PubMed Health⌕ Search

Biomedical subjects

J E Pintar

Publications and source records attributed to J E Pintar.

At least 55 records · Page 3Linked to original sources
PubMed1994

The developmental expression in rat of proteases furin, PC1, PC2, and carboxypeptidase E: implications for early maturation of proteolytic processing capacity.

The genes encoding mammalian subtilisin-like endoproteases furin, PC1, and PC2 have been isolated and are implicated in endoproteolytic cleavage of precursor molecules, which is a key step in posttranslational maturation of proproteins and neuropeptide precursors. Following endoproteolytic cleavage, the carboxyl-terminal basic amino acid residues are removed by carboxypeptidase E (CPE). We have examined the expression of these genes during rat development by in situ hybridization and compared their expression patterns to those of potential substrates. In the primitive streak stage of embryogenesis (e7) furin is expressed in both endoderm and mesoderm. This overall expression pattern is maintained until e10, when a distinctly higher level of furin expression is observed in the heart and liver primordia. In mid- and late gestational stages furin is broadly expressed in the peripheral tissues, and, therefore, may contribute to the proteolytic processing of numerous fetal proproteins, such as the precursors for natriuretic factors in heart and IGF-II throughout the embryo. In contrast, the expressions of PC1 and PC2 are initiated much later (e13) and are mainly confined to the developing nervous system, but with distinct spatial distributions. At midgestational ages, PC1 mRNA is mainly expressed in the hypothalamus and peripheral ganglia, while PC2 is expressed not only in these tissues but also in the thalamus, midbrain, pons, medulla oblongata, cortical plate, and spinal cord. Besides neuropeptide precursor processing in the nervous system, PC1 and PC2 may also be involved in the proteolytic processing in additional regions as evidenced by the finding that both PC1 and PC2 mRNAs are expressed in the embryonic pituitary and pancreas. CPE mRNA is expressed in both neural tissues and some non-neural tissues. In the developing nervous system, the expression of CPE encompasses all the regions where PC1 and PC2 are expressed and in fact includes most brain regions as neurogenesis proceeds. CPE mRNA is also expressed in some peripheral tissues, such as the embryonic heart and cartilage primordia, and in some cases its expression overlaps with furin expression. Thus, CPE may functionally collaborate during development with the subtilisin family of endoproteases in the completion of proteolytic processing of neuropeptide precursors in the nervous system and proproteins in the peripheral tissues. In the pituitary, the endoproteolytic processing of polyfunctional precursor proopiomelanocortin (POMC) occurs in a developmentally regulated manner. We have shown that while PC2 mRNA is predominantly expressed in the intermediate lobe in the adult, we observed an increased expression of PC2 mRNA in developing rat anterior lobe, peaking at early postnatal stages.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Tissue-specific expression of the insulin-like growth factor binding protein (IGFBP) mRNAs in mouse and rat development.

The insulin-like growth factor binding proteins (IGFBPs) are polypeptides which are thought to modulate the bioactivity of IGF-I and IGF-II, and may also have activities independent of the IGFs. The expression patterns of IGFBPs-1, -3, -4, and -6 in midgestational rodents were analyzed using in situ hybridization to begin to characterize the role of these IGFBPs during development. All IGFBPs are expressed at least as early as rat embryonic day 14 (e14), and each has a unique pattern of expression. IGFBP-1 mRNA is expressed by the liver throughout mid and late gestation. IGFBP-3 mRNA is expressed at high levels in the urogenital tract, several muscle groups, and the nasal epithelia. IGFBP-3 transcripts are also expressed at lower levels by many non-neural tissue types, including the liver, stomach, and heart. IGFBP-4 is abundantly expressed by many tissues in the developing embryo, with the notable exceptions of the spinal cord, specific cartilage groups, and the thymic cortex. IGFBP-6 is expressed in the liver by e14, and also by a previously unrecognized cell population surrounding developing cartilage. Taken together these observations suggest distinct roles in development for each of the IGFBPs.

Animals↗
PubMed1993

Expression of the P450 side-chain cleavage and adrenodoxin genes begins during early stages of adrenal cortex development.

The steroid hormone products of the fetal adrenal cortex play an essential role in normal maturation of several organ systems during fetal development. In addition, adrenal steroids appear to play a local role in the establishment and maintenance of the chromaffin cells of the adrenal cortex. Despite these developmental roles of cortical steroids, little is known about when the cells of the fetal rat adrenal cortex begin to undergo biochemical differentiation into cells capable of producing steroid hormones and whether the timing of developmental changes in cortical properties is related to chromaffin cell differentiation. To investigate these problems, in situ hybridization and immunocytochemistry were used to examine the ontogeny of expression of both the P450 side-chain cleavage (P450scc) and adrenodoxin genes during rat development. Transcripts from both genes (but not P450c17) and the respective proteins encoded by them were detected specifically in the cells of the presumptive cortex as early as embryonic day 12 (e12), which is several days before the layered architecture of the adrenal cortex is established and the earliest age at which biochemical differentiation of these cells has been detected. The spatial and temporal expression patterns for both genes were similar over the period examined (e12-e16.5), and no heterogeneity of expression was observed among cortical cells. In addition, significant increases in the accumulation of P450scc and adrenodoxin mRNA transcripts occurred during the midgestational period, when the synthesis and secretion of ACTH from the fetal pituitary are increasing.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Cortex↗
PubMed1993

Developmental regulation of proopiomelanocortin gene expression in the fetal and neonatal rat pituitary.

Expression of the POMC gene and secretion of its peptide products are under complex regulation in the pituitary by multiple factors. CRF stimulates POMC transcription and secretion in both adult anterior (AL) and intermediate (IL) pituitary lobes, whereas glucocorticoids have an inhibitory effect on POMC in the AL, but little, if any, effect in the IL. To determine when transcriptional responses elicited by these factors begin during development and whether they undergo changes during ontogeny, we used a solution hybridization/nuclease protection assay with a POMC exon 1-intron A splice junction probe to analyze simultaneously the levels of intron A-containing POMC heterogeneous nuclear RNA (hnRNA) and POMC mRNA in explant fetal and neonatal rat pituitaries. We examined responses to 8-bromo-cAMP, CRF, and dexamethasone (dex) at stages before and after innervation of the IL by dopaminergic neurons from the hypothalamus. Treatment of embryonic day 15 (e15) whole pituitaries with CRF (10(-7) M) for 1 h led to a 2.5-fold increase in the level of POMC hnRNA, while pretreatment with dex (10(-6) M) inhibited the CRF-induced stimulation of POMC transcription. These results demonstrate that by e15, POMC transcription is already responsive to both CRF and dex, and thus, functional receptors (coupled effectively to the POMC promoter) are present by this age. Initial studies of POMC mRNA levels at early postnatal ages showed that 1 mM 8-bromo-cAMP stimulated postnatal day 1 (p1) and p10 AL and neurointermediate lobe (NIL) POMC mRNA levels, and 10(-6) M dex inhibited this stimulation in p1 AL, p10 AL, and p1 NIL, but not in p10 NIL. These studies were extended to examine POMC hnRNA responses at these ages. Treatment with CRF for 1 h increased POMC hnRNA 1.9- and 1.5-fold in p1 and p10 AL, respectively, and pretreatment with dex blocked these CRF-mediated effects on AL POMC transcription. In the NIL on p1, CRF induced a 2-fold increase in POMC hnRNA, which (like that in the AL) was inhibited by 30-min pretreatment with dex; in contrast, on p10, dex did not affect the CRF-induced increase in POMC hnRNA. The glucocorticoid receptor subtype responsible for this effect was identified using treatments with specific agonist and antagonists. The type II receptor agonist RU 28362 had an effect similar to that of dex; at both 10(-6) and 10(-8) M, RU 28362 inhibited CRF-induced increases in POMC hnRNA in p1 NIL and p1 and p10 AL.(ABSTRACT TRUNCATED AT 400 WORDS)

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1992

Insulin-like growth factor I and II and insulin-like growth factor binding protein-2 RNAs are expressed in adjacent tissues within rat embryonic and fetal limbs.

Since the rapid proliferation of cells in a directed manner is a necessary component of limb formation, the distribution of locally produced mitogenic molecules within the developing limb is of considerable interest. We have used in situ hybridization to localize transcripts for both insulin-like growth factor binding protein-2 (IGFBP-2) and its ligands, the insulin-like growth factors I and II (IGF-I and IGF-II), within limb buds of rat embryos 10-16 days after conception (equivalent to stages 1-12 of mouse limb morphogenesis, Wanek et al, 1989. J. Exp. Zool. 249, 41-49). The mRNA for IGFBP-2 is very abundant in an anterior-posterior strip of ectoderm along the distal edge of the limb bud (the progenitor of the apical ectodermal ridge or AER) from as early as limb stage 1 (Embryonic Day 10) and is much less abundant in the rest of the limb ectoderm. A high level of IGFBP-2 expression continues to characterize the AER following its definitive appearance (stage 3) and throughout its existence (until stage 7). This is a period of rapid outgrowth during which the rate of mesodermal cell division is highest in cells nearest to the AER. The AER is known to have mitogenic activity in vitro and to direct limb outgrowth in vivo, but, until recently, few putative molecular correlates of these activities have been detected. The transcripts for IGF-I and IGF-II are also present at high abundance in developing limbs, especially in mesodermally derived cells. IGF-I mRNA is abundant in presumptive limb mesoderm from the beginning of limb outgrowth (just before stage 1), but is very low or undetectable in much of the rest of the embryo, while IGF-II mRNA becomes very abundant in limb mesoderm at stage 2. The distribution in limbs of both IGF-I and IGF-II mRNA changes dramatically during outgrowth and differentiation, so that their expression characterizes complementary populations of cells by stage 11. Taken together, these data suggest that IGFs and the IGF binding proteins, which may modulate IGF action, contribute to limb outgrowth and patterning.

Animals↗
PubMed1992

The embryonic pattern of rat insulin-like growth factor-I gene expression suggests a role in induction and early growth of the liver.

The classic experiments of LeDouarin and her colleagues demonstrated that the mesenchymal cells of the septum transversum induce both the rapid proliferation of the adjacent endodermally-derived foregut cells and their differentiation into the hepatocyte component of the liver. We have used in situ hybridization to test whether this inductive activity correlates with the developmental expression of genes encoding insulin-like growth factors-I and -II (IGF-I and -II) and/or proteins that may mediate IGF action (IGF binding protein-2 and the IGF-I receptor). We found that the onset of expression of the transcript for IGF-I in the septum transversum correlates precisely with the time that the inductive activity appears. In fact, the septum transversum is the earliest site of IGF-I mRNA expression detectable in the rat embryo by in situ hybridization.

Animals↗
PubMed1992

Expression of the IGFBP-2 gene in post-implantation rat embryos.

The insulin-like growth factors (IGFs) stimulate mitogenesis in a variety of cell types both in vitro and in vivo. These effects are mediated by both IGF receptors and a family of IGF binding proteins (IGFBPs), which are found complexed with the IGFs in serum and tissue fluids. Here we compare the sites of expression during early rat embryogenesis of the genes encoding the RGD-containing IGF binding protein IGFBP-2 and IGF-II. At all ages from early post-implantation through mid-gestation, the expression of IGFBP-2 was highly complementary to IGF-II. IGFBP-2 mRNA was detected throughout the epiblast of the egg cylinder as early as e7, when IGF-II expression was restricted to trophectoderm and other extraembryonic cells. As gastrulation proceeded, IGFBP-2 expression ceased as IGF-II expression began in the newly formed embryonic and extra-embryonic mesoderm, but was retained in other epiblast derivatives including the surface ectoderm and neuroectoderm, throughout its rostral-caudal extent. By e10-e11, IGFBP-2 expression in neuroectoderm was restricted to the rostral brain of the primary neural tube and was found in the new population of neuroepithelium formed in the tail bud during secondary neurulation. IGFBP-2 expression remained high in the ventricular layer of the rostral brain into mid-gestation ages but decreased or disappeared as cells entered the mantle layer and began to express the neurofilament-related gene alpha-internexin. IGFBP-2 mRNA was abundant in surface ectoderm, particularly that of the branchial arches, and all ectodermal placodes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Guinea pig pancreatic ganglia: projections, transmitter content, and the type-specific localization of monoamine oxidase.

The ganglionated plexus of the guinea pig pancreas was investigated by using histochemical, immunocytochemical, and tract-tracing methods in order to determine whether pancreatic ganglia are analogous to the ganglia of the enteric nervous system (ENS). Three lines of evidence suggest that the ganglia of the pancreas appear to be interconnected with one another, as are enteric ganglia. First, microinjections of the retrograde tracer Fluoro-Gold into individual pancreatic ganglia labeled the perikarya of neurons in distant pancreatic ganglia, whereas no labeling of neurons was observed if injections were placed in the connective tissue adjacent to pancreatic ganglia. Second, when the intercalating dye DiI was microinjected into single pancreatic ganglia in fixed tissues, DiI-labeled terminals were found in additional pancreatic ganglia. Finally, microinjections of the beta subunit of cholera toxin into individual pancreatic ganglia yielded similar results. The ganglionated plexus of the pancreas also expresses a diversity of transmitter content and cell type-specific localization of monoamine oxidase (MAO) that is analogous to the ENS. In common with guinea pig enteric ganglia, pancreatic ganglia contain highly varicose 5-hydroxytryptamine (5-HT)-immunoreactive axons and intrinsic neuropeptide Y (NPY)- and substance P (SP)-immunoreactive neurons. The vast majority, but not all, of SP-immunoreactive fibers in the pancreatic parenchyma also contain calcitonin gene-related peptide (CGRP) immunoreactivity. MAO-B was the primary type of MAO found in the intrinsic elements of the pancreas where it was located in neurons and fibers in the pancreatic parenchyma. In common with serotoninergic enteric neurons, MAO-B immunoreactivity was not found at the LM level in pancreatic serotoninergic neurites. In contrast, NPY- and tyrosine hydroxylase (TH)-immunoreactive perivascular axons were found to contain abundant MAO-A, but no MAO-B immunoreactivity. It is concluded that MAO-B immunoreactivity is characteristic of a portion of the intrinsic innervation of the pancreas, whereas MAO-A immunoreactivity is a marker for the extrinsic sympathetic innervation of the pancreas. Because of its receipt of a direct neural innervation from myenteric ganglia of the bowel (Kirchgessner and Gershon, '90: J. Neurosci 10:1626-1642), similar connections, transmitter content and localization of type-specific MAO, the ganglionated plexus of the pancreas should be regarded as an extension or subset of the ENS.

Animals↗
PubMed1990

Type-specific localization of monoamine oxidase in the enteric nervous system: relationship to 5-hydroxytryptamine, neuropeptides, and sympathetic nerves.

The localization in the guinea pig enteric nervous system (ENS) of monoamine oxidase (MAO) types A and B was investigated at the light and electron microscopic levels. Immunocytochemistry was used to visualize the enzyme protein and histochemistry was employed to study catalytic activity. Type specificity was achieved in histochemical studies by using deprenyl (0.5 microM) to inhibit MAO-B or clorgyline (0.1 microM) to inhibit MAO-A. The distribution of MAO-B immunoreactivity in the ENS corresponded to that of the sites of MAO activity found histochemically to be inhibited by deprenyl, but not clorgyline. MAO-B was observed to be the primary type of MAO found in the intrinsic elements of the ENS and was located in subsets of neurons in both submucosal and myenteric plexuses. MAO-B was not demonstrated immunocytochemically or histochemically in enteric glia, nor, at the light microscopic level, was there significant MAO-B activity or immunoreactivity in serotonin (5-HT)-immunoreactive neuronal cell bodies. In the submucosal plexus about 50% of the neurons expressed MAO-B; these neurons also contained neuropeptide y (NPY) and/or calcitonin gene related peptide (CGRP), but not substance P or vasoactive intestinal polypeptide (VIP). About 10% of myenteric neurons were intensely reactive for MAO-B; again MAO-B was co-localized with NPY and/or CGRP. In contrast to intrinsic neurons, extrinsic CGRP-immunoreactive nerve fibers contained no demonstrable MAO activity or immunoreactivity. Moreover, the sympathetic innervation, identified as varicose axons that degenerated after administration of 6-hydroxydopamine, contained abundant MAO-A, but no MAO-B activity or immunoreactivity. It is concluded that MAO-B is characteristic of a subset of intrinsic enteric neurons, while MAO-A is confined to the sympathetic innervation, which is extrinsic. At the electron microscopic level individual cells varied greatly in their degree of immuno- or cytochemically demonstrable MAO-B, which was most concentrated on the outer membranes of mitochondria. MAO-B immunoreactivity (but not cytochemical activity) was found on mitochondria in some serotoninergic perikarya identified by the simultaneous radioautographic detection of the uptake of 3H-5-HT. Mitochondria in most serotoninergic axon terminals displayed both MAO-B activity and immunoreactivity. Neurons receiving serotoninergic synapses often, but not invariably, contained MAO-B. Inhibition of neither MAO-B nor MAO-A appeared to slow the disappearance of 3H-5-HT loaded into enteric neurons significantly, even when intraneuronal storage of 5-HT was inhibited with tetrabenazine.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Transiently catecholaminergic (TC) cells in the bowel of the fetal rat: precursors of noncatecholaminergic enteric neurons.

Experiments were done to study the fate of transient catecholaminergic (TC) cells that develop in the rodent gut during ontogeny. When they are first detected, at Day E11 in rats, TC cells are distributed along the vagal pathway, in advance of the descending fibers of the vagus nerves, and in the foregut. The early TC cells coexpress the immunoreactivities of several neural markers, including 150-kDa neurofilament protein, peripherin, microtubule associated protein (MAP) 5, and growth-associated protein (GAP)-43, with those of the catecholamine biosynthetic enzymes tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH). All cells in the fetal rat bowel at Day E11 that express neural markers also express TH immunoreactivity. The primitive TC cells also express the immunoreactivities of neural cell adhesion molecule (N-CAM), neuropeptide Y (NPY), and nerve growth factor (NGF) receptor (and NGF receptor mRNA). By Day E12 TC cells are found along the vagal pathway and throughout the entire preumbilical bowel. At this age TC cells acquire additional characteristics, including MAP 2 and synaptophysin immunoreactivities and acetylcholinesterase activity, which indicate that they continue to mature as neurons. In addition, TC cells of the rat are immunostained at Day E12 by the NC-1 monoclonal antibody, which in rats labels multiple cell types including migrating cells of neural crest origin. Despite their neural properties, at least some TC cells divide and therefore are neural precursors and not terminally differentiated neurons. At Day E10 TH mRNA-containing cells were not detected by in situ hybridization; however, by Day E11 TH mRNA was detected in sympathetic ganglia and in scattered cells in the mesenchyme of the foregut and vagal pathway. At this age, the number of enteric and vagal cells containing TH mRNA is about 30% less than the number of cells containing TH immunoreactivity in adjacent sections. The ratio of TH mRNA-containing cells to TH-immunoreactive vagal and enteric cells is even less at Day E12, especially in more caudal regions of the preumbilical bowel. A similar decline in the ratio of TH mRNA-containing to TH-immunoreactive cells was not observed in sympathetic ganglia. After Day E12 TH mRNA cannot be detected in enteric or vagal cells by in situ hybridization; nevertheless, TH immunoreactivity continues to be present through Day E14. DBH, NPY, and NGF receptor immunoreactivities are expressed by TH-immunoreactive transitional cells in the fetal rat gut after TH mRNA is no longer detectable.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetylcholinesterase↗
PubMed1990

Developmental changes in levels of proopiomelanocortin intron A-containing heterogeneous nuclear RNA and mature messenger RNA in the anterior and neurointermediate lobes of the rat pituitary.

The POMC cells of the rat pituitary undergo dynamic phenotypic changes during differentiation. Here we have determined that alterations in the relative levels of a POMC precursor RNA species and POMC mRNA occur during development and may represent another level at which the POMC phenotype is developmentally regulated. We performed solution hybridization/nuclease protection assays using a POMC exon 1/intron A splice junction probe to quantitate levels of both intron A-containing POMC heterogeneous nuclear (hnRNA) and fully processed POMC mRNA in separated anterior and neurointermediate lobes of the fetal, neonatal, and adult pituitary. The levels of POMC hnRNA per anterior lobe increased 7-fold from embryonic day 15 to adulthood (0.022 to 0.159 fmol/lobe), while POMC mRNA levels increased 121-fold (0.15 to 18.2 fmol/lobe). POMC hnRNA levels per neurointermediate lobe increased 23-fold from embryonic day 18 to adulthood (0.024 to 0.54 fmol/lobe), while POMC mRNA levels increased 69-fold (0.65 to 44.6 fmol/lobe). Thus, both anterior and neurointermediate lobes contain higher relative abundances of POMC hnRNA compared to mRNA during early development. These subsequently decrease (from 1:7 to 1: approximately 110 in the anterior lobe and from 1:27 to 1:83 in the intermediate lobe over the ages examined) as the levels of POMC mRNA in both anterior and neurointermediate lobe increase at a greater rate than POMC hnRNA as development progresses. These results provide the first measurements of POMC mRNA and hnRNA levels during ontogeny and suggest that there may be a developmental change in the regulation of POMC primary transcript processing.

Animals↗
PubMed1990

The expression pattern of an insulin-like growth factor (IGF)-binding protein gene is distinct from IGF-II in the midgestational rat embryo.

Insulin-like growth factor-II (IGF-II), the predominant form of IGF in fetal and neonatal serum and tissues, is found in vivo complexed with IGF-binding proteins. One of these binding proteins, IGFBP-2, is present at high levels in fetal rat plasma and binds both IGF-I and IGF-II with high affinity. We here have used in situ hybridization to compare the distribution of IGFBP-2 mRNA with that of IGF-II mRNA in embryonic day 13.5-15 rat embryos. The spatial patterns of IGF-II and IGFBP-2 expression in the fetal trunk were distinct and, in general, nonoverlapping. Most mesoderm derivatives that express IGF-II at high levels contained little, if any, IGFBP-2 mRNA. Instead, IGFBP-2 mRNA was expressed at high levels in many cell types derived from ectoderm and endoderm. The expression of IGFBP-2 mRNA in the central nervous system (CNS) during this developmental period was examined in particular detail. The three most prominent sites of IGFBP-2 expression in the CNS were comprised of cells with nonneuronal phenotypes: 1) the epithelium of the choroid plexus, a tissue that produces cerebrospinal fluid; 2) the floor plate, an area that can guide axonal outgrowth from commissural neurons of the spinal cord in vitro; and 3) the infundibulum, the progenitor of the posterior pituitary that is believed to influence differentiation of the adjacent intermediate pituitary.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Stimulation of beta-endorphin secretion by corticotropin-releasing factor in primary rat Leydig cell cultures.

CRF, a hypothalamic peptide, is a potent stimulator of POMC synthesis and secretion in the pituitary. POMC biosynthesis has been documented in the testis, specifically in Leydig cells, and recent studies suggest that CRF is synthesized locally in the testis. A reverse hemolytic plaque assay and immunocytochemistry with Leydig cell-specific antibodies were used to study the effect of CRF on secretion of the POMC peptide beta-endorphin (beta EP) from normal rat primary Leydig cell cultures. In enriched Leydig cell preparations incubated with beta EP antiserum (diluted 1:50) then with complement (diluted 1:25), approximately 15% of immunocytochemically identified Leydig cells formed plaques. Preabsorption of the antiserum with beta EP (2 micrograms/microliters antiserum) overnight at 4 C abolished the formation of plaques. Increasing concentrations of CRF (from 10(-1) to 10(-7) M) resulted in an approximately 80% increase in both the percentage of plaque-forming cells and the mean plaque size. When the CRF antagonist CRF-(9-41) (10(-6) M) was added in the presence of CRF, the increases in plaque number and average size did not occur. These results demonstrate that Leydig cells have functional CRF receptors and that beta EP secretion from these cells is stimulated by CRF.

Animals↗
PubMed1989

Analysis of proopiomelanocortin gene expression during prenatal development of the rat pituitary gland.

The POMC gene is transcribed in 5-10% of adult rat anterior pituitary cells and nearly all intermediate lobe cells, but the end product peptide hormones produced by these two cell populations are distinct. We have here used in situ hybridization with 3H-POMC cRNA probes to investigate the temporal and spatial distribution of POMC mRNA containing cells during development of both lobes of the adenohypophysis. These hybridization patterns were, in addition, compared to the immunocytochemical distribution of POMC-related peptides on the same or adjacent sections. In both POMC populations, POMC-mRNA detection preceded POMC-derived peptide accumulation by at least 0.5 days. POMC-mRNA was first detected in the ventral aspect of Rathke's pouch (which will give rise to the anterior lobe) at e 13, which was two days earlier than POMC transcripts were first detected in the intermediate lobe; this result provides strong evidence that factors eliciting POMC transcription in these two populations act at distinct times during development. Further, since POMC mRNA containing cells were restricted to the anterior lobe during stages when intermediate lobe-like POMC peptides have been characterized biochemically, these results confirm immunocytochemical results and demonstrate that developmentally regulated alterations in the extent of POMC posttranslational processing occur during prenatal differentiation of anterior lobe POMC cells. POMC expression in the intermediate lobe was first observed in the midcaudal region in the midsagittal plane and subsequently extended in a gradient-like pattern to the rest of the intermediate lobe. Finally, semiquantitation of in situ hybridization signals documented that increases in the relative levels of POMC mRNA/cell occur at specific ages in both anterior and intermediate lobe. POMC cell populations and demonstrated that adult POMC mRNA/cell levels are not achieved before birth in either the anterior or intermediate lobe POMC cell populations.

Animals↗
PubMed1987

Differences in monoamine oxidase activity between cultured noradrenergic and cholinergic sympathetic neurons.

Two types of monoamine oxidase activity (MAO-A and MAO-B) help regulate the levels of biogenic amines such as catecholamines and serotonin. Although MAO-A has greater activity toward most catecholamines than MAO-B, no direct experiments have determined the types and levels of MAO activity that are normally expressed in noradrenergic neurons. Noradrenergic neurons from neonatal rat superior cervical ganglia were isolated and cultured under conditions that permit either continued expression of the noradrenergic phenotype or promote a transition to a predominantly cholinergic phenotype. After 14-21 days in vitro, neurons from both types of cultures were assayed for the type and amount of monoamine oxidase activity using tryptamine, a common substrate for both MAO-A and MAO-B. Neurons cultured under noradrenergic conditions expressed sevenfold greater MAO activity than neurons cultured under cholinergic conditions. Essentially all MAO activity in the noradrenergic cultures was inhibited by preincubation with 10(-8)-10(-9) M clorgyline, which indicated that this activity was primarily MAO-A. Cultures grown under cholinergic conditions exhibited 6- to 10-fold lower MAO-A activity and an 8- to 10-fold lower level of catecholamine synthesis from labeled precursors compared to neurons grown under noradrenergic conditions. These results directly demonstrate that high MAO-A activity is expressed in noradrenergic neurons in vitro. The corresponding decreases in both MAO-A specific activity and catecholamine synthesis as neurons become cholinergic in vitro suggest that the expression of the noradrenergic phenotype involves the coordinate regulation of degradative as well as synthetic enzymes involved in catecholamine metabolism.

Animals↗
PubMed1987

Region-specific expression of mouse homeobox genes in the embryonic mesoderm and central nervous system.

The homeobox is a 180-base-pair sequence characteristically found in homeotic and segmentation genes in Drosophila. Several copies of homeoboxes are also found in the mammalian genome, but it is not known whether these are components of morphogenetic loci in mammals as well. As a step toward understanding the function of mammalian homeoboxes, we have used in situ hybridization to define the spatial pattern of expression of two mouse homeobox genes in the midgestational mouse embryo. The two mouse homeoboxes studied here, Hox 1.2 and Hox 1.4, are located 20 kilobases apart on mouse chromosome 6. Our results demonstrate the following: (i) Hox 1.2 transcripts are localized mainly in the posterior myelencephalon, in the cervical central nervous system (CNS), and in several thoracic prevertebrae; (ii) Hox 1.4 transcripts are localized mainly in the posterior myelencephalon and in the cervical CNS; (iii) within the CNS region expressing Hox 1.4, the level of Hox 1.4 transcripts is higher in the mantle layer than in the ependymal layer and higher in the dorsal than in the ventral area. The specific localization of Hox 1.2 and Hox 1.4 transcripts in the embryonic CNS and the restricted pattern of expression along the rostrocaudal axis are strikingly reminiscent of the expression pattern of Drosophila homeoboxes in the fly embryo and larvae. Despite the different developmental strategies adopted by Drosophila and mammals, functional similarities may exist between Drosophila and mammalian homeobox genes.

Animals↗