Specific Neuronal Cell Research Articles

Expression and estrogen regulation of progesterone receptor mRNA in neurons of the mediobasal hypothalamus: an in situ hybridization study.

Diverse effects of steroid hormones on different tissues result from the tissue-specific regulation of target gene expression by steroid hormone receptors. These receptors belong to a family of transacting factors that regulate transcriptional activation of target genes by binding to DNA recognition sequences located in the 5'-flanking region of the target gene. In the brain, receptors for the gonadal steroid hormones estrogen (E) and progesterone (P) are present in discrete neuronal populations. These steroid hormone receptor-containing neurons mediate the effects of the gonadal steroids on a number of neural processes, including reproductive behavior. Using in situ hybridization we have found progesterone receptor (PR) mRNA-containing neurons present in specific hypothalamic nuclei and in the amygdala. E regulates PR mRNA levels in specific neuronal cell groups which express both ER and PR (in basomedial hypothalamus), but not in others (medial amygdala). The E-induced increase in P-responsive neurons in ventromedial hypothalamus can account for the permissive influence of E on P-facilitated reproductive behavior. This is the first demonstration that synthesis of a transcription factor (PR) can be related to a mammalian behavior.

The monoclonal antibody B30 recognizes a specific neuronal cell surface antigen in the developing mesencephalic trigeminal nucleus of the mouse

A monoclonal antibody, B30, obtained with whole cells from embryonic brain as an immunogen, recognizes a neuronal cell surface antigen that appears only in 2 distinct systems in the developing mouse brain: the trigeminal system and the cerebellum. In the trigeminal system, B30 labels the surface of neurons, including their axons and their transient dendrites, in 2 groups of cells: the centrally located mesencephalic trigeminal nucleus and the peripheral trigeminal ganglion. Immunoreactivity is detectable during axon outgrowth, peaks around the seventh postnatal day, and disappears around 2 weeks after birth. In the cerebellum, B30 labels 2 layers of cells during development. Perinatally, and for about a week after birth, the layer of premigratory granule cells stains. After their maturation, Purkinje cells start to stain and by 12 d postnatally all the Purkinje cell bodies, their axons, and their dendritic trees show strong immunoreactivity. Subsequently, and in the adult, this staining is lost from some cells to reveal bands of antigen positive and negative Purkinje cells. Initial biochemical characterization of the epitope shows that it is carried on 2 minor gangliosides.

Peripheral motoneuron interactions with laminin and Schwann cell-derived neurite-promoting molecules: developmental regulation of laminin receptor function.

Schwann cells synthesize several neurite outgrowth-promoting molecules and localize them in either the extracellular matrix (ECM; e.g., laminin) or on the plasma membrane (e.g., L1/NgCAM and N-cadherin). Neurite outgrowth by embryonic chick ciliary ganglion (CG) neurons in response to these Schwann cell molecules largely depends on several specific neuronal cell surface receptors: integrin beta 1-class ECM receptors, L1/NgCAM, and N-cadherin (Bixby et al.: Journal of Cell Biology 107:353-361 1988). To address whether neuronal ECM receptors are regulated independently of cell surface adhesion molecules, we studied the ability of dissociated CG neurons from different developmental ages to extend neurites rapidly on 1) substrates coated with the ECM glycoprotein laminin (either from Schwann cell-conditioned medium or purified from the Engelbreth-Holm-Swarm sarcoma) or 2) the surfaces of Schwann cells or Schwannoma (RN22) cells. CG neurons gradually lost the ability between embryonic day 8 (E8) and E14 to attach to and extend neurites in an integrin-dependent fashion on purified laminin or Schwann cell-derived laminin. The inability of E14 CG neurons to respond to laminin was partially reversed after explantation for 2.5 days in vitro, which increased the percentage of responsive neurons approximately ten-fold. E14 neurons remained capable of extending neurites rapidly on the surfaces of Schwann and Schwannoma cells. Thus, the inability of E14 neurons to respond to laminin reflects a specific loss of laminin receptor function, while other receptors, most likely N-cadherin and L1/NgCAM, remain capable of promoting neurite outgrowth on Schwann cell surfaces. Since integrin beta 1-class heterodimers have been shown to function directly as receptors mediating neuronal attachment and process outgrowth on laminin, our results imply that the expression or function of laminin-binding integrin heterodimers is regulated during the development of CG neurons. The apparent loss of integrin receptor function occurs during the period when the axons of CG neurons innervate their targets. Substantial integrin receptor function is recovered when target contact is disrupted by explantation. Thus, the functions of integrin-class receptors in CG neurons may be regulated by target contact.

Neurotoxicity of MPTP and MPP + in vitro: characterization using specific cell lines

The effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and its putative toxic metabolite 1-methyl-4-phenylpyridinium ion MPP + were studied with specific neuronal and glial cell lines in vitro. MPTP had no morphological effect on actively growing neuroblastoma N 2AB-1 cells or C 6 glioma cells nor did it affect cell numbers. However, a low dose of MPP + (33.7 μM) was cytotoxic to mitotic N 2AB-1 cells inducing vacuole formation, cell lysis, and inhibiting cell growth over a 3-day period. Protein synthesis was inhibited in a dose-dependent fashion in MPP + treated N 2AB-1 cells after 24 h exposure while 33.7 μM of this toxin induced a 50% decrease in protein synthesis as early as 5 h after treatment of these cells. Differentiated, neurite-bearing N 2AB-1 cells exhibited a loss of neurites and a change in cell size and shape following exposure to 0.33, 3.37 and 33.7 μM MPP + after 24 h and some cells appeared to be mitogenically stimulated indicating MPP + may act as a teratogen. C 6 glioma cells, however, were resistant to MPP +. While mitotic N 2AB-1 cells incubated with MPTP produced only traces of MPP +, C 6 glioma cells generated significant amounts of this metabolite (3.6 μM). Moreover, although the morphology and cell number of cocultures did not change in the presence of MPTP, glioma-neuroblastoma cocultures produced 2.90 μM MPP + which decreased protein synthesis by 18%. Therefore, the early changes in protein synthesis and loss of neurites of cells treated with MPP + in vitro as seen in this study may reflect the drop in catecholamine levels and dying back of fibers seen in administration of MPTP in in vivo studies. These findings suggest that this in vitro system may provide a useful model to assess the role of individual cell populations in the response to neurotoxic agents.

Monoclonal antibodies specific for glial and neuronal antigens in the young rat cerebellum

Monoclonal antibodies from 15 different hybridomas derived from the fusion of mouse spleen cells with a myeloma cell line were selected. Mice were immunized with the particulate fraction from 10–13-day-old rat cerebella. Hybridoma secreting antibodies were screened simultaneously by both immunocytochemistry and binding assay. Each antibody reacts with specific cerebellar neuronal or glial cells and structures.