Regional and developmental expression of calmodulin-dependent cyclic nucleotide phosphodiesterase in rat brain.
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2',3'-Cyclic-Nucleotide Phosphodiesterases↗
Biomedical subjects
C D Balaban
Publications and source records attributed to C D Balaban.
Directional tuning of the human presaccadic spike potential.
This study examined the behavior of the presaccadic spike potential (SP) in 20 normal, right-handed subjects for self-paced 10 degree saccades along vertical, horizontal and oblique meridians. The SP was recorded differentially between posterior parietal sites and a linked ear reference. The SP amplitude showed clear directional tuning properties with the maximum response prior to saccades directed in an oblique, downward and contralateral direction. The minimum response was obtained for upward saccades. The data were fitted to a model consisting of 3 components: (1) a constant component reflecting saccadic amplitude; (2) a component with narrow directional tuning that is modeled from properties of frontal eye field neurons in monkeys; and (3) a component with broad directional tuning that is designed to reflect directional tuning properties of potentials originating from horizontal and vertical saccade generators, motoneurons and extraocular muscles. The narrowly tuned mechanism is sufficient to encode the direction of saccades. One surprising finding, though, was that the broadly tuned mechanism was necessary and sufficient to account for differences in SP amplitude as a function of electrode laterality. Application of this model approach to published data for periorbital SP, recorded between periorbital and parietal sites (G. W. Thickbroom and F. L. Mastaglia, Electroencephalogr. Clin. Neurophysiol., 64 (1986) 211-214), suggested that this potential represents a broadly tuned mechanism with directional tuning opposite the parietal SP. These data indicate that the periorbital and parietal SPs represent activation of different networks of central generators.
Adult↗
Toxic effects of somatostatin in the cerebellum and vestibular nuclei: multiple sites of action.
This study demonstrates that somatostatin (SRIF), an endogenous peptide in vestibular nuclei and cerebellum, can produce both a dose-dependent death of Purkinje cells in distinct sagittal regions of cerebellar cortex and vascular infarcts centered selectively in the inferior vestibular nucleus. Alert, adult male rats were given a 5 microliters intracerebroventricular (i.c.v.) bolus of either SRIF alone (20 or 40 micrograms) or a combined dose of SRIF plus either arginine-vasopressin (AVP, 1 micrograms) or an AVP V1 antagonist, (1-(beta-mercapto-beta,beta-cyclopentamethylene propionic acid), 2-(O-methyl)-tyrosine)-arginine 8-vasopressin (mcAVP, 1 micrograms), through an implanted cannula. After a 4-5 day survival, the brains were stained with the cupric-silver selective degeneration method. Two types of dose-dependent lesions were observed in the cerebellar and vestibular nuclei of these animals: degeneration of Purkinje cell responses in the cerebellar cortex and vascular infarcts in vestibular nuclei. These toxic responses were unaffected by application of AVP or mcAVP; hence, they can be attributed to actions of SRIF. The distribution of Purkinje cell degeneration varied with the SRIF dose in different cerebellar regions. Purkinje cell responses in lobules I-III were equivalent at both SRIF doses, and degeneration in the copula pyramis, paraflocculus and paramedian lobule emerged at the higher SRIF dose. Purkinje cells in the medial aspect of lobules IX-X had an intermediate sensitivity to SRIF intoxication. Degenerating Purkinje cells tended to be arranged in parasagittal bands in each region, suggesting parasagittal zonal variations in susceptibility to SRIF intoxication. By contrast, infarctions in the vestibular nuclei only appeared at the higher SRIF dose. These infarcts could be unilateral or bilateral and always involved the inferior vestibular nucleus at the level of the caudal margin of the acoustic tubercle; they often extended into the medial and lateral vestibular nuclei. The infarcts had a necrotic core that was infiltrated by non-neuronal elements. Thus, they appear to reflect a direct or neurally-mediated vascular response to the peptide.
Animals↗
Developmental expression of calmodulin-dependent cyclic nucleotide phosphodiesterase in rat brain.
The patterns of expression of calmodulin-dependent cyclic nucleotide phosphodiesterase (CaM-PDE) have been studied in developing and adult rat brain using affinity-purified polyclonal antibodies against CaM-PDE. An immunocytochemical map of adult brain regions expressing CaM-PDE, constructed from serial coronal brain sections, illustrated that CaM-PDE was expressed in specific neuronal subpopulations throughout the adult rat brain. Immunoblot analysis coupled with subcellular fractionation indicated that CaM-PDE was primarily localized to cytoplasmic fractions, with a small amount associated with synaptosomal membranes. Immunoblots from developing brain indicated that CaM-PDE expression increased dramatically during postnatal days 7-20 (PND 7-20); parallel increases in CaM-PDE enzyme activity occurred during this same time. Immunocytochemical studies indicated that several distinct patterns of CaM-PDE expression occurred during development. Neocortex showed low levels of CaM-PDE immunoreactivity in neuronal somata of layers III, V and VI on PND 4 that increased by PND 11; the adult somatodendritic pattern of immunoreactivity was observed by PND 60. Similar patterns were observed in cerebellar Purkinje cells, with somatodendritic staining observed by PND 12. By contrast, caudate-putamen, the inferior olive and the hypoglossal nuclei expressed high levels of CaM-PDE on PND 4, with levels considerably lower in the adult animal. The different patterns of expression suggest that in neocortex and cerebellum, CaM-PDE increases during the period of neuronal differentiation and active synaptogenesis, while in the caudate-putamen, inferior olive and hypoglossal nucleus, high levels may be required early in development.
Aging↗
Use of avidin-biotin subtractive hybridization to characterize mRNA common to neurons destroyed by the selective neurotoxicant trimethyltin.
Trimethyltin (TMT), a selective neurotoxicant, destroys a distinct subpopulation of neurons which possess no known biochemical or anatomic linkage. However, TMT-sensitive neurons may share common gene products related to susceptibility. In an effort to isolate mRNAs common to TMT-sensitive neurons, avidin/biotin based-subtractive hybridization was used to generate a cDNA library specifically related to TMT-toxicity. Out of 50 cDNAs, two clones hybridized only to poly(A+) mRNA isolated from the brains of saline-treated rats. Two of these cDNAs, p9T10 and p9T19, were used for in situ hybridization; both hybridized to hippocampus, limbic cortex, amygdala and other regions destroyed by TMT, suggesting that these probes identified mRNA enriched in TMT-sensitive neurons. The patterns of in situ hybridization coupled with the loss of p9T10 and p9T19 hybridization to mRNA isolated from the brains of TMT-treated rats suggests that one or both of these two clones may represent mRNA found in neurons damaged by TMT. The combination of selective neurotoxic lesions followed by cDNA subtractive hybridization should prove to be a useful strategy for the isolation of gene products from specific neuronal populations.
Animals↗
Nodulus-uvula depressor response: central GABA-mediated inhibition of alpha-adrenergic outflow.
Electrical stimulation of a lateral region of the cerebellar nodulus-uvula transition zone in anesthetized albino rabbits decreases mean arterial blood pressure in direct proportion to stimulus intensity. The hypotension has an abrupt onset and is phasic; heart rate is unaffected. Neural pathways that might mediate the depressor response were studied using autonomic-blocking agents. Pretreatment with 2 mg/kg iv of either propranolol HCl or atropine methyl nitrate did not alter the onset or duration of the hypotensive response. However, pretreatment with 2 mg/kg iv phentolamine HCl abolished the depressor response, and 7 mg.kg-1.min-1 iv tetraethylammonium infusion decreased the response by more than 50%. Ipsilateral injections of 200 ng bicuculline methiodide into an area immediately dorsal to the superior cerebellar peduncle or the dorsal aspect of the superior vestibular nucleus reversibly attenuated the nodulus-uvula evoked depression. Anterograde horseradish peroxidase-wheat germ agglutinin (HRP-WGA) transport experiments revealed that both these regions receive direct inputs from the nodulus-uvula. These data suggest that hypotensive events elicited by lateral nodulus-uvula stimuli represent a central, alpha-aminobutyric acid-mediated, phasic inhibition of vasomotor drive mediated through autonomic ganglia to alpha-adrenoreceptors in the vasculature.
Animals↗
Neuropeptide modulation of central vestibular circuits.
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Animals↗
Evidence for transsynaptic regulation of calmodulin-dependent cyclic nucleotide phosphodiesterase in cerebellar Purkinje cells.
Calmodulin-dependent phosphodiesterase (CaM-PDE) is selectively expressed in specific neuronal populations in adult rat brain. In cerebellar cortex, it is expressed at high levels in Purkinje cells (soma and dendrites). Climbing fiber ablation by intraperitoneal injections of 3-acetylpyridine resulted in a selective depression of cerebellar CaM-PDE expression using Western immunoblot procedures; neither calcineurin (calmodulin-dependent protein phosphatase) nor other calmodulin binding proteins, detected by biotinylated calmodulin overlays, were affected. Immunocytochemical staining of cerebellum revealed a loss of detectable CaM-PDE immunoreactivity in Purkinje cells, with no appreciable change in calcineurin immunoreactivity. Cerebral cortex was examined as a control for a direct effect of 3-acetylpyridine on CaM-PDE expression, independent of climbing fiber deafferentation. There were no detectable changes in CaM-PDE or calcineurin immunoreactivity in cortical pyramidal cells, and no changes were detected, either in Western blot analyses for CaM-PDE or calcineurin or in biotinylated calmodulin overlays. These data suggest that CaM-PDE expression in Purkinje cells is regulated transsynaptically by climbing fiber inputs.
Animals↗
Diazepam attenuation of somatostatin-induced motor disturbances and neurotoxicity.
Intracerebroventricular somatostatin administration to conscious rats results in a characteristic motor abnormality (barrel rotation), convulsions that are frequently fatal and destruction of cerebellar Purkinje cells. This study demonstrates that each of these manifestations of this neuropeptide can be attenuated by pretreatment with diazepam (Valium, 5 mg/kg, i.p.) but not in vehicle-pretreated controls. Specifically, the incidence of mortality was reduced from 5/12 controls to 2/20 diazepam-treated rats, the incidence of barrel rotation was reduced from 6/12 controls to 2/20 diazepam-treated rats and the incidence of Purkinje cell death was reduced from 4/4 examined controls to 4/13 diazepam-treated animals. Vehicle pretreated rats did not differ from untreated rats. Thus, in addition to blocking somatostatin-induced motor dysfunction and mortality, diazepam offers significant protection from central neuronal cell death in the cerebellar cortex.
Animals↗
Motor disturbances and neurotoxicity induced by centrally administered somatostatin and vasopressin in conscious rats: interactive effects of two neuropeptides.
Barrel rotation (BR) is an abnormal, long-axis rotation induced by intracerebroventricular (i.c.v.) injections of peptides, including somatostatin (SRIF) and arginine-vasopressin (AVP). This study examined the effects of two i.c.v. doses of SRIF and combined injections of SRIF and AVP in conscious, adult Wistar and Sprague-Dawley rats. Mortality after i.c.v. SRIF was dose-dependent; 0/16 rats died after a 20 microgram dose, while 21/43 died after 40 micrograms SRIF. On the other hand, BR incidence was similar after the two doses, but the hazard function of the BR latency data was shifted to the left by the higher dose. Although the incidence data imply that BR and mortality are independent, the hazard function of BR latency data is predictive of mortality. An interaction study employing a combined i.c.v. dose of 20 micrograms SRIF and 0.5 micrograms AVP established that the effects add non-linearly. This is illustrated by a marked increment in mortality (0/16 for 20 micrograms SRIF, 1/25 for 0.5 micrograms AVP and 12/18 for SRIF + AVP). The hazard plot shows a similar, non-linear interaction. In addition, SRIF, but not AVP, produced a characteristic pattern of Purkinje cell death in cerebellar regions projecting to the fastigial and lateral vestibular nuclei. These results imply that SRIF and AVP act at independent sites to produce BR and mortality, and that the effects summate non-linearly at a common central site. This raises the issue of whether these neuropeptides, endogenous in human CSF, interact to produce similar biological effects.
Animals↗
Zonal organization of olivo-nodulus projections in albino rabbits.
The organization of inferior olivary projections to the cerebellar nodulus in albino rabbits was assessed by autoradiographic, anterograde degeneration and retrograde transport techniques. These data indicate that the caudal aspect of the dorsal cap of Kooy projects to a band extending 0.5-1 mm lateral to the midline of the nodulus. The medial half of this region receives a projection from beta nucleus over at least the dorsal surface of the nodulus; an extension onto the ventral surface, though, is consistent with the anterograde tracing data. The rostral aspect of the dorsal cap and ventrolateral outgrowth projects to an adjacent 0.5-1 mm wide band in the nodulus. A group of cells spanning the intermediocaudal dorsal cap and the adjacent, dorsomedial margin of the beta nucleus appears to project laterally on the ventral surface of the nodulus. On the dorsal aspect of the nodulus and ventral surface of lobule IXd, though, comparisons of anterograde and retrograde tracing data suggest that this lateral field is innervated by the rostral aspect of the dorsomedial cell column and the rostromedial accessory olive. Finally, the regions of lobules X and IXd lining the posterolateral fissure represent a transition between lobule IX and ventral lobule X patterns of olivary projections. These data provide a basis for investigating the efferent projections of the nodulus to distinct olivo-vestibular terminal fields in the vestibular nuclei.
Animals↗
Trimethyltin-induced neuronal damage in the rat brain: comparative studies using silver degeneration stains, immunocytochemistry and immunoassay for neuronotypic and gliotypic proteins.
Trimethyltin is a neurotoxicant which produces a distinct pattern of neuronal cell death following peripheral administration of a single dose (8 mg/kg, i.p.) in rats. The cupric-silver degeneration stain was used to produce an atlas documenting the distribution and time course of trimethyltin-induced neuronal damage in adult, male Long-Evans rats. Animals were examined at survival times of 1, 2, 3, 4, 5, 7, 10 and 18 days after intoxication. The earliest degeneration was observed at day 1 in the intermediate and ventral divisions of the lateral septal nucleus, followed by development of degeneration on days 2-4 in neuron populations including the septohippocampal nucleus, septohypothalamic nucleus, anterior olfactory nucleus, bed nucleus of the stria terminalis, endopiriform nucleus, parafascicular nucleus, superior colliculus, interstitial nucleus of the posterior commissure, inferior colliculus, pontine nuclei, raphe nuclei, pars caudalis of the spinal trigeminal nucleus, the caudal aspect of nucleus tractus solitarius, dorsal vagal motor nucleus, granule cells in the dentate gyrus, pyramidal cells in CA fields of the hippocampus, and of neurons in the subiculum, pyriform cortex, entorhinal cortex and neocortex (mainly layer Vb and VI). This was followed by degenerative changes on days 5-7 in other structures, including the amygdaloid nuclei, the ventral posterolateral and ventral posteromedial thalamic nuclei and the periaqueductal gray. The distribution of terminal degeneration from these neurons indicate that specific pools of cells are affected in each structure, and the time course suggests somatofugal degeneration. The trimethyltin damage was also assessed with immunocytochemical visualization of a neuronotypic protein, protein-O-carboxyl methyltransferase and a radioimmunoassay for glial fibrillary acidic protein. Protein-O-carboxyl methyltransferase immunoreactivity was altered in neuronal populations damaged by trimethyltin, but did not appear to be either as sensitive or selective an assay of neuronal damage as the silver stain, especially at short survival times. Glial fibrillary acidic proteins were dramatically elevated 21 days after trimethyltin intoxication, particularly in areas of extensive damage. These studies revealed advantages and problems encountered in the use of each technique in assessing neurotoxic effects, forming a basis for discussion of the relative merits of using a battery of specific molecular probes for neurotoxicity evaluations.
Animals↗
Distribution of inferior olivary projections to the vestibular nuclei of albino rabbits.
This study analyses the course and topography of olivo-vestibular projections originating in the dorsal cap, ventrolateral outgrowth and beta nucleus of albino rabbits. Rabbits were given either single pressure-injections of [3H]L-leucine (20 microCi in 50 nl) or single or multiple injections of 3-acetylpyridine (0.2-0.25 microliter of 27.5 micrograms/microliter in saline) into the medial aspect of the inferior olive. Brains from the former animals were processed for autoradiography after 2-3 days survival; brains from the latter animals were stained for degeneration with cupric-silver methods after a 16-24 h survival. In addition, four rabbits with kainic acid lesions of the flocculus were used to document flocculo-vestibular projections. Olivo-vestibular projections from the dorsal cap ventrolateral outgrowth, beta nucleus and the medial accessory olive diverge from olivo-cerebellar projections at the caudal margin of the flocculus stalk, and course medially in a broad sheet. Fibers (1) ascend in the superior fascicle, with flocculo-vestibular projections, to the superior vestibular nucleus, (2) enter the medial fascicle, with flocculo-vestibular fibers, and course along the dorsolateral border of the 4th ventricle to innervate a distinct rostral subdivision of the medial vestibular nucleus, and (3) enter the lateral fascicle, with flocculo-vestibular fibers, to terminate in pars alpha and beta of the lateral vestibular nucleus and the caudal subdivision of the medial vestibular nucleus. Comparison of different injection cases indicate that the caudal half to two-thirds of the dorsal cap contributes projections to the rostral medial vestibular nucleus, centrolateral and dorsomedial aspects of the superior vestibular nucleus, and a projection to both central and dorsal aspects of the caudal medial vestibular nucleus. By contrast, the rostral third to half of the dorsal cap-ventrolateral outgrowth projects sparsely to the rostral medial vestibular nucleus, contributing dense projections to the central aspect of the superior vestibular nucleus and dorsomedial and lateral regions in the caudal medial vestibular nucleus.(ABSTRACT TRUNCATED AT 400 WORDS)
Animals↗
Production of monoclonal antibodies against RNA polymerase I from nonimmunized autoimmune MRL/lpr mice and their use in rDNA transcription analysis.
A hybridoma secreting monoclonal antibodies against RNA polymerase I was produced by the fusion of myeloma cells with spleen cells from a nonimmunized MRL/lpr mouse which is known to produce autoantibodies to RNA polymerase I. The antibodies (McAb-2D11) belong to the IgG2b subclass, reacted specifically with the second largest (120 kDa) subunit of RNA polymerase I, and inhibited accurate transcription of cloned rat rDNA in a fractionated cell extract following immunoprecipitation of RNA polymerase I. McAb-2D11 did not inhibit RNA polymerase II-mediated transcription of the mouse metallothionein-I gene. Immunocytochemical procedures with biotinylated second antibody demonstrated specific immunolocalization of RNA polymerase I in the nucleus. These studies have (a) presented direct evidence that autoantibodies to functional RNA polymerase I are produced in a murine model of systemic lupus erythematosus, (b) demonstrated specificity of the monoclonal antibody for RNA polymerase I, and (c) provided a useful tool for the purification of RNA polymerase I and/or transcription factor(s) associated with RNA polymerase I.
Animals↗
Site-dependent central effects of aldosterone in rats.
A relationship between the subcommissural organ (SCO) and the adrenal glands has long been suspected. This report provides further information about the effects of a continuous D-aldosterone infusion into the SCO area of conscious, adult male Sprague-Dawley rats. A 6-day aldosterone infusion (5 ng/h) increased urinary sodium excretion, decreased adrenal medullary cross-sectional area, elevated adrenal corticosterone content and terminal plasma epinephrine concentration. Mineralocorticoid infusions directly into a lateral cerebral ventricle did not affect these parameters but, unlike SCO area infusions, decreased consummatory behavior. Infusions of tritiated aldosterone into the SCO area revealed that radioactivity was mainly confined to dorsomedial portions of the brain near the SCO, whereas the pineal body contained only background radioactivity. The data support the concept that the SCO area interacts with physiological systems related to both the adrenal cortex and medulla.
Adrenal Glands↗
Differential localization of calmodulin-dependent enzymes in rat brain: evidence for selective expression of cyclic nucleotide phosphodiesterase in specific neurons.
High-affinity antibodies against calmodulin (CaM)-dependent cyclic nucleotide phosphodiesterase and protein phosphatase (calcineurin) were purified and characterized. Rabbit anti-phosphodiesterase antibody did not react with other phosphodiesterases or with the regulatory subunits of cAMP-dependent protein kinase. Affinity-purified goat anti-calcineurin antibody recognized both the 61-kDa catalytic subunit and the 18-kDa Ca2+-binding subunit of the phosphatase. Neither antibody reacted with CaM, several CaM-binding proteins (calmodulin-dependent protein kinase, myosin light chain kinase, fodrin), or other cytosolic proteins from brain. The antibodies were used to compare the cellular localization of these two CaM-dependent enzymes in rat brain. Both calcineurin and phosphodiesterase were found predominantly in nerve cells; however, phosphodiesterase was restricted to very specific neuronal populations. Phosphodiesterase was prominent in the somatic cytoplasm and dendrites of regional output neurons--e.g., cerebellar Purkinje cells and hippocampal and cortical pyramidal cells. The extensive and uniform staining in the dendrites was consistent with postsynaptic localization and suggested an important function for this enzyme in neurons that integrate multiple convergent inputs. Calcineurin was present in virtually all classes of neurons, with immunoreactivity confined primarily to cell bodies. Both diffuse cytoplasmic staining and characteristic punctate staining of cell bodies were observed; the latter suggested compartmentalization of calcineurin at or near the plasma membrane. The results of this study demonstrate that calcineurin and phosphodiesterase are differentially localized in the central nervous system. Thus, the expression and compartmentalization of CaM-binding proteins may be highly regulated and specific for particular differentiated nerve cell types.
2',3'-Cyclic-Nucleotide Phosphodiesterases↗
Human spike potentials prior to saccades and optokinetic nystagmus fast phases: effects of instructions, eye movement direction and electrode laterality.
Presaccadic potentials in humans consist of 3 components, a slow negative shift, a positive antecedent potential and a spike potential (SP). This study demonstrated the presence of the SP before another class of rapid eye movements, fast phases of optokinetic nystagmus (OKN), in 11 right-handed, normal human subjects and compared the amplitude of the averaged SP for OKN fast phases, recorded at P3 and P4 (International 10/20 System), with the SP amplitude for 10 degrees self-paced saccades between two red light-emitting diodes. In particular, the effects of electrode laterality, rapid eye movement direction and two sets of instructions during the OKN task were assessed. Subjects were told to either 'look at the screen' (OKN1 paradigm) or to 'try to slow or stop the motion of the pattern' (OKN2 paradigm) during presentation of optokinetic stimulation. As in the case of saccades, the OKN fast phase velocity spike was used to trigger the signal averager (Nicolet (CA-1000]. There were two significant differences in SP amplitude prior to saccades and OKN fast phases. First, 3-way analysis of variance (ANOVA) and Newman-Keuls comparisons revealed that the SP was attenuated significantly for OKN for either eye movement direction over either left or right recording sites (F = 16.045, P less than 0.001). This effect was not related to amplitude differences in eye movements in the different tasks, although a contribution of variance in the OKN fast phase amplitudes cannot be excluded.(ABSTRACT TRUNCATED AT 250 WORDS)
Cerebral Cortex↗
Barrel rotation evoked by intracerebroventricular vasopressin injections in conscious rats. I. Description and general pharmacology.
Intracerebroventricular (i.c.v.) arginine-vasopressin (AVP) injections in rats evoke an unusual motor response termed 'barrel rotation' (BR). This report documents several aspects of BR after i.c.v. AVP in conscious, adult male Sprague-Dawley rats: single i.c.v. AVP injections (100-1000 ng/5 microliters) evoke BR in about 50% of naive rats with no relationship to dose and 20% mortality; no directional preference exists for BR, and sensitivity to BR does not vary over a weight range of 301-475 g; continuous i.c.v. AVP infusions at doses of 50-2500 ng/h evoked BR in 13 and 50% of rats tested at the extreme ranges; latency to BR was always within 3-6 min in infusion experiments; a protocol where rats received a single i.c.v. AVP injection (1 microgram) on day 1 followed on day 3 by 0.5 micrograms, increased the proportion of rats with BR from 51% to 83% (P less than 0.05), indicating a sensitization phenomenon; latency to BR after single i.c.v. injections did not fit the assumption of single underlying normal distribution; a novel method to analyze these data, hazard plotting, revealed two phases to the BR latency under ambient illumination. The following paper presents evidence of visual/vestibular involvement and the efficacy of anti-seizure drugs. Collectively, the data are compatible with the hypothesis that brain vasopressin pathways are involved in some abnormalities of motor output.
Animals↗