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F Wunderlich

Publications and source records attributed to F Wunderlich.

At least 55 records · Page 3Linked to original sources
PubMed1977

Reversibly contractile nuclear matrix. Its isolation, structure, and composition.

From Tetrahymena macronuclei we have isolated a reversibly contractile nucleo-skeleton, i.e., an "expanded" nuclear matrix which reversibly contracts when the total concentration of the bivalent cations, Ca and Mg (3:2), is decreased to 5 mM or increased to 125 mM. During contraction the average diameter of the expanded matrix becomes reduced by about 24%; this corresponds to a volume contraction of about 55%. The reversible contraction of the nuclear matrix does not depend on ATP and cannot be inhibited by salygran. The expanded matrix is obtained by removing carefully from the macronuclei 89.7% of the phospholipid, 99.6% of the DNA, 98.5% of the RNA, and 74.8% of the protein by treatment with Triton X-100 and digestion with DNase and RNase followed by an extraction with 2 M NaCl. Electron microscopy reveals, within the expanded matrix, residual equivalents to the structures characteristic for macronuclei: (a) a residual nuclear envelope with nuclear pore complexes; (b) residual nucleoli at the periphery; (c) a fibrillar internal network. The expanded matrix is essentially composed of proteins (96.2%) and traces of DNA (0.8%), RNA (0.5%), phospholipid (1.6%), and carbohydrates (0.9%). The last, which have been determined by gas chromatography, contain glucose, mannose, and an unidentified sugar in the ratio 1:5.4:5.7. The ratio of acidic to basic amino acids of the expanded matrix is 1.55. Sodium dodecyl sulfate (SDS) gel electrophoresis reveals a predominant protein with a mol wt of 18,000 which is apparently involved in the reversible contractile process. The mechanism of this reversible contraction of the expanded matrix remains to be elucidated, but it differs both from actin-myosin contraction systems and from the contractile spasmoneme system in vorticellids.

Calcium↗
PubMed1976

Structural transformation of the phagosomal membrane in Tetrahymena cells endocytosing latex beads.

A model system with a high phagosomal membrane turnover has been developed: During a 45-min period Tetrahymena cells endocytoze 186 latex beads (diameter: 2.02 mum) per average cell; 166 of these beads are then exocytozed in the course of the following 145 min. During the endocytotic phase an average cell is approximated to fabricate 1200 mum2 phagosomal membrane. Freeze-etch electronmicroscopy reveals that both fracture faces of the nascent phagosomal membrane are associated with the typical 85 A-particles in approximately equal numbers. Mature phagosomal membranes, however, show an unequal particle distribution. Smooth areas, smooth areas bordered with a fracture rim, and particle-associated depressions up to a diameter of 130 nm can be observed especially on fracture faces of mature phagosomes in the endocytotic phase. These are discussed with respect to membrane fusion.

Animals↗
PubMed1975

Membranes of Tetrahymena. IV. Isolation and characterization of temperature-responsive smooth and rough microsomal subfractions.

Temperature-responsive microsomes of the ciliate protozoan Tetrahymena have been originally fractionated by step centrifugation on two-layered, Mg2+-containing sucrose gradients. Three fractions have been obtained, which are termed smooth I, smooth II and rough according to the appearance of the membrane vesicles upon electron-microscopy. Smooth I, smooth II, and rough microsomes exhibit RNA/protein ratios of 0.09, 0.20, and 0.34; their phospholipid/protein ratios and their neutral lipid/phospholipid ratios were 0.52, 0.43 and 0.25, and 0.17, 0.18 and 0.13, respectively. All three fractions contain equivalent, low succinic dehydrogenase and 5'-nucleotidase activities. Glucose-6-phosphatase and acid phosphatase are more concentrated in smooth I membranes than in rough membranes. The reverse is true for ATPase. The smooth II membranes occupy an intermediate position except that their ATPase activity is the lowest of the three fractions. The specific activities of these enzymes of the three microsomal fractions are compared to those of homogenates of whole cells. Thin-layer chromatography reveals a very similar polar and nonpolar lipid pattern of the three microsomal fractions. The major phospholipid compounds are phosphatidlethanolamine, glycerideaminoethylphosphonate and phosphatidylcholine, while diglycerides, an unknown NL-compound, and triglycerides are the major apolar lipids. Gas liquid chromatography shows that the fatty acids are mainly even-numbered ranging between C12 and C18. The smooth I, smooth II and rough membranes contain 65.2, 69.3 and 72.7% unsaturated fatty acids in their polar lipids, whereas only 52.7, 49.7 and 48.3% unsaturated acids are found in their apolar lipids, respectively. The fatty acids are more unevenly distributed among the individual polar lipids than in the apolar ones.

Acid Phosphatase↗
PubMed1975

Thermotropic lipid clustering in tetrahymena membranes.

The effect of temperature on the core structure of endoplasmic reticulum membranes has been visualized directly in cells of the poikilothermic eukaryote Tetrahymena pyriformis by freeze-etch electron microscopy. Moreover, the effect of temperature on the smooth microsomal membrane vesicles isolated from these cells, as well as on the extracted membrane lipids, has been examined by fluorescence probing, electron spin resonance, proton nuclear magnetic resonance, and calorimetry. Freeze-etch electron microscopy of T. pyriformis cells, equilibrated at different temperatures between 28 and 5 degrees, reveals the emergence of smooth areas on the fracture faces of endoplasmic reticulum membranes at temperatures below similar to 17 degrees. In this temperature range, we also find discontinuities in the glucose 6-phosphatase activity, in the fluorescence intensity of 8-anilino-1-naphthalensulfonate, in the partition of 4-doxyldecane, and in the separation of the outer hyperfine extrema of 5-doxylstearic acid in the microsomal membranes. These membranes apparently contain at least two lipid environments of different fluidity as indicated by the 12-doxylstearic acid spin-label. Proton nuclear magnetic resonance of the extracted membrane lipids indicates an abrupt change of the fatty acid chain mobilities at temperatures below similar to 17 degrees. This, however, is not due to a true thermal liquid crystalline in equilibrium crystalline phase transition. Calorimetric measurements also support this conclusion. The thermotropic alterations observed within the membranes are interpreted to be due primarily to a clustering of "rigid" liquid crystalline lipid environments which exclude membrane-intercalating proteins.

Animals↗
PubMed1974

Reversible, thermotropic alteration of nuclear membrane stucture and nucleocytoplasmic RNA transport in Tetrahymena.

We examine the effect of cooling upon the freeze-etch ultrastructure of nuclear membranes, as well as upon nucleocytoplasmic RNA transport in the unicellular eukaryote Tetrahymena pyriformis. Chilling produces smooth, particle-free areas on both faces of the two freeze-fractured macronuclear membranes. Upon return to optimum growth temperature the membrane-associated particles revert to their normal uniform distribution and the smooth areas disappear. Chilling lowers the incorporation of [(14)C]uridine into whole cells and their cytoplasmic RNA. Cooling from the optimum growth temperature of 28 degrees to 18 degrees C (or above) decreases [(14)C]uridine incorporation into cells more than into their cytoplasmic RNA; chilling to below 18 degrees C but above 10 degrees C causes the reverse. [(14)C]Uridine incorporation into whole cells and their cytoplasmic RNA reflects overall RNA synthesis and nucleocytoplasmic RNA transport, respectively. RNA transport decreases strongly between 20 degrees and 16 degrees C, which is also the temperature range where morphologically detectable nuclear membrane transitions occur. This suggests that the nuclear envelope limits the rate of nucleocytoplasmic RNA transport at low temperatures. We hypothesize that a thermotropic lipid phase transition switches nuclear pore complexes from an "open" to a "closed" state with respect to nucleocytoplasmic RNA transport.

Animals↗