Search PubMed⌕ Search

Biomedical subjects

T Steiner

Publications and source records attributed to T Steiner.

At least 55 records · Page 3Linked to original sources
PubMed2000

Changes in cerebral blood flow and oxygen metabolism during moderate hypothermia in patients with severe middle cerebral artery infarction.

OBJECT: Moderate hypothermia has been reported to be effective in the treatment of postischemic brain edema. The effect of hypothermia on cerebral hemodynamics is a matter of controversial discussion in literature. Clinical studies have yet to be performed in patients with ischemic stroke after induction of hypothermia. METHODS: Measurements during mild hypothermia (33-34 degrees C) were made in six patients with severe ischemic stroke involving the middle cerebral artery territory. Hypothermia was induced as soon as possible and maintained for 48 to 72 hours. Cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2) were estimated by a new double-indicator dilution method. Measurements of CBF were made during normothermia, immediately after induction of hypothermia, at the end of hypothermia, and after rewarming. A total of 19 measurements of CBF and jugular bulb O2 saturation were made. Immediately after induction of hypothermia, CBF decreased in all patients. During late hypothermia, CBF improved in patients who survived but remained diminished in the two patients who died. Reduced CMRO2 levels were observed during all phases of hypothermia in all but one case. CONCLUSIONS: Preliminary oberservations indicate that moderate hypothermia seems to reduce CMRO2. Immediately after induction of hypothermia, CBF may decrease in all patients. During late hypothermia CBF seems to recover in patients with good outcome but remains diminished in patients who die. Serial bedside CBF measurements with the new double-indicator dilution technique may be useful to describe cerebral hemodynamic characteristics in patients with severe ischemic stroke during hypothermia.

Adult↗
PubMed2000

Active-site gorge and buried water molecules in crystal structures of acetylcholinesterase from Torpedo californica.

Buried water molecules and the water molecules in the active-site gorge are analyzed for five crystal structures of acetylcholinesterase from Torpedo californica in the resolution range 2.2-2.5 A (native enzyme, and four inhibitor complexes). A total of 45 buried hydration sites are identified, which are populated with between 36 and 41 water molecules. About half of the buried water is located in a distinct region neighboring the active-site gorge. Most of the buried water molecules are very well conserved among the five structures, and have low displacement parameters, B, of magnitudes similar to those of the main-chain atoms of the central beta-sheet structure. The active-site gorge of the native enzyme is filled with over 20 water molecules, which have poor hydrogen-bond coordination with an average of 2.9 polar contacts per water molecule. Upon ligand binding, distinct groups of these water molecules are displaced, whereas the others remain in positions similar to those that they occupy in the native enzyme. Possible roles of the buried water molecules are discussed, including their possible action as a lubricant to allow large-amplitude fluctuations of the loop structures forming the gorge wall. Such fluctuations are required to facilitate traffic of substrate, products and water molecules to and from the active-site. Because of their poor coordination, the gorge water molecules can be considered as "activated" as compared to bulk water. This should allow their easy displacement by incoming substrate. The relatively loose packing of the gorge water molecules leaves numerous small voids, and more efficient space-filling by substrates and inhibitors may be a major driving force of ligand binding.

Acetylcholinesterase↗
PubMed2000

Elevated plasma TGF-beta1 in renal diseases: cause or consequence?

We previously reported elevated levels of TGF-beta1 in patients with renal carcinoma. Certain aspects led us to ask whether they might be caused by chronic damage to the kidney(s). Here we report on an extended set of patients with various renal diseases, lung cancer, humoral immunodeficiency and controls. For latent TGF-beta1 in plasma, we find that the control, immunodeficiency, lung cancer and kidney transplant groups do not differ significantly (means, 7.0-8.8 ng/ml). Also, acute short-term renal stress (extracorporal lithotrypsy) does not lead to an increase of TGF-beta1. However, the pyelonephritis patients present with levels of 19.0 ng/ml, chronic extracorporal dialysis patients with 15.5 ng/ml, and renal cell carcinoma patients with 22.8 ng/ml. For active TGF-beta1 these findings are exactly recovered. For serum levels, only the renal carcinoma group presents with significantly elevated levels of TGF-beta1. Kidney transplantation seems to normalize TGF-beta1 levels, while in the kidney cancer patients surgery has an effect only in part of the group. We conclude that elevated plasma TGF-beta1 levels are common in at least two chronic renal disease conditions, and that it normalizes with restoration of renal function. It is tempting to speculate that chronic elevation of TGF-beta1 in these patients may be critically involved in these conditions predisposing to renal cancer.

Carcinoma, Renal Cell↗
PubMed2000

[Treatment of acute clinical stroke].

Stroke is an emergency. Treatment must begin as soon as possible because significant sustained neurological improvement has been demonstrated when thrombolytic treatment, mainly with recombined tissue plasminogen activator (rtPA) is initiated within the first hours of stroke onset. On the other hand in the acute phase of stroke it is critical that patients get adequate management for the prevention of early complications. Management of the acute phase of stroke is the target of this article. Preclinically started treatment must be continued in the neurological emergency unit. Clinical examination is followed by technical investigations: cerebral computer tomography (CCT) is the most useful radiological investigation in the acute phase. It allows to distinguish between ischemia and hemorrhagic lesions and also to rule out nonstroke brain conditions. Multimodal magnetic resonance imaging (mMRI) may provide data on viable versus irreversibly damaged tissue. Sufficient stroke treatment is based on well managed in-hospital infrastructure. Thrombolysis is the only causative treatment of stroke in selected patients. Complications of acute stroke comprise changes of blood pressure with hemodynamically relevant effects on cerebral perfusion pressure, acute post- ischemic brain edema, and intracerebral bleedings.

Brain↗
PubMed2000

Diffusion of water molecules in crystalline beta-cyclodextrin hydrates.

To understand the rapid diffusion mechanism of water molecules in the crystal lattice of hydrated beta-cyclodextrin (beta-CD), molecular dynamics (MD) simulations of crystalline beta-CD were performed at five different relative humidities corresponding to hydration states ranging from beta-CD-9.4H2O to beta-CD-12.3H2O, and in aqueous solution. The trajectories for the crystalline beta-CD hydrates had lengths of 4 ns each, whereas the simulation in aqueous solution extended to 2 ns. Transport of water molecules in the crystal was characterized in terms of a spatially varying diffusion constant and the main direction of diffusion, which were evaluated using newly developed algorithms. The main diffusion pathway winds through the cavities of adjacent doughnut shaped beta-CD molecules and is slightly slanted with respect to the crystallographic b-axis. Water molecules outside the beta-CD cavities have access to the main diffusion pathway. The diffusion constant for transport of water molecules along the main pathway calculated from the MD simulation data adopts 1/30 of the value in bulk water at room temperature. This is in agreement with estimates that can be made from experimental data on the adjustment of a beta-CD crystal to changes in relative humidity.

Algorithms↗
PubMed2000

Triphenylmethanol-triphenylphosphine oxide (1/1)

In the crystalline 1:1 molecular complex of triphenylmethanol (TPMeOH) and triphenylphosphine oxide (TPPO), C(19)H(16)O. C(18)H(15)OP, molecular dimers are formed which are linked by O-H. O=P hydrogen bonds. The dimers are aligned by sixfold phenyl embraces to form columns. The structure is disordered with half a dimer per asymmetric crystal unit, i.e. with only one molecular site which is half-occupied by both TPMeOH and TPPO.

Journal Article↗
PubMed2000

Hydrogen bonding in two salts of 3-methylthio-4-(propargylthio)quinoline

In 3-methylthio-4-(propargylthio)quinolinium chloride monohydrate, C(13)H(12)NS(2)(+).Cl(-).H(2)O, and 3-methylthio-4-(propargylthio)quinolinium trichloroacetate, C(13)H(12)NS(2)(+).C(2)Cl(3)O(2)(-), the terminal alkyne group forms C[triple-bond]C-H.O hydrogen bonds of favourable geometry. The conformation of the flexible propargylthio group is different in the two structures.

Journal Article↗
PubMed2000

Bis(4-propargyloxy-3-quinolylthio)methane.

The molecular structure of the title compound, C(25)H(18)N(2)O(2)S(2), in the crystal is characterized by almost parallel quinoline and propargyl groups that point in opposite directions out of the quinoline planes. Intermolecular C[triple-bond]C-H...N hydrogen bonding is observed, but the hydrogen-bond geometry is poor.

Analgesics↗
PubMed2000

C

Explore the source record for details and available documents.

Journal Article↗
PubMed2000

Frequency of Z' values in organic and organometallic crystal structures.

The frequencies of Z' values (formula units per asymmetric crystal unit) are documented for organic and organometallic crystal structures, using the Cambridge Structural Database. The absolute frequencies of all Z' values reported, relative frequencies for certain substance classes, the seven crystal systems and the most abundant space groups are given. The three Z' values 1/2, 1 and 2 make up 95.3% of all crystal structures. Structures with Z' > 1 occur most frequently with nucleosides and nucleotides (20.8%), and with steroids (18.8%).

Journal Article↗
PubMed2000

Short N+--H...Ph hydrogen bonds in ammonium tetraphenylborate characterized by neutron diffraction

The crystal structures of ammonium tetraphenylborate, NH4+.BPh4-, are determined by neutron diffraction at 20 and 293 K. At both temperatures, all four N-H vectors of the ammonium ion are time-average-oriented at the midpoints of the phenyl rings of neighboring anions. The N-H...Ph distances, H...M 2.067 and N...M 3.023 A, are exceptionally short (M = aromatic midpoint). Even at 20 K the ammonium ion performs large amplitude motions which allow the N-H vectors to sample the entire face of the aromatic system.

Journal Article↗
PubMed2000

Monitoring intravenous recombinant tissue plasminogen activator thrombolysis for acute ischemic stroke with diffusion and perfusion MRI.

BACKGROUND AND PURPOSE: Intravenous recombinant tissue plasminogen activator (rtPA) administration is an effective therapy for ischemic stroke when initiated within 3 hours and possibly up to 6 hours after symptom onset. To improve patient selection, a fast diagnostic tool that allows reliable diagnosis of hemorrhage and ischemia, vessel status, and tissue at risk at an early stage may be useful. We studied the feasibility of stroke MRI for the initial evaluation and follow-up monitoring of patients undergoing intravenous thrombolysis. METHODS: Stroke MRI (diffusion- and perfusion-weighted imaging [DWI and PWI, respectively], magnetic resonance angiography, and T2-weighted imaging) was performed before, during, or after thrombolysis and on days 2 and 5. We assessed clinical scores (National Institutes of Health Stroke Scale [NIHSS], Scandinavian Stroke Scale [SSS], Barthel Index, and Rankin scale) at days 1, 2, 5, 30, and 90. Furthermore, we performed volumetric analysis of infarct volumes on days 1, 2, and 5 as shown in PWI, DWI, and T2-weighted imaging. RESULTS: Twenty-four patients received rtPA within a mean time interval after symptom onset of 3.27 hours and stroke MRI of 3.43 hours. Vessel occlusion was present in 20 of 24 patients; 11 vessels recanalized (group 1), and 9 did not (group 2). The baseline PWI lesion volume was significantly larger (P=0.008) than outcome lesion size in group 1, whereas baseline DWI lesion volume was significantly smaller (P=0.008) than final infarct size in group 2. Intergroup outcome differed significantly for all scores at days 30 and 90 (all P<0.01). Intragroup differences were significant in group 1 for change in SSS and NIHSS between day 1 and day 30 (P=0.003) and for SSS only between day 1 and day 90 (P=0.004). CONCLUSIONS: Stroke MRI provides comprehensive prognostically relevant information regarding the brain in hyperacute stroke. Stroke MRI may be used as a single imaging tool in acute stroke to identify and monitor candidates for thrombolysis. It is proposed that stroke MRI is safe, reliable, and cost effective; however, our data do not prove this assumption. Early recanalization achieved by thrombolysis can save tissue at risk if present and may result in significantly smaller infarcts and a significantly better outcome.

Acute Disease↗
PubMed2000

Feasibility and practicality of MR imaging of stroke in the management of hyperacute cerebral ischemia.

BACKGROUND AND PURPOSE: Neuroimaging techniques such as diffusion- and perfusion-weighted MR imaging have been proposed as tools for advanced diagnosis in hyperacute ischemic stroke. There is, however, substantial doubt regarding the feasibility and practicality of applying MR imaging for the diagnosis of stroke on a routine basis, especially with respect to possible delay for specific treatment such as thrombolysis. In this study, we tested whether MR imaging of stroke is safe, fast, and accurate, and whether the gain in additional information can be used in the daily routine without a loss of time and a risk of suboptimal treatment for the patient with stroke. METHODS: Between September 1997 and August 1999, 64 patients with acute ischemic stroke were recruited for MR imaging (ie, diffusion-weighted imaging, perfusion-weighted imaging, MR angiography, T2-weighted imaging) after a baseline CT was performed. We evaluated practicality and feasibility of MR imaging of stroke by analyzing the intervals between symptom onset, arrival, CT, and MR imaging. RESULTS: Sixty-four patients (mean age, 60.9 years) underwent routine CT and MR imaging within 12 hours after stroke onset (n=25, < or =3 hr; n=26, 3-6 hr; n=13, 6-12 hr). Median times to arrival, start of CT, MR imaging, and between CT and MR imaging were 1.625 hours, 2 hours, 3.875 hours, and 1 hour, respectively. Intervals between symptom onset and MR imaging (P<.005), arrival and MR imaging (P<.002), and CT and MR imaging (P=.0007) differed significantly between the early phase of the study and after November 1998, whereas the intervals between symptom onset and arrival, symptom onset and CT, and arrival and CT did not. Hemorrhage could be excluded in all; a perfusion/diffusion match or mismatch could be shown in 63 of 64 patients. CONCLUSION: Practice and experience with MR imaging in a stroke team significantly reduce the time and effort required to perform this technique and thus make 24-hour availability for MR imaging of stroke practical. Assessment of patients with hyperacute stroke is rapid and comprehensive. Image quality can be substantially improved by head immobilization and by mild sedation, if necessary.

Adult↗
PubMed2000

Health care, information needs, and outreach: reaching Ohio's rural citizens.

As a rural state, Ohio has a vital interest in addressing rural health and information needs. NetWellness is a Web-based consumer health information service that focuses on the needs of the residents of Ohio. Health sciences faculty from the state's three Carnegie Research I universities--University of Cincinnati, Case Western Reserve University, and The Ohio State University--create and evaluate content and provide Ask an Expert service to all visitors. Through partnerships at the state and local levels, involving public, private, commercial, and noncommercial organizations, NetWellness has grown from a regional demonstration project in 1995 to a key statewide service. Collaboration with public libraries, complemented by alliances with kindergarten through twelfth grade agencies, makes NetWellness Ohio's essential health information resource.

Health Education↗