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Biomedical subjects

P Schenk

Publications and source records attributed to P Schenk.

At least 55 records · Page 3Linked to original sources
PubMed1992

Infrared laser tissue ablation: holmium:YAG laser surgery.

The in vivo tissue ablation characteristics of a pulsed holmium:YAG laser (lambda = 1,980 nm) were studied. The laser energy was coupled onto nylon fibers 400 and 600 microns in core diameter. Laser incisions were made on white rats at different sites of the tongue and of the mucous membranes of the oral cavity. Power settings of 500 and 1,000 mJ/2.5-ms pulse at 5 pulses/s were used and the tissue responses examined by light microscopy. Wound healing was studied over a 6-week period. The results of this study are promising for future application of the holmium:YAG laser in otorhinolaryngology.

Animals↗
PubMed1992

[Holmium:YAG laser surgery. Possibilities for use in inflammatory paranasal sinus diseases].

A pulsed Holmium: YAG laser (lambda = 2120 nm) was used during functional endoscopic endonasal surgery in ten patients with recurrent chronic inflammation of the paranasal sinuses. The Holmium: YAG laser energy was coupled to a 600 microns core diameter nylon fiber. Power settings of 950 mJ per 2.5 microseconds pulse at 5 pulses per second were used. Tissue responses to treatment were examined by light microscopy. The photoablative mechanism of the laser-tissue interaction led to bone and soft tissue ablation with only a minor thermal component in the target zone. In comparison with other laser types available clinically, there was no carbonization zone after use of the Holmium-YAG laser. The area of tissue damage produced was significantly smaller (370-520 microns only) and wound healing proceeded without complication. The physical settings of the laser equipment are described with regard to their significance in photoablation when using flexible light-conducting fibers. The possible role of the Holmium: YAG laser in clinical surgery is discussed on the basis of the present experience.

Adult↗
PubMed1991

Merkel cell carcinoma of the head and neck associated with Bowen's disease.

The Merkel cell carcinoma occurs primarily in the skin of the head and neck, and develops in the dermis with a trabecular growth pattern. Immunohistochemistry reveals positive staining for neuron-specific enolase, neurofilaments, cytokeratin and chromogranin A. Electron microscopically, the tumor cells contain dense-core granules, spinous cytoplasmic processes, desmosomes, zonulae adherentes and paranuclear filament aggregates besides frequent mitoses, focal necroses and lymphocyte and plasma cell infiltrates. The Merkel cell carcinoma is often co-existent with other malignancies such as squamous cell carcinoma or, as in the present study, with Bowen's disease. The definite diagnosis of the Merkel cell carcinoma can be effected only by electron microscopic examination of the tumor.

Aged↗
PubMed1991

Infrared laser stapedotomy.

A pulsed holmium: YAG laser (lambda = 1980 nm) was used to perform 0.4 mm stapedotomy fenestrations in human stapes footplates from freshly dissected cadavers under simulated surgical conditions. The energy was coupled into a 400 microns core diameter nylon fiber. Thermal gradients were then measured following laser applications and tissue responses examined by light microscopy. The results of this study suggest the feasibility of using a surgical holmium: YAG laser in middle ear surgery.

Humans↗
PubMed1991

The 45-kilodalton protein of cytomegalovirus (Colburn) B-capsids is an amino-terminal extension form of the assembly protein.

Intranuclear B-capsids from cytomegalovirus (strain Colburn)-infected cells contain an abundant 37-kDa assembly protein, thought to be involved in capsid formation, and three minor protein constituents (i.e., 45, 39, and 38 kDa) that are immunologically and structurally related to the assembly protein. In the experiments reported here, antisera produced against synthetic peptides were used in conjunction with chemical protein cleavage to examine the structural relationship of these proteins in more detail. Results of these experiments verify that the carboxyl end of the 39-kDa assembly protein precursor is lost during maturation and suggest that the 38-kDa protein may be a processing intermediate. It is shown that the 45-kDa protein is coterminal with the mature assembly protein at its carboxyl end but differs by a predicted 115-amino-acid extension at its amino terminus. In addition, evidence is presented that the 45-kDa protein has a 48-kDa precursor and a 47-kDa putative processing intermediate which have the same carboxy-terminal sequences and undergo the same maturational events as those of the assembly protein. A working model considering the structural relationship of these proteins is presented.

Amino Acid Sequence↗
PubMed1990

Differential repair of UV damage in rad mutants of Saccharomyces cerevisiae: a possible function of G2 arrest upon UV irradiation.

After UV irradiation, the transcriptionally active MAT alpha locus in Saccharomyces cerevisiae is preferentially repaired compared with the inactive HML alpha locus. The effect of rad mutations from three different epistasis groups on differential repair was investigated. Three mutants, rad9, rad16, and rad24, were impaired in the removal of UV dimers from the inactive HML alpha locus, whereas they had generally normal repair of the active MAT alpha locus. Since RAD9 is necessary for G2 arrest after UV irradiation, we propose that the G2 stage plays a role in making the dimers accessible for repair, at least in the repressed HML alpha locus.

Blotting, Southern↗
PubMed1990

Studies on sucrose-palmitate-stearate-containing vesicles encapsulating the cytostatic drug methylglyoxal-bis-guanyl-hydrazone.

Vesicles prepared from sucrose-palmitate-stearate and cholesterol encapsulating the anticancer drug methylglyoxal-bis-guanylhydrazone, were investigated. Treatment with drug-loaded vesicles of this composition in a q.d. 1-4 schedule resulted for murine leukemias P388 in nearly the same increase in life span as the corresponding dose of the free drug. Even very high dosages of sucrose-palmitase-stearate (up to 480 mg.kg-1.d-1) were tolerated by mice.

Animals↗
PubMed1989

[Schwannoma of the nose and paranasal sinuses].

A rare case of a Schwannoma (neurinoma) of the frontal sinus of a 75-year old male patient was examined clinically, histologically, and by electron microscopy. The fine structure of neurinomas occurs in two forms: Type Antoni A is composed of Schwann cells whose nuclei are arranged in palisading rows with greatly attenuated cytoplasmic processes extending from the Schwann cells in parallel alignment; Antoni B is characterized by loosely arranged Schwann cells set in meshwork of macrocysts and reticular fibers. It may be a degenerative form of Antoni A. In the present case Antoni A was the dominating pattern. A prominent basal lamina enveloping Schwann cells, as well as desmosome-like junctions between them, were identified. Furthermore, myelin figures, lysosomal bodies, intranuclear unmyelinated axons and concentric laminated inclusions, and annulate lamellae were found in Schwann cells. Luse bodies appeared in the tumour matrix. It is suggested that annulate lamellae may play a significant role in cell differentiation and tumour growth. No other ultrastructural signs of malignancy were seen.

Aged↗
PubMed1989

[Hyalinosis cutis et mucosae of the ear-nose-throat].

Hyalinosis cutis et mucosae (HCM) is a rare autosomal recessive disease of unknown aetiology and pathogenesis. In the skin and mucous membranes there is characteristically a deposition of hyaline-like material in the papillary dermis, around the small blood vessels and around skin appendages. Besides the manifold skin lesions, the mucous membranes affected are found in the nasal and oral cavities, pharynx and larynx. The latter causes the most characteristic symptom, namely, hoarseness, from birth. The lesions of the vessel walls are the most significant histopathological alterations. Ultrastructurally, massive deposits of amorphous, hyaline-like material in the dermis, reduction in number and size of the collagen fibrils and, finally, thickening of the basal laminae could be observed. The findings suggest an abnormal production of noncollagenous proteins as well as the alteration of the lysosomal systems of fibroblasts, endothelial cells and pericytes in the pathogenesis of hyalinosis.

Adult↗
PubMed1989

Mapping of epitopes on the 65k DNA-binding protein of herpes simplex virus type 1.

Previously we have described the isolation of seven monoclonal antibodies (MAbs) and two polyvalent rabbit sera directed against the product of herpes simplex virus type 1 (HSV-1) gene UL42, a 65K DNA-binding protein (65KDBP) which is essential for HSV DNA replication and virus growth. We now report the synthesis of all 483 overlapping hexapeptides of this 488 amino acid protein and describe their use for the identification of epitopes recognized by these MAbs and polyvalent sera. MAb 6898, derived from one fusion, recognizes the peptides EDLDGA and DLDGAA which correspond to amino acids 363 to 369 of 65KDBP. MAbs Z4D4, Z6F3, Z1A8, Z10Cl, Z3H12 and Z1F11, derived from a second fusion, all recognize the peptides GDPEDL and DPEDLD which correspond to amino acids 360 to 366. As expected both polyvalent sera recognize several different epitopes.

Amino Acid Sequence↗
PubMed1988

[Initial clinical experiences in a large Austrian patient sample with immunodeficiency syndrome (AIDS): I. Type and course of encountered infections].

This study presents a report on the first clinical experiences gained in 68 hospitalized HIV antibody-positive patients from Austria, covering a period of twelve months. 36 patients (52.9%) belonged to risk group I or Ib (homo- or bisexual), whereas 26 (38.2%) patients were i.v. drug abusers (risk group II). 5 (7.4%) patients fulfilled the criteria of stage II of the CDC classification of HIV-associated clinical symptoms, 10 (14.7%) were classified as stage III and the remaining 53 patients (78%) as stage IV. The most frequent and also the most serious problem was the development of opportunistic infections. Multiple infections were found in 45.7% of all cases. Kaposi's sarcoma was found in 9 patients who all belonged to risk group I. During the entire observation period 10 patients died as a consequence of HIV-1-induced immunodeficiency and the resulting opportunistic infections and/or neoplasms.

Acquired Immunodeficiency Syndrome↗
PubMed1988

The 65 K DNA binding protein appears early in HSV-1 replication.

During the infection cycle of herpes simplex virus polypeptides appear as immediate early, early and late proteins. We classified the 65 K DNA binding protein as an early (beta-) protein by comparing its detectibility with that of two well defined proteins the ICP 4 (known as immediate early protein) and the ICP 8 (known as early protein).

Animals↗
PubMed1988

Monoclonal antibodies against herpes simplex virus type 1-infected nuclei defining and localizing the ICP8 protein, 65K DNA-binding protein and polypeptides of the ICP35 family.

The production and properties of monoclonal antibodies raised against herpes simplex virus type 1 (HSV-1)-infected cell nuclei are described. Biological and immunochemical assays revealed that these antibodies recognize four different proteins in HSV-1-infected cells. Four antibodies reacted with the major DNA-binding protein (ICP8) and six with the 65K DNA-binding protein. Two antibodies detected the ICP35 family of proteins and one antibody bound to a protein with an apparent mol. wt. of 60K. Immune electron microscopy showed that the major DNA-binding protein had a patchy distribution, whereas the 65K DNA-binding protein was evenly spread in the infected cell nuclei. The 60K protein as well as the polypeptides of the ICP35 family were preferentially found associated with the viral capsid.

Animals↗
PubMed1988

Langerhans' cells are an actual site of HIV-1 replication.

Human epidermal Langerhans' cells (LC) are HLA-DR+/DQ+, CD1+, CD4+ dendritic antigen-presenting leukocytes. Based on the observation that in certain human immunodeficiency virus type 1 (HIV-1) infected individuals, LC are the only epidermal cells to react with monoclonal antibodies against HIV-1 isolate termed human T-lymphotropic virus IIIB/83 core proteins p17 and p24, we have proposed that LC can serve as a target for HIV-1. This contention was strengthened by the ultrastructural finding of HIV-1-like particles in the close proximity of LC and by the demonstration of signs of moderate to severe LC damage. Detailed electron microscopic analysis of skin and mucosal biopsies from an AIDS patient with p17/p24-positive LC now revealed not only mature HIV-1-like virions in the extracellular space surrounding LC and in intracytoplasmic LC vacuoles, but also developmental forms of HIV-1-like particles budding from LC surface membranes. Using peripheral blood derived monocytes/macrophages as targets for HIV-1 isolation, a virus isolate, designated human T-lymphotropic virus III WR-SK/86, was recovered from skin tissue from this patient by cocultivation and identified as unique by nucleic acid hybridization analysis. These findings now conclusively show that HIV-1 replicates in and is released from LC and support the concept that antigen-presenting cells (mononuclear phagocytes, LC) can serve as a reservoir for the acquired immunodeficiency syndrome virus.

AIDS-Related Complex↗
PubMed1988

[Acquired epidermolysis bullosa. A clinico-pathologic study].

Epidermolysis bullosa acquisita is an immunologically mediated mechano-bullous dermatosis presenting with a variety of clinical appearances. In mild cases the skin lesions, serous blisters, erosions and scars are restricted to the extremities. Scarring alopecia, dystrophy and even loss of nails as well as extensive erosions of mucous membranes may complicate severe cases. The characteristic histopathological feature is a subepidermal blister, which is located within the dermis by electron microscopy. Linear deposits of IgG and C3 along the basement membrane zone have been found on the dermal side of the lamina densa by immunoelectron microscopy. This close anatomical relationship with anchoring fibrils strongly suggests a functional disturbance of these anatomical structures, leading to dermolytic blistering. Treatment with sulphones, in combination with cortico-steroids in the more severe cases, has resulted in long-term improvement in two of our three patients.

Adult↗