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Biomedical subjects

K Ludwig

Publications and source records attributed to K Ludwig.

At least 73 records · Page 4Linked to original sources
PubMed2000

[Cystic gastric stromal tumors: a diagnostic dilemma?].

Gastric cysts are a rare disease and their diagnostic work-up often produces inconclusive results. We report on four gastric stromal tumors, in part huge, with cystic degeneration where the diagnosis and organ of origin remained unclear until operation. Considering these tumors as examples we discuss means and limits of differential diagnosis, taking into account further diseases with cystic formations in the gastric wall, such as other soft tissue tumors, pancreatic pseudocysts and gastric duplication cysts. In conclusion, every cystic tumor in the upper abdomen for which a diagnosis and origin cannot be established should be explored by surgery.

Adult↗
PubMed2000

Digital selenium radiography: detection of subtle pulmonary lesions on images acquired with and without an additional antiscatter grid.

OBJECTIVE: the objective of this ROC-study was to evaluate the diagnostic efficacy of images acquired with a grid in digital selenium radiography compared to that on images obtained with the integrated air gap only. MATERIALS AND METHODS: seven types of simulated lesions were superimposed onto an anthropomorphic chest phantom. Selenium radiography images were obtained either with or without an additional antiscatter grid. For images acquired with a grid either a similar or increased exposure level was used. Both normal and obese patients were simulated. RESULTS: When a grid was used with an equivalent detector dose and a higher exposure, diagnostic performance was significantly improved as compared to images obtained with only the air gap. ROC curve areas for mediastinal nodules and catheters were substantially higher for images acquired with a grid and the same exposure level compared to images obtained without a grid. However, detection of linear, net-shaped and reticulonodular structures in peripheral lung regions was significantly worse when a grid was used with an equivalent exposure level. Concerning the interpretation of images obtained from the normal and obese phantom models, no substantial differences were observed. CONCLUSION: a marked improvement in diagnostic performance could be achieved by means of the use of an additional antiscatter grid and an equivalent detector dose. However, when the same exposure was used, images acquired with the grid allowed a better detection of mediastinal structures although a worse performance was evident in radiolucent lung regions. Therefore, the routine use of a grid without increased exposure is not recommended.

Humans↗
PubMed2000

The role of the transmembrane and of the intraviral domain of glycoproteins in membrane fusion of enveloped viruses.

Fusion of enveloped viruses with their target membrane is mediated by viral integral glycoproteins. A conformational change of their ectodomain triggers membrane fusion. Several studies suggest that an extended, triple-stranded rod-shaped alpha-helical coiled coil resembles a common structural and functional motif of the ectodomain of fusion proteins. From that, it is believed that essential features of the fusion process are conserved among the various enveloped viruses. However, this has not been established so far for the highly conserved transmembrane and intraviral sequences of fusion proteins. The article will focus on the role of both sequences in the fusion process. Recent studies from various enveloped viruses strongly imply that a transmembrane domain with a minimum length is required for later steps of membrane fusion, i.e., the formation and enlargement of the aqueous fusion pore. Although no specific sequence of the TM is necessary for pore formation, distinct properties and motifs of the domain may be obligatory to ascertain full fusion activity. However, with some exceptions, the intraviral domain seems to be not required for fusion activity of viral fusion proteins.

Amino Acid Sequence↗
PubMed2000

Sterilization of elastic ligatures for intraoperative mandibulomaxillary immobilization.

Sterilization can influence the mechanical properties of elastic ligatures used for mandibulomaxillary immobilization. The aim of this study was to compare different sterilization protocols (ethylene oxide, autoclave, irradiation, plasma sterilization, povidone-iodine for 24 hours and 70% isopropyl alcohol for 24 hours) of three elastomers (natural rubber, silicone rubber, and polyurethane). Three mechanical variables were assessed in a testing machine: breaking strength, tensile strength and tensile strength after a 24-hour load (material fatigue). Natural rubber was most susceptible to mechanical alteration by sterilization and lost 46% of its breaking strength and 43% of its tensile strength after autoclaving. Polyurethane was more resistant (multiple comparison, Tukey-Kramer), but polyurethane ligatures stuck together after autoclaving. The protocols for low-temperature sterilization, ethylene oxide, irradiation, and plasma were superior to autoclaving and the disinfecting solutions. These data suggest that polyurethane sterilized with ethylene oxide is the material of choice.

2-Propanol↗
PubMed2000

Efficacy of botulinum toxin A for treatment of upper esophageal sphincter dysfunction.

OBJECTIVES: To investigate the efficacy of botulinum toxin A (BTA)-induced chemodenervation of the upper esophageal sphincter (UES) in patients with dysphagia and UES dysfunction. STUDY DESIGN: Prospective clinical trial in 10 selected patients with pure UES dysfunction. METHODS: In each patient 30 units of BTA were injected into the UES under brief general anesthesia. Videofluoroscopic swallowing study (VSS) was done and a clinical symptom score was determined before and after treatment. RESULTS: On VSS relative opening of the UES improved in all patients (mean +/- SD: 47 +/- 14% before versus 71 +/- 24% after treatment; P < .01). Hypopharyngeal retention or laryngeal penetration of barium was significantly reduced in four of seven patients. Clinical symptom scores improved in all patients. One patient was free of symptoms, mild dysphagia persisted in six patients, and moderate dysphagia persisted in three patients. CONCLUSIONS: Our results support the use of BTA in selected patients with pure UES dysfunction. Its efficacy is limited by the possibility of a persistent structural stenosis of the UES and the risk of BTA diffusion into the larynx or hypopharynx.

Adult↗
PubMed2000

Central corneal thickness determined with optical coherence tomography in various types of glaucoma.

AIMS: To evaluate central corneal thickness determined by optical coherence tomography (OCT) in various types of glaucoma, and its influence on intraocular pressure (IOP) measurement. METHODS: Central corneal thickness (CCT) was determined by using OCT in 167 subjects (167 eyes). 20 had primary open angle glaucoma (POAG), 42 had low tension glaucoma (LTG), 22 had ocular hypertension (OHT), 10 had primary angle closure glaucoma (AC), 24 had pseudoexfoliation glaucoma (PEX), 13 had pigmentary glaucoma (PIG), and 36 were normal. RESULTS: CCT was significantly higher in ocular hypertensive subjects (593 (SD 35) microm, p <0.0001) than in the controls (530 (32) microm), whereas patients with LTG (482 (28) microm, p < 0. 0001), PEX (493 (33) microm, p <0.0001), and POAG (512 (30) microm, p <0.05) showed significantly lower readings. There was no statistically significant difference between the controls and patients with PIG (510 (39) microm) and AC (539 (37) microm). CONCLUSIONS: Because of thinner CCT in patients with LTG, PEX, and POAG this may result in underestimation of IOP, whereas thicker corneas may lead to an overestimation of IOP in subjects with OH. By determining CCT with OCT, a new and precise technique to measure CCT, this study emphasises the need for a combined measurement of IOP and CCT in order to obtain exact IOP readings.

Aged↗
PubMed2000

Selenium-based digital radiography in the detection of bone lesions: preliminary experience with experimentally created defects.

PURPOSE: To compare the diagnostic performance of selenium-based digital radiography with that of conventional screen-film radiography and storage phosphor radiography for the detection of bone lesions simulating osteolyses. MATERIALS AND METHODS: Artificial osseous lesions 1.0-3.0 mm in diameter were created in 80 of 160 predefined regions in 16 porcine femoral specimens. Specimens were enclosed in containers filled with paraffin to ensure accurate repositioning and to obtain an absorption condition comparable to that of a human extremity. Imaging was performed with a selenium-based digital radiography system, a conventional screen-film system, and a storage phosphor radiography system with an exposure identical to that used during clinical imaging. The presence of a lesion was assessed with a five-point confidence scale. Receiver operating characteristic (ROC) analysis was performed for a total of 1,440 observations (480 per modality), and diagnostic performance was estimated with the area under the ROC curve (A(z)). Differences in diagnostic performance were assessed with the paired Student t test. RESULTS: ROC analysis results showed A(z) values of 0.656 for selenium-based digital radiography, 0.679 for storage phosphor radiography, and 0.680 for conventional screen-film radiography. Differences between the three modalities were not significant (P =.60-.93). CONCLUSION: Image quality with selenium-based digital radiography was comparable to that with conventional screen-film radiography and storage phosphor radiography.

Animals↗
PubMed2000

[Experiences with reconstruction of large abdominal wall cicatricial hernias using Stoppa-Rives pre-peritoneal mesh-plasty].

BACKGROUND: The observed recurrence-rate up to 20-50% of conventional incisional-hernia repair might be improved by alloplastic hernia repair in "sublay-technique" described by Stoppa and Rives. METHODS: From 12/94 to 12/97 122 pt. underwent surgery of incisional hernia of whom 50 had a very large abdominal wall defect so that hernia repair by alloplastic technique was necessary. All 50 pt. had mesh-implantation in subfascial plane, 28 pt. by ePTFE-patch (Gore-Tex) and 22 pt. by polypropylen-mesh (Prolene). RESULTS: The implantation-procedure required a mean time of 165 min. (range 55-345 min.). There were pulmonary complications in 2 patients (4%) of whom one had to be ventilated over 34 days, prosthesis-infection occurred in 3 pt. (6%). Follow-up on average 19 months (range 5-44 months) postoperatively revealed 5 hernia-recurrences (10.4%) in 48 patients. CONCLUSION: Mesh-implantation for hernia repair in sublay-technique requires intensive preparation of preperitoneal plane. Thus it took approximately 3 hours for mesh-implantation in this study. From our data Stoppa-Rives-procedure seems to be effective for 4-repair of large incisional hernias and allows immediate abdominal wall stress.

Adult↗
PubMed2000

Bilateral anterior lenticonus: Scheimpflug imaging system documentation and ultrastructural confirmation of Alport syndrome in the lens capsule.

BACKGROUND: Alport syndrome is a combination of proteinuria, hematuria, and neurosensory high-frequency deafness. Bilateral anterior lenticonus may be a late sign. Diagnosis relies on characteristic electron microscopy changes of glomerular basement membranes in renal biopsy specimens. PATIENT: A 38-year-old man was seen for progressive visual acuity loss (20/400 OU; best-corrected visual acuity, 20/60 OD and 20/50 OS). Findings from slitlamp examination included bilateral anterior lenticonus and central posterior subcapsular cataract, documented using a modified Scheimpflug imaging system. Retinal pathology was not present. On detailed questioning, a history of microhematuria and proteinuria since childhood and progressive high-frequency deafness for years were discovered. The family history was negative for nephropathies, deafness, or eye diseases. Cataract extraction rehabilitated the patient's vision. RESULTS: Electron microscopy of a fragile capsulorhexis specimen showed typical thinned basal lamina with basement membrane disruptions. CONCLUSIONS: Anterior lenticonus is a rare bilateral progressive developmental anomaly. More than 90% of cases are associated with Alport syndrome. For diagnosis of Alport syndrome, the presence of 3 of 4 criteria is required: family history positive for Alport syndrome, progressive intra-auricular deafness, characteristic eye anomalies, and positive findings from glomerular ultrastructural examination. We believe that ultrastructural proof of anterior lenticonus may also be provided in the lens capsule. Arch Ophthalmol. 2000;118:895-897

Adult↗
PubMed1999

Structure of influenza haemagglutinin at neutral and at fusogenic pH by electron cryo-microscopy.

The three-dimensional structures of the complete haemagglutinin (HA) of influenza virus A/Japan/305/57 (H2N2) in its native (neutral pH) and membrane fusion-competent (low pH) form by electron cryo-microscopy at a resolution of 10 A and 14 A, respectively, have been determined. In the fusion-competent form the subunits remain closely associated preserving typical overall features of the trimeric ectodomain at neutral pH. Rearrangements of the tertiary structure in the distal and the stem parts are associated with the formation of a central cavity through the entire ectodomain. We suggest that the cavity is essential for relocation of the so-called fusion sequence of HA towards the target membrane.

Cryoelectron Microscopy↗
PubMed1999

[Delayed toxicity of brief preoperative irradiation and risk-adjusted postoperative radiotherapy of operative rectal carcinoma. Results of a randomized prospective study].

AIM: Analysis of a randomized study of preoperative radiation therapy for operable carcinoma of the rectum with regard to late sequelae. Results of tumor control and survival, which have already been published in detail are summarized for comparison and for confirmation of the conclusions. PATIENTS AND METHODS: Between January 1988 and October 1993 94 patients with operable carcinoma of the rectum were included in a randomized trial. Fourty-seven patients were treated with 5 x 3.3 Gy (field size 16 x 16 cm, 9 MeV photons) 24 to 48 hours prior to surgery; 46 patients did not receive preoperative irradiation. If risk factors (T4-stage, R1/R2 resection, intraoperative tumor perforation) were present, postoperative irradiation was performed after CT-planning. Total postoperative doses of 41.4 Gy (preoperative irradiation) or 59.8 Gy (surgery only) were applied with doses per fraction of 1.8 to 2.0 Gy. Local control, survival, and pattern of side effects were analyzed at 5 years after conclusion of the trial. RESULTS: The frequency of local recurrence was markedly reduced by preoperative irradiation of R0-resected patients (24% vs 13%, p = 0.08). The time to recurrence was delayed (1.9 vs 3 years). The 5-year actuarial survival rate was significantly higher in the preoperatively irradiated group compared to the not pre-irradiated group (40% vs 28%, p = 0.027). Multivariate analysis revealed UICC-grading as the only independent parameter for local control (p = 0.0003), while preoperative irradiation (p = 0.07) and T-stage (p = 0.08) only displayed a trend. For patient survival, age (p = 0.0003). R-status (p = 0.01) and UICC-score (p = 0.001) were significant prognostic factors. Preoperative irradiation had a non-significant effect only (p = 0.078). Radiation-induced side effects with a LENT-SOMA score > 2 were observed neither during frequent follow-up nor at an additional examination of those patients still alive in 1998 (n = 25). Of 4 pre- and postoperatively irradiated patients with risk factors, 3 had side effects grade 1 or 2, predominantly rectal changes, at 5 to 11 years after treatment. CONCLUSIONS: A positive effect on tumor control and survival is achieved with preoperative irradiation with the doses used in this study, with moderate side effects.

Actuarial Analysis↗
PubMed1999

[Intra- and peri-renal gas formation. Bilateral emphysematous pyelonephritis].

Bilateral emphysematous pyelonephritis is an extremely rare, rapidly progressive and life-threatening intrarenal and perirenal infection. It is associated with diabetes mellitus, obstruction of the upper urinary tract and the presence of gas-forming coliform bacteria. As it presents as a severe acute pyelonephritis, a high index of suspicion and computer-tomographic imaging are essential to make the diagnosis. Only immediate combined medical and (bilateral) surgical therapy can reduce the high patient mortality. Postoperatively, computer-tomographic monitoring is recommended to follow the response to therapy.

Aged↗
PubMed1999

In vivo imaging of the human zonular apparatus with high-resolution ultrasound biomicroscopy.

BACKGROUND: To investigate the potential of high-resolution ultrasound biomicroscopy (UBM) for studying the zonular apparatus of human beings in vivo. METHODS: Using transducer frequencies of 34 MHz and 50 MHz, criteria were developed to identify transcorneal and transscleral sections that allowed reproducible identification of the different fiber groups of the zonular architecture. For that purpose, 10 volunteers between the ages of 14 and 41 years underwent high-resolution ultrasound biomicroscopy under conditions of consensual far- and near-accommodation. The online video recordings of the respective UBM investigations were afterwards analyzed image by image. Good visibility of zonular fibers was obtained when the ultrasound wave propagation comprised an angle close to 90 degrees with the fiber orientation and when the oscillations of the UBM scan had a strict radial orientation towards the limbus and avoided, simultaneously, the ciliary processes. RESULTS: In all the volunteers, high-resolution ultrasound biomicroscopy imaged the zonular fiber groups known from histology. In addition, it detected fibers that do not follow the course of the inner ciliary body surface but take a direct route from the ora serrata to the lens. It also demonstrated that fibers that seem to change direction at crossings with other fibers. Under conditions of near-accommodation, the zonular fibers showed signs of relaxation. CONCLUSIONS: High-resolution ultrasound biomicroscopy seems well suited for in vivo investigations of the zonular apparatus and of accommodation in man. The results support the fundamental features of the Helmholtz theory on accommodation.

Accommodation, Ocular↗