bluuebunny/crossref_metadata_2025 huggingface dataset:
LLC‐PK1 cysts: A model for the study of epithelial polarity
Authors: Wohlwend Annelise , Montesano Roberto , Vassalli Jean‐Dominique , Orci Lelio
Published: May 2005

In the present work, we have taken advantage of the properties of two recently isolated clonal subpopulations of the pig kidney‐derived LLC‐PK1 cell line to study aspects of the establishment of epithelial polarity. When grown in suspension, LLC‐PK1/D + Sc cells reaggregated within a few hours and, during the following days of culture, formed free‐floating, hollow spheres or cysts, lined by a monolayer of polarized cells. In contrast, LLC‐PK1/D ‐ cells were unable to develop such polarized structures even upon prolonged culture in suspension. The polarity of the LLC‐PK1/D + Sc cells lining the cysts was inverted compared to that in intact renal tubules, the microvilli‐rich “apical” pole being oriented toward the external medium. However, upon embedding these preformed cysts in collagen gels, a reversal of polarity was observed within hours, the microvilli‐rich pole now facing the cyst cavity. Thus, in the same clonally derived cell population, cell‐to‐cell contact and interaction with the extracellular matrix differentially affect the orientation of cellular polarity. The LLC‐PK1/D + Sc cysts provide a suitable in vitro model system for further study of the sequential events by which extracellular matrix components induce an appropriately oriented polarization. In addition, the comparison between LLC‐PK1/D + Sc and D ‐ cells, which differ in their ability to polarize in response to cell‐to‐cell contact, should help define some of the cellular determinants involved in epithelial organization.
Separation of murine megakaryocytes and their progenitors on continuous gradients of percoll
Authors: Ishibashi Toshiyuki , Burstein Samuel A.
Published: May 2005

Murine bone marrow was separated on continuous Percoll density gradients to analyze the distribution of cells of the megakaryocyte lineage. Eighty‐seven percent of the recovered megakaryocytes were found in fractions of density less than 1.058 g/cm3, with 63% of these cells found between 1.020 and 1.036 g/cm3. When megakaryocytes were classified according to size, 92% of the large ( ≥ 18 μm) acetylcholinesterase (AchE) positive cells were found in the least dense fractions (1.016–1.039 g/cm3), whereas 86% of the small (⩽ 10.6 μm) AchE positive cells were found in fractions of higher density (1.039‐‐1.078 g/cm3). The distribution of enzymatic AchE activity of the separated fractions corresponded to the location of the histochemically positive cells. When ploidy measurements were made of various fractions, most of the high ploidy (32N and 64N) cells were found at low density (1.028–1.036 g/cm3), whereas no cells greater than 4N were found at density > 1.071 g/cm3. Thus, large AchE positive cells and the cells of highest ploidy were found at lower densities of Percoll, while small AchE positive cells and cells of low ploidy were found at higher densities. An exception to this inverse relationship was found in fractions of lowest density ( > 1.030 g/cm3) where an anomalous distribution of size and ploidy was found. The majority of megakaryocytic colony‐forming cells (CFU‐MK) were found at high density, as were the granulocyte‐macro‐phage colony‐forming cells (CFU‐GM; ∼ 1.074 g/cm3). The density distribution of the incorporation of tritiated thymidine into liquid marrow cultures was concordant with the high density distribution of colony‐forming cells. The data show that megakaryocytic maturity and Percoll density varies inversely and that fractionation of marrow on continuous Percoll gradients may be a useful method for the separation and/or enrichment of megakaryocytes at different stages of differentiation.
Activation of ornithine decarboxylase in monolayer cells treated with trypsin
Authors: Gerner Eugene W. , Glass James R. , Fuller David J. M.
Published: May 2005

When monolayer Chinese hamster cells are treated with trypsin for short periods of time, ornithine decarboxylase (ODCase) activity increase two‐ to fourfold. This increase can be blocked by aprotinin, a protease inhibitor, and is not observed when cultures are dislodged from substrate mechanically prior to contact with exogenous trypsin. The trypsin‐induced increase in ornithine decarboxylase activity is not due to degradation of enzyme or inhibitor molecules or to new enzyme synthesis. Immunoprecipitable protein, radiolabeled with [3H]α‐difluoromethylornithine in vitro, is the same molecular weight in cells harvested with or without trypsin. Protein‐bound levels of this specific enzyme‐activated irreversible inhibitor of ornithine decarboxylase are unchanged by trypsin treatments that increase enzyme activity. Trypsin treatment of rat embryonic fibroblasts, transformed by a temperature‐sensitive mutant of Rous sarcoma virus, increases ODCase activity in cells growing at the nonpermissive, but not at the permissive, temperature for the transformed phenotype. These results suggest that ornithine decarboxylase can be activated by exogenous trypsin treatment in a manner that is dependent on cell adhesion properties, which are modified in transformed cells.
On the role of 17 alpha‐estradiol and 17 beta‐estradiol in the proliferation of MCF7 and T47D‐A11 human breast tumor cells
Authors: Papendorp John T. , Schatz Robert W. , Soto Ana M. , Sonnenschein Carlos
Published: May 2005

A comparative study of the proliferative effect of 17 beta‐estradiol and 17 alpha‐estradiol on human estrogen‐sensitive cell lines was performed. When using charcoal‐dextran stripped human female sera‐supplemented media the administration of the hormones, 17 alpha‐estradiol at 3 × 10−10M, and 17 beta‐estradiol at 3 × 10−11M, resulted in a ten‐fold increase in cell yield when compared with non‐estrogen supplemented controls after cells were grown for periods between 10 to 14 days. No significant metabolization of 17 alpha‐estradiol into 17 beta‐estradiol occurred as measured by the E2 levels in the supernatants of the cell culture flasks. Increased concentrations of 17 beta‐estradiol and 17 alpha‐estradiol added to the media bathing C7MCF7‐173 cells resulted in a triggering of a partially successful shut‐off effect; this phenomenon was not observed with T47D‐All cells. These results are compatible with predictions stemming from the indirect and direct negative working hypothesis for the regulation of cell proliferation.
Detector Systems in Capillary Gas Chromatography
Authors: Noij Th. , Rijks J. A. , van Es A. J. , Cramers C. A.
Published: May 2005

Expressions for the minimum detectable amount Qo and the minimum analyte concentration Co as functions of the chromatographic parameters are derived for both mass and concentration sensitive detectors. The effects of pressure drop, column inner diameter, and film thickness are given.

The minimum analyte concentration for mass flow sensitive detectors, Com, can be reduced considerably by selecting the carrier gas velocity well above its optimum value (related to Hmin), however, at the cost of long columns and long analysis times. For Qo the improvements can be neglected, and so the analysis can best be performed at uopt.

When the flow rate in the detector, Fd, is equal to the column flow rate Fc, the maximum permissible detector volume of concentration sensitive detectors is proportional to dc2 up to dc3, and so narrow bore columns require detectors of extremely small volume. Make‐up gas has to be added when the actual volume is too large, thus worsening the detectability. Another approach, vacuum operation of the detector cell, appears to be very attractive. On the other hand, when wide bore columns are used in combination with small volume concentration sensitive detectors, very small values of Qoc and Coc are obtainable when the abundant carrier gas can be removed before entering the detector cell.

Digital noise filtering can further reduce the obtainable Qo and Co values, especially for broad peaks and thus for wide bore columns.
Supercritical fluid chromatography of alkylene oxide‐fatty alcohol condensates: Their quantitation in water samples
Authors: Onuska F. I. , Terry K. A.
Published: May 2005

A method is described for the quantitative determination of linear alkylene oxide‐fatty alcohol condensates, nonionic surface active agents in water. Surface active agent is extracted from water samples with benzene. Surfactant is further extracted by salting out into chloroform. Capillary, supercritical fluid chromatography allows the separation and quantitative determination of oligometric constituents using carbon dioxide as a supercritical fluid. In this case, a fingerprint of the surfactant is obtained. Analysis time, however, is approximately 60 minutes. In the second case, the ether groups of ethylene oxide fatty alcohol condensates are cleaved by reaction with 50 percent hydrobromic acid in glacial acetic acid in sealed ampoules. The resulting alkyl bromides are extracted with carbon disulfide and chromatographed by both the supercritical fluid, capillary column chromatography (SFC) and high resolution open tubular column gas chromatography (OTC – HRGC). Results are in good agreement between these two techniques.
Siloxane/silarylene copolymers as stationary phases for capillary gas chromatography. Part II: Phenylsubstituted polymers
Authors: Bemgård A. , Blomberg L. , Lymann M. , Claude S. , Tabacchi R.
Published: May 2005

A commercially available silanol terminated silicone stationary phase, OV‐61‐OH (33% phenyl), and two phenyl‐substituted siloxane/silarylene copolymers, Sila 3 (27% phenyl) and 4 (35% phenyl), have been evaluated for use as stationary phases in fused silica capillary columns for gas chromatography.

Ulterations in column adsorptive activity, separation efficiency, stationary phase film thickness and selectivity after column conditioning for 50 h at 370°C have been studied. A high thermal stability was experienced with the stationary phases tested here. For OV‐61‐OH, the best thermal stability was obtained when coated on untreated fused silica, which illustrates the importance of grafting reactions here. The heat treatment resulted in some deactivation of adsorptive sites in the column. A higher degree of column deactivation was achieved when surface silylation was performed prior to coating. High thermal stability was achieved with Sila 3 when coated on such surfaces. Sila 3 would thus be preferred in cases when high thermal stability in combination with high dsorptive inertness is desired.

Sila 4 showed low column bleeding at 370 °C, but prolonged heating at this temperature resulted in the broadening of n‐alkane peaks when eluted at 90 °C. This indicates that excessive crosslinking has taken place during the heat treatment and the minimum allowable column operation temperature is thereby increased to ca. 120 °C. The separation of aza‐arenes and of triglycerides are
shown as applications.
Ultrastructural and histochemical features of the thymus glands of the adult lungless salamander, Plethodon glutinosus (Caudata: Plethodontidae)
Authors: Curtis Sherill K. , Cowden Ronald R. , Nagel Jerry W.
Published: May 2005

The thymus glands of adult slimy salamanders (Plethodon glutinosus) were examined by light and electron microscopy with the objective of describing the populations of epithelial cells believed to be secretory. The results of various histochemical procedures designed to demonstrate nucleic acids, proteins, lipids, and mucosubstances were evaluated by light microscopy. Each thymus is incompletely subdivided into a variable number of interconnected lobules by trabeculae extending inward from a thin capsule composed of connective tissues. The thymic parenchyma lacks distinct cortical and medullary regions, although developing lymphocytes and plasma cells tend to accumulate in larger numbers in the outermost portions of the gland. Basophils are found regularly in the capsule and trabeculae, but only very rarely within the thymic parenchyma. The epithelial cells of the thymus can be classified into five categories: epithelial reticular cells; three varieties of granulated cells (types I, II, and III), and myoid cells. Epithelial reticular cells form a three‐dimensional network which extends throughout all portions of the thymus. Type I and type II granulated cells can be distinguished from one another by various morphological criteria at the ultrastructural level, but only small differences in the composition of their inclusions can be demonstrated histochemically. Both types of granules are composed principally of a proteinaceous material containing an abundance of primary amino and guanidyl groups. In addition, most type I inclusions possess a lipid component that cannot be demonstrated in type II granules. Type III granulated cells possess very small cytoplasmic inclusions resembling those of gastroenteric endocrine cells. Myoid cells contain concentrically arranged myofibrils composed of sarcomeres. In favorably oriented material, small cysts can be identified whose walls are composed of mixtures of type I cells, type II cells, and epithelial reticular cells. Groups of degenerating epithelial cells form lamellated structures corresponding to Hassall's (thymic) corpuscles.
Fine structural studies of the nervous system and the apical organ in the planula larva of the sea anemone Anthopleura elegantissima
Authors: Chia Fu‐Shiang , Koss Ron
Published: May 2005

The nervous system of the planula larva of Anthopleura elegantissima consists of an apical organ, one type of endodermal receptor cell, two types of ectodermal receptor cells, central neurons and nerve plexus. Both interneural and neuromuscular synapses are found in the nerve plexus.

The apical organ is a collection of about 100 long, columnar cells each bearing a long cilium and a collar of about 10 microvilli. The cilia of the apical organ are twisted together to form an apical tuft. The ciliary rootlets of the apical organ cells are extremely long, reaching to the basal processes of the cells adjacent to the mesoglea.

All three types of sensory cells are tall and slender in profile and are identified by the presence of one or more of the following features: microtubules, small vesicles, membrane‐bound granules and synapses. The interneurons are bipolar cells with somas restricted to the aboral end, adjacent to the apical organ. All synapses observed are polarized or asymmetrical.

A diagram including all the elements of the nervous system is presented and the possible functions of the nervous system are discussed in relation to larval behavior.
A morphometric study of the cochlea of the little brown bat (Myotis lucifugus)
Authors: Ramprashad Fred , Landolt Jack P. , Money Kenneth E. , Clark Diana , Laufer Jerry
Published: May 2005

A detailed morphometric study of the basilar membrane was made from serial sections and graphic reconstructions of the cochlea of three little brown bats. Four distinct morphometric changes were observed within the basilar membrane. First, between 0‐1.4 mm from the basal end of the cochlea, there is a rapid increase in width and cross‐sectional area of the basilar membrane. Secondly, between 1.4‐2.5 mm, there is little change in width of the basilar membrane (its cross‐sectional area is at its greatest in this region). Thirdly, between 2.7‐3.1 mm, there is a sudden decrease in cross‐sectional area concomitant with an increase in the width of the basilar membrane. Finally, between 3.1 mm and the apex, there is a gradual decrease in cross‐sectional area concomitant with an increase in the width of the basilar membrane. The magnitudes of the cross‐sectional areas of the scalae media and vestibuli decrease from base to apex, but this is not true for the scala tympani. The cross‐sectional area of the scala tympani appears to decrease from the base to 0.7 mm, then it increases up to 1.4 mm, and then it decreases to the apex. These morphometric changes in the basilar membrane of the little brown bat are compared to those in other echolocating and non‐echolocating mammals. The significance of these changes is discussed in relation to the range of hearing in the little brown bat.
Normal distribution of alpha‐1‐adrenoceptors in the rat spinal cord and its modification after noradrenergic denervation: A quantitative autoradiographic study
Authors: Roudet C. , Savasta M. , Feuerstein C.
Published: May 2005

The distribution of alpha 1 (α1)‐adrenoceptors along the different segments of the spinal cord (cervical, thoracic, lumbar, and sacral) of normal rats has been studied by quantitative autoradiography using the specific α‐antagonist [3H]Prazosin as a ligand. In addition, the influence of noradrenergic (NA) denervation [obtained either by complete transection of the spinal cord at vertebrae level T8‐T9 or by selective lesion of NA spinal cord system carried out by intracisternal injection of 6‐hydroxydopamine (6‐OHDA)] on eventual variations of α1‐adrenoceptor density at spinal cord target cells was studied in parallel.

In control rats, the quantitative analysis of α1‐adrenoceptor densities revealed a widespread distribution of these receptors along all segments of the spinal cord with a similar pattern in the various subregions of gray matter studied. This distribution of α1‐adrenoceptors was quite well correlated with the distribution of NA terminals, when referring to previous descriptions by immunohistochemistry.

After 6‐OHDA lesion, as well as caudally to the transection, a significant increase of α1‐adrenoceptor densities was observed in all spinal subregions thus evidencing supersensitivity.

These results suggest that NA may act in the spinal cord, at least partly, via α‐adrenoceptors and that the expression of these receptors could be influenced by NA dysfunction, as demonstrated here through the effects observed in lesioned animals. © 1993 Wiley‐Liss, Inc.
Early dendrite development in spinal cord cell cultures: A quantitative study
Authors: Neale Elaine A. , Bowers L. M. , Smith T. G.
Published: May 2005

Neurons in dissociated cell culture provide a favorable system for the quantitative analysis of structural changes and the examination of structure‐function relationships during development. Fragment C of tetanus toxin was used to label neurons in murine spinal cord cell cultures and dendrite outgrowth was monitored by a number of measures. The dissociated neurons increased in morphologic complexity from approximate spheres to highly branched structures during the first week in culture. Much of the structural complexity of the dendrite arbor, as quantified by fractal dimension, was established within 48 hr after plating, i.e., prior to the development of interneuronal contacts. During the first few days in culture, dendrite branching complexity increased more rapidly than dendrite size, whereas after 4 days, fractal dimension remained relatively constant while dendrites continued to grow. Fractal analysis has provided data which suggest that the early development of dendrite branching complexity is determined intrinsically. Fractal dimension, as an effective index of morphologic complexity, should be a useful tool for the further study of extrinsic signals which might modify the generation or stabilization of dendrite form. © 1993 Wiley‐Liss, Inc.
Versican, a hyaluronate‐binding proteoglycan of embryonal precartilaginous mesenchyma, is mainly expressed postnatally in rat brain
Authors: Bignami A. , Perides G. , Rahemtulla F.
Published: May 2005

The localization of versican, a large hyaluronatebinding fibroblast proteoglycan, was studies in rat prenatal and postnatal development. In adult rat white matter and cerebellum, the distribution of versican was identical to that previously reported for brain‐specific glial hyaluronate‐binding protein (GHAP). Versican was also found in gray matter where it formed characteristic coats around large neurons. It was also found in peripheral tissues, namely, kidney medulla, myotendinous junctions, and endoneurial and endomysial sheaths. In rat embryo the most notable finding was the presence of large amounts of versican immunoreactive material in precartilaginous mesenchyma. In embryonal CNS, versican was mainly confined to the marginal zone on the surface of the cerebral hemispheres. Versican expression mainly occurred postnatally in brain and spinal cord. In spinal cord white matter, versican immunoreactivity was already present in 3‐day‐old rats and preceded the appearance of GHAP, which was first detected on day 13 after the onset of myelination. Versican expression was markedly delayed in gray matter. The characteristic perineuronal coats were first observed on day 21 in the cerebral cortex. It is concluded that, with the exception of hyaluronate, brain extracellular matrix (ECM) is mainly produced postnatally and that the ECM protein produced by brain cells, most likely astrocytes, is similar to that produced by precartilaginous mesenchyma. © 1993 Wiley‐Liss, Inc.
Transient reversion of O4+ Galc− oligodendrocyte progenitor development in response to the phorbol ester TPA
Authors: Avossa D. , Pfeiffer S. E.
Published: May 2005

The physiological importance of protein kinase C during oligodendrocyte progenitor maturation was investigated by analyzing the effects of the protein kinase C activator phorbol 12‐myristate 13‐acetate (TPA) on the morphology, proliferation, and differentiation of oligodendrocytes at sequential stages of development. Monoclonal antibodies A2B5 and O4 were used to identify the A2B5+ O4− and the A2B5+ O4+ galactocerebroside− progenitor stages. Anti‐galactocerebroside and anti‐myelin basic protein were used to identify mature, post‐mitotic oligodendrocytes. Proliferation was measured by bromodeoxyuridine incorporation. Within 24 hr after addition, TPA induced a down‐regulation of the O4 antigen in OL progenitors, and an increase of expression of the intermediate filament protein vimentin, leading to a phenotypic reversion from the vimentin− A2B5+ O4+ phenotype to the less mature vimentin+ A2B5+ O4− stage. Concomitantly, TPA induced an increase in the number of bromodeoxyuridine‐labeled oligodendrocyte progenitors and extensive process elongation. The response of O4+ progenitors was transient. Even with continued exposure to TPA, by 4 days after TPA addition the reverted cells ceased proliferation, reacquired O4 immunoreactivity, became vimentin‐negative, and began to express galactocerebroside and myelin basic protein, and to display the complex, highly branched morphology characteristic of terminally differentiated oligodendrocytes. These results indicate that modulation of protein kinase C activity by TPA induces a transient reversion of O4+ progenitors to less mature O4− cells, causing a transient inhibition of terminal differentiation. The relationship of these data to similar responses of the OL lineage to specific growth factors and implications for remyelination after pathologic injury are discussed. © 1993 Wiley‐Liss, Inc.
Expression of the class III β‐tubulin gene during axonal regeneration of rat dorsal root ganglion neurons
Authors: Moskowitz P. F. , Smith R. , Pickett J. , Frankfurter A. , Oblinger Monica M.
Published: May 2005

The effect of peripheral axotomy on the expression of the class III β‐tubulin gene in adult dorsal root ganglion (DRG) neurons was examined. Of the 5 isotypic classes of β‐tubulin expressed in the mammalian nervous system, only the class III β‐tubulin is neuron specific. While information about the expression of several of the tubulin genes during neuronal development and regeneration has become available recently, very little is known about the expression of βIII‐tubulin during axonal regeneration. To explore this issue, we examined axotomy‐induced changes in βIII‐tubulin mRNA levels in adult rat lumbar dorsal root ganglion (DRG) neurons at different times (1–28 days) after unilateral sciatic nerve crush using northern blotting of total RNA and quantitative in situ hybridization. These studies showed an initial decrease in βIII‐tubulin mRNA levels in axotomized DRG neurons as compared to contralateral controls at 1 day after injury followed by robust increases in βIII‐tubulin mRNA levels relative to contralateral controls from 1 to 4 weeks after injury. We postulate that βIII‐tubulin may play an essential role in axonal growth because of its unique neuron‐specific pattern of expression and its substantial increase in neurons that have been stimulated to regrow their axons. © 1993 Wiley‐Liss, Inc.
Use of nano‐liquid chromatography for the analysis of glycyrrhizin and glycyrrhetic acid in licorice roots and candies
Authors: Fanali Salvatore , Aturki Zeineb , D'Orazio Giovanni , Raggi Maria Augusta , Quaglia Maria Giovanna , Sabbioni Cesare , Rocco Anna
Published: May 2005

Glycyrrhizin (G) and glycyrrhetic acid (GA) were separated by using nano‐liquid chromatography (nano‐LC) in a fused silica capillary packed with RP18 stationary phase (75 μm ID, effective length 33 cm, packed 23 cm) eluting at 300 nL/min in a gradient mode. The mobile phase was a mixture of water‐MeOH‐MeCN‐acetic acid (29 : 35 : 35 : 1, v/v/v/v) that was delivered for one minute and after this was modified by reducing the water content (14 : 42.5 : 42.5 : 1, v/v/v/v). The intra‐day and inter‐day relative standard deviations (of retention time and peak area) were satisfactory (lower than 2.9 and 4%, respectively). The linearity of the nano‐LC method was assessed in the range 0.62–5.00 μg/mL and 80–200 μg/mL for GA and G, with R 2 = 0.996 and 0.995, respectively. The licorice was extracted with a mixture of ethanol‐water, diluted with the mobile phase, and injected for the analysis.
Comparison of microemulsion electrokinetic chromatography and micellar electrokinetic chromatography methods for the analysis of phenolic compounds
Authors: Huang Hsi‐Ya , Lien Wei‐Chih , Chiu Chen‐Wen
Published: May 2005

In this study, microemulsion electrokinetic chromatography (MEEKC) and micellar electrokinetic chromatography (MEKC) were compared for their abilities to separate and detect thirteen phenolic compounds (syringic acid, p‐coumaric acid, vanillic acid, caffeic acid, gallic acid, 3,4‐dihydroxybenzoic acid, 4‐hydroxybenzoic acid, (+)‐catechin, (–)‐epigallocatechin, (–)‐epicatechin gallate, (–)‐epigallocatechin gallate, (–)‐epicatechin, and (–)‐gallocatechin), and two other ingredients (caffeine and theophylline) in teas and grapes. Separation of phenolic compounds was improved by changing the SDS concentration for MEEKC, but the SDS concentration rarely affected the resolution for MEKC. Organic modifier (acetonitrile or methanol) was found to markedly influence the resolution and selectivity for both MEEKC and MEKC systems. In addition, a higher voltage and a higher column temperature improved the separation efficiency without any noticeable reduction in resolution for MEEKC whereas they caused a poor resolution for the MEKC system. Although separations with baseline resolution were achieved by the optimized MEEKC and MEKC methods, the separation selectivity resulting from the proposed MEEKC method was completely different from that of MEKC.
Co‐electroosmotic capillary electrophoresis determination of phenolic acids in commercial olive oil
Authors: Carrasco Pancorbo Alegría , Segura Carretero Antonio , Fernández Gutiérrez Alberto
Published: May 2005

Fourteen phenolic acids have been selectively determined in olive‐oil samples using the co‐electrosmotic capillary electrophoresis mode with UV detection after the LLE extraction system. A polycationic surfactant (hexadimetrine bromide, HDB), which dynamically coats the inner surface of the capillary and causes a fast anodic electroosmotic flow, was added to the electrolyte. The main factors affecting co‐electroosmotic flow (EOF) such as type of modifier, concentration, and influence of organic solvents have been studied. Other parameters such as pH, type, and concentration of buffer, applied voltage, and injection time were also optimised using hydrodynamic injection for 8 s and UV detection at 210 nm. The composition optimum of the running buffer used was a 20% 2‐propanol, 0.001% HDB, and 50 mM sodium borate at a pH value of 9.6. The method has been applied to determination and quantification of fourteen phenolic acids at ppb levels in olive oil samples after a liquid‐liquid extraction.
Identification of character‐impact odorants in coriander and wild coriander leaves using gas chromatography‐olfactometry (GCO) and comprehensive two‐dimensional gas chromatography–time‐of‐flight mass spectrometry (GC×GC–TOFMS)
Authors: Eyres Graham , Dufour Jean‐Pierre , Hallifax Gabrielle , Sotheeswaran Subramaniam , Marriott Philip J.
Published: May 2005

The essential oil of coriander leaves (Coriandrum sativum) and wild coriander leaves (Eryngium foetidum) grown in Fiji was obtained by steam distillation. The aroma profiles were characterised using gas chromatography‐olfactometry (GCO) and CharmAnalysisTM. The character‐impact odorants were identified using comprehensive two‐dimensional gas chromatography (GC×GC) combined with time‐of‐flight mass spectrometry (TOFMS). During GCO analysis, the co‐elution of E‐2‐alkenals and E‐2‐alken‐1‐ols resulted in the perception of ‘odour‐clusters’. The most important odorants in C. sativum were found to be Z‐2‐decenal, a co‐eluting odour‐cluster (E‐2‐dodecenal, E‐2‐dodecen‐1‐ol, and 1‐dodecanol), β‐ionone, eugenol, and E‐2‐decenal. E‐2‐Decen‐1‐ol was the most abundant compound in C. sativum (26.0% TIC) but only contributed 0.39% of the total odour activity. The most abundant compound in E. foetidum was E‐2‐dodecenal (63.5% TIC), which also contributed the most odour activity (52.9%). Other important odorants were either eugenol or a trimethylbenzaldehyde isomer, β‐ionone, Z‐4‐dodecenal, dodecanal, and E‐2‐tetradecenal. GC×GC–TOFMS allowed the identification of 42 and 20 compounds not previously reported in the literature for C. sativum and E. foetidum, respectively. In particular, β‐ionone was determined to be an important odorant in both samples but could not be identified with GC–qMS.
Development of a method for quantitative analysis of the major whey proteins by capillary electrophoresis with on‐capillary derivatization and laser‐induced fluorescence detection
Authors: Veledo María Teresa , de Frutos Mercedes , Diez‐Masa José Carlos
Published: May 2005

The main whey proteins have been derivatized on‐capillary with 3‐(2‐furoyl)quinoline‐2‐carboxaldehyde (FQ) and analyzed using a laboratory‐made capillary electrophoresis apparatus provided with a laser‐induced fluorescence detector. Several parameters controlling on‐capillary derivatization of proteins, including pH, mixing time, reaction time, concentration of the reagents (potassium cyanide and FQ), and reaction temperature, were optimized. Coefficient variations were lower than 1% for migration time and 7% for peak height. Assay detection limits for the different proteins were in the range 5 nM to 10 nM. The method developed was applied to the separation of the major whey proteins in a laboratory‐made cheese whey and in an infant food formulated with milk. In addition, the β‐LG content of these samples was quantitated. The results showed good agreement with those given by an RP‐HPLC method and with those reported in the literature.
Optimization of a multi‐residue screening method for the determination of 85 pesticides in selected food matrices by stir bar sorptive extraction and thermal desorption GC‐MS
Authors: Ochiai Nobuo , Sasamoto Kikuo , Kanda Hirooki , Yamagami Takashi , David Frank , Tienpont Bart , Sandra Pat
Published: May 2005

A multi‐residue method to determine 85 pesticides, including organochlorine pesticides, carbamates, organophosphorus pesticides, and pyrethroids, in vegetables, fruit, and green tea, has been developed. The method is based on stir bar sorptive extraction (SBSE) coupled to thermal desorption (TD) and retention time locked (RTL) GC‐MS operating in the scan mode. Samples are extracted with methanol and diluted with water prior to SBSE. Dilution of the methanol extract before SBSE was optimized to obtain high sensitivity and to minimize adsorption onto the glass wall of the extraction vessel as well as to minimize sample matrix effects (particularly for the pesticides with high log Ko/w values). The optimized method consists of a dual SBSE extraction performed simultaneously on respectively a twofold and a fivefold diluted methanol extract. After extraction, the two stir bars are placed in a single glass thermal desorption liner and are simultaneously desorbed. The method showed good linearity (r 2 > 0.9900) and high sensitivity (limit of detection: < 5 μg kg–1) for most of the target pesticides. The method was applied to the determination of pesticides at low μg kg–1 in tomato, cucumber, green soybeans, spinach, grapes, and green tea.
Recent advances in the isolation and structural studies of biomacromolecules using microcolumn techniques
Authors: Novotny Milos
Published: May 2005

Microcolumn liquid chromatography and capillary electrophoresis facilitate isolation of biological macromolecules at subnanogram levels. In order to characterize structurally such small amounts of labile materials, it is essential to develop new nanoscale sample treatment approaches and highly sensitive analytical techniques for the determination of biomolecular fragments. Progress in this area is summarized, using selected examples of the amino acid, peptide, and oligonucleotide separations.
Flow rate control in pressure‐programmed capillary supercritical fluid chromatography
Authors: Janssen Hans‐Gerd , Rijks Jacques A. , Cramers Carl A.
Published: May 2005

A versatile and simple system is described that allows variation of the column flow rate in open‐tubular capillary supercritical fluid chromatography using both on‐column and postcolumn detection. The system is based on column‐effluent splitting in a low‐dead‐volume T piece at the column exit just before detection. The flow is split into two streams. One stream is fed to a flame ionization detector, and the second is used to control the overall mass flow through the column. Flow through linear restrictors is studied as a function of the pressure drop over the restrictor at ambient temperature. We derived a simple relationship from this study that quantifies the flow rate characteristics of the dual‐restrictor system as a function of the column pressure and the restrictor back pressure.

The variable‐flow system was employed to control independently column pressure and mass flow rate in pressure‐programmed analysis. Resolution in flow‐controlled pressure‐programmed elution was shown to be superior to that achieved in fixed‐restrictor systems. Furthermore, the applicability of the system as a convenient means of measuring Van Deemter curves and diffusion coefficients is demonstrated.
Large‐volume sample introduction into narrow‐bore gas chromatography columns using thermal desorption modulation and signal averaging
Authors: Liu Zaiyou , Phillips John B.
Published: May 2005

A small diameter (50 μm) open‐tubular gas chromatographic column can be made to accept relatively large volume samples. A conventional injection port and a short length of a 530‐μm‐diameter column are used to accept and hold the sample while it is fed slowly into the 50‐μm column. An injection of such large volume and slow speed normally is quite incompatible with this small, fast column. An on‐column thermal desorption modulator at the head of the column matches the sample to the column by chopping the injected sample into many fast concentration pulses. Signal averaging of the resulting fast chromatograms gives a total sample chromatogram. The method is adaptable to either gaseous or liquid samples.
Current aspects of stationary phase immobilization in open tubular column chromatography
Authors: Blomberg Lars G.
Published: May 2005

In situ stationary phase immobilization in principle can be attempted in two different ways: using thermal methods or radical‐initiated reactions. Thermal immobilization, in general, is applied for the preparation of columns to be used at ultra‐high temperatures, and radical‐initiated immobilization can be applied in most other cases. For polar, narrow‐bore, and thick‐film columns, low immobilization temperatures are preferred. The reactions involved in the different immobilization methods are described in this review, and the advantages and disadvantages of current immobilization methods are discussed.
A step gradient system for microcolumn liquid chromatography based on a multiple‐loop valve
Authors: Banks J. Fred , Novotny Milos V.
Published: May 2005

A new gradient elution system for microcolumn liquid chromatography is presented and evaluated. A multiple‐loop valve system facilitates a reproducible, stepwise addition of the mobile phase at low‐microliter‐per‐minute flow rates. The system is amenable to automation. Gradient precision has been evaluated under various operational conditions. An optimized system yielded standard deviations in retention times of less than 0.5 on runs over 2 h.
Efficiency of packed microcolumns compared with large‐bore packed columns in size‐exclusion chromatography
Authors: Kennedy Robert T. , Jorgenson James W.
Published: May 2005

Columns with inner diameters of 50 and 28 μm were slurry‐packed with 4–5 μm size‐exclusion chromatography particles (Du Pont GF 250 Zorbax Bioseries) and compared with a commercially prepared 9.4‐mm i.d. column that was packed with the same particles. The columns were compared on the basis of efficiencies, peak shapes, and van Deemter coefficients obtained for three proteins used as test analytes. The microcolumns provided more symmetrical peak shapes and lower plate heights than those provided by the commercial column if the peaks were analyzed using statistical moments. For example, hmin for bovine serum albumin was 5.6 in the commercial column and 2.1 in the microcolumn. This difference is attributed to the quality of the packing process, based on the fact that the van Deemter A term was significantly lower for the microcolumn than for the conventional column. The van Deemter data demonstrate that the A term was the major source of band broadening in the commercial column throughout the range of velocities used, and both the A and C terms were significant for the microcolumn. A 90 cm × 50 μm column was prepared and showed approximately 80% of the expected increase in efficiency.
Capillary zone electrophoresis of dilute samples with isotachophoretic preconcentration
Authors: Dolnik Vladislav , Cobb Kelly A. , Novotny Milos
Published: May 2005

A method for concentrating dilute samples prior to separation by capillary zone electrophoresis (CZE) is described. The principles of isotachophoresis are used to achieve higher local concentrations of the sample solution within a preconcentration capillary that is attached directly to the CZE separation capillary. Through a judicious choice of leading, terminating, and background electrolytes, the isotachophoretic preconcentration step can be performed on‐line with the CZE separation using common CZE instrumentation. The use of isotachophoretic preconcentration allows larger volumes of dilute sample solutions to be analyzed effectively in the zone electrophoretic mode, thereby reducing the stringent CZE requirements of small sample volumes and concentrated sample solutions.
Capillary electrophoresis applied to the analysis of pharmaceutical compounds
Authors: Wainright Ann
Published: May 2005

Separations by capillary zone electrophoresis (CZE) in plain, uncoated fused silica capillaries were compared with those in electroendosmosis‐free coated capillaries. For small ions, exemplified by some anti‐inflammatory drugs, resolution and analysis times were comparable in the two types of capillaries. The advantage of the coated capillary was that it predictably eluted all negative analytes regardless of electrolyte pH. The uncoated capillary, on the other hand, allowed separation of both positive and negative species in one run, provided that the electroendosmotic flow was sufficiently high to elute all negatively charged analytes. Because electrolyte conditions were established that eluted all sample analytes, subsequent analyses were performed in uncoated capillaries.

Antibiotics such as sulfonamides, cephalosporins, and penicillins were separated by zone electrophoresis. Optimal separation conditions were established by varying the pH and ionic strength of the electrolyte. For the separation of structurally similar peptides and barbiturates, micellar electrokinetic capillary chromatography (MECC) was the method of choice because the structural differences conferred differences in hydrophobicity.

The feasibility of using CZE in pharmaceutical analysis was shown in the evaluation of over‐the‐counter pain, cold, and allergy medications. These typically gave relative standard deviations of 1% for retention times and 3% for peak areas.
Effects of buffer composition on electroosmotic flow in capillary electrophoresis
Authors: VanOrman Barbara B. , Liversidge Gary G. , McIntire Gregory L. , Olefirowicz Teresa M. , Ewing Andrew G.
Published: May 2005

Solute migration in capillary electrophoresis is the sum of the molecularly specific electrophoretic mobility and the electric‐field‐induced solvent flow (electroosmosis). This solvent flow is an important component of capillary electrophoresis and has been linked to resolution and automation aspects of this technique. This work demonstrates that equivalent electroosmotic flows can be achieved using different buffer types if the ionic strength is equal in the two systems. The effects of the addition of acetonitrile and several different alcohols on electroosmotic flow are also examined. The data suggest a unique surface effect of alcohols on the observed electroosmotic flow.
Electron spin resonance studies of inorganic radicals
Authors: Symons Martyn C. R.
Published: May 2005

A brief review is given of the ways in which ESR spectroscopy has been used to shed light on the electronic structures of simple inorganic radicals. These include atoms (H·, N, O2·, Ag·); diatomic radicals (·OH, ·NO, O), AB2 species(·CO2−, ·NO2, HĊO, O, etc.), AB3 species (·NH3+, ·CH3, ·BH3−, ·NO, ·SO3−, NO3·, H2ĊN, etc.) and AB4 centres (PO, ·PO, ·PF4, etc.). Matrix effects on these species are described and rationalized, and aspects of reaction mechanisms in which they participate are discussed.
EPR study of iron—nitrosyl clusters in the oxidation of Fe(NO)2(CO)2
Authors: Li Lijuan , Morton John R. , Preston Keith F.
Published: May 2005

The oxidation of Fe(NO)2(CO)2 by tetracyanoethylene (TCNE), by the nitrosonium ion (NO+), or by electrolysis in polar solvents was studied by EPR spectroscopy. A number of long‐lived (τ1/2 of the order of hours) free radicals were detected in the early stages of reaction, all having similar isotropic g‐factors and 14,15N hyperfine interactions. These have been identified as the mononuclear cations, Fe(NO)2(CO)2−nStn+ (St = solvent molecule). They slowly disappear and are replaced by persistent radicals (τ1/2 of the order of days) that show equal isotropic hyperfine interactions with four‐, six‐ or eight‐nitrogen nuclei. Infrared and EPR spectroscopic data suggest that two of these species are trinuclear nitrosyl clusters, Fe3(NO)2n(CO) (n = 3, 4), in which the unpaired spin is localized on one iron nucleus, but which are fluxional on the EPR time‐scale. The third nitrosyl radical with four equivalent NO ligands is tentatively identified as a binuclear intermediate that may be a precursor of the trinuclear clusters.
Review of recent EPR and theoretical studies on the addition of free radicals to C60 and C70
Authors: Morton John R. , Negri Fabrizia , Preston Keith F.
Published: May 2005

EPR spectra of free‐radical adducts of C60 and C70 are described and discussed. In the case of addition to C60 the prototype radical is HC60 or perhaps MuC60. The H/Mu hyperfine anomaly in these radicals is explained. The spectra of alkyl‐C60 and fluoroalkyl‐C60 radicals are also described, including factors determining the equilibrium configuration over the C60 surface of radicals of the general formula XYZCC60. The structure of the higher adducts R3C60 and R5C60 is mentioned. In the case of H addition to C70, four of the five possible isomers of HC70 have been identified, but only one of the 2792 isomers of H3C70 is reported.
Simultaneous ESR measurements of the kinetics of oxygen consumption and spin label reduction by mammalian cells
Authors: Morse Philip D. , Smirnov Alex I.
Published: May 2005

Nitroxide spin labels and probes were applied to measurements of cell redox activities and oxygen concentration by ESR. Current experimental methods often require large numbers of cells and monitoring of only the amplitude of the ESR signal. This can result in experimental artifacts and data misinterpretation. An improved method is described for accurate measurement of nitroxide intensity and linewidth, which in turn provides information about cell redox activities and oxygen concentration. The method is based on fitting of ESR spectra using a fast convolution least‐squares algorithm suitable for inhomogeneously broadened ESR lines. All fitting parameters, including the Lorentzian component of the linewidth and the double integrated intensity, are extracted from the experimental spectra directly. The experiments were carried out at cell concentrations of 5 × 106 cell ml−1 or less to prevent cell crowding and at initial nitroxide concentration of 1 mM or 100 μM to ensure that nitroxide metabolism by the cells was not diffusion limited. Examples include experiments with cultured baby hamster kidney and adenovirus transformed hamster cells using the nitroxide radicals TEMPOL (2,2,6,6‐tetramethylpiperidine‐N‐oxyl‐4‐ol) and 15N‐labeled perdeuteriated TEMPONE (15NPDT) (2,2,6,6‐tetramethylpiperidine‐N‐oxyl‐4‐one). Under these experimental conditions, the rates of nitroxide metabolism derived from changes in nitroxide intensity are independent of oxygen concentration.
Temperature and orientation dependence of electron spin relaxation in molybdenum(V) porphyrins
Authors: Husted Rebecca , Du Jing‐Long , Eaton Gareth R. , Eaton Sandra S.
Published: May 2005

Electron spin lattice relaxation rates were measured by saturation recovery for three oxo(5,10,15,20‐tetratolylporphyrinato)molybdenum(V) complexes, OMo(TTP)X, X=Cl−, OH−, OEt−. For O=Mo(TTP)(OEt) in glassy solution between 15 and 130 K the temperature dependence of 1/T1 is consistent with a two‐photon Raman process. For each of the complexes at 100 K 1/T1 is faster when the magnetic field is in the molecular plane than when it is perpendicular to the molecular plane, which is attributed to orientation dependence of intramolecular vibrations. The orientation‐dependent values of 1/T1 are approximately the same for isotopes with I = 0 or I = 5/2, which indicates that molybdenum nuclear hyperfine interaction is not a major factor in the electron spin‐lattice relaxation rate. Phase memory relaxation rates were measured by electron spin echo. Below about 90 K 1/Tm is weakly temperature dependent and becomes more strongly temperature dependent at higher temperature as 1/T1 approaches 1/Tm and as the host lattice softens. For isotopes with I = 5/2 at 100 K 1/Tm is faster at molecular orientations for which the resonant field is more strongly dependent on small changes in molecular orientation.
Atom positions from hyperfine data for germanium centers in α‐quartz
Authors: Mombourquette M. J. , McEachern R. J. , Weil J. A.
Published: May 2005

Germanium 3+ occurs in α‐quartz substitutionally for silicon 4+, either as complex anions [GeO4]− or these anions charge‐compensated with interstitial alkali cations, i.e. as two primary types of species denoted by [GeO4/M], where M = Li, Na. A brief review of the relevant literature is presented. Using the molecular‐orbital spin population for the unpaired electron in each center, available from 73Ge and 17O hyperfine data, an evaluation of the likely M+ positions within the quartz structure has been performed. In part, the present calculations were done to test the well known McConnell‐Strathdee approach with well defined experimental hyperfine data. A generalized discussion of atom‐position determination by EPR, and problems encountered in the process, is included.