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S Steidl

Publications and source records attributed to S Steidl.

At least 19 recordsLinked to original sources
PubMed2006

Midbrain pathways for prepulse inhibition and startle activation in rat.

The midbrain is essential for prepulse inhibition (PPI) of the startle reflex, but the exact neural circuits for PPI are not yet determined. Electrical stimulation of the superior colliculus (SC) or pedunculopontine tegmentum was used to characterize the neurons and pathways that mediate PPI and the activation of startle that also occurs at higher currents in the same sites. Startle was inhibited by prepulses in most, but not all SC sites, with the lowest intensity sites in intermediate layers of SC. PPI latencies in SC sites were 4-6 ms longer than in inferior colliculus, intercollicular nucleus or pedunculopontine sites. Contrary to previous serial models, there must be two parallel midbrain pathways for PPI, a faster auditory pathway from inferior colliculus to pedunculopontine tegmentum, and a slower multimodal SC output for PPI. Double-pulse stimulation of SC sites shows that PPI results from direct stimulation of neurons with moderate refractory periods (0.4-1.0 ms), similar to SC neurons that mediate contraversive turning responses. By contrast, startle activation occurring at higher currents in all SC sites (even sites where PPI could not be elicited) results from stimulation of very short refractory period neurons (0.3-0.5 ms) and very long refractory period neurons (1.0-2.0 ms), with startle inhibition often found from 0.5-1.0 ms. Startle activation appears to result from stimulation of short refractory period neurons in deep SC layers that mediate fear-potentiated startle, plus long refractory period substrates in more dorsal SC sites.

Animals↗
PubMed2004

Kynurenate in the pontine reticular formation inhibits acoustic and trigeminal nucleus-evoked startle, but not vestibular nucleus-evoked startle.

The startle reflex is elicited by acoustic, trigeminal or vestibular stimulation, or by combinations of these stimuli. Acoustic startle is mediated largely by ibotenate-sensitive neurons in the ventrocaudal pontine reticular formation (PnC). In these studies we tested whether startle elicited by stimulation of different modalities is affected by infusion of the non-selective glutamate antagonist, kynurenate, into the PnC. In awake rats, startle responses evoked by either acoustic or spinal trigeminal nucleus stimulation were inhibited by kynurenate, but not saline, infusions, with the most effective placements nearest PnC. In chloral hydrate-anesthetized rats, kynurenate in the PnC reduced trigeminal nucleus-evoked hindlimb EMG responses, but not vestibular nucleus-evoked startle. Kynurenate in the vestibular nucleus had no effect on trigeminal nucleus-evoked startle. These results indicate that trigeminal nucleus stimulation evokes startle largely through glutamate receptors in the PnC, similarly to acoustic startle, but vestibular nucleus-evoked startle is mediated through other pathways, such as the vestibulospinal tract.

Animals↗
PubMed2001

A novel lentivirus vector derived from apathogenic simian immunodeficiency virus.

The improvement of gene transfer efficiency in growth-arrested cells using human immunodeficiency virus type 1 (HIV-1)-derived vectors led to the development of vectors derived from other members of the lentivirus family. Here we report the generation of a lentiviral vector derived from the apathogenic molecular virus clone SIVagm3mc of the simian immunodeficiency virus from African green monkeys (Cercocebus pygerythrus). Upon pseudotyping with the G-protein of vesicular stomatitis virus (VSV-G), the SIVagm-derived vector was shown to transduce proliferating and growth-arrested mammalian cell lines, including human cells. After in vivo inoculation into the striatum of the adult rat brain, the vector was shown to transduce terminally differentiated neurons and oligodendrocytes as well as quiescent and reactive astrocytes. Moreover, SIVagm transfer vector mRNA was efficiently packaged by HIV-1 vector particles. Homologous [SIV(SIV)] vectors generated by using the SIVagm-derived envelope glycoproteins allowed selective gene transfer into human CD4(+)/CCR5(+) cells. Thus, the SIVagm3mc-derived vector is a useful alternative to HIV-1-derived lentiviral vectors in somatic gene therapy.

Animals↗
PubMed2001

Subcellular localization of the homocitrate synthase in Penicillium chrysogenum.

There are conflicting reports regarding the cellular localization in Saccharomyces cerevisiae and filamentous fungi of homocitrate synthase, the first enzyme in the lysine biosynthetic pathway. The homocitrate synthase (HS) gene (lys1) of Penicillium chrysogenum was disrupted in three transformants (HS(-)) of the Wis 54-1255 pyrG strain. The three mutants named HS1(-), HS2(-) and HS3(-) all lacked homocitrate synthase activity and showed lysine auxotrophy, indicating that there is a single gene for homocitrate synthase in P. chrysogenum. The lys1 ORF was fused in frame to the gene for the green fluorescent protein (GFP) gene of the jellyfish Aequorea victoria. Homocitrate synthase-deficient mutants transformed with a plasmid containing the lys1-GFP fusion recovered prototrophy and showed similar levels of homocitrate synthase activity to the parental strain Wis 54-1255, indicating that the hybrid protein retains the biological function of wild-type homocitrate synthase. Immunoblotting analysis revealed that the HS-GFP fusion protein is maintained intact and does not release the GFP moiety. Fluorescence microscopy analysis of the transformants showed that homocitrate synthase was mainly located in the cytoplasm in P. chrysogenum; in S. cerevisiae the enzyme is targeted to the nucleus. The control nuclear protein StuA was properly targeted to the nucleus when the StuA (targeting domain)-GFP hybrid protein was expressed in P. chrysogenum. The difference in localization of homocitrate synthase between P. chrysogenum and S. cerevisiae suggests that this protein may play a regulatory function, in addition to its catalytic function, in S. cerevisiae but not in P. chrysogenum.

Amino Acid Sequence↗
PubMed2001

The Aspergillus nidulans multimeric CCAAT binding complex AnCF is negatively autoregulated via its hapB subunit gene.

Cis-acting CCAAT elements are frequently found in eukaryotic promoter regions. Many of them are bound by conserved multimeric complexes. In the fungus Aspergillus nidulans the respective complex was designated AnCF (A. nidulans CCAAT binding factor). AnCF is composed of at least three subunits designated HapB, HapC and HapE. Here, we show that the promoter regions of the hapB genes in both A. nidulans and Aspergillus oryzae contain two inversely oriented, conserved CCAAT boxes (box alpha and box beta). Electrophoretic mobility shift assays (EMSAs) using both nuclear extracts and the purified, reconstituted AnCF complex indicated that AnCF binding in vitro to these boxes occurs in a non-mutually exclusive manner. Western and Northern blot analyses showed that steady-state levels of HapB protein as well as hapB mRNA were elevated in hapC and hapE deletion mutants, suggesting a repressing effect of AnCF on hapB expression. Consistently, in a hapB deletion background the hapB-lacZ expression level was elevated compared with the expression in the wild-type. This was further supported by overexpression of hapB using an inducible alcA-hapB construct. Induction of alcA-hapB expression strongly repressed the expression of a hapB-lacZ gene fusion. However, mutagenesis of box beta led to a fivefold reduced expression of a hapB-lacZ gene fusion compared with the expression derived from a wild-type hapB-lacZ fusion. These results indicate that (i) box beta is an important positive cis-acting element in hapB regulation, (ii) AnCF does not represent the corresponding positive trans-acting factor and (iii) that AnCF is involved in repression of hapB.

Aspergillus nidulans↗
PubMed2001

The Aspergillus nidulans homoaconitase gene lysF is negatively regulated by the multimeric CCAAT-binding complex AnCF and positively regulated by GATA sites.

In beta-lactam-antibiotic-producing fungi, such as Aspergillus (Emericella) nidulans, L-alpha-aminoadipic acid is the branching point of the lysine and penicillin biosynthesis pathways. To obtain a deeper insight into the regulation of lysine biosynthesis genes, the regulation of the A. nidulans lysF gene, which encodes homoaconitase, was studied. Band-shift assays indicated that the A. nidulans multimeric CCAAT-binding complex AnCF binds to two of four CCAAT motifs present in the lysF promoter region. AnCF consists at least of three different subunits, designated HapB, HapC, and HapE. In both a delta hapB and a delta hapC strain, the expression of a translational lysF-lacZ gene fusion integrated in single copy at the chromosomal argB gene locus was two to three-fold higher than in a wild-type strain. These data show that AnCF negatively regulates lysF expression. The results of Northern blot analysis and lysF-lacZ expression analysis did not indicate a lysine-dependent repression of lysF expression. Furthermore, mutational analysis of the lysF promoter region revealed that two GATA sites matching the GATA consensus sequence HGATAR positively affected lysF-lacZ expression. Results of Northern blot analysis also excluded that the global nitrogen regulator AreA is the responsible trans-acting GATA-binding factor.

Aspergillus nidulans↗
PubMed2001

AoHapB, AoHapC and AoHapE, subunits of the Aspergillus oryzae CCAAT-binding complex, are functionally interchangeable with the corresponding subunits in Aspergillus nidulans.

Two genes, AohapB and AohapE, encoding subunits of the Aspergillus oryzae CCAAT-binding complex were cloned and sequenced. The polypeptides encoded by AohapB and AohapE were expressed in Escherichia coli and used to reconstitute a DNA-binding complex with recombinant AoHapC. The DNA-binding activity was observed only in the presence of all three subunits, indicating that AoHapB, AoHapE and AoHapC are essential for CCAAT-binding. Furthermore, introduction of the AohapB, AohapC and AohapE genes into the A. nidulans hapB delta, hapC delta and hapE delta strains, respectively, revealed that the A. oryzae Hap subunits are functionally interchangeable with the corresponding subunits in A. nidulans.

Amino Acid Sequence↗
PubMed2001

Contributions of the vestibular nucleus and vestibulospinal tract to the startle reflex.

The startle reflex is elicited by strong and sudden acoustic, vestibular or trigeminal stimuli. The caudal pontine reticular nucleus, which mediates acoustic startle via the reticulospinal tract, receives further anatomical connections from vestibular and trigeminal nuclei, and can be activated by vestibular and tactile stimuli, suggesting that this pontine reticular structure could mediate vestibular and trigeminal startle. The vestibular nucleus, however, also projects to the spinal cord directly via the vestibulospinal tracts, and therefore may mediate vestibular startle via additional faster routes without a synaptic relay in the hindbrain. In the present study, the timing properties of the vestibular efferent pathways mediating startle-like responses were examined in rats using electrical stimulation techniques. Transient single- or twin-pulse electrical stimulation of the vestibular nucleus evoked bilateral, startle-like responses with short refractory periods. In chloral hydrate-anesthetized rats, hindlimb electromyogram latencies recorded from the anterior biceps femoris muscle were shorter than those for stimulation of the trigeminal nucleus, and similar to those for stimulation of the caudal pontine reticular nucleus or ventromedial medulla. In awake rats, combining vestibular nucleus stimulation with either acoustic stimulation or trigeminal nucleus stimulation enhanced the whole-body startle-like responses and led to strong cross-modal summation without collision effects. In both chloral hydrate-anesthetized and awake rats, combining vestibular nucleus stimulation with ventromedial medulla stimulation produced a symmetrical collision effect, i.e. a loss of summation at the same positive and negative stimulus intervals, indicating a continuous connection between the vestibular nucleus and ventromedial medulla in mediating vestibular startle. By contrast, combining trigeminal nucleus stimulation with ventromedial medulla stimulation resulted in an asymmetric collision effect when the trigeminal nucleus stimulation preceded ventromedial medulla stimulation by 0.5 ms, suggesting that a monosynaptic connection between the trigeminal nucleus and ventromedial medulla mediates trigeminal startle. We propose that the vestibulospinal tracts participate strongly in mediating startle produced by activation of the vestibular nucleus. The convergence of the vestibulospinal tracts with the reticulospinal tract within the spinal cord therefore provides the neural basis of cross-modal summation of startling stimuli.

Acoustic Stimulation↗
PubMed2001

Targeted gene transfer to lymphocytes using murine leukaemia virus vectors pseudotyped with spleen necrosis virus envelope proteins.

In contrast to murine leukaemia virus (MLV)-derived vector systems, vector particles derived from the avian spleen necrosis virus (SNV) have been successfully targeted to subsets of human cells by envelope modification with antibody fragments (scFv). However, an in vivo application of the SNV vector system in gene transfer protocols is hampered by its lack of resistance against human complement. To overcome this limitation we established pseudotyping of MLV vector particles produced in human packaging cell lines with the SNV envelope (Env) protein. Three variants of SNV Env proteins differing in the length of their cytoplasmic domains were all efficiently incorporated into MLV core particles. These pseudotype particles infected the SNV permissive cell line D17 at titers of up to 10(5) IU/ml. A stable packaging cell line (MS4) of human origin released MLV(SNV) pseudotype vectors that were resistant against human complement inactivation. To redirect their tropism to human T cells, MS4 cells were transfected with the expression gene encoding the scFv 7A5 in fusion with the transmembrane domain (TM) of the SNV Env protein, previously shown to retarget SNV vector particles to human lymphocytes. MLV(SNV-7A5)-vector particles released from these cells were selectively infectious for human T cell lines. The data provide a proof of principle for targeting MLV-derived vectors to subpopulations of human cells through pseudotyping with SNV targeting envelopes.

Animals↗
PubMed2001

Conditioned brain-stimulation reward attenuates the acoustic startle reflex in rats.

The acoustic startle reflex (ASR) in rats is attenuated by a light paired with food or, in humans, by "pleasant" pictures. Rats were trained to barpress for lateral hypothalamus (LH) stimulation. ASR amplitudes were then measured at 4 intensities, with or without a light. Control rats that did not receive brain-stimulation reward (BSR) showed initially lower ASR amplitudes than did rats exposed to BSR, but both groups responded similarly with or without light. Next, experimental rats were given BSR in the presence of light but not in its absence. After conditioning, ASR amplitudes were reduced, and ASR thresholds were raised by a mean of 2.6 dB in the light but remained at preconditioning levels without light. No such change was found for control rats or rats with placements outside the LH.

Acoustic Stimulation↗
PubMed2000

MLV-derived retroviral vectors selective for CD4-expressing cells and resistant to neutralization by sera from HIV-infected patients.

Retroviral vectors derived from amphotropic murine leukemia viruses (MLV) mediate gene transfer into almost all human cells and are thus not suitable for in vivo applications in gene therapy in which cell-specific gene delivery is required. We and others recently reported the generation of MLV-derived vectors pseudotyped by variants of the envelope glycoproteins (Env) of human immunodeficiency virus type 1 (HIV-1), thus displaying the CD4-dependent tropism of the parental lentivirus (Mammano et al., 1997, J. Virol. 71, 3341-3345; Schnierle et al., 1997, Proc. Natl. Acad. Sci. USA 76, 8640-8645). However, because of their HIV-1-derived envelopes these vectors are neutralized by HIV-specific antibodies present in some infected patients. To circumvent this problem, we pseudotyped MLV capsid particles with variants of Env proteins derived from the apathogenic simian immunodeficiency virus (SIVagm) of African green monkeys (AGM; Chlorocebus pygerythrus). Truncation of the C-terminal domain of the transmembrane protein was found to be necessary to allow formation of infectious pseudotype vectors. These [MLV(SIVagm)] vectors efficiently transduced various human CD4-expressing cell lines using the coreceptors CCR5 and Bonzo to enter target cells. Moreover, they were resistant to neutralization by antibodies directed against HIV-1. Therefore, [MLV(SIVagm)] vectors will be useful to study the mechanisms of SIVagm cell entry and for the selective gene transfer into CD4+ T-cells of AIDS patients.

Amino Acid Sequence↗
PubMed1999

Survival differences associated with treatment of cytomegalovirus retinitis in Maryland patients with AIDS, 1987-1994.

Differences in survival related to treatment of cytomegalovirus (CMV) retinitis in AIDS patients were studied. The medical records of adult AIDS patients who had been diagnosed with CMV retinitis in a Maryland inpatient facility between September 1987 and September 1994 were reviewed to assess determinants of survival, including treatment with ganciclovir and foscarnet, use of zidovudine, and demographic characteristics. The review was based on inpatient and outpatient medical records and computerized data from the Maryland HIV Information System. Of 212 AIDS patients with CMV retinitis, 123 (58.0%) were treated exclusively with ganciclovir, 55 (25.9%) received foscarnet only, and the remaining 34 (16.1%) received both ganciclovir and foscarnet at some point after their diagnosis for CMV retinitis. Patients who received both drugs survived significantly longer after the diagnosis than patients who received either drug by itself. The median time from diagnosis of CMV retinitis to death was 464 days for patients receiving both drugs, 225 days for ganciclovir recipients, and 202 days for foscarnet recipients. Other positive predictors of survival were male sex and use of zidovudine. Among Maryland adults with AIDS who were treated for CMV retinitis between September 1987 and September 1994, the most common treatment for the eye infection was ganciclovir. Patients receiving both ganciclovir and foscarnet survived longer than those treated with either drug alone.

AIDS-Related Opportunistic Infections↗
PubMed1999

Cloning and characterization of an Aspergillus nidulans gene involved in the regulation of penicillin biosynthesis.

To identify regulators of penicillin biosynthesis, a previously isolated mutant of Aspergillus nidulans (Prg-1) which carried the trans-acting prgA1 mutation was used. This mutant also contained fusions of the penicillin biosynthesis genes acvA and ipnA with reporter genes (acvA-uidA and ipnA-lacZ) integrated in a double-copy arrangement at the chromosomal argB gene. The prgA1 mutant strain exhibited only 20 to 50% of the ipnA-lacZ and acvA-uidA expression exhibited by the wild-type strain and had only 20 to 30% of the penicillin produced by the wild-type strain. Here, using complementation with a genomic cosmid library, we isolated a gene (suAprgA1) which complemented the prgA1 phenotype to the wild-type phenotype; i.e., the levels of expression of both gene fusions and penicillin production were nearly wild-type levels. Analysis of the suAprgA1 gene in the prgA1 mutant did not reveal any mutation in the suAprgA1 gene or unusual transcription of the gene. This suggested that the suAprgA1 gene is a suppressor of the prgA1 mutation. The suAprgA1 gene is 1,245 bp long. Its five exons encode a deduced protein that is 303 amino acids long. The putative SUAPRGA1 protein was similar to both the human p32 protein and Mam33p of Saccharomyces cerevisiae. Analysis of the ordered gene library of A. nidulans indicated that suAprgA1 is located on chromosome VI. Deletion of the suAprgA1 gene resulted in an approximately 50% reduction in ipnA-lacZ expression and in a slight reduction in acvA-uidA expression. The DeltasuAprgA1 strain produced about 60% of the amount of penicillin produced by the wild-type strain.

Amino Acid Sequence↗
PubMed1999

Sensitivity and specificity of dipstick tests for rapid diagnosis of malaria in nonimmune travelers.

Swift diagnosis of Plasmodium falciparum malaria in areas where the disease is not endemic is frequently complicated by the lack of experience on the side of involved laboratory personal. Diagnostic tools based on the dipstick principle for the detection of plasmodial histidine-rich protein 2 (HRP-2) and parasite-specific lactate dehydrogenase (pLDH), respectively, have become available for the qualitative detection of P. falciparum malaria. In order to evaluate two of the currently available assays, specimens from 231 patients were screened during a prospective multicenter study. Among the screened specimens, samples from 53 patients (22.9%) were positive for P. falciparum malaria by microscopy and/or PCR. While the test kit based on the detection of HRP-2 performed with a sensitivity of 92.5% and a specificity of 98.3%, the kit for the detection of pLDH showed a sensitivity of 88.5% and a specificity of 99.4%. Dipstick tests have the potential of enhancing speed and accuracy of the diagnosis of P. falciparum malaria, especially if nonspecialized laboratories are involved.

Biomarkers↗
PubMed1999

AnCF, the CCAAT binding complex of Aspergillus nidulans, contains products of the hapB, hapC, and hapE genes and is required for activation by the pathway-specific regulatory gene amdR.

CCAAT binding factors (CBFs) positively regulating the expression of the amdS gene (encoding acetamidase) and two penicillin biosynthesis genes (ipnA and aatA) have been previously found in Aspergillus nidulans. The factors were called AnCF and PENR1, respectively. Deletion of the hapC gene, encoding a protein with significant similarity to Hap3p of Saccharomyces cerevisiae, eliminated both AnCF and PENR1 binding activities. We now report the isolation of the genes hapB and hapE, which encode proteins with central regions of high similarity to Hap2p and Hap5p of S. cerevisiae and to the CBF-B and CBF-C proteins of mammals. An additional fungus-specific domain present in HapE was revealed by comparisons with the homologs from S. cerevisiae, Neurospora crassa, and Schizosaccharomyces pombe. The HapB, HapC, and HapE proteins have been shown to be necessary and sufficient for the formation of a CCAAT binding complex in vitro. Strains with deletions of each of the hapB, hapC, and hapE genes have identical phenotypes of slow growth, poor conidiation, and reduced expression of amdS. Furthermore, induction of amdS by omega amino acids, which is mediated by the AmdR pathway-specific activator, is abolished in the hap deletion mutants, as is growth on gamma-aminobutyric acid as a sole nitrogen or carbon source. AmdR and AnCF bind to overlapping sites in the promoters of the amdS and gatA genes. It is known that AnCF can bind independently of AmdR. We suggest that AnCF binding is required for AmdR binding in vivo.

Amidohydrolases↗
PubMed1998

Race and the treatment of cytomegalovirus retinitis in a cohort of patients with acquired immunodeficiency syndrome.

This historical cohort study assessed the impact of race on critical factors in the diagnosis and drug treatment of cytomegalovirus (CMV) retinitis in acquired immunodeficiency syndrome (AIDS) patients over a 7-year period. The study subjects included 194 adult patients with a history of AIDS who were treated for CMV retinitis between September 1987 and September 1994. Abstracted inpatient hospital medical records and a statewide automated AIDS database were the primary sources of data. Patients were assessed for severity of CMV retinitis at diagnosis, time from initial CMV retinitis diagnosis to first treatment, survival from diagnosis of AIDS, and initiation of drug treatment for CMV retinitis. Results indicated a significant difference in the severity of CMV retinitis at diagnosis by race. Patients diagnosed with early disease were more likely to be white, whereas patients diagnosed with severe disease were more likely to be black. There was no difference in the type of CMV retinitis treatment or patient survival time after diagnosis, nor time to treatment once diagnosed by race. These results suggest that differences in survival may not be the result of discrimination against black patients and may be due more likely to practices associated with accessing medical treatment.

AIDS-Related Opportunistic Infections↗
PubMed1991

Selective alpha 2-adrenergic agonists B-HT 920 and UK14304-18. Effects on aqueous humor dynamics in monkeys.

Selective alpha 2-adrenergic agonists UK14304-18 and B-HT 920 were evaluated in the eyes of cynomolgus monkeys. In normal monkeys, unilateral topical application of 0.3%, 0.5%, or 1% UK14304-18 or B-HT 920 reduced (P less than .05) intraocular pressure bilaterally up to 9.9 +/- 1.2 mm Hg (mean +/- SEM) and 8.4 +/- 1.4 mm Hg in treated and contralateral eyes, respectively. Five-day twice-daily 0.5% UK14304-18 administration reduced (P less than .05) intraocular pressure up to 49% in eight glaucomatous monkeys. In eight normal monkeys, 0.5% B-HT 920 and 0.5% UK14304-18 produced no alterations in outflow facility. Following unilateral application of 0.5% B-HT 920 or 0.5% UK14304-18, fluorophotometrically measured aqueous humor production was reduced (P less than .05) bilaterally up to 67% compared with baseline values. Also, 0.5% UK14304-18 reduced (P less than .025) systolic and diastolic blood pressure. UK14304-18 and B-HT 920 seem to reduce intraocular pressure by decreasing aqueous production. They are potential new agents for the treatment of glaucoma.

Administration, Topical↗