bluuebunny/crossref_metadata_2025 huggingface dataset:
Measuring drift during a receding flood: Results from an Austrian Mountain Brook (Ritrodat‐Lunz)
Authors: Tockner K. , Waringer J. A.
Published: February 2007

The drift of organisms and large particulate organic matter >200 μm (LPOM) was investigated during a single receding flood event from 16 to 23 June 1989 in a second order, calcareous, alpine, gravel brook. Starting with the peak level of the hydrograph, which was well above bankfull level, sampling lasted for five days (= 8 sampling dates). Between four and eight replicates were taken at each sampling date.

No significant differences (P < 0.05) could be detected in the proportion of the main aquatic taxa (excluding miscellaneous taxa) drifting during above versus below bankfull water levels. However, terrestrial taxa were significantly (P < 0.05) over‐represented (23–25% of the total) at flood peak and a small secondary flood peak four days later. In addition, aquatic taxa which normally are scarce in drift samples at the Seebach (e.g. oligochaetes, ostracods) were abundant during the receding main flood event.

Above bankfull stage (water level ⩾ 70 cm), animal drift densities were significantly (P < 0.01) and up to 22‐times higher (e.g. 45.6 individuals m−3) than during baseflow (e.g. 2.1 individuals m−3). Below bankfull stage, drift densities remain constant, independent of water discharge (Student‐Newman‐Keuls test; P < 0.01). In LPOM drift, this ratio was nearly 100: 1, with drift values ranging from 1.83 g dry weight m−3 at flood peak to 0.02 g dry weight m−3 at baseflow. Drift densities of animals and LPOM exhibited a positive exponential relationship with water level.

Drift rates of anmimals and LPOM ranged from 3200700 individuals and 148.9 kg dry weight per hour at flood peak to 17440 individuals and 0.2 kg dry weight per hour at baseflow. During a single receding flood (water level ⩾ bankfull) significantly more organisms and LPOM were transported than during a whole year at baseflow discharge.
Changes in the lower trophic levels as a consequence of the level of fish manipulation in the ponds
Authors: Tátrai István , Oláh János , Paulovits Gábor , Mátyás Kálmán , Kawiecka Barbara J. , Pekár Ferenc
Published: February 2007

Cyprinid fish of different mature age classes (3+ ‐4+) and stocks (100, 300 and 500 kg/ha) were introduced into each of three experimental ponds with area of 0.3 ha (average depth ca 1.7 m) while the fourth pond was left free of fish. Bream (Abramis brama L.), white bream (Blicca bjoerkna L.) and roach (Rutilus rutilus L.) made up 75% of the total cyprinid biomass, with wild carp (Cyprinus carpio L.) as the remaining 25%. The introduced fish spawned successfully.

The high (above 300 kg/ha) planktivorous and benthivorous fish stocks resulted in several qualitative and quantitative alterations of the food chain structure in our simulation pond experiments. These alterations must primarily be assigned to changes caused by both the zooplanktivory and benthivory nature of the stocked fish populations. At the higher levels of fish biomass, Secchi depth was influenced significantly by chlorophyll‐a concentration. Most of the variance in suspended solids concentration could be explained by the biomass ratio of the mature benthivorous fish. There was a clear shift in algal cell size in the ponds with the higher fish stocks: ponds with more fish had larger cells later in the summer. The relative influence of young cyprinid fish on crustaceans species composition and biomass, and mature populations on benthic fauna abundance and biomass, was sufficiently greater at higher (300–500 kg/ha) fish stock rates.
The hyporheic zone: Hydrogeological and geochemical study of a stream in the pyrenees mountains
Authors: Rouch Raymond , Mangin Alain , Bakalowicz Michel , D'Hulst Dominique
Published: February 2007

The hydrogeological and geochemical characteristics of the hyporheic zone were studied for a year on a 30 m2 site within a stream in the Pyrenees Mountains. This included the drawing of potentiometric maps, measuring hydraulic conductivity and porosity, and the monthly analysis of major chemical elements in water samples.

Use of the combined data led to the clarification of certain aspects of the characteristics, functioning and development of the hyporheic zone.

Even though the area studied lies in a zone of groundwater recharge, the direct vertical exchange between surface‐ and groundwater does not seem to be determinant in the potentiometric and chemical development of the area. However, the state of reserves, which can be reduced or reconstituted, seems to play an essential role in flow dynamics, and thus of the chemistry of this area. Flow dynamics in the hyporheic zone apparently are of the longitudinal‐transversal type, related to the local stream morphology.

The results show how difficult it is to define the hyporheic zone in a structural sense, even though the zone represents an entity that is clearly characterized by specific and identifiable dynamics.
Factors that Control the Species Composition of Freshwater Phytoplankton, with Special Attention to Nutrient Concentrations
Authors: Aakanishi Masami , Monsi Masami
Published: February 2007

Variations of species composition and population size of planktonic algae were studied in relation to the different nutrient levels in a eutrophic pond and an oligotrophic lake. The results obtained were discussed in comparison with the changes in photosynthesis and chlorophyll of several algal populations cultured under different nutrient conditions. As based on unialgal culture experiments two types of algae (the Chlorella‐type and the Melosira‐type) could be distinguished with regard to variations of photosynthesis and chlorophyll in response to different nutrient levels. Distribution of the Chlorella‐type algae may be confined to eutrophic waters, while the Melosira‐type algae can be distributed widely in waters from oligotrophic to eutrophic.
An Evaluation of the Effects of Environmental Variables on Marine Plankton Primary Productivity by Multivariate Regression
Authors: Hameedi M. Jawed
Published: February 2007

Stepwise multiple regression analysis has been used to evaluate the relative importance of environmental variables for primary productivity in oceanic areas off Washington and Oregon, USA. Special emphasis has been placed on the area affected by the Columbia River plume. In the plume, a large proportion of the total variability in primary productivity data is explained by only four variables: chlorophyll a, nitrate, depth of the photic zone, and temperature. In ambient sea water, the significant variables are salinity, temperature, solar radiation of the previous day, vertical stability in the upper 100 m, and phosphate. Analysis of the combined data indicates that, in the spring, primary productivity depends on chlorophyll a concentration alone. The results are explained from the biological and physical points of view. The usefulness of multiple regression analysis for marine ecosystem studies appears to be limited.
Some Observations on the Influence of Salinity on Photosynthetic Activity and Chloride Ion Loss in Several Seaweeds
Authors: Ohno Masao
Published: February 2007

The photosynthetic rates of Enteromorpha intestinalis, Fucus vesiculosus and Laminaria saccharina from the Baltic Sea were measured in different salinity range of Medium A (with NaHCO3) and Medium B (without NaHCO3). Photosynthetic activity in Medium A showed higher values than those in Medium B. The materials pretreated for one day showed a higher O2 output than those untreated at almost every salinity range. In a chloride loss experiment the pretreated thalli of Porphyra umbilicalis, Fucus vesiculosus and Laminaria digitata were placed for a three minute period in distilled water. The excreted chloride ion content showed a higher value in sublittoral species after hypotonic and hypertonic treatment than in intertidal species.
Cercaria orospinosa Encountered in the Snail Melanopsis praemorsa L. from a Mountain Stream in Turkey
Authors: Tareen Inam U.
Published: February 2007

Cercaria orospinosa is the only cercaria shed by Melanopsis praemorsa snails in Savanda stream, Turkey. Magnitude of infestation of snails by this cercaria was correlated with size of the snails and strength of the water current. The highest degree of infestation occurred in June, while in winter it was reduced to zero. The cercariae were released from rediae, which were found in the hepatopancreas of the snails.
Estimating Competition in Cladocerans Using Data on Dynamics of Clutch Size and Population Density
Authors: Gnauck A. , Matveev Vladimir
Published: February 2007

Negative correlations between clutch size and population density are proposed to be considered as indices of intra‐ and interspecific competition in cladocerans if they are revealed while analyzing population dynamics and clutch size and time lags are taken into account. The proper correlation analysis of summer populations of Diaphanosoma brachyurum, Bosmina coregoni, Daphnia cucullata and D. galeata from mesotrophic Lake Glubokoye (Moscow Region) in 1975, 1978, and 1979 indicates the important role of competition of both types for the community studied. High niche overlap in food and space in the four populations was also observed.
Degradation of Macromolecular Organic Compounds in a Tropical Lagoon (Ciénaga Grande, Colombia) and its Ecological Significance
Authors: Hoppe Hans‐Georg , Gocke Klaus , Zamorano Doris , Zimmermann Reinhard
Published: February 2007

Primary production and decomposition of organic substances were investigated in a tropical lagoon during the rainy season. Production and mineralization were measured using the oxygen method. Total bacteria numbers and biomasses were estimated with epifluorescence microscopy, and the enzymatic degradation capacity of model substrates was determined photometrically. These parameters were measured in the water and sediment of the lagoon itself and also in its effluents and incoming waters. The aim of the study was to determine the sites of highest microbial activity in the lagoon and to compare its activity with other coastal water bodies. Since the shallow water lagoon contains a large amount of particulate matter, it was of special interest to study the degradation of this material and its influence on the microbial population. It was found that up to 14 % of the bacteria colonized the particles and that 62 % of the respiration originated in the particle fraction >8 μm. Highest exoenzymatic activities were measured in the sediment and water of the mangrove belt. It is concluded that decomposition and conditioning of particulate organic matter play dominant roles in the recycling of organic carbon in the lagoon.
A Study of the Chromatiaceae in a Saline Meromictic Lake in Saskatchewan, Canada
Authors: Parker R. D. , Hammer U. T.
Published: February 2007

Lamprocystis roseopersicina was found to be the dominant phototrophic bacterium in meromictic Deadmoose Lake. Using carbon‐14 it was determined that phototrophic bacteria fixed 14.3 g C m−2 year−1, 17.1 % of the total limnetic primary production. Experiments indicated low light intensities (X = 8.87 × 10−2 cal cm−2hr−1) to be the most important factor limiting bacterial production. Lamprocystis was shown to be capable of photoorganoheterotrophic uptake of glucose.
Chitosan‐phosphorylated chitosan polyelectrolyte complex hydrogel as an osteoblast carrier
Authors: Li Quan‐Li , Chen Zhi‐Qing , Darvell Brian W. , Liu Lai‐Kui , Jiang Hong‐Bing , Zen Quan , Peng Qian , Ou Guo‐Min
Published: February 2007

To simulate extra‐cellular matrix, a novel three‐dimensional scaffold of polyelectrolyte complex (PEC) hydrogel as an osteoblast carrier was synthesized. First, chitosan, a natural glycosaminoglycan, was modified by phosphorylation to obtain a water‐soluble phosphorylated chitosan (P‐content: 10.7 mass%). The PEC hydrogel was then formed from equal volumes of 0.173 mass% phosphorylated chitosan in water and 1 mass% chitosan in 1% (V/V) acetic acid solution. Rat osteoblasts were seeded in the hydrogel. The PEC hydrogel had a three‐dimensional hierarchically‐porous structure and good cytobiocompatibility for osteoblasts in vitro. It is concluded that the PEC hydrogel is a promising material as an osteoblast carrier. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 2007
Factors related to contraction and mechanical strength of collagen gels seeded with canine endotenon cells
Authors: Chen Meng‐Yi , Sun Yulong , Zhao Chunfeng , Zobitz Mark E. , An Kai‐Nan , Moran Steven L. , Amadio Peter C.
Published: February 2007

Fibroblasts can construct a hydrated collagen lattice to a tissue‐like structure that is greatly influenced by initial culture conditions. The purpose of this study was to investigate the effects of cell concentration and collagen concentration on the contraction kinetics and mechanical properties of resultant endotenon‐derived fibroblast‐seeded collagen lattice. The experiment was designed to evaluate the effect of cell concentration (0, 0.25, 0.5, and 1.0 ××××× 106 cells/mL) and collagen concentration (0.5, 1.0, 1.5, and 2.0 mg/mL). Collagen lattice contraction was recorded for 42 days, after which time the lattices were mechanically tested. The collagen lattices seeded with higher initial cell concentration had a shorter contraction lag phase (p < 0.01), and exhibited a higher ultimate stress (p < 0.01) and instantaneous and equilibrium modulus (p < 0.01) than those seeded with a lower initial cell concentration. The collagen lattices cultured with a lower initial collagen concentration also had a shorter contraction lag phase, and exhibited greater instantaneous and equilibrium modulus (p < 0.01) than those cultured with higher initial collagen concentration. The collagen lattices of initial 0.5 mg/mL collagen concentration had the highest value of ultimate stress (p < 0.03). © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 2007
Implementation of π‐π interactions in molecular dynamics simulation
Authors: Yuki Hitomi , Tanaka Yoshikazu , Hata Masayuki , Ishikawa Hidenori , Neya Saburo , Hoshino Tyuji
Published: February 2007

No explicit π‐π interaction term has been incorporated in the conventional molecular dynamics (MD) simulation programs in spite of its significant role in the folding of biomolecules and the clustering of organic chemicals. In this article, we propose a technique to emphasize the effect of π‐π interactions using a function of energy and implement it into an MD simulation program. Several trial calculations show that the π‐π incorporated program gives improved results consistent with experimental data on atom geometry and has no unfavorable interference with the conventional computational framework. This indicates an importance of the explicit consideration of π‐π interactions in MD simulation. © 2007 Wiley Periodicals, Inc.J Comput Chem 2007
Performance of mentally retarded forensic patients on the test of memory malingering
Authors: Simon Michael J.
Published: February 2007

The utility of the Test of Memory Malingering (TOMM) with mentally retarded forensic patients was assessed. Twenty‐one adjudicated forensic inpatients, who had been diagnosed with mental retardation, were administered the TOMM. The majority of these patients also suffered from an Axis I mental disorder. The participants attained a mean score of 48.7 on Trial 2, with only 1 participant scoring below the standard cutoff for malingering (i.e., 45). The participants attained a mean score of 49.4 on the Retention Trial, with no participants falling below the cutoff for malingering. The results clearly indicate that mildly retarded forensic patients can perform well on the TOMM. The findings provide evidence that the TOMM can be used in the assessment of mildly retarded criminal defendants with little fear of obtaining false indications of malingering. © 2007 Wiley Periodicals, Inc. J Clin Psychol 63: 339–344, 2007.
Differential health effects of written processing of the experience of a surgical operation in high‐ and low‐risk conditions
Authors: Solano Luigi , Pepe Luisa , Donati Valentina , Persichetti Stefano , Laudani Guido , Colaci Andrea
Published: February 2007

The aim of this study was to assess the effects of the writing technique on postoperative course in interaction with different levels of risk. Participants were 40 urologic inpatients waiting to undergo transurethral resection of the prostate, with different levels of surgical risk as assessed with the Goldman Preoperative Risk Index (L. Goldman et al., 1978). Only 20 participants wrote for 3 days about the experience of being in the hospital. Measures were days of stay in the hospital after the operation, the Symptom Check List (SCL‐90; L. R. Derogatis, 1977; Italian version: G. Magni, C. Messina, D. De Leo, A. Mosconi, & M. Carli, 1983) scores, and a medical evaluation of postoperative course. A significant positive effect of writing on all three dependent variables emerged only in low‐risk participants. High‐risk writing participants showed a nonsignificantly worse postoperative course on all parameters than did high‐risk nonwriting participants. In highly stressful conditions, writing therefore should be employed only with caution. © 2007 Wiley Periodicals, Inc. J Clin Psychol 63: 357–369, 2007.
Powerful spin in the conclusion of wampold et al.'s re‐analysis of placebo versus no‐treatment trials despite similar results as in original review
Authors: Hróbjartsson Asbjørn , Gøtzsche Peter C.
Published: February 2007

B. E. Wampold, T. Minami, S. C. Tierney, T. W. Baskin, and K. S. Bhati (2005) re‐analyzed trials included in our systematic review of randomized clinical trials that compared placebo with no treatment (A. Hróbjartsson & P. C. Gøtzsche, 2001). Based on 11 trials, B. E. Wampold et al. concluded that “ … the placebo effect is robust” (p. 850). We (2001) concluded, based on 130 trials, that “we found little evidence in general that placebos have powerful clinical effects” (p. 1599). In this commentary, we examine the reasons for this discrepancy. For trials with continuous outcomes, our analyses (82 trials) and that of B. E. Wampold et al. (5 trials) resulted in pooled standardized mean differences that were small and essentially identical: −0.28 (95% confidence interval = −0.38 to −0.19) versus −0.29 (95% confidence interval = −0.52 to −0.06). There was considerable risk of bias (e.g., reporting bias, sample‐size bias). Similarly, for trials with binary outcomes, our analysis (32 trials) and that of B. E. Wampold et al. (6 trials) found no statistically significant pooled effect of placebo interventions and were essentially identical: relative risk 0.95 (95% confidence interval = 0.88–1.02) versus odds ratio 0.99 (95% confidence interval = 0.81–1.23). Thus, B. E. Wampold et al.'s conclusion was not substantiated by their data, and is best characterized as powerful spin. © 2007 Wiley Periodicals, Inc. J Clin Psychol 63: 373–377, 2007.
Contingency table techniques for three dimensional atom probe tomography
Authors: Moody Michael P. , Stephenson Leigh T. , Liddicoat Peter V. , Ringer Simon P.
Published: February 2007

A contingency table analysis procedure is developed and applied to three dimensional atom probe data sets for the investigation of fine‐scale solute co‐/anti‐segregation effects in multicomponent alloys. Potential sources of error and inaccuracy are identified and eliminated from the technique. The conventional P value testing techniques associated with χ2 are shown to be unsatisfactory and can become ambiguous in cases of large block numbers or high solute concentrations. The coefficient of contingency is demonstrated to be an acceptable and useful basis of comparison for contingency table analyses of differently‐conditioned materials. However, care must be taken in choice of block size and to maintain a consistent overall composition between experiments. The coefficient is dependent upon block size and solute composition, and cannot be used to compare analyses with significantly different solute compositions or to assess the extent of clustering without reference to that of the randomly ordered case. It is shown that as clustering evolves into larger precipitates and phases, contingency table analysis becomes inappropriate. Random labeling techniques are introduced to infer further meaning from the coefficient of contingency. We propose the comparison of experimental result, μexp, to the randomized value, μrand, as a new method by which to interpret the quantity of solute clustering present in a material. It is demonstrated that how this method may be utilized to identify an appropriate size of contingency table analysis blocks into which the data set is partitioned to optimize the significance of the results. Microsc. Res. Tech., 2007. © 2007 Wiley‐Liss, Inc.
Visualization of hemodynamics in intracranial arteries using time‐resolved three‐dimensional phase‐contrast MRI
Authors: Yamashita Shuhei , Isoda Haruo , Hirano Masaya , Takeda Hiroyasu , Inagawa Shoichi , Takehara Yasuo , Alley Marcus T. , Markl Michael , Pelc Norbert J. , Sakahara Harumi
Published: February 2007

Purpose

To visualize the hemodynamics of the intracranial arteries using time‐resolved three‐dimensional phase‐contrast (PC)‐MRI (4D‐Flow).

Materials and Methods

MR examinations were performed with a 1.5T MR unit on six healthy volunteers (22–50 years old, average = 30 years). 4D‐Flow was based on a radiofrequency (RF)‐spoiled gradient‐echo sequence, and velocity encoding (VENC) was performed along all three spatial directions. Measurements were retrospectively gated to the electrocardiogram (ECG), and cine series of three‐dimensional (3D) data sets were generated. The voxel size was 1 × 1 × 1 mm, and acquisition time was 30–40 minutes. 4D data sets were calculated into time‐resolved images of 3D streamlines, 3D particle traces, and 2D velocity vector fields by means of flow visualization software.

Results

We were able to see the 3D streamlines from the circle of Willis to the bilateral M2 segment of the middle cerebral arteries (MCAs). Time‐resolved images of 3D particle traces also clearly demonstrated intracranial arterial flow dynamics. 2D velocity vector fields on the planes traversing the carotid siphon or the basilar tip were clearly visualized. These results were obtained in all six volunteers.

Conclusion

4D‐Flow helped to elucidate the in vivo 3D hemodynamics of human intracranial arteries. This method may be a useful noninvasive means of analyzing the hemodynamics of intracranial arteries in vivo. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Age dependence of cerebral perfusion assessed by magnetic resonance continuous arterial spin labeling
Authors: Biagi Laura , Abbruzzese Arturo , Bianchi Maria Cristina , Alsop David C. , Del Guerra Alberto , Tosetti Michela
Published: February 2007

Purpose

To study the normal dependence of cerebral perfusion changes on age, to measure values of perfusion early in life, and to create a reference dataset.

Materials and Methods

Perfusion maps were collected from a total of 44 healthy subjects (from four to 78 years old) using the arterial spin labeling (ASL) technique. The population was retrospectively divided into three age groups: children, teenagers, and adults. For each group, mean values of cerebral blood flow (CBF) were calculated in gray matter (GM) and white matter (WM). Results were compared across the three different age groups.

Results

CBF values decreased with age (97 ± 5 mL/100 g/minute in GM and 26 ± 1 mL/100 g/minute in WM for the children, GM 79 ± 3 mL/100 g/minute and WM 22 ± 1 mL/100 g/minute for the teenagers, and GM 58 ± 4 mL/100 g/minute, WM 20 ± 1 mL/100 g/minute for the adults). The quantitative results suggest a rapid drop, rather than a gradual decrease, in cerebral perfusion between children and adult subjects, especially in the GM. This step in CBF occurs during adolescence, at approximately the 16th year of age.

Conclusion

ASL is a practical and quantitative technique suitable for perfusion measurement in children as well as adults. Perfusion measurements with ASL appear sensitive to neurophysiological changes occurring during brain maturation. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Perinatal kynurenine 3‐hydroxylase inhibition in rodents: Pathophysiological implications
Authors: Ceresoli‐Borroni Gianpiera , Guidetti Paolo , Amori Laura , Pellicciari Roberto , Schwarcz Robert
Published: February 2007

The kynurenine pathway (KP) of tryptophan degradation contains three neuroactive metabolites: the neuroinhibitory agent kynurenic acid (KYNA) and, in a competing branch, the free radical generator 3‐hydroxykynurenine (3‐HK) and the excitotoxin quinolinic acid (QUIN). These three “kynurenines” derive from a common precursor, L‐kynurenine, and are recognized for their role in brain physiology and pathophysiology. Inhibition of kynurenine 3‐hydroxylase, the enzyme responsible for 3‐HK formation, shifts KP metabolism in the mature brain toward enhanced KYNA formation. We now tested the cerebral effects of kynurenine 3‐hydroxylase inhibition in immature rodents. Rat pups treated with the kynurenine 3‐hydroxylase inhibitor UPF 648 (30 mg/kg, i.p.) 10 min after birth showed substantial increases in cerebral and liver kynurenine and KYNA levels up to 24 hr later, whereas 3‐HK and QUIN levels were simultaneously decreased. Administered to pregnant rats or mice on the last day of gestation, UPF 648 (50 mg/kg, i.p.) produced qualitatively similar changes (i.e., large increases in kynurenine and KYNA and reductions in 3‐HK and QUIN) in the brain and liver of the offspring. Rat pups delivered by UPF 648‐treated mothers and immediately exposed to neonatal asphyxia showed further enhanced brain KYNA levels. These studies demonstrate that acute kynurenine 3‐hydroxylase inhibition effectively shifts cerebral KP metabolism in neonatal rodents toward increased KYNA formation. Selective inhibitors of this enzyme may therefore provide neuroprotection in newborns and will also be useful for the experimental evaluation of the long‐term effects of perinatal KP impairment. © 2007 Wiley‐Liss, Inc.
Regulatory properties of 3‐deoxy‐D‐arabino‐heptulosonate‐7‐phosphate synthase isozymes from Candida maltosa
Authors: Bode R. , Melo C. , Birnbaum D.
Published: February 2007

The first step in the biosynthesis of aromatic amino acids by Candida maltosa was catalysed by two isozymes of 3‐deoxy‐d‐arabino‐heptulosonate 7‐phosphate (DAHP) synthase. The formation of which was constitutive. The phenylalanine‐sensitive and the tyrosine‐sensitive DAHP synthases were partially purified by hydroxylapatite chromatography and several properties of the separated isozymes were studied. Both enzymes showed a molecular weight of 90,000. The Km‐values of the tyrosine‐sensitive DAHP synthase were 0.20 mm for erythrose‐4‐phosphate (E‐4‐P) and 0.50 mm for phosphoenolpyruvate (PEP). Inhibition of this isozyme reaction by l‐tyrosine was competitive with respect to E‐4‐P (Ki = 0.028 mm) and non‐competitive with respect to PEP. The Km‐values of the phenylalanine‐sensitive DAHP synthase were estimated to be 0.65 mm for E‐4‐P and 0.63 mm for PEP; a Ki of 0.097 mm was obtained for l‐phenylalanine. A number of tyrosine and phenylalanine analogues and biosynthetic intermediates also inhibited the two isozyme reactions. For example, we observed a strong inhibitory effect of p‐hydroxyphenylpyruvate on the tyrosine‐sensitive DAHP synthase and of phenylpyruvate on the phenylalanine‐sensitive isozyme. Prephenate and arogenate had a less pronounced effect on the phenylalanine‐sensitive DAHP synthase.
Auswirkungen von Mutanteninduktion und Protoplastenfusion auf den DNA‐ und Proteingehalt vonPichia guilliermondii
Authors: Büttner Martina , Klinner U. , Birnbaum D. , Böttcher F.
Published: February 2007

The DNA content per cell of two tested auxotrophic mutants ofPichia guilliermondiiwas diminished in comparison to their wild‐type strains. After protoplast fusion between these mutants the majority of hybrids did not show the expected amount of DNA. In some hybrids it was only slightly higher than in the wild‐type strains, although heterozygosity for markers of three chromosomes could be established.

The protein content per cell of most strains was positively correlated with the DNA content, but generally more affected as the DNA content by the induction of mutations and protoplast fusion. The protein/DNA ratio of the two mutants was strongly reduced, while this ratio was somewhat enhanced in one of the hybrids in comparison to the wild‐type strains and the majority of hybrids. Apparently, the reduced protein content per cell in the mutants seemed to be partially compensated in the hybrids.
Einfluß von Phosphat und Inhibitoren der Proteinsynthese auf das Wachstum und die Tentoxinbildung von Alternaria alternata (Fr.) Keissler
Authors: Edel B. , Brückner B. , Hänel I. , Tröger R.
Published: February 2007

The synthesis of a phytotoxic substance, tentoxin, by Alternaria alternata (Fr.) Keissler is negatively controlled by inorganic phosphate. We show here that the influence of phosphate on the production of this secondary metabolite is time‐dependent. By using inhibitors of protein synthesis (p‐fluorphenylalanine, cycloheximide) together with a resuspension technique, attempts were made to find out when the enzymes responsible for tentoxin synthesis are formed.
Influence of nourseothricin on growth and secondary metabolism of Streptomyces noursei JA 3890b
Authors: Röder B. , Plonka G. , Bormann E. J. , Gräfe U.
Published: February 2007

The nourseothricin‐producing S. noursei strain JA 3890 b possessed a high degree of resistance to its own antibiotic when grown in submerged cultures started from mycelium samples as inocula. In contrast, both the outgrowth of spores and the development of surface colonies from mycelium samples were severely inhibited in the presence of relatively low concentrations of nourseothricin, suggesting that the producer organism is susceptible to the autotoxic metabolite in particular stages of its development. Nourseothricin production by submerged cultures has been found to be independent of negative feedback regulation by the antibiotic.
Conditions for the exopolysaccharide synthesis from n‐hexadecane by an oil‐positive bacterium 437
Authors: Wang X. Y. , Schwartz W.
Published: February 2007

Suitable conditions for exopolysaccharide synthesis from n‐hexadecane by the oil‐positive bacterium were: NaNO3 1.25–1.50 g, Na2HPO4 · 2 H2O 0.5 g, K2HPO4 0.5 g, MgSO4 · 7 H2O 0.5 g, H3PO4 (85%) 0–0.5 g, CaCl2 · 2 H2O 0.05 g, FeCl3 · 6 H2O 0.02 g, aqua dest. 1 l, pH 7.0–7.5, n‐hexadecane 2.5–3.0% (w/v). Under these conditions the viscosity of the broth from culture shaken at 30°C for 10 days was as high as 5,000–6,000 cSt (45°C). After pelleting of the cells, 11–13 g/1 polysaccharide were obtained by ethanol precipitation.
The temperature profiles of growth, thermal death and ethanol tolerance of the cellobiose‐fermenting yeast Candida wickerhamii
Authors: Cabeça‐Silva Cecilia , Madeira‐Lopes A. , Van Uden N.
Published: February 2007

The temperature profiles of growth and thermal death of the cellobiose‐fermenting yeast Candida wickerhamii was associative with the initial maximum, final maximum, optimum and minimum temperatures for growth around 38°C, 31°C, 31°C and 3°C, respectively. Ethanol enhanced thermal death by increasing the entropy of activation (entropy coefficient 7.2 entropy units mol−1 l−1), shifted the supraoptimal part of the profile to lower temperatures without disrupting it and increased the minimum temperature for growth. The temperature profile of ethanol tolerance with respect to growth displayed a narrow temperature plateau (18–22°C) of maximum tolerance (limit 7.4%, v/v, ethanol) while the toxic effects of ethanol increased steeply on either side of the plateau.
Hybridization of yeasts by protoplast fusion: Attempts to polyploidize Pichia guilliermondii
Authors: Klinner U. , Böttcher F.
Published: February 2007

The DNA content of fusion hybrids of Pichia guilliermondii was not further increased by renewed fusions. Occasionally, the stabilized hybrids only contained approximately the DNA content of the corresponding wild‐type strain. Investigation of the early events after fusion revealed spontaneous mitotic segregation with a high frequency. The benomyl‐induced mitotic segregation pattern of the hybrid clones was not uniform. In some clones certain markers did not segregate any longer. This probably indicates the loss of the respective chromosome. The inability of P. guilliermondii fusion products to form stable hybrids with the expected high DNA content may be attributed to either the aneuploidy of the fusion partners or a specific mitotic apparatus of this yeast.
Effektor‐ und Precursorfunktion von Mannose‐6‐phosphat, Mannose‐l‐phosphat, UDP‐N‐acetylglucosamin und Dolichylphosphat bei der mikrosomalen Biosynthese von Proteophosphomannan der SCP‐Hefe Candida maltosa H
Authors: Röber B. , Reuter G.
Published: February 2007

Microsomal preparations from protoplasts of the yeast Candida maltosa, which is able to assimilate n‐alkanes, were used as enzyme source to catalyse the nicorporation of radioactivity from guanosine diphosphate 14C‐mannose, 3H‐mannose‐6‐phosphate, 3H‐mannose‐1‐phosphate or uridine diphosphate N‐acetyl‐(14C‐glucose)‐glusosamine in a mannose polysaccharide. The reaction product was identified as yeast mannan by comparing the saccharides prepared by alkaline degradation and by acetolysis, with those from in vivo proteophosphomannan, obtained in structural investigations.

The enzyme preparation catalysed the formation of an almost unsubstituted α(1,6)‐linked mannan backbone from GDP‐Man. Man‐6P, dolichylphosphate and on the other hand UDP‐GNAc in the presence of ATP and dolichylphosphate are potent activators of the mannosyl transfer: α(1,3)‐(and α(1,3)‐) mannosyl transferases are activated by Man‐6P. Beside this Man‐6P is found to be a precursor for the incorporation of the first mannosyl (‐phosphate) unit in the side chain of a branched mannan and of the alkali‐labile bound oligosaccharides.

The data presented support the hypothesis that Man‐6P, not activated by GTP, is a second mannosyldonator in the biosynthesis of proteophosphomannan.
Studies on sugar isomerases of Lactobacillus sp.
Authors: Shukla G. L. , Prabhu K. A.
Published: February 2007

A culture of Lactobacillus sp. isolated from soil was found to contain glucose, xylose and ribose isomerase enzymes. Some of the factors affecting isomerase enzyme activities were studied with a view to isolate and purify the enzymes. Arsenate was not required in the enzyme reactions. At 10 mM concentrations sodium arsenate showed 65–70% inhibition of D‐glucose isomerase but did not affect D‐xylose and D‐ribose isomerases. At 5 mM concentrations EDTA showed 85–90% inhibition of D‐glucose and D‐ribose isomerases but not D‐xylose isomerase. Ca2+ ions showed inhibition of D‐glucose isomerase at a concentration of 1–2 mM, but inhibition could be reversed by increasing Mg2+ concentration in the enzyme reaction mixture. D‐Glucose enzyme production was maximal after 72 hrs of fermentation in shake flasks with Yamanaka medium containing glucose and xylose, and glucose isomerase activity in the culture increased up to 5–6 generations.

Heat treatment of ultrasonic crude extract and of whole bacterial cells in the presence of Co2+/Mg2+ ions gave insoluble fixed active D‐glucose isomerase enzyme devoid of D‐xylose and D‐ribose isomerase activities. About 40 units (μM/min) of D‐glucose isomerase activity per gram of dry cells were obtained in whole cell immobilization.
Inducible nature of the steroid 11‐hydroxylases in spores of Cunninghamella elegans (Lendner)
Authors: Jaworski A. , Sedlaczek L. , Dlugoński J. , Zajaczkowska Ewa
Published: February 2007

Spores harvested from steroid‐free media (non‐induced during sporogenesis), and used for cortexolone hydroxylation in the presence of cycloheximide to prevent enzyme synthesis during transformation produced cortexolone derivatives at a low rate: 4.85 ± 2.37 mg products per g dry weight per 6 hours.

Spores induced during sporogenesis and transformation formed the hydroxylation products at the rate 40.25 ± 6.25 mg/g d.wt./6 h, whereas spores induced only once — on the stage of sporogenesis or during transformation — produced them at the rate 15.28 ± 4.80 – 18.85 ± 4.48 mg/g·6 h.

The effectiveness of the hydroxylase induction during steroid transformation could be increased if spores pretreated with diluted KOH were used. This agent was shown to loosen the rigid structure of the spore envelopes, and to increase their permeability for the enzyme inducer. The similar could be shown with spores preincubated in a growth medium for 1–3 hours. Transformation rates of 51.34 mg/g·6 h and 68.82 mg/g·6 h were attained.
Gene expression at each stage of the life cycle of spore‐forming bacteria: Different sensitivity of transcription to antibiotics which act on DNA gyrase
Authors: Matsuda M. , Kameyama T.
Published: February 2007

Effects of antibiotics acting on DNA gyrase, novobiocin and nalidixic acid on RNA synthesis during germination, vegetative growth and sporulation of Bacillus subtilis were examined.

These drugs were relatively ineffective in inhibiting RNA synthesis of phase Gm 1 (5–15 min) during germination but effective in those of Gm 2 (15–40 min) and Gm 3 (40–60 min) during germination (Matsttda and Kameyama 1980).

No distinguishable inhibitory effects of RNA synthesis in B. subtilis Novritt mutant could be detected by novobiocin. Bna synthesis of Gm 2 and Gm 3 of this mutant was inhibited by nalidixic acid.

When novobiocin was added to exponential vegetative cell or sporulating cell culture at T0 and T1 stage, the rate of Bna synthesis was inhibited by 80% for 5 min following addition of the drug. However, Bna synthesis after T2 of sporulation became resistant toward novobiocin, as was the case at an early stage of germination.

RNA profiles from transcripts synthesized on administration of Nov suggested that the suppression of the synthesis of 23S and 16S rRNA is relatively greater than 4 to 5S RNA at the middle stage of germination and at vegetative growth stage in the presence of NOV.

Our present data suggest that DNA gyrase is involved in the regulation of gene transcription during middle and late phases of germination, vegetative growth and T0 and T1 of sporulation. The transcription during early phase of germination and sporulation after T2 may proceed independently of this enzyme.
Microbial side‐chain degradation of sterols
Authors: Kieslich K.
Published: February 2007

Apart from the broadly used diosgenin and some further natural compounds sterols gained an increasing importance as raw material for the synthesis of steroid drugs.

Parallel to the elucidation of the pathways of the enzymatic degradation of sterols technical processes were developed for a specific degradation of the side‐chain to useful primary products. A review is given on the present state of this field and the trends to further improvements.
Biochemical and genetic studies of a histidine regulatory mutant of Streptomyces coelicolor A3 (2)
Authors: Derkos‐Sojak Vlasta , Pigac Jasenka , Delić V.
Published: February 2007

The specific activities of three enzymes in a histidine regulatory mutant RF59 of Streptomyces coelicolor A3(2) resistant to the histidine analogue 1,2,4‐triazolealanine (TRA) were measured and compared to the activity of the wild type strain. The first enzyme of the histidine pathway, phosphorybosyl‐ATP‐pyrophosphorylase (PR‐ATP‐pyrophosphorylase), of mutant RF59 and the wild type was sensitive to allosteric inhibition by L‐histidine and hence feed‐back inhibition was not affected by mutation, although the specific activity in the mutant was 2.9 fold higher than in the wild type.

The other two enzymes coded by genes from the histidine operon were significantly derepressed. The enzyme D‐erythroimidazoleglycerol phosphate dehydrase (IGP‐dehydrase) in mutant RF59 had a 4.9 fold higher specific activity than in the wild type strain. The specific activity of the last enzyme of the pathway, histidinol‐dehydrogenase (Hol‐dehydrogenase), in the mutant was 4.7 fold derepressed compared to the wild type strain.

The results of genetic crosses revealed the mapping of RF59 regulatory mutation between argA1 and cysD18 on S. coelicolor chromosome, suggesting that the mutant RF59 is a regulatory mutant unable to fully repress genes of the histidine pathway.
Occurrence of squalene and dehydrosqualene in streptomycetes
Authors: Gräfe U. , Reinhardt G. , Hänel F. , Schade W. , Gumpert J.
Published: February 2007

Squalene, dehydrosqualene and related hydrocarbons were found to constitute an essential part of the neutral lipid fraction extracted from mycelia and membranes of S. hygroscopicus, S. griseus and S. noursei. In comparison with the fraction of the triglycerides, these terpenoid compounds failed to incorporate (U‐14C)‐acetic acid throughout pulse labelling experiments. This suggested that the pertinent precursors were formed via alternative routes, for instance by catabolising branched‐chain amino acids.
Nature and significance of microbial cometabolism of xenobiotics
Authors: Janke D. , Fritsche W.
Published: February 2007

Microbial cometabolism, i.e. “transformation of a non‐growth substrate in the obligate presence of a growth substrate or another transformable compound” (Dalton and Stirling 1982) is a whole‐cell phenomenon physiologically based on coupling of different catabolic pathways at the cellular level. It is frequently observed in transformation of xenobiotic non‐growth substrates by individual microbial species. Transformation processes of this type are usually mediated by appropriate nonspecific enzymes of the peripheric cellular metabolism able to modify a variety of substances other than their natural substrates.

The precise mechanisms of coupling between metabolism of xenobiotic non‐growth substrates and of particular additional carbon substrates may be different depending on the substrates and the microbial species involved. However, experimental data indicate that the primary function of the respective additional carbon substrates is to supply either energy, cofactors or metabolites for the different cellular events involved in the transformation process (e.g. uptake of the xenobiotic non‐growth substrate, functioning of appropriate degradative enzymes of the peripheric cellular metabolism).

Cometabolism of xenobiotics involves nothing special or novel from the standpoint of biochemistry. On the contrary, there are numerous examples where the turnover of particular natural compounds by certain aerobic or anaerobic microorganisms is essentially based on coupling of different catabolic pathways at the cellular level by transfer of hydrogen (i.e. reducing power) and/or energy between two or more enzymatic reactions. Synthetic chemicals which resist total degradation by individual microbial species may undergo mineralization due to complementary catabolic sequences mediated by certain multispecies microbial associations with cometabolic transformations being the initial steps.

Although taking place in certain natural habitats (e.g. rhizospheres, sewage), microbial cometabolism of xenobiotics in natural ecosystems occurs with slow rates since the respective cometabolizing populations are generally small and will not increase in number or biomass in response to the introduced chemicals. However, under conditions of axenic microbial cultures, high concentrations of biomass, and appropriate substrate mixtures cometabolism of synthetic chemicals may be a useful technique of considerable practical importance to accumulate biochemical products at high yields. In addition, cometabolic capabilities of wild‐type microorganisms may serve as a tool for the construction of microbial strains with a new degradative potential for recalcitrant xenobiotic compounds.
Biotest zum Nachweis von Hydroxamat‐Fe‐Chelatoren (Aerobactin)
Authors: Rabsch W. , Reissbrodt R.
Published: February 2007

Different Salmonella strains were tested for aerobactin production in a hydroxamate‐bioassay with the aerobactin indicator strain E. coli LG 1522. The majority of hospital strains of Salmonella typhimurium produce hydroxamate siderophore. On the other hand S. typhimurium strains belonging to phage type n. c. 1/72/n. c., biochemical type b from human and animal sources, were unable to produce this siderophore. Serotypes other than S. typhimurium for example the multi‐resistent S. wien hospital strains, which were isolated in western europe and in the GDR, can excreate hydroxamate siderophore. Plasmids pIE 528 and pIE 5 234 isolated from Salmonella hospital strains produce hydroxamate siderophore in the enterobactin negative Salmonella typhimurium‐strain enb‐7.

Thus, the hydroxamate bioassay may be a useful supplementary test for epidemiological strain characterization.
Parasexual process in the yeast Yarrowia lipolytica
Authors: Kurischko Cornelia
Published: February 2007

Genetic studies of several events of the life cycle of Y. lipolytica demonstrated that diploid strains were unstable and produced mitotic segregants by haploidization. A screening system was developed which enabled us to show that parasexual processes can take place in addition to the sexual life cycle. This haploidization occurred through aneuploid intermediates as was proven statistically by the deviations from the segregation pattern as well as by the segregation data of the clones.

The direction of the cross, was — with respect to the resistance to 2‐deoxyglucose of A‐ or B‐strain — not important for selection of mitotic segregants.
Surface hydrophobicity of plasmid‐carrying virulent Shigella flexneri and their avirulent variants
Authors: Seltmann G. , Tschäpe H. , Pál T.
Published: February 2007

Five pairs of strains of S. flexneri each differing in the colour of their colonies after growth on Congo red agar have been tested for their ability to cause keratoconjunctivitis in the guinea pig eye, for the presence of the 140 Md virulence plasmid, for the presence of the virulence marker antigen, and for their ability to adsorb to hydrophobic surfaces (cellulose nitrate filters and Phenyl Sepharose). The results suggest that the presence of the 140 Md virulence plasmid provides the bacterial surface with a rather high degree of hydrophobicity; exceptions have been found.
Effect of temperature on growth and protein turnover in Bacillus megaterium
Authors: Strnadová M. , Prasad R. , Kučerová H. , Chaloupka J.
Published: February 2007

The Arrhenius plot of the specific growth rate μ of an asporogenic mutant of Bacillus megaterium, growing in the range of 17–37 °C followed a straight line, whose slope was affected by the composition of the medium. The maximal μ was found at 40° C in all media tested and decreased rapidly above 42° C. The portion of protein degraded also followed a straight line but reached its maximal value at 45–47° C. Its slope was affected substantially by the composition of the medium; the mixture of amino acids suppressed protein degradation at temperature lower than 37° C. The extent of the short‐lived protein fraction, degraded with the half‐time of about 1 h, was mostly affected by both — the temperature and the medium. The amount of proteins degraded per one biomass doubling was almost constant up to 37° C but was affected by the composition of the medium. At higher temperatures it increased rapidly and reached values of 20–40% of pulselabelled proteins degraded per one cell cycle. The degradation of ethionine‐containing proteins was similarly dependent on the temperature but the extent of proteins degraded was increased.