摘要:

AbstractTreatment of the embryos of sea urchins with glyoxylic acid results in the appearance of luminescence which is indicative of the presence of biogenic monoamines. At the early stages of development (cleavage divisions, blastula, gastrula) the histochemical method reveals a tryptamine‐like substance which is first found in all embryonic cells and later is concentrated mainly in the cells of the primary gut and ciliary bands. At the stages of prism and pluteus there appear neuron‐like cells containing dopamine. The inhibitors of monoamine oxidase and neurotoxins reliably increase the histochemical reaction to monoamines only in late embryos which suggests a change in the properties of monoaminergic systems in the course of embryogenesis.

ISSN:0736-5748    

DOI:10.1016/0736-5748(85)90038-3

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractBiochemical, hormonal, and behavioural aspects of the effects of prenatal treatment (foetal days 18 and 19) with 6‐hydroxydopa (2 × 40 mg/kg) and DSP 4 (2 × 20 mg/kg) have been studied in the rat. The results of the catecholamine assays suggest that the 6‐hydroxydopa treatment produced a transient decrease of noradrenaline concentration in the cerebral cortex, and a long‐lasting decrease in the cerebellum, whereas DSP 4 produced a long‐lasting decrease in the cerebral cortex and a tendency towards increase in the cerebellum. Assays of adrenocorticotropic hormone and corticosterone indicated a general tendency towards increase in base line as well as in moderate stress situations. The results of behavioural tests indicated hyperactivity and/or hyperreactivity, but not restlessness, and partly supranormal sensorimotor performances.

ISSN:0736-5748    

DOI:10.1016/0736-5748(85)90039-5

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractWe report here the development in the chick embryo retina of binding sites for [3H]muscimol, a potent agonist of GABA receptors.In vivostudies were carried out with isolated neural retinas from different stages of development. High‐affinity binding sites were absent before embryonic day (E) 8, but increased conspicuously between E10 and E16. Scatchard analysis indicated that this rise was due to an increase in the number of binding sites. Kinetic parameters of the embryonic binding sites were consistent with those typically found for mature muscimol receptors. Measurements of the low‐affinity binding site showed a relatively similar developmental pattern although a pronounced decrease in binding to the low‐affinity site was observed between E12 and E14.In vitrostudies were carried out using glial‐free, purified monolayers of retinal neurons, starting at E8. Cultured retinal neurons showed a developmental pattern for high‐affinity muscimol binding sites resembling that observedin ovo. These binding sites were susceptible to regulation by cyclic AMP analogues. Increases of 100 to 200% in muscimol binding could be induced by a 24 hr treatment with dibutyryl cyclic AMP, 8‐bromo cyclic AMP, or the phosphodiesterase inhibitor IBMX. Scatchard analysis showed that this increase was due to a change in receptor affinity. No effects were found with either butyric acid or with adenosine 5′‐monophosphate. These results raise the possibility that cyclic AMP may be involved in the regulation of components of the GABA system.

ISSN:0736-5748    

DOI:10.1016/0736-5748(85)90040-1

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractProgressive increase in membrane resting potential (MRP) values in cultured chick embryo brain neurons were recorded from days 2 to 10 of development. Application of corticosterone or prednisone in 24 hr old cultured cells caused a significant increment in MRP recorded at day 2 of culture with respect to control. When ouabain was added to the corticosterone treated cells its effect on the MRP was impaired. An increment in protein synthesis and a reduction in sodium concentration were also observed in corticosterone pretreated cells. These results show that corticoids accelerate the differentiation process in cultured cells particularly the MRP, stimulating perhaps the Na+‐K+ATPase pump.

ISSN:0736-5748    

DOI:10.1016/0736-5748(85)90041-3

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThe phagocytes present in mechanically dissociated neonate rat cerebral hemispheres have been cultured and characterized both qualitatively and quantitatively. They comprise about 10% of the starting cell suspension and persist but do not proliferate in culture. They do not possess neuronal or neuroglial antigens but do express the leukocyte common antigen and readily ingest both latex beads and opsonized erythrocytes. the latter by an Fc receptor‐mediated process. Evidence is presented that these cells are a bona fida component of the neonate central nervous system.

ISSN:0736-5748    

DOI:10.1016/0736-5748(85)90042-5

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractOpiate receptor labeling was examined throughout the early postnatal period using autoradiography to localize and quantify [3H]naloxone binding to μ‐type opiate receptors in the medial preoptic area (MPOA). This region begins to exhibit sexual dimorphism of volume and dendritic growth shortly after birth. A distinct concentration of opiate receptor labeling appears on postnatal day 3 in females: this labeling is directly associated with the sexually dimorphic nucleus of the preoptic area (SDN‐POA). SDN‐POA labeling becomes denser through postnatal day 10 in females and the densely labeled area increases in size to encompass and surround the SDN‐POA. These changes in opiate receptor labeling occur only in females, since males show relatively uniform labeling across the region throughout the early postnatal period.The critical time of formation of dense MPOA opiate receptor labeling may be related to endogenous MPOA opioid function and to the critical period of dendritic growth of SDN‐POA neurons. The timing of these critical periods and their focus in the SDN‐POA are coincident. The possible role of MPOA opiate receptors in modulating growth of MPOA neurons is discussed.

ISSN:0736-5748    

DOI:10.1016/0736-5748(85)90043-7

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThe cytogenesis in the vestibular sensory epithelium of mouse embryo otocysts grown in organ culture was examined using tritiated thymidine autoradiography.Pulse‐labelingwith [3H]‐thymidine was applied eitherin vivo, at various intervals before explantation, orin vitroat specific stages of development. Observations of the developmentin vitroshowed that the cytogenesis and cytodifferentiation of vestibular sensory cells were disturbed by explantation. By varying the intervals between the [3H]thymidine exposure and the date of explantation, we were able to demonstrate that explantation itself caused a significant decrease in the mitotic and the postmitotic phases of the hair cell precursors. Labeling of the expiants excised on day 13 of gestation revealed that precursors of the hair cells were progressively losing their mitotic capacityin vitro. In contrast with this finding, precursors of the supporting cells were less affected by explantation and culture conditions and they retained the capacity for survival, proliferation and differentiation.

ISSN:0736-5748    

DOI:10.1016/0736-5748(85)90044-9

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractA quantitative ultrastructural study of microtubules in Purkinje cell dendrites of normal and hypothyroid developing rats was performed after fixation either at room or at low temperature (4°C). In normal animals, the density of microtubules and their fold‐stability increased with age, more especially during the period of intense dendritic growth. Thyroid deficiency delayed the appearance of microtubules and still more the acquisition of their fold‐stability. These effects might explain the defects in Purkinje cell dendritic growth and branching observed in hypothyroid animals.

ISSN:0736-5748    

DOI:10.1016/0736-5748(85)90045-0

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThe sites for [3H]nicotine binding in fetal brains were examined after administration of nicotine into pregnant rats. Administration of unlabelled nicotine into the pregnant rats increasedBmax values for the sites for [3H]nicotine binding without affectingKdvalues in the fetal brains. Treatment with this regimen, however, did not show any significant change in the sites for [3H]quinuclidinyl benzylate (QNB) binding. In addition, treatment with this regimen increasedBmax values of the sites for [3H]nicotine binding in the brains of pregnant rats. α‐Bungarotoxin had no effect on the sites for [3H]nicotine binding.It is inferred, therefore, that a similar response is elicited by nicotine binding sites to administered nicotine in both the fetal and maternal brains. Furthermore, a possible effect of nicotine in pregnant rats may be the facilitation of the development of nicotine acetylcholine receptors in the fetal brain.

ISSN:0736-5748    

DOI:10.1016/0736-5748(85)90046-2

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractParalysis of embryo during the period of naturally occurring motor neuron death produces an increase in the number of surviving neurons while the progressive differentiation and maturation of target muscle is severely retarded. Application of immunoglobulin G from patients with acquired myasthenia gravis to duck embryos during the period of trochlear motor neuron death also prevents this neuron loss but without paralyzing the embryo. The present study was conducted to investigate whether or not the differentiation and maturation of motor neurons, target muscle, and neuromuscular junctions were retarded following prevention of cell loss with myasthenic immunoglobulin. Immunoglobulin concentrates from myasthenics and normal human volunteers were applied daily to the chorioallantoic membrane of duck embryos from day 10 onward. The development of the trochlear neurons and the superior oblique muscle was examined with light and electron microscopy on embryonic days 12, 16 and 20. The motor neurons at the light and electron microscopic level were cytologically indistinguishable between the myasthenic and normal immunoglobulin‐treated embryos. Myoblasts fused to form myotubes. which further differentiated into mature myofibers at the same time in both groups. Numerous neuromuscular junctions of normal ultrastructure and nerve fibers with myelin wrappings were observed in both cases. It is concluded that the increased neuron survival following myasthenic immunoglobulin treatment does not accompany retardation in differentiation and maturation of the target muscle which is contrary to the results obtained from studies utilizing neuromuscular blocking agents producing increased cell survival.

ISSN:0736-5748    

DOI:10.1016/0736-5748(85)90047-4

出版商:Wiley    

年代:2003

数据来源: WILEY