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Biomedical subjects

B Mellström

Publications and source records attributed to B Mellström.

At least 37 records · Page 2Linked to original sources
PubMed1993

Molecular mechanisms of pain: serotonin1A receptor agonists trigger transactivation by c-fos of the prodynorphin gene in spinal cord neurons.

By using spinal cord neurons cultured in chemically defined medium, a double labeling procedure, and blockage with antisense oligonucleotides, we show that induction of c-fos and the subsequent transactivation of the prodynorphin gene are coupled events, triggered by serotonin1A receptor agonists. Addition of the specific 1A agonist 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT) to the culture, at concentrations similar to that needed for transactivation of the prodynorphin gene, also significantly increases cAMP levels. Furthermore, in rats depleted of serotonin by intrathecal administration of 5,7-dihydroxytryptamine, the induction of prodynorphin after noxious stimulation is dramatically decreased compared with the induction in sham-operated rats. These results suggest that the expression of the prodynorphin gene in spinal cord is under the control of the raphe-spinal efferents containing serotonin.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1993

Transcriptional response to cAMP in brain: specific distribution and induction of CREM antagonists.

Changes in cAMP levels are often associated with the modulation of neuronal function. The CREM gene encodes both antagonists and activators of the cAMP-dependent transcriptional response by alternative splicing. CREM transcripts in rat brain show a characteristic pattern of expression, being specific for the inner layer of the cerebral cortex, anterior thalamus, hippocampus, and hypothalamus. Strikingly, the CREM transcripts correspond to the antagonist isoforms in these areas, suggesting a down-regulatory role for CREM in brain; in contrast, the expression of CREM tau and CREB activators is more diffuse and generalized. In the supraoptic nucleus, CREM expression is induced after osmotic stimulus. Importantly, this demonstrates physiological inducibility of CREM, which is novel within the CRE/ATF family.

Animals↗
PubMed1993

Induction of CREM activator proteins in spermatids: down-stream targets and implications for haploid germ cell differentiation.

The cAMP-responsive element modulator (CREM) gene encodes a family of transcriptional regulators that bind to promoter sequences activated by increased intracellular cAMP levels. Both activators and repressors are generated by alternative splicing and alternative translational initiation. During the development of male germ cells, there is a switch in the transcripts generated by CREM. Specifically, from the prophase of meiosis, there is an increase in the CREM tau activator transcript. Here we present results showing that expression of the CREM activator protein is restricted to postmeiotic germ cells. We show that CREM tau is efficiently phosphorylated at a serine residue at position 117 by the protein kinase-A endogenous to germ cells, indicating that it constitutes a natural target of the adenylyl cyclase pathway during spermatogenesis. Phosphorylation of serine-117 turns CREM tau into a powerful activator. The rise in CREM tau protein coincides with the transcriptional activation of several genes. We show that CREM tau efficiently binds to CREs present in the promoters of these genes, suggesting that they could constitute down-stream targets of CREM. We have analyzed in more detail the regulation of one of these genes, the male germ cell-specific RT7. The RT7 promoter is cAMP inducible and activated by CREM tau in transfection assays. The RT7 promoter is efficiently transcribed in vitro with nuclear extracts from seminiferous tubules. CREM-specific antibodies block RT7 in vitro transcription, implicating a role for CREM tau in a cascade of transcriptional events during spermatogenesis.

Animals↗
PubMed1993

Distribution of insulin-like growth factor-I receptor mRNA in rat brain. Regulation in the hypothalamo-neurohypophysial system.

The distribution and regulation of mRNA for the IGF-I receptor (IGF-I-R) in the adult rat brain were studied by in-situ hybridization with a 35S-labelled cRNA probe. The pituitary gland showed a strong hybridization signal in the pars tuberalis (the surface of the median eminence), pars distalis and pars intermedia. Within the brain, a strong hybridization signal was found in the circumventricular organs, olfactory bulb, hippocampus, cerebellum and hypothalamus. IGF-I-R mRNA was consistently found in cell bodies of the hypothalamo-neurohypophysial system. Six days of intermittent salt-loading resulted in an increase in IGF-I-R gene expression in the supraoptic nucleus. The increase in IGF-I-R mRNA was accompanied by a high expression of c-Fos immunoreactivity in the same cells. The presence and regulation of IGF-I-R mRNA in the hypothalamus suggest that IGF-I may affect the local plasticity or modulation of activated magnocellular neurones by an autocrine or paracrine action through specific receptors in the hypothalamo-neurohypophysial system.

Animals↗
PubMed1992

Developmental switch of CREM function during spermatogenesis: from antagonist to activator.

Mammalian spermatogenesis consists of a series of complex developmental processes controlled by the pituitary-hypothalamic axis. This flow of biochemical information is directly regulated by the adenylate cyclase signal transduction pathway. We have previously described the CREM (cyclic AMP-responsive element modulator) gene which generates, by cell-specific splicing, alternative antagonists of the cAMP transcriptional response. Here we report the expression of a novel CREM isoform (CREM tau) in adult testis. CREM tau differs from the previously characterized CREM antagonists by the coordinate insertion of two glutamine-rich domains that confer transcriptional activation function. During spermatogenesis there was an abrupt switch in CREM expression. In premeiotic germ cells CREM is expressed at low amounts in the antagonist form. Subsequently, from the pachytene spermatocyte stage onwards, a splicing event generates exclusively the CREM tau activator, which accumulates in extremely high amounts. This splicing-dependent reversal in CREM function represents an important example of developmental modulation in gene expression.

Aging↗
PubMed1992

Fos-like expression and nuclear size in osmotically stimulated supraoptic nucleus neurons.

This study has analysed by immunocytochemistry the pattern of expression of Fos-related proteins, as well as variations in nuclear size, after the osmotically induced activation of supraoptic nucleus neurons of the rat. In control rats most supraoptic nucleus neurons were Fos-like negative. After acute and chronic dehydration by salt-loading, the number of Fos-like positive neurons increased dramatically. The level of Fos-like immunoreactivity was higher in chronically stimulated rats, and also the neurons of the ventral region of the supraoptic nucleus were more intensely stained than those of the dorsal region. The karyometric analysis was made on electron micrographs. The mean nuclear profile area showed a significant increase in dehydrated rats with respect to the controls (73 +/- 16 microns 2 in those dehydrated for six days vs 54 +/- 13 in controls, mean +/- S.D.). However, no significant differences in this parameter were found when one-day and six-day dehydrated groups were compared. The invagination factor of the nuclear membrane, a nuclear shape indicator, decreased significantly in dehydrated rats, indicating a tendency towards spherical nuclei. It is noteworthy that the nuclear profile perimeter was constant, about 32 microns, in control and osmotically simulated rats. The higher nuclear accumulation of Fos-related antigens after six days of dehydration suggests that in chronically stimulated supraoptic nucleus neurons there is a sustained induction of cell-specific genes. Moreover, the transcription rate of the target genes containing the consensus DNA sequence TGAC/GTCA or c-AMP responsive elements recognition sites may depend upon the nuclear concentration of Fos-related antigens in supraoptic nucleus neurons. Our results also suggest that the initial Fos-related antigen expression and nuclear size increase are triggered concomitantly in supraoptic nucleus neurons after a short period of osmotic stimulation. On the other hand, we propose that nuclear envelope invaginations represent a reservoir of nuclear membrane which allows dynamic changes in nuclear size and shape depending on the metabolic status of the supraoptic nucleus neurons.

Animals↗
PubMed1992

Narine occlusion decreases basal levels of Fos protein in the cerebral cortex of the lizard Podarcis hispanica.

Immunocytochemical study of cerebral cortex of the lizard Podarcis hispanica using an antibody directed to the M peptide of the rat c-Fos protein showed a distinct pattern of Fos distribution. Abundant Fos-immunoreactive neuronal nuclei were detected in the cell layers of the medial, the dorsal and the lateral cortices, whereas only a few nuclei were found in the cell layer of the dorsomedial cortex. The Fos immunoreactivity was characterized by Western blot analysis of nuclear extracts from lizard brain and showed a distinct band with an apparent molecular weight of 30,000. In band-shift assays, nuclear extracts from lizard brain were shown to contain AP-1 complexes. The basal expression of Fos immunoreactivity is related to sensory olfactory input in the cerebral cortex of the lizard since experiments with olfactory-deprived animals resulted in a complete absence of Fos immunoreactivity in the cortical areas.

Animals↗
PubMed1991

Transient expression of c-fos during the development of the rat cerebral cortex.

The present study has explored with immunocytochemical methods the expression of the proto-oncogene c-fos during the pre- and postnatal development of the cerebral cortex of the rat. The immunostaining of the Fos protein follows a strikingly precise spatiotemporal pattern: it occurs uniquely within layer VIb of the developing cerebral cortex, and is transient, lasting only from embryonic day 20 until postnatal day 1. The expression of c-fos in layer VIb may be related to the dynamic changes that occur at this level during development.

Animals↗
PubMed1991

Molecular pathways of pain: Fos/Jun-mediated activation of a noncanonical AP-1 site in the prodynorphin gene.

Noxious stimulation provokes the activation of genes that are thought to play a crucial role in the phenomena of stress and pain. Among these is the prodynorphin gene. By double-labeling in situ hybridization/immunohistochemistry, we show that increased prodynorphin gene expression is preceded, in the same neurons, by an early induction of c-fos. Inspection of the prodynorphin promoter region revealed the presence of several AP-1-like sequences. We demonstrate that only one of these sites is a functional AP-1 element. It is constituted by the noncanonical TGACAAACA sequence, in which the palindromic structure is partly conserved by the 3' terminal CA dinucleotide. Transfection experiments in NCB20 neuroblastoma cells indicated that this site is a target of Fos/Jun trans-activation. Our results suggest that Fos/Jun oncoproteins may function as third messengers in the signal transduction mechanisms of stress/pain processes.

Amino Acid Sequence↗
PubMed1991

Independent expression of the alpha and beta c-erbA genes in developing rat brain.

Thyroid hormone is important for normal brain development. Cellular responses to thyroid hormone are mediated by multiple nuclear receptors, classified into alpha- and beta-subtypes. In the rat, expression of both the alpha and beta genes results in several translation products. By using cRNA probes common to alpha transcripts or specific for alpha-1 and beta-1, we have studied the distribution of these transcripts in rat brain at different stages of development from embryonic day 14 to adult age by using in situ hybridization histochemistry. On embryonic day 14, the alpha-1 mRNA is already widely expressed at a low level in the developing brain. The alpha-1 mRNA is developmentally regulated and showed a peak in expression during the first 3 postnatal weeks in the cerebral cortex, amygdala, hippocampus, and cerebellum. The probe common to the alpha transcripts detected a widespread distribution and high levels of these forms in the same regions throughout postnatal development. The level of beta-1 mRNA before birth was low or undetectable. The beta-1 transcript showed developmental regulation as well, with a high level at birth in the mitral cell layer of the olfactory bulb, accumbens nucleus, caudate, and hippocampal field CA1 and increasing levels in other regions later during development. Complementary expression of the alpha and beta forms was seen in the cerebral cortex and hippocampus. The differential temporal and spatial distribution as well as coexpression at comparable levels in certain brain regions suggest different roles for the c-erbA proteins during brain development and in the mature animal.

Age Factors↗
PubMed1991

Differential expression of the jun family members in rat brain.

The transcription factor AP-1 is phorbol ester-regulated and, as such, is considered to be a nuclear target of the signal transduction pathway involving protein kinase C. AP-1 is constituted by the various products of the jun and fos gene family members. These genes belong to the early response class and are inducible in different ways by growth factors, phorbol esters and depolarization. We studied the transcript distribution of c-jun, junB and junD in the rat brain. Our results show that the transcripts for these three genes are differentially distributed in various neuronal tissues. We also provide evidence for developmentally regulated expression of jun genes in post-natal brain. The spatiotemporal pattern of expression of c-jun, junB and junD offers clues to the understanding of the links between gene regulation and neuronal processes.

Aging↗
PubMed1991

Co-induction of jun B and c-fos in a subset of neurons in the spinal cord.

Noxious stimulation in vivo provokes the transcriptional activation of several genes which are thought to play an important role in the phenomena of stress and pain. In the rat, the expression of the c-fos proto-oncogene is rapidly induced upon noxious stimulation in defined neurons in the dorsal horn of the spinal cord. Interestingly, expression of the prodynorphin gene, which is thought to be involved in the endogenous mechanisms for pain/stress control, also localizes in the same anatomical area. Fos proteins are known to associate in transcriptional complexes with the products of the jun family constituting nuclear factor AP-1. These considerations prompted us to analyse the expression of the jun gene family members c-jun, jun B and jun D in rats subjected to noxious stimulation. We present data indicating that in unstimulated animals the transcripts of the three genes are differentially expressed and abundant within the various laminas of the lumbar spinal cord. Surprisingly, upon stimulation only the jun B transcript is augmented, being co-localized with Fos in a subset of neurons of the medial dorsal horn.

Animals↗
PubMed1990

Unusual c-fos induction upon chromaffin PC12 differentiation by sodium butyrate: loss of fos autoregulatory function.

Induction of PC12 pheochromocytoma cells neuronal differentiation upon treatment with nerve growth factor (NGF) is accompanied by a coupled stimulation of c-fos and c-jun oncogene transcription. We found that induction of c-fos and c-jun proto-oncogene mRNAs levels following the endocrine differentiation of PC12 cells by sodium butyrate is uncoupled. While c-fos mRNA level increased within minutes, the content of c-jun mRNA was significantly elevated only 24 hours after treatment. Continuous presence of sodium butyrate for 72 hours resulted in stable high levels of c-fos and c-jun mRNAs. Gene transcription of the other members of the jun family, jun B and jun D, was not significantly modified at any induction time. The early accumulation of c-fos mRNA was accompanied by increased levels of c-Fos protein. While the NGF-induced c-Fos protein migrates with an apparent homogeneous molecular weight of 62 kDa, the sodium butyrate-stimulated Fos protein is of heterogeneous lower molecular weight. The different gel mobility of the Fos immunoreactive bands induced by sodium butyrate and the sustained Fos mRNA levels after induction suggested that the sodium butyrate-induced c-Fos protein could be non-functional in the autoregulation of the c-fos gene. Gel shift analysis showed unimpaired capacity of the butyrate-induced c-Fos protein to participate in the formation of transcriptional complexes with the Jun/AP-1 protein. However, transfection experiments indicate that the sodium butyrate-induced c-Fos protein is not able to negatively trans-regulate the c-fos promoter.

Adrenal Gland Neoplasms↗
PubMed1986

Amitriptyline metabolism: association with debrisoquin hydroxylation in nonsmokers.

Eleven healthy nonsmokers with wide variation in the ability to hydroxylate debrisoquin (D) were given single oral doses of amitriptyline and nortriptyline on different occasions. The urinary D/4-hydroxy-D ratio correlated significantly (P less than 0.01) with all three parameters of amitriptyline disposition measured (total plasma clearance, clearance by demethylation, and clearance by pathways other than demethylation), with rs = -0.89, -0.78, and -0.83, respectively. In contrast, we failed to demonstrate such correlations in a previous sample of smokers. Our data suggest that there may be a common regulation of the hydroxylation of D and the oxidative metabolism of amitriptyline in nonsmokers. It is hypothesized that an additional demethylase/hydroxylase is induced in smokers that is not involved in D hydroxylation.

Administration, Oral↗
PubMed1985

Clomipramine treatment of childhood obsessive-compulsive disorder. A double-blind controlled study.

Nineteen children (mean [+/- SD] age, 14.5 +/- 2.3 years) with severe, primary obsessive-compulsive disorder completed a ten-week, double-blind, controlled trial of clomipramine hydrochloride (mean dosage, 141 mg/day) or placebo, each of which was administered for five weeks. Half of the subjects had not responded to previous treatment with other tricyclic antidepressants. There was a significant improvement in observed and self-reported obsessions and compulsions that was independent of the presence of depressive symptoms at baseline. Improvement in obsessive-compulsive symptoms did not correlate significantly with plasma concentrations of the drug or its metabolites. Clomipramine appears to be effective in the treatment of children with obsessive-compulsive disorder and the treatment seems to be independent of an antidepressant effect.

Adolescent↗
PubMed1985

Comparative metabolism of debrisoquine, 7-ethoxyresorufin and benzo(a)pyrene in liver microsomes from humans, and from rats treated with cytochrome P-450 inducers.

The metabolism of debrisoquine, 7-ethoxyresorufin and benzo(a)pyrene has been studied in human liver microsomes. There was a significant correlation (r = 0.70, P less than 0.05) between debrisoquine hydroxylation and 7-ethoxyresorufin 0-deethylation among various livers, and debrisoquine inhibited 7-ethoxyresorufin deethylation competitively. These results suggest that debrisoquine and 7-ethoxyresorufin may be metabolised by a common P-450 form in human liver. The effect of cytochrome P-450 inducers on the metabolism of the three substrates was also examined in rat liver. Debrisoquine hydroxylation was not enhanced by phenobarbitone, beta-naphthoflavone or isosafrole.

Animals↗
PubMed1984

Nortriptyline and debrisoquine hydroxylations in Ghanaian and Swedish subjects.

Eleven Ghanaian and 12 Swedish subjects phenotyped with a debrisoquine (D) hydroxylation test were given a single oral dose of nortriptyline (NT). Much the same percentage of the given NT dose was excreted as 10-hydroxy-NT (10-OH-NT) by Ghanaians (43.1%) and Swedes (49.2%). There was a close correlation between plasma clearance of NT by 10-hydroxylation and the D metabolic ratio (D/4-OH-D in urine) in the Ghanaians (rs = -0.95; P less than 0.01) and Swedes (rs = -0.84; P less than 0.01). The E-isomer of 10-OH-NT is the major isomer in both Ghanaians (76% to 92% of total 10-OH-NT) and Swedes (78% to 95%). It is suggested that the E-10-hydroxylation of NT and the 4-hydroxylation of D are similarly coregulated in Ghanaians and Swedes.

Administration, Oral↗