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C A Fox

Publications and source records attributed to C A Fox.

At least 37 records · Page 2Linked to original sources
PubMed1994

Nuclear polyadenylation factors recognize cytoplasmic polyadenylation elements.

In the cytoplasm of oocytes and early embryos, addition of poly(A) to mRNAs can activate their translation. We demonstrate that despite many differences between poly(A) addition in the cytoplasm and nucleus, these two forms of polyadenylation may involve identical trans-acting factors. Nuclear polyadenylation requires the sequence AAUAAA, the AAUAAA-binding cleavage and polyadenylation specificity factor (CPSF), and a poly(A) polymerase (PAP). We show that CPSF and PAP, purified from calf thymus, exhibit the same sequence specificity observed in the cytoplasm during frog oocyte maturation, requiring both AAUAAA and a proximal U-rich sequence. The enhanced polyadenylation of RNAs containing U-rich sequences is caused by their increased affinity for CPSF. Frog nuclear polyadenylation factors display cytoplasmic sequence specificity when dilute, suggesting that a difference in their concentrations in the nucleus and cytoplasm underlies the different sequence specificities in the two compartments. Because polyadenylation in extracts prepared from oocytes before maturation is stimulated by addition of CPSF, the onset of polyadenylation during early development may be attributable to the activation or synthesis of a CPSF-like factor. We suggest that sequences upstream of AAUAAA that are required for cleavage and polyadenylation of certain pre-mRNAs in the nucleus may be functionally equivalent to the upstream, U-rich sequences that function in the cytoplasm, enhancing CPSF binding. We propose that CPSF and PAP comprise a core polyadenylation apparatus in the cytoplasm of oocytes and early embryos.

Animals↗
PubMed1994

mu-Opioid receptor mRNA expression in the rat CNS: comparison to mu-receptor binding.

The distribution of cells expressing mu-receptor mRNA and mu-receptor binding sites were compared in brain and spinal cord tissue sections using a combination of in situ hybridization and receptor autoradiographic techniques. mu-Receptor mRNA was visualized with a 35S-labeled cRNA probe directed to transmembrane III-VI of the rat mu-receptor, while mu-receptor binding sites were labeled with the mu-selective ligand [3H]DAMGO. A high correspondence between the mu-receptor mRNA and receptor binding distributions was observed in the nucleus of the accessory olfactory bulb, anterior olfactory nuclei, striatal patches of the nucleus accumbens and caudate-putamen, endopiriform nucleus, claustrum, diagonal band of Broca, globus pallidus, ventral pallidum, bed nucleus of stria terminalis, most thalamic nuclei, medial and posteriocortical medial amygdala, lateral, dorsomedial, posterior and mammillary nuclei of the hypothalamus, presubiculum, subiculum, rostral interpeduncular nucleus, median raphe, inferior colliculus, parabrachial nucleus, locus coeruleus, central grey, nucleus ambiguus, nucleus of the solitary tract, nucleus gracilis, nucleus cuneatus, and the dorsal motor nucleus of vagus. Differences in mu-receptor mRNA and receptor binding distributions were observed in several regions, including the olfactory bulb, cortex, hippocampus, superior colliculus, spinal trigeminal nucleus, cochlear nucleus and spinal cord, and may be due to mu-receptor transport to presynaptic terminals.

Animals↗
PubMed1994

The 3'-untranslated regions of c-mos and cyclin mRNAs stimulate translation by regulating cytoplasmic polyadenylation.

Early in the development of many animals, before transcription begins, any change in the pattern of protein synthesis is attributable to a change in the translational activity or stability of an mRNA in the egg. As a result, translational control is critical for a variety of developmental decisions, including axis formation in Drosophila and sex determination in Caenorhabditis elegans. Previous work demonstrated that increases in poly(A) length can activate translation, whereas removal of poly(A) can prevent it. In this report we focus on the control of c-mos and cyclin A1, B1, and B2 mRNAs during meiotic maturation and after fertilization of frog eggs. We show that addition and removal of poly(A) from these mRNAs is extensively regulated: The time at which each mRNA receives or loses poly(A), as well as the number of adenosines it gains or loses, differ substantially. Signals in the 3'-untranslated region (UTR) of each mRNA are sufficient to reconstitute both the temporal and quantitative control of poly(A) addition: Chimeric mRNAs in which a luciferase-coding region is joined to the 3' UTRs of cyclin A1, cyclin B1, or c-mos mRNA, receive poly(A) of the same length and at the same time as do the endogenous mRNAs. Moreover, each 3' UTR also regulates translation of the chimeric mRNAs, determining when and how much translation of the luciferase reporter is stimulated during maturation. The magnitude of stimulation in luciferase activity varies from 5- to 100-fold, depending on the 3' UTR. Translational stimulation by each 3' UTR requires poly(A) lengthening, as it is prevented by mutations that prevent that process. These results suggest that the 3' UTRs of cyclin and c-mos mRNAs control not only whether or not an mRNA is turned on during maturation, but when that activation occurs and to what extent. Translational control of c-mos mRNA, which may be achieved through regulation of poly(A) length, may be critical in the activation of maturation, and in the onset of cleavage divisions. Our findings, as well as those of others, suggest that even quite complex patterns of translational activation in the early embryo can be attained through the differential control of a common mechanism.

Animals↗
PubMed1994

The effects of haloperidol on dopamine receptor gene expression.

Haloperidol is a widely prescribed antipsychotic that acts as a dopamine D2 receptor antagonist. Chronic administration of haloperidol leads to an increase in striatal D2 receptor binding; however, studies examining striatal D2 receptor mRNA after haloperidol treatment report inconsistent results. This study examines the effects of haloperidol on dopaminoceptive striatal neurons, as well as dopamine D2 containing striatal inputs. Rats were injected subcutaneously with 2 mg/kg haloperidol twice daily for 7 days. A significant (36%) increase in D2 mRNA was observed in the anterior cingulate cortex. However, no changes were observed in the amounts of D1, D2, D3 mRNA, or D2 heteronuclear RNA (hnRNA) in the striatum or in the levels of D2 mRNA and hnRNA in the substantia nigra and ventral tegmental area. Thus, increased striatal D2 binding after haloperidol treatment may not be the result of altered D2 gene activity in the striatum or midbrain, but could result from an increase in D2 mRNA in cingulate corticostriatal neurons and/or a longer half-life for the D2 receptor protein in striatal neurons. Striatal proenkephalin mRNA increased significantly in the caudate-putamen (45%), nucleus accumbens (36%), and the olfactory tubercle (27%) while prodynorphin mRNA remained unaltered after haloperidol treatment. Since D2 receptor mRNA is generally colocalized with proenkephalin mRNA in striatal neurons, these results demonstrate what is likely a selective cellular increase in proenkephalin mRNA without a parallel increase in D2 mRNA.

Animals↗
PubMed1994

Kappa 1 receptor mRNA distribution in the rat CNS: comparison to kappa receptor binding and prodynorphin mRNA.

Three opioid receptor types have been identified in the CNS and periphery that are referred to as mu, delta, and kappa. The present study examines the mRNA distribution of the kappa 1 receptor in the rat brain and compares it to the distribution of kappa receptor-binding sites and prodynorphin mRNA using a combination of in situ hybridization and receptor autoradiographic techniques. kappa 1 receptor mRNA was localized with a cRNA probe generated with a BamHI-HindIII cDNA fragment of the rat kappa 1 receptor and corresponds to the last 45 bp of the protein coding region and 728 nucleotides of the 3' untranslated region. Prodynorphin mRNA was localized with a cRNA probe corresponding to a 733-bp BamHI-HincII fragment of prodynorphin. kappa receptor-binding sites were labeled in one of two ways: [3H]U69,593 or [3H]bremazocine in the presence of a 300-fold excess of DAMGO and DPDPE. A high degree of correspondence between the kappa 1 receptor mRNA and kappa receptor binding was observed in several brain regions, including the endopiriform nucleus, claustrum, nucleus accumbens, olfactory tubercle, bed nucleus of the stria terminalis, medial preoptic area, paraventricular, supraoptic, suprachiasmatic, dorsomedial and ventromedial hypothalamic nuclei, basolateral, medial and cortical amygdaloid nuclei, midline thalamic nuclei, periaqueductal grey, parabrachial nucleus, locus coeruleus, and the nucleus of the solitary tract. Differences in the localization of kappa 1 receptor mRNA and binding and the relationship between the distribution of kappa 1 receptor and prodynorphin mRNAs are discussed.

Animals↗
PubMed1992

Galanin-like immunoreactivity in the adult and developing Brazilian opossum brain.

The distribution of galanin-like immunoreactivity has been characterized in the brain of the adult and developing Brazilian opossum (Monodelphis domestica). Two commercially available antisera were used to examine the distribution of galanin-like immunoreactive (GAL-IR) cells and fibers. Nuclear groups containing GAL-IR cell bodies and fibers were seen throughout the adult opossum brain. The distribution of GAL-IR elements seen is similar to that reported for other mammals. Based on these findings, we believe that galanin may have similar physiological functions in the adult Brazilian opossum as has been reported for other mammals. In the developing brain, GAL-IR structures were seen as early as 1 day postnatal (PN) in the developing hypothalamus and brainstem. By days 5 and 10 PN, there was a robust expression of galanin-like immunoreactivity in specific regions of the brain. Since neurogenesis and brain morphogenesis are actively occuring postnatally in the opossum, galanin may be playing a role in the differentation of specific regions of the brain.

Aging↗
PubMed1992

Polyadenylation of maternal mRNA during oocyte maturation: poly(A) addition in vitro requires a regulated RNA binding activity and a poly(A) polymerase.

Specific maternal mRNAs receive poly(A) during early development as a means of translational regulation. In this report, we investigated the mechanism and control of poly(A) addition during frog oocyte maturation, in which oocytes advance from first to second meiosis becoming eggs. We analyzed polyadenylation in vitro in oocyte and egg extracts. In vivo, polyadenylation during maturation requires AAUAAA and a U-rich element. The same sequences are required for polyadenylation in egg extracts in vitro. The in vitro reaction requires at least two separable components: a poly(A) polymerase and an RNA binding activity with specificity for AAUAAA and the U-rich element. The poly(A) polymerase is similar to nuclear poly(A) polymerases in mammalian cells. Through a 2000-fold partial purification, the frog egg and mammalian enzymes were found to be very similar. More importantly, a purified calf thymus poly(A) polymerase acquired the sequence specificity seen during frog oocyte maturation when mixed with the frog egg RNA binding fraction, demonstrating the interchangeability of the two enzymes. To determine how polyadenylation is activated during maturation, we compared polymerase and RNA binding activities in oocyte and egg extracts. Although oocyte extracts were much less active in maturation-specific polyadenylation, they contained nearly as much poly(A) polymerase activity. In contrast, the RNA binding activity differed dramatically in oocyte and egg extracts: oocyte extracts contained less binding activity and the activity that was present exhibited an altered mobility in gel retardation assays. Finally, we demonstrate that components present in the RNA binding fraction are rate-limiting in the oocyte extract, suggesting that fraction contains the target that is activated by progesterone treatment. This target may be the RNA binding activity itself. We propose that in spite of the many biological differences between them, nuclear polyadenylation and cytoplasmic polyadenylation during early development may be catalyzed by similar, or even identical, components.

Animals↗
PubMed1991

Ontogeny of cholecystokinin-like immunoreactivity in the Brazilian opossum brain.

We have studied the anatomical distribution of cholecystokinin-like immunoreactive (CCK-IR) somata and fibers in the brain of the adult and developing Brazilian short-tailed opossum, Monodelphis domestica. Animals ranged in age from the day of birth (1PN) to young adulthood (180PN). A nickel enhanced, avidin-biotin, indirect immunohistochemical technique was used to identify CCK-IR structures. Somata containing CCK immunoreactivity were observed in the cerebral cortex, hippocampus, hypothalamus, thalamus, midbrain, and brainstem in the adult. Cholecystokinin immunoreactive fibers had a wide distribution in the adult Monodelphis brain. The only major region of the brain that did not contain CCK-IR fibers was the cerebellum. The earliest expression of CCK immunoreactivity was found in fibers in the dorsal brainstem of 5-day-old opossum pups. It is possible that the CCK-IR fibers in the brainstem at 5PN are of vagal origin. Cholecystokinin immunoreactive somata were observed in the brainstem on 10PN. The CCK-IR cell bodies observed in the brainstem at 10PN may mark the first expression of CCK-IR elements intrinsic to the brain. A broad spectrum of patterns of onset of CCK expression was observed in the opossum brain. The early occurrence and varied ontogenesis of CCK-IR structures indicates CCK may be involved in the function of a variety of circuits from the brainstem to the cerebral cortex. The early expression of CCK-IR structures in the dorsal brainstem suggests that CCK may modulate feeding behavior in the Monodelphis neonate. Cholecystokinin immunoreactivity in forebrain structures such as the suprachiasmatic nucleus, medial preoptic area, thalamus and cortical structures indicates that CCK may also be involved in circadian rhythmicity, reproductive functions, as well as the state of arousal of the Brazilian opossum. The ontogenic timing of CCK immunoreactivity in specific circuitry also indicates that CCK expression does not occur simultaneously throughout the brain. This pattern of CCK onset may relate to the temporal need for CCK in specific circuits of the central nervous system (CNS) during development.

Aging↗
PubMed1991

Ontogeny of cells containing estrogen receptor-like immunoreactivity in the Brazilian opossum brain.

In this study, we have used the Brazilian short-tailed opossum (Monodelphis domestica) as a model to study the ontogeny of estrogen receptors in the mammalian brain. Monodelphis is a small, pouchless marsupial which breeds well under laboratory conditions and whose young are born in an immature sexually undifferentiated state. The Abbott H222 monoclonal rat estrogen receptor antibody (gift of Abbott Laboratories) was utilized in an indirect immunohistochemical procedure to detect estrogen receptors in developing opossum brains. Estrogen receptors were first expressed in the dorsomedial and ventromedial hypothalamus of the opossum 10 days after birth (10PN). Most regions that contained estrogen receptor-like immunoreactivity (ER LI) in the adult opossum contained ER LI at 15 PN. These areas include the lateral septum, medial preoptic area, bed nucleus of the stria terminalis, periventricular preoptic area and hypothalamus, amygdala, dorsomedial and ventromedial hypothalamic nuclei, arcuate nucleus, ventral premammillary nucleus, and the midbrain central grey. The number of cells that contain ER LI increased through 60PN in all regions that will contain ER LI in the adult opossum. These results indicate that estrogen receptors are present in early development of the Monodelphis brain and may mark the beginning of a critical period for sexual differentiation of the opossum brain.

Animals↗
PubMed1991

Localization of cells containing estrogen receptor-like immunoreactivity in the Brazilian opossum brain.

The Brazilian opossum (Monodelphis domestica) is a small, pouchless marsupial whose young are born in an immature, sexually undifferentiated state. Etgen and Fadem, and Handa and coworkers have biochemically detected and characterized estrogen receptors in the forebrain of the Brazilian opossum. In this study, we have examined the distribution of estrogen receptor-like immunoreactive (ER-LI) cells in the brains of gonadectomized male and female Brazilian opossums using Abbott H222 rat monoclonal estrogen receptor antibody (H222 is a gift of Abbott Labs). An indirect immunohistochemical procedure employing the Vectastain Elite system and a nickel-enhanced DAB chromogen was used. A large number of ER-LI cell nuclei were observed in the medial preoptic area, ventral septal nucleus, medial division of the bed nucleus of the stria terminalis, lateral part of the ventromedial hypothalamus, premammillary nucleus, arcuate nucleus, posterior amygdaloid nucleus, and the midbrain central grey. Lower numbers of ER-LI cell nuclei were observed in the intermediate subdivision of the lateral septal nucleus, and in the anterior, medial, and posterior cortical amygdaloid nuclei. The anatomical distribution of ER-LI in the Brazilian opossum brain is similar to that which has been reported for estrogen binding sites following biochemical analysis. Based on these findings, we believe specific regions of the Brazilian opossum brain may serve as substrata for the action of estrogen in the adult. In addition, these results are supportive of the use of this animal model to investigate the organizational effects of estrogen on the developing central nervous system.

Animals↗
PubMed1991

Characterization and distribution of estrogen receptors in the diencephalon of the gray short-tailed opossum.

The Brazilian gray short-tailed opossum is a pouchless marsupial whose young are born sexually undifferentiated making this animal ideal for developmental studies. Previously, Etgen and Fadem (Dev. Brain Res., 49 (1989) 131-133; Gen. Comp. Endocrinol., 66 (1987) 441-446) detected estrogen receptor (ER) in the hypothalamus-preoptic area, and compared males and females in the adult and during development. In this study we characterized the ER and determined its distribution in specific diencephalic regions in the brains of adult male and female opossums. ER were measured by the in vitro binding of [3H]estradiol to cytosol of microdissected brain nuclear regions. Radioinert moxestrol (R2858) was used to define non-specific binding. Saturation analysis showed a single high-affinity binding site. Binding was displaced by estradiol (E2), diethylstilbestrol (DES) and R2858, but not by non-estrogenic steroids. Ligand bound receptor adhered to DNA-cellulose and was eluted as a single peak with 0.2-0.3 M NaCl. High levels of ER were found in the medial preoptic-periventricular area. Intermediate levels were seen in the ventromedial hypothalamic nucleus, medial amygdala and arcuate nucleus. No sex differences were observed. The presence of a neural ER and its similarity of distribution to that of the laboratory rat support the use of this animal model in studies examining steroid dependent organization of the hypothalamus.

Animals↗
PubMed1991

The Berkeley Group: ten years' experience of a group for non-violent sex offenders.

During the first ten years of a group started in February 1977 by the Avon Probation Service for the treatment of non-violent sex offenders, many of the offenders have shown a high degree of commitment to the group, and attendance levels have run consistently at over 70%. Of 63 men who came to the group during the ten-year study period, 33 completed their stay at the group, 11 left the group prematurely, and 11 never engaged satisfactorily. The remaining eight were still attending the group at the end of the study period. Of the 55 men whose contact with the group had ended, 36 (65%) had not been convicted of further sex offences by the end of the study period.

Adult↗
PubMed1990

Immunohistochemical localization of cholecystokinin in the medial preoptic area and anterior hypothalamus of the Brazilian gray short-tailed opossum: a sex difference.

We have studied the anatomical localization of cholecystokinin-like immunoreactivity (CCK IR) in somata and fibers in the medial preoptic area (MPA) and anterior hypothalamus (AH) of the Brazilian gray short-tailed opossum, (Monodelphis domestica). With the aid of an avidin-biotin, nickel-enhanced, immunohistochemical technique, CCK IR neuronal elements were found within the MPA and AH. A large number of CCK IR cell bodies were located in the MPA of colchicine-treated opossums. The MPA also contained a CCK IR fiber plexus. Quantitative image analysis revealed that the periventricular preoptic area of noncolchicine-treated male opossums had a significantly higher percent of blocked light measurements than that of the noncolchicine-treated females, indicating a higher density of CCK IR neuronal elements in the males. Neuronal fibers and somata containing CCK IR were also found within the periventricular hypothalamic nucleus (Pe), and the suprachiasmatic nucleus (SCh). These results show that CCK IR neuronal elements are found within the MPA and AH of the Brazilian short-tailed opossum. Furthermore, there is a sexually dimorphic distribution of CCK IR elements within the MPA of this small marsupial.

Animals↗
PubMed1990

Poly(A) removal during oocyte maturation: a default reaction selectively prevented by specific sequences in the 3' UTR of certain maternal mRNAs.

Certain maternal mRNAs lose their poly(A) tails during early development and concomitantly become translationally inactive. In this report we analyze the mechanism of poly(A) removal during frog oocyte maturation by injecting short synthetic RNAs. We demonstrate that removal of poly(A) during oocyte maturation is a default reaction: In the absence of any specific sequence information, poly(A) is removed. However, poly(A) removal can be prevented by specific sequences in the 3'-untranslated regions of certain maternal mRNAs. These sequences are also required for poly(A) addition during oocyte maturation and include AAUAAA and a nearby U-rich element. Mutations in either AAUAAA or the U-rich element cause loss of poly(A) and not merely a failure to extend the poly(A) tail. We infer that poly(A) addition is required to escape poly(A) loss. The enzyme that removes the poly(A) during oocyte maturation appears to be a 3'----5' nuclease that prefers a 3'-terminal poly(A) segment. We discuss possible mechanisms by which poly(A) addition might circumvent default poly(A) removal and consider whether poly(A) removal is also a default reaction in somatic cells. Finally, we consider the possible implications of our results for the selectivity of poly(A) addition and removal, and for translational regulation during early development.

Animals↗
PubMed1989

Poly(A) addition during maturation of frog oocytes: distinct nuclear and cytoplasmic activities and regulation by the sequence UUUUUAU.

In frog oocytes, certain maternal mRNAs receive poly(A) in the cytoplasm during progesterone-induced maturation. To analyze this reaction and to compare it to poly(A) addition in the nucleus, we injected short, synthetic RNA substrates into Xenopus oocytes. These RNAs contain only portions of the 3'-untranslated regions of appropriate mRNAs and end at the natural poly(A) site. We demonstrate that the nuclear and maturation-specific polyadenylation activities are distinct in substrate specificity and subcellular location. The sequence AAUAAA, contained in virtually all pre-mRNAs, is necessary for both activities. A second sequence element, UUUUUAU, activates poly(A) addition during maturation. UUUUUAU and AAUAAA are both necessary and virtually sufficient for maturation-specific polyadenylation: Poly(A) tails of between 50 and 300 nucleotides are added during maturation to RNAs containing both sequences but not to RNAs that lack either sequence. Before maturation, RNAs that contain AAUAAA are extended by just 10 nucleotides, presumably adenosines. The maturation-specific activity first appears within 1 hr of the time the nucleus breaks down but apparently does not require a nuclear component, as it is unaffected by enucleation. These observations, combined with those of others, lead us to speculate that polyadenylation may be responsible for the translational activation of a family of mRNAs essential for maturation.

Animals↗
PubMed1988

Role of hydrogen in the activation and regulation of hydrogen oxidation by the soluble hydrogenase from Alcaligenes eutrophus H16.

The activation kinetics of the H2-oxidizing activity of the soluble hydrogenase from Alcaligenes eutrophus H16 were investigated. Activation with Na2S2O4 plus 101 kPa H2 resulted in a rapid increase in activity over 1 h and constant activity after 3 h incubation. Less-stable activations were achieved if enzyme was incubated with Na2S2O4 under 1 kPa H2 or 101 kPa N2. The enzyme could also be partly activated either with NADH alone or with H2 alone. The level of activity obtained with both 101 kPa H2 and NADH present was greater than that obtained with either 101 kPa H2 or NADH alone. Activation with H2 plus NADH was virtually independent of NADH concentration but highly dependent on H2 concentration. The effects of various concentrations of H2 and constant concentration of NADH on the level of activation were the same whether H2 oxidation was assayed by H2-dependent Methylene Blue or NAD+ reduction. Diaphorase activity did not require activation and was little affected by the treatments that activated H2-oxidizing activity. The results suggest that H2 plays an important role in regulating the level of H2-oxidizing activity in this soluble hydrogenase.

Alcaligenes↗
PubMed1988

Anatomic and functional development of the suprachiasmatic nuclei in the gray short-tailed opossum.

The anatomic and functional development of the suprachiasmatic nuclei (SCN) was studied in the gray short-tailed opossum, Monodelphis domestica. To provide a background for developmental studies, daily patterns of wheel-running behavior and SCN metabolic activity were studied in adult animals. Adult opossums manifested robust circadian rhythms in locomotor activity that were entrained by the daily light-dark cycle. The temporal course of SCN metabolic activity, studied by the 14C-labeled deoxyglucose autoradiographic technique, showed that the adult SCN were metabolically active throughout subjective day and relatively inactive during subjective night. SCN neurogenesis, determined using 3H-thymidine autoradiography, was active at postnatal day 3, the earliest age studied, and continued until postnatal day 7. It was not until postnatal day 16 that the SCN appeared as distinct nuclei by light microscopy. Study of the ontogeny of the daily rhythm in SCN metabolic activity showed that the nuclei were metabolically active during both day and night at postnatal day 16. On day 20, a clear day-night rhythm in SCN metabolic activity was first observed; the rhythm was even more pronounced on day 27. These results indicate that the gray short-tailed opossum has a functioning circadian timing system and that the anatomic and functional development of the SCN in this species occurs during the postnatal period.

Animals↗