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Biomedical subjects

P Reichart

Publications and source records attributed to P Reichart.

At least 19 recordsLinked to original sources
PubMed2004

Three-dimensional hydrogen microscopy in diamond.

A microprobe of protons with an energy of 17 million electron volts is used to quantitatively image three-dimensional hydrogen distributions at a lateral resolution better than 1 micrometer with high sensitivity. Hydrogen images of a <110>-textured undoped polycrystalline diamond film show that most of the hydrogen is located at grain boundaries. The average amount of hydrogen atoms along the grain boundaries is (8.1 +/- 1.5) x 10(14) per square centimeter, corresponding to about a third of a monolayer. The hydrogen content within the grain is below the experimental sensitivity of 1.4 x 10(16) atoms per cubic centimeter (0.08 atomic parts per million). The data prove a low hydrogen content within chemical vapor deposition-grown diamond and the importance of hydrogen at grain boundaries, for example, with respect to electronic properties of polycrystalline diamond.

Journal Article↗
PubMed2004

Microirradiation of cells with energetic heavy ions.

The ion microprobe SNAKE at the Munich 14 MV tandem accelerator achieves beam focussing by a superconducting quadrupole doublet and can make use of a broad range of ions and ion energies, from 20 MeV protons to 200 MeV gold ions. Because of these properties, SNAKE is particularly attractive for biological microbeam experiments. Here we describe the adaptation of SNAKE for microirradiation of cell samples. This includes enlarging of the focal distance in order to adjust the focal plane to the specimen stage of a microscope, construction of a beam exit window in a flexible nozzle and of a suitable cell containment, as well as development of procedures for on-line focussing of the beam, preparation of single ions and scanning by electrostatic deflection of the beam. When irradiating with single 100 MeV (16)O ions, the adapted set-up permits an irradiation accuracy of 0.91 microm (full width at half maximum) in the x-direction and 1.60 microm in the y-direction, as demonstrated by retrospective track etching of polycarbonate foils. Accumulation of the repair protein Rad51, as detected by immunofluorescence, was used as a biological track detector after irradiation of HeLa cells with geometric patterns of counted ions. Observed patterns of fluorescence foci agreed reasonably well with irradiation patterns, indicating successful adaptation of SNAKE. In spite of single ion irradiation, we frequently observed split fluorescence foci which might be explained by small-scale chromatin movements.

Cells, Cultured↗
PubMed2004

Clinico-pathological conference 2002.

INTRODUCTION: Six cases are reported, each presented at the 11th Biennial Congress of the International Association of Oral Pathologists as an instructive case for differential diagnosis on the basis of clinical, imaging or histological features. CLINICAL PICTURE: Case diagnoses included a large, possibly intraosseous, myofibroma presenting with an oral mass; Langerhans cell histiocytosis with facial skin lesions; an intraosseous vascular hamartoma of the maxilla with worrying radiological features; an unusual mixed radiolucency of the jaw caused by cemento-ossifying fibroma; an osteosarcoma of the posterior mandible causing a well-defined radiolucency and an intraoral squamous cell carcinoma in a child.

Adolescent↗
PubMed2002

Oral and dental care and treatment protocols for the management of HIV-infected patients.

This paper describes the workings of the workshop dedicated to oral and dental care and treatment protocols for the management of HIV-infected patients. The questions addressed were: 1) What are the current ethical issues in dental care of HIV patients, do they need to be addressed? 2) Do we need to modify the dental care we give HIV-positive patients? 3) When is it necessary to give antibiotic prophylaxis to HIV-positive patients? 4) What is the evidence for the effective treatment of oral lesions associated with HIV? 5) What is the most successful palliative treatment for KS? 6) Can we provide clinical treatment that has a scientific basis rather being trial based? 7) Is ddI + hydroxy-urea an effective African alternative to HAART? 8) What is the influence of protease inhibitors and HAART on the excretion of HIV in saliva? 9) What is the effect of anti-HIV therapy on the oral mucosa and oral health? This workshop did not fully cover the issue of ddI and hydroxy-urea as an alternative HIV therapy as this was considered to be the remit of general physicians caring for patients with HIV and AIDS rather than that of oral health care workers.

AIDS-Related Opportunistic Infections↗
PubMed1995

Human immunodeficiency virus-associated squamous cell carcinomas of the head and neck presenting as oral and primary intraosseous squamous cell carcinomas.

Six cases of squamous cell carcinoma arising in the head and neck of patients infected with the human immunodeficiency virus are described. This article reports the first two cases of primary intraosseous squamous cell carcinoma associated with infection with human immunodeficiency virus. Clinical presentation, results of imaging studies, histologic characteristics, therapies applied, and the clinical follow-up are described in detail for each of the six cases. These data are evaluated through a review of the current literature.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Distribution of undulin, tenascin, and fibronectin in the human periodontal ligament and cementum: comparative immunoelectron microscopy with ultra-thin cryosections.

We studied the ultrastructural localization of three distantly related glycoproteins of the extracellular matrix, undulin, tenascin and fibronectin, in decalcified sections of human periodontal ligament (PL) and cementum. Undulin was associated with tightly packed major collagen fibrils and not with microfibrils, indicating that this protein may be involved in the supramolecular and functional organization of collagen fibrils into flexible bundles. Tenascin was found on globular masses between less densely packed collagen fibrils, thus displaying a pattern quite distinct from that of undulin. Fibronectin was noted in bulky material between the cross-striated fibrils, often surrounding individual fibrils like garlands, and in the microfibrillar meshwork extending from cross-striated fibrils. The three glycoproteins displayed a distinct and unique pattern of distribution in PL that can be correlated with their molecular structure and potential functions.

Adolescent↗
PubMed1992

Odontogenic lesions in opercula of permanent molars delayed in eruption.

Opercula of permanent first and second molars delayed in eruption were investigated histologically to detect possible causes of eruption failure. The material comprised operation specimens from exposure of 74 non-erupted molars in 63 young individuals (34 boys, 29 girls). Eighteen of the 74 specimens (or 24.3%) were diagnosed as "classical" odontogenic tumors belonging to the following entities: ameloblastic fibroma (seven), ameloblastic fibrodentinoma (six), ameloblastic fibro-odontoma (four) and complex odontoma (one). Twenty-two specimens (or 29.7%) showed a hitherto unrecognized odontogenic lesion of hamartomatous character, termed odontogenic giant cell fibromatosis (OGCF). Thus, 54.1% of the specimens could be diagnosed as odontogenic tumors or hamartomas. Histomorphologic changes could not be detected in the remaining 34 specimens (45.9%). Odontogenic tumors were associated with unerupted first molars much more frequently than with second molars (ratio 8:1). The OGCF had a strong association with unerupted mandibular molars. Further, opercula of mandibular first molars frequently revealed odontogenic lesions whereas tissue overlying the crown of unerupted maxillary second molars often was reported as normal operculum.

Adolescent↗
PubMed1992

Immunocytochemical detection of herpes viruses in oral smears of HIV-infected patients.

Cytologic smears (CS) were taken from the lateral border of the tongue of HIV-seropositive patients (HIV+) (n = 39) and of seronegative controls (HIV-) (n = 19) and examined by immunocytochemistry (APAAP) and in situ hybridization (ISH) (biotinylated DNA probes) for the presence of viral antigens/DNA of EBV and CMV. While none of the HIV controls showed positive results for EBV antigen, 61% (APAAP) resp. 79% (ISH) of oral epithelial cells in the group of HIV+ patients were EBV-positive. While all CS taken from areas with the clinical diagnosis of hairy leukoplakia (HL) were EBV positive (APAAP and/or ISH), the detection of EBV in CS from uninvolved oral mucosa seemed to be associated with the later development of HL. In the group of HIV+ patients the detection rate for CMV was about five times (APAAP) resp. three times (ISH) higher than in HIV- persons. This non-invasive technique seems to be a valuable tool to screen for viral antigens/genomes.

Adult↗
PubMed1992

Distribution of cytokeratins in oral cytological smears of HIV-infected patients.

Cytological smears (CS), taken from the lateral border of the tongue of HIV-seropositive patients (HIV+) (n = 34) and of seronegative controls (HIV-) (n = 16), were examined by means of immunocytochemistry (APAAP) for the distribution patterns of different cytokeratins and MHC class II antigens. Compared with HIV- patients in CS of HIV-infected patients cornification associated cytokeratins 10/11 were increased, while the number of keratinocytes positive for cytokeratins 13/16 was comparable in both groups. Expression of simple epithelial cytokeratins 19, rarely observed in CS of HIV- patients, was a frequent findings in CS of HIV+ patients. Keratinocytes positive for MHC class II antigens were observed in CS of 12/34 HIV+, while all control CS were negative. In the group of HIV+ patients no correlation was found between the clinical presence of HL and the expression of cytokeratins or class II antigens. The altered distribution of cytokeratins may reflect local responses to proliferative stimuli or local inflammation due to the presence of microbial antigens or may occur as a general unspecific reaction in the setting of systemic viral infection. This non-invasive technique seems to be a valuable tool to determine the proliferation rate of oral epithelial cells.

Adult↗
PubMed1991

Expression of proteins encoded by Epstein-Barr virus trans-activator genes depends on the differentiation of epithelial cells in oral hairy leukoplakia.

The Epstein-Barr virus (EBV) immediate early gene product BZLF1 was localized by indirect immunofluorescence to the cytoplasm of the basal epithelial layer at the lateral border and dorsum of tongue in human immunodeficiency virus-infected and -seronegative patients. Two biopsies of oral hairy leukoplakia revealed a sporadic cytoplasmic staining of the BHRF1 and BRLF1 gene products in the basal epithelial layer. The widespread presence of BZLF1 in the basal epithelial layer indicated that this cell layer contained EBV DNA and was probably directly infected by EBV. Nuclear localization of the immediate early and early gene products BZLF1, BHRF1, BRLF1, and BMLF1 was limited to oral hairy leukoplakia in human immunodeficiency virus-seropositive patients and revealed a codistribution with the virus capsid antigen. Our results indicate that the epithelium of the tongue is a potential reservoir for EBV and that in heavily immunocompromised patients EBV may move from the cytoplasm to the nucleus with increasing differentiation and be coactivated there during the terminal differentiation of epithelial cells at the lateral border and dorsum of tongue.

Cell Differentiation↗
PubMed1991

Immunoelectron microscopy shows an atypical pattern and a quantitative shift of collagens type I, III and VI in oral Kaposi's sarcoma of AIDS.

The localization of collagen types I, III and VI in normal human alveolar and palatal mucosa and in oral Kaposi's sarcoma (KS) was studied by light microscopy and cryo-immunoelectron microscopy. Normal oral mucosa revealed two different types of organization. The upper connective tissue stroma contained a loose reticular network mainly composed of collagen types III and VI, while collagen type I immunostaining predominated in the deeper stroma. Ultrastructurally, in the KS tumour stroma, a loose pattern of individual thin collagen fibrils was noted. These often fanned out at their ends showing a filamentous substructure. The fibrils consisted predominantly of collagen type I similar to individual fibrils of normal oral mucosa. However, there was a marked loss of thick fibre bundles of collagen types I and III in KS compared with normal oral mucosa, whereas collagen type VI was markedly increased and found preferentially in clusters and strands around cross-striated fibrils that often spanned the distance between single collagen fibres. The abundance of collagen type VI in a pattern similar to early stages of wound healing suggests that the KS stroma resembles an early organizational stage of the interstitial and vascular extracellular matrix subject to a high rate of collagen turnover. This character of the KS stroma appears to result from a continuous auto-and paracrine stimulation of cell growth and collagen synthesis and provides an excellent model to study the structural arrangement of collagen type VI in relation to the fibrillar collagen types I and III.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Oral manifestations of AIDS-associated non-Hodgkin's lymphomas.

While B-cell lymphomas are frequently found in AIDS patients, reports on oral manifestations are rare. Among a group of 465 HIV-infected patients 5 presented with primary oral manifestations of a malignant B-cell lymphoma. The primary site of manifestation was the maxilla in 3 cases and the mandible in 2 cases. Based on the histological and immunohistochemical examination the tumors were differentiated as Burkitt's lymphoma (n = 1), as anaplastic large cell (ALC) lymphoma of the B-cell type (n = 1), as high-grade non-Hodgkin's lymphoma not classifiable according to the Kiel classification (n = 1), as immunoblastic-plasmoblastic lymphoma (n = 1), and as centroblastic lymphoma (n = 1). Serum samples were negative for HTLV-I antibodies in 5/5 cases.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Primary intraosseous AIDS-associated Kaposi's sarcoma. Report of two cases with initial jaw involvement.

AIDS-associated Kaposi's sarcoma (KS), which in 80% of cases occurs in the oral cavity, usually presents with characteristic clinical features such as brown-bluish pigmented macules or tumorous lesions. In later stages the tumor, most probably originating from the vascular endothelium, may secondarily induce erosion of the underlying bone. The primary, intraosseous occurrence of KS has prompted the present 2 case reports. The tumor presented as extensive, diffuse osteolysis within the mandible without causing clinical symptoms. Although rare, intraosseous KS must be included in the differential diagnosis of isolated bone defects in HIV-infected patients.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Guided bone regeneration next to osseointegrated implants in humans.

The purpose of this investigation was to evaluate the technique of guided tissue regeneration on a clinical and histologic level for generating new bone adjacent to osseointegrated implants. Cylindrical, press-fitted, titanium plasma flame-coated implants were modified by a disk screwed onto the implant. After implant insertion, the disk-implant assembly was covered by an expanded polytetrafluorethylene membrane. In one group, the space underneath the membrane was filled with hydroxylapatite granules; in the control group, no membrane was used. Clinical and histologic results demonstrate that the principle of guided tissue regeneration is applicable to osteogenesis in humans.

Adult↗
PubMed1990

Cytomegalovirus associated oral ulcerations in HIV-infected patients.

Oral ulcerations associated with disseminated cytomegalovirus (CMV) infection were observed in four patients with AIDS manifestations showing low CD4 counts. Virus cultures of urine and saliva samples were positive for CMV in all cases. The lesions were characterized by a punched-out appearance, non-indurated borders, low bleeding tendency and lack of inflammatory wall. Light microscopy revealed granulation tissue containing "owl's eye" like cells in all specimens. Presence of CMV was confirmed by immunohistochemistry and in situ hybridization. The ulcerations were infiltrated with T-lymphocytes of the helper, suppressor and cytotoxic subset, most were positive for HLA DR. Despite the local invasion with immunocytes and high serum titers of serum antibodies the patients experienced progressive CMV disease.

Adult↗