Biomedical subjects

J Maurer

Publications and source records attributed to J Maurer.

At least 19 recordsLinked to original sources

PubMed2006

Normal embryonic development and cardiac morphogenesis in mice with Wnt1-Cre-mediated deletion of connexin43.

Mice harboring a null mutation in the gap junction protein connexin43 (Cx43) die shortly after birth due to an obstruction of the right ventricular outflow tract of the heart. These hearts exhibit prominent pouches at the base of the pulmonary outlet, i.e., morphological abnormalities that were ascribed to Cx43-deficiency in neural crest cells. In order to examine the Cx43 expression pattern in neural crest cells and derived tissues and to test whether neural crest-specific deletion of Cx43 leads to the conotruncal defects seen in Cx43null mice, we ablated Cx43 using a Wnt1-Cre transgene. Deletion of Cx43 was complete and occurred in neural crest cells as well as in neural crest-derived tissues. Nevertheless, hearts of mice lacking Cx43 specifically in neural crest cells were indistinguishable from controls. Thus, the morphological heart abnormalities of Cx43 null mice are most likely not caused by lack of Cx43 in neural crest cells.

Animals↗

PubMed2005

Side-branch growth in two-dimensional dendrites. I. Experiments.

The dynamics of growth of dendrites' side branches is investigated experimentally during the crystallization of solutions of ammonium bromide in a quasi-two-dimensional cell. Two regimes are observed. At small values of the Peclet number a self-affine fractal forms. In this regime it is known that the mean lateral front grows as t(0.5). Here the length of each individual branch is shown to grow (before being screened off) with a power-law behavior t (alpha(n)). The value of the exponent alpha(n) (0.5< or = alpha(n) < or =1) is determined from the start by the strength of the initial disturbance. Coarsening then takes place, when the branches of small alpha(n) are screened off by their neighbors. The corresponding decay of the growth of a weak branch is exponential and defined by its geometrical position relative to its dominant neighbors. These results show that the branch structure results from a deterministic growth of initially random disturbances. At large values of the Peclet number, the faster of the side branches escape and become independent dendrites. The global structure then covers a finite fraction of the two-dimensional space. The crossover between the two regimes and the spacing of these independent branches are characterized.

Journal Article↗

PubMed2004

[Postoperative bleeding after laser surgery in head and neck tumors].

BACKGROUND: There are different reports in the literature how often postoperative hemorrhage occurs after laser resection of head-and-neck tumours. This retrospective study investigates the frequency of postoperative hemorrhage after laser surgery of head and neck tumours. Time and extent of bleeding have been considered as well as the localization of the primary tumour and possible general risk factors. METHODS AND PATIENTS: Between 1998 and 2001, microscopic laser surgery was performed in 223 patients with previously untreated squamous cell carcinomas of the oral cavity, oropharynx, supraglottic and glottic region and the hypopharynx. In case of ultrasonographic or palpable evidence of cervical lymphadenopathy surgery included subsequent neck dissection. The mean age of the patients was 59.2 year. RESULTS: Postoperative bleeding occurred in 14 out of 223 patients (6 %). It was 9 % for oral carcinoma, patients 10 % for oropharyngeal carcinoma, 5 % for supraglottic carcinoma and none for glottic and hypopharyngeal carcinoma. 5 patients were treated conservatively, 4 patients were controlled bei cautery and ligation, 1 patient was treated with ligation of the lingual artery and in 2 cases ligation of the external carotid artery was performed. 1 patient had a fatal hemorrhage. CONCLUSIONS: Laser-surgical resection of head and neck carcinomas does not lead to a higher incidence of bleeding complications compared to ordinary surgery.

Adult↗

PubMed2003

[Common errors of intraoperative navigation in lateral skull base surgery].

BACKGROUND AND OBJECTIVE: The knowledge of disturbing factors for navigated surgical procedures in lateral skull base surgery will help the user to identify, avoid, and correct these errors. PATIENTS/METHODS: Based on our experiences with 85 patients undergoing surgery of the lateral skull base, errors of hard- and software, of image acquisition and image transfer, of patient registration, user-related errors as well as strategic errors were analyzed. RESULTS: Any impairment of the camera field leads to functional limitation of optical systems to the same extent as electromagnetic systems can be affected by ferromagnetic materials. Standard patient registration procedures as well as the lack of compensation for soft tissue shift may cause problems. CONCLUSIONS: While dealing with navigation devices in lateral skull base surgery, the user must pay critical attention to certain details in order to recognize and interpret possible malfunction.

Computer Systems↗

PubMed2003

Laparoscopic management of complications following laparoscopic Roux-en-Y gastric bypass for morbid obesity.

BACKGROUND: We reviewed our experience with complications following laparoscopic Roux-en-Y gastric bypass (LRYGB) that were managed laparoscopically. METHODS: A total of 246 consecutive morbidly obese patients (mean body mass index, 50.9 kg/m2) underwent LRYGB by three surgeons at two institutions. All patients met National Institutes of Health criteria for surgical treatment of morbid obesity. Patients were followed prospectively. RESULTS: A total of 62 patients (25.2%) developed 64 complications, 34 of which (13.8%) required a surgical intervention. Twenty-seven of the 34 procedures were performed laparoscopically. Gastrojejunostomy stricture was the most common complication (8.9%), followed by intestinal obstruction (7.3%) and gastrointestinal bleeding (4%). The intestinal obstruction was secondary to adhesions (n = 6), internal hernia at the level of the transverse mesocolon (n = 3), jejunojejunostomy stricture (n = 3), and cicatrix around the Roux limb at the level of the transverse mesocolon (n = 3). Other complications included gastrojejunostomy leak (1.6%), symptomatic gallstone disease (2.8%), and gastric remnant perforation (0.8%). One patient underwent a negative laparoscopy to rule out anastomotic leak. There were 3 deaths in this series of patients, 2 attributable to anastomotic leak. CONCLUSIONS: A variety of complications can present after LRYGB. Laparoscopy is an excellent technique to treat these complications.

Adult↗

PubMed2003

[Results in terms of hearing results after surgical closure of labyrinthine fistulas].

OBJECTIVES: We investigated the results achieved in terms of hearing in 36 patients who had each undergone resection of a cholesteatoma and closure of a labyrinthine fistula. PATIENTS AND METHODS: These patients included 28 who had a fistula of the semicircular canal, in 7 of them with an opened perilymphatic space. In 8 cases we found a fistula of the cochlea, with with a perilymphatic leak 7 in of them. We compared the sensorineural threshold before and after surgery and also the results in the two groups. Patients who were deaf preoperatively were excluded from further analysis. RESULTS: Hearing did not improve in any of the patients (n=5) who were deaf preoperatively. There was no significant difference in changes to the hearing threshold between patients with fistula of the cochlear and those with fistula of the semicircular canal with opened perilymphatic space; nor did patients with a fistula of the semicircular canal without perilymphatic leakage have a better outcome than patients with an open membranous labyrinth. CONCLUSIONS: The outcome of cholesteatoma resection and closure of the fistula in a single operation was good. Perilymphatic leakage seems to be predictive of a poorer result in terms of hearing.

Audiometry, Pure-Tone↗

PubMed2003

[Intratympanic interval therapy of Menière disease with gentamicin with preserving cochlear function].

For the effective treatment of Menière's disease, gentamicin should be administered at most three times: on days 1, 8 and 15. More than 50% ( n=30) of 57 patients seen between 1997 and 2000 only needed a single dose of gentamicin to obtain a sufficient reaction (single shot-therapy). Vertigo attacks were controlled in 95% of our 57 patients and there were no substantial hearing losses. Four patients lost 15 dB. Tinnitus (46%) and ear pressure (69%) could be controlled or improved. The intratympanic injection-technique (single dose=0.3 ml=12 mg) performed under local anaesthesia is simple and superior to any other procedure. The peak concentration of gentamicin is reached after 2-6 days (average 4.6 days). As soon as signs of inner ear reaction are observed, treatment has been effective and must be stopped immediately to avoid over-intoxication and damage to the cochlea.

Anti-Bacterial Agents↗

PubMed2003

[Epidemiological data of patients with sudden hearing loss -- a retrospective study over a period of three years].

In this retrospective study data of 257 patients (11- 6 years; 52 % male, 48 % female) admitted during the last three years for treatment of sudden unilateral hearing loss are statistically evaluated. No correlation with coexisting disease like hypertension, coronary heart disease, hypercholesteremia, arthropathy of the cervical spine, diabetes, thyroid disorders or nicotine abuse were evident. In 194 patients (75 %) total remission was achieved after rheological therapy. Patients additionally treated with steroids had a significant better outcome. Younger patients had higher remission rates. The best prognosis was found for patients with hearing loss in the lower frequency range. There were no differences in remission rates for patients with preexisting sensorineural hearing loss or chronic otitis media. Also patients suffering from recurrent episodes of sudden hearing loss had a similar outcome also.

Adolescent↗

PubMed2003

[The effects of Streptolysin-O and sodium hyaluronate on the permeability of the round window membrane in guinea pigs--an electrophysiologic study].

BACKGROUND: The round window membrane (RWM) acts like a barrier for topically applied substances into the middle ear preventing diffusion into the perilymphatic fluid compartment. MATERIAL AND METHOD: In an animal model, modulation of the permeability of the RWM was attempted using Streptolysin-O (SLO) in various concentrations and sodium hyaluronate. Thereafter, the effect of intratympanically applied Lidocain 2 % on hearing threshold measured by auditory brainstem response was tested for Lidocain 2 % and Lidocain 2 % in combination with SLO or sodium hyaluronate. RESULTS: The results show that both, SLO and sodium hyaluronate, influence the effect of Lidocain 2 % on hearing thresholds as an indirect sign for changes of the permeability of the RWM. However SLO by itself in low concentrations decreased auditory thresholds in some animals while this was never observed with sodium hyaluronate. CONCLUSIONS: Our findings preclude SLO and favor sodium hyaluronate as a modulator of RWM permeability in therapeutic trials.

Animals↗

PubMed2003

Comparison of Different Computer-Aided Surgery Systems in Skull Base Surgery.

Computer-aided surgery (CAS) based on high-resolution imaging techniques represents an important adjunct to precise intraoperative orientation when anatomical landmarks are distorted or missing. Several commercial systems, mostly based on optical or electromagnetic navigation principles, are on the market. This study investigated the application of EasyGuide(R), VectorVision(R), and InstaTrak(R) CAS systems in ENT surgery under practical and laboratory conditions. System accuracy, time required, handling, individual features, and practicality were examined in 155 patients who underwent endonasal sinus surgery and in 23 patients who underwent anterior or lateral skull base procedures. The VectorVision(R) and InstaTrak(R) CAS systems proved to be suitable for routine application in surgery involving the paranasal sinuses and various regions of the anterior skull base by helping to avoid critical structures and to determine minimally invasive approaches.

Journal Article↗

PubMed2002

Outcome analysis of laparoscopic Roux-en-Y gastric bypass for morbid obesity. The first 116 cases.

BACKGROUND: Morbid obesity has been described as a continuing epidemic affecting a growing portion of our population. We report an outcome analysis of our early experience with laparoscopic Roux-en-Y gastric bypass (LRYGB) in the treatment of morbid obesity. METHODS: Two surgeons performed 116 consecutive LRYGBs at a single institution, creating a 25-ml pouch and a 90- to 150-cm Roux limb. The prospectively collected data included patient demographics, comorbidities, postoperative weight loss, and complications. RESULTS: All eight conversions to an open procedure occurred early during the experience of the surgeons. The mean operating room time for the first 50 cases was 272 min, which decreased to 198 min with experience. The mean length of hospital stay was 3 days. There were 34 complications in 27 patients (23.3%), 14 of which (12%) required reoperation. At 18 months postoperatively, the patients had lost 77% of their excess weight, and their body mass index had decreased from a mean of 49.3 to 32.6 kg/m2. As a result of LRYGB, 25% of the patients were rendered completely free of any pharmacologic treatment for their preexisting comorbidities. CONCLUSIONS: Although technically challenging, LRYGB can be performed safely with excellent long-term results. The mean operating room time and conversion rate improved with experience. As this study showed, LRYGB achieves an excellent rate of weight loss and improvement in preoperative comorbidities with a minimal length of hospital stay and an acceptable complication rate.

Adult↗

PubMed2002

[Intraoperative navigation in surgery of paranasal sinus and anterior skull base].

BACKGROUND AND OBJECTIVE: Based on physical laws, stage of technical development and the user's individual skills a number of possible errors have to be considered for the application of CAS in paranasal sinus and anterior skull base surgery. PATIENTS/METHODS: Based on our experiences of 436 navigated cases hard- and software errors, errors of image acquisition and transfer, errors of patient registration, user related errors as well as strategic errors are analyzed. RESULTS: Any hindrance of the camera field leads to a limitation of functionality of optical systems in the same extent as electromagnetic systems can be affected by ferromagnetic materials. The mode of image acquisition is dependent from the CAS-system involved. The reconstruction algorithm requires particular attention. The patient registration based on the headset proved to be reliable for endonasal sinus surgery. CONCLUSIONS: In dealing with navigation devices in paranasal and anterior skull base surgery the user must pay critical attention to possible malfunction in order to guarantee a successful image guided surgical procedure.

Algorithms↗

PubMed2002

Neural conservation in skull base surgery.

Surgical treatment of lesions of the skull base carries significant risk to the functioning of the cerebral hemispheres, the brain stem and the cranial nerves. This risk is due both, to problems associated with maintaining an adequate blood flow while exposing and removing the tumor and to direct or indirect trauma to the brain, perineural tissues and cranial nerves. These risks may be reduced if information about possible implications of surgical maneuvers on the cerebral blood flow and on the function of the patients central nervous system and cranial nerves is available and can be monitored during surgery of the skull base. The use of electromyographic neuromonitoring for the facial nerve and of BERA-monitoring for the auditory nerve have been described and are now standard methods to achieve these goals. In acoustic tumors in the last several years beside preservation of the function of the facial nerve hearing preservation especially in small tumors has been one of the primary goals in acoustic neuroma surgery. Computer assisted surgery and intraoperative imaging for lateral skull base surgery are still in their infancy but promise to allow further improvement of neural conservation.

Brain↗

PubMed2002

Clinical characteristics of 13 solid organ transplant recipients with ganciclovir-resistant cytomegalovirus infection.

BACKGROUND: Ganciclovir-resistant (GCV-R) cytomegalovirus (CMV) is now being reported with increasing frequency in solid organ transplant recipients. OBJECTIVE: To describe the clinical characteristics and outcomes of all solid organ transplant patients with GCV-R CMV seen between 1990 and 2000 at a single center. METHODS: Patients with clinically suspected GCV resistance had viral isolates subjected to phenotypic analysis by plaque reduction assay, and also genotypic analysis. Medical records of the 13 patients with GCV-R CMV were reviewed for demographic, microbiologic, clinical, and pathologic data. RESULTS: Thirteen patients were identified, including 5 kidney, 1 heart, and 7 lung transplant recipients. All but one patient (92%) were CMV donor seropositive, recipient negative (D+/R-), and 11/13 (85%) had tissue-invasive CMV. CMV viremia was recurrent in 9/13 (69%); in 2 others, the first CMV episode was fatal. Overall, 9/13 (69%) of patients have died, all of CMV or its complications. Of the 10 who received foscarnet, only one survived. All patients had received GCV-based prophylactic regimens; 8/13 patients (62%) had received CMV hyperimmune globulin (CMVIG) as part of prophylaxis, 6/13 (46%) had received oral ganciclovir, and 5/13 (38%) had received intermittent (3 x/week) IV ganciclovir for prophylaxis. CONCLUSIONS: GCV-R CMV is associated with CMV D+/R- status, tissue-invasive disease, and high mortality even with foscarnet therapy. Exposure to less than fully therapeutic levels of GCV, in the form of oral or intermittent IV GCV, is common. The use of CMVIG in prophylaxis does not appear to prevent resistance. Further work remains to be done to elucidate the risk factors and optimal mode of prophylaxis and treatment for GCV-R CMV.

Cytomegalovirus↗

PubMed2001

Comparison of ethidium bromide-stained agarose gel electrophoresis and automated fragment analysis for evaluation of IgH gene products.

In acute lymphoblastic leukemia (ALL) patients, automated fluorescence fragment analysis (ALF) has been reported to improve the monoclonality detection rate of immunoglobulin heavy chain genes (IgH) polymerase chain reaction (PCR) analysis. This study performed complementary determining region (CDR) I and III PCR on samples from 135 patients with B-cell neoplasias and 25 healthy controls. The value of ALF was investigated in comparison to the widely used ethidium bromide (ETB)-stained agarose gels (AGGE). ETB-stained AGGE detected monoclonal CDR III PCR products in 53/72 ALL, in 22/34 non-Hodgkin's lymphoma (NHL), 13/22 multiple myeloma (MM), and 2/7 monoclonal gammopathies (MGUS). ALF identified monoclonal CDR III amplificates in 55/72 ALL, 23/34 B-NHL, 14/22 MM, and 2/7 MGUS. AGGE achieved clonal CDR I PCR results in 30/64 samples, while ALF detected 34 clonal CDR I product patterns. Taking together, ETB-stained AGGE revealed monoclonality in 120/199 PCR products versus 129/199 by ALF. Compared with AGGE and ETB-staining, ALF offers a slightly increased sensitivity and can be recommended for the evaluation of difficult samples.

DNA, Neoplasm↗

PubMed2001

Expression of matrix-degrading cysteine proteinase cathepsin K in cholesteatoma.

Cholesteatoma is a nonneoplastic lesion of the middle ear space or mastoid that is histologically characterized by a progressive bone erosion of the ossicles and surrounding bone. Several matrix-degrading enzymes have been implicated as mediators of this bone erosion. Because the novel cysteine proteinase cathepsin K has been shown to play a central role in bone resorption, we examined the expression of this enzyme in tissue specimens of cholesteatoma. Tissue specimens of 9 patients with cholesteatoma were obtained during middle-ear surgery. Expression of cathepsin K mRNA was determined by RT-PCR using specific primers. Immunohistochemical analysis of cathepsin K protein expression in tissue sections was performed by using the streptavidin-alkaline phosphatase technique. Expression of both cathepsin K mRNA and protein was detected in areas affected by cholesteatoma, whereas specimens of nonaffected ear cartilage and surrounding tissue were not positive. In addition, cathepsin K was detected in numerous multinucleated giant cells, particularly osteoclasts at the site of bone degradation. In contrast, keratinized squamous epithelium was negative for cathepsin K. These data demonstrate that the matrix-degrading cysteine proteinase cathepsin K may be involved in bone erosion in cholesteatoma. Strong expression of this collagenolytic enzyme in osteoclasts suggests that these cells are mainly involved in cathepsin K-mediated bone destruction.

Adult↗

PubMed2001

Prospective BCR-ABL analysis by polymerase chain reaction (RT-PCR) in adult acute B-lineage lymphoblastic leukemia: reliability of RT-nested-PCR and comparison to cytogenetic data.

The reliability of routine BCR-ABL RT-nested-PCR was evaluated in 1453 B-lineage ALL or hybrid leukemia at initial diagnosis by RT-nested-PCR. All BCR-ABL-positive (n = 642) and 176 BCR-ABL-negative samples underwent a second RT-PCR. In 518 patients, karyotyping and/or FISH was compared to the BCR-ABL status. The second RT-PCR revealed in 155/642 initially positive samples a divergent result (153 BCR-ABL-negative, two other transcripts) that in most cases turned out to be caused by contaminations in the first RT-nested-PCR. Confirmatory RT-PCR detected 2/176 false negative first RT-nested-PCR results. Thirty-nine specimens remained ambiguous despite different RT-PCR approaches. As far as cytogenetic evaluation and FISH is available (n = 23), the majority but not all patients with an ambiguous RT-PCR result were Ph-negative (n = 18). RT-nested-PCR and cytogenetics yielded in 346 of 383 evaluable samples a concordant result. Differing results are given and account in part to the lower sensitivity of karyotyping. Taken together, confirmed RT-PCR detected BCR-ABL fusion transcripts consistently in 487 out of 1453 ALL samples (c-ALL: 43%, pre-B ALL: 34%, pro-B ALL: 5%, B-ALL: 0%, hybrid leukemia: 5/11). Since false positive initial RT-nested-PCR data were frequent, either confirmatory second RT-PCR or FISH analysis is warranted to guarantee sensitive and reliable results of utmost clinical relevance.

Adult↗

PubMed2001

[The Interesting Case No. 42. Differential diagnosis of epistaxis].

Epistaxis is a symptom and one of the most frequent medical emergencies. In most cases haemorrhages concern the anterior parts of the septum, in particular the Locus Kiesselbachi. Thus they are harmless and therapy is easy to handle. We report a case of a 55-year-old lady with relapsing epistaxis due to a pseudoaneurysm after surgery of a meningioma of the sphenoid bone. This type of epistaxis is rare and may culminate into a life-threatening event. The case demonstrates the importance of an exact differential diagnostic evaluation by use of modern imaging techniques for severe and life-threatening symptomatic nose-bleeding.

Aneurysm, False↗