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L J Muglia

Publications and source records attributed to L J Muglia.

14 recordsLinked to original sources
PubMed1999

Stress-induced behaviors require the corticotropin-releasing hormone (CRH) receptor, but not CRH.

Corticotropin-releasing hormone (CRH) is a central regulator of the hormonal stress response, causing stimulation of corticotropin and glucocorticoid secretion. CRH is also widely believed to mediate stress-induced behaviors, implying a broader, integrative role for the hormone in the psychological stress response. Mice lacking the CRH gene exhibit normal stress-induced behavior that is specifically blocked by a CRH type 1 receptor antagonist. The other known mammalian ligand for CRH receptors is urocortin. Normal and CRH-deficient mice have an identical distribution of urocortin mRNA, which is confined to the region of the Edinger-Westphal nucleus, and is absent from regions known to mediate stress-related behaviors. Since the Edinger-Westphal nucleus is not known to project to any brain regions believed to play a role in anxiety-like behavior, an entirely different pathway must be postulated for urocortin in the Edinger-Westphal nucleus to mediate these behaviors in CRH-deficient mice. Alternatively, an unidentified CRH-like molecule other than CRH or urocortin, acting through the CRH receptors in brain regions believed to mediate stress-induced behaviors, may mediate the behavioral response to stress, either alone or in concert with CRH.

Animals↗
PubMed1999

Corticotropin-releasing hormone deficiency unmasks the proinflammatory effect of epinephrine.

Traditionally, the adrenal gland has been considered an important endocrine component of the pathway to inhibit acute inflammation via hypothalamic corticotropin-releasing hormone (CRH)-mediated secretion of glucocorticoid. Immunoreactive CRH found in inflamed tissues is a potent proinflammatory factor. Using genetic and pharmacological models of CRH deficiency, we now show that CRH deficiency unmasks a major proinflammatory effect of epinephrine secreted from the adrenal medulla. Together, epinephrine and peripheral CRH stimulate inflammation, and glucocorticoid acts as a counterbalancing force in this regard. Our findings suggest that stimulation of the acute inflammatory response should be included with the other "fight-or-flight" actions of epinephrine.

Adrenal Glands↗
PubMed1999

The 5'-flanking region of the mouse adenylyl cyclase type VIII gene imparts tissue-specific expression in transgenic mice.

The calcium-stimulated adenylyl cyclases (ACs) play a central role in stimulus-dependent modification of synaptic function. The type VIII AC (AC8) is one of three mammalian calcium-stimulated isoforms, each of which is expressed in a region-specific manner in the CNS. To delineate the DNA sequences responsible for appropriate targeting of AC8 expression, we report here the complete structure of the AC8 gene and define the pattern of expression of the full-length cDNA and its splice variants. In addition to expression within the brain, robust expression of AC8 was also found in the lung. By in situ hybridization, we have found the highest expression of AC8 mRNA within the olfactory bulb, thalamus, habenula, cerebral cortex, and hypothalamic supraoptic and paraventricular nuclei. By generating transgenic mice whose expression of beta-galactosidase is controlled by the AC8 5'-flanking DNA sequences, we demonstrate that the DNA sequences within the 10 kb preceding exon 1 are critical for establishment of this region-specific pattern. This spectrum of sites of production is unique to AC8 among the calcium-stimulated adenylyl cyclases and suggests nonredundant functions with other adenylyl cyclases in neuroendocrine regulation and/or behavior.

Adenylyl Cyclases↗
PubMed1999

Calcium-stimulated adenylyl cyclase activity is critical for hippocampus-dependent long-term memory and late phase LTP.

It is hypothesized that Ca2+ stimulation of calmodulin (CaM)-activated adenylyl cyclases (AC1 or AC8) generates cAMP signals critical for late phase LTP (L-LTP) and long-term memory (LTM). However, mice lacking either AC1 or AC8 exhibit normal L-LTP and LTM. Here, we report that mice lacking both enzymes (DKO) do not exhibit L-LTP or LTM. To determine if these defects are due to a loss of cAMP increases in the hippocampus, DKO mice were unilaterally cannulated to deliver forskolin. Administration of forskolin to area CA1 before training restored normal LTM. We conclude that Ca2+-stimulated adenylyl cyclase activity is essential for L-LTP and LTM and that AC1 or AC8 can produce the necessary cAMP signal.

Adenylyl Cyclases↗
PubMed1999

Proliferation and differentiation defects during lung development in corticotropin-releasing hormone-deficient mice.

Corticotropin-releasing hormone-deficient (CRH-KO) mice, which as a consequence are also glucocorticoid-insufficient, exhibit neonatal lethality when derived from CRH-KO mothers. Death is due to respiratory insufficiency as a result of abnormal pulmonary development, and can be prevented by prenatal administration of glucocorticoids. In the study described here, we used CRH-KO mice as a model of genetically altered in utero glucocorticoid action to elucidate the role of endogenous glucocorticoids in lung maturation. The histologic appearance of the lungs of these mice is normal until Day 17.5 of gestation, at which point failure of septal thinning and air-space formation is observed. These morphologic alterations in the CRH-KO mouse lung are the result of continued cell division in cellular compartments that by this time in gestation have ceased proliferating in wild-type mice, rather than the result of a failure of apoptosis. In accord with this observation, the CRH-KO lung exhibits delayed induction of type II pneumocyte biochemical parameters, such as messenger RNAs (mRNAs) for surfactant protein-A (SP-A) and SP-B, and fatty acid synthase, as well as delayed Clara cell maturation. In contrast, surfactant phospholipid synthesis is not impaired during CRH-KO lung development. Our findings indicate that an essential role of endogenous glucocorticoids in pulmonary maturation in utero is to stimulate a developmental program in late gestation that affects epithelial and mesenchymal cell proliferation and differentiation throughout the parenchyma.

Animals↗
PubMed1999

Reciprocal changes in the expression of transcription factors GATA-4 and GATA-6 accompany adrenocortical tumorigenesis in mice and humans.

While certain genetic changes are frequently found in adrenocortical carcinoma cells, the molecular basis of adrenocortical tumorigenesis remains poorly understood. Given that the transcription factors GATA-4 and GATA-6 have been implicated in gene expression and cellular differentiation in a variety of tissues, including endocrine organs such as testis, we have now examined their expression in the developing adrenal gland, as well as in adrenocortical cell lines and tumors from mice and humans. Northern blot analysis and in situ hybridization revealed abundant GATA-6 mRNA in the fetal and postnatal adrenal cortex of the mouse. In contrast, little or no GATA-4 expression was detected in adrenal tissue during normal development. In vivo stimulation with ACTH or suppression with dexamethasone did not affect the expression of GATA-4 or GATA-6 in the murine adrenal gland. To assess whether changes in the expression of GATA-4 or GATA-6 accompany adrenocortical tumorigenesis, we employed an established mouse model. When gonadectomized, inhibin alpha/SV40 T-antigen transgenic mice develop adrenocortical tumors in a gonadotropin-dependent fashion. In striking contrast to the normal adrenal glands, GATA-6 mRNA was absent from adrenocortical tumors or tumor-derived cell lines, while GATA-4 mRNA and protein were abundantly expressed in the tumors and tumor cell lines. Analogous results were obtained with human tissue samples; GATA-4 expression was detected in human adrenocortical carcinomas but not in normal tissue, adenomas, or pheochromocytomas. Taken together these results suggest different roles for GATA-4 and GATA-6 in the adrenal gland, and implicate GATA-4 in adrenal tumorigenesis. Immunohistochemical detection of GATA-4 may serve as a useful marker in the differential diagnosis of human adrenal tumors.

Adrenal Cortex↗
PubMed1998

Opposing actions of prostaglandins and oxytocin determine the onset of murine labor.

Prostaglandins (PGs) have been recently proven essential for parturition in mice. To dissect the contributions of the two cyclooxygenase (COX) isoforms to the synthesis of PGs during pregnancy, we have characterized the parturition phenotype of COX-1-deficient mice. We find that mice with targeted disruption of the COX-1 gene have delayed parturition resulting in neonatal death. Results of matings of COX-1-deficient females with COX-1 intact males, and blastocyst transfer of COX-1-deficient or -intact embryos into wild-type foster mothers, proved necessity and sufficiency of maternal COX-1 for the normal onset of labor. COX-1 expression is induced in gravid murine uterus and by in situ hybridization; this induction is localized to the decidua. Measurement of uterine PGs further confirmed that COX-1 accounted for the majority of PGF2alpha production. To evaluate the interaction of PGs with oxytocin during murine labor, we generated mice deficient in both oxytocin and COX-1. Surprisingly, the combined oxytocin and COX-1-deficient mice initiated labor at the normal time. COX-1-deficient mice demonstrated impaired luteolysis, as evidenced by elevated serum progesterone concentration and ovarian histology late in gestation, and delayed induction of uterine oxytocin receptors. In contrast, simultaneous oxytocin and COX-1 deficiency restored the normal onset of labor by allowing luteolysis in the absence of elevated PGF2alpha production. These findings demonstrate that COX-1 is essential for normal labor in the mouse, with a critical function being to overcome the luteotrophic action of oxytocin in late gestation.

Animals↗
PubMed1998

Glucocorticoid deficiency delays stratum corneum maturation in the fetal mouse.

The stratum corneum (SC) matures during late gestation in man and other mammals. Using the fetal rat as an experimental model, we have previously shown that glucocorticoids given in pharmacologic doses accelerate fetal SC maturation and barrier formation. To determine whether glucocorticoids are required for normal SC maturation, we examined the epidermal morphology of glucocorticoid-deficient (C-) murine pups, derived from matings of mice homozygous for null mutations of the corticotropin-releasing hormone alleles. In control pups on day 17.5 of gestation (term is 19.5 d), a multilayered SC was present and neutral lipid deposition in a membrane pattern was observed using Nile red fluorescence histochemistry. Ultrastructurally, mature lamellar unit structures predominate in the SC intercellular domains. In contrast, in C-pups only a single layer of SC was evident on day 17.5, and secreted lamellar material was not organized into mature lamellar structures. Furthermore, the expression of structural proteins necessary for cornified envelope formation, involucrin, loricrin, and filaggrin, and the activity of the lipid synthetic enzymes beta-glucocerebrosidase and steroid sulfatase, markers of barrier maturation, were reduced in day 17.5 C-pups. C-pups derived from pregnancies supplemented with physiologic amounts of cortisone, however, display normal SC ultrastructure on day 17.5 of gestation. Furthermore, at birth, both control and C-pups exhibit a multilayered SC replete with mature lamellar membrane structures. These data demonstrate that fetal glucocorticoid deficiency delays SC maturation, and suggests that normal levels of glucocorticoids are not absolutely required for SC development.

Animals↗
PubMed1997

Impaired diurnal adrenal rhythmicity restored by constant infusion of corticotropin-releasing hormone in corticotropin-releasing hormone-deficient mice.

The normal pattern of daily glucocorticoid production in mammals requires circadian modulation of hypothalamicpituitary-adrenal axis activity. To assess both the factors responsible for imparting this diurnal profile and its physiologic importance, we have exploited corticotropin-releasing hormone (CRH)-deficient mice generated by homologous recombination in embryonic stem cells. CRH-deficient mice have lost normal circadian variations in plasma ACTH and glucocorticoid while maintaining normal circadian locomotor activity. Constant peripheral infusion of CRH produced marked diurnal excursions of plasma glucocorticoid, indicating that CRH acts in part as a permissive factor for other circadian modulators of adrenocortical activity. The presence of atrophic adrenals in CRH-deficient mice without an overt deficit in basal plasma ACTH concentration suggests that the diurnal increase in ACTH is essential to maintain normal adrenal function.

Adrenal Cortex↗
PubMed1997

CRH and the immune system.

Inflammatory cytokines released during immune system activation can stimulate the hypothalamic-pituitary-adrenal axis and cause increased secretion of corticotropin-releasing hormone (CRH), adrenocorticotropin and glucocorticoids. Identification of CRH peptide and mRNA, as well as its receptors in immune tissues, suggested a role for this peptide as a mediator of the neuroendocrine-immune interactions. Experimental evidence suggests that CRH may modulate the immune and inflammatory responses via two pathways: an antiinflammatory one operated by centrally released CRH, most likely through stimulation of glucocorticoid and catecholamine release, and one proinflammatory, through direct action of peripherally released CRH. This review highlights these concepts. In addition preliminary data on immune activation and inflammatory response in CRH-deficient mice created in our laboratory are discussed.

Animals↗
PubMed1996

Knockout mice.

Explore the source record for details and available documents.

Animals↗
PubMed1994

Expression of the mouse corticotropin-releasing hormone gene in vivo and targeted inactivation in embryonic stem cells.

Corticotropin-releasing hormone (CRH), one of the primary regulators of the hypothalamic-pituitary-adrenal (HPA) axis, exhibits abnormal regulation in pathologic states such as depression and anorexia nervosa. Analysis of the role of CRH in regulation of the HPA axis would be facilitated by the creation of animal models in which CRH gene structure and function could be manipulated. We have determined the DNA sequence of the mouse CRH gene. Using a highly sensitive reverse transcription-polymerase chain reaction method, we have found expression of CRH mRNA in adrenal, ovary, testis, gut, heart, anterior pituitary, lung, and spleen, in addition to cerebral cortex and hypothalamus. Within the spleen, CRH mRNA is localized specifically to T-lymphocytes. We mapped the chromosomal location of mouse CRH via interspecific mouse backcrosses to chromosome 3, which is not the site of any naturally occurring mutations consistent with CRH deficiency. Because of this, we inactivated a CRH allele in mouse embryonic stem (ES) cells by homologous recombination with a mutant mouse CRH gene lacking the entire coding region of preproCRH. Mice chimeric for each of two ES clones with an inactivated CRH allele are being used to generate animals with complete CRH deficiency.

Animals↗
PubMed1986

Chromatin fibers are left-handed double helices with diameter and mass per unit length that depend on linker length.

Four classes of models have been proposed for the internal structure of eukaryotic chromosome fibers--the solenoid, twisted-ribbon, crossed-linker, and superbead models. We have collected electron image and x-ray scattering data from nuclei, and isolated chromatin fibers of seven different tissues to distinguish between these models. The fiber diameters are related to the linker lengths by the equation: D(N) = 19.3 + 0.23 N, where D(N) is the external diameter (nm) and N is the linker length (base pairs). The number of nucleosomes per unit length of the fibers is also related to linker length. Detailed studies were done on the highly regular chromatin from erythrocytes of Necturus (mud puppy) and sperm of Thyone (sea cucumber). Necturus chromatin fibers (N = 48 bp) have diameters of 31 nm and have 7.5 +/- 1 nucleosomes per 10 nm along the axis. Thyone chromatin fibers (N = 87 bp) have diameters of 39 nm and have 12 +/- 2 nucleosomes per 10 nm along the axis. Fourier transforms of electron micrographs of Necturus fibers showed left-handed helical symmetry with a pitch of 25.8 +/- 0.8 nm and pitch angle of 32 +/- 3 degrees, consistent with a double helix. Comparable conclusions were drawn from the Thyone data. The data do not support the solenoid, twisted-ribbon, or supranucleosomal particle models. The data do support two crossed-linker models having left-handed double-helical symmetry and conserved nucleosome interactions.

Animals↗