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Biomedical subjects

J Haase

Publications and source records attributed to J Haase.

At least 37 records · Page 2Linked to original sources
PubMed1999

Control of FES thumb force using slip information obtained from the cutaneous electroneurogram in quadriplegic man.

A tetraplegic volunteer was implanted with percutaneous intramuscular electrodes in hand and forearm muscles. Furthermore, a sensory nerve cuff electrode was implanted on the volar digital nerve to the radial side of the index finger branching off the median nerve. In laboratory experiments a stimulation system was used to produce a lateral grasp (key grip) while the neural activity was recorded with the cuff electrode. The nerve signal contained information that could be used to detect the occurrence of slips and further to increase stimulation intensity to the thumb flexor/adductor muscles to stop the slip. Thereby the system provided a grasp that could catch an object if it started to slip due to, e.g., decreasing muscle force or changes in load forces tangential to the surface of the object. This method enabled an automatic adjustment of the stimulation intensity to the lowest possible level without loosing the grip and without any prior knowledge about the strength of the muscles and the weight and surface texture of the object.

Adult↗
PubMed1998

[An unusual case of intracranial lipomatosis and cerebral aneurysm].

An unusual combination of a fusiform aneurysm on the middle cerebral artery branch to the central region and cortical lipomatosis is described. The etiology of lipomatous disorders in the brain are multiple. The possibility of a combined dysplasia based on maldifferentiation of primitive meninges and the arterial wall is suggested in this case. Treatment consisted in uneventful, microsurgical image-guided resection of the aneurysm using the Surgiscope robotic system.

Adult↗
PubMed1998

[New techniques in neurosurgery].

Society demands for exactness and low complication rates of surgical treatment are high. Surgical training in the apprentice manner has been significantly reduced in Denmark since 1981 and e.g. the ability to visualize in three dimensions among younger neurosurgeons has diminished. Computer technology now makes it possible to create 3-D images that with incorporation of functionality leads to a faster and better understanding of neuroanatomy. In addition--for the sake of precision--true robotic instrumentation and navigational instruments have been introduced. The technological investments are compensated by reduced costs due to operative complications. A prerequisite for these developments are a close collaboration between medical doctors and engineers, keeping the respect for humanity intact. A survey of developmental areas in the neurosurgical techniques of today is given.

Brain Mapping↗
PubMed1998

Double resonance probes for close frequencies.

A new double resonance probe design for NMR experiments for systems with close resonance frequencies is introduced. The design is based on two coupled resonators and was extensively tested on magnetically aligned powders of several high temperature superconductors by performing double resonance experiments between the 65Cu and 63Cu isotopes as well as between transitions of different magnetic quantum number of the same spin. The probe's performance approaches that of a single resonance circuit and it has only 4 variable tuning/matching elements.

Magnetic Resonance Spectroscopy↗
PubMed1998

Epidemiology and prognosis in children treated for intracranial tumours in Denmark 1960-1984.

A total of 911 Danish children under 15 years of age were treated for an intracranial tumour in the 25-five year period 1960-1984. All cases were followed up to the end of 1994 or to emigration or death if one of these came sooner. The mean annual incidence was 32.5 per million children with a slight increase over the 25 years. The male/female ratio was 1.15 and close to the M/F ratio for the entire Danish population of children. Of the tumours, 46% were located in the supratentorial and 54% in the infratentorial compartment, and 94% were verified histologically. In order of frequency the most common types were astrocytomas (all grades, 35%), medulloblastomas (20%), ependymomas (14%), and craniopharyngiomas (5%). Total removal of the tumour was performed in 277 and partial removal, including biopsy, in 490 children. In 57 patients a shunt operation only was performed, and 87 children did not have an operation or died before the correct diagnosis was established. Radiotherapy was administered in 55%. The outcome depended on extent of removal, radiation, location and histology of the tumour. Most (784 or 86%) of the children survived more than 1 month after diagnosis or operation, and 353 children (39% of the whole series, 47% of those alive more than 1 month after diagnosis) were alive at follow-up. Of the survivors 29% had a tumour in the supratentorial midline, 26% one in the lateral part of the supratentorial area, 31% a cerebellar tumour and 13% a IV ventricle tumour. It was possible for 66% of the survivors with supratentorial and 90% of those with infratentorial tumours to lead a normal life. The long-term prognosis was especially good for children with cerebellar and supratentorial astrocytomas and optic chiasma tumours. Children with juvenile cerebellar astrocytoma had the best prognosis: 90% were alive at the end of the follow-up period, as against 20% of those with medulloblastoma and 6% of those with glioblastoma. A comparison of the data from the present series and from a similar Danish series of intracranial tumours in 533 children seen in the years 1935-1959 shows no significant differences in location or histology, a slight increase in annual incidence, and improved survival rates during the 50 years in question.

Adolescent↗
PubMed1998

[Balloon angioplasty of stent restenosis: early and late results of first and second PTCA in focal and diffuse stenosis].

UNLABELLED: From January 1996 until February 1997 6,376 patients were treated by our group with PTCA and 3,859 (60.5%) received one or several stents. An angiographic followup was achieved in 63% of the patients with 1,267 experiencing restenosis (32.8%). Of those being treated with re-PTCA 302 were randomly selected for further analysis. In-stent-restenosis was treated with rotablator in 8 patients (2.7%), with eximer laser in 21 (7.0%) and with another stent in 48 patients (15.9%). 225 patients (74.4%) of this subselection were treated with balloon-angioplasty only. Mean patient age was 63 +/- 10.2 years, 401 stents had been implanted (42.5% Wiktor, 13.7% Jomed Sito, 12.3% ACS Multlink, 9.5% GR II, and some others), the number of stents per patient was 1.68, mean stent length 28.5 mm, mean stent diameter 3.01 +/- 0.3 mm, the time since implantation 142 +/- 76 days. The recurrence appeared as restenosis in 199 patients (88.4%) and as a chronic stent occlusion in 26 (11.6%). In-stent-restenosis was discovered in 94.7% within the stent and was of focal appearance (restenosic lesion of < or = 5 mm) in 28.5% and diffuse (> 5 mm) in 71.5%. Balloondilatation (balloon:artery = 1:1; maximal pressure 11.7 +/- 3.3 bar) was successfull in 98% of the stenotic lesions and in 18/26 of the chronically occluded stents (definition of success: residual stenosis < 50%, no major complications). The stenosis decreased from 82.2% to 20.5% (12.8% in focally stenosed vessels and 23.6% in diffuse restenosis). Complications were death in 0.9%, Q-MI in 0% CABG in 0.9%, Non-Q-MI in 2.4%, subacute stent thrombosis in 0.5% and groin bleeding in 1.8%. A clinical follow up after 151.7 +/- 87.7 days was achieved in 98.6% and an angiographic follow up in 69.1% of the patients: 1.9% had died (2/4 due to noncardiac disease), no MI, 6.2% CABG and 31% PTCA (TLR 37.2%). A second restenosis within the stents ocurred in 27.9% of those with focal disease and in 44.3% of those with diffuse in stent restenosis. CONCLUSIONS: Restenosis within stents may occurr in about 30% of unselected patients. In 2/3 these stenoses appear diffuse and in 10% they appear as chronic occlusions. Re-PTCA with balloons is rather simple with a high success rate (even in chronic stent occlusions) and a low complication rate. The incidence of a second restenosis is acceptably high in focal lesions but appears unacceptable in patients with diffuse in-stent-restenosis. Thus the indication for stenting should be restricted to patients with clear cut advantage over balloon-angioplasty alone, e.g. threatening closure, chronic occlusion, old savenous veingraft and proximal LAD stenosis.

Aged↗
PubMed1998

Neurosurgical tools and techniques--modern image-guided surgery.

Cushing and other great neurosurgeons made their mental preparations for surgical procedures through extensive, beautiful drawings. Three-dimensional visualization was in those days supported through interpretation of pneumoencephalograms with displacements of structures indicating where a space-occupying process might be located. Today this visualization necessary for each neurosurgeon is partly lost in the teaching process due to axial magnetic resonance imaging and computed tomography scans and of minimal invasive techniques. Microsurgical navigation on the brain surface is like sailing along a coastline. Navigating in the brain is like sailing in fog and tools for navigation must be developed accordingly. The robotic microscope Surgiscope enables the surgeon to have at the same time a microscope, a pointing devise and a bidirectional tool for automatic maneuverability in the brain. A neurosurgeon may be distracted and thereby perform less adequate. Computer technology and virtual reality models enhances possibilities for rehearsal of difficult operations and of controlling the surgical performance. Computer technology is thus a supporter of future neurosurgeons and a part of quality control. Future education must be linked to this fact.

Brain↗
PubMed1997

Randomized comparison of angioplasty of complex coronary lesions at a single center. Excimer Laser, Rotational Atherectomy, and Balloon Angioplasty Comparison (ERBAC) Study.

BACKGROUND: The purpose of this study was to test whether coronary revascularization with ablation of either excimer laser or rotational atherectomy can improve the initial angiographic and clinical outcomes compared with dilatation (balloon angioplasty) alone. METHODS AND RESULTS: At a single center, a total of 685 patients with symptomatic coronary disease warranting elective percutaneous revascularization for a complex lesion were randomly assigned to balloon angioplasty (n = 222), excimer laser angioplasty (n = 232), or rotational atherectomy (n = 231). The primary end point was procedural success (diameter stenosis < 50%, absence of death, Q-wave myocardial infarction, or coronary artery bypass surgery). The patients who underwent rotational atherectomy had a higher rate of procedural success than those who underwent excimer laser angioplasty or conventional balloon angioplasty (89% versus 77% and 80%, P = .0019), but no difference was observed in major in-hospital complications (3.2% versus 4.3% versus 3.1%, P = .71). At the 6-month follow-up, revascularization of the original target lesion was performed more frequently in the rotational atherectomy group (42.4%) and the excimer laser group (46.0%) than in the angioplasty group (31.9%, P = .013). CONCLUSIONS: Procedural success of rotational atherectomy is superior to laser angioplasty and balloon angioplasty; however, it does not result in better late outcomes. The role of plaque debulking before balloon dilatation in percutaneous coronary revascularization remains to be fully defined.

Adult↗
PubMed1997

Parent stress and coping in NICU and PICU.

The purpose of this study was to identify and compare parental perceptions of their stress and coping experiences with children in pediatric intensive care units (PICU) and the neonatal intensive care units (NICU). The sample consisted of 31 NICU and 20 PICU parents. Parents in both units experienced the most stress from alteration in their parenting role and in their infants' behavior and appearance. Parents of children in PICU found assistance with parenting role more helpful than parents of children in NICU. Parents with children in the PICU perceived problems-focused coping more helpful than parents with children in the NICU; parents of children in NICU found emotion-focused coping more helpful than parents of children in PICU. Parents in both units considered problem-focused coping more helpful than appraisal- or emotion-focused coping.

Adaptation, Psychological↗
PubMed1997

Restoration of lateral hand grasp using natural sensors.

A closed-loop control system for controlling the key grip of a C6 tetraplegic patient was developed. Natural sensors served as the source of the feedback signal. The neural signals from cutaneous receptors were picked up by an implanted cuff electrode placed around the radial branch of the median nerve innervating the lateral part of the index finger. Mechanical stress applied to the skin, like pressure and slips, resulted in an increase in amplitude of the recorded neural signal. The goal of the study was to determine whether the recorded neural signals were able to indicate the slip of an object during lateral grasp and whether the slip could be stopped by increasing the grasp force through functional electrical stimulation of the thumb adductor and flexor.

Action Potentials↗
PubMed1997

Assembly of a functional phage PRD1 receptor depends on 11 genes of the IncP plasmid mating pair formation complex.

PRD1, a lipid-containing double-stranded DNA bacteriophage, uses the mating pair formation (Mpf) complex encoded by conjugative IncP plasmids as a receptor. Functions responsible for conjugative transfer of IncP plasmids are encoded by two distinct regions, Tra1 and Tra2. Ten Tra2 region gene products (TrbB to TrbL) and one from the Tra1 region (TraF) form the Mpf complex. We carried out a mutational analysis of the PRD1 receptor complex proteins by isolating spontaneous PRD1-resistant mutants. The mutations were distributed among the trb genes in the Tra2 region and accumulated predominantly in three genes, trbC, trbE, and trbL. Three of 307 phage-resistant mutants were weakly transfer proficient. Mutations causing a phage adsorption-deficient, transfer-positive phenotype were analyzed by sequencing.

Bacteriophages↗
PubMed1997

A specific protease encoded by the conjugative DNA transfer systems of IncP and Ti plasmids is essential for pilus synthesis.

TraF, an essential component of the conjugative transfer apparatus of the broad-host-range plasmid RP4 (IncP), which is located at the periplasmic side of the cytoplasmic membrane, encodes a specific protease. The traF gene products of IncP and Ti plasmids show extensive similarities to prokaryotic and eukaryotic signal peptidases. Mutational analysis of RP4 TraF revealed that the mechanism of the proteolytic cleavage reaction resembles that of signal and LexA-like peptidases. Among the RP4 transfer functions, the product of the Tra2 gene, trbC, was identified as a target for the TraF protease activity. TrbC is homologous to VirB2 of Ti plasmids and thought to encode the RP4 prepilin. The maturation of TrbC involves three processing reactions: (i) the removal of the N-terminal signal peptide by Escherichia coli signal peptidase I (Lep), (ii) a proteolytic cleavage at the C terminus by an as yet unidentified host cell enzyme, and (iii) C-terminal processing by TraF. The third reaction of the maturation process is critical for conjugative transfer, pilus synthesis, and the propagation of the donor-specific bacteriophage PRD1. Thus, cleavage of TrbC by TraF appears to be one of the initial steps in a cascade of processes involved in export of the RP4 pilus subunit and pilus assembly mediated by the RP4 mating pair formation function.

Amino Acid Sequence↗
PubMed1996

Significance of automated stenosis detection during quantitative angiography. Insights gained from intracoronary ultrasound imaging.

BACKGROUND: Automated stenosis analysis is a common feature of commercially available quantitative coronary angiography (QCA) systems, allowing automatic detection of the boundaries of the stenosis, interpolation of the expected dimensions of the coronary vessel at the point of obstruction, and angiographically derived estimation of atheromatous plaque size. However, the ultimate meaning of this type of analysis in terms of the degree of underlying atherosclerotic disease remains unclear. We investigated the relationship between stenosis analysis performed with QCA and the underlying degree of atherosclerotic disease judged by intracoronary ultrasound (ICUS) imaging. METHODS AND RESULTS: In 40 coronary stenoses, automated identification of the sites of maximal luminal obstruction and the start of the stenosis was performed with QCA by use of curvature analysis of the obtained diameter function. Plaque size at these locations also was estimated with ICUS, with an additional ICUS measurement immediately proximal to the start of the stenosis. Crescentlike distribution of plaque, indicating an atheroma-free arc of the arterial wall, was recorded. At the site of the obstruction, total vessel area measured with ICUS was 16.65 +/- 4.04 mm2, whereas an equivalent measurement obtained from QCA-interpolated reference dimensions was 7.48 +/- 3.30 mm2 (P = .0001). Plaque area derived from QCA data was significantly less than that calculated from ICUS (6.32 +/- 3.21 and 13.29 +/- 4.22 mm2, respectively; mean difference, 6.92 +/- 4.43 mm2; P = .0001). At the start of the stenosis identified by automated analysis, ICUS plaque area was 9.38 +/- 3.17 mm2, and total vessel area was 18.77 +/- 5.19 mm2 (50 +/- 11% total vessel area stenosis). The arterial wall presented a disease-free segment in 28 proximal locations (70%) but in only 5 sites (12%) corresponding to the start of the stenosis and none at the obstruction (P = .0001). At the site of obstruction, all vessels showed a complete absence of a disease-free segment, and the atheroma presented a cufflike or all-around distribution with a variable degree of eccentricity. CONCLUSIONS: At the site of maximal obstruction, QCA underestimated plaque size as measured with ICUS. Atherosclerotic disease was consistently present at the start of the stenosis and was used as a reference site by automated stenosis analysis. At the start of the stenosis, ICUS demonstrated a mean 50 +/- 11% total vessel area stenosis, with a characteristic loss of disease-free arcs of arterial wall present in proximal locations. Thus, the site identified by automated stenosis analysis as the start of the stenosis does not represent a disease-free site but rather the place where compensatory vessel enlargement fails to preserve luminal dimensions, a phenomenon that seems related to the observed loss of a remnant arc of normal arterial wall.

Aged↗