PubMed Health⌕ Search

Biomedical subjects

T Stein

Publications and source records attributed to T Stein.

At least 19 recordsLinked to original sources
PubMed2003

(-)-PHCCC, a positive allosteric modulator of mGluR4: characterization, mechanism of action, and neuroprotection.

Group-III metabotropic glutamate receptors (mGluR4, -6, -7, and -8) modulate neurotoxicity of excitatory amino acids and beta-amyloid-peptide (betaAP), as well as epileptic convulsions, most likely via presynaptic inhibition of glutamatergic neurotransmission. Due to the lack of subtype-selective ligands for group-III receptors, we previously utilized knock-out mice to identify mGluR4 as the primary receptor mediating neuroprotection of unselective group-III agonists such as L-AP(4) or (+)-PPG, whereas mGluR7 is critical for anticonvulsive effects. In a recent effort to find group-III subtype-selective drugs we identified (+/-)-PHCCC as a positive allosteric modulator for mGluR4. This compound increases agonist potency and markedly enhances maximum efficacy and, at higher concentrations, directly activates mGluR4 with low efficacy. All the activity of (+/-)-PHCCC resides in the (-)-enantiomer, which is inactive at mGluR2, -3, -5a, -6, -7b and -8a, but shows partial antagonist activity at mGluR1b (30% maximum antagonist efficacy). Chimeric receptor studies showed that the binding site of (-)-PHCCC is localized in the transmembrane region.Finally, (-)-PHCCC showed neuroprotection against betaAP- and NMDA-toxicity in mixed cultures of mouse cortical neurons. This neuroprotection was additive to that induced by the highly efficacious mGluR1 antagonist CPCCOEt and was blocked by MSOP, a group-III mGluR antagonist. Our data provide evidence for a novel pharmacological site on mGluR4, which may be used as a target-site for therapeutics.

Amyloid beta-Peptides↗
PubMed2002

Retrospective study of 46 cases of feline haemobartonellosis in Israel and their relationships with FeLV and FIV infections.

Forty-six cats with clinical haemobartonellosis were studied; 75 per cent of the cats of known age were two-and-a-half years old or younger, 50 per cent were intact males and 19.5 per cent were castrated males. The predominant signs of the disease were tachypnoea, lethargy, depression, anorexia, infestation with fleas, pale mucous membranes, icterus, emaciation, dehydration, splenomegaly, anaemia, leucocytosis, increased activities of alanine aminotransferase and aspartate aminotransferase, and azotaemia. Thirty-eight per cent of the cats that were tested for feline leukaemia virus (FeLV) antigen were positive, and 22 per cent of those tested for feline immunodeficiency virus (FIV) antibodies were positive. The prevalence of both FeLV and FIV was much higher than in the general Israeli cat population. The cats infected with both Haemobartonella felis and FeLV had a significantly lower body temperature, were more anaemic and the mean cell volume of their erythrocytes was greater than in the cats with haemobartonellosis alone.

Anaplasmataceae Infections↗
PubMed2002

Energy metabolism pathways in rat muscle under conditions of simulated microgravity.

Evidence from rats flown in space suggests that there is a decrease in the ability of the soleus muscle to oxidize long chain fatty acids during space flight. The observation suggests that a shift in the pathways involved in muscle fuel utilization in the absence of load on the muscle has occurred. It is also possible that the reduction is part of a general down-sizing of metabolic capacity since energy needs of inactive muscle are necessarily less. The rodent hind limb suspension model has proved to be a useful ground based model for studying the musculo-skeletal systems changes that occur with space flight. Microarray technology permits the screening of a large number of the enzymes of the relevant pathways thereby permitting a distinction to be made between a shift fuel utilization pattern or a general decrease in metabolic activity. The soleus muscle was isolated from 5 control and 5 hindlimb suspended rats (21 days) and the Affymetrix system for assessing gene expression used to determine the impact of hindlimb unloading on fuel pathways within the muscle of each animal. RESULTS: Suspended rats failed to gain weight at the same rate as the controls (337 +/- 5 g vs 318 +/- 6 g, p < 0.05) and muscle mass from the soleus was reduced (135 +/- 3 mg vs 48 +/- 4 mg, p < 0.05). There was a consistent decrease (p < 0.05) in gene expression of proteins involved in fatty acid oxidation in the suspended group whereas glycolytic activity was increased (p < 0.05). Gene expressions of individual key regulatory enzymes reflected these changes. Carnitine palmitoyltransferase I and II were decreased (p < 0.05) whereas expression of hexokinase, phosphofructokinase and pyruvate kinase were increased (p < 0.05). CONCLUSION: Disuse atrophy is associated with a change in mRNA levels of enzymes involved in fuel metabolism indicative of a shift in substrate utilization away from fat towards glucose.

Journal Article↗
PubMed2001

C-terminal interaction is essential for surface trafficking but not for heteromeric assembly of GABA(b) receptors.

Assembly of fully functional GABA(B) receptors requires heteromerization of the GABA(B(1)) and GABA(B(2)) subunits. It is thought that GABA(B(1)) and GABA(B(2)) undergo coiled-coil dimerization in their cytoplasmic C termini and that assembly is necessary to overcome GABA(B(1)) retention in the endoplasmatic reticulum (ER). We investigated the mechanism underlying GABA(B(1)) trafficking to the cell surface. We identified a signal, RSRR, proximal to the coiled-coil domain of GABA(B(1)) that when deleted or mutagenized allows for surface delivery in the absence of GABA(B(2)). A similar motif, RXR, was recently shown to function as an ER retention/retrieval (ERR/R) signal in K(ATP) channels, demonstrating that G-protein-coupled receptors (GPCRs) and ion channels use common mechanisms to control surface trafficking. A C-terminal fragment of GABA(B(2)) is able to mask the RSRR signal and to direct the GABA(B(1)) monomer to the cell surface, where it is functionally inert. This indicates that in the heteromer, GABA(B(2)) participates in coupling to the G-protein. Mutagenesis of the C-terminal coiled-coil domains in GABA(B(1)) and GABA(B(2)) supports the possibility that their interaction is involved in shielding the ERR/R signal. However, assembly of heteromeric GABA(B) receptors is possible in the absence of the C-terminal domains, indicating that coiled-coil interaction is not necessary for function. Rather than guaranteeing heterodimerization, as previously assumed, the coiled-coil structure appears to be important for export of the receptor complex from the secretory apparatus.

Amino Acid Motifs↗
PubMed2001

Structure of the Bacillus subtilis peptide antibiotic subtilosin A determined by 1H-NMR and matrix assisted laser desorption/ionization time-of-flight mass spectrometry.

Subtilosin A produced by Bacillus subtilis is a macrocyclic peptide antibiotic which comprises 35 amino acids. Its molecular mass (3399.7 Da), determined by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and chemical properties gave experimental support for unusual intramolecular linkages. The three-dimensional fold of native subtilosin in dimethylsulfoxide was determined from two-dimensional 1H-NMR spectra recorded at 600 MHz. Based on the backbone conformation, a structure for subtilosin A is presented which is characterized by three inter-residue bridges where two cysteines are linked with two phenylalanine residues, respectively, and a third cysteine is bound to a threonine residue.

Amino Acid Sequence↗
PubMed2001

The tetraheme cytochrome c NrfH is required to anchor the cytochrome c nitrite reductase (NrfA) in the membrane of Wolinella succinogenes.

The electron-transport chain that catalyzes nitrite respiration with formate in Wolinella succinogenes consists of formate dehydrogenase, menaquinone and the nitrite reductase complex. The latter catalyzes nitrite reduction by menaquinol and is made up of NrfA and NrfH, two c-type cytochromes. NrfA is the catalytic subunit; its crystal structure is known. NrfH belongs to the NapC/NirT family of membrane-bound c-type cytochromes and mediates electron transport between menaquinol and NrfA. It is demonstrated here by MALDI MS that four heme groups are attached to NrfH. A Delta nrfH deletion mutant of W. succinogenes was constructed by replacing the nrfH gene with a kanamycin-resistance gene cartridge. This mutant did not form the NrfA protein, probably because of a polar effect of the mutation on nrfA expression. The nrfHAIJ gene cluster was restored by integration of an nrfH-containing plasmid into the genome of the Delta nrfH mutant. The resulting strain had wild-type properties with respect to growth by nitrite respiration and nitrite reductase activity. A mutant (stopH) that contained the nrfHAIJ locus with nrfH modified by two artificial stop codons near its 5' end produced wild-type amounts of NrfA in the absence of the NrfH protein. NrfA was located exclusively in the soluble cell fraction of the stopH mutant, indicating that NrfH acts as the membrane anchor of the NrfHA complex in wild-type bacteria. The stopH mutant did not grow by nitrite respiration and did not catalyze nitrite reduction by formate, indicating that the electron transport is strictly dependent on NrfH. The NrfH protein seems to be an unusual member of the NapC/NirT family as it forms a stable complex with its redox partner protein NrfA.

Base Sequence↗
PubMed2001

Communication challenges for experienced clinicians: topics for an advanced communication curriculum.

We asked 111 experienced clinicians (MDs, RNs, PhDs, DMins) attending a conference on medical interviewing for descriptions of communication challenges they encountered while practicing in clinical health care settings. Eighty-one provided accounts analyzed in this study. Using narrative analysis, we found that most of the accounts focused on conflicts between clinicians and patients based on differing beliefs about the nature and treatment of illness and contrasting expectations about the doctor-patient relationship. This article traces the clinician-narrators' use of plot, characterization, cause-effect relationships, and idealized images to make sense of challenging communication encounters. The results of our analysis point to several communication competencies that experienced clinicians found they lacked, even af ter receiving communication training and developing an awareness of the literature on teaching health communication skills. Building skills in the identified areas could reduce clinician frustration and enrich the practice of medicine.

Adult↗
PubMed2000

RNA polymerase III transcription: its control by tumor suppressors and its deregulation by transforming agents.

The level of RNA polymerase (pol) III transcription is tightly linked to the rate of growth; it is low in resting cells and increases following mitogenic stimulation. When mammalian cells begin to proliferate, maximal pol III activity is reached shortly before the G1/S transition; it then remains high throughout S and G2 phases. Recent data suggest that the retinoblastoma protein RB and its relatives p107 and p130 may be largely responsible for this pattern of expression. During G0 and early G1 phase, RB and p130 bind and repress the pol III-specific factor TFIIIB; shortly before S phase they dissociate from TFIIIB, allowing transcription to increase. At the end of interphase, when cells enter mitosis, pol III transcription is again suppressed; this mitotic repression is achieved through direct phosphorylation of TFIIIB. Thus, pol III transcription levels fluctuate as mammalian cells cycle, being high in S and G2 phases and low during mitosis and early G1. In addition to this cyclic regulation, TFIIIB can be bound and repressed by the tumor suppressor p53. Conversely, it is a target for activation by several viruses, including SV40, HBV, and HTLV-1. Some viruses also increase the activity of a second pol III-specific factor called TFIIIC. A large proportion of transformed and tumor cell types express abnormally high levels of pol III products. This may be explained, at least in part, by the very high frequency with which RB and p53 become inactivated during neoplastic transformation; loss of function of these cardinal tumor suppressors may release TFIIIB from key restraints that operate in normal cells.

Animals↗
PubMed2000

Functional connectivity in the thalamus and hippocampus studied with functional MR imaging.

BACKGROUND AND PURPOSE: With functional connectivity functional MR imaging, co-variance in signal intensity has been shown in functionally related regions of brain in participants instructed to perform no cognitive task. These changes are thought to represent synchronous fluctuations in blood flow, which imply neuronal connections between the regions. The purpose of this study was to map functional connectivity in subcortical nuclei with functional connectivity functional MR imaging. METHODS: Imaging data were acquired with an echo-planar sequence from six volunteers who performed no specific cognitive task. For functional connectivity functional MR imaging, a "seed" voxel or group of voxels was selected from the resting data set in the thalamus or in the hippocampus. Control voxels in gray matter presumed not to be eloquent cortex were also chosen. The correlation coefficient of the seed voxels and the control voxels with every other voxel in the resting data set was calculated. The voxels with correlation coefficients greater than or equal to 0.5 were mapped onto anatomic images for the functional connectivity functional MR images. The anatomic location of these voxels was determined by conventional parcellation methods. RESULTS: For each participant, functional connectivity functional MR imaging maps based on four seed voxels in the thalamus or hippocampus showed clusters of voxels in the ipsilateral and contralateral thalamus or hippocampus. For control voxels, few voxels in the hippocampus or thalamus showed significant correlation. Significantly more pixels in the ipsilateral hippocampus correlated with the seed voxel than in the contralateral hippocampus. The differences between numbers of functionally connected voxels in ipsilateral thalamus and those in contralateral thalamus were not significant. CONCLUSIONS: The thalamus and hippocampus show functional connectivity, presumably representing synchronous changes in blood flow.

Adult↗
PubMed2000

Capnography in EMS.

Explore the source record for details and available documents.

Allied Health Personnel↗
PubMed1999

The mycosubtilin synthetase of Bacillus subtilis ATCC6633: a multifunctional hybrid between a peptide synthetase, an amino transferase, and a fatty acid synthase.

Bacillus subtilis strain ATCC6633 has been identified as a producer of mycosubtilin, a potent antifungal peptide antibiotic. Mycosubtilin, which belongs to the iturin family of lipopeptide antibiotics, is characterized by a beta-amino fatty acid moiety linked to the circular heptapeptide Asn-Tyr-Asn-Gln-Pro-Ser-Asn, with the second, third, and sixth position present in the D-configuration. The gene cluster from B. subtilis ATCC6633 specifying the biosynthesis of mycosubtilin was identified. The putative operon spans 38 kb and consists of four ORFs, designated fenF, mycA, mycB, and mycC, with strong homologies to the family of peptide synthetases. Biochemical characterization showed that MycB specifically adenylates tyrosine, as expected for mycosubtilin synthetase, and insertional mutagenesis of the operon resulted in a mycosubtilin-negative phenotype. The mycosubtilin synthetase reveals features unique for peptide synthetases as well as for fatty acid synthases: (i) The mycosubtilin synthase subunit A (MycA) combines functional domains derived from peptide synthetases, amino transferases, and fatty acid synthases. MycA represents the first example of a natural hybrid between these enzyme families. (ii) The organization of the synthetase subunits deviates from that commonly found in peptide synthetases. On the basis of the described characteristics of the mycosubtilin synthetase, we present a model for the biosynthesis of iturin lipopeptide antibiotics. Comparison of the sequences flanking the mycosubtilin operon of B. subtilis ATCC6633, with the complete genome sequence of B. subtilis strain 168 indicates that the fengycin and mycosubtilin lipopeptide synthetase operons are exchanged between the two B. subtilis strains.

Adenosine Monophosphate↗
PubMed1999

Resolving disagreements in the patient-physician relationship: tools for improving communication in managed care.

Managed care uses financial incentives and restrictions on tests and procedures to attempt to influence physician decision making and limit costs. Increasingly, the public is questioning whether physicians are truly making decisions based on the patient's best interest or are unduly influenced by economic incentives. These circumstances lead to the potential for disagreements and conflict in the patient-physician relationship. We convened a group of individuals in October 1998, including patient representatives, leaders from health care organizations, practicing physicians, communication experts, and medical ethicists, to articulate the types of disagreements emerging in the patient-physician relationship as a result of managed care. We addressed 3 specific scenarios physicians may encounter, including allocation, illustrated by a patient who is referred to a different ophthalmologist based on a new arrangement in the physician's group; access, illustrated by a patient who wishes to see his own physician for a same-day visit rather than a nurse specialist; and financial incentives, illustrated by a patient who expects to have a test performed and a physician who does not believe the test is necessary but is afraid the patient will think the physician is not ordering the test because of financial incentives. Using these scenarios, we suggest communication strategies that physicians can use to decrease the potential for disagreements. In addition, we propose strategies that health plans or physician groups can use to alleviate or resolve these disagreements.

Communication↗
PubMed1999

Expression studies and promoter analysis of the nuclear gene for mitochondrial transcription factor 1 (MTF1) in yeast.

The basal mitochondrial transcription apparatus of Saccharomyces cerevisiae consists of the core enzyme for mitochondrial RNA polymerase and the specificity factor. The core enzyme is homologous to those of bacteriophages T3, T7 and SP6 whereas the specificity factor shows similarities with bacterial sigma factors. Recently it was shown that the bacteriophage-type core enzyme is widespread among the eukaryotic lineage and a common picture for the mitochondrial transcription apparatus in eukaryotic cells is now emerging. In contrast to the situation for the core enzyme, the gene for the specificity factor has only been identified from S. cerevisiae and more recently from two other yeast species. As the specificity factor is the key component for initiation of transcription at the mitochondrial promoter we wanted to study in more detail gene expression, regulation, and the function of the promoter of the nuclear MTF1 gene. For this purpose the messenger RNA level for scMTF1 was investigated under a large number of different growth conditions and thereby exhibited a very low, but regulated and carbon source-dependent, expression. Deletion experiments identify the minimal promoter for functional complementation in yeast. To evaluate the functional conservation of the promoter elements the homologous MTF1 gene from the closely related yeast Saccharomyces douglasii was isolated and tested in heterologous complementation experiments. In spite of a highly conserved protein sequence these studies demonstrate that at low-copy number sdMTF1 is not able to substitute for scMTF1 in S. cerevisiae. Promoter exchange experiments with MTF1 from S. cerevisiae and S. douglasii demonstrate that differences in gene expression are responsible for the failure in heterologous complementation. This finding prompted us to compare the promoter regions of MTF1 from four different yeast species. For this purpose the sequences of the 5' regions from S. douglasii, S. kluyveri and Kluyveromyces lactis were determined. A comparison of these sequences identifies significant differences and rapid changes in the intergenic regions, even between closely related yeast species.

5' Untranslated Regions↗
PubMed1999

Noninvasive assessment of coronary flow reserve with transthoracic signal-enhanced Doppler echocardiography.

OBJECTIVES: The feasibility of noninvasive assessment of coronary flow reserve (CFR) in the distal left anterior descending artery (LAD) with echocardiography-enhanced transthoracic pulsed wave Doppler guided by high-resolution transthoracic color Doppler (TTCD) was investigated. The results were compared with the degree of coronary diameter stenosis obtained during cardiac catheterization. BACKGROUND: Assessment of CFR has proven to be useful in the selection of patients undergoing invasive treatment of coronary artery disease and in estimating their prognosis. However, CFR could only be determined invasively in everyday practice during catheterization procedures. Recent development of high-resolution TTCD allows transthoracic visualization of distal LAD and supra-apical intramyocardial perforator branches and noninvasive measurement of CFR with pulsed wave Doppler technique. METHODS: CFR was determined by measuring the ratio of pulsed wave Doppler time velocity integral during adenosine-induced hyperemia (140 microgram/kg/min intravenously) to baseline value. If the baseline Doppler signal of LAD flow was insufficient, an echocardiography (echo) enhancer (Levovist) was used. Forty-five patients were examined by TTCD (7-MHz B-mode, 5-MHz color Doppler, and 3.5-MHz pulsed wave Doppler) after coronary angiography had been performed. Group 1 consisted of 15 patients without heart disease, group 2 of 15 patients with 50% to 85% isolated LAD diameter stenosis, and group 3 of 15 patients with >85% LAD diameter stenosis. RESULTS: Peripheral LAD coronary flow at baseline condition was assessed in 40 (88%) patients with TTCD. CFR could be quantified in 36 (80%) of the 45 patients: in 18 patients without echo enhancer, and in 18 patients with echo-enhancing agent. CFR could not be assessed in 9 (20%) patients. CFR in the various groups was as follows: group 1, 3. 13 +/- 0.57; group 2, 2.23 +/- 0.20 (vs group 1: P <.01); and group 3, 1.64 +/- 0.30 (vs group 2: P <.02). CONCLUSION: CFR in the LAD can be determined in 80% of patients with pulsed wave Doppler guided by high-resolution TTCD combined with intravenously administered echo-enhancing agent.

Aged↗
PubMed1999

Structural and functional organization of the fengycin synthetase multienzyme system from Bacillus subtilis b213 and A1/3.

BACKGROUND: Bacillus subtilis strains produce a broad spectrum of lipopeptides that are potent biosurfactants and have specific antimicrobial and antiviral activities. The cyclic lipodecapeptide fengycin is one such compound. Although the fengycin biosynthetic genes in B. subtilis 168 (pps genes) and F29-3 (fen genes) have been well characterized, only limited information is available about the biochemical features of the fengycin synthetase multienzyme system. RESULTS: Five multifunctional peptide synthetases (Fen1-5) that catalyze biosynthesis of the peptide portion of fengycin have been purified from crude extracts of the B. subtilis b213 and A1/3 strains. These enzymes activate all fengycin amino-acid components as aminoacyl adenylates or aminoacyl thioesters. Fen1, Fen2 and Fen3 are each approximately 286 kDa, Fen4 is approximately 400 kDa and Fen 5 is approximately 140kDa; each enzyme activates a different set of L-amino acids. A five-gene cluster (fen1-5) was detected in the B. subtilis A1/3 genome that shows high homology to the pps and fen genes in B. subtilis strains 168 and F29-3. Disruption of fen4 resulted in a loss of fengycin production. The fengycin synthetase enzymes isolated from B. subtilis b213 were assigned to the corresponding A1/3 fen genes by their amino-terminal sequences. CONCLUSIONS: The structural and functional organization of the fengycin synthetase system from B. subtilis b213 has been characterized in detail and correlated with the corresponding pps and fen genes in B. subtilis strains 168, A1/3 and F29-3. Biosynthesis of the peptide part of fengycin involves five multifunctional modular proteins that assemble the lipopeptide chain using a nonribosomal, multiple carrier thiotemplate mechanism.

Amino Acid Sequence↗
PubMed1999

The single cysteine residue of the Sud protein is required for its function as a polysulfide-sulfur transferase in Wolinella succinogenes.

The periplasmic Sud protein which is induced in Wolinella succinogenes growing by polysulfide respiration, has been previously proposed to serve as a polysulfide binding protein and to transfer polysulfide-sulfur to the active site of polysulfide reductase [Klimmek, O, Kreis, V., Klein, C., Simon, J., Wittershagen, A. & Kröger, A. (1998) Eur. J. Biochem. 253, 263-269.]. The results presented in this communication suggest that polysulfide-sulfur is covalently bound to the single cysteine residue (Cys109) of the Sud monomer, and that Cys109 is required for tight binding of polysulfide-sulfur and for sulfur transfer. A modified Sud protein [(C109S)Sud-His6] in which the cysteine residue was replaced by serine, did not catalyze sulfur transfer from polysulfide to cyanide and did not stimulate electron transport to polysulfide, in contrast to Sud-His6. The polysulfide-sulfur bound to (C109S)Sud-His6 was fully removed upon dialysis against sulfide. After this treatment, Sud-His6 retained one sulfur atom per monomer; thiocyanate was formed upon addition of cyanide to the preparation. After incubation of Sud-His6 with polysulfide, a proportion of the Sud-His6 monomers carried one or two sulfur atoms, as shown by matrix-assisted laser desorption ionization mass spectrometry. The sulfur atoms were absent from monomers derived from Sud-His6 treated with cyanide and from (C109S)Sud-His6 incubated with polysulfide.

Amino Acid Substitution↗
PubMed1999

A new system for a combined laser and ultrasound application in neurosurgery.

A new combined Laser and Ultrasound Surgical Therapy (LUST) device suitable for endoscopical coagulation and tissue fragmentation has been developed at the LMTB. The new feature is the simultaneous transmission of laser radiation and ultrasound via flexible silica glass fibers. The ultrasound tissue interaction is based on the well-known CUSA-technology which enables the surgeon to cut various types of tissue with different degrees of effectiveness. Application fields are in oncology, neurosurgery and angioplasty. The laser radiation can be used, for example, for tissue coagulation purposes. With a fiber based LUST-system working at a frequency of 30 kHz, a displacement of 100 microns could be attained at the distal end. (The usual standard CUSA displacement is 10-350 microns.) During in vitro experiments the following tissue fragmentation rates could be achieved: brain tissue 50 mg sec-1, liver 4.5 mg sec-1 and kidney 4 mg sec-1 (displacement of the tip 60 microns; phi 1.3 mm; suction setting: 5 W). Laser radiation up to 25 W was sufficient to coagulate soft tissue. This technology offers new possibilities in minimal invasive surgery. The flexible opto-acoustic waveguide (phi 400-1700 microns) can be bent making areas accessible that were previously inaccessible. Without changing the instrumentation the surgeon can use the laser radiation for tissue coagulation or cutting and the ultrasound for tissue fragmentation and tissue reduction.

Animals↗