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Biomedical subjects

K Donath

Publications and source records attributed to K Donath.

At least 19 recordsLinked to original sources
PubMed2005

Automated segmentation of the optic nerve head for diagnosis of glaucoma.

Glaucoma is the second most common cause of blindness worldwide. Low awareness and high costs connected to glaucoma are reasons to improve methods of screening and therapy. A well-established method for diagnosis of glaucoma is the examination of the optic nerve head using scanning-laser-tomography. This system acquires and analyzes the surface topography of the optic nerve head. The analysis that leads to a diagnosis of the disease depends on prior manual outlining of the optic nerve head by an experienced ophthalmologist. Our contribution presents a method for optic nerve head segmentation and its validation. The method is based on morphological operations, Hough transform, and an anchored active contour model. The results were validated by comparing the performance of different classifiers on data from a case-control study with contours of the optic nerve head manually outlined by an experienced ophthalmologist. We achieved the following results with respect to glaucoma diagnosis: linear discriminant analysis with 27.7% estimated error rate for automated segmentation (aut) and 26.8% estimated error rate for manual segmentation (man), classification trees with 25.2% (aut) and 22.0% (man) and bootstrap aggregation with 22.2% (aut) and 13.4% (man). It could thus be shown that our approach is suitable for automated diagnosis and screening of glaucoma.

Algorithms↗
PubMed2004

De novo bone formation using bovine collagen and platelet-rich plasma.

In order to regenerate critical-size bone defects, a variety of bone substitutes is used in addition to autogenous bone. The regenerative capacity of these bone substitutes is usually compared to the efficacy of autogenous bone known as the "golden standard". Different cytokines influence the regeneration process because of their morphogenic or mitogenic properties. Platelet-rich plasma (PRP), a platelet concentrate, is characterised by having a positive effect on wound healing, reducing bone graft resorption and increasing the density of bone transplants. This experiment was commenced with a view to studying the osseous defect regeneration after placing various combinations of "filler materials" in experimentally created defects in the forehead of adult pigs. Regeneration by means of grafted autogenous bone (Group 1) or a bovine collagen based medical device (Group 4) alone and combined with PRP in two concentrations (Groups 2, 3, 5 and 6) was evaluated by means of microradiography and light microscopy after 2, 4 and 12 weeks. The microradiographic and light microscopic findings showed that autogenous bone in combination with PRP (Groups 2 and 3) had a significant accelerating effect on early bone regeneration (2 weeks). This effect was not evident when PRP was added to the bovine collagen (Groups 5 and 6). When using the collagen alone, significantly higher mineralisation values were achieved after 2 and 4 weeks than when using autogenous bone alone. After a 12-week observation period, the existing differences between the healing processes in the various groups were more or less levelled out. In summary, the results of the study indicate that clinically autogenous bone, as expected, is the ideal defect filler. Combining autogenous bone with PRP did not provide significantly better results. The findings in the groups treated with bovine collagen indicate that its local application mimics the effect of autogenous bone and amplifies bone regeneration when comparing with the control defect.

Animals↗
PubMed2004

Multimodal retinal image registration for optic disk segmentation.

OBJECTIVES: The analysis of the optic disk morphology with the means of the scanning laser tomography is an important step for glaucoma diagnosis. A method we developed for optic disk segmentation in images of the scanning laser tomograph is limited by noise, non-uniform illumination and presence of blood vessels. Inspired by recent medical research, we wanted to develop a tool for improving optic disk segmentation by registration of images of the scanning laser tomograph and color fundus photographs and by applying a method we developed for optic disk segmentation in color fundus photographs. METHODS: The segmentation of the optic disk for glaucoma diagnosis in images of the scanning laser tomograph is based on morphological operations, detection of anatomical structures and active contours and has been described in a previous paper. The segmentation of the optic disk in the fundus photographs is based on nonlinear filtering, Canny edge detector and a modified Hough transform. The registration is based on mutual information using simulated annealing for finding maxima. RESULTS: The registration was successful 86.8% of the time when tested on 174 images. Results of the registration have shown a very low displacement error of a maximum of about 5 pixels. The correctness of the registration was manually evaluated by measuring distances between the real vessel borders and those from the registered image. CONCLUSIONS: We have developed a method for the registration of images of the scanning laser tomograph and fundus photographs. Our first experiments showed that the optic disk segmentation could be improved by fused information from both image modalities.

Fundus Oculi↗
PubMed2003

Quality of generalist vs. specialty care for people with HIV on antiretroviral treatment: a prospective cohort study.

OBJECTIVES: To describe health-care use by persons with HIV in an urban area of Switzerland (Zurich). Further, to compare the different health-care settings. DESIGN: A 1-year prospective cohort study recruiting 60 patients at general practices and 60 patients at a specialized university outpatient clinic. METHODS: Patients and their treating physicians were interviewed or answered questionnaires, respectively, at baseline, month 6 and 12. RESULTS: During the study period, five patient groups were identified among the 106 enrolled patients, of whom (i) 42% saw a general practitioner exclusively, (ii) 31% were treated at the specialized outpatient clinic, (iii) 8% were in shared care, (iv) 10% changed health-care model, and (v) 9% were lost to follow-up. Baseline demographic, psychosocial and clinical data were similar among patient groups. At study end, the proportion of patients with HIV-1 RNA < 400 copies/mL was 72%, 74%, 88%, 55% among groups (i) to (iv), respectively (ns), and 22% at month 6 among those lost to follow-up. Indicators for quality of care were similarly good among all patient groups. CONCLUSIONS: A well-working system offers high-quality healthcare to persons living with HIV, where existing teams of specialty and primary health-care professionals efficiently and effectively co-operate.

Adult↗
PubMed2002

[Chronic myoepithelial sialadenitis - symptomatology, clinical signs, differential diagnostics].

UNLABELLED: In the differential diagnosis of mass lesions of the salivary glands, myoepithelial sialadenitis (MESA), i. e. benign lymphoepithelial lesion, carries particular importance because of its association with Sjoegren's syndrome and development of malignant lymphoma. In the present study, epidemiology and clinical findings were analysed in relation to presence of MESA, Sjoegren's syndrome and lymphoma development. MATERIAL AND METHOD: 67 patients, histopathologically classified by the salivary gland registry, were analysed retrospectively in regard to their clinical presentation, especially in regard to the chronical process of inflammation as present in MESA. RESULTS: MESA primarily affects women in the 5th and 6th decade and regularly the parotid gland; in 44.8 % of the cases, there is multiple organ presentation. Xerostomy (38.5 %) is usually present (in 88,9 % of all cases) before or at clinical onset of gland inflammation, whereas xerophthalmy (28.4 %) did not show such a correlation. In general, rheumatic diseases (23.9 %) precede the gland-symptoms in 77.8 % of the patients. In 31.3 % of the cases a Sjoegren's syndrome was present. 26.9 % of the patients developed a malignant Non Hodgkin's Lymphoma (88.9 % of the MALT-type). CONCLUSION: The most important clinical relevance of MESA lies in the higher probability to develop malignant lymphoma; this requires adequate staging-procedures and proper histopathological examination of sialogenic and nodal masses, especially over the course of the disease.

Adult↗
PubMed2002

Evaluation of sporadic cases of odontogenic keratocysts in multicentric study.

The aim of this retrospective study was to report frequency of sporadic odontogenic keratocysts (sOKC) according to the age and gender, as well as location (mandible, maxilla, soft tissues, and maxillary sinus). Four hundred and twenty nine sOKC confirmed pathohistologically in a period from 1965-1998 were included in this study. The average age of patients with sOKC was 43.11 (age range 10-91), in males 42.06 and in females 44.72 years. More frequently sOKC were found in males (60.61%) in comparison to the females (39.39%). Therefore, ratio between males and females was 1.5:1. Diagnosis of sOKC is usually established in patients aged 21-30 (18.88%), in males usually aged between 21-30 (23.46%), and in females aged between 11-20 (18.93%). sOKC are more frequent in males according to the age groups, except between age 61-70 where sOKC were more frequent in females. Most frequently, sOKC occurred in the mandible 70.16%, 12.35% of sOKC were found in the maxilla, 12.82% in soft tissues and 4.66% in the maxillary sinuses.

Adolescent↗
PubMed2001

Adenomatous ductal proliferation of the salivary gland.

OBJECTIVE: The objective of this study is to report a series of patients with adenomatous ductal proliferation of the salivary gland and to investigate the nature and histogenesis of this process. STUDY DESIGN: The histologic and immunohistochemical studies of 13 patients with adenomatous ductal proliferation of the salivary gland were performed. RESULTS: Ten cases coexisted with other diseases, such as salivary gland tumor or chronic parotitis. Most of the lesions were limited to 1 or 2 lobules and showed prominent ductal proliferation with some acinar cell complexes. The proliferative ducts had a compact growth pattern with little stroma. Dedifferentiation of acinar cells, identified by the loss of their secretory granules and appearing similar to intercalated duct epithelium, was seen in the early stages of adenomatous ductal proliferation. CONCLUSION: Acinar cells play a role in the histogenesis of salivary gland tumors because acinar cells clearly participate in the formation of the proliferative ducts.

Adenolymphoma↗
PubMed2001

Angiogenesis, vascular endothelial growth factor and platelet-derived growth factor-BB expression, iron deposition, and oxidation-specific epitopes in stented human coronary arteries.

Pathogenesis of in-stent restenosis remains poorly understood because information from human histopathologic studies is scarce. We used an improved saw-grinding and cutting method on methacrylate-embedded samples containing metal stents, which allows in situ hybridization and immunohistochemical analysis of in-stent restenosis. Twenty-one samples were collected 3 hours to 3 years after stenting from 6 patients aged 36 to 81 years. Except in very early samples collected within hours after the stent deployment, neovascularization was present in all segments studied. At advanced stages, extensive neovascularization was located mainly at the luminal side of the stent struts and was only rarely accompanied by inflammatory cells. The neovessels colocalized with vascular endothelial growth factor (VEGF)-A mRNA and protein expression as well as with iron deposits and oxidation-specific epitopes, which imply the presence of chronic oxidative stress. VEGF-A expression was detected in the same areas containing macrophages, endothelial cells, and, to a lesser extent, smooth muscle cells, which also showed platelet-derived growth factor-BB expression. We conclude that in-stent restenosis features neovascularization, VEGF-A and platelet-derived growth factor-BB expression, and iron deposition, which is most probably derived from microhemorrhages. These mechanisms may play an important role in the development of neointimal thickening and could provide useful targets for the prevention and treatment of in-stent restenosis.

Adult↗
PubMed2001

Peri-implant bone reactions to immediately loaded implants. An experimental study in monkeys.

BACKGROUND: There are reports which demonstrate that immediately loaded splinted implants can be osseointegrated when they are placed in the anterior part of the lower jaw. The concept of immediate loading has not been well investigated in the posterior mandible. The aim of this study was to evaluate the bone reactions around immediately loaded implants placed in the posterior region of the lower jaw in the monkey model. METHODS: Six adult Macaca fascicularis monkeys were used in this study. A total of 36 implants were placed after extraction of the second premolars, first and second molars, and complete healing of the sockets. Three control (C) group implants were placed in one quadrant of the lower jaw of each monkey. After a delay of 3 months to allow osseointegration to take place, the implants were loaded for 1 month using temporary resin bridges and later for 2 months using metal splinted crowns. In the contralateral region of the lower jaw, 3 test (T) group implants were placed and loaded immediately with the same sequence as carried out for the C implants. Specimens were examined and evaluated histologically after sacrifice. RESULTS: All of the implants were osseointegrated. Compact, cortical bone in contact with the implant surface without any gaps or connective tissue formation was observed. CONCLUSIONS: It was concluded that immediately loaded, splinted implants can be osseointegrated with a similar hard and soft tissue peri-implant response as delayed-loaded implants in the posterior mandible.

Alveolar Process↗
PubMed2000

A new approach to demonstrate cellular activity in bone formation adjacent to implants.

Bone tissue repeatedly formed in titanium 6-aluminum 4-vanadium rabbit bone harvest implants was collected in vivo at various times between 12 days and 5 weeks. Qualitative and quantitative examinations on undecalcified thin sections were performed in the light microscope. The amount of bone tissue was calculated on routinely stained sections. Alkaline (ALP) and acid phosphatase (ACP) enzyme activities were investigated. We also performed immunohistological detection of bone matrix proteins. Increasing bone density as well as an increasing mineralization of the tissue was observed in the biopsies with increasing time. The ALP and ACP activities were similar at short times (12 days and 2 weeks). With increasing time the ALP activity was stronger than that of ACP. The results from the immunohistochemical detection of osteonectin, osteopontin, bone sialoprotein, and collagen I and II demonstrated changes in the tissue differentiation with time. The tissue formation in the canal became more mature with time of ingrowth, as observed with the various techniques used in this study. Owing to these methodical developments, undecalcified ground sections may be used for detailed analysis of various phases of tissue formation in close proximity to implants.

Acid Phosphatase↗
PubMed2000

Histological evaluation of different biodegradable and non-biodegradable membranes implanted subcutaneously in rats.

Different types of biodegradable membranes have become available for guided tissue regeneration. The purpose of this study was to evaluate histologically three different biodegradable membranes (Bio-Gide, Resolut and Vicryl) and one non-biodegradable membrane (expanded polytetrafluoroethylene/e-PTFE) implanted subcutaneously in rats. Five subcutaneous pouches were created in each of 24 rats. One of the four test membranes was randomly placed in each of the four pouches and one pouch was left empty to serve as a control. Histological evaluation was performed after 4, 10 and 21 days which demonstrated that e-PTFE was well tolerated and encapsulated by a fibrous connective tissue capsule. There was capsule formation around Resolut and Vicryl and around Bio-Gide in the early phase there was a wide inflammatory zone already. e-PTFE and Vicryl were stable materials while Resolut and Bio-Gide fragmented in the early phase. In the late phase Vicryl was surrounded by an increasing amount of multinucleated macrophages and a thin capsule, whilst around Resolut and Bio-Gide a strong foreign body reaction was observed. Also granuloma formation was noted around the fragmented Resolut material in its capsule and a mild inflammatory reaction surrounding Bio-Gide within its thin capsule.

Absorbable Implants↗
PubMed2000

Expression and mutation patterns of p53 in benign and malignant salivary gland tumors.

The expression and mutation patterns of p53 were studied in a series of 68 benign pleomorphic adenomas and 237 malignant salivary gland tumors. p53 overexpression (nuclear staining exceeding 10%) was detected in 20% of the malignant salivary gland tumors, with the highest prevalence observed in polymorphous low grade adenocarcinoma, squamous cell carcinoma, and carcinoma ex pleomorphic adenoma and the lowest in adenoid cystic carcinoma and acinic cell carcinoma. In contrast, none of the 68 benign pleomorphic adenomas had nuclear staining exceeding 10%. SSCP and nucleotide sequence analysis of exons 4 to 9 of p53 in 19 malignant tumors revealed 9 mutations in 7 tumors. Our findings indicate that p53 may be a useful marker to help discriminate between benign and malignant salivary gland tumors.

Blotting, Western↗
PubMed2000

[A clinicopathologic study on membranous basal cell adenoma].

OBJECTIVE: To investigate the clinicopathologic features and behaviour of membranous basal cell adenoma. METHODS: Twelve cases with membranous basal cell adenoma of salivary gland were analysed clinicopathologically. RESULTS: The tumors were composed of epithelial islands of various sizes and shapes. Its histologic finding was characterized by palisading of peripheral cells and excessive hyaline basal membrane. Four cases had co-existing dermal cylindromas of the scalp. In 8 cases, the tumors demonstrated multiple origin. One case showed malignant transformation and cervical lymph node metastasis. CONCLUSIONS: The differential diagnosis involved the solid variant of basal cell adenoma, basal cell adenocarcinoma, solid subtype of adenoid cystic carcinoma and basal squamous cell carcinoma. Total parotidectomy rather than superficial parotidectomy is suggested to avoid the recurrence of the tumor. A close follow up after treatment is necessary.

Adenoma↗
PubMed2000

[Histogenesis and development of membranous basal cell adenoma of the salivary gland].

OBJECTIVE: To investigate the histogenesis and development of membranous basal cell adenoma in the salivary glands. METHODS: A histological and immunohistochemical study was carried out on 12 cases of membranous basal cell adenoma in the salivary glands. RESULTS: In 4 cases, multiple focal proliferations of striated ducts in the surrounding salivary gland were conspicuous, which allowed tracing the development of the tumors from their origin. The earliest changes were characterized by hyperplasia of the basal cells of striated ducts. Continuous ductal proliferation lead to the formation of microadenomas. CONCLUSIONS: Proliferation of basal cells of the striated ducts apparently participate in, and play a main role in the histogenesis of some membranous basal cell adenomas of the salivary glands.

Adenoma↗
PubMed1999

Reactions and complications after the implantation of Endobon including morphological examination of explants.

In the study described here, the integration of hydroxyapatite (HA) ceramic implants (Endobon) was investigated. These implants have an interconnecting system of pores and are free from foreign protein. The material is not toxic, genotoxic, nor zytotoxic, and it is biocompatible. The progress of integration was investigated by means of clinical and radiological check-ups. From 10 patients, it was possible to obtain samples for histological analysis during a second operation (e.g., metal explantation). Microscopic examination showed bony integration with newly formed bone in direct contact with the HA ceramic; it also showed osteoblasts and osteoid seams. No second operation took place earlier than 4 months after the first operation, yet even after this relatively short period, bony integration was already evident. Clinical observation (based on X-rays, reports of pain, signs of inflammation) showed that in most cases healing was taking place without complications. More general operational complications such as thrombosis or nerve injury were observed in 4 patients. If the implant is not sufficiently protected from mechanical stress, bony integation will not take place, and the implant may fracture. HA ceramic, with a porosity between 30% and 80%, is not comparable to cortical bone but only to spongy bone. This factor must be taken into account when deciding whether a HA ceramic implant is indicated.

Adult↗