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Biomedical subjects

K Weber

Publications and source records attributed to K Weber.

At least 505 records · Page 28Linked to original sources
PubMed1983

Heavy ion action on yeast cells: inhibition of ribosomal-RNA synthesis, loss of colony forming ability and induction of mutants.

The action of heavy ions (Ar to U) accelerated to specific energies up to about 10 MeV/u (u=atomic mass unit) on different functions of yeast cells was studied. Ribosomal-RNA synthesis is inhibited according to a single-hit mechanism. Inactivation cross-sections were linearly related to the ratio of the squares of the effective charge Z* and the velocity of the ions. It is concluded from the analysis that the range of the most energetic delta-electrons is larger than previously assumed. There is no such dependence for survival and induction of mutants. In both cases cross-sections increase with the ion's specific-energy indicating an important contribution of long-range delta-electrons. The analysis shows that diploid yeast is not killed by a single-hit mechanism even by very heavy ions if the track width is too small. The relative importance of the penumbral region is even more pronounced with the more sensitive strains.

Argon↗
PubMed1983

Localization of vasoactive intestinal polypeptide in penile erectile tissue and in the major pelvic ganglion of the rat.

Vasoactive intestinal polypeptide was localized by immunocytochemical techniques in the major pelvic ganglion and penile erectile tissue of the rat. Vasoactive intestinal polypeptide fibers were concentrated in penile crura with the density of innervation decreasing distally. The helicine arteries were very densely innervated while fewer fibers surrounded the deep artery of the penis. Intrinsic smooth muscle of the cavernous bodies received a moderate supply of vasoactive intestinal polypeptide immunoreactive fibers. Dorsal vascular structures, including the deep dorsal vein were innervated by vasoactive intestinal polypeptide fibers. Vasoactive intestinal polypeptide immunoreactive cell bodies were found in the major pelvic ganglion, concentrated on one end of the ganglion. Retrograde studies with a dye injected into the penile crura indicated that neurons in major pelvic ganglion projected to the penis. Combined dye and immunofluorescent studies showed that all the dye-labeled neurons were immunoreactive for vasoactive intestinal polypeptide. It is concluded that all vascular beds in the penis of the rat are innervated by vasoactive intestinal polypeptide fibers and that the extent of the innervation is related to the occurrence of smooth muscle. Neurons in the major pelvic ganglion probably are the main source of vasoactive intestinal polypeptide fibers to the penis.

Animals↗
PubMed1983

Cytoplasmic actin patterns in Physarum as revealed by NBD-phallacidin staining.

Fluorescently labeled phallacidin, a F-actin specific drug, was used to demonstrate the morphological variety in the cytoskeletal actin pattern of thin-spread plasmodia of the acellular slime mould Physarum polycephalum. The patterns observed in phallacidin-stained specimens consisted of a polygonal network in the anterior region, and of longitudinal as well as helically twisted fibrils in plasmodial strands of the posterior region. These observations are in complete accordance with our recent results obtained on comparable plasmodia by immunofluorescence microscopy using specific antibodies against actin.

Actins↗
PubMed1983

The spectrin-related molecule, TW-260/240, cross-links the actin bundles of the microvillus rootlets in the brush borders of intestinal epithelial cells.

Previous studies have shown that molecules related to erythrocyte spectrin are present in the cortical cytoplasm of nonerythroid cells. We report here the localization by immunoelectron microscopy of one such molecule, TW-260/240, in the brush border of intestinal epithelial cells. Using highly specific antibodies against TW-260 and TW-240 as well as antibodies against fodrin, another spectrinlike molecule, we have found that the TW-260/240 molecules are displayed between rootlets at all levels of the terminal web. Occasionally, extended structures appear labeled suggestive of the fine filaments known to cross-link actin bundles. These results are in line with previous in vitro studies showing that TW-260/240 binds to, and cross-links, actin filaments. The results are discussed in terms of a model in which rootlets are immobilized in the terminal web in a matrix of TW-260/240.

Actins↗
PubMed1983

Intermediate filaments of the vimentin and prekeratin type in human epidermis.

Monospecific antibodies to intermediate filaments of mesenchymally derived vimentin, applied to frozen sections of human skin, specifically stained dendritic basal and suprabasal cells. Cellular morphology, distribution, reaction pattern with anti-HLA-DR in serial sections, and OKT6 in double-staining procedures identified these cells as melanocytes and Langerhans cells. As shown previously in animals keratinocytes stained with antiprekeratin exclusively. Thus, vimentin is an intracellular marker for Langerhans cells and melanocytes, differentiating them from keratinocytes.

Cytoskeleton↗
PubMed1983

Monoclonal antibodies specific for glial fibrillary acidic (GFA) protein and for each of the neurofilament triplet polypeptides.

A panel of 10 mouse monoclonal antibodies specific for glial fibrillary acidic protein (GFA) has been isolated using porcine GFA as antigen. Although all antibodies recognize GFA purified from porcine spinal cord in the western blot technique, they can be subdivided into at least three groups on the basis of their reactivity against defined fragments of the molecule. Immunofluorescence staining patterns with the monoclonal antibodies performed on tissues and cell lines resemble those reported with conventional polyclonal antibodies directed against GFA. In particular astrocytes and Bergmann glia are strongly stained. In addition mouse monoclonal antibodies specific for either the 200 kd, or the 160 kd, or the 68 kd neurofilament triplet protein have been isolated and characterized. These antibodies are specific for neuronal cells and support conclusions made with similar antigen affinity-purified polyclonal antibodies. The combined set of monoclonal antibodies seems a valuable tool to characterize the different cell types of the nervous system.

Animals↗
PubMed1983

Immunocytochemistry of the acellular slime mould Physarum polycephalum. I. Preparation, morphology, and reliability of results concerning cytoplasmic actomyosin patterns in sandwiched plasmodia.

Small phaneroplasmodia of Physarum polycephalum migrate, under sandwich conditions between two agar sheets and a membrane of cellophane, as thin protoplasmic sheets. This method suitably simulates the situation in the natural habitat of acellular slime moulds; i.e. the narrow clefts of the forest soil. The highly differentiated system of cytoplasmic fibrils displayed under these conditions survives both long-term extraction with glycerol and fixation with methanol, procedures that remove the strong inherent autofluorescence, thus allowing the use of immunocytochemical studies. The complicated fibrillar system of sandwiched plasmodia consists of: (1) a membrane-associated cortical filament layer in the anterior region; (2) a more or less regular polygonal fibrillar network in the intermediate region; and (3) a helically twisted fibrillar system encircling endoplasmic pathways as well as isolated strands in the posterior region. So far, three different cytoskeletal proteins have been identified immunocytochemically as constituents of the fibrillar structures: actin, myosin and AM-protein (fragmin). No positive identification of alpha-actinin, filamin and tropomyosin was obtained using antibodies against vertebrate proteins. Electron microscopy of glycerol-extracted specimens treated with antibodies against actin and myosin revealed that the 6 nm filaments consist of actin, whereas the electron-dense material between single actin filaments appears to be myosin. The AM-protein modulating the polymer status of actin is located in all fibrillar structures.

Actins↗
PubMed1983

The structure and development of the rat retina: an immunofluorescence microscopical study using antibodies specific for intermediate filament proteins.

Rat retina structure was studied between embryonic day 14 and adult with antibodies specific for vimentin, glial fibrillary acidic protein (GFA) and the proteins of the neurofilament triplet. Vimentin could be detected in radial processes throughout the retina at all stages studied. These processes are believed to correspond, in the developing retina, to ventriculocytes, and in the mature retina to Müller cells. They could not normally be stained with any of the other intermediate filament antibodies employed here. We did find, however, that some older albino rats possessed GFA staining in addition to vimentin in these processes. Since we never saw such staining in the retinae of mature non-albino rats, and the retinae of older albino rats often showed signs of degeneration, we concluded that such GFA expression was most likely pathological. Neurofilament protein-positive processes were first detectable at embryonic day 15 1/2 in the inner regions of the retina, and corresponded to the axons of retinal ganglion cells. Such processes were equivalently displayed with antibodies to 68 K and 145 K protein, but were negative with 200 K protein. Some 68 K and 145 K positive fibers could also be decorated with vimentin antibody at this stage, though at later stages this was not the case. At later development stages more 68 K and 145 K neurofilament positive processes appeared, and after the first post-natal week progressively more of such processes became in addition 200 K positive, so that almost all neurofilament positive fibers in the adult stained for all three proteins. Such fibers, in the mature retina corresponded to 68 K and 145 K positive optic nerve fibers, and the processes of neurones in the inner plexiform layer. All fibers in the mature optic nerve fiber layer, but not all of those in the inner plexiform layer were stainable with 200 K antibodies. At 4 days post-natal we were able to detect 68 K and 145 K protein positive profiles in the outer regions of the developing retina, the prospective outer plexiform layer. Such profiles were always in addition vimentin positive, but negative for 200 K protein. During further development such profiles became ordered into a well defined layer and from about post-natal day 13 all of them began to acquire 200 K protein. They could be identified as the processes of horizontal cells. They continued to express vimentin in addition to the three triplet proteins in the adult, a so far unprecedented situation. We were able to detect neurofilament staining in the mature retina only in the above described regions, the inner and outer nuclear layer and the photoreceptor processes being completely free of staining. GFA was first detected in short processes adjacent to the inner limiting membrane which penetrated the optic nerve fiber layer. Such profiles were first detectable in the eye of the newborn animal, and were invariably identically stainable with vimentin at this age. These profiles could be stained with both vimentin and GFA at all later stages examined, although GFA staining became very much stronger than vimentin staining in some profiles in the adult. The results presented here are discussed in terms of development of the different retinal cell types.

Age Factors↗
PubMed1983

Tumor diagnosis by intermediate filament typing: a novel tool for surgical pathology.

In most cell types intermediate or 10-mm filaments (IF) are a major cytoskeletal organization and, thus, directly or indirectly influence the structural appearance of the cytoplasm. In line with the cell type-specific expression patterns of different IF proteins in normal animal and human tissue, IF typing distinguishes the major tumor groups, as documented by results with several hundred human tumors classified by conventional histologic methods. Carcinomas are characterized by cytokeratins, sarcomas of muscle cells by desmin, nonmuscle sarcomas by vimentin, and gliomas by glial fibrillary acidic protein. Furthermore, certain tumors originating from the sympathetic nervous system, e.g., ganglioneuroblastoma, pheochromocytoma, and at least some neuroblastomas, are characterized by the presence of neurofilaments. Carcinomas can often be further subdivided with regard to their possible derivation by examining their cytokeratin profiles. The IF type characteristic of the cell of origin seems to be kept not only in the primary tumor but usually also in solid metastases. In general, tumors do not acquire additional IF types. Therefore, IF typing can provide an unambiguous and rapid characterization in certain cases, that are difficult to diagnose by conventional techniques. Some useful examples are the small cell tumors of childhood and the discrimination between undifferentiated carcinoma and lymphoma. IF typing of a few tumors has already led to a revision or reconsideration of the original light microscopic diagnosis. The combined results indicate that at least certain carcinomas, as well as certain other tumor types, seem to arise by the selective multiplication of a particular and identifiable cell type present in the normal tissue. The procedure is not restricted to tumor material. IF typing of Mallory bodies, Alzheimer's disease tangles, certain myopathies, and the cells of the amniotic fluid offers further interesting applications. Thus, IF typing should become a valuable new tool both in histology and surgical pathology.

Amniotic Fluid↗
PubMed1983

Pinocytosis and locomotion of amoebae. XIX. Immunocytochemical demonstration of actin and myosin in Amoeba proteus.

The spatial distribution of cytoplasmic actin and myosin in 1. normal locomoting, 2. immobilized, and 3. pinocytosing Amoeba proteus was demonstrated by indirect immunofluorescence microscopy. In orthotactic and polytactic cells fixed during normal locomotion actin is mainly located in a cortical layer delineating the granuloplasm from the peripheral hyaloplasm. In cell areas lacking a hyaloplasmic sheet the actin layer immediately borders the plasma membrane. The amount of actin within the continuous layer seems to increase from the advancing front to the middle cell region and to decrease again toward the uroid. The distribution of myosin is largely congruent to the display of actin, with the exception that the myosin-based fluorescence of the cortical layer gradually increases from the front to the uroid. A considerable amount of actin and myosin is also distributed around the nucleus and the contractile vacuole. In immobilized cells contracted by the external application of 10(-4)M procaine hydrochloride the cortical layer distinctly increases in thickness. In contrast to normal locomoting cells actin and myosin show a uniform distribution within the cell cortex along the entire surface. In pinocytosing cells, up to three cortical layers conspicuously rich in actin are produced during the process of channel formation. One of these layers is located in close proximity to the plasma membrane of the pinocytotic channels and the vacuoles. The immunocytochemical results are discussed with respect to earlier observations on the distribution of actin and myosin in Amoeba proteus as obtained by other methods.

Actins↗
PubMed1983

Immunocytochemistry of the acellular slime mold Physarum polycephalum. III. Distribution of myosin and the actin-modulating protein (fragmin) in sandwiched plasmodia.

The acellular slime mold Physarum forms very thin plasmodia when sandwiched between two agar sheets. After extraction with glycerol-containing buffers, suitable objects for immunofluorescence microscopy are obtained, and an analysis of the cytoskeletal and contractile system of Physarum becomes possible. Plasmodia were stained with antibodies against myosin and fragmin, a protein factor involved in actin filament length regulation. The microanatomy and topography of cellular structures containing these proteins were investigated at the light and electron microscopic levels. The patterns obtained with the two antibodies are closely related to those obtained with actin antibody [25]. In both cases the complex system of cytoplasmic fibrils is stained selectively. The fibrils form a more or less regular network in the advancing front zone with the fibrils being interconnected by focal nodes. In the posterior region of the plasmodium, where endoplasmic pathways and protoplasmic veins are differentiated, larger fibrils are detected, running obliquely or longitudinally to the veins. With both antibodies the fluorescent pattern of the fibrils is continuous without indications of periodic interruptions or striations, which would be expected in the case of sarcomere-like subunits. With anti-myosin unstained patches are frequently seen at or close to the nodes of the fibrillar network in the anterior region. The small lobopodia, which are rich in actin, are apparently not stained by the myosin antibody, a result similar to the situation in "ruffling edges¿ of cultured vertebrate cells. Electron microscopic investigations of antibody-labeled fibrils in embedded and sectioned plasmodia allow the identification of antibody molecules at specific sites along the fibrils with a different distribution pattern for each of the two antibodies.

Animals↗
PubMed1983

[Reaction of the whole body to auxiliary liver transplantation].

Changes of hemoglobin, hematocrit, blood pressure, blood lactate concentration, and blood pyruvate concentration, as well as in the acid-base balance, the electrolyte metabolism, and the enzyme activities into the serum were investigated in auxiliary liver transplantation in 5 dogs. Transitory hypokalemia and hypoglycemia, a slight controllable acidosis caused by lactate accumulation, as well as a strong short-term increase of the enzyme activities in the serum are an expression of the functioning of the transplanted liver. Hyperkalemia, a massive increase of the blood lactate concentration with uncontrollable acidosis, a therapy-resistant depression in blood pressure, and a slow continuous increase of the enzyme activities in the serum are symptoms of the irreversible ischemic damage of the transplanted liver. The avoidance of an irreversible ischemic damage during the preservation, the maintenance of a normal blood pressure after the transplantation, as well as the compensation of acidosis, hypoglycemia, and hypokalemia are of decisive importance for a successful liver transplantation.

Acid-Base Equilibrium↗
PubMed1983

Isolation and characterization of mammalian villin and fimbrin, the two bundling proteins of the intestinal microvilli.

Using a Mg2+ rather than the standard Ca2+ precipitation method microvillus membrane vesicles of porcine intestinal epithelial cells with a relatively well preserved cytoskeleton are obtained. Such vesicles are long and relatively straight and retain some of the core filament structure typical of non-vesicularized microvilli. They are therefore a good starting material for the purification of mammalian F-actin bundling proteins. We have purified the two previously predicted bundling proteins villin and fimbrin from such preparations and show that in most but not all aspects they resemble their counterparts in chicken microvilli. The now documented F-actin severing activity of purified porcine villin explains the easy vesicularization of porcine microvilli in the traditional Ca2+ precipitation method.

Animals↗
PubMed1982

Microfilament-membrane interaction: the brush border of intestinal epithelial cells as a model.

The intestinal epithelium provides an excellent starting material for the isolation of natural microfilament organizations in amounts suitable for biochemical studies. The microvillus filament bundle core and the terminal web provide two distinct microfilament systems. We review the current knowledge of the filament bundle core and the attempts that have been made to reconstitute this structure from actin and its four major associated proteins. We show in addition that a high molecular mass actin-binding protein (TW-260/240) having spectrin-like properties is, next to myosin, the major associated protein of the terminal web retained in isolated brush borders. We summarize the biochemical and morphological evidence for the existence of a class of spectrin-related molecules in the cortical cytoplasm of many cell types. These findings may lead to a new understanding of membrane-microfilament interactions.

Animals↗
PubMed1982

F-actin-binding and cross-linking properties of porcine brain fodrin, a spectrin-related molecule.

The axonally transported high molecular weight protein fodrin, known to be present in the cortical cytoplasm of neurones and other cells, has been purified to homogeneity and several of its biochemical properties have been characterized. Fodrin is an F-actin-binding and cross-linking protein inducing actin gels. It is composed of two nonidentical polypeptide chains (Mr = 240,000 and 235,000) which form a tetrameric complex of a molecular weight close to 930,000. The similarity of fodrin with tetrameric erythrocyte spectrin is directly shown by rotary shadowed molecules both alone and in interaction with F-actin. The gelation and cross-linking activity of fodrin is influenced both by ionic strength and pH in a manner similar to other cross-linking factors. These results strengthen previous concepts concerning the existence of spectrin-related molecules in nonerythroid cells and point to a possible related function in the submembranous microfilament organization in nonmuscle cells.

Actins↗