Showing papers by "University of Tübingen published in 1974"

The development of the macronucleus in the ciliated protozoan Stylonychia mytilus

Abstract: Ciliated protozoa are characterized by generative micronuclei and vegetative polyploid macronuclei. Micronuclei of Stylonychia mytilus contain 1 600 times as much DNA per haploid genome as E. coli. Most of this DNA is shown to be repetitive. The development of the macronucleus involves, as demonstrated by cytology, only 1/3 of the chromosomes which in a first replication phase are polytenized in probably 5 replication steps and appear as giant chromosomes. At this developmental stage considerable amounts of repetitive DNA are still present in the chromosomes. During the subsequent disintegration phase more than 90% of the DNA are eliminated from the macronucleus anlage. The remainder is further replicated five times and composes the final macronucleus. Since this DNA reassociates with a reaction rate almost identical to an ideal second order reaction its kinetic complexity can be determined by comparison with the kinetic complexity of E. coli DNA. Macronuclear DNA reassociates with a kinetic complexity of 26 times the kinetic complexity of E. coli DNA (corrected for GC content) which indicates that macronuclear DNA sequences exist at a ploidy level of 4 096 C. We assume that macronuclear DNA may be present only once per haploid genome. In this case it represents only 1.6% of the DNA in micronuclei or 10% of the DNA in the giant chromosome stage.

UDP-glucuronyltransferase in perfused rat liver and in microsomes: influence of phenobarbital and 3-methylcholanthrene.

Abstract: Liver microsomal UDP-glucuronyltransferase (1-naphthol as substrate) is activated about 10-fold by treatment of native microsomes in vitro with Triton X-100. Following pretreatment of rats with 3-methylcholanthrene or phenobarbital the specific activities of detergent-activated microsomes were increased by about 300% and 40%, respectively, while the corresponding increases in native microsomes were only about 70% and 10%, respectively. In isolated liver perfused with 0.5 mM 1-naphthol, the rate of glururonidation of naphthol, as determined by the appearance of naphthol glucuronide in the perfusate, bile and liver tissue, was 0.1 μmol × min−1× g liver−1. This rate of glucuronidation was increased by 70% in rats pretreated with 3-methylcholanthrene and by 140% following phenobarbital treatment, in contrast to the changes observed in microsomes. A UDP-glucuronic acid level of 0.3 μmol/g liver was determined in perfused liver from control rats. This level remained unchanged during perfusion with 0.5 mM 1-naphthol. In the perfused liver from phenobarbital or 3-methylcholanthrene-treated rats, the UDP-glucuronate level increased to 0.5 μmol/g liver. In control, 3-methylcholanthrene or phenobarbital-treated rats, rates of glucuronidation of 1-naphthol in the perfused liver system correspond best with the UDP-glucuronyltransferase activities determined in native microsomes when the different UDP-glucuronate levels, microsomal protein contents and liver weights are taken into account. The results suggest that the enzyme is mostly latent in the microsomal membrane and that this latency is increased after pretreatment of rats with 3-methylcholanthrene despite the marked enzyme induction.

Frequency and directional responses of cilia to membrane potential changes inParamecium

Abstract: Ciliary motor reactions and membrane responses to injected current stimulation inParamecium caudatum were recorded with a combined electrophysiological and high-speed cine system to investigate relations between ciliary activity and membrane potential. The power stroke of the cilia normally directed to the right rear rotates clockwise to a more posterior orientation in response to hyperpolarizing stimulation. Depolarization induces a counterclockwise shift, usually leading to the rapid reversal of beat direction toward the anterior end (Fig. 15). Ciliary frequency is increased either with hyperpolarization or with moderate or strong depolarization of the cell membrane. The frequency response is linked to the directional response in such a way that minimal frequency occurs during transition from reversed to normal beating, and that with increasing clock-wise or counterclockwise angular deviation of the power stroke from this sector of transition the frequency of beat is increased. In the course of transition from the reversed to normal beating the cilia are inactivated, i.e. they stick out perpendicularly to the cell surface without a polarized beat. A depression in normal beating activity somewhat resembling inactivation occurs with small depolarizations. Hyperpolarization-induced frequency time courses are significantly slower than those evoked by membrane depolarization. The role of transmembrane calcium fluxes and consequent modification of intraciliary calcium concentrations is considered with regard to the observed ciliary responses.

Taste bud types in fishes. II. Scanning electron microscopical investigations on Xiphophorus helleri Heckel (Poeciliidae, Cyprinodontiformes, Teleostei).

Abstract: Within the epithelium of the head gut of the sword-tail (Xiphophorus helleri Heckel) there are three types of taste buds that can be identified with certainty in the scanning electron microscope. The breathing valves, which are situated behind the mouth region, bear relatively high epidermal papillae in which type I taste buds can be found. The middle region of the head gut is mostly occupied by low epidermal papillae containing type II taste buds. Type III taste buds are present within the metabranchial head gut; they never rise above the normal level of the epithelium. Taste buds of each type show two kinds of receptor villi within their receptor areas: tall villi (about 1,5×0,5 μm) and small villi (about 0.5×0.2 μm). A few tall villi belonging to solitary chemosensory cells are situated between the superficial epithelial cells of the tongue. In addition, the surface of the epidermal cells shows a delicate microridge system.—It is postulated that the taste buds of different types serve different functions: Taste buds within epidermal papillae may act both as chemoreceptors, and mechanoreceptors. Taste buds that never rise above the normal level of the epithelium perhaps act predominantly as chemoreceptors.

Der Einfluß des Mondlichtes auf die Aktivitätsperiodik nachtaktiver Säugetiere.

Abstract: 1. Mehrmonatige Aktivitatsregistrierungen unter naturlichen Beleuchtungsbedingungen in Aquatornahe (Kolumbien) zeigen, das die lunarperiodisch bedingten Anderungen der Nachthimmelshelligkeit das Aktivitatsverhalten nachtaktiver Saugetiere in unterschiedlicher Weise beeinflussen. 2. Nachtaffen (Aotus trivirgatus) beschranken ihre Aktivitat bei Neumond weitgehend auf Abend- und Morgendammerung und sind bei Vollmond die ganze Nacht hindurch sehr aktiv (Abb. 5). Bei der neotropischen BlattnasenfledermausArtibeus lituratus hingegen wirkt Mondlicht aktivitatshemmend. Entsprechend senkt sie ihre Aktivitat bei zunehmendem Mond in der ersten, bei abnehmendem Mond in der zweiten Nachthalfte und bei Vollmond wahrend der ganzen Nacht (Abb. 6). Nilflughunde (Rousettus aegyptiacus) erreichen ihre maximale Aktivitat bei zunehmendem Mond, die BlattnasenfledermausPhyllostomus hastatus bei abnehmendem Mond (Abb. 8 und 9). Beide haben bei Vollmond die geringste Adtivitat. Goldhamster (Mesocricetus auratus) lassen im Naturtag keine beleuchtungsbedingten Aktivitats- und Aktogrammanderungen erkennen. 3. Die Befunde legen eine Einteilung in drei Grundtypen der Reaktion auf lunarbedingte Anderungen der Nacht-Beleuchtungsstarke (Aotus-, Artibeus- undMesocricetus-Typ) sowie verschiedene Ubergangsformen nahe. Sie sprechen dafur, das das Licht das Aktivitatsverhalten sowohl uber das circadiane System als auch direkt beeinflust, das diese beiden Komponenten unterschiedlich stark ausgepragt sein konnen, und das bei beiden proportionale und differentielle Wirkungen des Lichtes vorliegen. 4. BeiRousettus last sich eine direkte Beziehung zwischen dem Verhalten unter naturlichen Beleuchtungsbedingungen und der in Laborversuchen nachgewiesenen „Optimumsfunktion” der Abhangigkeit der Aktivitat von der Beleuchtungsstarke aufzeigen. Es ist zu erwarten, das Entsprechendes fur alle arten gilt, bei denen ahnliche beleuchtungsbedingte Aktivitatsoptima bzw. Aktivitats- und Aktogrammanderungen unter naturlichen Beleuchtungsbedingungen nachgewiesen sind.

Metabolism of 17α-Ethinylestradiol by Human Liver Microsomes in Vitro: Aromatic Hydroxylation and Irreversible Protein Binding of Metabolites

Abstract: Incubation of 2,4,6,7-[3H] estradiol and 2,4,6,7-[3H] ethinylestradiol with human liver microsomes and a NADPH-regenerating system resulted in an oxidative attack on tritiated positions of the estrogens. The tritium of the oxidized portions we recovered from the incubations as HTO. Hydroxylation of estradiol and ethinylestradiol at ring B is of minor importance and accounted for only 4–5% as compared to the oxidation of C-2 and C-4 of ring A. Using a substrate concentration of 20 nmol/ml, the initial velocities of hydrogen displacement ( ± SD) from C-2 and C-4 were 119 ± 58 (estradiol) and 237 ± 104 (ethinylestradiol) . The corresponding figures for displacement from the positions 6,7 were 4.2 ± 2.1 (estradiol) and 9.9 ± 4.8 (ethinylestradiol) . The apparent difference between the oxidation of ring A and ring B of estradiol and of ethinylestradiol is explained by the fact that hydroxylation is hindered at C-16 due to the 17α-ethinyl group, and by the competitive nature of 16- and 2-hydroxylation ...

[Functional adaptations of shape and structure in shark teeth (author's transl)].

Abstract: An der Oberflache von Selachierzahnen befindet sich eine dem Schmelz der Saugetiere analoge Schicht, die von Reif erstmals eingehend elektronen-rastermikroskopisch untersucht worden ist. Die mechanische Widerstandsfahigkeit dieser 0,2–0,9 mm dicken Schicht ist groser als diejenige des Dentins.

Epistatic gene interaction, crossing over, and linked and unlinked inversions in drosophila subobscura.

Abstract: In theoretical population genetics the one locus-two allele system has served for a long time as a very useful tool in model building and many fundamental theories have been worked out by the use of it. Although the value of such simplified models can not be overlooked it became clear very soon that the assumption of independent genes is unrealistic since genetic systems exhibit an interconnected complexity. As soon as two locus models are considered, the problem, however, becomes much more difficult. The very important parameters as linkage and epistatic gene interactions can be introduced in the mathematical treatment leading to more realistic models. A summary of the theoretical findings showing the significance of the problems has been given by Kimura and Ohta (1971) and Kojima and Lewontin (1970). Although the theoretical treatments of epistasis and linkage have shed much light on the load problem and how multiple polymorphism and genetic variabilities can be maintained in populations, there are only a few experimental investigations dealing with two locus problems. Inversion polymorphisms in natural populations of several Drosophila species offer good material for analyzing the role of linkage and epistasis. Independent inversions of homologous chromosomes show very often nonrandom associations, in as far as coupling or repulsion phases are much more frequent than theoretically expected (Levitan, 1958; Bmcic, 1961; Mather, 1963; Stalker, 1964). An extreme case has been reported for Drosophila subobscura (Sperlich and Feuerbach, 1969). In this European species independent but linked inversions oc-

Metabolic products of microorganisms

Abstract: The transport of 55Fe3+, mediated by various fungal sideramines, was tested using an ornithine-deficient mutant of Neurospora crassa (arg-5, ota, aga), which can be cultivated completely free of its own sideramines. We have found that Neurospora crassa is able to accumulate iron by its own chelate coprogen (K m∼20 μM, V max∼1.74 nmol/mg min) and also by the two exogenous sideramines ferricrocin (K m∼5 μM, V max∼0.22 nmol/mg min) and ferrichrysin (K m∼20 μM, V max∼0.4 nmol/mg min) produced by members of the genus Aspergillus. Other sideramines like ferrichrome, ferrichrome A, and ferrirubin were relatively ineffective as iron transport molecules for this organism. Competitive inhibition of coprogen uptake was observed with all ferrichrome-group compounds: ferrichrysin (K i∼140 μM), ferrichrome and ferricrocin (K i∼5 μM). Ferrirubin (K i∼0.5 μM) was the strongest inhibitor of coprogen uptake in Neurospora crassa. Inhibition experiments indicate that ferrirubin may possibly block the uptake of coprogen and ferrichrome-type compounds by occupying the receptor sites without being preferably transported. For further characterisation of the coprogen uptake system in Neurospora crassa comparative uptake experiments were performed with the parent wild-type strain 74 A, and with a ferricrocin-producing Aspergillus fumigatus strain.

The content of scandium, thorium, silver, and other trace elements in different plant species

Abstract: Thirty five plant species apartaining to 16 divisions, representing the main plant kingdom, as well as some soil samples collected under these plants, were analysed for Sc, Th, Cr, Co, Rb, Cs, Fe, Zn, and Ag. Higher amounts of scandium and thorium as well as of other elements were found in some fungi (Basidiomycetes) and bryophytes, whereas a lower content was found in angiosperms and gymnosperms. A higher silver content was found in some plant species.

Synthese des biologisch aktiven Undecapeptids Substanz P nach der Flüssig‐Phasen‐Methode

Abstract: The synthesis of the biological active undecapeptide substance P with the liquid-phase method (LPM) is described The over-all-yield of the synthesis is high and the peptide shows full biological activity The synthesis demonstrates that the modification of the liquid-phase synthesis, the cristallisation method, enables the preparation of peptides in short time with high yield and purity

Migration of Diplostomum spathaceum (Trematoda) in the fish intermediate host

Abstract: The migratory route of Diplostomum spathaceum to the eye lens of the fish host was determined by examining fishes killed at various times after infection in the laboratory by immersion in water containing cercariae. Migration occurred mostly in subcutaneous connective tissue and muscles of the trunk. Neither peritoneal cavity nor circulatory system served as a major migratory route. Rate of migration was estimated to be about 5 mm/hr with the aid of caudal fin immersion technique. Successful migration depended largely on adequate glycogen reserves and secretions of penetration glands. Only diplostomula that could plow their way to fish lenses survived the host tissue reactions; the remainder underwent phagocytosis.

Ultrastructural study of arterio-venous anastomoses in gill filaments of Tilapia mossambica

Abstract: Arterio-venous anastomoses (AVA) in gill filaments of Tilapia mossambica exhibit a distinct polarity. Two different types of highly specialized endothelial cells, both of epitheloid shape, line these vessels: Type I cells, contacting the arterial lumen, are elongated and about two to three times as large as type II endothelial cells. Their surface is increased by tentacular protrusions which reach far into the arterial lumen. Filament whorls forming tubelike structures with centrally located glycogen granules are abundant in these cells. Type II endothelial cells are located proximal to the central venous sinus (CVS). Their less abundant and more electron dense cytoplasm is free of filament whorls. There are also intermediate cell forms at approximately the middle of each anastomosis. Short cell processes protrude from all endothelial cell types into the AVA lumen. Outside the indistinct vascular basement lamina, a layer of cover cells tightly envelopes the AVA. These cells are, however, absent around the part of the AVA adjacent to the CVS. Here the endothelial cells are in immediate contact with the interstitium. Endothelial cells sheathed by cover cells reach the interstitium through basal foot processes. Nerve fibre bundles regularly come into close contact with the AVAs. Possible functions of the AVAs, including osmoreception are discussed.

The contribution of solvent drag to the intestinal absorption of the acidic drugs benzoic acid and salicylic acid from the jejunum of the rat.

Abstract: 1 Jejunal loops of anaesthetized rats were perfused with hypotonic, isotonic and hypertonic buffered solutions containing 14C-labelled benzoic acid and salicylic acid at pH 62 and 22 The blood flow of the loop was maintained at an intermediate rate (078–097 ml min−1 g−1) The water net flux was determined by polyethylene glycol as non-absorbable marker and amounted up to +31 or-27 μl min−1 g−1 2 A positive water net flux (leaving the gut lumen) increased the appearance rate of benzoic acid and salicylic acid in the intestinal venous blood by maximally 47 and 41%, a negative water net flux (entering the gut lumen) diminished the appearance rate by 28 and 37% 3 The experimental data were analysed by means of a kinetic model The parameters of the model were the epithelial permeability kF D , the serosal permeability k S F S and the sieving coefficient Φ=1−σ The epithelial permeability was 0115 and 0107 for benzoic acid and salicylic acid at pH 62 and increased to 0163 and 0185 ml min−1 g−1 at pH 22 The serosal permeability was assumed to be identical for neutral and acidic pH and amounted to 0046 and 0112 ml min−1 g−1 indicating that a certain proportion of the absorbed drugs was transferred to the serosal side The sieving coefficient was 292 and 231 at neutral pH and 379 and 356 at acidic pH 4 The main resistance to the absorption of the two drugs is the epithelial membrane, since the effective blood flow and the unstirred layer are not ratelimiting The high sieving coefficient for the two drugs is interpreted as indicating an interaction of drug and water molecules inside the lipid part of the cell membrane (which contains at least 30% water) The electric potential across the gut wall may contribute to the size of the sieving coefficient, if the drug molecules permeate also in the ionized form 5 Using acidic perfusion solutions the epithelial permeability and the sieving coefficient were increased by the factor 13–15 This increase can be explained sufficiently by a facilitated entrance of the unionized drug molecules into the epithelial membrane

The contribution of solvent drag to the intestinal absorption of the basic drugs amidopyrine and antipyrine from the jejunum of the rat.

Abstract: 1. Jejunal loops of anaesthetized rats were perfused with hypotonic, isotonic and hypertonic buffered solutions containing 14C-labelled amidopyrine and antipyrine at neutral and at acidic pH. The blood flow of the loop was maintained at an intermediate rate (0.7–1.0 ml min−1g−1). The water net flux was determined by means of polyethylene glycol as non-absorbable marker and amounted up to ±30 μl min−1g−1. 2. A positive water net flux (directed towards the blood) increased the appearance rate of amidopyrine and antipyrine by maximally 43.8 and 49.2%, a negative water net flux (directed towards the gut lumen) diminished it by 38.8 and 35.0%. 3. The experimental data were analysed by means of a kinetic model with the water net flux as independent variable and the epithelial permeability kFD, the serosal permeability kSFS and the sieving coefficient Φ=1−σ as absorption parameters. For antipyrine independent of the pH-value of the perfusion solution kFD was 0.123, and, for amidopyrine at pH 7 and pH 3 kFD was 0.231 and 0.091, respectively. kSFS was zero indicating that in this experimental arrangement the transfer of drug molecules to the serosal side was negligible. The sieving coefficient Φ amounted to 2.30 for amidopyrine and 2.15 for antipyrine at neutral pH. At acidic pH it amounted to 0.50 for amidopyrine and 1.44 for antipyrine. The hydraulic permeability of water was identical at neutral and acidic pH. 4. The high sieving coefficient for the two drugs at neutral pH is interpreted as indicating that water and lipophilic drug molecules interact within the lipid part of the cell membrane. At acidic pH the ionized drug molecules appear to permeate the cell membrane preferentially across other (presumably more hydrophilic) areas.

Epidural and subdural haematomas as a complication of internal drainage of cerebrospinal fluid in hydrocephalus.

Abstract: After mentioning the most important indications for the implantation of atrio-ventricular systems in increased intracranial pressure, the importance of epidural and/or subdural bleeding as one of the main postoperative complications is pointed out. In the literature, known to us, there are reports of 9 epidural and 25 subdural haematomas. Four more personal cases are reported. The cause of the bleeding is collapse of the cortex which leads to rupture of cortical veins or epidural vessels. Especially at risk are adult patients with high intracranial pressure or atrophy of the cortex in long standing hydrocephalus. Epidural haematoma always develops in the first few hours after the operation, whereas subdural haematomas may develop either in the first days or even after weeks and months. The incidence of this complication in our adult patients is 5.6%. Some possibilities for the prophylaxis of intracranial bleeding are mentioned.

Chemical Automata in Homogeneous and Reaction-Diffusion Kinetics

Abstract: A finite automaton or, synonymously, a finite state machine is in the simplest case a triple (X,I,λ), whereby X is a finite set of states, I is a finite set of inputs, and λ is the next-state mapping, such that λ : X x I → X (cf. Arbib, 1969). For example, if x1 and x2 are two state variables each possessing two possible states, the whole automaton has four possible states, and λ specifies the transitions between these states in dependence on a given input. If the input is constant, one speaks of an autonomous automaton, otherwise of a nonautonomous automaton .

Nuclear-magnetic-resonance with 13C and 31P and circular-dichroism studies of a ternary complex of spermine, Cu2+ and AMP.

Abstract: The formation of a ternary complex using cupric ions, basic amines of biological significance, and nucleotides was examined employing high-resolution nuclear magnetic resonance (NMR) with 13C and 31P and circular dichroism. The reaction of Cu2+ with each ligand was studied separately and as the ternary complex. From 13C-NMR data the assignment of the respective carbon atoms adjacent to a copper-binding atom was clearly shown. It is intriguing to note that even in such a ternary complex the N-7 of the purine ring, as well as the phosphate residue (measured by 13P-NMR spectroscopy) provide the preferred binding sites for the cupric ion. Marked interactions of the chelated cupric ion with the ribose moiety in the ternary complex were deduced from circular dichroic measurements. No such reactivity was seen when dAMP was employed. The existence of a ternary Cu · AMP · amine complex opens a number of new aspects regarding the reactivity of metal ions in the biochemistry of nucleic acids.

Hexadecapole interaction in the atomic ground state of165Ho

Abstract: Using the atomic beam magnetic resonance method several hyperfine transitions in the ground state of165Ho were measured at magnetic fields near zero Oe. Including a hexadecapole interaction constantD a perfect fit of the seven hyperfine separations was possible giving the following results:A′=800.583645 (6)MHz,C′=−1.504 (37)kHzB′=−1668.00527 (33)MHz,D′=−0.137 (14)kHz. These interaction constants have been corrected for second order hyperfine interaction within the4I ground multiplet. The corrected constants are the following:A=800.583173 (36)MHz,C=−0.249 (140)kHzB=−1668.078 70 (330) MHz,D=−0.148 (16) kHz. Using a value for 〈r4f/−5〉Ho of Fraga a nuclear hexadecapole moment can be calculated:Π(165Ho)=0.89·10−48cm4. Because of severe uncertainties still present in the theory for calculating the electronic matrix elements this value can be only regarded as highly speculative.

Prefabrication of shell ornamentation in the bivalve Laternula

Abstract: The minute, cone-like spikes which cover the valve surfaces of Laternula arc formed by the mantle in advance of the growing shell margin and are subsequently incorporated into the calcarcous shell. This ‘prefabrication’ process allows the formation of a prismatic spike ultrastructure distinct from other layers of the nacro-prismatic shell and provides ornamentation to the otherwise uncalcified ventral surface. A consideration of a number of morphologic variables, including the mechanism of shell construction, suggests that spikes function to increase the skin friction of the valve surfaces and thereby promote a stable life position. Variations on Laternula's shell construction mechanism arc found throughout the Pandoracea and possibly larger taxonomic groupings.