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Biomedical subjects

U Maier

Publications and source records attributed to U Maier.

At least 37 records · Page 2Linked to original sources
PubMed1998

Two-dimensional magnetic particles

Single two-dimensional (2D) atomically thick magnetic particles of cobalt and iron with variable size and shape were fabricated by combining a mask technique with standard molecular beam epitaxy. Reduction of the lateral size of in-plane magnetized 2D cobalt films down to about 100 nanometers did not essentially modify their magnetic properties; although the separation of boundaries decreased greatly, neither domain penetrated the particle, nor was any sizable shape anisotropy observed. The mutual interaction of 2D cobalt particles was negligible, and the magnetic state of a single particle could be switched without modifying the state of the neighbors. Perpendicularly magnetized iron particles did not exhibit such responses. These results suggest that only a few atoms forming a 2D in-plane magnetized dot may provide a stable elementary bit for nanorecording.

Journal Article↗
PubMed1998

Gbetagamma stimulates phosphoinositide 3-kinase-gamma by direct interaction with two domains of the catalytic p110 subunit.

Class I phosphoinositide 3-kinases (PI3Ks) regulate important cellular processes such as mitogenesis, apoptosis, and cytoskeletal functions. They include PI3Kalpha, -beta, and -delta isoforms coupled to receptor tyrosine kinases and a PI3Kgamma isoform activated by receptor-stimulated G proteins. This study examines the direct interaction of purified recombinant PI3Kgamma catalytic subunit (p110gamma) and Gbetagamma complexes. When phosphatidylinositol was used as a substrate, Gbetagamma stimulated p110gamma lipid kinase activity more than 60-fold (EC50, approximately 20 nM). Stimulation was inhibited by Galphao-GDP or wortmannin in a concentration-dependent fashion. Stoichiometric binding of a monoclonal antibody to the putative pleckstrin homology domain of p110gamma did not affect Gbetagamma-mediated enzymatic stimulation, whereas incubation of Gbetagamma with a synthetic peptide resembling a predicted Gbetagamma effector domain of type 2 adenylyl cyclase selectively inhibited activation of p110gamma. Gbetagamma complexes bound to N- as well as C-terminal deletion mutants of p110gamma. Correspondingly, these enzymatically inactive N- and C-terminal mutants inhibited Gbetagamma-mediated activation of wild type p110gamma. Our data suggest that (i) p110gamma directly interacts with Gbetagamma, (ii) the pleckstrin homology domain is not the only region important for Gbetagamma-mediated activation of the lipid kinase, and (iii) Gbetagamma binds to at least two contact sites of p110gamma, one of which is close to or within the catalytic core of the enzyme.

Adenylyl Cyclases↗
PubMed1998

High incidence of nephrogenic adenoma of the bladder after renal transplantation.

BACKGROUND: Tumors of the bladder termed nephrogenic adenomas in kidney allograft recipients are believed to develop as urothelial metaplastic proliferations in response to mechanical trauma, chemical noxae, irradiation, and bacterial or viral pathogens. We report on the incidence of nephrogenic adenoma of the bladder in patients who received renal transplants during a period of 7 years and 3 months at the University Hospital of Vienna. METHODS: Diagnosis was obtained by cystoscopy and histological analysis. Nephrogenic adenoma was treated by transurethral electroresection and administration of antibiotics in case of urinary tract infections. Follow-up consisted of cytological controls of urine and bladder irrigation fluid as well as of cystoscopy every 3 months. RESULTS: In 7 of 1328 renal allograft recipients, nephrogenic adenoma could be detected after 7 to 60 months following renal transplantation. In five patients, recurrence was detected 9 to 23 months after diagnosis of the initial lesion. No evidence of malignant degeneration was observed in any patient. Nephrogenic adenoma was not related to immunosuppressive therapy, cytomegalovirus disease, or gancyclovir therapy. CONCLUSIONS: We suggest that after successful transurethral electroresection of nephrogenic adenomas, cytological controls are adequate every 3 months. Only in renal transplant patients with recurrence of voiding disturbances, macrohematuria, or urinary tract infection are cystoscopy and biopsy indicated in the routine follow-up regimen.

Adenoma↗
PubMed1998

Nephrogenic adenoma in renal transplant recipients: a truly benign lesion?

OBJECTIVES: Nephrogenic adenoma is a benign metaplastic lesion of the urinary bladder, reported to occur as a response to inflammation, trauma, intravesical therapies, and after renal transplantation. The aim of this study was to evaluate on the basis of chromosomal analysis whether nephrogenic adenoma really is benign. METHODS: Twelve renal transplant recipients with histologically verified nephrogenic adenoma were analyzed for numerical aberrations of chromosomes 7, 9, and 17. Results were related to total DNA content, p53 and Ki-67 positivity, and clinical outcome. Ten patients with superficial bladder cancer and 10 healthy renal transplant recipients formed the control groups. RESULTS: All 12 patients with nephrogenic adenoma had monosomy 9 in a mean of 24.3% (range 20% to 30%) of the evaluated cells; 3 patients had an additional trisomy 7 in a mean of 8% (range 6% to 10%) of the counted cells. Chromosome 1 7 was disomic in all patients. DNA histograms were diploid in 11 of the 12 patients and aneuploid in 1 patient. No p53 and Ki-67 positivity was present in this group. All patients with superficial bladder cancer had monosomy 9 in a mean of 79.8% (range 75% to 85%) of the counted cells. Two patients were found to have an additional trisomy 7 in 50% and 65% of the cells, respectively. The latter had an aneuploid histogram; the others had haploid/diploid histograms. p53 was negative in all specimens. Ki-67 positivity was present in 70% of these patients. All healthy transplant recipients had disomic chromosomal patterns according to diploid DNA histograms and negative immunocytochemical results. CONCLUSIONS: Even if in a lower percentage of cells, aberrations of chromosome 7 and 9 were detected in nephrogenic adenoma. It therefore cannot be excluded that nephrogenic adenomas in immunosuppressed renal transplant recipients may develop into malignant lesions.

Adolescent↗
PubMed1998

Phenotypic and functional characterization of mast cells derived from renal tumor tissues.

Mast cells (MCs) originate from multipotent hematopoietic progenitor cells. However, MCs in various organs are heterogenous in terms of mediator or receptor expression and response to diverse stimuli. We characterized the phenotype and functional properties of human renal mast cells (HRMCs). Tissue was obtained from 17 patients suffering from renal tumors (transitional cell carcinoma, n = 4; renal cell carcinoma, n = 13). HRMCs were isolated by collagenase digestion. Double staining with toluidine blue and immunofluorescence using monoclonal antibodies (mAbs) revealed expression of stem cell factor (SCF)-receptor (c-kit/CD117), CD9, CD29, CD33, CD43, CD44, CD54, and CD63 on HRMCs. In contrast, HRMCs were not recognized by mAbs to CD2, CD3, CD4, CD11b, CD14, CD15, CD16, CDw17, CD19, or CD23. HRMCs were also negative for CD116 (granulocyte-macrophage colony-stimulating factor [GM-CSF] receptor alpha), CD123 (interleukin [IL]-3Ralpha), CD121a (IL-1R type I), CD122 (IL-2Rbeta), and CD127 (IL-7R) and were also found to lack C5aR (CD88). Ligand-induced activation of HRMCs through immunoglobulin (Ig)E-R or SCF-R (c-kit) resulted in histamine secretion (control: <10%; alphaIgE, 1 microg/mL: 50.12 +/-5.18%; rhSCF, 100 ng/mL: 29.24 +/- 22.39), whereas recombinant C5a, erythropoietin (EPO), IL-1 through 10, and GM-CSF exerted no effects. As determined by in situ staining, HRMCs contained tryptase, but only low or undetectable amounts of chymase. Electron microscopy confirmed the presence of MCs in renal tissues and revealed a scroll-rich granule population in HRMCs. Together, HRMCs are tryptase+, C5aR- mast cells exhibiting phenotypic and functional properties similar to those of lung MCs.

Adult↗
PubMed1997

Late ureteral obstruction after kidney transplantation. Fibrotic answer to previous rejection?

Today, the incidence of urological complications following renal transplantation is 2%-10%. Most of these complications occur within the 1st year and affect the distal ureter. We report on two patients who developed very late ureteral obstruction, 14 and 18 years after transplantation. Both patients had rejection episodes 1 and 10 months prior to the ureteral stenosis. Histological examination of one resected ureter revealed findings strongly suggestive of a rejection process. Open surgery with antirefluxive reimplantation into the bladder was successful in both patients, with a postoperative observation time of 20 and 8 months, respectively. We conclude that a percutaneous nephrostomy may be required in patients with rising creatinine and incipient hydronephrosis even long after transplantation has been performed.

Adult↗
PubMed1997

[Acromio-humeral distance and acromial shape in 3-dimensional computerized tomography reconstruction. Side comparison in supraspinatus outlet syndrome].

Mechanical irritations of the supraspinatus tendon due to a reduction of the subacromial space are considered to be a potential cause of supraspinatus outlet syndrome. The aim of the current study was, therefore, to provide a method of improved measurement of the acromiohumeral distance and the evaluation of the acromial shape. In seven patients aged 50-60 years with unilateral supraspinatus outlet syndrome, imaging with standardized, high-resolution computed tomography (CT) was performed in order to demonstrate the acromion and the subacromial space three-dimensionally. The acromiohumeral distance was measured in three reconstructed frontal sections, and the two sides of each patient were directly compared. The acromial shape was compared with the classification of Bigliani as derived from conventional radiography. Whereas the Constant Score was found to be significantly reduced in the diseased shoulders (p < 0.01), the acromiohumeral distance was not significantly lower in three standardized frontal sections. In five cases the classification of the acromial form from the conventional radiograph was confirmed by 3D CT, whereas in two cases it was shown to be different. Our results suggest that primary or secondary changes of the acromial form can be more accurately evaluated with 3D CT than with conventional radiography. A direct comparison of the two sides in patients with supraspinatus syndrome does not suggest a reduction of acromiohumeral distance in the diseased shoulder.

Female↗
PubMed1997

Determination of subacromial space width and inferior acromial mineralization by 3D CT. Preliminary data from patients with unilateral supraspinatus outlet syndrome.

A reduction of the subacromial space and an increased subacromial pressure have been considered to play an important role in the pathogenesis of rotator cuff lesions. The objective of the current study was to develop a CT based method for measuring the acromiohumeral distance and inferior acromial mineralization. In seven patients with unilateral rupture of the rotator cuff and two with impingement syndrome, transverse CT images were obtained at a section thickness of 1 mm with muscular relaxation in a standardized position. The bones were then reconstructed three-dimensionally, and the minimal vertical distance between the acromion and the humerus was determined in three secondary frontal images on both sides. The distribution of mineralization within the inferior surface of the acromion was assessed using CT osteoabsorptiometry. Although the Constant score was significantly reduced in the diseased shoulders, the width of the subacromial space was not routinely lower than on the contralateral side. In seven cases the maximal inferior acromial mineralization was identical in both shoulders, and in two cases it was lower on the affected side. These preliminary data suggest that with muscular relaxation no narrowing of the subacromial space can be detected in secondary frontal CT images, and that a potential increase of subacromial pressure is not high enough to cause a measurable increase in inferior acromial bone density. The method presented makes it possible to investigate the pathogenesis of the supraspinatus outlet syndrome in vivo with greater precision than has so far been possible with conventional radiography.

Acromion↗
PubMed1997

Late urological complications and malignancies after curative radiotherapy for gynecological carcinomas: a retrospective analysis of 10,709 patients.

PURPOSE: A retrospective study was done to analyze late urological complications following curative radiotherapy of primary gynecological carcinomas. All patients were treated at a single center and with the same radiotherapeutic regimen. The incidence of other carcinomas in these patients was also evaluated. MATERIALS AND METHODS: A total of 10,709 patients was treated using combined telebrachytherapy (dosage 67.5 Gy.) during an observation period of 22 years. RESULTS: Severe late complications were seen in 1.24% (133 of 10,709) of the patients, including irradiated bladder (65 cases, mean interval since treatment 6.7 years). Complications required surgery in 118 of 133 patients with a perioperative mortality of 4.2% (5 of 118). Overall in 4.27% (457 of 10,709) of the patients another malignancy developed after (29.1%), during (26.3%) and before (44.6%) radiotherapy. Subsequent malignancies after treatment were predominantly seen in the genital region (88.4%) but they were also in the irradiated nongenital area (0.13%, 14 of 10,709). Of the latter patients 6 had urothelial bladder cancer, which represents a relative risk of 4.66 (based on the Austrian female population) to develop bladder cancer after radiotherapy for gynecological cancer. CONCLUSIONS: Late urological complications after radiotherapy of the pelvis are rare but severe. Surgical therapy of irradiated tissues has a higher complication rate compared to surgery on nonirradiated tissue.

Female↗
PubMed1997

Preoperative evaluation of tumor extension in patients with recurrent cervical cancer.

BACKGROUND: Pelvic exenteration is an option in the treatment of locally recurrent cervical cancer. Various preoperative diagnostic procedures in the estimation of tumor invasion of the bladder and rectum or lymphonodal involvement were evaluated. DESIGN: The sensitivity and specificity of cystoscopy, intravenous pyelography, irrigoscopy, rectoscopy, and computed tomography were evaluated by comparing the preoperative findings with the histological result as the 'golden standards'. RESULTS: In the assessment of bladder invasion the sensitivity of cystoscopy, intravenous pyelography and computed tomography was 22.2%, 55.6% and 55.6%, respectively. The overall sensitivity of the three diagnostic procedures was 77.8%. In the assessment of invasion of the rectum irrigoscopy, rectoscopy and CT revealed a sensitivity of 33.3%, respectively. Only 50% of all cases with tumor infiltration of the rectum showed positive results when all three diagnostic procedures were combined. The sensitivity and specificity of computed tomography in the diagnosis of lymphonodal involvement were 75% and 83.3%, respectively. CONCLUSION: We think that there is an obvious necessity for all diagnostic procedures for patient selection prior to pelvic exenteration. However, all these investigations are not conclusive but complement each other. Prior to pelvic exenteration, critical interpretation of all preoperative diagnostic procedures is mandatory, otherwise surgery results in an unintended palliative procedure.

Adult↗
PubMed1996

The impact of liver transplantation on endocrine status in men.

OBJECTIVE: There are few longitudinal data on the endocrine changes which occur after liver transplantation. We have therefore studied the impact of orthotopic liver transplantation (oLTX) on the hypothalamic-pituitary-gonadal hormone axis and sex steroid metabolism in men. PATIENTS AND STUDY DESIGN: Ten male patients with end-stage liver failure due to alcohol induced cirrhosis (n = 2), virus-induced cirrhosis (n = 5), primary biliary cirrhosis (n = 1) and idiopathic cirrhosis (n = 2) were included in a prospective study analysing the impact of oLTX on endocrine status. They were studied before and after oLTX with a mean follow-up of 11.6 months (range 4-23) following transplantation. MEASUREMENTS: Serum levels of LH, FSH, testosterone (TE), free TE, PRL, cortisol, oestradiol (E2) and sex hormone binding globulin (SHBG) were analysed with commercially available radioimmunoassays in all individuals before and after oLTX. Gonadotrophin releasing hormone stimulation tests were done in 5 patients before and after oLTX. Additionally, a complete urological assessment with a detailed questionnaire on sexual function was obtained from all individuals. RESULTS: Prior to oLTX, endocrine status was invariably abnormal, the most prominent finding being a pathological decrease of TE in 90% and of free TE in all cases. After successful oLTX, all individuals had physiological levels of TE and of free TE which increased twofold (P < 0.01) and tenfold (P < 0.0001), respectively. Additionally, serum gonadotrophin (LH/FSH) levels increased in the majority of patients, while E2 decreased following oLTX. Endocrine changes extended beyond the hypothalamic-pituitary-gonadal hormone axis, as shown by a decrease in PRL (P < 0.02) and SHBG (P < 0.01) after transplantation. GnRH tests revealed normal stimulation of LH and FSH before and after oLTX in all cases. Libido, potency and frequency of sexual intercourse improved significantly after oLTX in the majority of patients. CONCLUSIONS: These findings demonstrate the ability of the hypothalamic-pituitary-gonadal hormone axis and sex steroid metabolism to resume physiological function following orthotopic liver transplantation in men. Correspondingly, sexual function returns to normal in the majority of patients, despite significant alterations prior to orthotopic liver transplantation.

Adult↗
PubMed1996

Adrenalectomy--still a must in radical renal surgery?

OBJECTIVE: To investigate the incidence of adrenal involvement and survival in patients with renal cell carcinoma. PATIENTS AND METHODS: A retrospective, multicentre trial was initiated by the Austrian Association of Urologic Oncology (AUO); between January 1980 and December 1984, 225 patients were eligible for the study. All patients had unilateral renal tumours and nephrectomies were performed either with (group A, 109 patients) or without (group B, 116 patients) adrenalectomy. The two groups were matched for sex, age, laterality and nodal status. The mean follow-up time was 78 months. RESULTS: The location of the intrarenal tumour had no significant effect on adrenal involvement. By univariate and multivariate analysis (Cox's proportional hazards model) significant differences in outcome were found only for pT stages. The mean survival times of patients in group A were 122.9 months in those with stage pT1/2, 76.6 months with stage pT3 and 75.3 months with stage pT4. In group B, survival times were 109 months in those with stage pT1/2 (not significant) and 111 months in stage pT3 (P = 0.0076). Eight patients had adrenal involvement and died from their tumours after a median of 15.3 months (range 4-63). The slightly longer survival of patients in group B with stage T1/2 tumours and the significantly better survival of patients with stage T3 disease may be attributable to statistical bias, but there was no benefit from adrenalectomy. CONCLUSION: The effect of adrenalectomy on the prognosis was at best comparable to that of lymphadenectomy and no curative effect was demonstrated. The removal of a healthy adrenal may be detrimental and cause subsequent problems in those patients requiring hormone replacement.

Adrenalectomy↗
PubMed1996

[Studies on radiation exposure in retrograde sclerotherapy of the testicular vein].

PURPOSE: Prospective evaluation of different radiation exposure parameters in a large series of varicoceles. The dependency of the square area product on the different therapists was calculated in addition. MATERIAL AND METHOD: Between 5/91 and 12/93 a total of 737 sclerotherapies were performed on 465 patients. The following parameters were measured prospectively: Square area product (n = 737), fluorotime (n = 737), symphysis surface doses (n = 24), gonadal doses (n = 49), catheterisation time (n = 737). 608 of the sclerotherapies were performed by 4 similar experienced radiologists (U1 - U4). The individual fluorotimes, square area products and the average square area product per minute fluorotime were calculated. RESULTS: The average gonadal doses was 0.01 mSv. Calculation of the square area product per minute fluorotime revealed a useful parameter to demonstrate the potential for further dose reduction, because the results ranged from 566 mGy x cm2/min to 988 mGy x cm2/min. There is no need for a time limit for this interventional procedure. CONCLUSION: The gonadal doses is so low that it can be considered negligible. However, in view of the considerable differences in the square area product per minute, close attention must be paid to the technique by which th fluorotime is determined.

Adolescent↗