bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrochemical Behavior of Some Thiotriazoles in Aqueous‐Alcoholic Media at GCE
Authors: Fotouhi Lida , Hajilari Fatemeh , Heravi Majid M.
Published: December 2002

An electrochemical study related to the electrooxidation of 4‐amino‐3‐thio‐5‐methyl‐1,2,4‐triazole (I), 4‐amino‐3‐thio‐5‐phenyl‐1,2,4‐triazole (II) and 3‐thio‐5‐phenyl‐1,2,4‐triazole (III), in 10% v/v methanol‐acetate buffer pH 4.6 has been performed. A variety of electrochemical techniques such as differential pulse voltammetry, cyclic voltammetry, double‐potential step chronoamperometry, rotating‐disk electrode voltammetry and coulometry, were employed to clarify that the mechanism of the electrode process follows the oxidation of thiol compounds. All the compounds exhibit similar redox behavior under the given conditions. They display one irreversible oxidation peak, which is diffusion controlled. From the plot of current function in cyclic voltammetry and the ratio of ic/ia less than one in double‐potential step chronoamperometry, it was established that these compounds undergo an one electron oxidation followed by a dimerization process involving the formation of disulfide derivative (EC mechanism). The pKa values were obtained by the dependence of limiting current and potential with in the wide pH interval. The transfer coefficients, the diffusion coefficients and rate constant of coupled chemical reaction were also reported. The substituent effects were also investigated.
Electrodes of Nontoxic Solid Amalgams for Electrochemical Measurements
Authors: Yosypchuk Bogdan , Novotný Ladislav
Published: December 2002

The preparation, activation and electrochemical pretreatment of electrodes based on nontoxic solid amalgams were described. Testing of metal solid amalgam electrodes (MeSAEs) proved their broad applicability in many respects, e.g., as to the range of working potentials and the level of background currents, well comparable with those of the hanging mercury drop electrode (HMDE). A regeneration of their surfaces before each measurements could be simply automatized using a PC‐controlled system providing a reasonable repeatability of voltammetric measurements down to 3% RSD. Combination with stripping techniques at accumulation times tac=300 s the detection limit amounted to the concentration level of 1 ppb Cu(II), Pb(II), Cd(II), Zn(II), etc. Best electrochemical properties were exhibited by the silver solid amalgam electrode (AgSAE). For example, polished AgSAE (p‐AgSAE), completely free of liquid mercury, proved satisfactory even at more negative potentials enabling the determination of Zn(II), Mn(II), IO$\rm{ {_{3}^{-}}}$, etc. Moreover, even better repeatability of mercury meniscus modified AgSAE (m‐AgSAE) was due to better quality and renewability of its surface. In many cases further testing confirmed that under appropriate conditions MeSAEs represent good, often cheaper and more users‐friendly alternatives to HMDE.
Msh2 deficiency increases the mutation frequency in all parts of the mouse colon
Authors: Zhang Shulin , Lloyd Ruth , Bowden Gregory , Glickman Barry W. , de Boer Johan G.
Published: December 2002

The Msh2 DNA mismatch repair gene is one of five genes implicated in the pathogenesis of hereditary nonpolyposis colorectal cancer (HNPCC). To address the possible mechanisms of the site‐specific occurrence of HNPCC, the effect of Msh2 deficiency on mutations in different parts of the colon was investigated using the BC‐1(lacI)/Msh2 double transgenic mouse. Compared to the Msh2+/+ mice, Msh2‐/‐ mice had an 8–9‐fold increase of mutation frequency (MF) in the lacI gene from the cecum and the proximal and distal colon. The mutational spectra were also significantly different between Msh2+/+ and Msh2‐/‐ mice, with a significant increase in the frequency of −1 frameshifts and G:C→A:T base substitutions in the repair‐deficient mice. However, in spite of the site‐specific predisposition of HNPCC in humans, we found no significant difference in the MF or mutation spectrum between the three parts of the colon in Msh2+/+, Msh2+/‐, or Msh2‐/‐ mice. In addition, 11 independent mutants harboring complex mutations within the lacI gene were recovered in the Msh2‐/‐ mice. Interestingly, while the Msh2+/‐ mice displayed an overall MF similar to that observed in the wild‐type mice, sequencing revealed a significantly different mutational spectrum between Msh2+/+ and Msh2+/‐ mice, mainly characterized by an increase in −1 frameshifts. Due to the prevalence of frameshift mutations in HNPCC patients, this haploinsufficiency effect of the Msh2 gene in safeguarding genomic integrity may have important implications for human carrier status. Environ. Mol. Mutagen. 40:243–250, 2002. © 2002 Wiley‐Liss, Inc.
Transmission of mutations in the lacI transgene to the offspring of ENU‐treated Big Blue® male mice
Authors: Barnett Lois B. , Tyl Rochelle W. , Shane Barbara S. , Shelby Michael D. , Lewis Susan E.
Published: December 2002

The purpose of the study was to determine: 1) if male germ cells of Big Blue® mice carrying newly induced mutations in the lacI transgene were effective in fertilization; 2) if offspring arising from such mutant sperm had the mutation in germ cells and multiple somatic tissues; and 3) how the frequency of mutants induced in the lacI transgene compared to the frequency induced in endogenous genes traditionally employed to study germ cell mutagenesis in mice. Male B6C3F1 mice hemizygous for the lambda/lacI transgene were treated weekly with 100 mg/kg body weight of the mammalian germ cell mutagen N‐ethyl‐N‐nitrosourea (ENU). The cumulative dose for each treated animal was 300 mg ENU/kg body weight. Ten weeks later the treated mice were mated to T stock females and the resulting offspring were screened for specific‐locus mutations at six loci affecting external appearance, as well as for mutations in the lacI transgene in multiple somatic tissues and germ cells. Five offspring carrying recessive specific‐locus mutations were observed among 597 offspring screened (mutant frequency = 139.6 × 10‐5 per locus). Four offspring carrying lacI mutations were observed among 280 offspring screened (mutant frequency = 35.7 × 10‐5 per locus (assuming 40 target loci)). Each of the four lacI mutant offspring carried a different mutation. Three of the mutations were A:T→G:C transitions and one a G:C→A:T transition. Consistent with the expectation that a mutation induced in a parental germ cell and transmitted to a conceptus would exist in every cell of the offspring, each mutant mouse had identical mutations in all somatic tissues sampled, as well as in its germ cells. These data provide preliminary evidence for the biological validity of assessing induced, heritable mutations using transgenic mice, without the need for generating an F1 generation. Environ. Mol. Mutagen. 40:251–257, 2002. © 2002 Wiley‐Liss, Inc.
Genotoxicity biomonitoring in regions exposed to vehicle emissions using the comet assay and the micronucleus test in native rodent Ctenomys minutus
Authors: Heuser Vanina D. , da Silva Juliana , Moriske Heinz‐Jörn , Dias Johnny F. , Yoneama Maria Lúcia , de Freitas Thales R.O.
Published: December 2002

Exposure to motor vehicle emissions represents an important concern for possible long‐term health effects. The present report describes: 1) the application and verification of the alkaline comet assay in Ctenomys minutus to detect the possible genotoxicity of automobile emissions; 2) a comparison of the comet assay results with peripheral blood micronucleus (MN) assay results performed in the same animals; and 3) the identification of agents involved in the responses and in the seasonal variation of the effects. Ctenomys minutus (Octodontidae‐Rodentia) were captured in two different fields from both sides of RS/030, a highway on the coastal plain of the Brazilian state of Rio Grande do Sul. Reference animals were obtained from a nearby field that was about 3 km distant from any road. By the end of this study, 123 rodents (73 females and 50 males) were live‐trapped. Our results indicate that there was an increase in cells with DNA damage for C. minutus environmentally exposed to automobile emissions, as demonstrated by the alkaline comet assay, but there was no increase in micronucleated cells. The alkaline comet assay showed age and gender differences in the response. The comet assay results suggest that adult females are the principal population affected by air pollutants from vehicle emissions. Chemical data were also collected from areas exposed to automobile exhaust and these indicated that elevated levels of hydrocarbons, metals, and NO2 were associated with the elevated levels of damaged cells observed in the wild rodent C. minutus. Our results agree with previous data on engine and fuel components, where weak increases in damage for native rodents exposed to emissions have been observed. Other larger, controlled studies are needed to better understand how the metabolism of C. minutus affects its response to emission exposure. Environ. Mol. Mutagen. 40:227–235, 2002. © 2002 Wiley‐Liss, Inc.
Effects of heat shock protein 70 (Hsp70) on arsenite‐induced genotoxicity
Authors: Barnes J.A. , Collins B.W. , Dix D.J. , Allen J.W.
Published: December 2002

Arsenic, a human carcinogen, is genotoxic, although its mechanism(s) of action for tumorigenesis is not well understood. Among the toxicity‐related properties of this chemical are its clastogenic and aneugenic activities, as well as its capacity for inducing stress‐response in the form of elevated heat shock protein (HSP) expression. In the present study, we evaluated the effects of Hsp70 expression on arsenite (As)‐induced structural and numerical chromosome anomalies in human cells. Human MCF‐7 Tet‐off cells stably transfected with a pTRE/Hsp70‐1 transgene construct were used to regulate Hsp70 levels prior to in vitro As exposures. Separate cultures of relatively high vs. low Hsp70‐expressing cells were established. A cytokinesis block micronucleus assay with kinetochore immunostaining was used to detect micronuclei (MN) derived from chromosome breakage (K−MN) or loss (K+MN). These studies demonstrated significant increases in micronucleus frequencies in response to As following either a long exposure (5 or 10 μM for 46 hr), or short exposure (10 or 40 μM for 8 hr) protocol. Overall, the long protocol was more efficient in producing K+MN and cells with multiple MN. Overexpressing Hsp70 resulted in significant reductions in the percent of cells positive for MN for both the long and short As exposure protocols. Both K+ and K− types of As‐induced MN were lower in cells with elevated Hsp70 as compared to cells without overexpression of Hsp70. We conclude that the dose and duration of As exposure influence the type as well as amount of chromosomal alteration produced and that inducible Hsp70 protects against both the clastogenic and aneugenic effects of this chemical. Environ. Mol. Mutagen. 40:236–242, 2002. Published 2002 Wiley‐Liss, Inc.
Mutagenic activity of cisplatin in the lacZ plasmid‐based transgenic mouse model
Authors: Louro Henriqueta , Silva Maria J. , Boavida Maria G.
Published: December 2002

Cis‐diamminedichloroplatinum (II) (cisplatin) is a well characterized antitumor drug used for the treatment of a variety of human cancers. The cytotoxicity of cisplatin is mainly mediated through the formation of DNA adducts, which are also believed to be responsible for the secondary malignancies produced by the drug. The aim of this study was to determine the in vivo mutagenic activity of cisplatin in the lacZ plasmid‐based transgenic mouse model. The mutant frequency (MF) and the spectrum of mutations induced by cisplatin in the mouse liver were analyzed and compared to controls. The mean MF in the lacZ gene was increased 2‐fold in mice treated with a single 6 mg/kg body weight dose of cisplatin and sacrificed after 17 and 28 days (P = 0.001 and P < 0.0001). Restriction analysis and sequencing of mutant DNA showed that cisplatin was able to induce both large deletions and point mutations. A specific profile of base substitution and frameshift mutations was identified in treated mice, consisting primarily of G:C→A:T transitions at GpG and ApG sites, the preferential DNA binding sites of cisplatin, and single basepair deletions/insertions. The present results provide the first evidence that cisplatin has mutagenic activity in vivo and induces a characteristic pattern of mutations in the mouse liver. This mutagenicity may be responsible for its tumorigenic activity. Environ. Mol. Mutagen. 40:283–291, 2002. © 2002 Wiley‐Liss, Inc.
Induction of epithelial tumors in Drosophila melanogaster heterozygous for the tumor suppressor gene wts
Authors: Eeken Jan C.J. , Klink Ilse , van Veen Bert L. , Pastink Albert , Ferro Wouter
Published: December 2002

The imaginal disk cells of Drosophila have a cell cycle that is very similar to that of mammalian cells. Data concerning factors inducing tumors in these cells may directly relate to the risk of these factors for inducing cancer in humans. One of the genes involved in the regulation of cell cycle control is wts (warts), the Drosophila homolog of the mammalian tumor suppressor gene LATS1. The Drosophila wts mutations are recessive lethal. However, homozygous clones that arise in heterozygous flies in the imaginal disk cells lead to epithelial tumors, spectacular outgrowths visible on the cuticle of the adult. We have treated Drosophila larvae, heterozygous for wts, with the chemical mutagen MMS (methyl methanesulfonate) or with X‐rays and measured the appearance of epithelial tumors in the eclosing adult flies. This test is a variation of the well‐known Drosophila somatic mutation and recombination test (SMART), where mostly recessive markers have been used leading to visible phenotypes in the eyes and wings of the fly. We show that the sensitivity of this test is far greater than the comparable test system using the recessive eye marker white. Environ. Mol. Mutagen. 40:277–282, 2002. © 2002 Wiley‐Liss, Inc.
Overexpression of heme oxygenase‐1 (HO‐1) in V79 cells results in increased resistance to hyperbaric oxygen (HBO)‐induced DNA damage
Authors: Rothfuss Andreas , Speit Günter
Published: December 2002

Heme oxygenase (HO) catalyzes the rate‐limiting step in the oxidative degradation of heme to biliverdin. The isoform HO‐1 is inducible by a variety of agents causing oxidative stress and has been suggested to play an important role in cellular protection against oxidant‐mediated cell damage. Using treatment of cell cultures with hyperbaric oxygen (HBO) as a model for oxidative stress, we have shown an induction of HO‐1 in isolated human lymphocytes after a single HBO exposure and protection of these cells against DNA damage by subsequent oxidative stress. In contrast, V79 Chinese hamster cells showed neither a comparable adaptive protection nor an induction of HO‐1 after HBO exposure, which makes this cell line an attractive model system for a further characterization of HO‐1‐mediated protection. In the present study, we investigated whether overexpression of HO‐1 renders V79 cells more resistant to DNA damage induced by HBO. Transient transfection of V79 cells with a full‐length human HO‐1 cDNA resulted in a 2–3‐fold increase in HO‐1 protein levels. Comet assay experiments with and without FPG posttreatment for the determination of oxidative DNA base damage showed that HO‐1 overexpressing V79 cells were significantly protected against oxidative DNA damage induced by a single HBO exposure. Furthermore, HO‐1‐transfected cells exhibited a clearly reduced induction of micronulei after HBO treatment. Since the observed protective effects were abolished by cotreatment with the HO‐1 inhibitor tin‐mesoporphyrin, our study suggests that a low‐level overexpression of HO‐1 provides protection against oxidative DNA damage induced by HBO. Environ. Mol. Mutagen. 40:258–265, 2002. © 2002 Wiley‐Liss, Inc.
Evaluation of the clastogenic, DNA intercalative, and topoisomerase II‐interactive properties of bioflavonoids in Chinese hamster V79 cells
Authors: Snyder Ronald D. , Gillies Peter J.
Published: December 2002

Bioflavonoids are naturally occurring polyphenols with intriguing and varied therapeutic and chemoprotective activities generally ascribed to their antioxidant properties. However, many flavonoids have also been shown to be genotoxic in a variety of prokaryotic, eukaryotic, and in vivo systems. The mechanistic basis for this genotoxicity has not been fully elucidated, although structure–activity relationship studies have identified requisite flavonoid structural features. We utilized Chinese hamster V79 cells to evaluate the relationships between DNA intercalation ability, topoisomerase II interactions, reactive oxygen species (ROS) generation, and clastogenicity in a series of 14 bioflavonoids. Five of the flavonoids examined, luteolin, quercetin, genistein, apigenin, and acacetin, were strongly clastogenic. This clastogenicity was shown to require DNA intercalation (with the exception of genistein) and was substantially reduced by catalytic inhibitors of DNA topoisomerase II. The transition metals Cu(II) and Mn(II) formed chelates with and/or modified the structure and biological activity of some flavonoids but no consistent relationship could be demonstrated between metal reactivity and clastogenicity. There was no clear association between generation of ROS and clastogenicity. The data presented herein are consistent with a model in which the genotoxicity of most flavonoids arises via DNA intercalation and topo II poisoning, likely mediated through metabolism to flavonoid quinones. Interestingly, other flavonoids such as myricetin, daidzein, baicalein, fisetin, and galangin were catalytic topo II inhibitors, rather than poisons. These studies further validate the use of cell‐based approaches for detecting drug/topo II interactions and raise interesting questions relating to biological and chemical mechanisms of flavonoids. Environ. Mol. Mutagen. 40:266–276, 2002. © 2002 Wiley‐Liss, Inc.
Mouse lymphoma thymidine kinase gene mutation assay: Follow‐up International Workshop on Genotoxicity Test Procedures, New Orleans, Louisiana, April 2000
Authors: Moore Martha M. , Honma Masamitsu , Clements Julie , Harrington‐Brock Karen , Awogi Takumi , Bolcsfoldi George , Cifone Maria , Collard Deborah , Fellows Michael , Flanders Kathryn , Gollapudi Bhaskar , Jenkinson Peter , Kirby Paul , Kirchner Stephan , Kraycer Joann , McEnaney Stephen , Muster Wolfgang , Myhr Brian , O'Donovan Michael , Oliver Jo , Ouldelhkim Marie‐Claude , Pant Kamala , Preston Robert , Riach Colin , San Richard , Shimada Hiroyasu , Stankowski Leon F.
Published: December 2002

The Mouse Lymphoma Assay (MLA) Workgroup of the International Workshop on Genotoxicity Test Procedures held a second harmonization meeting just prior to the U.S. Environmental Mutagen Society Meeting in New Orleans, LA, in April 2000. The discussion focused on several important aspects of the MLA, including: 1) cytotoxicity measures and their determination, 2) use of a 24‐hr treatment, 3) the ability of the assay to detect aneugens, and 4) concentration selection. Prior to the meeting the group developed Microsoft Excel Workbooks for data entry. Ten laboratories entered their data into the workbooks (primarily as coded chemicals). The Excel Workbooks were used to facilitate data analysis by generating an extensive set of graphs that were evaluated by the meeting participants. Based on the Workgroup's previous agreement that a single cytotoxicity measure should be established for both the microwell and soft agar versions of the assay, the Workgroup analyzed the submitted data and unanimously agreed that the relative total growth (RTG) should be used as the cytotoxicity measure for concentration selection and data evaluation. The Workgroup also agreed that the various cytotoxicity measures should be calculated using the same methods regardless of whether the soft agar or microwell version of the assay was used. In the absence of sufficient data to make a definitive determination, the Workgroup continued to endorse the International Committee on Harmonization recommendation for the use of 24‐hr treatment and made some specific 24‐hr treatment protocol recommendations. The Workgroup recognized the ability of the MLA to detect at least some aneugens and also developed general guidance and requirements for appropriate concentration selection. Environ. Mol. Mutagen. 40:292–299, 2002. © 2002 Wiley‐Liss, Inc.
Extreme events controlling erosion and sediment transport in a semi‐arid sub‐andean valley
Authors: Coppus R. , Imeson A. C.
Published: December 2002

The importance of extreme events in controlling erosion and sediment transport in semi‐arid areas has long been appreciated but in practice being by definition rare and episodic they are difficult to study. When they are observed this is frequently in catchments for which little data are available. Another difficulty is that even when catchments are being monitored the instruments that record discharge, sediment load and hillslope sediment fluxes perform inaccurately or unpredictably during extreme weather conditions. This paper describes slope and channel processes that were actually observed by the authors during a (at least) 1 : 30 year 30 minute event with a rainfall intensity of 240 mm h−1 in a second‐order tributary of the Rio Camacho near Tarija in southern Bolivia. During the event, it could be observed how different tributary streams and slope sections contributed sediments and flow to the main channel. Evidence for these contributions did not survive the event, which has implications for both modelling and monitoring. Before the onset of the event open erosion plots were functioning on the slopes where rainfall and runoff were being measured. Rainfall experiments were used to obtain infiltration rates.

The storm began with a moderate intensity of about 5 cm per hour but increased after 5 minutes to 30 cm per hour and continued for 30 minutes. At this time, the rainfall intensity greatly exceeded the infiltration capacity and water started draining the steep slopes. The ephemeral channel rapidly filled up with runoff. Erosion by hailstones was considerable.

Provisionally, the discharge during peak runoff was estimated at 43·7 m3 s−1 (Manning equation). On the basis of sediment loads carried by previous storms, (average concentration of 21 g l−1) the total suspended load discharge during the storm would have been 15 ton ha−1. Within the ephemeral channel, 10 to 50 cm thick layers of coarse sediments were deposited. The collectors of the open erosion plots could not handle the large amounts of runoff and sediment and were completely filled to overflowing.

Comparing these data with soil losses during less intense storms it can be concluded that extreme events largely contribute to erosion and sediment transport and that the majority of the rainstorms play only a minor role. The results also show how limited the values of rainfall experiments are in understanding geomorphic events. This makes modelling of erosion and soil losses a difficult and hazardous task. Copyright © 2002 John Wiley & Sons, Ltd.
Slope–channel linkage and sediment delivery on North Carolina coastal plain cropland
Authors: Slattery Michael C. , Gares Paul A. , Phillips Jonathan D.
Published: December 2002

This paper presents the results of field measurements conducted in a small (19·4 ha) agricultural basin on the North Carolina coastal plain. The overall objective of the study is to determine the magnitude of soil erosion and sediment delivery as a result of storm runoff. The results suggest that erosion in the region is more rapid and extensive than previously thought. Fields at the site are experiencing accelerated soil loss, with rates often comparable to those of the southeastern Piedmont, a region long recognized as having rapid and problematic soil loss. This casts doubt on some assessments of the coastal plain as being a stable, non‐eroding landscape. However, much of the soil mobilized is redistributed and stored within the watershed with only a small portion of the soil eroded from slopes leaving the basin on an event time frame. Copyright © 2002 John Wiley & Sons, Ltd.
Linkage of slope wash and sediment and solute export from a foothill catchment in the Carpathian Foothills of South Poland
Authors: Święchowicz Jolanta
Published: December 2002

This paper analyses the linkage between slope wash and sediment and solute export from the Stara Rzeka foothill catchment. Transport of sediment on slopes and its supply to the stream channel vary in time and depend on morphology and agricultural use of the area. Three thresholds important for morphodynamics in a foothill catchment have been established as well as the role of slopes and valley bottoms in the supply of suspended matter to stream channels. When the first threshold is exceeded, occasional transport of material on a particular slope is initiated. When the second threshold is exceeded, local erosion is triggered on a slope. When the third threshold is exceeded, general transport of material on a slope takes place and is deposited in the valley bottom. When the second threshold is exceeded, the linkage between the slope and the channel is local. When the third threshold is exceeded, the connection between the two systems is general but still the majority of material transported from the slope is deposited on the footslope proluvial plains and in flat valley bottoms.

In the Stara Rzeka foothill catchment, chemical denudation is dominant. However, the proportion of solute and sediment export is significantly larger in its subcatchment. This indicates that proluvial plains impede free sediment flux from the watershed divide to the channel and also that the solute transported by streams comes from the whole area of the catchment, while the source of the sediment is channel erosion. Copyright © 2002 John Wiley & Sons, Ltd.
Evaluation of soil‐loss contribution areas on loess soils in SouthEast Poland
Authors: Rejman Jerzy , Usowicz Bogusław
Published: December 2002

Results of soil‐loss assessments on loess‐derived silt soils are presented. The studies were conducted on plots of different length maintained in continuous bare fallow conditions. Analysing runoff events separately, soil losses per unit area varied with plot length. Description of the soil‐erosion process in terms of (1) maximum soil loss per unit area and (2) the effective distance of soil transport allows us to overcome problems with data interpretation. Smaller values of soil loss per unit area could then be connected with (1) impeded development of erosion process on plots of shorter length and (2) over‐estimation of soil loss contribution area on longer plots. The method of determination of soil‐loss contribution area was the main reason of the differences between soil losses, observed and predicted from the Universal Soil Loss Equation. Studies conducted showed that eroded soil material was transported short distances (from 2 to 13 m). The maximum soil loss per unit area was well correlated with rainfall amount, whilst the effective distance of soil transport was affected by many factors, including rainfall amount and initial state of soil roughness. Copyright © 2002 John Wiley & Sons, Ltd.
Using sediment deposits in small ponds to quantify sediment yield from small catchments: possibilities and limitations
Authors: Verstraeten Gert , Poesen Jean
Published: December 2002

Most soil‐erosion research has been undertaken at small spatial scales, i.e. from small erosion plots over field parcels to small catchments of a few hectares. On the other hand, sediment‐yield data for several large river basins (>1000 km2) are also available. Little information exists, however, on the link between soil‐erosion processes on hillslopes and yields of suspended sediment in large rivers. Data on sediment yield for smaller catchments (1–50 km2) are therefore needed. Such data can be obtained by different measuring methods of which sediment rating curves or river sampling are the most common. In this study, however, the possibilities and limitations of the use of sedimentary deposits in small ponds (<1 ha) to assess sediment yields is investigated. In small catchments (<50 km2), many small flood retention ponds, ponds for irrigation purposes or farm ponds already exist and no expensive monitoring equipment needs to be installed to assess sediment yield. This technique, however, also has a few limitations. Volumetric sediment deposition rates measured in these ponds need to be converted to sediment masses using representative values of the dry sediment bulk density. Furthermore, measured sediment masses need to be corrected for the trap efficiency of the pond otherwise sediment yield will be underestimated. These conversions and corrections are subject to errors. For 21 catchments in central Belgium, the mean error on computed sediment yield, using sediment deposits in small ponds, was estimated to range between 40 and 50 per cent. This error more or less corresponds to the error when using sediment rating curves and suggests that this technique can be a valuable alternative to provide data on the regional variations in sediment yield. Copyright © 2002 John Wiley & Sons, Ltd.
Modelling the effects of hillslope–channel coupling on catchment hydrological response
Authors: Michaelides Katerina , Wainwright John
Published: December 2002

A new two‐dimensional hydrological model has been developed that accounts for dynamic interactions between hillslope and channel flows. The model is specifically designed for semi‐arid areas dominated by Hortonian overland flow, and has a dynamically active channel belt. Sensitivity analyses of the model have been carried out to assess the relative importance of topographic linkages, surface characteristics and rainfall characteristics on catchment hydrological response. Attribute sensitivity analyses suggest that hillslopes are more sensitive than floodplains to all parameters except surface roughness. However, decoupling through the presence of floodplains or other barriers will reduce the relative importance of the sensitivity of hillslope parameters. Spatial sensitivity analysis suggests that sensitivity to the spatial variability of infiltration decreases with an increase in the magnitude of the runoff event. On the other hand, variability in output discharge at the catchment outlet increases with an increase in the spatial variability of infiltration. Rainfall intensity is thus an important factor in controlling the overall coupling characteristics. Catchment runoff production is affected by a complex interaction of topographic, surface and rainfall characteristics. Copyright © 2002 John Wiley & Sons, Ltd.
The influence of land use, soils and topography on the delivery of hillslope runoff to channels in SE Spain
Authors: Kirkby Mike , Bracken Louise , Reaney Sim
Published: December 2002

It is generally accepted that within particular physiographic and climatic regions catchments exhibit differences in their hydrological response. These differences result from the interaction of spatial variability in catchment characteristics, variability of rainfall inputs and surface and subsurface hydrological processes. These interactions are complex and difficult to unravel. Hydrologically similar surfaces (HYSS) have been used to identify catchment areas that have a similar response to rainfall and have been identified at a number of scales. HYSS have been identified at the subcatchment scale for the Rambla de Nogalte in SE Spain. Areas with similar at‐a‐point hydrological storages were distinguished by using a combination of geology, land use and topography. This mapping was compared with discharge estimates made throughout the catchment following a seven‐year return interval flood in September 1997. From this significant flood source areas were identified from reaches showing rapidly increasing channel discharge, and associated with HYSS that combined suitable internal characteristics with good connectivity to the main channel. This paper presents a simulation model that has been developed to investigate the way in which the hydrological response of areas within a HYSS respond to changes in source area, gradient, connectivity to the channel, storm size and intensity profile. This is one of the first studies using a hillslope model to investigate spatial patterns of runoff‐response in semi‐arid areas and results have implications for scaling up hydrological response, and on how the dynamics of runoff producing areas vary both under changing storm conditions and over time. It is implicit in our results that the nature of stream–slope coupling differs substantively between semi‐arid and humid areas. Copyright © 2002 John Wiley & Sons, Ltd.
Modelling solute and sediment transport at different spatial and temporal scales
Authors: Bogena Heye R. , Diekkrüger Bernd
Published: December 2002

A concept for continuous modelling of solute and sediment transport at the catchment scale for a period of 50 years is presented. The simulation is based on the application of the OPUS model system, which is designed for long‐term simulations of agricultural processes. As OPUS is a hillslope model, the catchment is discretized into numerous slopes. Modifications and enhancements of the OPUS model were made in order to simulate interflow induced by macropores. The simulation results are compared with measurements at different spatial and temporal scales of a meso‐scale catchment used for drinking water supply. Five small subcatchments of 22 to 29 ha are used to validate the model at the local scale. The modified and validated model is then applied to the Wahnbach catchment with an area of about 54 km2. Simulations at the local and the catchment scales are presented and compared with measurements.

To model the long‐term behaviour of solute and sediment transport with a deterministic model, a complete set of climate and land‐use data is necessary. In this case study a method was developed to overcome the lack of data by using a weather generator. The long‐term catchment simulations are validated by determining the mass of sediments trapped in the drinking‐water reservoir. The results confirm that the model concept is applicable to a large range of scales from single events to decades and from single slopes to meso‐scale catchments. By using these methods it is conceivable to make forecast simulations of the future solute and sediment discharge using land‐use scenarios. Copyright © 2002 John Wiley & Sons, Ltd.
A new juniper from the Palaeogene of Central Europe
Authors: Kvaček Z.
Published: December 2002

The earliest fossil record of Juniperus L. (Cupressaceae) is reported. Juniperus pauli Z. Kvaček, sp. nova is based on foliage shoots, pollen cones, seed cones and seeds, and belongs to the multiseed series of “entire”‐leafed species of sect. Sabina. It occurs in association with the humid warm‐temperate mixed‐mesophytic forest vegetation in the volcanogenic diatomaceous shale at Roudníky and Větruše in the Palaeogene of the České středohoří Mountains, north Bohemia. The former site is radiometrically dated near the Eocene/Oligocene boundary. The relationship to extant taxa is discussed together with a review of fossil junipers.
Population variation in Persicaria salicifolia (Brouss. ex Willd.) Assenov (Polygonaceae) in Nigeria
Authors: Ayodele A. E. , Olowokudejo J. D.
Published: December 2002

Study of six living population samples and herbarium specimens of Persicaria salicifolia from Nigeria revealed considerable variability in vegetative and floral characters. Two subspecies, one of which is a new one (subsp. nova, p. 516), are recognised. Experimental cultivation showed that the combination of distinguishing characters for each subspecies remains intact under uniform conditions in the botanical nursery.
De Liliifloris Notulae – 7. De decuria altera specierum novarum generis Androcymbium (Colchicaceae) in Africa Australi s.l.
Authors: Müller‐Doblies Ute , Müller‐Doblies D.
Published: December 2002

In a previous paper (Müller‐Doblies 1998) we established a taxonomic framework for Androcymbium sect. Androcymbium by subdividing it into two subsections with two and six series respectively, comprising altogether 34 species. Apart from one monotypic series, the other seven series were foreseen to comprise 3–13 species, and the second largest series A. ser. Gradatocymbia was subdivided into four subseries.

Encouraged by the molecular results of Caujapé Castells et al. (1999, 2001), we upgraded the two subsections of A. sect. Androcymbium to sectional level: A. subsect. Gradatocymbium became A. sect. Kunkeliocymbium with 16 spp. and the emended A. sect. Androcymbium s.str. now has 30 spp.

The largest series A. ser. Eghimocymbia was already earmarked for a subdivision into subseries, a plan which is realized in the present paper. For another 10 new species (numbered # 11–# 20 in the present paper) diagnoses and drawings are given. Furthermore the postponed drawings of five new Androcymbium species described in Müller‐Doblies (1998) are added here. Eight of the present new spp. were collected alive in the field for cultivation, whereas each of the remaining two are only known from a herbarium specimen.

For the presentation of distribution data, the geographic table for Southern Africa developed by Müller‐Doblies (1996) (refined by Müller‐Doblies et al. 2001) is used in Tables 5–7. After the inclusion of two Androcymbium species and one subspecies described by Pedrola Montfort et al. (1999a, b), the three distribution tables of Androcymbium in Southern Africa comprise 50 species [retaining the numbering 05–48 of Müller‐Doblies (1998) for Androcymbium sect. Androcymbium and including the new Pedrola species for the time being as 13A and 14A]. Thus, the current list of Southern African Androcymbium species embraces a total of 50 spp. in 11 series.

Only two of the 50 Southern African Androcymbium species do not occur in the Republic of South Africa (RSA): i.e. the Namibian endemics A. etesionamibense and A. buchubergense. Of the remaining 48 Androcymbium species 38 are endemic to RSA. The 10 non‐endemic species occur in addition to RSA also in Namibia, or in Lesotho and/or Swaziland. The highest concentration of Androcymbium species is found in the Northern and the Western Cape: in each of them more than 50% of the 48 South African species occur (28 and 26 spp. respectively including 12 and 10 endemic spp.), whereas in the other seven provinces only 0–6 spp. occur of which only two species are endemic to Kwazulu‐Natal.
Originalité de la flore et de la végétation de l'Anti‐Atlas sud‐occidental (Maroc)
Authors: Msanda F. , El Aboudi A. , Peltier J.P.
Published: December 2002

L'Anti‐Atlas occidental marocain se caractérise par des structures de végétation constituées à la fois par des éléments de souche méditerranéenne, saharienne et tropicale qui cohabitent en fonction des conditions climatiques. L'originalité du secteur tient à la présence du genre endémique Argania, d'éléments succulents, de Quercus ilex subsp. rotundifolia (qui trouve ici sa limite méridionale absolue au Maroc), d'un développement spectaculaire de la steppe à Artemisia inculta (qui annonce un domaine plus interne), d'une flore saharienne (sur le revers méridional) et de nombreuses endémiques. Les principales structures de végétation sont rappelées et leur ordonnancement précisé. En fonction de critères édapho‐géomorphologiques, diverses associations sahariennes ont été retrouvées et quelques nouvelles structures de végétation décrites. Le passage à la végétation saharienne se situe au nord du jbel Bani et correspond à l'isohyète des 100 mm. Toutes ces végétations se caractérisent par leur extrême dégradation, à l'origine souvent d'une uniformisation des paysages rendant difficile la reconnaissance des différents bioclimats.
Endemic genera of the Caucasian flora
Authors: Gagnidze R. , Gviniashvili Ts. , Shetekauri Sh. , Margalitadze N.
Published: December 2002

Within the flora of the Caucasus consists of 17 mono‐ or oligotypic endemic or subendemic genera. Their taxonomy and nomenclature, chorology (latudinal and longitudinal distribution) as well as the site conditions are examined. According to their distribution patterns endemic genera could be classified as follows: Greater Caucasus, Western Caucasus, Central Caucasus, Eastern Caucasus, Greater Eastern Caucasus, and common Caucasus endemics. The centres of diversity of the subendemic genera are in the Caucasus, but spread out into Lazistan and Anatolia, some of them are also found in Iran. Most of the endemic genera developed in the phytogeographical units (phytochorions) of the Colchis and of the Caucasus. The florogenetic relation to Mediterranean genera is demonstrated.

The caryogeographic analysis of endemic genera shows that the majority is palaeodiploid. Geographical isolation (with respect to longitude, latitude and altitude) is an important factor in the formation and evolution of the Caucasian flora generated by three‐dimensional landscape structure of the mountains.
Loss of folylpoly‐γ‐glutamate synthetase activity is a dominant mechanism of resistance to polyglutamylation‐dependent novel antifolates in multiple human leukemia sublines
Authors: Liani Esti , Rothem Lilah , Bunni Marlene A. , Smith Clyde A. , Jansen Gerrit , Assaraf Yehuda G.
Published: December 2002

We have studied the molecular basis of drug resistance in human CCRF‐CEM leukemia cells exposed to high dose intermittent pulses of novel polyglutamatable antifolates that target various folate‐dependent enzymes. These include the dihydrofolate reductase (DHFR) inhibitors edatrexate, methotrexate and aminopterin, the thymidylate synthase (TS) inhibitors ZD1694 and GW1843, the glycinamide ribonucleotide formyltransferase (GARTF) inhibitor DDATHF as well as the multitargeted antifolate LY231514 inhibiting both TS, DHFR and GARTF. Fourteen antifolate‐resistant sublines were isolated, 11 of which displayed a drug resistance phenotype that was based on impaired folylpoly‐γ‐glutamate synthetase (FPGS) activity as these cell lines: 1) typically lost 90–99% of parental FPGS activity; 2) expressed 1.4–3.3‐fold less FPGS mRNA (only 4 cell lines); 3) displayed up to 105‐fold resistance to polyglutamylation‐dependent antifolates including ZD1694 and MTA; 4) retained sensitivity to polyglutamylation‐independent antifolates including ZD9331 and PT523; 5) were up to 19‐fold hypersensitive to the lipid‐soluble antifolates trimetrexate and AG377; 6) had a normal or a small decrease in [3H]MTX transport; and 7) had a 2.1–8.3‐fold decreased cellular folate pools and a consequently increased folate growth requirement. The remaining 3 antifolate‐resistant sublines lost 94–97% of parental [3H]MTX transport and thus displayed a high level resistance to all hydrophilic antifolates. To screen for mutations in the hFPGS gene, we devised an RT‐PCR single strand conformational polymorphism (SSCP) assay. RT‐PCR‐SSCP analysis and DNA sequencing showed that only a single FPGS‐deficient subline harbored an FPGS mutation (Cys346Phe). Three‐dimensional modeling of the human FPGS based on the crystal structure of Lactobacillus casei FPGS suggested that this mutation maps to the active site and interferes with the catalytic activity of the enzyme due to a putative bulky clash between the mutant Phe346 and a native Phe350 within α‐helix A10 in a highly conserved C‐terminal hydrophobic core. This was consistent with a 23‐fold decreased affinity of the mutant Cys346Phe FPGS for L‐glutamate. We conclude that decreased FPGS activity is a dominant mechanism of resistance to polyglutamylation‐dependent novel antifolates upon a high‐dose intermittent exposure schedule. The finding that cells may exhibit 5 orders of magnitude of resistance to polyglutamylation‐dependent antifolates but in the same time retain parental sensitivity or hypersensitivity to polyglutamylation‐independent antifolates or lipophilic antifolates offers a potentially promising treatment strategy in the overcoming of FPGS‐based anticancer drug resistance. © 2002 Wiley‐Liss, Inc.
Pharmacokinetic, biochemical and clinical effects of dimethyltriazenoimidazole‐4‐carboxamide–bischloroethylnitrosourea combination therapy in patients with advanced breast cancer
Authors: Clemons Mark , Ranson Malcolm , Margison Jennifer M. , El Teraifi Hassan , Griffiths Audrey , Kelly Jane , Morris Charles Q. , Howell Anthony , Margison Geoffrey P.
Published: December 2002

We assessed whether split dosing with the methylating agent DTIC is an effective strategy for inactivating the DNA repair protein O6‐alkylguanine DNA‐ATase in order to decrease tumour resistance to BCNU. ATase levels in PBMCs were used as a surrogate for tumour ATase depletion to determine whether this correlated with either the pharmacokinetics of DTIC and its major metabolite AIC or other clinical sequelae. Two 1 hr infusions of DTIC (400 mg/m2) 4 hr apart followed another 4 hr later by BCNU (75 mg/m2) were administered every 6 weeks in 7 patients with heavily pretreated advanced breast cancer. The extent and kinetics of ATase depletion and recovery in PBMCs varied not only between patients but also between cycles in the same patient. Serial FNAs showed heterogeneity in tumour ATase expression but no clear pattern of change in ATase activity. DTIC and AIC exhibited biphasic clearance from the blood, consistent with a 2‐compartment pharmacokinetic model. The AUC of AIC was strongly correlated with the percentage decrease in PBMC ATase levels. There were no clinical responses, and toxicity in neutrophils and platelets was marked. Split‐dose DTIC therefore does not appear to be a clinically effective approach to overcome O6‐alkylating agent resistance in advanced breast cancer. © 2002 Wiley‐Liss, Inc.
EphA2 overexpression correlates with poor prognosis in esophageal squamous cell carcinoma
Authors: Miyazaki Tatsuya , Kato Hiroyuki , Fukuchi Minoru , Nakajima Masanobu , Kuwano Hiroyuki
Published: December 2002

EphA2 is a member of the Eph family of receptor tyrosine kinases, which interact with cell‐bound ligands known as ephrins. EphA2 expression was investigated by immunohistochemistry with an anti‐EphA2 monoclonal antibody in 80 patients with esophageal squamous cell carcinoma (ESCC) who had undergone surgery. EphA2 overexpression was positive in 40 of the 80 patients (50%). A significant correlation was observed between EphA2 expression and regional lymph node metastasis (p=0.023), number of lymph node metastases (p=0.011) and poor degree of tumor differentiation (p=0.004). The survival rates of EphA2‐positive patients were poorer than those of EphA2‐negative patients (p=0.014). The 5‐year survival rate of patients without EphA2 overexpression was 68%, whereas that of patients with EphA2 overexpression was 29%. EphA2 expression was also investigated in 7 ESCC cell lines (TE‐1, ‐2, ‐8, ‐13, ‐15, TT and TTn) and 1 immortalized human esophageal keratinocyte cell line (CHEK‐1). Western blotting revealed different levels of EphA2 expression in the 8 cell lines. EphA2 was expressed at a high level in the ESCC cell lines compared to CHEK‐1. EphA2 phosphorylation was demonstrated in all cell lines. Northern blot analysis showed that EphA2 mRNA expression in TE‐1 was greater than that in the other ESCC cell lines. The observation of small gaps on Western blot analysis of the ESCC cell lines suggests that there may be a mechanism for EphA2 regulation at the point of translation. In conclusion, EphA2 overexpression appears to be related to poor degree of tumor differentiation and lymph node metastasis in ESCC. Consequently, patients with EphA2 overexpression have a poorer prognosis than those without. EphA2 is a potential target to prevent ESCC cells spreading into the lymphatic drainage. © 2002 Wiley‐Liss, Inc.