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I Schulze

Publications and source records attributed to I Schulze.

At least 19 recordsLinked to original sources
PubMed2001

Quantification of insect nitrogen utilization by the venus fly trap Dionaea muscipula catching prey with highly variable isotope signatures.

Dionaea is a highly specialized carnivorous plant species with a unique mechanism for insect capture. The leaf is converted into an osmotically driven trap that closes when an insect triggers sensory trichomes. This study investigates the significance of insect capture for growth of Dionaea at different successional stages after a fire, under conditions where the prey is highly variable in its isotope signature. The contribution of insect-derived nitrogen (N) was estimated using the natural abundance of 15N. In contrast to previous 15N studies on carnivorous plants, the problem emerges that delta15N values of prey insects ranged between -4.47 per thousand (grasshoppers) and +7.21 per thousand (ants), a range that exceeds the delta15N values of non carnivorous reference plants (-4.2 per thousand) and soils (+3 per thousand). Thus, the isotope-mixing model used by Shearer and Kohl to estimate the amount of insect-derived N is not applicable. In a novel approach, the relationships of delta15N values of different organs with delta15N of trapping leaves were used to estimate N partitioning within the plant. It is estimated that soon after fire approximately 75% of the nitrogen is obtained from insects, regardless of plant size or developmental stage. The estimates are verified by calculating the average isotope signatures of insects from an isotope mass balance and comparing this with the average measured delta15N values of insects. It appears that for Dionaea to survive and reach the flowering stage, seedlings must first reach the 6th-leaf rosette stage, in which trap surface area nearly doubles and facilitates the capture of large insects. Large amounts of nitrogen thus made available to plants may facilitate an enhanced growth rate and the progressive production of additional large traps. Dionaea reaches a maximum abundance after fire when growth of the competing vegetation is suppressed. About 10 years after fire, when grasses and shrubs recover, Dionaea becomes overtopped by other species. This would not only reduce carbon assimilation but also the probability of catching larger prey. The amount of insect-derived nitrogen decreases to 46%, and Dionaea becomes increasingly dependent on N-supply from the soil. Competition for both light and N may cause the near disappearance of Dionaea in older stages of the fire succession.

Animals↗
PubMed1998

Hydroperoxides mediate lithium effects on regeneration in Hydra.

Regeneration experiments in Hydra have shown that lithium long-term treatment apparently causes a transformation of prospective head into foot tissue. Although lithium ions are known to interfere with the PI-PKC signal-transduction system and evidence has been provided that this system plays a role in pattern formation in Hydra, its role in mediating the lithium effect on patterning is still obscure. The present study provides evidence that H2O2 and presumably also lipid hydroperoxides mediate the lithium effects. First, the perturbation of pattern formation is strikingly stronger in the strain Hydra vulgaris than in Hydra magnipapillata, and similar strain-specific differences are found in the long lasting accumulation of hydroperoxides following lithium treatment. Second, the antioxidant vitamins E and C, which suppress peroxide accumulation, and the H2O2-degrading enzyme catalase significantly protect H. vulgaris from lithium effects. Lithium treatment also negatively affects overall DNA synthesis in a similar strain-specific manner, which, however, cannot be rescued by antioxidant vitamins. The lithium-activated source of peroxide production differs from another source, which generates peroxide in untreated polyps of both strains. The results suggest that lithium treatment-induced peroxide accumulation in H. vulgaris provokes a cytotoxic response showing foot-like characteristics. Nevertheless, a role of peroxides as messengers in pattern forming processes can not be excluded.

Animals↗
PubMed1994

Growth condition-induced precocious activation of p34cdc2 kinase inhibits the expression of developmental competence.

We examined the effect of growth conditions upon mitotic p34cdc2 kinase and developmental competence in Acanthamoeba castellanii. At G2/M of the cell cycle p34cdc2 kinase activity peaks in level, and p34cdc2 is transiently in a complex with newly synthesized cyclin B and phosphorylated on tyrosine (pre-MPF). Developmental competence peaks in level slightly preceding p34cdc2 kinase activation and pre-MPF accumulation. Under adverse growth conditions p34cdc2 kinase activation and transient pre-MPF accumulation occur at a reduced G2 phase length and smaller cell size. Developmental competence is not expressed during the shortened G2 phase. Cycloheximide inhibits the precocious p34cdc2 kinase activation and both the precocious accumulation of cyclin B and tyrosine phosphorylation on p34cdc2. No-codazole inhibits the precocious p34cdc2 kinase activation as well; however, it does not affect the precocious accumulation of pre-MPF. Developmental competence increases in level during artificially elongated G2 phases. The results indicate that, first p34cdc2 kinase activation requires cyclin B in a complex with p34cdc2 and the presence of intact microtubuli, second establishment of competence requires a certain length of G2, and third the regulation of pre-MPF accumulation, and thus of cyclin B expression, plays a role in the relationship among growth condition, cell cycle progression, and expression of the developmental program.

Acanthamoeba↗
PubMed1991

Role of influenza B virus in hepatic steatosis and mitochondrial abnormalities in a mouse model of Reye syndrome.

The hepatic steatosis observed in the influenza B virus mouse model of Reye syndrome has been attributed to infectious virus or, alternately, to decreased food intake in the virus-treated mice or impurities in the virus preparation. To resolve this issue, 4- to 6-wk-old male Balb C mice were given, by intravenous injection, 12,800 hemagglutination units of influenza B Lee/40 virus in phosphate buffered saline/1% bovine serum albumin using virus prepared by ultra-centrifugation from infected allantoic fluid, by sucrose density-gradient purification of virus prepared by ultracentrifugation from infected allantoic fluid or by irradiation of virus prepared by ultracentrifugation from infected allantoic fluid to inactivate virus. The infectivity titer of virus prepared by ultracentrifugation from infected allantoic fluid was much higher than that of sucrose density-gradient purified virus prepared from infected allantoic fluid: 50% egg infectious dose for virus prepared by ultracentrifugation from infected allantoic fluid was 3.9 x 10(4)/hemagglutination unit vs. 8.7 50% egg infectious dose/hemagglutination unit for sucrose density-gradient purified virus prepared from infected allantoic fluid. Control mice received phosphate-buffered saline/1% bovine serum albumin or uninfected allantoic fluid diluted in phosphate-buffered saline/1% bovine serum albumin. Mice were fasted to eliminate dietary variation, and livers were obtained 36 hr after virus administration. Of the above treatments, only virus prepared by ultracentrifugation from infected allantoic fluid caused clinical illness and increased hepatic triglycerides (p less than 0.02) compared with controls. Hepatic triglycerides in virus prepared by ultracentrifugation from infected allantoic fluid correlated with histopathological vacuolization scores (r = 0.5773; p less than 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Relationship between the timing of DNA replication and the developmental competence in Acanthamoeba castellanii.

In Acanthamoeba, two different cell types are known. Trophozoites are generated in the mitotic division cycle, whereas cells committed at late G2 phase of the cell cycle develop into cysts in response to starvation. In this paper we study the role of timing of DNA replication in regulating development. The investigation was performed with cultures growing in a non-defined medium (ND cells) that show a high encystation competence and with cultures that have been growing in a chemically defined medium (D cells) for several years and show a low encystation competence. Bivariate DNA/BrdUrd distributions show that ND cells progress through a cycle in which the short replication phase occurs immediately and exclusively after prior completion of mitosis. These cells arrest at late G2 phase of the cell cycle during the stationary stage. In D cells, DNA replication and mitosis seem to be uncoupled, since replication takes place before as well as after mitosis. These cells arrest within their replication phase during the stationary stage. These findings indicate that D cells do not progress into late G2 phase of the cell cycle and hence do not have the competence for commitment. The alternate timing of DNA replication and the low encystation competence of D cells can be reversed by cultivation of these cells in ND medium. Synchronization experiments reveal that late G2 phase ND cells exhibit a low capacity for BrdUrd incorporation and growth after transfer into D medium, whereas ND cells of earlier phases of the cell cycle show premitotic incorporation of BrdUrd into nuclear DNA and growth. These findings suggest on the one hand that premitotic DNA synthesis is a prerequisite for growth of cells in D medium, and that there is a dependence of the induction of premitotic DNA synthesis on the cell cycle, and on the other hand that a reciprocal relationship exists between the capacity of premitotic DNA synthesis and commitment to differentiation.

Acanthamoeba↗
PubMed1987

Effect of essential amino acids on the phosphorylation of a 40S ribosomal protein and protein synthesis in Acanthamoeba castellanii.

Reversible and multiple phosphorylation of a 40S ribosomal protein is observed in a variety of eukaryotic cells. In the primitive eukaryote Acanthamoeba, one or three phosphorylated S3 derivatives are observed during growth phase in nondefined nutrient medium (ND cells) or in chemically defined nutrient medium (D cells), respectively. In both cases, stationary phase cells exhibit nonphosphorylated S3; however, transfer of these cells into the respective fresh nutrient media results in a transient accumulation of four phosphorylated S3 derivatives. Transfer of D cells into nutrient medium, deficient in all or any single essential amino acids, leads to reversible inhibition of S3 phosphorylation and growth arrest. The low level of phosphorylated S3 is not simply the consequence of growth arrest, since in cells where growth is arrested differently, the level of phosphorylated S3 can be high. In response to amino acid deficiency, a number of other changes can be observed. These include a 2-3-fold decrease of total protein synthesis, 13 changes in the cellular protein pattern, and specific alterations in the ribosome absorbance profiles and in the distribution of poly-A+ RNA within subribosomal and ribosomal fractions. While the rate of total protein synthesis seems to be associated with the level of phosphorylated S3, the level of the synthesis of at least 10 of the particular proteins can be dissociated from the level of S3 phosphorylation.

Amino Acids, Essential↗
PubMed1986

Adenoid cystic carcinoma of the salivary glands: an immunohistochemical study.

Twenty-four cases of adenoid cystic carcinoma from the Salivary Gland Registry of the University of Hamburg were analysed with respect to their differentiation and subclassification. With immunohistochemical methods, several groups of marker substances were analysed in these tumors: marker for a glandular function; immunoglobulins; metalloproteins; tumor markers; substances associated with the basal membrane and carbohydrate chains. The following patterns of histological differentiation were found: cribriform pattern with typical pseudocysts; tubular pattern with ductal elements; trabecular pattern with predominance of hyalinized stromal elements; basaloid pattern with low differentiated cells. For every pattern, a special immunohistochemical profile could be established. The morphological and immunohistochemical analysis revealed the following relation between the different patterns: Origin of the malignant proliferation is presumably the terminal ductal system of the salivary glands (indifferent cell of the reserve cell type). This cell can differentiate in 2 directions: a myoepithelial and a ductal cell type. Immunohistochemically, the presence of basement membrane-associated substances is accompanied by the appearance of myoepithelial-like cells. The presence of secretory products is a feature of ductal cells.

Antibodies, Neoplasm↗
PubMed1985

[Ventricular septal defect: late spontaneous closure].

25 patients who had a proven isolated small ventricular septal defect (VSD) when they were children were re-examined 3 to 19 years later, at the age of 20-21 years. Spontaneous closure was diagnosed if the murmur had disappeared and all other cardiological findings were normal. This was so in nine patients. Six of them had previously been followed to eight years or more with the definite diagnosis of VSD. In the three others who had only been followed to the age of 3-5 years the time of closure, whether early or late, could not be assessed.

Adult↗
PubMed1983

Interaction of catecholamine-derived alkaloids with central neurotransmitter receptors.

Catecholamine-derived alkaloids of the simple tetrahydroisoquinoline, 1-benzyl-tetrahydroisoquinoline and tetrahydroprotoberberine classes have been tested for their ability to inhibit the binding of seven different radioligands to neurotransmitter receptors of brain synaptic membranes. Alkaloids of all three classes were active in inhibiting 3H-clonidine binding to alpha 2-adrenergic receptors. Stereoselectivity of tetrahydropapaveroline in binding to alpha 2-adrenergic receptors was evidenced by the marked activity of the S-(--) isomer (IC50 = 0.65 microM) in comparison to the R-(+) enantiomer (IC50 = 50 microM). The simple tetrahydroisoquinolines (3,4-dihydroxytetrahydroisoquinoline and salsolinol), the four isomeric mono-O-methyl derivatives of 2,3,10,11-tetrahydroxyberbine and tetrahydropapaveroline were the most potent inhibitors of 3H-apomorphine binding to dopaminergic receptor agonist sites. The tetrahydroprotoberberines, as a class, were the most potent inhibitors of 3H-spiroperidol binding to dopaminergic receptor antagonist sites and of 3H-WB-4101 binding to alpha 1-adrenergic receptors. The 1-benzyl-tetrahydroisoquinolines exhibited varying degrees of interaction with beta 1-adrenergic receptors. Tetrahydropapaveroline (IC50 = 0.3 microM) was the most active of the 24 alkaloids tested in inhibiting binding of 3H-dihydroalprenolol to beta 1-adrenergic receptors. None of the alkaloids significantly affected 3H-QNB binding to muscarinic-cholinergic receptors, and selected alkaloids from each class interacted only moderately with serotonergic receptors.

Alkaloids↗
PubMed1982

Nerve growth factor and cyclic AMP: opposite effects on neuroblastoma-substrate adhesion.

Increased cellular adhesion has been postulated to be an early event required of neuroblasts undergoing neurite extension during differentiation. Nerve growth factor (NGF) induces neurite extension in a variety of cell types of neural crest origin. In the PC12 rat pheochromocytoma cell line, which has been proposed as a model for precursor cells to sympathetic neurons, NGF and dibutyryl cyclic AMP (dBcAMP) promote both neurite extension and an increased rate of cell-substrate adhesion. Since dBcAMP can substitute for NGF in this enhancement of adhesion rate in the PC12 cell line, cAMP has been suggested as a second messenger for NGF. We have shown that in two nearly diploid adrenergic like human neuroblastoma clones, the KA and SY5Y cell lines, which also extend neurites in response to both NGF and dBcAMP, only NGF enhances cellular adhesion, as defined by an increase in the number of cells cells prelabeled with 35S-methionine which attach to culture dishes at a given time. Incubation with monospecific antibodies directed against murine beta-NGF abolishes the NGF effect on adhesion. The NGF effect on human neuroblastoma is specific insofar as NGF does not facilitate adhesion of two glioma lines. Unlike the results obtained for PC12, in both SY5Y and KA lines, 1 mM dBcAMP decreases the rate of adhesion to levels significantly below those of controls. Adhesiveness of neuroblastoma cells treated with both NGF and dBcAMP is intermediate between that of cells treated with either agent alone. While theophylline mimics the dBcAMP effect, sodium butyrate has no such effect. At 22 degrees C, the effect of NGF on neuroblastoma substrate adhesion is observable within 5 minutes and persists for 2 hours; treatment of the KA line with NGF at 37 degrees C for 24 hours results in a more persistent enhancement of cell adhesion. Furthermore, both SY5Y and KA exhibit different morphologies when challenged with NGF, dBcAMP, or sodium butyrate. This study suggests that NGF and cyclic AMP do not share a common mechanism of action, but can in fact interact antagonistically in an adrenergic like neuroblastoma model system. Furthermore, the results suggest that increased cellular adhesiveness may not be an obligatory prerequisite for neurite extension by neuroblasts in development.

Bucladesine↗
PubMed1982

Coordinate regulation of synthesis of ribosomal proteins during encystation of Acanthamoeba castellanii.

The synthesis of ribosomal proteins has been examined during growth and encystment of Acanthamoeba castellanii. Cells have been radiolabelled with [35S]methionine and ribosomal proteins have been extracted either from ribosomes or from total cell extracts. The results show that there is less synthesis of ribosomal proteins relative to total cell proteins soon after transfer of growing cells into non-nutrient medium, suggesting that the synthesis of all ribosomal proteins is under coordinate control. Furthermore, synthesis of ribosomal RNA and ribosomal proteins seems to be regulated coordinately, since within 1 h there is 70-80% decline in synthesis of both. Translation of total RNA in vitro indicates that the relative decrease in the synthesis of ribosomal proteins during development is not only due to a relative decrease in the content of ribosomal protein mRNA. However, a considerable (about 10-fold) and coordinate decrease in the relative content of ribosomal protein mRNA occurs during encystment. These data suggest a difference in the control of the synthesis of total proteins and ribosomal proteins as well as in the regulation of the content of total mRNA and ribosomal protein mRNA. The comparison of patterns of ribosomal proteins indicates that during development no qualitative changes occur. The content of one protein of the small ribosomal subunit is low in growing cells and increases during encystation. Since the differences in the concentration of this protein are neither due to changing levels of the corresponding mRNA nor to changing rates of synthesis, changing affinities of this protein to ribosomes in vivo are suggested.

Amoeba↗
PubMed1977

[Classical conditioning of agonistic behavior in the Syrian golden hamster (Mesocricetus auratus Waterhouse)].

Nine different reactions of unconditioned agonistic behavior of golden hamsters (Mesocricetus auratus Waterhouse) which could be elicited by an air blow (UCS) were classically conditioned at a sound of a xylophone (tone g), a previously neutral stimulus. Tone g (CS) was paired with UCS for a different number of trials/day. In all animals exposed to over 20 pairings/day components of the agonistic behavior were brought under the control of CS, but it was not possible to predict which one of the agonistic reactions would appear. Most of the animals generalized and also showed conditioned reactions (CR) when presenting tone c' instead of tone g. When utilizing a differential conditioning procedure the animals learned to discriminate between the different tones. Extinction of CR at tone g was reached after an individually different number of trials.

Acoustic Stimulation↗