Search PubMed⌕ Search

Biomedical subjects

J Harms

Publications and source records attributed to J Harms.

At least 37 records · Page 2Linked to original sources
PubMed2000

[The radiological diagnosis of an intraorbital bullet projectile].

Beside conventional X-ray examination, ultrasound and computer tomographic examination are accepted radiologic techniques to assess the extend of damage of intraorbital injuries. With the exception of a few reports in the literature there is agreement that intraorbital metallic foreign bodies and gun-shot bullets represent a contraindication for magnetic resonance (MR) imaging examination because of artificial imaging side effects and the potential of secondary dislocation of the metallic foreign body due to ferromagnetism. By means of the case reported here it is shown that this general opinion is not universally valid. Depending on the elemental metallic composition of foreign bodies and gun-shot bullets it is demonstrated that MR examination allows high-resolution illustration and in some cases is advantageous compared with other radiologic imaging techniques.

Adult↗
PubMed2000

Assessment of gunshot bullet injuries with the use of magnetic resonance imaging.

BACKGROUND: Magnetic resonance imaging (MRI) is rarely used for preoperative assessment of shotgun injuries because of concerns of displacing the possibly ferromagnetic foreign body within the surrounding tissue. METHODS: A total of 56 different projectiles underwent MRI testing for ferromagnetism and imaging quality in vitro and in pig carcasses with a commercially available 1.5-MRI scan. Image quality was compared with that of computed tomographic scans. RESULTS: Projectiles with ferromagnetic properties can be distinguished easily from nonferromagnetic ones by pretesting the motion of an identical projectile within the MRI coil. When ferromagnetic projectiles were excluded, MRI yielded the more precise images compared with other imaging techniques. Projectile localization and associated soft tissue injuries were visualized without artifacts in all cases. CONCLUSIONS: When ferromagnetic foreign bodies are excluded by pretesting their properties within the MRI with a comparative projectile, MRI portends an excellent imaging procedure for assessing the extent of injury and planning the removal by surgery.

Animals↗
PubMed2000

[Telemetric impedance analysis of the liver: evaluation of a noninvasive device for diagnosis of acute graft rejection after experimental liver transplantation].

Allograft rejection and its differentiation from other causes of organ dysfunction remains a diagnostic problem in liver transplant patients. Currently, acute rejection can be prevented only by a combination of diagnostic and therapeutic modalities. The diagnostic potential of a novel implantable telemetric rejection monitoring device has been assessed on the basis of the noninvasive impedance analysis in normal and liver transplanted pigs. The electric impedance data were correlated with biochemical and histological parameters. Acute rejection was correctly predicted in n = 4, and correctly excluded in n = 32, biopsy-related impedance recordings (p = 0.004). A correlation between impedance measurements and severity of histological findings r = 0.84; p = 0.0001) was confirmed. Only the biochemical parameters SGLDH and serum bilirubin revealed a comparable correlation. Impedance gradient analysis revealed evidence of a physiological relationship between liver function and the electrical properties of the organ. Telemetric impedance analysis would appear a promising means of assessing acute rejection noninvasively.

Animals↗
PubMed2000

Targeting exposed RNA regions in crystals of the small ribosomal subunits at medium resolution.

Within the framework of ribosomal crystallography, the small subunits are being analyzed, using crystals diffracting to 3 A resolution. The medium resolution electron density map of this subunit, obtained by multiple isomorphous replacement, show recognizable morphologies, strikingly similar to the functional active conformer of the small ribosomal subunit. It contains elongated dense features, traceable as RNA chains as well as globular regions into which the structures determined for isolated ribosomal proteins, or other known structural motifs were fitted. To facilitate unbiased map interpretation, metal clusters are being covalently attached either to the surface of the subunits or to DNA oligomers complementary to exposed ribosomal RNA. Two surface cysteines and the 3' end of the 16S ribosomal RNA have been localized. Targeting several additional RNA regions shed light on their relative exposure and confirmed previous studies concerning their functional relevance.

Crystallography, X-Ray↗
PubMed1999

The small ribosomal subunit from Thermus thermophilus at 4.5 A resolution: pattern fittings and the identification of a functional site.

The electron density map of the small ribosomal subunit from Thermus thermophilus, constructed at 4.5 A resolution, shows the recognizable morphology of this particle, as well as structural features that were interpreted as ribosomal RNA and proteins. Unbiased assignments, carried out by quantitative covalent binding of heavy atom compounds at predetermined sites, led to the localization of the surface of the ribosomal protein S13 at a position compatible with previous assignments, whereas the surface of S11 was localized at a distance of about twice its diameter from the site suggested for its center by neutron scattering. Proteins S5 and S7, whose structures have been determined crystallographically, were visually placed in the map with no alterations in their conformations. Regions suitable to host the fold of protein S15 were detected in several positions, all at a significant distance from the location of this protein in the neutron scattering map. Targeting the 16S RNA region, where mRNA docks to allow the formation of the initiation complex by a mercurated mRNA analog, led to the characterization of its vicinity.

Base Sequence↗
PubMed1999

Elucidating the medium-resolution structure of ribosomal particles: an interplay between electron cryo-microscopy and X-ray crystallograhy.

BACKGROUND: Ribosomes are the universal cellular organelles that accomplish the translation of the genetic code into proteins. Electron cryo-microscopy (cryo-EM) has yielded fairly detailed three-dimensional reconstructions of ribosomes. These were used to assist in the determination of higher resolution structures by X-ray crystallography. RESULTS: Molecular replacement studies using cryo-EM reconstructions provided feasible packing schemes for crystals of ribosomes and their two subunits from Thermus thermophilus, and of the large subunits from Haloarcula marismortui. For the large subunits, these studies also confirmed the major heavy-atom sites obtained by single isomorphous replacement combined with anomalous diffraction (SIRAS) and by multiple isomorphous replacement combined with anomalous diffraction (MIRAS) at approximately 10 A. Although adequate starting phases could not be obtained for the small subunits, the crystals of which diffract to 3.0 A, cryo-EM reconstructions were indispensable for analyzing their 7.2 A multiple isomorphous replacement (MIR) map. This work indicated that the conformation of the crystallized small subunits resembles that seen within the 70S ribosomes. Subsequently, crystals of particles trapped in their functionally active state were grown. CONCLUSIONS: Single-particle cryo-EM can contribute to the progress of crystallography of non-symmetrical, large and flexible macromolecular assemblies. Besides confirming heavy-atom sites, obtained from flat or overcrowded difference Patterson maps, the cryo-EM reconstructions assisted in elucidating packing arrangements. They also provided tools for the identification of the conformation within the crystals and for the estimation of the level of inherent non-isomorphism.

Crystallography, X-Ray↗
PubMed1999

Spontaneous lumbar curve coronal correction after selective anterior or posterior thoracic fusion in adolescent idiopathic scoliosis.

STUDY DESIGN: Retrospective review of anterior and posterior fusions for treatment of adolescent idiopathic thoracic scoliosis. OBJECTIVES: To evaluate both the instrumented thoracic and the spontaneous lumbar curve corrections after treatment of the primary thoracic scoliosis by either anterior or posterior fusion. SUMMARY OF BACKGROUND DATA: Recent reports of thoracic scoliosis fusions have concentrated on the thoracic correction obtained by posterior segmental instrumentation systems. Coronal decompensation occurring because of curve progression with imbalance of the unfused lumbar spine has also been investigated. No report comparing spontaneous lumbar curve response after selective anterior versus posterior thoracic scoliosis fusions are available. METHODS: One hundred twenty-three cases of primary thoracic-compensatory lumbar adolescent idiopathic scoliosis were treated by selective thoracic instrumentation and fusion with either an anterior (n = 70) or posterior (n = 53) single approach. Thoracic and lumbar Cobb measurements and lumbar apical translation parameters were assessed before surgery, 1 week after surgery, and 2 years after surgery on upright coronal radiographs. All patients had a minimum 2-year follow-up. RESULTS: At 2-year follow-up, the percentage of thoracic curve correction was superior for the anterior (58%) versus the posterior (38%) group (P < 0.05), whereas the spontaneous lumbar curve correction was also superior for the anterior (56%) group versus the posterior (37%) group for all curve types investigated (P < 0.05). Both treatment groups consistently improved lumbar apical positioning after the thoracic fusion procedure. CONCLUSIONS: Spontaneous lumbar curve correction occurs consistently after both selective anterior and posterior thoracic fusion implying intrinsic ability of the lumbar spine to follow thoracic spine correction. In the current study, using multisegmented hook-rod systems posteriorly with intentional limitation of posterior thoracic correction to avoid decompensation, instrumented thoracic and spontaneous lumbar curve correction was statistically better after anterior thoracic instrumentation and fusion, with the results most dramatic for lumbar curve Type C (true King II curves).

Adolescent↗
PubMed1999

Comparison of anterior and posterior instrumentation for correction of adolescent thoracic idiopathic scoliosis.

STUDY DESIGN: This was a prospective study of two cohort groups of patients (one group receiving anterior instrumentation and the other posterior instrumentation) receiving treatment for thoracic idiopathic scoliosis. OBJECTIVE: To present the 2-year postoperative results of a prospective multicenter study comparing the use of anterior instrumentation with that of posterior multisegmented hook instrumentation for the correction of adolescent thoracic idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: Despite reports of satisfactory results, problems have been reported with posterior systems, including worsening of the lumbar curve after surgery and failure to correct hypokyphosis. Theoretically, the advantages of anterior instrumentation include prevention of lumbar curve decompensation by shortening the convexity of the thoracic curve. In addition, by removing the disc, better correction of thoracic hypokyphosis could be obtained. METHODS: Seventy-eight patients who underwent an anterior spinal fusion using flexible threaded rods and nuts (Harms-MOSS instrumentation, De Puy-Motech-Acromed, Cleveland, OH) were analyzed and compared with 100 patients who underwent posterior spinal fusion with multisegmented hook systems. Parameters of comparison included coronal and sagittal correction, balance, distal lumbar fusion levels, and complication. All patients had idiopathic thoracic curves of King Types II to V. The average age at surgery was 14 years in each group, the average preoperative curve 57 degrees, and the minimum duration of follow-up for all patients 24 months. All data were collected prospectively and analyzed via Epl into statistical analysis (Centers of Disease Control, Atlanta, GA). RESULTS: Average coronal correction of the main thoracic curve was 58% in the anterior group and 59% in the posterior group (P = 0.92). Analysis of sagittal contour showed that the posterior systems failed to correct a preoperative hypokyphosis (sagittal T5 to T12 less than 20 degrees) in 60% of cases, whereas 81% were normal postoperatively in the anterior group. However, hyperkyphosis (sagittal T5 to T12 greater than 40 degrees) occurred after surgery in 40% of the anterior group when the preoperative kyphosis was greater than 20 degrees. Postoperative coronal balance was equal in both groups. An average of 2.5 (range, 0-6) distal fusion levels were saved using the anterior spinal instrumentation according to the criteria used for determining posterior fusion levels in this study. Selective fusion of the thoracic curve (distal fusion level T11, T12, L1) was performed in 76 of 78 patients (97%) in the anterior group as compared with only 18 of 100 (18%) in the posterior group. Surgically confirmed pseudarthrosis occurred in 4 of 78 patients (5%) in the anterior group and in 1 of 100 patients (1%) in the posterior group (P = 0.10). Loss of correction greater than 10 degrees occurred in 18 of 78 patients (23%) in the anterior group and in 12 of 100 patients (12%) in the posterior group (P = 0.01). Implant breakage occurred in 24 patients (31%) of the anterior group and in only 1 patient (1%) of the posterior group. CONCLUSIONS: 1) Coronal correction and balance were equal in both the anterior and posterior groups, even though the anterior group had the majority of curves (97%) fused short or to L1, whereas only 18% were fused short or to L1 in the posterior group. 2) In the anterior group there was a better correction of sagittal profile in those with a preoperative hypokyphosis less than 20 degrees. However, hyperkyphosis (with a mean of 54 degrees) occurred in 40% of those in the anterior group with a preoperative kyphosis of more than 20 degrees. 3) An average of 2.5 lumbar levels can be saved with anterior fusion and instrumentation according to the criteria used for choosing posterior fusion levels in this study. 4) Using the 3.2-mm flexible rod in this study, loss of correction, pseudarthrosis, and rod breakage were unacceptably highe

Adolescent↗
PubMed1999

Metal compounds as tools for the construction and the interpretation of medium-resolution maps of ribosomal particles.

Procedures were developed exploiting organometallic clusters and coordination compounds in combination with heavy metal salts for derivatization of ribosomal crystals. These enabled the construction of multiple isomorphous replacement (MIR) and multiple isomorphous replacement combined with anomalous scattering medium-resolution electron density maps for the ribosomal particles that yield the crystals diffracting to the highest resolution, 3 A, of the large subunit from Haloarcula marismortui and the small subunit from Thermus thermophilus. The first steps in the interpretation of the 7. 3-A MIR map of the small subunit were made with the aid of a tetrairidium cluster that was covalently attached to exposed sulfhydryls on the particle's surface prior to crystallization. The positions of these sulfhydryls were localized in difference Fourier maps that were constructed with the MIR phases.

Animals↗
PubMed1999

[Not Available].

Explore the source record for details and available documents.

Journal Article↗
PubMed1999

[Surgical aortic fenestration in acute thoracoabdominal aortic dissection with abdominal malperfusion and end organ ischemia].

Intestinal, renal, spinal or peripheral arterial ischemia or failure of branch artery recanalization following initial prosthetic repair of thoracoabdominal aortic dissection is still a problem, with high morbidity and mortality. Five consecutive patients with acute thoracoabdominal aortic dissection (two type A dissections, three type B dissections) suffering from concomitant intestinal, renal, spinal and acute peripheral arterial ischemia are reported. Considering the anatomical and pathophysiological basis of thoracoabdominal aortic dissection and concomitant organ ischemia, the aortic fenestration procedure as a primary or secondary operative approach succeeded in restoring blood flow in all cases without complications. Assessment of the long-term results after 3 years revealed that all patients are doing well without any residual complaints. We conclude that in the case of persistent or secondary onset of aortic branch artery ischemia following initial prosthetic repair of either type A or type B dissection, aortic fenestration can be recommended immediately as a staged operative approach. Primary abdominal aortic fenestration is justified in acute type B dissection when end-organ ischemia becomes the focus of clinical deterioration.

Acute Disease↗
PubMed1999

[Correction of posttraumatic deformities. Principles and methods].

The reason for inadequate results after the treatment of spinal lesions may be due to the misinterpretation of the type of lesion thus leading to incorrect therapy. Frequently the bio-functional construction principles of the spine are ignored and biomechanically based reconstruction of the spine is not done. Unsuitable approaches and fusion techniques may result in insufficient stabilisation with predictable failure. In both the first surgery and the salvage procedure, the principles of the load-sharing system as well as the posterior tension band principle must be respected. These principles and the surgery techniques are demonstrated in individual examples. Special attention is drawn to the impact of segmental deformities on the general statics of the spine. Frequently, residual deformities with the typical clinical picture lead to decompensation and the reduction of efficiency only after ten to fifteen years.

Adolescent↗
PubMed1999

The role of lumbar lordosis, vertebral end-plate inclination, disc height, and facet orientation in degenerative spondylolisthesis.

Degenerative spondylolisthesis (DS) is a common condition of the aging spine, but the underlying pathomechanisms remain controversial. Most previous studies focused on the role of facet-joint alignment and reported a pronounced sagittal orientation. This, however, may also be a secondary feature to the slippage. This study analyzed several radiologic findings in the lower lumbar spine in 23 patients with DS (group A) and 40 age- and sex-matched controls (group B). Facet-joint angulation, intervertebral disc height, lordosis of the lumbar spine (L1-S1), and inclination of the L4, L5, and S1 end plates were assessed from neutral standing lateral radiographs and computed tomography (CT) or magnetic resonance imaging (MRI) investigations. Two findings were found to be significantly different between the groups. Facet joints were aligned more sagittal in group A, and the inclination of the vertebral end plates was more horizontal in group B. There was no statistical difference in lumbar lordosis or L4-5 disc height between the two groups, with disc height being decreased in both groups. In group A, more gliding was associated with a further decrease in disc space, pronounced sagittal alignment of the L4-5 facet joints, and a decrease in lumbar lordosis. We concluded that further studies should focus on the analysis of spinal alignment and lower lumbar end-plate orientation to identify patients at risk for development of DS.

Aged↗
PubMed1999

Mechanisms of retrolisthesis in the lower lumbar spine. A radiographic study.

The study investigates lower lumbar segments with posterior vertebral shifts (retrolisthesis) with respect to the orientation of facet joints, disc height, lordosis of the lumbar spine, and orientation of vertebral endplates. Standing lumbar radiographs as well as CT and/or MRI investigations of 69 patients were analyzed. Data from patients with retrolisthesis (20 cases) were compared to data from patients with degenerative spondylolisthesis (DS, 23 cases), and from patients without signs of vertebral shifts (26 cases). The orientation of facet joints in segments with retrolisthesis was not different from segments without shifts, whereas the facet joints in patients with DS were oriented more sagittally. The overall lordosis of the lumbar spine and the endplate inclination were considerably reduced in patients with retrolisthesis, especially compared to those with DS. Disc height was comparable in retrolisthesis and DS, but was reduced compared to segments without shifts. The results support biomechanical considerations, that a retrolisthesis of a lower lumbar spine segment is correlated with a reduction of lumbar lordosis, endplate inclination, and segmental height.

Aged↗
PubMed1999

[Primary stability of 2 PLIF (posterior lumbar interbody fusion) techniques--a biomechanical and finite element analysis].

The purpose of this study was to compare the initial stiffness of two techniques for posterior interbody lumbar fusion by biomechanical and finite element analysis. Initial stiffness was tested under compression, torsion and shearing forces. The effect of an increasing initial stability by additional posterior instrumentation is proven by the biomechanical analysis and the finite element method.

Biomechanical Phenomena↗
PubMed1998

Crystallographic studies on the ribosome, a large macromolecular assembly exhibiting severe nonisomorphism, extreme beam sensitivity and no internal symmetry.

Crystals, diffracting best to around 3 A, have been grown from intact large and small ribosomal subunits. The bright synchrotron radiation necessary for the collection of the higher-resolution X-ray diffraction data introduces significant decay even at cryo temperatures. Nevertheless, owing to the reasonable isomorphism of the recently improved crystals of the small ribosomal subunits, reliable phases have been extracted at medium resolution (5-6 A) and an interpretable five-derivative MIR map has been constructed. For the crystals of the large subunits, however, the situation is more complicated because at higher resolution (2.7-7 A) they suffer from substantial radiation sensitivity, a low level of isomorphism, instability of the longest unit-cell axis and nonisotropic mosaicity. The 8 A MIR map, constructed to gain insight into this unusual system, may provide feasible reasoning for the odd combination of the properties of these crystals as well as hints for future improvement. Parallel efforts, in which electron-microscopy-reconstructed images are being exploited for molecular-replacement studies, are also discussed.

Animals↗
PubMed1998

Facet joint remodeling in degenerative spondylolisthesis: an investigation of joint orientation and tropism.

This study analyzed transverse facet joint angulations at the three lower lumbar levels in 132 patients assigned to one of four groups. Group A comprised 23 patients with degenerative spondylolisthesis (DS) at the level L4-5, group B comprised 40 patients above the age of 50 years, group C comprised 38 patients aged between 35 and 50 years, and group D comprised 31 patients under the age of 35 years. Groups B, C, and D had no evidence of DS. Measurements were taken from hard copies of axial MR or CT images. The transverse plane of facet joints was more sagittally oriented in group A than in any other group. This difference was highly significant at the L4-5 level. The incidence of more sagittally oriented L4-5 facet joints was also significantly higher only in group A. The incidence of facet joint tropism, however, was not different in group A. These results support the view that the pronounced sagittal alignment of facet joints in patients with DS represents a secondary remodeling rather than a pre-existing morphology. Facet joint asymmetry does not seem to play a major role in the development of DS.

Adult↗