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G Seifert

Publications and source records attributed to G Seifert.

At least 73 records · Page 4Linked to original sources
PubMed1996

Classification and differential diagnosis of clear and basal cell tumors of the salivary glands.

Several cell types of the salivary glands and their neoplasms may have a clear cytoplasm. Classification of their cytological features is made possible with special stainings, immunohistochemistry, and electron microscopy. Clear cell tumors of the salivary glands are usually formed by one distinctive cytological type. A new but distinct and very rare salivary gland neoplasm is the hyalinizing clear cell carcinoma, which should be differentiated from other clear cell salivary tumors. Salivary gland tumors with predominance of a basal cell component are basal cell adenoma, basal cell adenocarcinoma, and the solid type of adenoid cystic carcinoma. The differential diagnosis of clear cell and basal cell tumors is of great importance for the prognosis and treatment of these tumors.

Adenocarcinoma↗
PubMed1995

Glial cells in the mouse hippocampus express AMPA receptors with an intermediate Ca2+ permeability.

Recently, we could demonstrate the 'complex' glial cells in mouse hippocampal slices express glutamate receptor changes of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate subtypes. In the present study, we further characterized this glial receptor. Since voltage-clamp control is imperfect and diffusion barriers hinders the quantitative analysis of the receptor currents in situ, the patch-clamp technique was applied to glial cells acutely isolated from the mouse hippocampal CA1 stratum radiatum subregion. A concentration-clamp technique was used which enabled very fast exchange of the extracellular solutions. Thus, it was possible to characterize the transient receptor currents with high time resolution. Application of L-glutamate, AMPA and L-homocysteate induced rapidly activating and fast desensitizing receptor currents in the suspended glial cells. In contrast, kainate induced non-desensitizing currents. The corresponding dose-response curve revealed a half-maximum of current activation at 350 microM. The current/voltage relationship of the kainate-evoked response was linear with a reversal potential at approximately 9 mV. Analysis of the reversal potential in solutions containing high concentrations of CaCl2 confirmed earlier in situ data by demonstrating significant Ca2+ permeability of the glial glutamate receptor channels in the hippocampus. The kainate-induced receptor currents were markedly increased by cyclothiazide, a substance which selectively potentiates glutamate receptors of the AMPA subtype. We conclude that glial cells of the juvenile hippocampus mainly express heteromeric high-affinity AMPA receptors. Most probably, the receptor channels are assembled from the low Ca(2+)-permeable glutamate receptor-2 subunit together with Ca(2+)-permeable AMPA-preferring subunits.

Animals↗
PubMed1995

Developmental regulation of Na+ and K+ conductances in glial cells of mouse hippocampal brain slices.

The relative contribution of voltage activated Na+ and K+ currents to the whole cell current pattern of hippocampal glial cells was analyzed and compared during different stages of postnatal maturation. The patch-clamp technique was applied to identified cells in thin brain slices obtained from animals between postnatal day 5 and 35 (p5-35). We focused on a subpopulation of glial cells in the CA1 stratum radiatum which most probably represents a pool of immature astrocytes, termed "complex" cells. These cells could not be labelled by O1/O4 antibodies, but some of the older cells were positively stained for glial fibrillary acidic protein (GFAP). In the early postnatal days, the current pattern of the "complex" cells was dominated by two types of K+ outward currents: a delayed rectifier and a transient component. In addition, all cells expressed significant tetrodotoxin (TTX)-sensitive Na+ currents. During maturation, the contribution of delayed rectifier and A-type currents significantly decreased. Furthermore, almost all cells after p20 lacked Na+ currents. This down-regulation of voltage gated Na+ and K+ outward currents was accompanied by a substantial increase in passive and inward rectifier K+ conductances. We found increasing evidence of electrical coupling between the "complex" cells with continued development. It is concluded that these developmental changes in the electrophysiological properties of "complex" glial cells could be jointly responsible for the well known impaired K+ homeostasis in the early postnatal hippocampus.

Animals↗
PubMed1995

[Etiology and differential diagnosis of sialadenitis].

The salivary glands are integrated into the body in such a complex manner that the analysis of the saliva allows conclusions about pathological function of other organ systems. Such interactions between salivary glands and the body as a whole play an important role in the etiology and pathogenesis of the different types of sialadenitis. An etiological classification is a proven method for arriving at a clinical diagnosis. Etiological factors include traumas, bacteria, viruses, ductal obstructions, disturbances of secretion, radiogenic damage, and immunological reactions (immunocomplex, tuberculin, or autoimmune types). Frequently the etiology is influenced by several factors. After a brief discussion of the clinical diagnostic methods, we present the clinical and morphological findings concerning the various types of sialadenitis and their differential diagnosis.

Diagnosis, Differential↗
PubMed1994

Properties of voltage-activated Na+ and K+ currents in mouse hippocampal glial cells in situ and after acute isolation from tissue slices.

In the present study, we were interested in a quantitative analysis of voltage-activated channels in a subpopulation of hippocampal glial cells, termed "complex" cells. The patch-clamp technique in the whole-cell mode was applied to identified cells in situ and to glial cells acutely isolated from tissue slices. The outward current was composed of two components: a sustained and a transient current. The transient K+ channel had electrophysiological and pharmacological properties resembling those of the channel through which the A-currents pass. In addition, this glial A-type current possessed a significant Ca2+ dependence. The current parameters determined in situ or in isolated cells corresponded well. Due to space clamp problems in situ, properties of voltage-dependent Na+ currents were only analysed in suspended glial cells. The tetrodotoxin (TTX) sensitivity and the stationary and kinetic characteristics of this current were similar to corresponding properties of hippocampal neurons. These quantitative data demonstrate that at an early postnatal stage of central nervous system maturation, glial cells in situ express a complex pattern of voltage-gated ion channels. The results are compared to findings in other preparations and the possible consequences of transmitter-mediated channel modulation in glial cells are discussed.

Animals↗
PubMed1994

A panel of monoclonal antibodies to rat plectin: distinction by epitope mapping and immunoreactivity with different tissues and cell lines.

A panel of twelve monoclonal antibodies (mAbs) to plectin was analyzed to localize molecular epitopes and assess their utility for various immunotechniques. Based on staining patterns obtained by immunoblotting of proteolytic plectin fragments five groups of mAbs with spatially closely linked epitopes were distinguished. In combination with previous results obtained with recombinant mutant proteins, the epitopes of all mAbs could be shown to reside within three separated domains of plectin's rod domain. Immunoblot analyses of several different rat tissues and a number of cultured cell lines derived from various species, including rat, hamster, cow, mouse and man, revealed considerable variations in immunoreactivity of antibodies. Differences in mAb immunoreactivities were also revealed by immunofluorescence microscopy of different tissues and cultured cell lines. One third of the mAbs examined produced staining patterns that were indistinguishable from those generated by conventional rabbit antisera, confirming the widespread and highly divers cellular localization of plectin previously reported. Microinjection of several monoclonal antibodies into Rat 1 cells had no detectable effects on the structure and organization of plectin arrays or of other cytoskeletal filaments. This new collection of mAbs provides a more reliable tool for histological studies than previously available antisera and should be useful for studies of tissue and cell type specific functions of plectin domains in vivo and in vitro.

Animals↗
PubMed1993

Histological re-evaluation of 101 intraoral salivary gland tumors by an EORTC-study group.

Tumors of the salivary glands constitute a heterogeneous group of lesions of great morphologic variation and for this reason present many difficulties in histologic classification. The histologic slides of 101 consecutive intraoral salivary gland tumors of the Department of Oral Pathology of the Free University in Amsterdam were reviewed, retrospectively, by an EORTC-study group on salivary gland tumors. Complete concurrence of diagnosis was reached in 54 cases. In 33 cases there were minor disagreements, mostly related to subclassification. Major disagreements, relating to benign versus malignant, occurred in eight cases (7.9 per cent).

Female↗
PubMed1992

The World Health Organization's Histological Classification of Salivary Gland Tumors. A commentary on the second edition.

The second edition of the World Health Organization's Histological Classification of Salivary Gland Tumors is more extensive and detailed than the previous edition published 20 years ago. The new edition is based on data regarding newly described tumor entities and the behavior and prognosis of the previously classified tumors. The distinct morphologic features of monomorphic adenomas justify their separation for purposes of identification. Among the carcinomas, various types were distinguished for purposes of recognition, prognosis, and treatment. The term tumor was replaced by carcinoma in the following two entities: acinic cell carcinoma and mucoepidermoid carcinoma. The tumor-like lesions were described in more detail.

Adenoma↗
PubMed1992

Histopathology of malignant salivary gland tumours.

This report is based upon the Salivary Gland Register in Hamburg and on the second revised edition of the WHO Histological Typing of Salivary Gland Tumours. The group of malignant salivary gland tumours contains carcinomas, malignant non-epithelial tumours, malignant lymphomas and secondary tumours. The various carcinomas are classified in a continuous separate listing because the different types are distinguished not only by histopathology, but also by differences in prognosis and treatment. The term "tumour" is replaced by "carcinoma" in two entities: acinic cell carcinoma and mucoepidermoid carcinoma. New entities are: polymorphous low-grade adenocarcinoma, basal cell adenocarcinoma, salivary duct carcinoma and malignant myoepithelioma. Carcinoma in pleomorphic adenoma can be distinguished as non-invasive and invasive carcinoma, and carcinosarcoma. Malignant non-epithelial tumours are mostly malignant fibrous histiocytoma, malignant schwannoma and rhabdomyosarcoma. The large majority of malignant lymphomas are non-Hodgkin-lymphomas with high differentiation. Many lymphomas are associated with chronic immunosialadenitis (Sjögren's syndrome). Secondary tumours are mostly metastases from primary squamous cell carcinomas or from melanomas of the skin (head and neck area). Haematogeneous metastases are very rare (mainly from lung, kidney or breast).

Adenocarcinoma↗
PubMed1992

Tumour-like lesions of the salivary glands. The new WHO classification.

Tumour-like lesions must be distinguished from true tumours of the salivary glands. In the new WHO classification of salivary gland tumours seven entities were considered: sialadenosis, oncocytosis (diffuse oncocytosis and focal adenomatous oncocytic hyperplasia), necrotizing sialometaplasia (salivary gland infarction), benign lymphoepithelial lesion (chronic myoepithelial sialadenitis), salivary duct cysts (mucoceles of the minor salivary glands of extravasation or retention type, cysts of the major salivary glands, ranula and dysgenetic polycystic disease of the parotid gland), chronic sclerosing sialadenitis of the submandibular gland (Küttner tumour), and cystic lymphoid hyperplasia in AIDS. The main topics of clinical data and pathohistology were described and documented by the results of the Salivary Gland Register in Hamburg (1965-1989).

Acquired Immunodeficiency Syndrome↗
PubMed1990

[Systemic lysotherapy using recombinant tissue plasminogen activator for fulminant pulmonary embolism].

A 44-year-old woman sustained massive pulmonary embolization from a deep leg-vein thrombosis. She was given 70 mg recombinant tissue plasminogen activator (rt-PA) by continuous intravenous drip over two hours. Before this treatment perfusion scintigraphy had demonstrated complete absence of flow in the right lung due to embolic occlusion of the central hilar vessels. In addition there were several segmental filling defects in the left lung. Even during the two-hour infusion the circulatory state began to improve, as did echo- and electrocardiographic signs of acute right heart strain. Correspondingly there was a rapid raise in arterial pO2. Another scintigraphy after 48 hours revealed almost complete reperfusion of the right lung and the left lung segments. This case demonstrates that infusion of rt-PA can be an effective and relatively risk-free method of treating haemodynamically significant massive lung embolism, even in comparison with selective or systemic thrombolysis with urokinase or streptase or with surgical embolectomy.

Adult↗