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Modified Method (modified + method)

Distribution by Scientific Domains

Life Sciences	25%
Engineering	20%
Medical Sciences	16%
Mathematics and Statistics	16%
Chemistry	12%
Earth and Environmental Science	8%

Selected Abstracts

Modified method of characteristics for solving population balance equations

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 11 2003
Laurent Pilon
Abstract This paper presents a new numerical method for solving the population balance equation using the modified method of characteristics. Aggregation and break-up are neglected but the density function variations in the three-dimensional space and its dependence on the external fields are accounted for. The method is an interpretation of the Lagrangian approach. Based on a pre-specified grid, it follows the particles backward in time as opposed to forward in the case of traditional method of characteristics. Unlike the direct marching method, the inverse marching method uses a fixed grid thus, making it compatible with other numerical schemes (e.g. finite-volume, finite elements) that may be used to solve other coupled equations such as the mass, momentum, and energy conservation equations. The numerical solutions are compared with the exact analytical solutions for simple one-dimensional flow cases. Very good agreement between the numerical and the theoretical solutions has been obtained confirming the validity of the numerical procedure and the associated computer program. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Modified method for external attachment of transmitters to birds using two subcutaneous anchors

JOURNAL OF FIELD ORNITHOLOGY, Issue 3 2008
Tyler L. Lewis
ABSTRACT Of the transmitter attachment techniques for birds, the subcutaneous anchor provides a secure attachment that yields relatively few secondary effects. However, the use of subcutaneous anchors has been limited by transmitter size and retention time. Using a modified method of attachment that utilized two subcutaneous anchors, we deployed 69 GPS transmitters, plus 13 VHF transmitters that were similar in size and weight to GPS models, on Pacific Black Brant (Branta bernicla nigricans). Prior to our study, only harnesses were used for attaching GPS transmitters on birds, mainly because GPS transmitters are too large for other external attachment techniques and implantation in the body cavity attenuates the GPS signal. Thus, to increase the size capacity of anchor attachment and to avoid the well-documented negative effects of harnesses on behavior and survival, we added a second anchor at the transmitter's posterior end. The double-anchor attachment technique was quickly and easily accomplished in the field, requiring bird handling times of <10 min. Incidental recoveries of tagged Brant indicate a high degree of transmitter retention. Five recaptured birds (4,6 weeks after deployment) and eight killed by hunters (3,6 mo after deployment) retained their GPS transmitters. For studies involving the use of relatively large transmitters, the double-anchor method appears to provide a viable alternative for external attachment. SINOPSIS Entre las técnicas para montar radiotransmisores a aves, el anclaje subcutáneo provee una forma segura de montaje que presenta muy pocos efectos secundarios. Sin embargo, la utilidad del anclaje subcutáneo ha sido limitada por el tamaño del transmisor y el tiempo de retención en el ave. Utilizando un método modificado que utiliza dos puntos subcutáneos de anclaje, desarrollamos 69 transmisores GPS y 13 transmisores VHF que replicaban el tamaño y peso de modelos GPS, y que fueron montados en individuos del ganso, Branta bernicla nigricans. Previo a este estudio, solo se habían utilizado arneses para colocar radiotransmisores en los gansos. Esto fue así porque los tipo GPS son demasiado grandes para ser colocados de otra manera y cuando se implantan en la cavidad celómica, queda atenuada la señal del transmisor. Por tal razon, y para incrementar la capacidad de anclaje del transmisor y evitar el impacto negativo documentado en los arneses (en conducta y sobrevivencia), añadimos un segundo punto de anclaje en la parte posterior del transmisor. La técnica desarrollada fue fácil de aplicar en el campo y se hizo de forma rápida (<10 minutos). Recobros incidentales de gansos (4 recapturas, 4,6 semanas después) y ocho individuos cazados (3,6 meses después) indicaron un 100% de retención de los transmisores. Para estudios que conlleven transmisores de gran tamaño, el método de doble anclaje parece proveer una alternativa adecuada. [source]

Evaluation of acute copper toxicity to larval fathead minnows (Pimephales promelas) in soft surface waters

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2005
Eric J. Van Genderen
Abstract The hardness-based regulatory approach for Cu prescribes an extrapolation of the toxicity-versus-hardness relationship to low hardness (,50 mg/L as CaCO3). Hence, the objective of the present research was to evaluate the influences of water quality on acute Cu toxicity to larval fathead minnow (Pimephales promelas) in low-hardness surface waters. Seasonal water sampling was conducted at 24 sites throughout South Carolina, USA, to determine the site-specific influences of soft surface-water conditions on acute Cu toxicity. Concurrent toxicity tests in laboratory water, matched for hardness and alkalinity (modified method), also were conducted to allow calculation of water-effect ratios (WERs). In addition, tests were conducted at recommended hardness levels (recommended method) for comparison of WER methodology in soft water. Surface-water conditions (average ± standard deviation, n = 53) were hardness of 16 ± 8 mg/L as CaCO3, alkalinity of 18 ± 11 mg/L as CaCO3, and dissolved organic carbon of 6 ± 4 mg/L. Dissolved Cu 48-h median lethal concentration (LC50) values varied nearly 45-fold across the dataset and greater than four-fold at individual sites. Spatial (p < 0.0001) and seasonal (p = 0.026) differences among LC50 values were determined for eight sites that had multiple toxicity results for one year. All modified WERs were greater than 1.0, suggesting that the site waters were more protective of Cu toxicity than the matched laboratory water. Some WERs generated using recommended methods were less than 1.0, suggesting limited site-specific protection. Based on these observations, extrapolation of the hardness-based equation for Cu at 50 mg/L or less as CaCO3 would adequately protect fathead minnow populations in soft surface waters. The WER results presented here demonstrate the inconsistency between hardness-based criteria and the methodology for deriving site-specific water-quality criteria in low-hardness waters. [source]

Variant of estimation method of aboveground plant biomass in grassland with the gamma model.

GRASSLAND SCIENCE, Issue 2 2006

Abstract A modified method with visual observation for estimating biomass distribution on grasslands is proposed. This labor-saving technique facilitates surveys for estimating herbaceous biomass distribution for grasslands. It is based on the principle of Shiyomi's visual observation method. The procedure is performed as follows. (i) Set two points with biomass of c1 g and c2 g used as criteria in a pasture (c1 < c2). (ii) In the first visual observation, divide herbaceous biomass in the pasture into two classes that are more or less than c1 g. (iii) In the second visual observation, divide herbaceous biomass in the same pasture into two classes that are more or less than c2 g. Then, match the trial numbers obtained in the first and second observations. (iv) Measure the biomass weights of c1 and c2 with cutting. (v) From the data obtained above, infer the herbaceous biomass distribution using the gamma model. The procedure was conducted in a Zoysia grazed pasture. The following are discussed: advantages and regulations of the current method with a gamma model; some problems of the cutting method, as viewed from the shape of herbaceous biomass distribution; and the influence of grazing pressure on herbaceous biomass distribution. [source]

Enrichment of enhanced assumed strain approximations for representing strong discontinuities: addressing volumetric incompressibility and the discontinuous patch test

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 1 2004
J. E. Dolbow
Abstract We present a geometrically non-linear assumed strain method that allows for the presence of arbitrary, intra-finite element discontinuities in the deformation map. Special attention is placed on the coarse-mesh accuracy of these methods and their ability to avoid mesh locking in the incompressible limit. Given an underlying mesh and an arbitrary failure surface, we first construct an enriched approximation for the deformation map with the non-linear analogue of the extended finite element method (X-FEM). With regard to the richer space of functions spanned by the gradient of the enriched approximation, we then adopt a broader interpretation of variational consistency for the construction of the enhanced strain. In particular, in those elements intersected by the failure surface, we construct enhanced strain approximations which are orthogonal to piecewise-constant stress fields. Contrast is drawn with existing strong discontinuity approaches where the enhanced strain variations in localized elements were constructed to be orthogonal to constant nominal stress fields. Importantly, the present formulation gives rise to a symmetric tangent stiffness matrix, even in localized elements. The present modification also allows for the satisfaction of a discontinuous patch test, wherein two different constant stress fields (on each side of the failure surface) lie in the solution space. We demonstrate how the proposed modifications eliminate spurious stress oscillations along the failure surface, particularly for nearly incompressible material response. Additional numerical examples are provided to illustrate the efficacy of the modified method for problems in hyperelastic fracture mechanics. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Modified method of characteristics for solving population balance equations

Constructing a non-linear relationship between the incoming solar radiation and bright sunshine duration

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 12 2010
Khil-Ha Lee
Abstract This paper reports the application of a non-linear relationship between the incoming shortwave solar radiation and bright sunshine duration. The newly suggested equation is a modified form of the existing Angstrom equation. Measurements of solar radiation and sunshine radiation from 1997 to 2006 at 21 meteorological stations were used to calibrate and validate the suggested equation. The model parameters required to specify the nature of the relationship between solar radiation and sunshine duration were determined by automatically minimizing the difference between the modelled and measured solar radiation. At the 21 meteorological stations, the absolute error (AE) is in the range of ,0.126,0.158 MJm,2 day,1 for the original Angstrom equation, while it is in the range of ,0.089,0.154 MJm,2 day,1 for the modified equation. The root mean square error (RMSE) is also improved by 7,8% for the modified method. The results show that the newly suggested equation generally provides better performance than the existing Angstrom equation. Copyright © 2009 Royal Meteorological Society [source]

Accurate and time efficient estimation of the probability of error in bursty channels,

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 7 2003
M. Stevan Berber
Abstract A method and a technique for the probability of error estimation in digital channels with memory are developed and demonstrated. The expressions for the mean and variance of a random variable, representing a block of bits transmission in a bursty channel (channel with memory), are derived. The influence of the memory is expressed by a parameter called the memory factor. It is shown that the traditional Monte Carlo method can be applied for the probability of error estimation. In order to control the accuracy and increase the time efficiency of estimation this method is modified and a new method, called the modified Monte Carlo method, is proposed. Based on this modified method a technique of estimation with controlled accuracy is developed and demonstrated using data obtained by simulation. According to this technique the sample size is adjusted in the course of estimating procedure to give an accurate estimate of the probability of error for a minimum required time of estimation. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Parameter optimization for a PEMFC model with a hybrid genetic algorithm

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 8 2006
Zhi-Jun Mo
Abstract Many steady-state models of polymer electrolyte membrane fuel cells (PEMFC) have been developed and published in recent years. However, models which are easy to be solved and feasible for engineering applications are few. Moreover, rarely the methods for parameter optimization of PEMFC stack models were discussed. In this paper, an electrochemical-based fuel cell model suitable for engineering optimization is presented. Parameters of this PEMFC model are determined and optimized by means of a niche hybrid genetic algorithm (HGA) by using stack output-voltage, stack demand current, anode pressure and cathode pressure as input,output data. This genetic algorithm is a modified method for global optimization. It provides a new architecture of hybrid algorithms, which organically merges the niche techniques and Nelder,Mead's simplex method into genetic algorithms (GAs). Calculation results of this PEMFC model with optimized parameters agreed with experimental data well and show that this model can be used for the study on the PEMFC steady-state performance, is broader in applicability than the earlier steady-state models. HGA is an effective and reliable technique for optimizing the model parameters of PEMFC stack. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Urological complications in 980 consecutive patients with renal transplantation

INTERNATIONAL JOURNAL OF UROLOGY, Issue 10 2006
HAMID R DAVARI
Aim: To present the urological complications of renal transplantations performed in the last 14 years at one center and to briefly explain a modified method of Lich,Gregoir ureteroneocystostomy. Methods: The data of 980 patients receiving kidney transplants at the authors' institution from April 1991 to February 2004 were reviewed in a retrospective prospective study. In particular, surgical techniques and urological complications were noted. Results: A total of 980 patients had received kidney transplantation. Extravesical ureteroneocystostomy (Lich,Gregoir method) was used in the first 480 patients (group A). In the subsequent 500 patients, the authors' modified method of extravesical ureteroneocystostomy, using single layer anastomosis and small feeding tubes as stent, was used (group B). Overall urological complication rate was 2.8% (28 patients), including leakage (13 patients, 1.3%), stenosis (seven, 0.7%), obstruction (one, 0.1%), distal ureter necrosis (four, 0.4%), pelvocalyceal fistula (two, 0.2%) and implantation of ureter into the peritoneum (one, 0.1%). Urological complications were significantly more common in group A compared to group B (16, 3.3% and 9, 1.8%, respectively; P < 0.05). Conclusions: Preserving the adventitia, fat and blood supply of the ureter by delicate dissection of the ureter during donor nephrectomy, short ureters, and fixation of the adventitia, fat and blood supply of the ureter to the bladder wall, to prevent kinking or twisting, are important factors in decreasing urological complications. Additionally, the authors' method of ureteroneocystostomy is also effective in decreasing the incidence of ureteric complications. [source]

Modified method for external attachment of transmitters to birds using two subcutaneous anchors

Novel putative nonprotein-coding RNA gene from 11q14 displays decreased expression in brains of patients with schizophrenia

JOURNAL OF NEUROSCIENCE RESEARCH, Issue 1 2003
Oxana O. Polesskaya
Abstract A modified method of differential display was employed to identify a novel gene (named PSZA11q14), the expression of which was reduced in brains from patients with schizophrenia. Decreased expression of PSZA11q14 was identified initially in Brodmann's area (BA) 21 from a small group of patients with schizophrenia (n = 4) and normal controls (n = 6) and was confirmed subsequently using independent RT-PCR assay in BA 21, 22, and 9, and in hippocampus from a larger group of patients with schizophrenia (n = 36) and controls (n = 35). PSZA11q14 is located on chromosome 11q14, an area shown previously to co-segregate with schizophrenia and related disorders in several families. Decreased expression of PSZA11q14 in patients with schizophrenia and its location on 11q14 provide converging lines of evidence indicating that PSZA11q14 may be involved in at least some cases of schizophrenia. PSZA11q14 shows no significant homology with any known gene. It has no introns and produces two RNA transcripts of ,4.5 and ,7.0 kb. The largest open reading frame (ORF) in the PSZA11q14 transcripts may potentially encode for a short polypeptide of 71 amino acids. High frequency of rare codons, the short size of this ORF, and low homology with mouse sequences, however, indicate that PSZA11q14 may instead represent a novel member of a family of nonprotein-coding RNA genes that are not translated and that function at the RNA level. PSZA11q14 is located within the first intron of the DLG-2 gene and transcribed in the opposite direction to DLG-2. These results suggest that PSZA11q14 may be considered a candidate gene for schizophrenia acting as an antisense regulator of DLG-2, which controls assembling functional N -methyl- D -aspartate (NMDA) receptors. © 2003 Wiley-Liss, Inc. [source]

Pilot-scale anaerobic thermophilic digester treating municipal sludge

AICHE JOURNAL, Issue 1 2006
M. A. de la Rubia
Abstract The work reported concerns anaerobic thermophilic municipal sludge digestion (55°C) in a completely mixed anaerobic digester on a pilot-plant scale (850 L). The experimental protocol was defined to examine the effect of increasing the organic loading rate (OLR) on the efficiency of this digester and to report on its steady-state performance. The reactor had previously been converted from mesophilic to thermophilic conditions following the protocol previously proposed by the authors: this was achieved by a modified method that combined systems investigated in Chicago and in Vancouver. The reactor was subsequently subjected to a program of steady-state operation over a range of sludge retention times (SRTs) of 27, 20, and 15 days. The digester was fed with raw sludge [containing approximately 34.8 g/L volatile solids (VS)] three times per day. Under thermophilic conditions and with a 27-day SRT, the reactor was operated with an OLR of 1.48 kg VS m,3 day,1. The solids removal efficiency of the reactor was 42.9%, whereas the volumetric methane production rate in the digester reached 0.35 m3 m,3 day,1. Over an operating period of 150 days, an OLR of 2.63 kg VS m,3 day,1 was achieved with 41.8% VS removal efficiency in the pilot sludge digester (SRT: 15 days). During this period the volumetric methane production rate in the digester reached 0.20 m3 m,3 day,1 and 0.20 m3/kg VSr (VS reduction). The greatest efficiency in terms of substrate removal was 54.3% for an OLR of 1.71 kg VS m,3 day,1 and SRT of 20 days. Under these conditions, the generation of biogas and methane was at levels of 0.86 and 0.58 m3 m,3 day,1, respectively, with a methane yield of 0.70 m3/kg VSr. © 2005 American Institute of Chemical Engineers AIChE J, 2006 [source]

Preparation of budesonide/,-cyclodextrin complexes in supercritical fluids with a novel SEDS method

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 10 2006
Tarja Toropainen
Abstract The aim was to investigate if solid drug/cyclodextrin complexes could be produced in a single-step process with a solution enhanced dispersion by supercritical fluids (SEDS) method. Budesonide and ,-cyclodextrin (CD) solutions (50% or 99.5% ethanol) were pumped from the same (conventional method) or separate (modified method) containers together with supercritical carbon dioxide through a coaxial nozzle into a particle formation chamber. The pressure was maintained at 100, 150 or 200 bar with a temperature of 40, 60 or 80°C. SEDS-processed powders were characterised with HPLC, DSC and XRPD for budesonide content, complexation and crystallinity. The budesonide dissolution rate was determined in 1% ,-CD aqueous solution. Solid, white budesonide/,-CD complex particles were formed using the conventional and modified SEDS processes. The complexation efficiency was dependent on the processing conditions. For example, with the conventional method (100 bar, 60°C) the yield of the powder was 65,±,12% with 0.14,±,0.02 mg budesonide/mg powder, corresponding to 1:2 drug:CD molar ratio. The dissolution rate of this complexed budesonide (93,±,2% after 15 min) was markedly higher compared to unprocessed micronised budesonide (41,±,10%) and SEDS-processed budesonide without CD (61,±,3%). As a conclusion, SEDS is a novel method to produce solid drug/CD complexes in a single-step process. © 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 95:2235,2245, 2006 [source]

Stereological evaluation of treatment response in patients with non-resectable hepatic alveolar echinococcosis using computed tomography via the Cavalieri method

LIVER INTERNATIONAL, Issue 10 2006
Bulent Aydinli
Abstract: Introduction: The purposes of this study were to describe and adapt the relevant methods of computed tomography (CT) and stereology to estimate parasitic volume in the liver, to compare the efficiency of benzimidazole treatment in hepatic alveolar echinococcosis (AE), and to determine whether the response rates measured by the stereological method are correlated with those measured by simple volumetric measurements (SVM). Methods: Nine eligible patients with non-resectable AE were included in the study. By using their abdominal CT at the baseline and after a year of treatment, treatment responses of the cases were evaluated both by the stereological method via a software and by SVM, retrospectively. The volume estimation was performed in our study using a different approach that consisted of three separate stages combined with the Cavalieri method of modern design stereology. Results: The response rates were ,17±55% and ,12±37% by the Cavalieri method and SVM, respectively; however, they were not statistically significant (P=0.59 and 0.21 for the Cavalieri method and SVM, respectively). Although some cases had comparable results, others had different response rates, and the two methods showed no significant correlation (r=,0.31, P=0.41). Conclusions: Because this modified method provides accurate results by reducing margin of errors, even in case of bizarre shape of AE, a correct, unbiased, and reliable management of the cases with AE via this method may be possible. Owing to lack of a correlation with SVM, it is suggested that a measurement via SVM may be wrong and its use in the evaluation of the treatment response in such cases will not be sufficient and completely true. [source]

Modified relaxation method for mathematical programs with complementarity constraints

MATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 17 2007
Gui-Hua Lin
Abstract In this paper, we suggest a new relaxation method for solving mathematical programs with complementarity constraints. This method can be regarded as a modification of a method proposed in a recent paper (J. Opt. Theory Appl. 2003; 118:81,116). We show that the main results remain true for the modified method and particularly, some conditions assumed in the previous paper can be removed. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Characteristic-mixed covolume methods for advection-dominated diffusion problems

NUMERICAL LINEAR ALGEBRA WITH APPLICATIONS, Issue 9 2006
Zhangxin Chen
Abstract Characteristic-mixed covolume methods for time-dependent advection-dominated diffusion problems are developed and studied. The diffusion term in these problems is discretized using covolume methods applied to the mixed formulation of the problems on quadrilaterals, and the temporal differentiation and advection terms are treated by characteristic tracking schemes. Three characteristic tracking schemes are studied in the context of mixed covolume methods: the modified method of characteristics, the modified method of characteristics with adjusted advection, and the Eulerian,Lagrangian localized adjoint method. The proposed methods preserve the conceptual and computational merits of both characteristics-based schemes and the mixed covolume methods. Existence and uniqueness of a solution to the discrete problem arising from the methods is shown. Stability and convergence properties of these methods are also obtained; unconditionally stable results and error estimates of optimal order are established. Copyright © 2006 John Wiley & Sons, Ltd. [source]

A finite element modified method of characteristics for convective heat transport

NUMERICAL METHODS FOR PARTIAL DIFFERENTIAL EQUATIONS, Issue 3 2008
Mofdi El-Amrani
Abstract We propose a finite element modified method of characteristics for numerical solution of convective heat transport. The flow equations are the incompressible Navier-Stokes equations including density variation through the Boussinesq approximation. The solution procedure consists of combining an essentially non-oscillatory modified method of characteristics for time discretization with finite element method for space discretization. These numerical techniques associate the geometrical flexibility of the finite elements with the ability offered by modified method of characteristics to solve convection-dominated flows using time steps larger than its Eulerian counterparts. Numerical results are shown for natural convection in a squared cavity and heat transport in the strait of Gibraltar. Performance and accuracy of the method are compared to other published data. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2008 [source]

An optimal-order error estimate for MMOC and MMOCAA schemes for multidimensional advection-reaction equations

NUMERICAL METHODS FOR PARTIAL DIFFERENTIAL EQUATIONS, Issue 1 2002
Hong Wang
Abstract In this article, we analyze the modified method of characteristics (MMOC) and an improved version of the MMOC, named the modified method of characteristics with adjusted advection (MMOCAA), for multidimensional advection-reaction transport equations in a uniform manner. We derive an optimal-order error estimate for these schemes. Numerical results are presented to verify the theoretical estimates. © 2002 John Wiley & Sons, Inc. Numer Methods Partial Differential Eq 18: 69,84, 2002 [source]

Extraction and characterisation of hemicelluloses from maize stem

PHYTOCHEMICAL ANALYSIS, Issue 5 2010
Xiao-Feng Sun
Abstract Introduction , Extraction and characterisation of hemicelluloses are very important for converting them into functional materials and chemicals. Objective , To develop a method for isolation of hemicelluloses from all cell walls. Methodology , Sequential steps using 90% dioxane, 80% acidic dioxane, 100% dimethyl sulphoxide and 8% NaOH were used for extraction of the hemicellulosic preparations (H1, H2, H3 and H4) from maize stem. Advanced NMR techniques were used for the analysis of native hemicelluloses. Results , Hemicelluloses with high yieldd were isolated from all cell walls, and contained arabinoxylan as the major polysaccharide. H3 was substituted by , - l -arabinofuranose, , - d -xylopyranose, and acetyl groups (degree of saturation = 0.12/0.09) at O -3/O -2 of xylan. H4 had a long continuous side chain of arabinose residues, and associated closely with non-cellulosic glucose. The hemicelluloses formed more linkages with guaiacyl lignins, and some p -coumaric acids built a bridge between hemicelluloses and lignin in maize stem. Conclusion , This modified method is successful for the isolation of hemicelluloses with high yields from all cell walls of maize stem. Copyright © 2010 John Wiley & Sons, Ltd. [source]

A modified method for purifying amelanotic melanocytes from human hair follicles

THE JOURNAL OF DERMATOLOGY, Issue 4 2006
Hui-Jun MA
ABSTRACT We describe a modified method for establishing long-term pure cultures of amelanotic melanocytes (AMMC) derived from human hair follicles. Normal human corpse scalp (just after death, 1 h) was transected 1 mm below the epidermis, and hair follicles in the remaining dermis were isolated by a two-step enzyme treatment. Hair follicle cell suspensions were prepared by 0.50% trypsin treatment for 30 min and cultured in an optimized melanoblast proliferation nature mitogen medium. Cells attached to the substratum were mostly amelanotic melanocytic in character with small, bipolar shapes in the early stage; only a few keratinocytes and rare fibroblasts were observed. Keratinocytes were easily removed by differential trypsinization. After the third passage, the proliferating cells were all amelanotic melanocytes as confirmed by immunostaining with polyclonal antibodies to ,PEP7h, which recognized the tyrosinase protein located on melanosomes and NKI/beteb, which is a pre-melanosomal antigen against synthetic peptides corresponding to the carboxyl termini of human melanosomal protein GP100. Cultured AMMC were highly positive to L-dopa reactivity after the addition of IBMX to the culture medium for 7 days. Many stage I and II melanosomes and occasional stage III melanosomes without stage IV melanosomes were found in the cytoplasm by transmission electron microscope. This modified technique is potentially more suitable for cultivating amelanotic melanocytes. The availability of pure cultures of hair-follicle amelanotic melanocytes will facilitate investigations of the roles of those cells in migration and differentiation during treatment of vitiligo. [source]

A Marine Dinoflagellate, Amphidinium eilatiensis n. sp., from the Benthos of a Mariculture Sedimentation Pond in Eilat, Israel

THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 6 2003
JOHN J. LEE
ABSTRACT. A species of Amphidinium bloomed in a mariculture sedimentation pond that was used to grow bivalves near the Gulf of Eilat, Israel. Its overall length averaged 13 ,m, the hypocone was 11 ,m, and its width was 8,m. It has a ventral ridge. The sulcus begins at the longitudinal flagellar pore and does not project forward in the apex toward the transverse flagellar pore and left margin of the cingulum. The sulcus is a very shallow groove that projects variably about a third of the body length toward the antapex. The cingulum is a deep groove as it circles the cell from the left ventral side to the dorsal side and then becomes very shallow on the right ventral side as it arches posterior toward the longitudinal flagellar pore. Using a modified method for studying dinoflagellate chromosomes in the SEM, we observed 31 chromosomes. The plastid is dorsal and peripheral with 6 ventrally projecting peripheral digital lobes that wrap around the sides of the ventral and posterior nucleus. Amphidinium eilatiensis n. sp. is morphologically closest to Amphidinium carterae and Amphidinium rhynchocephalum, but it does not have the obvious thecal plates or polygonal units described for the former species. Instead, it has a series of spicules, bumps, and ridges on its surface. It differs from A. rhynchocephalum by two morphological characters: surface morphology and gross plastid architecture. The amplified fragments of the rDNA from A. eilatiensis n. sp. isolated from 2 separate sedimentation ponds in Eilat include the 3,-end of the SSU rDNA (about 100 nt), the whole ITS region (ITS1 + 5. 8S + ITS2) and the 5,-end of the LSU rDNA (about 900 nts). The total length of the sequences ranged from 1,460 nt. (A. eilatiensis isolate #1) to 1,461 nts. (A. eilatiensis isolate #2). The latter sequences are identical, the difference in length being due to three insertions. Amphidinium eilatiensis is genetically more closely related to A. carterae than to A. klebsii, with respectively 2. 36% and 6. 93% of sequence divergence. [source]

Zebrafish as a model for developmental neurotoxicity testing,,

BIRTH DEFECTS RESEARCH, Issue 7 2006
Christopher Ton
Abstract BACKGROUND: To establish zebrafish as a developmental toxicity model, we used 7 well-characterized compounds to examine several parameters of neurotoxicity during development. METHODS: Embryos were exposed by semistatic immersion from 6 hrs postfertilization (hpf). Teratogenicity was assessed using a modified method previously developed by Phylonix. Dying cells in the brain were assessed by acridine orange staining (these cells are likely to be apoptotic). Motor neurons were assessed by antiacetylated tubulin staining and catecholaminergic neurons were visualized by antityrosine hydroxylase staining. RESULTS: Atrazine, dichlorodiphenyltrichloroethane (DDT), and 2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD) were primarily teratogenic and not specifically neurotoxic. 2,4-dichlorophenoxyacetic acid (2,4-D), dieldrin, and nonylphenol showed specific neurotoxicity; dieldrin and nonylphenol were specifically toxic to catecholaminergic neurons. Malathion, although not teratogenic, showed some nonspecific toxicity. CONCLUSIONS: Teratogenicity measured in 96-hpf zebrafish is predictive of mammalian teratogenicity and is useful in determining whether a compound causes specific neurotoxicity or general developmental toxicity. Induction of apoptosis or necrosis is an indicator of neurotoxicity. An effect on motor neurons in the caudal third of the embryo correlates with expected defects in motility. Overall, our results showed a strong correlation with mammalian data and suggest that zebrafish is a predictive animal model for neurotoxicity screening. Birth Defects Research (Part A) 76:553,567, 2006. Published 2006 Wiley-Liss, Inc. [source]