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B L Jacobs

Publications and source records attributed to B L Jacobs.

At least 37 records · Page 2Linked to original sources
PubMed1998

Involvement of dopamine D2 receptors in apomorphine-induced facilitation of forebrain serotonin output.

The effect of systemic administration of the nonselective dopamine receptor agonist apomorphine on efflux of serotonin (5-hydroxytryptamine, 5-HT) in striatum and hippocampus of freely moving rats was examined using in vivo microdialysis. 5-HT efflux was increased by a moderate dose of apomorphine sufficient for a postsynaptic dopaminergic effect (0.5 mg/kg, s.c.), but not by a lower dose (0.1 mg/kg, s.c.), that acts preferentially on presynaptic dopamine receptors. This effect was blocked by a dopamine D2 receptor antagonist raclopride, administered either systemically or locally into striatum, but not by a 5-HT1A receptor antagonist N-¿2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl¿-N-(2-pyridinyl) cyclohexanecarboxamide 3HCI (WAY-100635). This indicates that dopamine D2 receptors, and not 5-HT1A receptors, mediate the facilitatory effect of apomorphine, and that this effect occurs at the nerve terminal level. Behavioral effects of apomorphine outlasted the concomitant changes in 5-HT efflux, suggesting that these changes resulted from dopaminergic receptor activation, rather than from the drug-induced behavioral arousal.

Animals↗
PubMed1998

Characterization of viral double-stranded RNA-binding proteins.

Several viruses have been shown to code for proteins that specifically bind to double-stranded RNA or RNA with large amounts of secondary structure. These proteins have been implicated in providing interferon resistance to viruses and in inhibiting induction of apoptosis by viruses, and have been suggested to be involved in regulation of viral and cellular protein synthesis in infected cells. This article describes methods for detecting and analyzing viral double-stranded RNA-binding proteins.

Blotting, Northern↗
PubMed1998

Role of the vaccinia virus E3L and K3L gene products in rescue of VSV and EMCV from the effects of IFN-alpha.

Vaccinia virus (VV) has been shown to be relatively resistant to the antiviral effects of interferon-alpha (IFN-alpha) and to rescue replication of IFN-sensitive viruses, such as encephalomyocarditis virus (EMCV) and vesicular stomatitis virus (VSV), from the antiviral effects of IFN. The E3L and K3L gene products have been implicated in the IFN resistance of VV. We have investigated the role that these VV-encoded functions play in the rescue of VSV and EMCV from the effects of IFN. Transient expression of the E3L open reading frame (ORF) was sufficient to rescue VSV but not EMCV from the IFN-induced antiviral state. Rescue of VSV by mutants of E3L correlated with the ability of the mutated E3L gene products to bind dsRNA. Conversely, transient expression of the K3L ORF was sufficient to partially rescue EMCV but not VSV from the effects of IFN. Results with VV deleted of either the K3L or E3L ORFs were consistent with results obtained by transient expression of these genes. These results demonstrate that the VV E3L gene products are likely responsible for the VV-mediated rescue of VSV from the effects of IFN and the K3L gene product is likely at least partly responsible for rescue of EMCV.

Antiviral Agents↗
PubMed1998

Activation of antiviral protein kinase leads to immunoglobulin E class switching in human B cells.

An epidemiologic association between viral infections and the onset of asthma and allergy has been documented. Also, evidence from animal and human studies has suggested an increase in antigen-specific immunoglobulin E (IgE) production during viral infections, and elevated levels of IgE are characteristic of human asthma and allergy. Here, we provide molecular evidence for the roles of viral infection and of activation of the antiviral protein kinase (PKR) (double-stranded-RNA [dsRNA]-activated protein kinase) in the induction of IgE class switching. The presence of dsRNA, a known component of viral infection and an activator of PKR, induced IgE class switching as detected by the expression of germ line epsilon in the human Ramos B-cell line. Furthermore, dsRNA treatment of Ramos cells resulted in the activation of PKR and in vivo activation of the NF-kappaB complex. Interestingly, infection of Ramos cells with rhinovirus (common cold virus) serotypes 14 and 16 resulted in the induction of germ line epsilon expression. To further evaluate the role of PKR in the viral induction of IgE class switching, we infected Ramos cells with two different vaccinia virus (cowpox virus) strains. Infection with wild-type vaccinia virus failed to induce germ line epsilon expression; however, a deletion mutant of vaccinia virus (VP1080) lacking the PKR-inhibitory polypeptide E3L induced the expression of germ line epsilon. Collectively, the results of our study define a common molecular mechanism underlying the role of viral infections in IgE class switching and subsequent induction of IgE-mediated disorders such as allergy and asthma.

B-Lymphocytes↗
PubMed1997

Complementation of vaccinia virus deleted of the E3L gene by mutants of E3L.

Vaccinia virus devoid of its E3L gene is sensitive to treatment of RK-13 cells with interferon-alpha and fails to replicate or form plaques in HeLa cells. In order to determine function of the E3L gene, vaccinia virus recombinants were constructed by inserting mutant E3L genes or a gene coding for an alternative dsRNA-binding protein into virus deleted of its wild type E3L gene. Those viruses that expressed proteins that retained dsRNA binding activity were resistant to the effects of interferon in RK-13 cells and could replicate in HeLa cells. Recombinant viruses that expressed E3L mutant proteins which were unable to bind to dsRNA were interferon sensitive in RK-13 cells and could not replicate in HeLa cells. In addition, a virus that expressed a mutant E3L protein previously characterized as having a low binding affinity for dsRNA exhibited an intermediate phenotype: it was interferon resistant in RK-13 cells but could not replicate in HeLa cells. This work suggests that the E3L gene of vaccinia virus functions primarily as a dsRNA-binding protein in allowing resistance to interferon and in promoting replication in HeLa cells.

Antiviral Agents↗
PubMed1997

Burst activity of ventral tegmental dopamine neurons is elicited by sensory stimuli in the awake cat.

In light of evidence implicating dopamine in the pathophysiology of attention deficit disorder and schizophrenia, diseases involving attentional or sensory processing abnormalities, it was of interest to determine whether and how dopamine neurons in the ventral tegmental area respond to sensory stimuli. The single-unit responses of ventral tegmental dopamine neurons were recorded in freely-moving cats during the presentation of brief, non-conditioned auditory and visual stimuli. Both auditory and visual stimuli produced neuronal excitation, involving a greater than 5-fold increase in the probability of burst firing followed by a period of burst inhibition. The burst nature of the single-unit response suggests that sensory-induced dopamine release at target sites was disproportionally large relative to the discharge frequency. While characteristics of the dopaminergic sensory response were similar for auditory and visual stimuli, the response latency was longer for visual stimuli. The results demonstrate that dopamine neurons in the ventral tegmental area, the site of origin for mesolimbocortical dopamine neurons, are reliably activated by non-conditioned auditory and visual stimuli.

Acoustic Stimulation↗
PubMed1997

Complementation of deletion of the vaccinia virus E3L gene by the Escherichia coli RNase III gene.

This work investigated whether the Escherichia coli RNase III gene, rnc+, could complement vp1080, a mutant vaccinia virus that is deleted of its E3L gene. Like E3L, rnc+ codes for a dsRNA binding protein that contains an additional nucleolytic activity. Rnc genes were cloned into the eukaryotic expression vector pMTVa-, expressed in COS-1 cells, and shown to be functional. Transient rescue experiments in HeLa cells demonstrated that the cleavage function of the rnc+ gene was necessary for full rescue of vp1080. The rnc 70 gene, which encodes a product deficient in catalytic activity but still capable of binding to dsRNA, rescued vp1080 weakly. The rnc 105 gene, which encodes a product that cannot bind or cleave dsRNA, was unable to rescue vp1080. The rnc genes were also inserted into the E3L locus of vp1080. While recombinants containing the rnc+ gene or the rnc 70 gene regained the IFN resistance phenotype in RK13 cells, full host range of vaccinia virus was only restored in the recombinant containing the rnc+ gene. Thus, the ability of RNase III to process dsRNA appears to be necessary to restore the host range phenotype. The vp-rnc 105 recombinant behaved similarly to vp1080.

Amino Acid Sequence↗
PubMed1997

Single-unit responses of serotonergic dorsal raphe neurons to specific motor challenges in freely moving cats.

Serotonin has been hypothesized to play an important role in the central control of motor function. Consistent with this hypothesis, virtually all serotonergic neurons within the medullary nuclei raphe obscurus and raphe pallidus in cats are activated in response to specific motor challenges. To determine whether the response profile of serotonergic neurons in the midbrain is similar to that observed in the medulla, the single-unit activity of serotonergic dorsal raphe nucleus cells was studied during three specific motor activities: treadmill-induced locomotion, hypercarbia-induced ventilatory response and spontaneous feeding. In contrast to the results obtained for medullary raphe cells, none of the serotonergic dorsal raphe cells studied (n=26) demonstrated increased firing during treadmill-induced locomotion. A subset of serotonergic dorsal raphe cells (8/36) responded to the hypercarbic ventilatory challenge with increased firing rates that were directly related to the fraction of inspired carbon dioxide, and a non-overlapping subset of cells (6/31) was activated during feeding. All feeding-on cells demonstrated a rapid activation and de-activation coincident with feeding onset and offset, respectively. Although the proportions of serotonergic cells activated by hypercarbia or feeding in the dorsal raphe nucleus were similar to those found in the medullary raphe, there were several major distinctions in the response characteristics for the two cell groups. In contrast to the medullary serotonergic neurons, only a minority of dorsal raphe nucleus serotonergic neurons responded to a motor challenge. Overall, the above results suggest very different roles for the midbrain and medullary serotonergic neurons in response to motor activities.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1997

Effects of sleep deprivation on serotonergic neuronal activity in the dorsal raphe nucleus of the freely moving cat.

Total sleep deprivation (TSD) for one or more nights produces a rapid antidepressant response in humans. Since most pharmacological treatments for depression increase brain serotonin neurotransmission, the purpose of the present study was to determine whether TSD increases the activity of serotonergic neurons in the dorsal raphe nucleus (DRN) in cats. Cats were prevented from sleeping by the experimenter, who monitored the behavioral state of each animal on a polygraph. Firing rates during quiet waking (QW) and active waking (AW) were obtained throughout a 24-h sleep deprivation period and subsequent 6-h recovery period. During the experiments, unit activity was also recorded during exposure to loud white noise, which elicited strong behavioral arousal. The inhibitory response of serotonergic DRN neurons to systemic administration of the selective 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) was determined before and after TSD to assess possible changes in 5-HT1A autoreceptor sensitivity. TSD increased mean firing rates by as much as 18% during both AW and white noise exposure. Maximal effects were observed after 15 h of TSD for AW, and after 18 h for white noise. QW firing rates also tended to be elevated throughout TSD. Firing rates for all conditions during the recovery period were not significantly different from baseline. The neuronal inhibition produced by 8-OH-DPAT was significantly diminished after TSD. Overall, these results indicate that TSD increases the firing rate of serotonergic DRN neurons during AW and arousal. This effect may be attributable to a decrease in the sensitivity of 5-HT1A autoreceptors. These findings are consistent with the hypothesis that TSD exerts its antidepressant action, at least in part, through an activation of brain serotonergic neurons.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1997

Serotonin and motor activity.

The activity of brain serotonergic neurons in both the pontine-mesencephalic and medullary groups is positively correlated with the level of behavioral arousal and/or the behavioral state. This, in turn, appears to be related to the level of tonic motor activity, especially as manifested in antigravity muscles and other muscle groups associated with gross motor activity. In addition, a subset of serotonergic neurons displays a further increase in activity in association with repetitive, central pattern generator mediated responses. Accumulating evidence indicates that this relation to motor activity is related both to the co-activation of the sympathetic nervous system and to the modulation of afferent inputs.

Animals↗
PubMed1997

Double-stranded RNA is a trigger for apoptosis in vaccinia virus-infected cells.

The vaccinia virus E3L gene codes for double-stranded RNA (dsRNA) binding proteins which can prevent activation of the dsRNA-dependent, interferon-induced protein kinase PKR. Activated PKR has been shown to induce apoptosis in HeLa cells. HeLa cells infected with vaccinia virus with the E3L gene deleted have also been shown to undergo apoptosis, whereas HeLa cells infected with wild-type vaccinia virus do not. In this report, using virus recombinants expressing mutant E3L products or alternative dsRNA binding proteins, we show that suppression of induction of apoptosis correlates with functional binding of proteins to dsRNA. Infection of HeLa cells with ts23, which leads to synthesis of increased dsRNA at restrictive temperature, induced apoptosis at restrictive but not permissive temperatures. Treatment of cells with cytosine arabinoside, which blocks the late buildup of dsRNA in vaccinia virus-infected cells, prevented induction of apoptosis by vaccinia virus with E3L deleted. Cells transfected with dsRNA in the absence of virus infection also underwent apoptosis. These results suggest that dsRNA is a trigger that can initiate a suicide response in virus-infected and perhaps uninfected cells.

Animals↗
PubMed1996

A microdialysis examination of serotonin release in the rat forebrain induced by behavioral/environmental manipulations.

Serotonin (5-HT) has been implicated in a variety of behavioral and physiological processes mediated by the central nervous system. However, the exact nature of 5-HT release under naturalistic or physiologic conditions remains unclear. The present study investigated this issue by employing in vivo microdialysis to examine 5-HT release in the hippocampus, corpus striatum, amygdala, and prefrontal cortex of the rat during manipulations that induced varying behavioral and physiological responses. In each rat, two sites were examined simultaneously during two of the following manipulations: tail pinch, tail pinch with food present, feeding, cat exposure, floating, and swimming. Results indicate that 5-HT levels increased 20-65% above baseline levels in response to each manipulation in all forebrain areas examined. The only significant difference found across manipulations was that tail pinch with food present produced a greater increase in 5-HT than cat exposure, which may be attributable to differences in the degree of general activation induced by these manipulations rather than to specific physiological or behavioral aspects. Furthermore, there was a strong positive correlation between 5-HT release and time spent in alert waking. Finally, there was an overall significantly smaller increase in 5-HT release in the corpus striatum compared to the other three sites. These data suggest that the release of 5-HT in the forebrain is closely related to behavioral state, not to specific behaviors, and that the magnitude of 5-HT release may reflect the degree of activation. In addition, this study suggests there can be some degree of differential pattern of release of 5-HT in the forebrain.

Amygdala↗
PubMed1996

5-HT1A agonists induce hippocampal theta activity in freely moving cats: role of presynaptic 5-HT1A receptors.

Electrical activity in the dorsal hippocampus was recorded in freely moving cats in response to intravenous administration of 5-HT1A agonist and antagonist drugs. Administration of low doses of the selective 5-HT1A agonists 8-OH-DPAT (5-20 micrograms/kg) and ipsapirone (20-100 micrograms/kg) produced rhythmic slow activity (theta) in the hippocampal EEG within 30 s. Similar effects were observed with BMY 7378 (20 and 100 micrograms/kg), which acts as an agonist at presynaptic (somatodendritic) 5-HT1A receptors and as an antagonist at postsynaptic 5-HT1A receptors. Power spectral analyses showed that all three compounds produced a dose-dependent increase in the EEG power occurring in the theta frequency band (3.5-8.0 Hz) as a proportion of total power from 0.25 to 30.0 Hz (relative theta power). The increase in relative theta power produced by 8-OH-DPAT (20 micrograms/kg) was greatly attenuated by spiperone (1 mg/kg), a highly effective 5-HT1A autoreceptor antagonist. Administration of spiperone alone had no significant effect on relative theta power. These results are discussed in relationship to the effects of these drugs on serotonergic neuronal activity. Our results suggest that preferential activation of presynaptic 5-HT1A receptors, and subsequent inhibition of serotonin neurotransmission, facilitates the appearance of hippocampal theta activity in awake cats.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1996

When two strands are better than one: the mediators and modulators of the cellular responses to double-stranded RNA.

Double-stranded RNA is a potent inducer of interferon, a modulator of the expression of a number of other genes involved in the response of cells to virus infection, an activator of the interferon-induced antiviral state, and may be involved in differentiation, induction of apoptosis, and control of oncogenic transformation. This review will attempt to summarize what is known about the cellular proteins that act to mediate the response of cells to double-stranded RNA and the viral and cellular macromolecules that may be able to modulate these responses.

2',5'-Oligoadenylate Synthetase↗
PubMed1996

A subgroup of dorsal raphe serotonergic neurons in the cat is strongly activated during oral-buccal movements.

A subgroup of approximately 25% of dorsal raphe nucleus serotonergic neurons in cat was strongly activated in association with oral-buccal movements, such as chewing, licking, and grooming. The mean magnitude of increase in neuronal activity for these cells was approximately 100% above the spontaneous waking level. However, some of these cells were activated by as much as 200-300%. The neuronal activation frequently preceded the initiation of the movement and stopped abruptly in association with either pauses in the motor sequence or with its cessation. Most of the neurons in this subgroup were also strongly and preferentially activated by somatosensory stimuli applied to the head, neck, and face. During orientation to a strong or novel stimulus, the activity of these neurons fell silent for periods of 1-5 s. These data and results from our previous studies of medullary raphe neurons are discussed within the context of the general role of serotonin in tonic and central pattern generator-related motor activity.

Animals↗
PubMed1996

Changes in forebrain serotonin at the light-dark transition: correlation with behaviour.

In vivo microdialysis in the rat was used to determine whether changes in forebrain serotonin (5-HT) levels seen during the light-dark transition differ by area examined and whether these changes could be accounted for by complementary changes in behaviour. 5-HT levels increased significantly during the first half hour of dark phase in the hippocampus (45.9%), striatum (13.4%), amygdala (19.7%) and prefrontal cortex (18.4%), the increase in the hippocampus being significantly larger than those in the other areas. 5-HT levels co-varied significantly with changes in the levels of alert waking, a behavioural measure of the time spent in active waking, suggesting that this factor might account for the changes in 5-HT across the light-dark transition.

Analysis of Variance↗
PubMed1996

Host-range restriction of vaccinia virus E3L-specific deletion mutants.

The vaccinia virus (VV) E3L gene product functions as a dsRNA binding protein that is involved in conferring an interferon-resistant phenotype upon the virus. Studies with a vaccinia virus (VV) E3L- deletion mutant (vP1080) have also demonstrated that the E3L gene product is critical for productive replication on certain cell substrates. While E3L was found to be nonessential for replication in chick embryo fibroblasts (CEFs), virus specifically deleted of E3L was found to be replication deficient in Vero, HeLa, and murine L929 cells. Further, the temporal block in replication appears to differ in these cell systems, as evidenced by the observed timing of protein synthesis inhibition. In Vero cells infected with the VV E3L- mutant, there was no detectable protein synthesis after 2 hr post-infection, whereas in L929 cells normal protein patterns were observed even at late times post-infection. Expression of a heterologous dsRNA binding protein, the reovirus sigma 3 protein, by the E3L- mutant virus restored near wild-type growth characteristics, suggesting the critical nature for regulating dsRNA levels in VV-infected cells.

Animals↗