fiber tracts, such as the corpus callosum, external capsule, fornix and anterior commissure. This study provides a comprehensive view of the zones of origin, probable routes of migration, and final destination of cholinergic neurons in the mouse forebrain.

Aging↗
PubMed1989

Neuronal-glial interactions: quantitation of astrocytic influences on development of catecholamine neurons.

Effects of astroglia on the morphological and biochemical differentiation of catecholamine neurons from embryonic rat mesencephalon were studied in vitro, and compared to results obtained with fibroblasts. Neurite outgrowth and complexity were measured using computer-assisted morphometry on tyrosine hydroxylase immunoreactive neurons growing on preformed monolayers of astrocytes or fibroblasts. The morphological differentiation of these neurons was stimulated by the presence of astrocytes, and this effect was evident in various cellular compartments, including the size of the cell soma, length of neurites and neuritic segments, and the numbers of these segments. Tyrosine hydroxylase activity was measured biochemically in these cultures and was also found to be stimulated by the presence of astroglial monolayers. The implication of these results for the understanding of specific neuron-glial interactions during embryonic brain development is discussed.

Animals↗